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ETL 97-9 Criteria and Guidance for C

1. 101 of 162 25 November 1997 e Using the layer data from the PPD enter the top of the chart with the thickness of the aggregate surface layer Draw a vertical line Line 1 downward through the aircraft pass levels Also enter the bottom of the chart at the desired gross weight draw a line vertically to the curve depicting the CBR of the layer immediately beneath the surface layer then horizontally to intersect Line 1 This point of intersection defines the allowable number of passes If this number is equal to or exceeds the number of passes computed during the evaluation of the surface layer strength then the thickness of the surface layer is adequate Note This step evaluates the layer immediately beneath the surface layer as well as the thickness of the surface layer C 7 1 2 3 Evaluate remaining subsurface layers Repeat this procedure for each soil layer Enter the top of the chart with the thickness above the layer being evaluated and use the CBR of the layer being evaluated The layer that produces the lowest allowable number of passes is the controlling layer for the evaluation Example Determine the allowable number of passes for a 400 000 Ib C 17 aircraft on the following soil cross section in an A traffic area 8 Aggregate Surface Course CBR 20 8 Subbase Course CBR 15 Subgrade CBR 5 Solution e Step 1 Evaluate Surface Course Strength Enter the nomograph chart at 98 PSI the expected contact tire pres
2. 110 E Subgrade Strength 100 A High CBR gt 13 90 B Medium CBR 9 13 C Low CBR 4 8 80 D Ultra Low lt 4 70 60 ACN PCN 50 40 30 20 10 250 300 350 400 450 500 550 600 Aircraft Gross Weight kips Figure C 12 Semi Prepared ACN Curves for C 17 C 8 4 Similar ACN PCN charts will be developed for other aircraft capable of using semi prepared airfields Figure C 13 depicts ACN PCN curves for the C 130 aircraft and Figure C 14 depicts ACN PCN curves for the C 27 aircraft When analyzing the effect of an aircraft on a specific airfield feature the appropriate ACN must be selected For example if the PCN of a given feature is 50 S B X T to determine the effect of any other aircraft on the same feature the correct ACN for that aircraft must be used the one considering similar pavement type and subgrade strength Atch 1 106 of 162 25 November 1997 Subgrade Strength A High CBR 13 B Medium CBR ns C Low CBR D Ultra Low CBR 1 ACN PCN 60 70 80 90 100 110 120 130 140 150 160 170 180 Aircraft Gross Weight kips Figure C 13 Semi Prepared ACN Curves for C 130 SUBGRADE STRENGTH ALL SUBGRADE CATEGORIES ACN PCN 6182 em Aircraft Gross Weight kips Figure C 14 Semi Prepared ACN Curves for C 27 C 8 5 The ACN PCN system is structured so that a feature with a particular PCN value can sup
3. DCP TEST DATA File Name DCP Project Example DCP Data Plot Date Location Soil Type s SP Poorly Graded Sand Hammer Soil Type W 10 1 Ib Save Data W cH Plot Profile 17 6 Ib CL n Delete Data m 1 Both hammers used 1 All other soils No of Accumulative Type of CBR Blows Penetration Hammer 1 10 100 25 65 90 115 145 170 195 220 250 280 305 335 370 400 430 465 500 530 560 590 620 660 690 725 765 805 850 875 905 935 970 1005 1035 1075 1110 1150 1185 1220 100 200 1L 4 300 16 H 4 400 24 500 DEPTH in DEPTH mm 1 600 32 H J 4 700 36 J 4 800 40 j 900 48 L 1 4000 ROAD PROFILE 100 200 300 e TT oa 400 500 DEPTH in N e m DEPTH mm 600 N oa 1 700 30 4 1 a Ww NN NNWANNNNW WHO K HK NH 800 35 4 900 40 1 1000 Figure C 5 Software Plot of DCP Data Atch 1 90 of 162 25 November 1997 Table C 2 Tabulated Correlation of DCP Index vs CBR DCP Index DCP Index DCP Index mm blow in Blow CBR mm blow in Blow CBR mm blow in Blow CBR lt
4. 20 00 40 00 50 00 60 00 10 00 CBR Figure 4 4 Design Curve for C 17 Operations on AM 2 Mat at 350 000 Pounds 1 00 Atch 1 35 of 162 25 November 1997 0 00 10 00 20 00 30 00 5 000 Aircraft Passes 40 00 inches 50 00 60 00 70 00 Minimum Thickness Required Beneath AM 2 Mat 80 00 1 00 CBR 90 10 00 Figure 4 5 Design Curve for C 17 Operations on AM 2 Mat at 400 000 Pounds 0 00 10 00 20 00 oO c 30 00 9 9 Passes amp 5 40 00 tc 50 00 c x o E 60 00 E E 7000 80 00 1 00 100 00 10 00 Figure 4 6 Design Curve for C 17 Operations on AM 2 Mat at 450 000 Pounds Atch 1 36 of 162 25 November 1997 0 00 10 00 20 00 30 00 Passes Minimum Thickness Required Beneath AM 2 Mat inches A 10 00 CBR 100 00 Figure 4 7 Design Curve for C 17 Operations on AM 2 Mat at 500 000 Pounds 0 00 E 1000 1D z 4 100 20 00 oO o 1 c m 3000 vo 5 000 Aircraft Passes o o 25 40 00 o c c o 9 50 00 c x 60 00 E E
5. 70 00 z 80 00 1 00 10 00 CBR 96 100 00 Figure 4 8 Design Curve for C 17 Operations on AM 2 Mat at 550 000 Pounds Atch 1 37 of 162 25 November 1997 4 10 4 Design for Frost Conditions Typically contingency airfields are not designed for protection against frost action due to their short design life However in some contingency situations designing for frost conditions may be warranted The design for frost conditions utilizes the reduced subgrade strength criteria which assigns a material to a frost group based upon the material s properties Table 4 5 shows the frost group designations for various material types Each material is then assigned a Frost Area Soil Support Index FASSI number based upon its frost group designation The FASSI numbers for each frost group are illustrated in Table 4 6 The material s FASSI number is then used in lieu of the in place subgrade CBR to enter the design curves Therefore to design for frost conditions determine the material s FASSI number then perform a typical contingency design utilizing the FASSI number instead of the in place subgrade CBR However if the FASSI designation is greater than the in place soil s CBR the in place soil s CBR should be used for the final design For a more detailed frost design refer to AFM 88 6 Chapter 4 4 11 Design Examples To illustrate usage of the design criteria outlined above several examples are provided below for designing contingency ai
6. SC and SP SC Gravelly soils GW GM GP GM GW GC and GP GC a ed soils GM GC GM GC b Sands SM SC SW SM SP SM SW SC SP SC and SM SC a Gravelly soils GM GC GM GC b Sands not very fine silty SM SC SM SC sands Clays PI 12 Silts Very fine sands Clays PI 12 Varved clays or fine CL or CH layered with ML grained banded MH SM SC SM SC or sediments ML CL e void ratio NFS indicates non frost susceptible material C a b C d To design for the effects of frost Frost Area Soil Support Indexes FASSIs are used in lieu of CBRs Table 4 6 below lists these indexes for the different frost groups in Table 4 5 The design of contingency airfields for frost conditions is addressed later Atch 1 31 of 162 25 November 1997 Table 4 6 Frost Area Soil Support Indexes FASSIs Frost Area Soil Support Frost Group of Soils Index NFS In place CBR F1 and 1 NNNM 9 F2 and S2 F3 and F4 4 10 Surface CBR and Thickness Design The criteria presented herein describes the design of unsurfaced aggregate surfaced and AM 2 mat surfaced contingency airfields The first step in all designs is to obtain the site reconnaissance or investigation data to determine existing site conditions Divide the subsurface soil strength data into layers of varying thickness by grouping materials possessing similar CBR values The procedure for determining the soil strength for the various layers is
7. GP GM GW GC and GP GC SW SP SW SM SP SM SW SC and SP SC GW GM GP GM GW GC and GP GC a Gravelly soils GM GC GM GC b Sands SM SC SW SM SP SM SW SC SP SC and SM SC a Gravelly soils GM GC GM GC b Sands not very fine silty SM SC SM SC ands Clays PI gt 12 Silts Very fine sands Clays PI 12 Varved clays or fine CL or CH layered with ML MH ained SM banded sediments SC SM SC or ML CL NOTE e void ratio NFS indicates non frost susceptible material C 4 2 1 Loads Gross weights of anticipated mission aircraft including cargo and fuel Co Sandy soils lt 0 30 o A o Gravelly soils Om C 4 2 2 Traffic Volume The expected number of passes anticipated for each aircraft type For a runway passes are determined by the number of aircraft movements across an imaginary traverse line placed within 500 feet of the end of the runway Simply stated it is one aircraft movement over a given area For taxiways and aprons passes are determined by the number of aircraft cycles across a line on the primary taxiway that connects the runway and parking areas For contingency evaluations if the operational data received specifies the number of required missions for a given aircraft this number should be doubled to determine the number of passes C 4 2 3 Aircraft ground operations such as turn arounds and taxi r
8. The wet shaking test is the only way to distinguish this property A 2 2 3 3 Ribbon Test e Procedure Prepare a soil sample as in the roll or thread test Form a roll of soil about 1 2 to 3 4 inch in diameter and 3 to 5 inches long Lay the roll across the palm of one hand palm up and starting at one end squeeze the roll between the thumb and forefinger over the edge of the hand to form a flat unbroken ribbon about 1 8 to 1 4 inch thick Allow the ribbon as formed to hang free and unsupported Continue squeezing and handling the roll carefully to form the maximum length of ribbon that can be supported only by the cohesive properties of the soil Results Sample holds together for a length of 8 to 10 inches without breaking Highly plastic and highly compressive CH Soil can be ribboned only with difficulty to 3 to 8 inch lengths Low plasticity CL A 2 2 3 4 Wet Shaking Test e Procedure Form a ball of soil about 3 4 inch in diameter moistened with water to just below the sticky limit Smooth the soil pat in the palm of the hand with a knife blade or small spatula shake it horizontally and strike the back of the hand vigorously against the other hand When shaking water comes to the surface of the sample producing a smooth shiny or livery appearance Squeeze the sample between the thumb and forefinger of the other hand The surface water will disappear The surface will become dull and the Atch 1 5
9. a gt trc Lu o tc l t o gt I LL gt tc o SURFACE SUBBASE SUBGRADE FEAT IDENT LGTH WDTH pn DESCRP DESCRP DESCRP ft ft K in K in K in FACILITY Atch 1 159 of 162 25 November 1997 CBR 80 COVERAGES 10 000 p 40 T 30 EPE AAAA s3 77 1 ie 1 000 1 1 1 1 1 1 L 2 1 T 1 1 1 D P e SRS Tire Pressure psi o So r 10 Surface CBR Required for Aircraft Operations on Semi prepared Airfields Thickness inches 40 35 30 25 20 15 10 5 0 Re 5 4 ae 300 350 400 450 500 550 600 650 700 Allowable Gross Weight kips Semi prepared Surface Evaluation Curve C 17 Atch 1 160 of 162 25 November 1997 Contact Pass Coverage Gross Weight Surface ESWL Tire Pressure Ratio Aircraft kips kips psi A Traffic C 17 580 55 2 142 1 37 500 47 5 122 450 42 9 110 425 40 5 104 400 38 1 98 350 33 3 84 ESWLs and Tire Pressures for C 17 Aircraft Note A coverage differs from a pass A pass simply represents an aircraft movement across a given point on
10. difference between these three ways to measure velocity is less than 5 then the Bowmonk speed measurement is accurate Multiple tests may be performed and the average of all the tests for each measurement technique may then be compared This test measures the accuracy of the speedometer as well as the Bowmonk D 3 5 3 Verification of Peak Friction or Mean Friction Measurement For this procedure simply run two or more Bowmonk units if available simultaneously in the desired vehicle this will only work on the HMMWV or truck the cycle and quad do not have enough room Perform at least three skid tests at the target speed for that vehicle and then compare the average results Either peak or average mean friction measurements may be compared If the overall average between units differs by less Atch 1 126 of 162 25 November 1997 than 3 then the units are most likely reading correctly If the averages differ by more than 396 then more tests should be conducted If a large number of tests are conducted and the overall average between units still differ by more than 396 then one or more units may be malfunctioning Check to see if the unit settings are the same and that none of the units is due for its annual calibration D 3 5 4 Verification by Direct Measurement Of Skid Distance This procedure may be used to directly measure the average braking friction of any vehicle used Direct comparison of measured skid distance or this n
11. outlined in AFJPAM 32 8013 and Appendix C of this document The second step in the design of contingency airfields for the C 17 aircraft is to determine the design aircraft loading and the number of aircraft passes required to support mission requirements 4 10 1 Unsurfaced Design This design criteria consists of the determination of a minimum surface CBR value and a minimum thickness of material equal to or greater than the minimum surface CBR over a lower strength material The existing soil conditions must meet both the surface CBR requirement and the thickness requirements To determine if the surface CBR is sufficient to sustain the design traffic enter Figure 4 1 with the required number of aircraft passes Proceed vertically until the pass level intersects the appropriate design gross weight of the aircraft Finally trace a horizontal line from this intersection to the required subgrade CBR value The CBR obtained is the surface soil strength required to support the design aircraft load at the required pass level If the CBR obtained from Figure 4 1 is greater than the in place subgrade CBR determined from the preliminary site investigation the airfield will require structural improvement to support mission requirements If the CBR obtained from Figure 4 1 is equal to or less than the in place subgrade CBR the surface CBR requirement is met If the in place surface CBR is only slightly less than the minimum CBR scarify and compact the in pl
12. see ML below Plastic fines see plastcfines Len below Identification Procedures on Fractions smaller than No 40 sieve Thread or D h Wet Shak None to Noneto slight Quick to slow None Silts amp Clays LL lt 50 ES Medium to high None to very slow MH Slight to medium Slight to medium Silts amp Clays Medium to high None to very slow Slight to medium z Readily identified by color odor spongy feel Highly Organic Soils Pt emery E ee O O Unified Soil Classification System No 200 sieve Coarse grained Soils More than half of material is larger than fraction is smaller than No 4 sieve 2 Gg fe o o c G o o z o o 2 Gg o o o G I G o E gt Fine grained Soils No 200 sieve More than half of material is smaller than Atch 1 152 of 162 25 November 1997 Value as m E GW Exelem Good vory siart Gravels GP codio exconenf Poor to tair very sight Gravelly ga ceodteexcalon _ Fair to good sight to mediu Very eig Sands coos _ stighttomeaiufn Sign GC rartogood poor _ sightiomesisfy sight Sw very sight Sands rartogood worsuitable very siant Sandy om d 1 Poor stigntto nigh very sight Graves u Fairtogooa Not suitabie_ Sihtto high Stigt to mediun ML Fairtopoor Notsutable Very nigh slight to me
13. this goal an adequate number of skid tests should be conducted in several locations on the airfield that when averaged will adequately represent the skid resistance of the runway surface Jaquiny PWA PAS uonoauq 1S9 L Wed PIM pue uOneAINSYUOD B o noo IPMA JO PLS uorpoJiq 19quinw 3S9 T puooes 9 uny umunu Jo IIL oseyd 9 I p uonoeg uonoeg c uonoeg uonoeg d4 9 96 Required Skid Test Locations Atch 1 141 of 162 25 November 1997 Number of Tests Required Preliminary analysis of the research data has shown that the number of tests required for the typical contingency airfield 4000 x90 as an example should be as follows Number of Tests Confidence Level Time to Complete 8 Minimum Required 20 Minutes 16 Standard 35 Minutes 24 or more Desired 50 Minutes or more Target Speed at Braking The absolute best speed for skid testing would be the speed of the aircraft when it touches down approximately 135 mph but this is not safe or practical for ground vehicles on a short dirt landing strip The following target speeds are recommended for operational skid testing 40 mph for the HMMWV 6 Pax quad and cycle Please note that the cycle does not have a speedometer or tachometer so the operator must use their best judgment when using this test vehicle Braking Procedure For the
14. 03 Coarse Silt Fine Silt 1 Hour 0 01 Silt Clay e Since all of the particles of soil larger than the No 200 sieve will have settled to the bottom of the cup or jar 30 seconds after the mixture has been agitated it follows that the particles still remaining in suspension are fines The water containing the suspended fines should be carefully poured into another container 30 seconds after agitation more water added to the cup or jar containing the coarse fraction and the procedure repeated until the water soil mixture becomes clear 30 seconds after mixing The cup or jar will contain the coarse fraction of the soil and the other container will hold the fines The water is then wicked or evaporated off and the relative amounts of fines and sands determined fairly accurately In clay soils the clay particles will often form small lumps flocculate that will not break up in water If after several repetitions of the test substantial amounts of clay are still present in the coarse material the sand will feel slippery Further mixing and grinding with a stick will be necessary to help break up these lumps A 2 2 3 Plasticity Tests Fine grained soil particles those passing the No 200 sieve are generally not classified using gradation criteria but are identified primarily by characteristics related to plasticity In the laboratory Atterberg tests are used to define the liquid and plastic limits of the soil and classify it Expedient field tests
15. 25 November 1997 RCR 20 16 12 Note These runway lengths do not include under overruns Pressure Altitude ft 0 6 000 0 2 000 2 001 5 000 5 001 6 000 0 2 000 2 001 5 000 5 001 6 000 0 3 000 3 001 5 000 5 001 6 000 0 2 000 2 001 4 000 4 001 6 000 Runway Length ft 3 500 3 500 4 000 4 500 4 000 4 500 5 000 5 000 5 500 6 000 6 000 6 500 7 000 E 1 2 Annex A appendix 2 1 Airfield Survey Data should be updated as follows E 1 2 1 RCR Values The following charts procedures related to friction measurement should be included in the checklist 139 of 162 Atch 1 25 November 1997 Mission Select Skid Test Vehicle Equipment Suitability Truck HMMW V Quad Cycle Availability Readiness Checks Enter Header Info MER Detailed Speed s re Deploymen Bowmonk Operations Peak amp Mean Friction Operational Checks Quick Speed Printer Paper Battery Charger Skid Distance Pre Deployment In Field Layout Field Test Locations Skid Locations Required Perform Skid Testing Download Process Skid Data Calculate C 17 RCR Correlate Ground Vehicle Decel to Aircraft RCR Flowchart of the Recommended Friction Procedure Atch 1 140 of 162 25 November 1997 Layout Field Test Locations The goal of the field tests is to accurately characterize the on site friction supply or skid resistance of an unpaved airfield In order to meet
16. 3 0 10 100 12 18 56 57 2 20 3 2 0 11 92 0 50 17 58 3 1 0 12 84 13 16 59 60 3 0 3 80 14 0 55 15 61 62 2 40 2 9 0 13 76 15 0 60 14 63 64 2 50 2 8 0 14 70 16 0 65 13 65 66 2 60 2 7 0 15 65 17 0 70 12 67 68 2 6 0 16 61 18 19 11 69 71 2 80 2 5 4 60 20 21 0 80 10 72 74 2 4 0 17 57 22 23 0 90 9 75 77 3 00 2 3 0 18 53 24 26 1 0 8 78 80 2 2 5 0 19 50 27 29 7 81 83 2 1 0 20 47 30 34 6 84 87 3 40 2 0 21 45 35 38 1 40 5 88 89 3 50 1 9 0 22 43 39 4 8 92 96 1 8 0 23 41 440 4 7 97 101 4 00 1 7 6 40 41 1 60 4 6 102 107 1 6 0 24 39 42 4 4 108 114 1 5 0 25 37 43 4 3 115 121 1 4 7 0 26 35 44 4 2 122 130 5 00 1 3 0 27 34 45 4 1 131 140 1 2 0 28 32 46 1 80 4 141 152 1 1 0 29 31 47 3 9 153 166 6 00 1 8 0 30 30 48 3 8 166 183 7 00 0 9 9 0 35 25 49 50 3 7 184 205 8 00 0 8 0 40 22 51 2 0 3 6 206 233 9 00 0 7 10 11 20 52 3 5 234 271 10 00 0 6 0 45 19 53 54 3 4 272 324 0 5 55 3 3 2324 0 5 Atch 1 91 of 162 25 November 1997 Table C 3 Tabulated Correlation of DCP Index vs CBR CH and CL Type Soils CH CL DCP DCP DCP DCP Index Index Index Index mm Blow in Blow CBR mm Blow in Blow CBR inBlow CBR mmBlow inBlow CBR 10 0 4 35 115 4 5 3 0 19 0 7 9 6 40 1 6 2 2 15 0 6 23 120 4 7 2 9 20 0 8 8 6 41 1 6 2 1 20 0 8 17 125 4 9 2 8 21 0 8 7 8 42 1 7 2 0 25 1 0 14 130 5 1 2 7 22 0 9 7 1 43 1 7 1 9 30 1 2 12 135 5 3 2 6 23 0 9 6 5 44 1 7 1 8 35 1 4 10 140 5 5 2 5 24 0 9 6 0 45 1 8 1 7 40 1 6 8 7 145 5 7 2 4 25 1 0 55 46 1 8 1 6 4
17. 31 47 3 9 153 166 6 00 1 8 0 30 30 48 3 8 166 183 7 00 0 9 9 0 35 25 49 50 3 7 184 205 8 00 0 8 0 40 22 51 2 0 3 6 206 233 9 00 0 7 10 11 20 52 3 5 234 271 10 00 0 6 0 45 19 53 54 3 4 272 324 0 5 55 33 2924 0 5 Tabulated Correlation of DCP Index vs CBR Atch 1 157 of 162 25 November 1997 CH CL DCP DCP DCP DCP Index Index Index Index mm Blow in Blow CBR mm Blow in Blow CBR mm Blow in Blow CBR mm Blow in Blow CBR 10 0 4 35 115 4 5 3 0 19 0 7 96 40 1 6 2 2 15 0 6 23 120 47 29 20 0 8 86 41 1 6 2 1 20 0 8 17 125 49 28 21 0 8 7 8 42 17 2 0 25 1 0 14 130 5 1 12 7 22 0 9 7 1 43 1 7 19 30 1 2 12 135 5 3 26 23 0 9 65 44 1 7 1 8 35 1 4 10 140 5 5 12 5 24 0 9 6 0 45 1 8 1 7 40 16 8 7 145 57 2 4 25 1 0 55 46 1 8 1 6 45 18 7 7 150 5 9 23 26 1 0 5 1 47 19 1 6 50 2 0 7 0 155 6 1 23 27 11 47 48 1 9 1 5 55 2 2 53 160 6 3 2 2 28 1 1 4 4 49 19 1 4 60 24 58 165 65 2 1 29 1 1 4 1 50 2 0 1 4 65 26 54 170 6 7 2 0 30 1 2 3 8 51 2 0 1 3 70 28 50 5175 569 lt 2 0 31 12 3 6 52 2 0 1 3 75 3 0 4 6 32 13 3 4 53 2 1 1 2 80 3 1 4 3 33 13 32 54 2 1 1 2 85 33 4 1 34 14 3 0 55 2 2 1 1 90 3 5 3 9 35 14 28 56 2 2 1 1 95 3 7 37 36 14 27 57 2 2 1 1 100 3 9 35 37 1 5 25 58 2 3 1 0 105 41 3 3 38 15 24 gt 59 gt 2 3 lt 1 0 110 4 3 3 2 39 1 5 972 3 Tabulated Correlation of DCP Index vs CBR CH and CL Type Soils Atch 1 158 of 162 25 November 1997 o a l LL 4 tc t tc us o 4 E t
18. 8 of this document 4 6 Gradation Requirements The recommended gradation requirements and design CBR values for the subbase and select material FM 5 430 00 1 AFPAM 32 8013 Vol Atch 1 25 of 162 25 November 1997 1 are shown in Table 4 1 Select material is used when an additional thickness above the subgrade is required and can be achieved with a more readily available material than the subbase or base material Table 4 1 Recommended Maximum Permissible Value of Gradation and Atterberg Limit Requirements in Subbases and Select Materials Maximum Permissible Value Gradation Requirements passing Atterberg Limits Maximum Design Size in Material CBR Inches No 10 No 200 LL PI Subbase 50 2 50 15 25 5 Subbase 40 2 80 15 25 5 Subbase 30 2 100 15 25 5 Select 20 3 35 12 Material Determination of these values will be made according to ASTM D4318 The recommended gradation requirements for base course materials FM 5 430 00 1 AFPAM 32 8013 Vol I are shown in Table 4 2 The base course should also meet the plastic and liquid limit requirements set for the subbase material as shown in Table 4 1 A material with a liquid limit greater than 25 or a plasticity index greater than 5 should not be used as a base course The strengths in terms of a design CBR that may be expected of the base course material FM 5 430 001 AFPAM 32 8013 Vol 1 if it meets the gradation and compaction requirements Table 4 4 are shown in T
19. THICK in DESCRP CBR THICK in DESCRP CBR THICK DESCRP CBR in Figure C 8 Summary of Physical Property Data Sheet Atch 1 98 of 162 25 November 1997 COVERAGES 4 10 000 i 1 000 1 I 3 1 1 1 Ja 100 1 1 1 21 D e Sore e e j vy 5 10 Tire Pressure psi 1 11 Figure 9 CBR Required for Operation of Aircraft on Semi Prepared Airfields Atch 1 99 of 162 25 November 1997 Thickness inches 40 35 30 25 20 15 10 5 0 300 350 400 450 500 550 600 650 700 Allowable Gross Weight kips Figure C 10 Semi Prepared Surface Evaluation Curve C 17 C 7 1 1 3 Choose the type of evaluation for allowable passes or loads e f evaluating for loads enter the number of design passes e f evaluating for passes the design load is automatically adjusted when the type aircraft is selected but this can be altered For example if the C 17 aircraft is selected the design load of 580 000 Ibs is shown This is the maximum design load of the aircraft If you wanted to determine the allowable passes for a C 17
20. Value B Medium X Medium Evaluation F Flexible C Low Y Low U Using Aircraft S Semi Prepared D Ultralow Z Ultralow Subgrade Flexible Rigid Tire Strength Pavement Pavement Pressure Pressure Code CBR k Code psi A Over 13 Over 400 W No Limit B 8 13 201 400 X 146 217 C 4 8 100 200 Y 74 145 D 4 100 Z 0 73 Example If the reported PCN for a feature is 50 S A X T 50 indicates the PCN number S indicates that it is an semi prepared airfield A indicates a high subgrade strength X indicates that medium tire pressures are allowed and T indicates that a technical evaluation was performed to determine the PCN Each part of the code is important The number 50 cannot be used properly without the letters that follow C 8 3 Once an AGL has been determined for an airfield feature this should be converted to a PCN using the Semi Prepared ACN PCN Curves Figure C 12 For example during the evaluation of an semi prepared airfield with a subgrade strength of 12 CBR it was determined that in order to complete 1 000 passes of the C 17 on the airfield its AGL must be limited to 425 000 pounds To determine the airfield PCN enter the bottom of the chart in Figure C 12 at 425 and extend the line vertically until it intersects the B subgrade strength curve At this point extend the line horizontally to determine the PCN of 50 This would be reported as 50 S B X T Atch 1 105 of 162 25 November 1997
21. at the top with the in place subgrade CBR 12 and draw a vertical line down until it intersects the design gross weight of the C 17 or 447 kips Next draw a horizontal line from this intersection until it intersects the design pass level of 400 passes Finally draw a vertical line from this intersection downward until you intercept the required thickness The design requires 8 inches of 15 CBR material be placed over the in place subgrade in order to support 400 passes of a 447 kip C 17 aircraft 4 11 3 Example 3 Developments have led to the need for a contingency airfield Estimation of the mission suggests that the design pass level should be 1 000 passes of a 447 kip C 17 The only available site has a CBR of 4 for a depth of 12 inches where it increases to an 8 CBR for an additional 24 inches Note The mission requirements include plans for a parallel taxiway and a small apron Thus the number of required passes should remain at 1 000 due to the probability that the aircraft will use the taxiway and apron for all movements other than takeoffs or landings Step 1 The design aircraft has been designated as the C 17 The design gross weight of the C 17 is 447 kips which seems reasonable in regard to mission requirements Step 2 The design aircraft passes stated were 1 000 All pavements are A type traffic areas and will use the same design Step 3 Using Figure 4 1 determine the minimum required subgrade strength to support 1 000 pas
22. bearing capacity of a soil used as a base or subgrade beneath airfield pavements For military pavement applications the California Bearing Ratio CBR value of a soil is used as a measure of soil strength Atch 1 85 of 162 25 November 1997 Laboratory methods of determining CBR values are time consuming and thus impractical for expedient or contingency evaluations Several methods are available to determine CBR values in the field C 3 3 1 Dynamic Cone Penetrometer The DCP is the preferred method of obtaining CBR field data It will penetrate layers having CBR strengths in excess of 100 and will measure soil strengths less than 1 It is a powerful relatively compact sturdy device that produces consistent results Its use will be discussed in detail later in this section Airfield Cone Penetrometer ACP The ACP is a probe type instrument that when pushed down through the soil gives an airfield index Al of soil strength This Al can be correlated to CBR values This instrument is commonly used by USAF SSTs for expedient evaluations because of its portability and simplicity to operate Its range is limited to 0 to 18 CBR and it will not penetrate many crusts thin base course or gravel materials Consistency of test results is also difficult due to variability of soil strengths that impact the rate of penetration Due to this and depth constraints it is not recommended for C 17 evaluations Electronic Cone Penetrometer ECP T
23. es 25052 2 55 Atch 1 70 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Holand pw 6 72 97 Section HO FOO H SO inspector Jack Le run SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY KE GNELZEICELILEEICE SPACI CALCULATIONS Distress Deduct Type Severity Value NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Stabilized Layer Failure Amber Severity Atch 1 71 of 162 25 November 1997 STEP THREE CALCULATING THE RATINGS The distress measurements are used to calculate the Semi Prepared Airfield Condition Index SPACI based on deduct values A deduct value is a number from 0 to 100 with 0 meaning that the distress has no impact on the airfield condition and 100 meaning that the airfield has completely failed Deduct values for runways and taxiways where the aircraft is moving are different than those on aprons and hammerheads where the C 17 may be offloading equipment The deduct value table reflects these differences We will show how to do this calculation by running through an example 1 2 11 12 13 14 15 Fill in the identifying information at the top of the inspection sheet Put a check mar
24. given test location data to that at adjacent test locations C 6 2 Group those containing common characteristics into features C 6 3 Establish the representative profile for each feature In most cases the CBR values selected for a feature should be a low average of those collected from all the test locations within the feature but this is not always true Conditions are seldom uniform and sound engineering judgment should be used C 6 4 Compile the characteristics for each feature into the Summary of PPD This information will be used to determine the allowable gross loads and or allowable passes for the airfield see Figure C 8 C 7 Determine Allowable Gross Loads AGLs Allowable Passes C 7 1 Semi Prepared Airfields Semi prepared airfields may be evaluated for various aircraft using the US Army Waterways Experiment Station developed software program UNSEVA Computer Aided Evaluation of Expedient Airfields or manually using Figure C 9 CBR Nomograph and Semi Prepared Surface Evaluation Curve Figure C 10 C 7 1 1 If using the UNSEVA program C 7 1 1 1 Double click on the icon to bring up the Expedient Airfields screen Inputs from this screen are somewhat self explanatory C 7 1 1 2 Choose the aircraft type from the list Atch 1 97 of 162 25 November 1997 SUMMARY OF PHYSICAL PROPERTY DATA SEMI PREPARED AIRFIELDS FACILITY SURFACE SUBBASE SUBGRADE FEAT IDENT LGTH ft WDTH ft COND
25. grain sizes all intermediate sizes substantially represented Predominantly one size or some intermediate sizes missing Coarse grained Soils More than half of material is larger than More than half of coarse More than half of coarse fraction is smaller than No 4 sieve ac Nonplastic fines or fines with little plasticity see ML below sc Plastic fines see CL below Identification Procedures on Fractions smaller than No 40 sieve Thread or D h Wet Shak ry Strengt et Shake Ribbon None to slight Quick to slow None Medium to high None to very slow Medium Slight to medium Slight Slight to medium Slight to medium Silts amp Clays Medium to high None to very slow Slight to medium Highly Organic Soils Pt Readily identified by color odor spongy feel Table A 1 Unified Soil Classification System Silts amp Clays LL 50 Fine grained Soils No 200 sieve More than half of material is smaller than C SC ML CL OL CH and frequently by fibrous texture Atch 1 44 of 162 25 November 1997 Value as i un i Value as Potential Compressibilit None to N and Gravelly Fair to good Slight to medium Very slight Fair to good Por Slight to mediu very slight Almost none Sands Coarse ined Gravels 1 Poor to None to Fair to good Not suitable very slight Almost none SC Fairtogood _ Not suitable slight to high Sight to mediu ML Fairtopoor Notsutzble very
26. high Sight to mediu cL OL Poor Notsuitabe Medium to nig Medium to nig Poor Notsuitabie very high is CH Poorto very popr_Not suitable Medium OH Poortovery popr Not suitable Medium High ign Organic Soils Pt wot suitable not suitable Sight Very high GM and SM groups are divided into subdivisions d and u for roads and airfields Suffix d is used when 1428 and Pk 6 Suffix u is used when LL gt 28 Subgrade Modulus Drainage Unit Dry Weight Field K Soil Types Symbol Characteristics Lb per Cu Ft CBR Lb per Cu In Gravels 110 190 s000rmore_ and Gravelly Fair to poor 130 145 40 80 300 or more pervious 120 140 20 40 20010900 200 1 300 120 135 impervious 108 130 impervious 105 130 Poor to impervious 105 130 Fartopor 100 125 Poor 20 100 imperious 9 80 impervious 105 Highly organie Soils Pt rartopor GM and SM groups are divided into subdivisions d and u for roads and airfields Suffix d is used when LL lt 28 and PI lt 6 Suffix u is used when LL 28 Fair to good Not suitable Slight to high Slight to mediu Coarse grained Soils 20 40 200 to 300 10 20 200 to 300 200 to 300 100 to 200 100 to 200 as as 50 to 100 Fine grained Soils Table A 2 Charact
27. is the average mean friction in percent g that the test vehicle experienced Record this number Repeat test procedure if performing more than one test Ready vehicle for next skid test if collecting data in lieu of Bowmonk measurements If this was last test print out Bowmonk data and download data if necessary Once the test or tests are completed the average mean friction as measured by the Bowmonk can be compared with the average mean friction derived from table D 4 If these values differ by less than approximately 5 the Bowmonk unit is probably functioning correctly If the values differ by more than 5 check to see if the unit settings are correct and that the unit is not due for its annual calibration It may be desirable to perform multiple tests and compare the average results of the sequence of tests If performing these tests as a substitute for actual Bowmonk measurements standard skidding procedures skidding locations and data analysis must still be followed Atch 1 128 of 162 25 November 1997 Stopping Distance feet 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175 180 185 190 200 Table D 4 Average Friction vs Braking Distance 40 50 20 30 mph mph 90 NA 67 NA 54 NA 45 101 38 86 34 76 30 67 27 61 24 55 22 50 21 47 19 43 18 40 17 38 16 36 15 34 14 32 13 30 13 29 12 28 12 26 1
28. of the airfield should be included in the checklist Obtain Mission Data Load Data Traffic Volume Ground Operations Define Airfield Perform Compile Compute Field Tests gt AGLs Passes Define Features Classify Soils Refine Features Compute Allowable Gross Surface Type Layer Thicknesses DCP Select Representative Loads and or Passes Layer Thickness Layer Strengths DCP Profile Use Compile Physical Traffic Type Property Data PPD Determine Test Locations Assess SPACI Visual Inspection of Surface Distresses to Determine Semi prepared Airfield Condition Index SPACI Evaluation Process 500 on Centerline 500 on Centerline Overrun Note For unimproved airfield continue this pattern ae throughout the length For aggregate surfaced Typical Semi prepared Airfield airfields the pattern may be more widely spaced on the remaining portion of the airfield Priority Testing Soft spots Overrun 2 Offsets should be in wheel paths of main gear Centerline Aircraft turnarounds Any area where the aircraft must stop Overrun one test in center Along edges at 500 feet intervals oR Oo NO Typical Apron or Turnaround DCP Test Locations for Semi prepared Airfields Atch 1 154 of 162 25 November 1997 Surface Layer Strengths Lack of confinement at the top of the surface layer affects the DCP measurements The penetration depth required to measure the surface laye
29. related friction problems and allow more accurate measurements 2 Many sands occur in a loose state Such sands when relatively dry will show low DCP index values for the top few inches and then may show increasing strength with depth The confining action of aircraft tires will increase the strength of sand All sands and gravels in a quick condition water percolating through them must be avoided Evaluation of moist sands should be based upon DCP test data 3 If the cone does not penetrate significantly approximately one half inch after 10 blows the test should be stopped If the material encountered is a stabilized material or high strength aggregate base course which does not produce Atch 1 155 of 162 25 November 1997 accurate results when penetrated with the DCP it should be cored or augered through its depth and the DCP operation resumed beneath it An appropriate CBR should be assigned to this layer If large aggregate is encountered the test should be stopped and a new test should be performed within a few feet of the first location The DCP is generally not suitable for soils having significant amounts of aggregate larger than 2 inches CBR values for unpenetrable materials must be carefully selected based upon their service behavior Suggested CBR values for such materials are Graded Crushed Aggregate 100 Macadam 100 Bituminous Binder 100 Limerock 80 Stabilized Aggregate 80 Soil Cemen
30. resort Appendix A provides the soil test methods that should be used to determine the soil type in the field Table D 8 provides the correlation used to estimate RCR D 7 Rolling Friction Estimation The rolling friction factor is important when the unsurfaced airfield is soft enough to produce appreciable loose till The aircraft must plow through this loose till and this produces a requirement for slightly longer takeoff distances This loose till depth should be measured at five locations on the runway in accordance with the measuring procedures described in Appendix B Suggested measurement locations include touchdown area initial braking zone point of rotation departure end of runway and other areas where the surface may be softened due to poor drainage improper construction aircraft turning etc Calculate the average of these five till depth measurements to establish the overall runway till depth then refer to Table D 9 to determine the approximate rolling friction factor for the runway surface measured Table D 9 Rolling Friction Guidance Semi prepared Dry Till Depth Rolling Friction Factor Runway Unstabilized dry 0 to 1 5 inches 5 1 51 to 3 5 inches 10 3 51 to 5 75 inches 15 5 76 to 7 75 inches 20 gt 7 75 inches Maintenance Required Unstabilized damp to wet 0 to 1 0 inches 5 Cement stabilized 0 to 0 5 inches 2 Atch 1 136 of 162 25 November 1997 Atch 1 137 of 162 25 November 1997 Appendix E Speci
31. sands or gravelly sands e SP Poorly graded sands or gravelly sands A 1 3 2 Coarse Grained Soils Containing More Than 12 Percent Fines The first letter of the symbol indicates a gravel or sand The second letter is based upon the plasticity characteristics of the portion of the material passing the No 40 sieve The symbol M usually designates a fine grained soil of little or no plasticity The symbol C is used to indicate that the binder soil is predominantly clayey in nature e GM Silty gravels or gravel sand silt mixtures The Atterberg limits plot below the A line on the plasticity chart in Table A 1 or the plastic index is less than 4 Atch 1 46 of 162 25 November 1997 e GC Clayey gravels or gravel sand clay mixtures The Atterberg limits plot above the A line with a plastic index of more than 7 e SM Silty sands or sand silt mixtures The Atterberg limits plot below the A line or the plastic index is less than 4 e SC Clayey sands or sand clay mixtures The Atterberg limits plot above the A line with a plastic index of more than 7 A 1 3 3 Borderline Coarse Grained Soils Coarse grained soils which contain between 5 and 12 percent of material passing the No 200 sieve are classified as borderline and are given a dual symbol for example GW GM Select the two that are believed to be the most representative of the probable behavior of the soil In cases of doubt the symbol representing the poorer of the possible groupings sho
32. the top few measurements of the test in this process In our example the first layer break is located at 420mm or 16 so the thickness of layer 1 is 16 The second layer break is at 800mm or 31 so the thickness of layer 2 is 15 This is continued throughout the depth of the test DCP Index The layer DCP index is established by dividing the depth of penetration by the number of blows In our example the first straight line intersected the depth axis at 70mm and the layer break point at 420mm so the depth for determination of DCP index is 350mm It took 46 blows to reach the first layer break Dividing 350 by 46 results in a DCP index of 7 6 for this layer DCP indexes for the remaining layers are determined the same way by using the number of blows and depth measurements between layer breaks Our DCP index for layer 2 is 14 6 and the DCP index for layer 3 is 35 Atch 1 93 of 162 25 November 1997 CBRs Tables C 2 and are then used to determine the CBRs for each layer In our example the soils tested were classified as SP or poorly graded sand so we used Table C 2 Our depth measurements were in milimeters so we enter the table in the DCP Index mm blow columns as appropriate to find the corresponding CBRs A CBR of 32 resulted for layer 1 CBR 14 for layer 2 and CBR 5 for layer 3 C 3 3 1 6 Special Considerations C 3 3 2 DCP tests in highly plastic clays are generally accurate for depths to approximately 1
33. to Rock Salt Medium No 10 No 40 Rock Salt to Table Salt Fine No 40 No 200 Table Salt to Powdered Sugar Fines No 200 No Minimum Size Not discernible to naked eye Grain Size Groups Steps for Field Identification 1 Select representative sample of soil approximately 1 pint 2 Separate gravel size particles from remainder of soil approximately 1 8 to 3 16 inch and above e Gravel gt 50 GW GP GM GC e Gravel 50 SW SP SM SC or fine grained ML MH CL CH OL OH Atch 1 149 of 162 25 November 1997 3 Estimate fines 200 sieve in original sample sedimentation test may be helpful e For gravels if 10 fines GW or GP if gt 10 fines GM or GC For Sands if 10 fines SW or SP if gt 1096 fines SM or SC e If gt 50 of entire sample lt 200 sieve ML MH CL CH OL OH 4 For gravels and sands with 1096 fines GW GP SW SP check gradation to determine if well graded or poorly graded e Wide range in grain sizes with all intermediate sizes substantially represented GW or SW e Predominantly one size or some intermediate size missing uniform or gap graded z GP or SP 5 For fine grained soils ML MH CL CH OL OH test for organic matter e f distinctive color odor spongy feel or fibrous texture particles of vegetation z OL or OH e f not then ML MH CL CH 6 For fine grained soils ML MH CL CH OL OH and coarse grained soils w
34. to the anvil In some soils with large aggregate the DCP may try to penetrate the soil at a slant rather than from a true vertical direction The operator should not apply force to the handle in an attempt to force vertical penetration This will potentially break the rod or connections Instead the test should be stopped if the handle deviates from plumb more than 6 inches and a new test should be attempted in close proximity of the failed test e Maintenance of Equipment The DCP should be kept clean and all soil should be removed before each test Graphite spray lubricant or oil should be applied to the hammer slide before use each day All joints should be constantly monitored and kept tight Loctite may be used The lower rod should be kept clean and lubricated when clayey soils are tested e Recording Data A suggested format for DCP data collection is shown in Figure C 4 The number of blows and penetration depths must be recorded during the test Depending on the scale used the depth of penetration readings is measured and recorded to the nearest 5 mm or 0 2 inches DCP DATA SHEET 1 No of hammer blows FEATURE DATE between test readings TEST LOCATION 2 Accumulative cone No of DCP Depth penetration after each set of Blows Penetration p Blow Set Index in hammer blows 1 60 7 3 Difference in accumulative penetration 2 at start and end of each hammer blow set 4 3 divided by 1 b Enter 1
35. vehicle bounce Proceed down runway accelerating uniformly to target test speed 4 test speed has been reached maintain uniform speed for 2 sec 5 Perform skid test Apply full braking until coming to a complete stop Remember full rear braking only for quad and cycle 6 Bring vehicle to a complete stop Vehicle and driver MUST remain still for several seconds while Bowmonk unit calculates and records braking information 7 Check test results in the Bowmonk display 8 If data appears valid accept test If data appears invalid reject and repeat test 10 Ready Bowmonk for next skid test If data appears invalid reject test return to previous starting location and repeat steps 1 through 8 If vehicle is not properly aligned with the runway after skidding to a stop wheels pointed straight ahead then pull forward and align vehicle and wheels for next skid Several of the above steps are discussed in greater detail in the following sections D 5 1 1 Target Speed at Braking The following target speeds are recommended for operational skid testing 60 mph for the HMMWV and six pax 50 mph for the quad and cycle Please note that the cycle may not have a speedometer or tachometer so the operator must establish speed when using this test vehicle If the cycle speed is correct to within 10 mph an adequate deceleration value will be measured With all vehicles the driver should attempt to obtain correct target speed with
36. weighing 447 000 Ibs simply change the design load entry C 7 1 1 4 Enter correct base course CBR and thickness C 7 1 1 5 Enter correct subgrade CBR and select the appropriate subgrade frost code C 7 1 1 6 Under usual circumstances do not alter the tire pressure data This is automatically adjusted when the type aircraft is selected C 7 1 1 7 The allowable passes or loads may then be read in the results fields for the surface and subgrade layers The lower of the two numbers would establish the controlling layer for the evaluation Atch 1 100 of 162 25 November 1997 Note This program limits CBR inputs to two layers Careful analysis of the DCP data is required to ensure that the layer data entered in the program represents that which was determined in the field For semi prepared surface evaluations primary concern is given to the DCP data taken from the top 24 inches of soil C 7 1 2 Two steps are required to manually evaluate semi prepared airfields first evaluate for the strength of the surface layer and second evaluate for the thickness of the surface layer and the strengths and thicknesses of underlying layers C 7 1 2 1 Evaluate Surface Layer Strength A nomograph Figure C 9 has been developed to determine the strength of soil required to support a given loading condition based upon the tire pressure load soil strength and traffic The tire pressure is the contact tire pressure the soil strength is the CB
37. with inorganic soils Gray blue or gray and yellow mottled colors frequently result from poor drainage Red yellow and yellowish brown result from the presence of iron oxides White to pink may indicate considerable silica calcium carbonate or aluminum compounds A 2 2 1 2 Grain Size The maximum particle size of each sample should be established This determines the upper limit of the gradation curve Gravels range down to the size of peas Sands start just below this size and decrease until the individual grains are just distinguishable by the naked eye Silt and clay particles are indistinguishable as individual particles Atch 1 49 of 162 25 November 1997 A 2 2 1 3 Grain Shape The shapes of the visible particles should be determined They may vary from sharp and angular to smooth and rounded A 2 2 1 4 Grain Size Distribution An approximate identification can be made by examining a dry sample spread on a flat surface All lumps should be pulverized until individual grains are exposed but not broken A rubber faced or wooden pestle and a mixing bowl are recommended but mashing the sample underfoot on a smooth surface will suffice for an approximate identification Separate the larger grains gravels and some sands by picking them out individually Examine the remainder of the soil and estimate the proportions of visible individual particles and the fines Convert these estimates into percentages by weight of the total sample I
38. zones and imaginary surfaces are in Tables 3 3 3 4 and 3 5 respectively These surfaces are displayed in Figures 3 1 through 3 4 3 4 Taxiways The widths and turning radius are similar to that for class A and B fixed wing airfields but the clearances and grades are less stringent Criteria for taxiways are in Table 3 6 and illustrated in Figure 3 4 3 5 Aprons The clearance as well as the longitudinal and transverse grades for aprons are in Table 3 7 3 6 Airfield Marking Schemes for night and day marking of airfields are illustrated in Figures 3 5 and 3 6 3 6 1 The Visual Assault Zone Marker Panel VAMP The VAMP comes in three different configurations the low medium and the high velocity model the low velocity version to withstand sustained wind blasts up to 150 miles per hour the medium velocity version to withstand wind blasts from 150 to 200 MPH and the high velocity version to withstand winds of 200 MPH and greater We have listed the differences among the three models by design below A drawing of the VAMP is depicted in Figure 3 7 Atch 1 13 of 162 25 November 1997 Table 3 3 Runway End Clear Zone for C 17 Contingency Airfields Contingency Item Item Airfield Description Semi Prepared and AM 2 Remarks 1 Length 152 5 m Measured along the extended runway 500 ft centerline Begins at the runway threshold 2 Wiath at 55m Inner Edge 180 ft Width at 152 5 Outer Edge 500 ft clear zone
39. 1 25 11 24 10 23 10 22 10 22 9 21 9 20 9 20 8 19 8 18 8 18 8 17 7 17 T 16 7 16 7 15 Note Values in table are in units of percent g Atch 1 129 of 162 25 November 1997 Table D 4 Average Friction vs Braking Distance Continued Stopping Distance 20 30 40 50 60 feet mph mph mph mph mph 210 6 14 26 40 58 220 6 14 24 38 55 230 6 13 23 37 53 240 6 13 22 35 50 250 5 12 22 34 48 2 5 5 11 20 31 44 300 4 10 18 28 40 325 4 9 17 26 37 350 4 9 15 24 35 375 4 8 14 22 32 400 3 8 13 21 30 425 3 7 13 20 28 450 3 7 12 19 27 500 3 6 11 17 24 550 2 6 10 15 22 600 2 5 9 14 20 650 2 5 8 13 19 700 2 4 8 12 17 Note Values in table are in units of percent g D 4 Layout Field Test Locations The goal of the field tests is to accurately measure the surface friction characteristics of the contingency airfield In order to meet this goal an appropriate number of skid tests must be conducted at multiple locations on the airfield When conducted in the correct manner at the appropriate locations on the airfield these tests will provide an accurate measure of the airfield surface friction These measurements can then be converted into a C17 RCR The following sections detail skid testing patterns on the runway number of tests required and procedures for performing skid tests D 4 1 Skid Test Locations Mark the beginning of the overruns at each end of the airfield Place markers at the midpoint of the airfield and then at
40. 12 Driver accelerates down runway towards marker reaching and maintaining selected test speed as accurately as possible 13 Driver performs standard braking procedure when front tires are even with marker Remember that for the quad and the motorcycle that only the rear brakes are to be used for braking no front brakes 14 Driver remains stopped and operates Bowmonk unit accepting or rejecting data as necessary 15 If testing Bowmonk unit the vehicle must be straight to within approximately 15 degrees of original direction of travel If greater than 15 degrees repeat test Atch 1 127 of 162 25 November 1997 16 17 18 19 20 21 22 23 24 25 Observer notes where braking actually begins and if braking wheels locked up resulting in a true skid If braking wheels did not appear to lock up repeat test Locate point on runway where rear tires actually began skidding Observer and or driver measure the point from where braking of the rear tires began to the point where the rear tires are located when the vehicle came to a complete stop Distance is measured in feet Most preferably with survey wheel or survey tape Record vehicle used and skid distance in feet Locate measured distance in column one of Table D 4 Round up to next higher distance if measurement falls between two values Move horizontally along that row until column for speed at which test was conducted is located This number
41. 2 25 November 1997 operators who need to become familiar with the operation and accuracy of these units In the process of performing these procedures all safety considerations and vehicle skidding procedures described in this appendix should still be followed D 3 5 1 Quick Verification of Speed Measurement For this operational check a long flat level area is required The Bowmonk unit is placed in the vehicle of choice as recommended The unit is armed and operated as normal Make sure the unit displays a speed of 0 0 when starting and that the vehicle is accelerated smoothly and uniformly As the vehicle increases in speed towards the target speed the driver watches the speed as displayed on the Bowmonk this is impossible on the cycle and in the HMMWV and six pax a passenger to observe the unit is helpful If when reaching target speed the difference between the speedometer and the Bowmonk is less than 595 then the unit is likely working correctly Multiple units can also be used simultaneously to make comparisons between Bowmonk units This test assumes that the vehicle speedometer is accurate and functioning correctly D 3 5 2 Detailed Verification of the Speed Measurement For this operational check a long distance must be measured out on flat level ground at least 1000 with large physical markers placed at either end such as cones flagging or airfield distance markers The distance should be measured to an accuracy of 1
42. 2 48 146 81 136 88 129 Limit 60 53 12 62 47 143 80 134 87 128 2 a 3Effe tive Turn Angle Y Maximum Steering Angle 65 A Pavement Width for 180 Turn Pd A Nose gear track radius measured from outside face of tire Figure 2 4 Turning Criteria Atch 1 10 of 162 25 November 1997 Section 3 Dimensional Criteria 3 1 Contents This section presents design considerations unique for C 17 contingency airfields This criteria is given as a supplement to the criteria given in AFJPAM 32 8013 FM 5 430 00 2 Planning and Design of Roads Airfields and Heliports With introduction of the C 17 came the requirement to validate existing design criteria or develop new criteria as required to accommodate contingency operations on semi prepared runway surfaces 3 2 Runway and Overrun Descriptions Tables 3 1 and 3 2 provide dimensional criteria for layout and design of assault landing zones 3 2 1 Length For a semi prepared runway located between sea level and 6 000 feet pressure altitude the minimum length requirement for C 17 operations is 3 500 feet with 300 foot overruns on each end This length requirement based upon an RCR of 20 assumes an ambient temperature equal Standard 1962 plus 31 F and a landing gross weight of 447 000 pounds Based upon these same temperature and weight assumptions the runway length will vary with different RCRs as follows Pressure Altitude Runway Len
43. 2 inches At deeper depths clay sticking to the lower rod may indicate higher CBR values than actually exist Oiling the rod will help without significantly impacting the test results It may be wise to auger out the test hole after each 12 inch depth encountered to eliminate the clay related friction problems and allow more accurate measurements Many sands occur in a loose state Such sands when relatively dry will show low DCP index values for the top few inches and then may show increasing strength with depth The confining action of aircraft tires will increase the strength of sand All sands and gravels in a quick condition water percolating through them must be avoided Evaluation of moist sands should be based upon DCP test data If the cone does not penetrate significantly approximately one half inch after 10 blows the test should be stopped If the material encountered is a stabilized material or high strength aggregate base course which does not produce accurate results when penetrated with the DCP it should be cored or augered through its depth and the DCP operation resumed beneath it An appropriate CBR should be assigned to this layer If large aggregate is encountered the test should be stopped and a new test should be performed within a few feet of the first location The DCP is generally not suitable for soils having significant amounts of aggregate larger than 2 inches CBR values for unpenetrable materials must be carefully
44. 3 Atch 1 135 of 162 25 November 1997 D 6 2 1 Mean Deceleration Measurements from Measured Skid Distance If a Bowmonk unit is not available or if the unit should malfunction in the field this procedure can be used to obtain an RCR value The skidding and distance measurement procedure as described in the operational paragraph D 3 5 6 Verification by Direct Measurement of Skid Distance should be followed Actual skid tests should be conducted in the number described in paragraph D 4 2 Number of Tests Required and in the test patterns shown in Figure D 9 Skidding tests should be conducted as described in paragraph D 5 Performing Skid Test Skid speeds of 40 mph should be used Once testing is complete each skid distance measurement is converted to a mean deceleration value as described in paragraph D 3 5 6 Verification by Direct Measurement of Skid Distance and shown in Table D 4 The overall average for these mean deceleration values is then calculated This average mean value is compared to column three of Table D 7 to determine the equivalent C 17 RCR value D 6 2 2 Correlation with Soil Type Classification In lieu of collecting any actual skid test data on the airfield surface the characteristic friction parameter RCR may be estimated based on soil type and classification or strength data collected to assess the structural suitability of the airfield This method is the least accurate and should only be used as a last
45. 3 of 162 25 November 1997 sample will become firm resisting deformation Cracks will occur as pressure is continued and the sample will crumble If the water content is still adequate shaking the broken pieces will cause them to liquefy again and flow together e Results This process can only occur when the soil grains are bulky and noncohesive Very fine sands and silts are readily identified by this test Even small amounts of clay will tend to retard the reaction to this test A rapid reaction is typical of nonplastic fine sands and silts A sluggish reaction indicates slight plasticity indicating the silt has small amounts of clay or organic silts No reaction at all does not indicate a complete absence of silt or fine sand A 2 2 3 5 Bite or Grit Test e Procedure Grind a small pinch of soil lightly between the teeth e Results Sandy soils The sharp hard particles of even fine sands will grate very harshly between the teeth and will be highly objectionable Silty soils Silt grains are not particularly gritty but their presence is still quite unpleasant and easily detected Clayey soils Clay grains feel smooth and powdery like flour Dry lumps will stick when lightly touched with the tongue A 2 2 3 6 Shine Test e Procedure Rub a clay sample with a fingernail or smooth metal surface such as a knife blade e Results Highly plastic clay will produce a definite shine Lean clays will
46. 4 9 Design Parameters The design of contingency airfields requires a knowledge of the design aircraft the gross weight of the aircraft the mission traffic requirements the type of traffic area preliminary soil strength data and frost conditions Each of these parameters is described below 4 9 1 Design Aircraft The criteria presented is for the design of contingency airfields exclusively for the C 17 aircraft If the C 17 is to be used in conjunction with other Atch 1 29 of 162 25 November 1997 aircraft i e C 130 the C 17 will be the critical aircraft for the structural design of contingency airfields 4 9 2 Aircraft Gross Weight The gross weight of the aircraft is the combined weight of the empty aircraft the cargo and the fuel The operating weight of the C 17 aircraft is 279 000 Ibs or 279 kips The maximum gross weight of the aircraft is 586 kips However the maximum gross weight for operations on contingency airfields for the C 17 aircraft is 447 kips which is also typically the design gross weight for contingency operations 4 9 3 Mission Traffic Requirements The mission traffic requirements refer to the number of aircraft passes that an airfield must sustain in order to fulfill mission requirements Contingency airfields typically have a short design life and a reasonable estimate of the mission s requirements in terms of aircraft passes is required in order to produce an adequate airfield design with the minim
47. 4mL225 66 200 7 L APPROACH DEPARTURE SURFACE PLAN NTS NOTES 1 TAXIWAY CLEAR AREA WIDTH 33 5m 110 FOR C 17 From centerline taxiway to obstacle S ga NG BETWEEN MULTIPLE NS IS DETERMINED BY TOPOGRAPHY MISSION 500 3S TRUCTI BUT SHALL NOT BE LESS THAN 500 APART S AT BOTH END OF THE RUNWAY MUST BE PROVIDED AND OBSTRUC PARALLEL TAXIWAY OR TURN AROUND AR Figure 3 2 C 17 Contingency Airfield Detail Atch 1 17 of 162 25 November 1997 ov H LENGTH 91 j ACCIDENT POTENTIAL ZONE 1 762 0m 25007 PLAN NTS RUNWAY END ELEVATION LONGITUDINAL SECTION NTS LEGEND Figure 3 3 C 17 Contingency Airfield Runway Imaginary Surfaces Atch 1 18 of 162 25 November 1997 lt 2 B CERE a 5 A T 2 uy 2j ol Figure 3 4 C 17 Contingency Airfield Runway Taxiway and Apron Section Atch 1 19 of 162 25 November 1997 Table 3 6 Taxiways for C 17 Contingency Airfields Contingency Airfield Item Semi Prepared and AM 2 Description Remarks 3 Shoulder Width Shoulders should be stabilized to prevent erosion by jet blast Where adequate sod cover cannot be established the shoulders should be chemically stabilized for blast protection Remove all tre
48. 5 1 8 7 7 150 5 9 2 3 26 1 0 5 1 47 1 9 1 6 50 2 0 7 0 155 6 1 2 3 27 1 1 4 7 48 1 9 1 5 55 2 2 5 3 160 6 3 2 2 28 1 1 4 4 49 1 9 1 4 60 2 4 5 8 165 6 5 2 1 29 1 1 4 1 50 2 0 1 4 65 2 6 5 4 170 6 7 2 0 30 1 2 3 8 51 2 0 1 3 70 2 8 5 0 gt 175 gt 6 9 20 31 1 2 3 6 52 2 0 1 3 75 3 0 4 6 32 1 3 3 4 53 2 1 1 2 80 3 1 4 3 33 1 3 3 2 54 2 1 1 2 85 3 3 4 1 34 1 4 3 0 55 2 2 1 1 90 3 5 3 9 35 1 4 2 8 56 2 2 1 1 95 3 7 3 7 36 1 4 2 7 57 2 2 1 1 100 3 9 3 5 37 1 5 2 5 58 2 3 1 0 105 4 1 3 3 38 1 5 24 gt 59 gt 23 10 110 4 3 3 2 39 1 5 2 3 es ee em tS SERERE TTE MM Am 11 _ 1 eS cc a o NEM du m 10 100 DCP MM BLOW Figure C 6 Plotted Correlation of DCP Index vs CBR Atch 1 92 of 162 25 November 1997 DEPTH MM CUMULATIVE BLOWS 0 10 20 30 40 50 60 70 80 90 100 1300 Figure C 7 Manual Plot of DCP Data Plot Annotate the total number of blows needed in a particular DCP test being plotted along one axis of the graph Annotate the depth of penetration along the other axis Then plot the points as recorded on the DCP Data Sheet Layers Draw straight lines tangent to or through the points that are reasonably straight These lines indicate the soil layers with the intersecting points indicating the layer breaks Disregard
49. 65 21 47 83 NA NA 70 19 43 77 NA NA 75 18 40 72 NA NA 80 17 38 67 NA NA 85 16 36 63 99 NA 90 15 34 60 93 NA 95 14 32 57 88 NA 100 13 30 54 84 NA 105 13 29 51 80 NA 110 12 28 49 76 NA 115 12 26 47 73 NA 120 11 25 45 70 NA 125 11 24 43 67 97 130 10 23 41 65 93 135 10 22 40 62 90 140 10 22 38 60 86 145 9 21 37 58 83 150 9 20 36 56 81 155 9 20 35 54 78 160 8 19 34 53 76 165 8 18 33 51 73 170 8 18 32 49 71 175 8 17 31 48 69 180 7 17 30 47 67 185 7 16 29 45 65 190 7 16 28 44 64 200 7 15 27 42 61 210 6 14 26 40 58 220 6 14 24 38 55 230 6 13 23 37 53 240 6 13 22 35 50 250 5 12 22 34 48 275 5 11 20 31 44 300 4 10 18 28 40 325 4 9 17 26 37 350 4 9 15 24 35 375 4 8 14 22 32 400 3 8 13 21 30 425 3 7 13 20 28 450 3 7 12 19 27 500 3 6 11 17 24 550 2 6 10 15 22 600 2 5 9 14 20 650 2 5 8 13 19 700 2 4 8 12 17 Values in Table are in units of percent g AVERAGE FRICTION VS BRAKING DISTANCE Atch 1 145 of 162 25 November 1997 E 1 2 2 Condition Survey Maintenance Data The following charts should be included in the checklist Runway Layout 500 Sections Coincide with Markers z 2 rc gt OVERRUN Distress Locations Distress Types By Section 95 Rolling Resistant Mat m el zs a Stabilized Layer Failure Distress Locations Additional Features Sections Taxiways Aprons Turnarounds Etc Identify Features Section Distress Types mu pp 1 Resistant Mat 97 Stabilized
50. 69 ft 9 in 51 74 m to Winglet Tips ft O in 19 81 m 7 ft 9 in 2 36 m 33 ft 8 in 10 26 m 45 ft 9 in 13 94 m 13 72 m E 111 ft 8 in 34 04 m 119 ft 11 in 36 55 m 47A ft 0 in 53 04 m Figure 2 1 Horizontal and Vertical Aircraft Dimensions Atch 1 7 of 162 25 November 1997 57 ft9 in E 17 59 in 65 ft 10 in 20 06 m 11 ft 0 in 3 35 m 59 ft 1 in 48 49 m gt Figure 2 1 Horizontal and Vertical Aircraft Dimensions Continued 24 ft 11 in 7 60 m Aft Gear 33 ft 8 in Gear Tires 10 26 m Nose Landing 11 5 in 0 29 m Typ 2ft5in 0 74 m 25 ft 2 in Main Landing Gear Tires 7 67 m Foward Gear Axle Centerline a 62112 in 18 95 m Figure 2 2 Landing Gear Dimensions Atch 1 8 of 162 25 November 1997 Aircraft Classification Numbers The International Civil Aviation Organization has developed and adopted a standardized method of reporting pavement strength for conventional rigid and flexible pavements This procedure is known as the Aircraft Classification Number Pavement Classification Number ACN PCN The ACN is a number that expresses the effect an aircraft will ha
51. 96 1000 10 or 4000 40 for example The distance between 1000 markers on most airfields is not always exactly 1000 0 so it is important to verify this accurately The driver then accelerates the vehicle to the target speed and maintains the vehicle at this constant speed for at least 2 seconds to stabilize the vehicle speed The driver then uses a stopwatch accurate to at least 0 1 sec to time how long it takes to traverse this known distance The marker time measurements should be made to within 0 25 seconds and a passenger to make the timing measurements is helpful The driver should maintain as constant a speed as possible over the length of the timing course by watching the odometer closely This total distance in feet is divided by the time to cover that distance in seconds to obtain a velocity in feet per second This velocity in feet per second is then converted to mph by multiplying the speed in feet per second by 0 6818 After the driver passes the second timing marker then a skid test is performed The skid test must be of high quality i e a smooth level skid with little vehicle bounce with the vehicle ending straight for this operational check to be made see section on skid test procedures and requirements The speed calculated from the time to traverse the measured distance is the actual velocity This actual velocity is then compared to the odometer indicated velocity and the Bowmonk measured velocity If the percent
52. FROM AFCESA CES 139 Barnes Drive Suite 1 Tyndall AFB FL 32403 5319 SUBJECT Engineering Technical Letter 97 9 Criteria and Guidance for C 17 Contingency and Training Operations on Semi Prepared Airfields 1 Purpose This ETL provides criteria and guidance for design construction maintenance and evaluation of semi prepared airfields for contingency and training operations of C 17 aircraft It supersedes ETL 97 9 dated 15 October1997 Visual Flight Rules VFR apply for the dimensional criteria in Section 3 2 Application All Department of Defense organizations responsible for design construction maintenance and evaluation of airfields 2 1 Effective Date Immediately Remains in effect until these requirements are incorporated into FM 5 430 00 01 2 AFJPAM 32 8013 Planning and Design of Airfields in the Theater of Operations El 02C013 TM 5 808 7 Airfield and Heliport Planning and Design and or AFJMAN 32 1014 Airfield Pavement Design 2 2 Ultimate Recipients e Base Civil Engineers and Red Horse Units responsible for design construction and maintenance of airfields e Army Corps of Engineers Marine and Navy offices responsible for design maintenance and construction of airfields 3 Criteria and Guidance Criteria and guidance attached are based on very limited data Structural and flight tests were accomplished at only one AM 2 location three mechanically stabilized locations with similar soil types and climatic condit
53. HMMWV and 6 Pax push on the brake as hard as possible to lock up all four tires and then skid to a complete stop For the cycle and quad it was unsafe to lock up both the front and back brakes so the procedure to be used for all tests is locking up the back brakes only Runup Lengths and Stopping Distances Notice also that there is a certain required runup length for each skid test The evaluator should think through the test sequence after arriving on site and carefully plan the skid test locations to achieve maximum efficiency and avoid aborted test runs because he she ran out of room before they reached desired test speed For planning purposes with 40 mph test speeds the following table is provided Maximum Required Runup Length Stopping Distance Skid Vehicle Required ft HMMWV 1400 300 6 Pax 1200 250 Quad 1000 175 Cycle 700 125 Friction Test Procedure Bowmonk Operation Any of the following items in bold are extremely important and must be followed Atch 1 142 of 162 25 November 1997 10 11 Align test vehicle with runway on one of the two longitudinal test lines previously identified i 30 feet to the left of centerline or ii 30 feet to the right of centerline Both vehicle and tires should be straight Turn unit on by pressing RESET letting unit go through self check Unit will display AFM2 READY once self check is complete jArm Bowmonk device for test Device should be armed just prior to vehicle accele
54. HOW TO MEASURE Stick a ruler into the RRM until you hit solid ground and read the number on the ruler at the top of the RRM to the nearest inch Take a minimum of seven measurements in each gear path and average those measurements Determine average RRM depth by averaging the measurements in the touchdown area in the primary braking area at the point of rotation and the last 500 feet of runway Fora typical 4000 foot runway take one set of measurements at approximately 54 00 10 00 20 00 and 35400 and average those four sets of fourteen measurements GREEN Measure here AU N RRM VIN E 0 315 inches V RRM exists but is less than 31 2 inches deep Runway RRM 31 2 73 4 inches LN e RRM is 31 2 73 4 inches deep 1 RRM greater than 73 4 inches RRM is greater than 73 4 inches deep Atch 1 66 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS aed Bicycle Lake pae 72 97 Section 17 4S9 AO 00 Inspector 3 I Skak SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY EAMA REMARKS NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation RRM Amber Severity Atch 1 67 of 162 25 November 1997 96 JET BLAST EROSION DEFINITION Jet blast erosion o
55. It must also be determined if adequate thickness of the 16 CBR material is available Enter Figure 4 2 at the top with the in place subgrade CBR 16 and draw a vertical line down until it intersects the design gross weight of the C 17 or 447 kips Next draw a horizontal line from this intersection until it intersects the design pass level of 400 passes Finally draw a vertical line from this intersection downward until you intercept the required thickness Seven inches of 16 CBR material is required to support 400 passes of a 447 kip C 17 aircraft Since the in place soil has 24 inches of 16 CBR material the unsurfaced airfield can support the design aircraft for the design passes without structural improvement Step 5 Since there is a 12 inch layer of weaker material underlying the surface layer it must be determined if the surface soil layer has adequate thickness to protect the underlying weaker layer Enter Figure 4 2 with the weak layers CBR 10 and draw a vertical line down until it intersects the design gross weight of the aircraft or 447 kips Next draw a horizontal line from this intersection until it intersects the design pass level of 400 passes Finally draw a vertical line from this intersection downward until you intercept the required material thickness Nine inches of a 15 CBR material is required to protect the weak subsurface soil layer Since the in place soil has 24 inches of a 16 CBR material the weak layer is adequately pro
56. Layer Failure Atch 1 146 of 162 25 November 1997 Distress Severity Levels Distress Types GREEN AMBER RED 91 Potholes 4 Deep and or 4 to 9 Deep and 9 Deep and 15 Diameter gt 15 Diameter 215 Diameter Exist but 4 Deep 4 to 9 Deep 29 Deep 93 Loose Covers between 1 10 and 1 2 Does not obstruct visibility Partially obstructs visibility Thick obstructs visibility 95 MEM Exist but 3 5 Dee 3 5 to 7 75 Dee 7 75 D Resistant Mat b i gt 7 96 Jet Blast 97 Stabilized is _ Note Potholes ruts and rolling reistant material are considered major distresses Depending upon actual distress location any of these distress types categorized as RED may cause overall airfield condition to be RED Rolling Friction Guidance Semi prepared Dry Till Depth Rolling Friction Factor Runwa Unstabilized dry 0 to 1 5 inches 5 1 51 to 3 5 inches 10 3 51 to 5 75 inches 15 5 76 to 7 75 inches 20 gt 7 75 inches Maintenance Required Unstabilized damp to wet 0 to 1 0 inches 5 Cement stabilized 0 to 0 5 inches 2 Deduct Values for C 17 Operations Green Amber Hed Distress R T HA R T HA RT 91 Potholes 4 2 10 6 20 12 92 Ruts 14 4 18 6 24 10 93 Loose Aggregate 4 15 6 30 8 45 94 Dust 2 15 4 30 6 45 95 Rolling Resistant Material 18 2 22 4 26 15 96 Jet Blast Erosion 5 10 10 30 15 40 97 Stabilized Layer Failure 5 15 10 25 15 35 Atch 1 147 of 162 25 Novem
57. NT TEST N Press A instead of ENTER as described in the steps above This only applies to a results table printout Unit will print results tables from test N up to the last test carried out Press RESET at anytime to terminate printout See Figure D 8 b Results Table printout for an example Note that both peak and mean values are given for each test If using the mean friction value measurements to determine a C 17 RCR then the average for all the means must be calculated After performing the skid tests in the number and manner described elsewhere in this appendix a results table must be printed out for each test Total the mean values for each test then divide that total by the number of tests to determine the overall average mean friction value for that series of tests As an example look at the data shown in Figure D 8 b Results Table The three mean friction values are 66 g 71 g and 68 g The total value is 205 g Divide 205 by a total of three tests for an average mean value of 68 3 g for this series of tests This overall average mean friction value is the number that is used in Table D 7 to calculate a C 17 RCR An overall average mean friction value is highly preferable to an overall average peak friction value for determining a C 17 RCR D 3 3 3 Download Skid Data The following procedure is to be used for uploading data from the Bowmonk Mk II Airfield Friction Meter to a field laptop or portable computer Th
58. R of the surface layer the traffic is measured in coverages and the load is the single wheel load or the equivalent single wheel load ESWL To use this nomograph e Enter the chart with the expected contact tire pressure of the aircraft being evaluated See Table C 5 for contact tire pressure data for the C 17 at various mission gross weights e Move vertically to the appropriate ESWL curve See Table C 5 for ESWLs for various gross weights e Move horizontally to the right edge of the chart e At that point project a straight line through the measured CBR value of the surface layer to read the number of coverages e Convert coverages to passes using Table C 5 Table C 5 ESWLs and Tire Pressures for C 17 Aircraft Gross Surface Contact Tire Pass Coverage Weight ESWL Pressure Ratio Aircraft kips kips psi A Traffic C 17 580 55 2 142 1 37 500 47 5 122 450 42 9 110 425 40 5 104 400 38 1 98 350 33 3 84 Note A coverage differs from a pass A pass simply represents an aircraft movement across a given point on the airfield whereas a coverage takes into account the fact that aircraft wander somewhat and the wheels do not follow the same identical path on each pass To determine the number of passes multiply the number of coverages by the pass coverage ratio for the aircraft and traffic area being evaluated C 7 1 2 2 Evaluate Surface Layer Thickness e Select Figure C 10 Semi Prepared Surface Evaluation Curve C 17 Atch 1
59. REEN Less than Less than 15 inches 4 inches T Potholes are less than 4 inches deep and or less than 15 inches in diameter AMBER Y lt Greater than 228 15 inches inches Potholes are 4 9 inches deep and greater than 15 inches in diameter RED Y Greater than 15 inches Greater than 9 inches T Potholes are greater than 9 inches deep and greater than15 inches in diameter Atch 1 58 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Aue Bicycle Lake Date 4 12 97 Section 24 50 o 7 09 Inspector Kew Shepherd SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Potholes Amber Severity Atch 1 59 of 162 25 November 1997 92 RUTS DEFINITION Ruts are surface depressions in the wheel paths that run parallel to the centerline They result from repeated aircraft passes and become more severe with time HOW TO MEASURE Lay a straightedge across the ruts with both ends resting on the solid runway surface with loose rolling resistant material removed Measure the depth of the three deepest ruts on each side from the bottom of the straightedge to the solid ground in th
60. San cae QU Qu s m uu are ca n i M e qo ue rus d MAREM Mum 1s LEEY T s i n BONHEUR m There b a thin dust Chock that does net obstruc vetite Obetructed There a moderately Chick cles that nartaly obstructs vieiitby Severe Visibility Problem There amp thick cxudthat obetructs visbisty Atch 1 64 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Aitea Bicycle Lake pate 4 12 97 Section 17 50 20 O Inspector eve Bole SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY SPACI CALCULATIONS Distress Deduct Type Severity Value Total deduct value NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Dust Red Severity Atch 1 65 of 162 25 November 1997 95 ROLLING RESISTANT MATERIAL DEFINITION Rolling resistant material RRM is any type of loose or unbound material that separates from the solid base and lies on top of the surface and in the ruts In sufficient quantities it increases the rolling resistance and therefore increases the amount of runway required for C 17 takeoffs It is more prevalent in dry soils and is a byproduct of severe rutting
61. a stabilized layer A failure occurs when areas of that layer begin to crack and delaminate It is a progressive failure The number and size of cracks increase layers can delaminate and pieces can be removed The cracks get closer together and interconnect until the surface resembles an alligator skin this is called alligator cracking and usually indicates weak support beneath NOTE An abrupt vertical change of more than 2 inches may cause nose gear damage The runway surface must be repaired before the airfield can be used HOW TO MEASURE Put a straightedge across the failed area and measure the depth Treated Layer Cracks d TOUT EH EHE pH EE EEEE TEE EE Ep EE FECE R 4 ech ete Less than 1 inch S 505059 Se A with minor cracking or degradation Treated Layer Alligator Cracks 1 2 inches with alligator cracking and possible delamination Treated Layer Alligator Cracks 4A Greater than 2 inches with flying objects or debris FOD potential and delamination 2529 t te t gt id 25 ms t to ch 55 EHE HEEL ERE LU RU tot tt tt tt tt LLL LCS EEEE EEEE EE rrr t ata EE ERECTO E EE heheheh ted ETE EC ELE HE EE EE EE ECR CECE ER ERE EE EE EE E HERE EE 2 7 5 xo Bre tte is t t rt 5 55 oS 55 to
62. able 4 3 Table 4 2 Recommended Gradation for Crushed Rock Slag Uncrushed Sand and Gravel Aggregates for Base Courses Percent Passing Each Sieve Square Openings by Weight Sieve Maximum Aggregate Size Designations 2 inch 1 ve inch 1 inch 1 inch sand clay 2 inch 100 1 ve inch 70 100 100 1 inch 55 85 75 100 100 100 34 inch 50 80 60 90 70 100 3 8 inch 30 60 45 75 50 80 No 4 20 50 30 60 35 65 No 10 15 40 20 50 20 50 65 90 No 40 5 25 10 30 15 30 33 70 No 200 0 10 5 15 5 15 8 25 Atch 1 26 of 162 25 November 1997 Table 4 3 CBR Ratings for Base Course Materials Material Type Design CBR Graded crushed aggregate 100 Water bound macadam 100 Dry bound macadam 100 Lime rock 80 Soil cement 80 Sand shell or shell 80 4 7 Compaction Requirements The recommended compaction requirements for the base subbase select material and subgrade are shown in Table 4 4 In general the top six inches of the subgrade is compacted to density requirements indicated in Table 4 4 Table 4 4 Recommended Compaction Requirements for Semi Prepared Airfields Percent Compaction Material CBR Required Cohesive Cohesionless Base course 80 100 NA 100 105 Subbase 20 50 NA 100 105 Select material amp Subgrade 20 90 95 95 100 Notes 1 A cohesive soil has a PI gt 5 a cohesionless soil is one with a PI lt 5 2 Cohesive soils are Not Applicable NA for use as a base or subbase 3 Percent compaction i
63. ace material Then reevaluate the subgrade soil strength by one of the methods described above and compare the compacted in place CBR to the required CBR from Figure 4 1 Next determine the minimum thickness of the required CBR from Figure 4 2 Enter Figure 4 2 at the top with the in place subgrade CBR and draw a vertical line down until it intersects the design gross weight of the aircraft Then draw a horizontal line from this point until it intersects the required design passes Finally draw a vertical line down from the required pass level until it intersects the required thickness This thickness is the required thickness in inches of a material of the minimum surface CBR determined from Figure 4 1 necessary to support mission requirements If the in place subgrade CBR is equal to or greater than the minimum subgrade CBR determined from Figure 4 1 and the preliminary site investigation revealed that the depth of the in place subgrade CBR is equal to or greater than the thickness determined from Figure 4 2 then the airfield is structurally Atch 1 32 of 162 25 November 1997 adequate to support the design traffic If a weaker soil layer is encountered at some depth below the surface soil layer the thickness of material required to protect the weaker soil layer should be checked using Figure 4 2 Enter Figure 4 2 with the weak layer s CBR rather than the surface layer s CBR If the thickness of the surface layer is not sufficient to protec
64. aching desired test velocity As vehicle accelerates unit will indicate current speed Apply full brakes quad and cycle rear brakes only until vehicle comes to a complete stop Atch 1 115 of 162 25 November 1997 BOWMONK AFM2 AIRFIELD FRICTION METER MKII AUTO START STOP Stripchart Printout 99 TEST MEMORY of Results AUTO SWITCH OFF press RESET to switch on read OPERATING INSTRUCTIONS before use Displayed Results Control Panel Figure D 5 Instrument Panel of the Bowmonk Unit Atch 1 116 of 162 25 November 1997 Figure D 6 Two Bowmonk Devices Installed in a HMMWV Atch 1 117 of 162 25 November 1997 Unit will display DON T MOVE CALCULATING Keep the vehicle stationary to allow unit to complete its internal calculations and display results Unit will now display measured PERCENT G first line and SPEED second line f the results are acceptable save the test results by pressing A to accept this test The unit will now display AFM2 READY f the result is not acceptable press RESET the instrument will discard the current test and display AFM2 READY Another test can be performed and saved with the same test number Ready vehicle for next test and repeat from step 2 to perform subsequent tests Continue until desired number of friction tests are completed The Bowmonk unit will automatically shut down after 4 minutes of inactivity to save t
65. ad bearing capability of an airfield to sustain C 17 contingency operations Appropriate evaluation charts are included This appendix does not address the geometric characteristics of an airfield such as runway length and width gradient criteria or airfield and airspace clearances C 1 1 The HQ AFCESA Pavement Evaluation Team is tasked to assess the suitability of airfields for projection of U S forces in support of regional conflicts or stability and support operations Other Air Force units such as Red Horse Squadrons and Special Tactics Teams STTs are also tasked to perform contingency evaluations of semi prepared airfields These taskings have increased substantially in recent years and have highlighted the need to ensure those tasked are sufficiently trained and to standardize evaluation procedures C 1 2 The procedures presented here see Figure C 1 are those required to adequately evaluate an airfield In cases where in the field evaluation time is limited and judgments must be made on limited available data the reliability of the evaluation is questionable Sound judgment must be used in reporting airfield suitability in such situations If evaluation results indicate the airfield will not support the intended pass or load levels refer to Section 4 Structural Design Criteria to determine upgrade requirements Obtain Mission Data Load Data Traffic Volume Ground Operations Define Airfield Perform Compile Compute gt Fie
66. al Tactics Team Checklist E 1 Current operator checklists used by AFSOC Special Tactics Teams STTs to verify suitability of semi prepared airfields for C 17 operations should be updated to reflect the guidance given in this ETL which supersedes the criteria contained in AFJPAM 32 8013 FM 5 430 Volumes 1 and 2 Planning and Design of Roads Airfields and Heliports in the Theater of Operations in regards to C 17 airfield criteria E 1 1 Chapter 3 page 7B C 17 Characteristics Airfield Data should be updated to reflect the following Runway Single Point Refuel Panel Length 3 500 Nose to Spr Unk Width 90 Side Right Width 180 TURN 165 Lateral Safety Zone 35 Turnarounds Obstruction Slope 5 1 Length 180 Width 165 Overruns Length 300 Width 90 Taxiway Distance RWY Weights centerline to Operating Wt Empty 279 000 TXY edge 280 Max Landing Wt Paved 586 000 Width 60 Max Landing Wt AM 2 560 000 Turn Radius 90 Max Landing Wt Semi prepared 447 000 Shoulder 10 Clear Area 70 Wind Limits Apron Max Wind TBD Distance Tailwind TBD Apron edge to Crosswind 30 fixed object 100 Runway length of 3 500 ft for locations 0 to 6 000 ft Pressure Altitude This requirement assumes an RCR of 20 90 F Ambient temperature Standard 1962 31 F and a Landing gross weight of 447 000 pounds Using the same temperature and weight assumptions the different RCRs will influence the required runway lengths as follows Atch 1 138 of 162
67. allet a motorcycle and a quad The six pax truck is typically available to RED HORSE units and airfield pavement evaluation teams APE the HMMWV is available to Army Engineer Battalions and the AFSOC Special Tactics Teams STT have access to the HMMWV quad and cycle Atch 1 110 of 162 25 November 1997 The ground vehicle selected should be one of these four vehicles since these particular vehicles were used to establish the initial data correlations to the aircraft If a vehicle other than one listed above is used to collect data the data correlation will not be valid The mission commander must make the ground vehicle selection issue based on several factors including mission requirements equipment availability operational considerations safety and desired data accuracy If the commander has the latitude to use any of these four vehicles then the vehicle that gave the most accurate correlations to the aircraft should be used These were from best to worst HMMWV truck quad and cycle all gave acceptable correlations but there were differences in accuracy Standard safety equipment should always be used by the test driver when performing these tests including seat belts and helmets Since all the testing and the resulting correlations were done with the tire types shown in Table D 1 it is recommended that these same tires be used if at all possible If it is not possible to use these same tires then at a minimum similar tire
68. are frost susceptible See Table C 4 Frost Design Soil Classifications Areas of frost heave when no longer frozen may have large subsurface voids and will not support projected loads These areas must be properly recompacted C 3 3 2 4 Wet Climate Soil layer strengths in areas subject to heavy seasonal rains or flooding may react similarly to those in frost susceptible areas This is particularly true in the case of fine grained materials containing clays and or silts where there is no adequate surface seal or positive drainage away Moisture conditions at the time of testing should be documented Is it dry damp or wet and anticipated conditions for the projected usage period must be considered in determining the validity of test data for intended aircraft operations C 4 Obtain Aircraft Operational Requirements C 4 1 Obtain aircraft operational requirements from the Site Operations Officer local Command Section or the tasking OPR C 4 2 Data Required for C 17 Aircraft Atch 1 95 of 162 25 November 1997 Table C 4 Frost Group Designations for Soil Classification Required for Frost Design 96 by Frost Weight Typical Soil Types wet Type of Soil lt 0 02 mm under the USCS Gravels e gt 0 25 Seis Crushed Rock b Sands e 0 30 Sands e gt 0 30 a Gravels e 0 25 Crushed Stone Crushed Rock b Gravelly soils O OWO W 0 GW GP GW GM
69. atory roller Rubber tired and sheepsfoot rollers are most effective for compacting cohesive soils A towed sheepsfoot with a contact pressure of 400 600 psi or a 35 to 50 ton rubber tired roller with four wheels will usually yield satisfactory results Vibratory rollers are effective on some cohesive soils particularly those containing granular fractions such as SC SM GC and GM Use steel wheel rollers to seal the surface of cohesive soils to decrease rainfall penetration B 2 3 Cohesionless Soils These soils are relatively clean sands and gravels not highly moisture sensitive and relatively pervious They include SW SP GW and GP soil types Optimum moisture content and maximum dry density may need to be considered depending upon the type and quantity of soil fines If a granular soil contains essentially no fines optimum density can be achieved when the soil is almost saturated Cohesionless soils often require continuous wetting during compaction to prevent bulking These soils can be compacted most effectively by vibratory rollers with a total drum force of 15 20 tons Rubber tired rollers are somewhat less effective Steel wheel rollers are normally used to obtain a smooth finish surface B 2 4 Compaction Method The choice of compaction equipment should depend upon soil type and moisture content Equipment should be tracked over the material at least four times both parallel and perpendicular to the centerline of the runway Traffi
70. ay will show AFM2 READY Press ENTER to enter Editing Mode Use UP ARROW and DOWN ARROW to move between menus Move to CLEAR MY MEMORY menu Press ENTER Unit will display ALL RECORDS LOST PRESS ENTER TO ACCEPT RESET TO ESCAPE Press ENTER to clear memory Unit will display AFM2 READY Press S and PRINT at the same time to turn unit off D 3 4 Predeployment Operational Checks and Procedures The following sections detail procedures that can be performed as predeployment steps to save time in the field or verify proper functioning of unit before actual deployment Atch 1 122 of 162 25 November 1997 D 3 4 1 Entering Header Information This section details the steps necessary to enter Header information in the Bowmonk unit This can be done before arriving on site to save time in the field The unit will retain this information until it is changed Entering this information is useful for data documentation but not necessary for proper operation of the unit Press RESET to turn unit on if not already on Unit will display AFM2 READY Press ENTER The display will show EDITING MODE Press UP ARROW and the display will show EXAMINER ID Press ENTER again You may now enter the Examiner ID Use the UP ARROW and DOWN ARROW to select a letter Press ENTER to accept that letter and move to the next letter Press and hold ENTER whe
71. ber 1997 R T Runways and taxiways Hammerheads and aprons EE DE EM NIE Number of deduct values equal to or greater than 5 E BE 100 Pk CS 000 2 10 0 20 40 60 80 100 120 140 160 180 200 Total Deduct Value Semi Prepared Airfield Condition Index SPACI Correction Curves for Total Deduct Values Enter bottom of chart with the total of all deduct values determined for each distress Extend line vertically until it intersects the correct q line number of individual distress deduct values that are equal to or greater than 5 At this point draw line horizontally to determine the Semi prepared Airfield Condition Index SPACI SPACI Scale Atch 1 148 of 162 25 November 1997 E 1 2 3 Soil Identification The following charts related to field soil characterization should be included in the checklist Soil Groups Symbol Gravel Sand Silt Clay Ozoco o Soil Characteristics Well graded Poorly graded High compressibility Low compressibility Organic peat Organic silts and clays Liquid limits under 50 Liquid limits over 50 Erozr sya o Soil Groups Symbols Size Group Passing Retained On Example Boulders No Maximum Size 12 Inch Cobbles 12 Inch 3 Inch Gravels 3 Inch No 4 Lemon to Pea Coarse 3 Inch 3 4 Inch Lemon to Walnut Fine 3 4 Inch No 4 Walnut to Pea Sands No 4 No 200 Pea to Powdered Sugar Coarse No 4 No 10 Pea
72. box in the severity table 1110 of Area Covered Loose aggregate exists but covers less than 1 10 of the section mowo lt Covered Greater than 112 of Area Covered More than 1 2 of the section has bose aggregate covering the suface Atch 1 62 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS O Sy cle Lake 4 12 97 Section 2 S 2090 00 Inspector Jeh n Holfman SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY te fp epee te fe he SPACI NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Loose Aggregate Amber Severity Atch 1 63 of 162 25 November 1997 94 DUST DEFINITION Dust is fine material that becomes airborne when disturbed The natural material on unsurfaced airfields and the multiple passes of the aircraft cause these fine materials to separate from the soil binder and become a significant problem for personnel trailing aircraft and the environment HOW TO MEASURE Have a vehicle drive at 60 miles per hour down the runway Watch the dust cloud and check the appropriate box on the table For example if you cannot see the vehicle check Red 23 it Lc e Meee ns arte t EE TEE a ey
73. btain the optimum water content Compact to obtain the optimum density Lift thickness may have to be reduced to 2 to 3 inch lifts to obtain the optimum density depending on the compaction equipment available 92 RUTS Wet if dry Scarify Add material as required Rewet if necessary Grade to a proper cross section Rewet as required Compact to a required optimum density Repeat 5 6 and 7 in 2 to 3 inch lifts if needed to achieve the optimum density with the compaction equipment available 93 LOOSE AGGREGATE Wet if dry Scarify if conditions are severe Rewet as needed Add material if necessary Rescarify if material is added Rewet as needed Grade to a proper cross section Compact to the optimum density Wet and compact again if necessary to obtain the optimum density with the compaction equipment available 94 DUST Wet as needed Use a dust palliative Stabilize if time and resources are available Install matting if required by the mission Atch 1 80 of 162 25 November 1997 95 ROLLING RESISTANT MATERIAL Wet Scarify Rewet as needed Grade to a proper cross section Rewet as needed Compact to obtain the optimum density Repeat 5 and 6 in lifts if necessary to obtain the optimum density with the compaction equipment available ALOJI EON 96 JET BLAST EROSION Wet if dry Scarify to include the undisturbed area to ensure good adhesion or bonding of the repair Re
74. ccurs when the top layer of soil is blown or stripped away in the areas that are scoured by the C 17 engines as they fire up to taxi or take off Jet blast erosion outside trafficked areas can be ignored Jet blast erosion in trafficked areas must be maintained Jet blast erosion is characterized by no evidence of loose aggregate HOW TO MEASURE Measure the depth of the erosion and check the appropriate box on the inspection sheet L Mr Jet blast erosion exists but is less than 1 inch deep m 1 3 inches zs Jet blast erosion is 1 3 inches deep m s Greater than 3 inches EJ Jet blast erosion is greater than 3 inches deep Atch 1 68 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Airfield f cycle Lake l12 92 Section 2 7 O 0 4 O O Inspector l rvc Fox SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY Ew fe fete fo PS i e SPACI NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Jet Blast Erosion Green Severity Atch 1 69 of 162 25 November 1997 97 STABILIZED LAYER FAILURE DEFINITION If the runway surface material is mixed with a stabilizing agent such as Portland cement the resulting mix is called
75. characteristic friction parameter RCR may be estimated based on soil type and classification or strength data collected to assess the structural suitability of the airfield Appendix A provides the soil test methods that should be used to determine the soil type in the field Table D 3 provides the data correlation obtained USCS Water Soil Type Classification Content C 17 RCR Well Grade Gravels GW Dry 20 Clean Sands lt 5 fines SW SP Dry 22 Clayey Sands Silty Sands SC SM Dry 22 gt 12 fines Low Plasticity Clays amp Silts CL ML Dry 23 Correlation Between Soil Type and RCR Direct Measurement Of Skid Distance In lieu of collecting skid test data with the Bowmonk AFM 2 the actual skid distance may be physically measured The following procedure can be used to measure the average braking friction of any vehicle used This provides the user with a method to determine airfield friction should a Bowmonk unit not be available or working improperly Comparison of measured skid distance converted into an average friction with the value calculated by a Bowmonk unit may also be used in the field as a method of checking the unit for proper operation Atch 1 144 of 162 25 November 1997 Stopping Distance ft 20 MPH 30 MPH 40 MPH 50 MPH 60 MPH 15 90 NA NA NA NA 20 67 NA NA NA NA 25 54 NA NA NA NA 30 45 101 NA NA NA 35 38 86 NA NA NA 40 34 76 NA NA NA 45 30 67 NA NA NA 50 27 61 NA NA NA 55 24 55 98 NA NA 60 22 50 90 NA NA
76. ches thick use the average CBR of the data taken between the 12 and 24 inch depths as the critical CBR e Soil Strength Decreases with Depth Determine the average CBRs for various 12 inch layers such as 6 to 18 inches 8 to 20 inches 10 to 22 inches and 12 to 24 inches Use the lowest average CBR of these layers as the critical CBR Atch 1 103 of 162 25 November 1997 30 TT TTT TRAFFIC PASSES 20 OEE 8 T EE eT 8 0 6 e l ee __ NUM _ A 10 20 40 60 80100 200 400 600 1000 2000 4000 TRAFFIC PASSES Semi prepared with or without membrane Light duty Mat Medium duty Mat Figure C 11 Subgrade Strength Requirements for C 17 C 7 2 AM 2 Mat Surfaced Airfields Refer to the curves and procedures in Chapter 4 Structural Design Criteria to determine suitability of AM 2 mat surfaced airfields C 8 Determine Aircraft Classification Number Pavement Classification Number ACN PCN This system is included for mission planning purposes C 8 1 In 1983 the International Civil Aviation Organization ICAO developed and adopted a standardized method of reporting pavement strength This procedure is known as the Aircraft Classification Number Pavement Classification Number ACN PCN method The ACN is a number that expresses the effect an aircraft will have on a pavement system The PCN is a number that expresses the capability of a pavement to su
77. city VAMP designed for use with aircraft that generate a maximum take off blast jet or prop greater than 200 mph This VAMP is constructed of a cerise and or orange colored 420 denier nylon fabric panel 17 inches high by 72 inches long This panel is reinforced around its entire outer edge by a two inch wide 1000 test nylon webbing that is sewn into the colored panel material Three 2 inch webbing loops are evenly spaced and sewn to each of the 17 inch sides Additionally there are two 20 inch webbing stiffeners evenly spaced along the bottom edge of the fabric panel There is a 0 3125 inch inside diameter ID brass coated steel grommet pressed into each of the two webbing stiffeners There are three vertical slits evenly spaced sewn into the panel This allows for air pressure relief while under maximum stress loads There is a 0 3125 inch inside diameter ID brass coated steel grommet pressed into each corner of the panel The panel is supported Atch 1 22 of 162 25 November 1997 and suspended by two 19 inch long by 0 500 inch outside diameter OD aluminum poles The poles are constructed of hollow aluminum tubing reinforced by a round head 0 375 inch by 2 inch carriage bolt inserted into each end of the pole The poles are inserted through the 2 inch webbing loops at each end of the panel The panel is then attached to the poles by a 0 125 inch machine crimped steel cable configuration Each corner of the 17 inch side s is a
78. cking should continue until no further densification of the material can be observed If additional passes do not increase soil strength the material is probably too dry or too wet Pumping of the material in front of the roller also indicates the material is too wet B 2 5 Equipment Sizes Sizes referenced in paragraphs B 2 2 and B 2 3 should provide adequate compaction to depths of 6 9 inches If the available compaction equipment is smaller the soil must be compacted in thinner lifts with more passes until no further densification of the material can be observed on each lift B 2 6 Repairs Passes should begin on the outside of the repair adjacent to the existing adequate surface and should proceed toward the center of the repair Passes should overlap and the equipment should crawl rather than race across the surface B 2 7 Soil Testing Where time or available equipment precludes moisture density tests to confirm compaction dynamic cone penetrometer DCP tests should be performed following compaction to determine if the material is strong enough to support aircraft operations Atch 1 79 of 162 25 November 1997 Qum co Boos o oL OD BT qe et OT COS TO 91 POTHOLES Cut to at least 2 inches below the base of the pothole and at least 2 feet around the hole Add material identical to the surrounding material This is especially important if the soil is stabilized Wet as required to o
79. ction should begin as soon as possible after mixing with cement stabilization In no case should compaction be finished later than four hours after the start of mixing of the cement mixture Roller patterns may be adjusted until the minimum number of passes results in the density required The required density should be at least 95 percent of the mix design density For lime stabilization compaction may be delayed as long as 24 hours The materials should be kept near optimum moisture content after mixing and before compaction occurs The delay in compaction allows the material to react chemically a process termed mellowing for lime stabilized materials 4 8 3 6 Curing Curing is required to maintain the moisture content and allow the hydration process to continue uninterrupted thereby allowing the stabilized material to achieve maximum strength Normally spray on membranes such as a bitumen or a curing compound may be used for curing However since the stabilized layer will be the airfield surface membranes are not recommended Sprinklers hay or burlap blankets can be used for moist curing Plastic sheeting that can be removed after the curing period may also be used The curing period should last at least seven days but curing beyond seven days will help the stabilized material develop maximum strength If sprinklers or other systems are used for wet curing the surface should be monitored to ensure that surface erosion does not occur
80. d Subgrade The upper part of the subgrade 1 3 Airfield Types The C 17 can operate on paved or semi prepared airfields and matting Paved airfields consist of conventional rigid and flexible pavements and are generally used for routine operations A semi prepared airfield refers to an unpaved airfield The amount of engineering effort required to develop a semi prepared airfield depends on the planned operation the service life needed to support these operations and the existing soil and weather conditions Semi prepared construction maintenance preparations may range from those sufficient for limited use to those required for continuous routine operations Options for surface preparation may include stabilization addition of an aggregate course compaction of in place soils or matting 1 4 Types of Operations Three types of operations are anticipated with the C 17 aircraft Visual flight rules apply for contingency and training operations e Routine operations consist of normal day to day operations conducted on paved surfaces e Contingency operations are normally short term operations connected with conflicts or emergencies Airfields for contingency operations can be paved or unpaved Since operations are limited structural requirements are not as great In addition higher risk to aircraft and personnel may be justified so requirements such as clearances are not as stringent e Training operations involve training for contingency
81. d aerial photographs would also be helpful if available C 2 1 2 Use expedient methods to survey taping measuring wheel or pacing C 2 1 3 Update existing plans or make new scaled drawing as required C 2 2 Divide the airfield pavement system into features based upon common characteristics which are the surface type thickness and construction history data available subsurface layer data use and traffic type C 2 2 1 Surface Types e AM 2 Mat e Gravel Unsurfaced e Stabilized Material Note A specific feature contains only one surface type Atch 1 83 of 162 25 November 1997 C 2 2 2 Surface Layer Thickness and Construction History Data All surface material in a specific feature must share a constant nominal thickness within reason and a common construction history Construction history is comprised of data regarding the materials used and year of original construction as well as all subsequent maintenance and repair materials and techniques C 2 2 3 Subsurface Layers e Types e Thicknesses e Strengths C 2 2 4 Use e R Runway e O Overrun e T Taxiway e A Apron C 2 2 5 Traffic Type A Channelized traffic full design weight of aircraft All areas of contingency airfields should be evaluated as A traffic C 2 3 Determine Test Locations The numbers and locations of soil strength tests and samples will vary with the type of airfield size of airfield proposed mission of the airfield number
82. d into six sections that explain this friction test procedure e Selection of skid test vehicle e Installation Operation of Bowmonk e Layout of field test locations e Performance of skid tests e Downloading Processing of skid data e Calculation of RCR Runway Condition Rating for C 17 These sections are shown graphically in Figure D 1 Atch 1 109 of 162 25 November 1997 Site Conditions Mission Select Skid Test Vehicle Equipment Suitability Truck HMMW V Quad Cycle Availability Readiness Checks Operational Checks Quick Speed Detailed Speed Peak amp Mean Friction Skid Distance Enter Header Info Unit Settings Printer Paper Battery Charger Pre Deployment In Field Pre Deployment Bowmonk Operations Layout Field Test Locations Skid Locations Required Perform Skid Testing Download Process Skid Data Calculate C 17 RCR Correlate Ground Vehicle Decel to Aircraft RCR Figure D 1 Flowchart of the Recommended Friction Procedure D 2 Select Skid Test Vehicle The first step in this friction procedure requires the collection of deceleration skid data with a decelerometer unit mounted in a ground vehicle Data was collected using the four vehicles most likely to be used to perform skid tests for C 17 deployment on contingency airfields an Air Force six pax truck a HMMWV High Mobility Multi purpose Wheeled Vehicle with a communications p
83. diu OL Poor Not suitabie_ medium to highMedium to hig Poor Notsuitabie Veymgn Hih us cH roortoverypebr Nossa medum Poortoverypopr Notsuitable Highly Organic Soils Pt Notsuitable Notsutabe verv nign GM and SM groups are divided into subdivisions d and u for roads and airfields Suffix d is used when 1428 and Pk 6 Suffix u is used when LL 28 E Subgrade Modulus Drainage Unit Dry Weight Field K Soil Types Symbol Characteristics Lb per Cu Ft CBR Lb per Cu In Gravels 110 180 25 60 amormoe Gravelly Fair to poor 130 145 40 80 300 or more NIS pervious 120 140 sew impervious 120 140 mee impervious 200 to 300 200 to 300 200 to 300 Sands and Sandy Coarse grained Soils Poor to impervious 105 130 Fairtopoor 100 125 200 to 300 eg T EM See NUES END 8 RHET WO m GM and SM groups divided into subdivisions d for roads and airfields Suffix d is used when LL lt 28 and PI lt 6 Suffix u is used when LL 28 TRECE aoe ini T SHEET HR Ax ae ER RIT Fine grained Soils Soil Characteristics Pertinent to Roads and Airfields Atch 1 153 of 162 25 November 1997 E 1 2 4 Structural Evaluation The following charts and procedures related to structural evaluation
84. e Mixing bowl and pestle Scales or balances Knife or small spatula A 2 2 Tests for Field Identification The USCS considers three soil properties the percentage of gravel sand or fines the shape of the grain size distribution curve and the plasticity The purpose of field tests is to get the best possible identification and classification in the field Tests appropriate to a given soil sample should be made When a simple visual examination will define the soil type only the tests needed to verify this are necessary When results from a test are inconclusive some of the similar tests should be tried to establish the best identification A 2 2 1 Visual Examination This test should establish the color grain sizes grain shapes of the coarse grained portion approximate gradation and some properties of the undisturbed soil A 2 2 1 1 Color Color helps in distinguishing between soil types and aids in identifying soil types It may also indicate the presence of certain chemicals minerals or impurities Color often varies with moisture content Thus the moisture content at the time of identification should be included Colors generally become darker as the moisture content increases and lighter as the soil dries Some fine grained soil OH OL with dark drab shades of brown or gray including almost black contain organic material In contrast clean bright shades of gray olive green brown red yellow and white are associated
85. e 7 feet 9 inches Bottom of inboard engine 8 feet 11 inches Lowest point on fuselage main gear pod 12 inches Landing Gear Dimensions The main landing gear consists of dual struts on each side of the aircraft with three wheels on each strut The nose gear consists of a single strut with two wheels Dimensions are shown below and in Figure 2 2 Distance between nose gear tires 2 feet 5 inches center to center Center of nose gear to center of main gear 62 feet 2 inches Tread 33 feet 8 inches Distance between main gear tires varies see Figure 2 2 Aircraft Weights Maximum gross weight on paved surfaces 586 000 pounds Maximum contingency operating weight on semi prepared surfaces 447 000 pounds Maximum operating weight on matting 560 000 pounds Operating weight 279 000 pounds Landing Gear Static Loads Percent load on each main gear strut 23 96 Percent load on nose gear 8 Main Gear Characteristics Contact Area Weight Strut Wheel Contact Tire Width Kips Load Kips Load Kips Area Sq In Pressure psi In 586 134 8 44 9 320 138 15 7 560 128 8 42 9 310 138 15 5 447 102 8 34 3 250 138 13 9 279 64 2 21 4 155 138 9 8 Nose Gear Characteristics Contact Area Weight Strut Wheel Contact Tire Width Kips Load Kips Load Kips Area Sq In Pressure psi In 586 46 9 23 4 150 155 10 7 560 44 8 22 4 145 155 10 6 447 35 8 17 9 115 155 9 4 279 22 3 11 2 72 155 7 5 Atch 1 6 of 162 25 November 1997 1
86. e Max 5 0 90 280 1 5 3 0 10 1 5 5 0 100 162 of 162 25 November 1997 E 1 4 Annex A appendix 2 3 Airfield Layout should be updated to reflect a more detailed airfield drawing DESIRED APPROACH ZONE REQUIRED APPROACH ZONE ACCIDENT POTENTIAL ZONE 3NDZ OVERRUN TAXLWAY AIRCRAFT TURNAROUND LATERAL SAFETY ZONE LATERAL CLEAR AREA LATERAL SAFETY ZUNE TAXIVAY CLEAR AREA TAXIWAY CLEAR AREA SHDULDER SHOULDER YZ Atch 1 163 of 162 25 November 1997
87. e a good indication of the surface capability to withstand the additional loads and stresses expected during landing operations C 3 3 1 4 Depth of Tests The C 17 aircraft may affect the soil to depths of 36 inches or more therefore it is recommended that DCP tests be conducted to the full depth of the rod If a test must be discontinued short of full rod depth a new test should be accomplished nearby C 3 3 1 5 Correlation of DCP Readings to CBR e If using the U S Army Corps of Engineers Waterways Experiment Station developed DCP software program the CBRs are computed for the user based upon the number of blows and penetration depths inputted The DCP program will also display a graph of the CBR values in relation to the depths measured and is useful in determining layer thicknesses See Figure C 5 If using manual field plotting methods the CBRs may be obtained from Tables C 2 and C 3 or Figure C 6 Table C 2 correlations should be used for all soil groups other than CH and CL with a CBR below 10 Table C 3 correlations should be used for all CH soils and for CL soils with a CBR less than 10 When using these tables CBRs should be rounded to the nearest whole number Figure C 6 shows a plot of all correlations The DCP data may also be easily plotted on graph paper and the resulting soil layer thicknesses and corresponding CBRs may be determined Figure C 7 is an example of this method Atch 1 89 of 162 25 November 1997
88. e acceptable save the test results by pressing A to accept this test The unit will now display ARM2 READY If the result is not acceptable press the RESET button the instrument will discard the current test and display AFM2 READY Another test can be performed and saved with the same test number Ready vehicle for next test and repeat from step 2 to perform subsequent tests Continue until desire number of friction tests are completed The Bowmonk device will automatically shut down after 4 minutes of inactivity to save the battery To turn it back on simply hit the RESET button Print out Bowmonk data and or download to computer Atch 1 143 of 162 25 November 1997 Stopping Friction Guidance Preliminary HUMVEE Semi prepared Surface Condition Bowmonk Runway Reading RCR o at40mph Unstabilized Visibly dry dry depth 2 gt 61 20 Cement Stabilized Visibly dry no puddles gt 61 20 Either Damp to wet N A 4 Note Average of all eight mean decel in g readings Alternate Friction Prediction Procedures There are two alternate friction prediction procedures correlating the soil type to RCR and directly measuring the skid distance with a ground vehicle and correlating to RCR Neither method has as much accuracy as the Bowmonk Decel method but can be used to obtain the RCR Correlation with Soil Type Classification In lieu of collecting any actual skid test data on the airfield surface the
89. e borderline cases and should be given dual symbols for example CL ML A 1 5 Highly Organic Soils A special classification Pt is reserved for the highly organic soils such as peat which have many characteristics undesirable for use as foundations and construction materials No laboratory criteria are established for these Atch 1 47 of 162 25 November 1997 soils as they can be identified in the field by their distinctive color odor spongy feel and fibrous textures Particles of leaves grass branches or other fibrous vegetable matter are common components of these soils A 2 Field Identification of Soil Lack of time and facilities often make laboratory testing impossible in contingency evaluations Even where laboratory tests are to follow field identification tests can reduce the number of laboratory test samples required In expedient evaluations where the DCP is the primary instrument used to determine soil strength proper identification of soil type is required to determine the correct correlation factor to be used in computing CBRs The correlations for CL and CH soils vary significantly from other materials see Tables C 2 and C 3 and Figure C 6 in Appendix C Experience is the greatest asset in field identification and this is gained by getting the feel of soils during laboratory testing If expedient field tests to identify clay soils are inconclusive testing should be conducted using laboratory Atterberg limits equ
90. e bottom of the rut Use the maximum depth of the six measurements for that location Rut width does not affect severity GREEN Wheel Paths Less than 4 inches Ruts exist but are less than 4 inches deep 4 9 inches Y Ruts are 4 9 inches deep Greater than 9 inches Y Ruts are deeper than 9 inches Atch 1 60 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Airfield Lake pue 7 2 97 Section 27 80 AO too Inspector _ Jim Greene _ SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY et te tate IRIS v UE SPACI CALCULATIONS Distress Deduct Type Severity Value NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Ruts Green Severity Atch 1 61 of 162 25 November 1997 93 LOOSE AGGREGATE DEFINITION Loose aggregate consists of small stones 14 inch or larger that have separated from the soil binder In large enough quantities and sizes it becomes dangerous Rocks over 4 inches in diameter must be removed from the airfield before any operations If material crushes underfoot it is not considered loose aggregate HOW TO MEASURE Estimate the area of the section that is covered by loose aggregate and check the appropriate
91. e investigation data and Table 4 1 it is determined that the subgrade is in the F3 Frost Group The next step is to determine the Frost Area Soil Support Index FASSI for the subgrade Using Table 4 2 the FASSI for an F3 material is 3 5 Step 4 Since the FASSI is less than the in place subgrade CBR 3 5 10 then the FASSI must be used in lieu of the in place CBR for determining soil strength and thickness requirements Enter Figure 4 1 with the design passes 100 and the gross aircraft weight 447 kips to determine the subgrade surface CBR required to support the design mission traffic Following the steps in Example 1 Step 3 it is determined that a minimum surface CBR of 12 is required to support 100 passes of a 447 kip C 17 Atch 1 42 of 162 25 November 1997 Step 5 Since the minimum required surface CBR is greater than the in place subgrade CBR for frost design 12 3 5 the subgrade requires structural improvement to withstand the design traffic Using Figure 4 2 enter the chart with an in place subgrade CBR of 3 5 to determine the thickness of 12 CBR material required above the subgrade to support the design traffic Following the guidance in Example 1 Step 4 it is determined that 15 inches of 12 CBR material is required above the 3 5 CBR frost subgrade At this point an analysis of available construction materials would determine whether 15 inches of an 12 CBR non frost susceptible material would be plausible If no
92. e stumps and loose rocks 4 Longitudinal Maximum 3 096 Hold to minimum practicable Grade Grades may be both positive and negative 5 Rate of Maximum 2 0 per 30 meters 100 feet The minimum distance between two Longitudinal successive points of intersection is Grade Change 60 meters 200 feet Changes are to be accomplished by means of a vertical curve Transverse 0 5 to 3 0 Transverse grades are to slope down Grade of from the taxiway centerline The intent of Taxiway the transverse grade limitation is to provide adequate cross slope to facilitate drainage without adversely affecting aircraft operations The surfaces should slope so that the centerline of the taxiway is crowned 7 Transverse 1 5 to 5 0 Aircraft are not permitted to use Grade of shoulders on AM 2 airfields due to Taxiway horizontal and vertical load devices Shoulder connected to the mat edges Runway 85 5 m 280 ft Measured from the runway centerline to Clearance near edge of the taxiway Clearance to 33 5 m 110 ft Measured from the taxiway centerline Fixed or Mobile Obstacles 10 Taxiway Clear 21 5 m 70 ft Remove or embed rocks larger than 6 Area Width inches in diameter Cut tree stumps brush and other vegetation excluding grass to within 6 inches of the ground 11 Taxiway Clear Maximum 5 0 Transverse grades may slope up or down Area Grade to provide drainage ditches Centerline of drainage ditches must be established away fr
93. e subgrade and construction materials can be determined in terms of the California Bearing Ratio CBR by using the laboratory CBR test airfield cone penetrometer trafficability penetrometer or the Dynamic Cone Penetrometer DCP The soil strengths in terms of CBR can be determined based upon procedures outlined in Chapter 5 FM 5 430 00 1 AFPAM 32 8013 Vol 1 A preliminary site investigation is essential in order to properly design contingency airfields The procedure for conducting site evaluations is provided in Appendix C of this document 4 9 6 Frost Conditions Frost action can cause subgrade strengths to be reduced significantly during thaw periods Detrimental frost action will occur if the subgrade contains frost susceptible materials the temperature remains below freezing for a considerable amount of time and an ample supply of ground water exists If the subgrade is frost susceptible determine its frost group from Table 4 5 below FM 5 430 00 1 AFPAM 32 8013 Vol 1 Atch 1 30 of 162 25 November 1997 Table 4 5 Frost Group Designations for Frost Design based on Soil Classification b Frost Weight Typical Soil Types eh Type of Soil lt 0 02 mm under the USCS Gravels e gt 0 25 Sons Crushed Rock b Sands e 0 30 Sands e gt 0 30 a Gravels e 0 25 Crushed Stone Crushed Rock b Gravelly soils GW GP GW GM GP GM GW GG and GP GC Sandy soils e 0 30 SW SP SW SM SP SM SW
94. e use of an AM 2 mat surfacing may be a plausible solution For satisfactory performance the landing mat must be supported by the subgrade and must not be required to bridge over depressions To determine if the subgrade is capable of supporting an AM 2 surfaced airfield the minimum required subgrade CBR must be determined from Figure 4 3 and compared to the in place subgrade CBR Enter Figure 4 3 at the bottom with the required number of aircraft passes and draw a vertical line to the intersection of the appropriate design gross weight curve Then draw a horizontal line to the vertical axis to determine the minimum required subgrade CBR Now that the required subgrade CBR has been determined it is necessary to check the subgrade thickness requirements Use Atch 1 33 of 162 25 November 1997 CBR 1 2 3 4 5 6 7 8 910 20 30 40 50 60 70 8090 S Sos i S Ten Y ee A 1 2 3 4 5 6 7 8 910 20 30 40 50 60 70 8090 Thickness inches Figure 4 2 Aggregate or Select Fill Surface Thickness Requirements for the C 17 Aircraft Figures 4 4 through 4 8 to find the thickness of the subgrade that is required at the predetermined soil strength from Figure 4 3 for different design gross weights of the aircraft Use the in place subgrade CBR when using Figures 4 4 through 4 8 to determine the minimum thickness requirements F
95. ection 1 Introduction 1 1 References e FM 5 430 00 01 02 AFJPAM 32 8013 Volumes and II Planning and Design of Roads Airfields and Heliports in the Theater of Operations El 02C013 TM 5 803 7 AFJMAN 32 1013 Airfield and Heliport Planning and Design e Pavement Transportation Computer Aided Structural Engineering PCASE design and evaluation computer programs Dynamic Cone Penetrometer DCP program is used to plot DCP data and establish soil layer thicknesses and strengths Unsurfaced Design UNSURF program is used to aid in design of semi prepared airfields Unsurfaced Evaluation UNSEVA program is used to determine aircraft allowable gross weights and or passes based upon layer structures established with the DCP e Airfield Friction Meter MK2 Operating Instructions Rev 3 1x Issue 3 Bowmonk Ltd Norwich England 1995 PCASE programs are available on the World Wide WEB WWW at http pavement wes army mil pcase html For access open a Uniform Resource Listing Locator URL to the address which will jump to the PCASE homepage for computer program access For File Transfer Protocol FTP Anonymous Network Access FTP to pavement wes army mil using anonymous as the log in name and pcase as the password Change directory to pub cd pub and look at directory contents 15 Change transfer type to binary binary and then use the get command to retrieve any file you wish For example if you wish
96. ed under more than one runway id The UP ARROW and DOWN ARROW can be used to select runway id to print Press ENTER once this will print a results summary stripchart report that shows the test number the calculated velocity at braking and the peak friction results for all tests performed Remove stripchart printout label with additional information if necessary vehicle driver test conditions and store in an appropriate place Atch 1 118 of 162 25 November 1997 AIRFIELD FRICTION Test Friction Time Speed 1g t a La C4 C4 BUSS eer SBSESE9R9R0R SSJESSVNN OS d C4 6 Ose 5 6 9 62 62 amp 68 65 57 58 62 66 66 72 70 65 Test 18 carried out 20 59 on 13 fPR 97 Serial Mot 11038 Next Cal 10 FEB 9 Software Rev W312 Turnkey Instruments Figure D 7 Example Stripchart Print Out After the results summary is finished printing it is possible to print out a more detailed results table An example of this table is shown in Figure D 8 Note that the results table will show both the mean and peak friction time to stop brake delay time speed and stopping distance for each test Atch 1 119 of 162 25 November 1997 RUNWAY FRICTION Mean Deceleration 66 g MAX over 0 20sec 78 g AIRFIELD FRICTION TIME TO STOP 1 41 sec SPEED AT BRAKING 23 5 miles hour STOPPING DISTANCES 21 3 feet Test Friction Time
97. eliports in the Theater of Operations The introduction of the C 17 resulted in the requirement to validate existing design criteria or develop new criteria for contingency operations on semi prepared runways Semi prepared airfields include unsurfaced aggregate surfaced and matted airfields The criteria presented provides guidance for designing unsurfaced aggregate surfaced and AM 2 mat surfaced airfields for the operation of the C 17 aircraft 4 2 Site Investigation The site investigation for input to the structural design of a semi prepared airfield is required to determine the in place material properties and the properties of the materials that are available for use in constructing a contingency airfield If an existing airfield is to be used the evaluation portion of this document Appendix C should be used for investigating the capability of the airfield to support C 17 aircraft operations If an existing airfield is not capable of supporting operations of the C 17 aircraft the airfield will need to be upgraded or repairs and maintenance will be required periodically during the mission If it is determined that an existing airfield will be upgraded the design portion of this document should be used and the material characteristics of the existing airfield and available materials for upgrading will be required for input to the design procedure Knowledge of the current field condition at a site to be used for a contingency airfield is impor
98. eristics Pertinent to Airfields Atch 1 45 of 162 25 November 1997 A 1 1 Categories In the USCS all soils are divided into three major categories coarse grained fine grained and peat The first two are differentiated by grain size whereas the third is identified by the presence of large amounts of organic material A 1 2 Groups Each of the major categories is further subdivided into groups and a letter symbol is assigned to each group Soil Groups Symbol Gravel G Sand S Silt M Clay C Soil Characteristics Symbol Well graded W Poorly graded P High compressibility H Low compressibility L Organic peat Pt Organic silts and clays O Liquid limits under 50 L Liquid limits over 50 H A 1 3 Coarse Grained Soils Coarse grained soils are defined as those in which at least half the material by weight is larger than a No 200 sieve They are divided into two major divisions gravels and sands A coarse grained soil is classified as a gravel if more than half the coarse fraction by weight is larger than a No 4 sieve It is a sand if more than half the coarse fraction by weight is smaller than a No 4 sieve A 1 3 1 Coarse Grained Soils with Less Than Five Percent Nonplastic Fines The first letter of the symbol indicates a gravel or sand The second letter is determined by the grain size distribution curve e GW Well graded gravels or gravel sand mixtures e GP Poorly graded gravels or gravel sand mixtures e SW Well graded
99. f Remove all tree stumps and loose rocks in shoulder Shoulders 10 ft areas Shoulders should be stabilized to prevent erosion by jet blast Where adequate sod cover cannot be established the shoulders should be chemically stabilized Longitudinal Maximum 396 Hold to minimum practicable Grades of Grades may be both positive and negative but must not exceed the limit specified Shoulders Longitudinal Max 1 596 per 60 m 200 ft Longitudinal grade changes cannot occur within 150 m Runway 500 feet of runway ends Grade Minimum distance between grade changes is 122 m 400 Change ft Transverse 0 5 3 0 Transverse grades should slope down from the runway Grade of centerline The intent of the transverse grade limit is to Semi provide adequate cross slope to facilitate drainage Prepared without adversely affecting aircraft operations Runway Transverse 1 596 Minimum Grade of to Runway 5 096 Maximum Shoulder Lateral 10 5 m Remove or embed rocks larger than 6 inches in Clear Area 35 ft diameter Cut tree stumps to within 6 inches of the ground Remove vegetation excluding grass to within 6 inches of ground Transverse 2 096 Minimum Grades may slope up or down to provide drainage Grade of to Exception Essential drainage ditches may be sloped up Lateral 5 0 Maximum to 1096 in the primary surface area and clear zones Do Clear Area not locate these ditches within 27 5 meters 90 feet of the runway centerline Such ditches should be e
100. f the fines exceed 50 percent the soil is considered fine grained M C or O If the coarse material exceeds 50 percent the soil is coarse grained G or S Examine coarse grained soil for gradation of the particle sizes from the largest to the smallest A good distribution of all sizes means the soil is well graded W Overabundance or lack of any size means the material is poorly graded P Estimate the percentage of the fine grained portion of the of the coarse grained soil for further classification Fine grained soils and fine grained portions of coarse grained soils require other tests for identification A 2 2 1 5 Undisturbed Soil Properties Characteristics of the soil in the undisturbed state may be helpful in identification The compactness of gravels or sands may be loose medium or dense Clays may be hard stiff or soft The ease or difficulty of sample removal should be recorded The moisture content of the soil influences the in place characteristics It is helpful to know the weather just prior to and during the field evaluation to determine how the soil has or will react to weather changes The presence of decayed roots leaves grasses and other vegetable matter in organic soils produces soil which is usually dark when moist having a soft spongy feel and a distinctive odor of rotting organic matter The odor may be musky and slightly offensive The odor is especially apparent in undisturbed conditions or in fresh samples lt
101. for 17 6 Ib hammer 2 for 10 1 Ib hammer 6 4 x S 7 From CBR versus DCP correlation table C 2 or C 3 8 Previous entry in 2 divided by 25 4 rounded off to 0 2 in Figure C 4 DCP Data Sheet C 3 3 1 3 Surface Layer Strengths Lack of confinement at the top of the surface layer affects the DCP measurements The penetration depth required to measure the surface layer strength accurately is related to the gradation and plasticity characteristics of the materials The DCP can measure strengths of thin surface layers of fine grained plastic materials but requires thicker surface layers for the non plastic coarse grained materials The penetration depth required for measuring actual Atch 1 88 of 162 25 November 1997 strength of the surface layer with the DCP is shown in Table C 1 for the various soil types Table C 1 Depth Required to Measure Surface Layer Strength No Overburden Average rend e Soil Type _ inches CH 1 CL 3 SC 4 SW SM 4 SM 5 GP 5 SP 11 Note The shearing action of the C 17 while braking during landing operations will create loose till on dry unstabilized soil surfaced runways in arid or semi arid regions The number of allowable passes may be significantly lower than those predicted using standard evaluation procedures The DCP data collected at the top of the surface layer in the unconfined material if treated as a separate layer in calculating allowable loads or passes may provid
102. g 16 tests To perform this larger number of tests conduct the procedure described in Section D 4 2 1 twice reversing direction on the second set This insures that an even number of tests are conducted in either direction This helps to compensate for the effects of the wind on the friction measurements D 4 1 3 High Confidence Level The most accurate results will be achieved if the evaluator has the time to perform 24 or more skid tests The driver repeats the two test patterns shown in Figure D 9 reversing direction after each subset of 8 tests until the total number of tests reaches the desired number With the test pattern shown 24 or 32 tests can easily be performed It is unnecessary to collect more than 32 tests D 5 Perform Skid Testing The following section lists the general steps required to perform one friction test at one skid location Any of the following items in bold are extremely important and must be followed for the test to be accurate Atch 1 133 of 162 25 November 1997 1 Align test vehicle with runway on one of the two longitudinal test lines shown in Figure D 9 Both vehicle and tires should be straight 2 Arm Bowmonk unit for test Device should be armed just prior to vehicle acceleration If unit is armed and a delay of more than 15 seconds occurs unit should be reset and then rearmed 3 Begin vehicle acceleration smoothly but quickly Acceleration should be uniform without spinning tires or excessive
103. g Ground Temp 83 84 78 Runway ID Examiner Signature 1st 1 3 average 2nd 1 3 average 3rd 1 3 average RUNWAY FRICTION Overall Average Mean Deceleration 71 g Ground Temp MAX over 0 20 sec 83 g TIME TO STOP 1 32 sec SPEED AT BRAKING 20 8 miles hour STOPPING DISTANCES 19 5 feet Runway ID Examiner ignat Signature Ground Temp Test 3 carried out 15 58 on 26 JUN 97 Serial No 11039 Next Cal 10 FEB 98 Software Rev W3 12 Turnkey Instruments Runway ID Examiner Signature a Results Summary RUNWAY FRICTION Mean Deceleration 68 g MAX over 0 20 sec 83 g TIME TO STOP 1 22 sec SPEED AT BRAKING 18 4 miles hour STOPPING DISTANCES 15 8 feet Ground Temp Runway ID Examiner Signature Test 1 carried out 15 57 on 26 JUN 97 Serial No 11039 Next Cal 10 FEB 98 Software Rev W3 12 Turnkey Instruments b Results Table Figure D 8 Example Printouts of Friction Results Atch 1 120 of 162 25 November 1997 To print out a results table continue with the following steps Press PRINT for a second time Use UP ARROW or DOWN ARROW to select test number to print Press ENTER to start printing a results table for that test number All the tests stored in the unit can also be printed The following steps can be used to print the results tables from the test number indicated on the unit up to the last test carried out Unit will display PRI
104. gth RCR feet feet 20 0 6 000 3 500 16 0 2 000 3 500 2 001 5 000 4 000 5 001 6 000 4 500 12 0 2 000 4 000 2 001 5 000 4 500 5 001 6 000 5 000 8 0 3 000 5 000 3 001 5 000 5 500 5 001 6 000 6 000 4 0 2 000 6 000 2 001 4 000 6 500 4 001 6 000 7 000 Note The runway lengths do not include under overruns 3 2 2 Width The widths of these landing surfaces must be sufficient to protect the aircraft landing gear and the engines Table 3 1 provides the minimum runway width 3 2 3 Longitudinal Gradients of Operational Surfaces Gradient constraints are based upon reverse aircraft operations conducted on hard surfaces Caution should be used when backing aircraft on soft soil conditions at any gradient 3 2 4 Shoulders Shoulders are graded and cleared of obstacles and slope downward away from the runway where practical to facilitate drainage Atch 1 11 of 162 25 November 1997 Table 3 1 Runways for C 17 Contingency Airfields Contingency Item Item Airfield Description Semi Prepared and AM 2 Remarks No 1 Length Minimum Runway length of 3 500 ft required for locations between 1 067 m sea level and 6 000 ft pressure altitude based upon an 3 500 ft RCR of 20 an ambient temperature of Standard 1962 2 See Remarks 31 F and landing gross weight of 447 000 lbs See paragraph 3 2 1 for runway requirements based upon different RCRs Width 27 5 See Note 1 90 ft 3 Width o
105. h requirements for mat surfaced airfields Enter the left side of the chart with the measured CBR Follow horizontally to the curve indicating the surface condition unsurfaced light duty mat or medium duty mat and aircraft gross weight Then read downward to determine the allowable aircraft cycles One cycle is equal to one take off and one landing AM 2 is considered medium duty mat C 7 1 2 5 The Subgrade Strength Chart is limited to one CBR input so care must be given to ensure that the chosen CBR value is truly representative This is not difficult for a soil that exhibits a uniform CBR and soil characteristics to a depth of 24 inches If the soil strength varies through this depth the evaluation must be made using the critical CBR of the soil e Soil Strength Increases with Depth Use the average CBR for the top 12 inches as the critical CBR e Very Soft Layer over Hard Layer If soft layer is 4 inches thick or less discard the soft layer CBR values Use the average CBR for the 12 inch layer under the soft layer as the critical CBR f the soft layer is more than 4 inches thick the soft layer should be reduced by grading to less than 4 inches If this can not be done use the average CBR for the top 12 inches as the critical CBR e Hard Layer over Soft Layer f the hard layer is less than 12 inches thick use the average CBR of the 12 inch layer under the hard layer as the critical CBR f the hard layer is more than 12 in
106. h skid tests are performed are representative of the runway surface that the aircraft itself will use for braking D 4 1 1 Runup Lengths and Stopping Distances There are required runup lengths for the test vehicles The evaluator should think through the recommended test sequence and pattern after arriving on site and carefully plan the skid test locations to achieve maximum data collection efficiency and avoid aborted test runs due to inadequate runup distance between skid locations Assuming test speeds of 40 mph for all vehicles Table D 5 is provided Table D 5 Required Runup Distances at 40 mph Runup Skid Length Maximum Required Vehicle Required Stopping Distance ft HMMWV 1400 300 Truck 1200 250 Quad 1000 175 Cycle 700 125 Atch 1 131 of 162 25 November 1997 uJ9jjed pue suomne 2oT S3L PINS eq Jaquiny 9pIQ9A PLS uod 193 L yed PIM pue uone mns3ruo IPA JO PHIS pue uns Jo puooes asvyg q uod 1oqunw 3S9 uny uuum JO asat sey v I p uonoog uonoog c uonoog uonoog UNJIOA THI Ks OK _ Atch 1 132 of 162 25 November 1997 Note that if the approach ends of the runway provide extra runup room in addition to the 500 foot overruns they can be used if they allow for smooth uniform acceleration Overruns can be used for vehicle acceleration but should not be used for s
107. have been developed to determine the cohesive and plastic characteristics of soil These field tests are performed only on material passing the No 40 sieve the same fraction used in the laboratory tests A 2 2 3 1 Breaking or Dry Strength Test A 2 2 3 1 1 Pat Test e Procedure Prepare a pat of soil about 2 inches in diameter and 1 2 inch thick by molding it in a wet plastic state Allow the pat to dry completely in the sun in an oven or inside the engine compartment then grasp the pat between the thumbs and forefingers of both hands and attempt to break it If the pat breaks try to powder it by rubbing it between the thumb and forefinger of one hand e Results Pat cannot be broken nor powdered by finger pressure Very highly plastic soil CH Atch 1 51 of 162 25 November 1997 Pat can be broken with great effort but cannot be powdered Highly plastic soil CL Pat can be broken and powdered but with some effort Medium plastic soil CL Pat breaks easily and powders readily Slightly plastic soil ML MH or CL Pat has little or no dry strength and crumbles or powders when picked up Nonplastic soil ML or MH or OL or OH Note Dry pats of highly plastic clays often display shrinkage cracks Breaking the pat along such a crack may not give a true indication of the strength It is important to distinguish between a break along such a crack and a clean fresh break that indicates the
108. he battery To turn it back on simply press RESET testing can then continue To check the amount of memory used and the battery condition press and hold RESET once unit is on and displaying AFM2 READY Release RESET to return to normal on state This is recommended if large numbers of tests are conducted or battery is suspected to be low Print out and or download data if memory approaches full or battery level becomes low to avoid a loss of data D 3 3 2 Printing Test Results After completion of the friction tests the following steps are required to print out a summary of the test results A results summary printout from a series of tests is shown in Figure D 7 Note that the friction values are the peak friction measurements not mean Also note that the overall average is an average of the peak friction measurements The overall average peak friction value 6396g in Figure D 7 can be used in Table D 7 to calculate a C 17 RCR However an overall average mean friction value is highly preferable to a peak value for determining an RCR The results are more consistent and the measurement is less likely to be made incorrectly After completion acceptance of last test display will show AFM2 READY If unit has shutdown press RESET to turn unit back on Press PRINT The display will show PRINT TEST FOR RUNWAY check the instrument and make sure it shows correct RUNWAY ID Data may have inadvertently been collect
109. he contingency soils van operated by HQ AFCESA is equipped with an ECP that is hydraulically pushed through the soil layers to depths of typically five to seven feet The cone tip pressure is measured and recorded by the on board computer system and is correlated to CBR values Soil cohesion measurements are also recorded and used in conjunction with the tip pressure to assist in soil classification This one of a kind item is also equipped with a core drill capable of coring through flexible and rigid pavement layers as required is air transportable by C 130 C 141 C 5 and C 17 aircraft and provides accurate consistent data This van is not available nor appropriate for all contingency evaluations but its use should be considered when other methods of data collection do not provide clear results Field Small Aperture CBR Test Standard CBR tests may also be performed on the surface or through core holes in the pavement surface This use is normally limited to tests on the surface of the base course These tests may be performed in conjunction with DCP tests to validate the data or as stand alone tests in cases where use of the DCP is not applicable These tests are described in detail in FM 5 530 AFM 89 3 USCS Correlation This is the quickest yet least accurate method of determining CBR values For each soil type empirical studies have determined a range of CBR values These values are shown on the Table A 2 Soil Characteristics Chart in Appe
110. he in place subgrade must be structurally improved Step 6 To determine the thickness required of the 10 CBR material use the guidance in step 6 above and Figure 4 6 Entering the figure with the in place subgrade CBR 4 indicates that 22 inches of a 10 CBR is required beneath the AM 2 mat to support design traffic requirements Thus the design of the airfield includes the construction of a 22 inch select fill or aggregate layer of at least a 10 CBR to be placed on top of the 4 CBR in place subgrade The surfacing will consist of the use of AM 2 matting for all traffic areas Alternate designs incorporating various layers of differing soil strengths may be considered provided that they meet the criteria presented herein 4 11 5 Example 5 Design an airfield for contingency operations of a C 17 in an area susceptible to frost action 50 passes are expected during the spring thaw period Preliminary site investigations identified that the subgrade was classified as a low plasticity clay CL with a Plasticity Index of 15 and an in place subgrade CBR of 10 for 36 inches No taxiways will be constructed Step 1 The design aircraft is a 447 kip C 17 Step 2 The expected number of aircraft passes is 50 but the airfield will not have any taxiways so the design pass level is adjusted to 100 see Note in Example 1 Step 3 The first step in designing for frost is to determine the Frost Group to which the subgrade belongs Using the sit
111. in reason However attempts to maintain proper speed should not override other considerations described in this appendix which are required to perform testing properly D 5 1 2 Braking Procedure The correct braking procedure is to apply full braking until completely stopped For the HMMWV and six pax this means pushing on the brake pedal as hard as possible to lock up all four tires and then skidding to a complete stop For the cycle and quad it is unsafe to lock up both the front and back brakes so the procedure requires locking up the back brakes only Full braking must be used for operational testing Note Warm up test skids should be performed starting at lower test speeds and using non skid braking partial braking to confirm proper braking action and determine vehicle braking behavior at the particular airfield Atch 1 134 of 162 25 November 1997 D 5 1 3 Steering During Skids During the skids a nominal amount of steering will be required to maintain as straight a line as possible This is acceptable and will not significantly affect the test results If the vehicle twists more than 15 degrees from a longitudinal line then the test must be repeated D 6 Calculate C 17 RCR There are three ways to calculate the Runway Condition Rating RCR value required for C 17 contingency operations Convert Bowmonk Mean Deceleration readings into RCR Convert Soil Type to RCR Convert Ground Vehicle Skid Distance Meas
112. inimum area Centerline to be repaired 30 ft Min mms B 2 1 Soil Compaction In contingency situations supplemental materials may not be available to blend with or replace existing inadequately graded soils but on grade compaction of soil with suitable equipment can sometimes increase the soil stability and strength This is especially true for granular soils Improvement achieved by compaction depends upon the soil type moisture content and degree and method of compaction Different soils require different compaction equipment In general fine grained soils should be compacted with rubber tired sheepsfoot or segmented pad rollers and in some cases steel wheel rollers Vibratory rollers are well suited for coarse grained soils and for some dry fine grained soils n NC B 2 2 Cohesive Soils Cohesive soils contain enough soil fines to make the soil sensitive to changes in moisture content They include all types of clays silts and Atch 1 78 of 162 25 November 1997 clayey and silty sands and gravels such as CH CL MH ML SC SM GC and GM For a given compactive effort and method of compaction there is an optimum moisture content which results in the maximum dry density of the soil At any other moisture content the resulting soil dry density will be less for the same compactive effort Compact cohesive soils at or slightly higher than the optimum moisture content except when using a vibr
113. ions and one cement stabilized location Data on other soil types and climates are needed to assure world wide capability for contingency situations Friction data is based on tests at a variety of locations however additional testing is needed to increase confidence NOTE This ETL will be revised as additional data becomes available Users should reference all subsequent changes to this ETL to obtain current guidance APPROVED FOR PUBLIC RELEASE DISTRIBUTION UNLIMITED 25 November 1997 4 Contacts Mr Jim Greene DSN 523 6334 commercial 850 283 6334 or Mr Dick Smith DSN 523 6084 commercial 850 283 6084 William G Schauz Colonel USAF 2 Atch Director of Technical Support 1 Criteria for Design Maintenance and Evaluation of Semi Prepared Airfields for Contingency Operations of the C 17 Aircraft 2 Distribution List 25 November 1997 Criteria for Design Maintenance and Evaluation of Semi Prepared Airfields for Contingency Operations of the C 17 Aircraft Atch 1 1 of 162 25 November 1997 Contents Section 1 Introduction 2 Aircraft Characteristics 3 Dimensional Criteria 4 Structural Design Criteria Appendixes A Classification and Field Identification of Soils B Condition Survey and Maintenance Procedures C Structural Evaluation Procedures for Contingency Operations D Friction Test Procedures for Contingency Operations E Landing Zone Checklist Atch 1 2 of 162 25 November 1997 S
114. ipment and procedures Figure A 1 outlines a step by step procedure to field classify soil TEST FOR NM ORGANIC FINES SELECT REPRESENTATIVE SAMPLE OF SOIL 1 PINT CE 2 SHINE TEST e PEKO THREAD TEST N GRAVEL lt 50 ER em ESTIMATE SEPARATE PARTICLES SHAKING TEST El D 1 8 OR LARGER GRAVEL ESTIMATE THREAD E Ls EINESTM RIBBON TEST ENTIRE SAMPLE WASH x GRAVEL gt 50 SEDIMENTATION mum 0 SMEAR TEST OF SAMPLE DUST TEST CHECK 7 sw GRADATIO Xe CHECK GRADATION we A 2 1 Equipment Required Field tests may be performed with little or no equipment other than a small amount of water However accuracy and uniformity of results will be increased by the proper use of available equipment The following is a suggested list Atch 1 48 of 162 Figure A 1 Field Identification Procedures 25 November 1997 e Sieves No 40 All tests used to identify the fine grained portions of any soil are performed on the portion of the material which passes the No 40 sieve If this sieve is not available a rough separation may be made by spreading the material on a flat surface and removing the gravel and larger sand particles No 4 This sieve defines the limit between gravels and sands No 200 This sieve defines the limit between sands and fines The sedimentation test may also be used to separate the sands and fines This test requires a transparent cup or jar Pan and oven or other heating devic
115. is less pronounced as the sample is exposed to air The odor can be made stronger by heating a wet sample A 2 2 2 Sedimentation Test From visual examination it is relatively easy to approximate the proportions of gravels and sands in a soil sample Determining the proportion of fine grained particles is more difficult but just as important In the laboratory and in some field testing situations the fines may be separated from the sample using the No 200 sieve The sedimentation test provides an alternate field method to separate fines from the sand particles in a soil sample e Smaller particles will settle through water at a slower rate than large particles Placing a small amount of the fine fraction of a soil such as a heaping teaspoon in a transparent cup or jar covering it with about 5 inches of water and agitating it by stirring or shaking will completely suspend the soil in water With cohesive soils it will be necessary to break up all lumps of soil before adding the water After the soil particles have been dispersed in the water and then left they will start to settle to the bottom beginning with the larger sized particles in time periods indicated in Table A 3 Atch 1 50 of 162 25 November 1997 Table A 3 Sedimentation Test Approximate Time of Settlement Grain Diameter in 5 Inches of Water millimeters Differentiates 2 Seconds 0 4 Coarse Sand Fine Sand 30 Seconds 0 072 No 200 Sieve Sand Fines 10 Minutes 0
116. is procedure is not critical to contingency airfield operations but it does preserve the data collected in more detail and allow for a more in depth analysis of the data later if necessary Field computer must meet these minimum requirements 3865 processor at least 4 MB of RAM a hard disk with at least 4 MB of free space one RS232 serial port VGA or SVGA screen a mouse and Microsoft Windows 3 1 or later The manufacturer supplied program AFM2 for Windows must also be installed on the field computer Note that only the software and Bowmonk units purchased together are compatible due to the encoding of serial numbers on the units and software Units and software purchased separately will not work Attach manufacturer supplied download cable to both Bowmonk and RS232 serial port of computer Press RESET on Bowmonk to turn on if not already on Press and hold RESET Atch 1 121 of 162 25 November 1997 Unit will display battery voltage and percent memory used If percent memory used is greater than 9596 then unit should not be downloaded doing so will cause software to crash and will corrupt computer database resulting in loss of data and requiring re installation of software f data in Bowmonk has not been printed it should be done now in case of downloading problems f memory used was gt 95 then unit must be cleared and tests redone Start up AFM2 for Windows program in Windows on
117. ith gt 10 fines GM GC SM SC Remove all material gt 40 sieve e Perform field plasticity tests on portion lt 40 sieve to determine cohesive and plastic characteristics e Results will be as given for each test e Perform tests as required until results are conclusive Atch 1 150 of 162 25 November 1997 Field Identification of Soils Types ML MH CL CH OL OH Dry Strength no to low med to low Wet med high Roll Thread Stick med Ribbon no to 8 8 to 10 Stick cohesion cohesion Wet Shake lt 40 Sieve slow to no to ei Stick rapid andle freely handle roughly lt 40 lt 200 unpleasant smooth Sieve hine ull Wash iscolors quickly gt 5 silt Dust 0 silt Sedimentation 30 Seconds Summary of Field Plasticity Tests Results to Determine Soil Types Atch 1 151 of 162 25 November 1997 m Field Identification Procedures Major Divisions Symbol Base fractions on estimated weights Gravels lt 5 Fines Wide range in grain sizes all intermediate sizes substantially represented Predominantly one size or some intermediate sizes missing No 4 sieve gt 12 Nonplastic fines or fines with little plasticity see ML below o Fines fraction is larger than Plastic fines see CL below Es Wide range in grain sizes all intermediate sizes substantially represented sp Predominantly one size or some intermediate sizes missing E Nonplastic fines or fines with little plasticity
118. ity of each operation Atcn 1 74 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Airfield lame NW Date 4 30 77 Section 0 TSO inspector d o everence DISTRESS TYPES 9 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure REMARKS q SPACI 76 NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Atcn 1 75 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Airfield e uS Date eec M HP Inspector SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY SPACI CALCULATIONS Distress Deduct REMARKS Type Severity Value RATING Total deduct value q NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Atch 1 76 of 162 25 November 1997 Deduct Values for C 17 Operations RN Distress R T H A R T HA R T HA 91 Potholes 4 2 10 6 20 12 92 Ruts 14 4 18 6 24 10 93 Loose Aggregate 4 15 6 30 8 45 94 Dust 2 15 4 30 6 45 95 Rolling Resistant Material 18 2 22 4 26 15 96 Jet Blast Erosion 5 10 10 30 15 40 97 Stabilized Layer Fai
119. ix B in manufacturer s manual for details on editing or modifying these values Table D 3 Required Values for Trimmable Parameters Setting Required Value Tilt 2 5 degrees g Brake 10 00 Starting 00 50 secs Stopping 00 10 secs PFT Trig 20 00 N MAX over 0 20s D 3 4 2 2 2 Tilt This compensates for the forward tilt of the vehicle as it decelerates movement of the suspension Vehicles with softer suspensions require a larger tilt compensation value and conversely harder suspensions a lower tilt value The default value of 2 5 which simulates a typical car was used for all research testing D 3 4 2 2 3 Brake This is the deceleration in g of the Braking Threshold which determines the start and end of braking If the External Trigger is being used it is also the threshold for the end of the Brake Delay Time period It can be adjusted between 00 00 and 99 99 g The default value is 10 00 g D 3 4 2 2 4 Starting The time window of the deceleration must be sustained at more than the braking threshold for the braking to be determined to have started and the Brake Delay to have ended The brake start time is then taken as the beginning of this time window The time from the External Trigger to the brake start time is the Brake Delay Time The Starting Time Window can be adjusted between 00 00 sec and 02 55 sec the default value is 00 50 secs Atch 1 124 of 162 25 November 1997 D 3 4 2 2 5 Stopping The time window af
120. ized layers should only be performed when temperatures will remain above 40 F throughout construction and curing 4 8 3 1 Subgrade The subgrade which will support the stabilized material should be firm and uniform Wind rowing the in place material to be stabilized thereby exposing the subgrade allows the subgrade to be worked and any problems corrected before placing the stabilized layer The subgrade should be rolled with the largest roller available either a rubber tired or steel wheeled roller Any weak areas that yield or move excessively under the roller should be replaced with a select fill material 4 8 3 2 Pulverizing Material to be stabilized should be pulva mixed before placing the stabilizing agent Pulva mixing should be continued until the material to be stabilized passes 100 percent of the 1 inch U S Standard Sieve and 50 to 60 percent passes the No 4 U S Standard Sieve Pulverizing ensures proper mixing and reaction with all of the material If the material is not well pulverized clay balls or zones of weak unstabilized material may result in subsequent poor performance of the airfield 4 8 3 3 Mixing The material to be stabilized should be at optimum moisture content when the stabilizing agent is added The stabilizing agent should be uniformly distributed over the surface of the airfield Mixing should continue with the pulva mixer until the material is uniform in color through the depth of the layer being stabili
121. k in the severity box corresponding to the distresses you find If you don t find some distresses leave those boxes blank Refer to the Table of Deduct Values for C 17 Operations on page 77 Each distress has a deduct value for each severity level For potholes of Green severity on the runway the deduct value is 4 Record that number in the correct box on the bottom left side of the inspection sheet For ruts at Amber severity the deduct value is 18 For loose aggregate at Amber severity the deduct value is 6 For dust at Amber severity the deduct value is 4 Add all the distress values and record the total on the line labeled Total deduct value In this case the total deduct value is 32 Count the total number of distresses that have deduct values greater than 5 That is the q value Record it on the line labeled q For this example q is 2 On the SPACI curve page 77 locate the Total Deduct Value Go across the numbers on the bottom of the graph until you reach the total deduct value of 32 Go up the vertical line until it intersects with the curved line that matches your q number in this example 2 From that point follow the line across to the left to find the rating the SPACI For this example the SPACI is 77 Go to the SPACI scale page 77 which shows that 77 is in the Green range Circle this overall rating on the bottom left of the inspection sheet This is the rating for this section The rating f
122. kid testing D 4 2 Number of Tests Required Preliminary analysis of the research data has determined the number of tests required for a typical contingency airfield evaluation 4000 x90 as an example as shown in Table D 5 Times shown in Table D 6 are only approximate and can vary highly depending on vehicle type vehicle condition length of runway driver technique and data collection efficiency Table D 6 Number of Tests Required Number of Tests Confidence Level Time to Complete 8 Minimum Required 20 minutes 16 Standard 35 minutes 24 or more Desired 50 minutes or more D 4 2 1 Minimum Number of Tests The minimum number of tests required is 8 The airfield evaluator should perform these tests in the approximate locations as shown in Figure D 9 To perform this minimum number of tests the driver conducts skid tests 1 through 4 at the locations shown in Figure D 9 a The driver then conducts skid tests 5 through 8 at the locations shown in Figure D 9 b The skid locations shown within each section are just guidelines It is preferable to skid in the center of each section but if runway length or vehicle performance require skidding elsewhere that is acceptable as long as a skid remains in the appropriate section For extremely short runways the driver may back the vehicle up after a skid to allow more runup distance for the next skid D 4 1 2 Medium Confidence Level A more accurate answer will result from the evaluator performin
123. ld Tests gt AGLs Passes Define Features Classify Soils Refine Features Compute Allowable Gross Surface Type Layer Thicknesses DCP Select Representative Loads and or Passes Layer Thickness Layer Strengths DCP Profile Use Compile Physical Traffic Type Property Data PPD Determine Test Locations Assess SPACI Visual Inspection of Surface Distresses to Determine Semi prepared Airfield Condition Index SPACI Figure C 1 Evaluation Procedures Atch 1 82 of 162 25 November 1997 C 1 3 If questions arise in the field one of the following should be contacted e HQ AFCESA CESC 139 Barnes Drive Suite 1 Tyndall AFB FL 32403 5319 Mr James Greene DSN 523 6334 Comm 850 283 6334 USAF Pavements Manager Mr Richard Smith DSN 523 6084 Comm 850 283 6084 Pavements Laboratory Manager FAX DSN 523 6499 Comm 850 283 6499 e CEWES GP N Airfields and Pavements Division Geotechnical Laboratory U S Army Engineer Waterways Experiment Station 3909 Halls Ferry Road Vicksburg MS 39180 6199 Dr Albert Bush Comm 601 634 3545 or 1 800 522 6937 ext 3545 Mr Don Alexander Comm 601 634 2731 or 1 800 522 6937 ext 2731 FAX Comm 601 634 3020 C 2 Define Initial Airfield Layout C 2 1 Make an initial tour of the airfield C 2 1 1 Verify dimensions of the airfield and accuracy of existing drawings if available Existing information on the airfield such as soil boring data geological topographical and agricultural maps an
124. lure 5 15 10 25 15 35 R T runways and taxiways H A hammerheads and aprons 0 LLLLLINNNN X LL LLL LL LR Number of deduct values equal to or TT greater than 5 ITTI 140 160 180 200 Semi Prepared Airfield Condition Index SPACI SPACI Scale Atch 1 77 of 162 25 November 1997 B 2 Maintenance Procedures Maintenance on semi prepared airfields will be determined by e Equipment available e Materials available e Time available For all distresses except potholes the BEST procedure is to rework or reconstruct the entire distressed area from runway shoulder to runway shoulder The MINIMUM requirement is to rework or reconstruct from the outside of the main landing gear path across the runway centerline to outside the opposite main landing gear path outside of distressed area to outside of distressed area minimum of 30 feet both sides of the centerline to include all of the distressed area If this course of action is selected scarify diagonally to the direction of travel of the landing gear This will help to distribute the load across the repair area Doing just the minimum can create areas of different compaction and density which may adversely affect C 17 landings and takeoffs RECOMMEND MAINTENANCE BE PERFORMED ACROSS THE ENTIRE RUNWAY IN THE AREA OF DISTRESS Runway Desired area of repairs 90 ft across antre ey 30 ft Min M
125. me settings cannot be modified or even checked without the password Anyone using the password to check or modify settings should use caution and document any setting numbers before and after any changes The manufacture s user manual should also be consulted If the correct password is given to the Configuration Prompt in the Editing Mode the following menus appear a Advanced Setup b Trim Parameters C Trim Zeros d Adjust Clock e Re Calibrate Atch 1 123 of 162 25 November 1997 These menus allow the setup of the instrument to be changed Use UP ARROW or DOWN ARROW to move between the menus and press ENTER to select These settings might have to be re entered if the unit experiences a power loss A brief description of each follows D 3 4 2 2 Advanced Setup This option allows the user to turn various Bowmonk unit settings ON or OFF See appendix A in the manufacturer s manual Bowmonk Airfield Friction Meter MK2 Operating Instructions for details on selecting desired settings D 3 4 2 2 1 Trimmable Parameters Bowmonk Default Settings Required Probably the most significant of these menus is the Trim Parameters menu These are the configuration settings that were used for the research testing All the correlations in this appendix are based upon results obtained using the BOWMONK with these settings Therefore the Bowmonk unit must be set with these defaults The following sections describe these settings See append
126. ment rack Cycle On rear equipment rack D 3 3 1 Bowmonk Operational Instructions The following sections detail the operation and use of the Bowmonk during skid testing The emphasis in these sections is on the procedures required to operate the unit Detailed instructions on entering heading information changing unit settings and testing the unit for correct operation are given in the following sections The manufacturer s documentation should be referred to for proper charging procedures maintenance of the stripchart printer and the installation and use of available software The following steps detail the actions required to perform a test Words in all uppercase are what the unit shows on the LCD display Words in all uppercase and surrounded by brackets represent control panel keys Turn unit on by pressing RESET letting unit go through self check Unit will display AFM2 READY once self check is complete Press A to arm for first friction test Check to be sure display shows ARM FOR TEST 1 on first line or whatever test number is being conducted ENTER TO ACCEPT will be displayed on line two Press ENTER to ACCEPT The display will now show RUNWAY ID Press and hold ENTER until unit beeps at least twice Release ENTER button Display will show PLEASE WAIT for several seconds Then display will show ARMED FOR TEST 41 first line Second line will display SPEED 0 Accelerate smoothly until re
127. n Examiner ID is correctly input The display will now show RUNWAY ID Press ENTER again to enter the Runway ID Use the UP ARROW and DOWN ARROW to select a letter Press ENTER to accept that letter and move on to the next letter Press and hold ENTER when Runway ID is correctly input The display will show NAME OF AIRPORT Press ENTER again to enter the Name of Airport Use UP ARROW and DOWN ARROW to select a letter Press ENTER to accept that letter and move on to the next letter Press and hold ENTER when Name of Airport is correct Press the RESET The display will now read AFM2 READY D 3 4 2 1 Bowmonk Configuration Menus The following sections detail the steps necessary to access and modify important unit settings These settings should not be modified unless they differ from settings recommended in this appendix It should not be necessary to perform any of these modifications This section is included mainly to document these settings and provide a way for the user to check them should the unit not appear to be operating correctly Each Bowmonk unit comes with a manufacturer supplied password This is to prevent inadvertent changes to important unit settings which is possible without a password due to the nature of the control panel It is highly recommended that the password for the unit be documented and stored in multiple locations and accessible in the field So
128. n and taps the device using the slide hammer until the base of the cone is flush with the surface of the soil The second person or recorder then measures the distance between the cone and the surface to establish a baseline reading The operator then raises and releases the hammer The hammer must be raised to the point of touching the bottom of the handle but not lifting the rod and cone The hammer must be allowed to drop freely with its downward movement not influenced by any hand movement The operator must be careful not to exert any downward force on the handle after dropping the hammer The recorder ensures the device remains in a vertical position measures the cone penetration counts the number of hammer drops between measurements and records the data The number of blows or hammer drops between measurements is based on the rate of penetration The cone should penetrate at least 25 mm or 1 inch between measurements Both the operator and recorder should be alert to any sudden increases in cone penetration rates which indicate weaker soil layers A measurement should be recorded at that point to indicate the beginning of that layer After the DCP has been driven to the desired depth it should be extracted from the soil Atch 1 87 of 162 25 November 1997 by bumping the drop hammer against the handle The hammer must be raised in a vertical direction rather than in an arching motion or the rod may be bent or broken where it connects
129. n identified as universally acceptable for all problem situations that may be encountered Several materials have been recommended for use and are discussed in TM 5 830 3 AFM 88 17 Chapter 3 Atch 1 43 of 162 25 November 1997 APPENDIX A Classification and Field Identification of Soils A 1 Soil Classification Soils seldom exist separately as sand gravel or any other single component in nature They are usually mixtures with varying proportions of different sized particles Each component contributes to the characteristics of the mixture The Unified Soil Classification System USCS is based on the characteristics which indicate how a soil will behave as a construction material The physical properties determined by appropriate tests and calculations are used to classify the soil The criteria for identifying the different soil types is described in Table A 1 and the following paragraphs Table A 2 depicts engineering characteristics of the different soil types pertinent to roads and airfields Major Divisions Symbol Field Identification Procedures Base fractions on estimated weights Wide range in grain sizes all intermediate sizes substantially represented 29 o Fines T Predominantly one size or some intermediate sizes missing Nonplastic fines or fines with little plasticity see ML below Plastic fines see CL below No 4 sieve Gravels gt 12 Fines fraction is larger than G No 200 sieve Wide range in
130. n on ranges of CBR that can be expected for different soil types A conservative estimate of CBR based on the material type may be used for preliminary design During construction the actual CBR can be measured with the dynamic cone penetrometer DCP and the design of the semi prepared pavement can be adjusted as necessary It should be noted that the CBR may change with time as the material becomes saturated Saturation of the material usually results in a reduction in the CBR this fact should be accounted for in the design of the airfield Soaked laboratory CBR values provide a good indication of the reduction in the CBR that may be expected Otherwise conservative values based on the material type and the CBR determined in the field should be used for design The gradation portion of this document also provides an indication of the CBR that may be expected for materials meeting gradation and compaction requirements 4 5 Soil Behavior Soil is compacted to improve its load carrying capability 5 430 00 2 AFJPAM 32 8013 Vol II The compaction of soil reduces its natural variability providing a more uniform structure for operating aircraft Compaction also reduces the soils permeability and susceptibility to erosion Stabilization of soils can be used to improve the strength of the soil or to reduce the effects of plasticity and high liquid limits Stabilizing can also provide dustproofing and waterproofing Stabilization is addressed in Section 4
131. nd directions 400 from approach end spaced midway between remaining side field marker lights ooooo Five Optional Strobe Lights May be placed on centerline 100 apart starting at the outer edge of the overrun Figure 3 5 Airfield Marking Pattern Night Atch 1 21 of 162 25 November 1997 300 100 400 Panels will be 500 150M minimum to 400 100 300 1000 300M maximum distance apart Touch Overrun down Direction of Flight e gt gt Overrun Zone Orange Panel 6 apart when used in pairs Additional Touchdown Zone Cerise Panel 6 apart when used in pairs Panels may be installed to make the LZ usable from both directions Figure 3 6 Airfield Marking Pattern Day 2 00 WIDE SUSPENSION ALUMINUM SUPPORT STRAP lt 3 PER END MT COLORED NYLON DEI FP POLE 1 EACH END BUNGEE CORD QUICK LINK CABLE d ali ATTACHMENT LOWER EDGE STAKES PER CORNER C MODEL ONLY ALUMINUM BUNGEE STAKES 4 EACH VERTICAL PRESSURE EACH LEG OF THE RELIEF SLITS 63 EVENLY ALUMINUM POLE BUNGEE CORD IS SPACED C MODEL ONLY gt STAKE EACH ENDO APPROX 22 00 LONG Figure 3 7 Visual Assault Zone Marker Panel VAMP 3 6 1 1 VAMP C Model TACTEC Part Number AMS 0004 C 00001will be used for C 17 operations The C Model is the high velo
132. ndations For training airfields stabilization of the surfacing material is desirable When stabilizing the airfield surface to improve the strength of the existing material cement and or lime generally will be the most appropriate stabilizing agent to use Bituminous materials are appropriate for stabilizing coarse grained materials However to provide a quality layer the bituminous stabilized material should be mixed in a plant not mixed in place lt is very difficult to obtain the mixing compaction and grade control required using in place mixing of bituminous materials Army TM 5 822 14 Air Force AFJMAN 32 1019 Soil Stabilization for Pavements provides detailed guidance on design and construction of stabilized layers The following paragraphs provide general design and construction guidance 4 8 2 General Design Guidance The thickness requirement for the stabilized layer should be determined from Figure 4 2 No reduction in thickness is allowed due to stabilizing Note A minimum six inches of stabilized material should be used Stabilization results in improved performance and durability Materials to be stabilized with cement or lime should attain a minimum unconfined compressive strength of 5 170 kPa 750 psi using curing periods of 7 days for cement stabilization and 28 days for lime stabilization 4 8 3 General Construction Guidance The following guidance applies to stabilizing with cement and or lime Construction of stabil
133. ndix A These CBR ranges are only estimates and due to the varying soil types and strengths encountered across an airfield the lowest CBR values in the range should be used and then with judgment and caution Measure soil layer thickness and strengths using the DCP C 3 3 1 1 Description The DCP consists of a 16 mm diameter stainless steel rod with a cone attached to one end which is driven into the soil by means of an 8 kg sliding Atch 1 86 of 162 25 November 1997 hammer which is dropped from a height of 575 mm The angle of the cone is 60 degrees and the diameter of the base of the cone is 20 mm The rod may either be a scored version or may be smooth requiring the use of an adjacent measuring scale see Figure C 3 Units that test both paved and semi prepared airfields should use 50 inch long rods as shown in Figure C 3 but 36 inch long rods are available and are adequate for semi prepared airfield evaluations Disposable cones which mount on an adapter may be used in cases where the cone is difficult to remove from the soil This disposable cone remains in the soil Use of disposable cones will increase the number of tests per day that can be accomplished ex w cum HANDLE 8 Kg 17 6 Ib HAMMER ANVIL See 16mm ROD Figure Dynamic Cone Penetrometer C 3 3 1 2 Use Two people are required to operate the DCP One person the operator holds the device by its handle in a vertical positio
134. ne Overrun Note For unimproved airfield continue this pattern m throughout the length For aggregate surfaced Typical Semi prepared Airfield airfields the pattern may be more widely spaced on the remaining portion of the airfield Priority Testing 1 Soft spots Overrun 2 Offsets should be in wheel paths of main gear 3 Centerline 4 Aircraft turnarounds 5 Any area where the aircraft must stop 6 Overrun one test in center 7 Along edges at 500 feet intervals Typical Apron or Turnaround Figure C 2 DCP Test Locations for Semi Prepared Airfields e f field classification methods do not produce clear results or require validation obtain samples for follow up laboratory testing e f materials have been altered or have additives as in the case of dense crushed rock layers or stabilized soil layers identify them as such C 3 2 Thicknesses e Measure actual layer thicknesses in the wheel paths where possible e Use Dynamic Cone Penetrometer DCP data to determine layer thicknesses e Be aware of other sources of strata information such as ditches or excavations This provides useful information on the subbase subgrade C 3 3 Strengths Shearing resistance is one of the most important properties that a Soil possesses A soil s shearing resistance under given conditions is related to its ability to withstand a load The shearing resistance is especially important in its relation to the supporting strength or
135. no distresses or you may have as many as seven distresses If you have trouble telling which distress you are looking at make a reasonable guess The system is flexible enough to give you an accurate rating The seven distresses are Atch 1 56 of 162 25 November 1997 91 92 93 94 95 96 97 Potholes Ruts Loose aggregate Dust Rolling resistant material Jet blast erosion Stabilized layer failure The numbers 91 97 are associated with the Micro Paver Pavement Management System and will be used in the computerized version of this system Fill in the identifying information on the top of the inspection sheet and record the severity levels on the table The following pages will give you the definition of each distress and explain how to determine the severity level for that distress Unless otherwise stated the distress severity measurements for contingency and training operations are the same Atch 1 57 of 162 25 November 1997 91 POTHOLES DEFINITION Potholes are bowl shaped depressions in the airfield surface Once potholes have begun to form the runway will continue to disintegrate because of loosening surface material or weak spots in the underlying soils HOW TO MEASURE Measure the maximum depth of the biggest potholes and determine their severity level In areas of high pothole density observe aircraft reaction The location and number of potholes can be critical to aircraft performance G
136. number of passes The maximum allowable number of C 17 passes at a gross weight of 400 000 Ibs is 450 Atch 1 161 of 162 25 November 1997 E 1 3 Annex A appendix 2 2 Airfield Criteria should be updated to include C 17 specific criteria Runway Length Width Longitudinal Gradient 96 Transverse Gradient 96 Max Grade Change 96 per 200 Shoulder Width Shoulder Transverse Gradient 96 Lateral Clear Area Width Lateral Clear Area Gradient Lateral Safety Zone Width Lateral Safety Zone Slope Overrun Length Overrun Width Aircraft Turnaround Length Aircraft Turnaround Width End Clear Zone Length End Clear Zone Inner Width End Clear Zone Outer Width End Clear Zone Max Gradient 96 Approach Zone Length Approach Zone Inner Width Approach Zone Outer Width Approach Zone Glide Ratio APZ 1 Length APZ 1 Width Taxiway Width Longitudinal Gradient Transverse Gradient Shoulder Width Shoulder Transverse Gradient Clear Area Width Clear Area Gradient Turn Radii Distance RWY centerline to edge of TXY Apron Gradient Shoulder Width Shoulder Transverse Gradient Distance Apron Edge to Obstacle 90 180 165 includes width of runway overrun 500 180 500 Max 5 0 Min 10 500 Desired 32 000 500 2 500 at 10 500 length is constant from 10 500 to 32 000 20 1 2 500 500 60 Max 3 0 0 5 3 0 10 1 5 5 0 110 from TXY centerline to obstacl
137. of approximately 25 000 square feet The starting point 0 00 is at the very end of the overrun Use a rolling wheel measure or steel tape to measure distances Mark every 250 foot point with a nail and plastic surveyor s tape with the station marked on it or use some other permanent marker along the outside edge of the runway out of the trafficked area 250ft 250 Tt 10 00 7 50 5 00 2 50 0 00 3 00 Runway Overrun Threshold Hammerhead Before the runway is used for the first time every section should be inspected to give baseline information As a minimum for contingency operations sections should be located in the touchdown area in the primary braking area at approximately 1000 to 1500 feet at the point of aircraft rotation at approximately 2000 to 2500 feet and at the last 500 feet of the runway The point of rotation may move due to pressure and altitude changes These sections include the areas most likely to be damaged by landing braking stopping acceleration and takeoff for the runway in use Inspect and monitor additional areas where degradation develops STEP TWO INSPECTING THE AIRFIELD AND IDENTIFYING DISTRESSES Conduct as detailed and accurate an inspection as time and conditions permit By doing it right the first time you will be able to identify possible problem areas and monitor them closely during operations There are seven possible problems or distresses In each 250 foot section you may have
138. of features and time available for conducting the tests Test locations must be chosen wisely and should accurately cover each feature or aspect of the airfield yet may need to be minimized due to aircraft operations or time constraints Soil conditions are extremely variable therefore as many tests as time and circumstance will permit should be taken The strength range and uniformity of the area will control the number of tests required In all cases it is advisable to test apparent weak areas first since the weakest conditions control the pavement evaluation In areas of doubtful strength or where evidences of changing layer structure occur the tests may be closely spaced On the other hand in areas where the structure appears to be firm and uniform tests may be few and widely spaced After weak areas have been tested areas of high traffic intensity or loading such as take off touch down zones runway taxiway intersections and taxi lanes on aprons should be tested Figure C 2 shows recommended test locations for semi prepared airfields Conduct as many tests as possible in the time available C 3 Collect Field Data to Determine Airfield Structural Properties C 3 1 Types e Identify surface and any underlying base subbase and subgrade materials using field identification methods and classify using the United Soil Classification System USCS See Appendix A Atch 1 84 of 162 25 November 1997 500 on Centerline 500 on Centerli
139. of the existing soil and any layers that will be constructed above it are important parameters that are input to the design procedure For semi prepared pavements the parameter used for indicating the strength of the layers is the California Bearing Ratio CBR The CBR is a measure of the shearing resistance or strength of the soil The evaluation portion of this document discusses the tools and procedures for quickly obtaining an estimate of the CBR of in place soils For soils or materials that are to be placed i e excavated hauled placed and compacted it will be necessary to determine the CBR that will be obtainable A moisture density relationship proctor curve with accompanying laboratory CBR values is preferred for determining the CBR obtainable in the field and for specifying moisture and density requirements during construction The CBR value of a material to be placed may be significantly different than the in place CBR of the material Some soils loose strength with remolding see Chap 8 FM 5 410 Other soils if properly placed can achieve CBR values greater than existed naturally This is accomplished by compacting the soil at or near optimum moisture content with an appropriate compactive effort to obtain near maximum density If maximum density is not achieved a reduction in available performance results with a reduction in the number of aircraft operations the airfield can support before failure occurs Appendix C provides informatio
140. om taxiway shoulders to prevent water from backing up on to the shoulder area Exception Essential drainage ditches may be sloped up to 10 Atch 1 20 of 162 25 November 1997 Table 3 7 Apron for C 17 Contingency Airfields Contingency Item Airfield Description Semi Prepared and AM 2 Remarks Apron Grades in 1 5 to 3 096 the Direction of Drainage Width of Apron Apron shoulders should be stabilized to Shoulder prevent erosion by jet blast Where adequate sod cover cannot be established the shoulders should be chemically stabilized for blast protection Transverse Grade 1 5 to 5 0 Apron shoulder should be graded to carry of Shoulder away storm water away from the apron In from the Apron shoulder areas remove all tree stumps and loose rocks Aircraft are not permitted to use shoulders on AM 2 airfields due to horizontal and vertical load devices connected to the mat edges Clearance from 30 m 100 ft Edge of Apron to Fixed or Mobile Obstacles 300 1007 400 Lights will be 500 150M minimum to 400 1000 300M maximum distance apart e o o Overrun Direction of Flight e Overrun Green Light 6 apart when used in pairs Additional Touchdown Zone OzWhite Light 6 apart when used in pairs Lights May be installed to Red Light 6 apart when used in pairs make the LZ usable from both Light Reflector Panel Optional Place Reflectors at 200 300 a
141. or example enter Figure 4 6 for a C 17 aircraft with a design gross weight of 450 000 Ibs at the bottom with the in place subgrade CBR Draw a vertical line from the in place subgrade CBR to the intersection of the appropriate design pass level Then draw a horizontal line from this intersection to the vertical axis to determine the thickness of subgrade at the required strength that must exist beneath the AM 2 matting If the preliminary site investigation indicates that the in place subgrade CBR is greater than or equal to the minimum required CBR obtained from Figure 4 3 and that the in place soil strength is consistent for a depth equal to or greater than the thickness required in Figures 4 4 through 4 8 then AM 2 mat surfacing will be adequate to sustain the mission s design traffic Otherwise AM 2 matting will not provide sufficient structural improvement to the natural subgrade to support the design C 17 operations Figures 4 3 through 4 8 should not be used for Navy and Marine airfields since their criteria require a minimum CBR of 25 under AM 2 surfaced airfields Atch 1 34 of 162 25 November 1997 Aircraft Passes Figure 4 3 Soil Strength Requirements for the C 17 on AM 2 Mat 5 000 Aircraft Passes 1 000 0 00 10 00 m seuour Z INV u1eeueg sseuxoiu
142. or the runway is the average of the ratings from all the sections For example SPACIs of 63 59 and 67 in different sections would give an average SPACI of 63 for the whole runway Atch 1 72 of 162 25 November 1997 NOTE If any distress is Red the landing zone safety officer will determine the feasibility of each operation SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS Airfield lamo NV Section Io oo l 2o Inspector 3 e lo E afon SKETCH DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure DISTRESS SEVERITY e 8 pem cL a SES rq dest SD CRI ee SPACI CALCULATIONS REMARKS q 1 4 SPACI 77 NOTE If any distress is red the landing zone safety officer will determine the feasibility of each operation Atch 1 73 of 162 25 November 1997 SEMI PREPARED AIRFIELD INSPECTION SHEET FOR C 17 OPERATIONS airfield Alamo NY __ pw 4 30 97 Section 10 406 12 50 Inspector R enee Me tno Y DISTRESS TYPES 91 Potholes 92 Ruts 93 Loose Aggregate 94 Dust 95 Rolling Resistant Material 96 Jet Blast Erosion 97 Stabilized Layer Failure REMARKS Total deduct value 6 5 4 RATING NOTE If any distress is red the landing zone safety officer will determine the feasibil
143. outes determine designations of feature types and resulting gross loads Additional aircraft movements Atch 1 96 of 162 25 November 1997 on the runway i e back taxiing in the case of an airfield with no parallel taxiway and apron system will also increase the number of passes per each planned mission C 5 Conduct Surface Condition Visual Assessment Visual surveys of the airfield surface can provide information on apparent structural integrity operational condition and projected performance A cursory inspection of the features should be performed and the distress types quantities and severity levels as described in Appendix B should be identified The features should then be assigned overall condition ratings C 6 Refine Airfield Layout Compile Summary of Physical Property Data PPD Update the airfield layout based upon aircraft operational requirements surface condition assessment and results of field test data Each feature should now be distinguishable by the characteristics of surface type thickness and condition subsurface layer types thicknesses and strengths construction history use and traffic type One method to consolidate the cross section or pavement system profile data obtained from field tests and construction history into specific features is to C 6 1 Arrange pavement and soil profile data in relation to the actual test locations on the airfield This will show the range of values and relationship of any
144. personnel are available clipboard inspection sheets this appendix and pens or pencils B 1 3 How the Method Works The method for rating the condition of semi prepared airfields has four steps Step 1 Divide the airfield into features and sections Step 2 Inspect the airfield and identify the distresses Step 3 Calculate the rating for each section Step 4 Use the ratings to determine if the airfield is GREEN Operational for low risk operations AMBER Needs monitoring and should be repaired if possible medium risk operations RED Dangerous and must be repaired high risk operations When the surface condition is rated as amber maintenance should be performed as the mission allows If any single distress is rated as red the landing zone safety officer will determine the feasibility of each operation Inspections should increase in frequency as the condition of the airfield degrades If the condition approaches red inspection could be as frequent as before each operation Atch 1 55 of 162 25 November 1997 STEP ONE DIVIDING THE AIRFIELD INTO FEATURES AND SECTIONS Before you start to inspect the airfield divide the entire field into features and sections This includes the runway both overruns any taxiways the aprons and the hammerheads Each section is 250 feet long and the width of the runway or taxiway The hammerheads and overruns should each be a section The aprons should be divided into sections
145. port an aircraft that has an ACN value equal to or less than the PCN If the ACN is more than the PCN the feature will be overloaded and the expected life reduced Occasional minor overloading is acceptable and there will be situations when operators decide to overload the feature Examples are emergency landings and short term contingencies Atch 1 107 of 162 25 November 1997 e Overload movements should not be allowed on pavements exhibiting signs of structural distresses or failure e For frost susceptible regions overloading should be avoided during periods of thaw or when the subgrade appears weakened e For seasonally wet regions overloading should be avoided if the subgrade appears saturated or weakened by water Atch 1 108 of 162 25 November 1997 APPENDIX D Friction Test Procedures for Contingency Operations D 1 Introduction This appendix presents the basic criteria and procedures used to determine whether a semi prepared contingency airfield is suitable for C 17 operations in terms of surface friction characteristics and usable runway length Appropriate data figures and evaluation charts are included This appendix does not address structural suitability load bearing capacity operational geometrics or airspace clearance issues D 1 1 Scope The procedure described herein is an interim guideline for evaluating the friction characteristics of a semi prepared contingency airfield This appendix is organize
146. pport aircraft Once AGLs are computed for each feature of a given airfield they should be converted to PCNs PCNs for a given feature will vary depending on which aircraft and number of passes they are based upon All reports generated by HQ AFCESA for surfaced airfields base the PCNs on the AGLs for the C 141 aircraft at 50 000 passes This standard will be changed to the C 17 aircraft This facilitates pavement strength comparisons of bases throughout the Air Force Atch 1 104 of 162 25 November 1997 PONS for flexible and rigid pavement systems will be based upon 50 000 passes of the C 17 at a maximum weight of 586 000 and PCNs for semi prepared airfields will be based upon 1 000 passes of the C 17 at a maximum weight of 447 000 pounds C 8 2 In the ACN PCN method the PCN pavement type subgrade strength category tire pressure category and evaluation method are reported together in a code system This code system is presented in Table C 6 Although ICAO does not currently include semi prepared airfields in the ACN PCN reporting method the ACN PCN method may be a useful tool in mission planning The symbol S should be used to identify the pavement type in the reported PCN code The subgrade strength codes should be the same as those used for flexible pavements based upon CBR values Table C 6 ACN PCN Code Subgrade Tire Method of PCN PCN Pavement Type Strength Pressure Determination Numerical R Rigid A High W High T Technical
147. r strength accurately is related to the gradation and plasticity characteristics of the materials The DCP can measure strengths of thin surface layers of fine grained plastic materials but requires thicker surface layers for the non plastic coarse grained materials The penetration depth required for measuring actual strength of the surface layer with the DCP varies with soil types as follows Average FED e Soil inches CH 1 CL 3 SC 4 SW SM 4 SM 5 GP 5 SP 11 Note The shearing action of the C 17 while braking during landing operations will create loose till on dry unstabilized soil surfaced runways in arid or semi arid regions The number of allowable passes may be significantly lower than those predicted using standard evaluation procedures The DCP data collected at the top of the surface layer in the unconfined material if treated as a separate layer in calculating allowable loads or passes may provide a good indication of the surface capability to withstand the additional loads and stresses expected during landing operations Special Considerations 1 DCP tests in highly plastic clays are generally accurate for depths to approximately 12 inches At deeper depths clay sticking to the lower rod may indicate higher CBR values than actually exist Oiling the rod will help without significantly impacting the test results It may be wise to auger out the test hole after each 12 inch depth encountered to eliminate the clay
148. rated with a 12 VDC cigarette lighter plug found in most vehicles The Bowmonk includes a connection for exporting data via an RS 232 serial port to a personal computer for permanent storage and analysis The internal memory of the Bowmonk AFM 2 will hold up to 99 tests before it must be downloaded to a PC A stripchart printer is provided for real time hardcopy printouts of the data in the field See Figure D 5 for a close up of the instrument panel of the Bowmonk unit D 3 2 Measurement Parameters The Bowmonk measures the deceleration of the vehicle during a skid test The values are reported as a percentage of the acceleration due to gravity 96g Both peak and average mean calculated decelerations are provided as well as calculated stopping distance time of deceleration and velocity at the start of the skid This ground vehicle deceleration data can then be correlated to the required aircraft Runway Condition Rating RCR for comparing available runway length to stopping distance required by the aircraft D 3 3 Bowmonk Installation In the HMMWV and six pax the Bowmonk unit is placed beside the driver and secured in a horizontal configuration With the motorcycle and quad the unit is placed on the equipment racks The unit should be horizontal to within 15 degrees The unit does not have to be perfectly level since it has an internal software routine that compensates for small deviations from level It will be necessary to construct pl
149. ration If device is armed and a delay of more than 15 seconds occurs device should be reset and then rearmed Press button A to arm for first friction test Check to be sure display shows SET FOR TEST 1 on first line or whatever test number is being conducted ENTER TO ACCEPT will be displayed on line two Press ENTER to accept The display will now show RUNWAY ID Press and hold ENTER until unit beeps at least twice Release ENTER button Display will show PLEASE WAIT for several seconds Then display will show ARMED FOR TEST 1 on first line Second line will display SPEED O Begin vehicle acceleration smoothly but quickly Acceleration should be uniform without spinning tires or excessive vehicle bounce Proceed down runway accelerating uniformly to target test speed Unit will indicate current speed Once test speed has been reached maintain uniform speed for 2 seconds Perform skid test Apply full braking until coming to a complete stop Unit will display DON T MOVE CALCULATING Keep the vehicle stationary to allow the unit to complete its internal calculations and display results This is particularly important with the motorcycle and quad Nominal steering will be required If the vehicle twists more than 15 degrees from the longitudinal line then the test must be repeated Unit will now display measured PERCENT G on first line and SPEED on second line If the results ar
150. remain dull A 2 2 3 7 Feel Test e Consistency Squeeze a piece of undisturbed soil between the thumb and forefinger It may be hard stiff brittle friable sticky plastic or soft Remold the soil by working it between the hands This can indicate the natural water content Clays which become fluid on remolding are probably near their liquid limit If they remain stiff and crumble they are probably below their liquid limit e Texture Rub a portion of fine grained soil between the fingers or on a more sensitive area such as the inside of the wrist Results are similar to the bite or grit test Atch 1 54 of 162 25 November 1997 APPENDIX B Condition Survey and Maintenance Procedures B 1 Condition Survey Procedure B 1 1 Introduction During contingency or expedient operations it is important that personnel have the ability and tools to quickly and accurately assess a pre existing or newly constructed unsurfaced airfield and to monitor it for required maintenance This rating system will show you how to divide the airfield into features runway taxiway apron hammerhead and overruns and sections identify the distresses problems that exist or develop rate the severity of each distress and determine whether the airfield is operational or should be closed for repairs B 1 2 Equipment Required Measuring wheel or 100 foot steel tape carpenter s 6 foot folding rule straightedge 8 foot 2 4 or other stringline if enough
151. rfields for various C 17 aircraft missions 4 11 1 Example 1 Design an airfield in the theater of operations for 200 operations of a C 17 A special tactics team determined that the soil s in place CBR was 16 for a depth of approximately 24 inches beyond which there is a 12 inch layer of 10 CBR material The airfield s geometric design does not include a parallel taxiway Note The number of required passes should be multiplied by two to account for the aircraft taxiing down the runway to takeoff or unload cargo Step 1 The design aircraft has been designated as the C 17 The design gross weight of the C 17 is 447 kips which seems reasonable in regard to mission requirements Step 2 The design aircraft passes stated were 200 however for design purposes as noted above 400 passes will be used to account for taxi movements Step 3 Using Figure 4 1 determine the minimum required subgrade strength to support 400 passes of a 447 kip C 17 aircraft Enter Figure 4 1 with 400 passes and draw a vertical line to just below the 450 kip gross weight curve From this point draw a horizontal line to the vertical axis to determine the required CBR The required subgrade CBR for 400 passes of a 447 kip C 17 is approximately 15 CBR Step 4 Since the minimum required CBR is less than the in place CBR 15 16 then the in place subgrade surface strength is sufficient to support mission Atch 1 38 of 162 25 November 1997 requirements
152. riction Tests Simultaneously Atch 1 113 of 162 25 November 1997 D 3 Bowmonk Unit The Bowmonk Airfield Friction Meter Mk Il was the device used for this research testing The use of any other device is not recommended since the data correlations were developed with this unit The Bowmonk is manufactured in England and was designed to provide airfield managers with a simple consistent and automated method for predicting the available friction between the aircraft tires and runway surface The unit was originally designed for use on paved runway surfaces such as asphalt or concrete but has now been evaluated for applicability to skid testing on semi prepared contingency airfields A skid test is performed with the decelerometer unit installed on a flat and level surface in the ground vehicle and the resulting ground vehicle deceleration measurement is used to predict aircraft stopping performance In this section the hardware will be discussed the fundamental measurements will be described specific installation recommendations will be provided and procedures for testing and operating the Bowmonk will be detailed D 3 1 Hardware Description The Bowmonk unit measures approximately 6 inches by 9 inches by 3 inches and weighs only 6 pounds It is relatively simple to operate and is portable for field use The unit is battery powered and can operate for up to 16 hours in the field on a single charge If necessary it may be recharged or ope
153. rture 500 ft Clearance Surface Inner Width at Inner 152 5 m 500 ft 20H 1V Remains constant throughout length 11 Slope Length Minimum 3 200 m The desired slope length is 9 733 m 10 500 ft 32 000 ft 12 Width at Outer 762 00 m 2 500 ft Width of approach departure Edge at 3200 m 10 500 ft clearance surface is constant from from inner edge 3 200 m 10 500 ft to 9 753 32 000 ft from the inner edge Atch 1 15 of 162 25 November 1997 CLEAR ZONE LENGTH 152 5m 500 APPROACH DEPARTURE SURFACE SEE FIGURE 3 3 ee me START OF CLEARZ p mM l tn gt OF CH DEPARTURE ul S CE m x m LL 0 72 CENTERLINE amp SHOULDER 2 2 CLEAR LIM PLAN N T S BEGINS ELEVATION A LINE ELEVATION RUNWAY END ax Max grade chan 2 in first 500 at each LONGITUDINAL PROFILE N T S Figure 3 1 Primary C 17 Contingency Airfield Surface End Details Atch 1 16 of 162 25 November 1997 CLEAR ZONE 152 5m 500 OVERRUN LENGTH TURN AROUND SEE NOTE 3 CLEAR En 50 D ZONE 45 DEGREE FILLET ro RUNWA Y 152 5m 5007 85 5m 280 min 27 5m 90 R E TAXIWAY 18 5m 60 CLEAR AREA SEE NOTE 1 ie 7 TAXIWAY p E 7
154. s Do not locate these ditches within 27 5 meters 90 feet of a runway centerline Such ditches should be essentially parallel with the runway Remove or embed rocks larger than 2 inches in diameter Cut tree stumps brush and other vegetation excluding 4 Longitudinal Maximum 5 096 Grades are exclusive for clear zone and and are not part of the overrun but are Transverse shaped into the overrun grade See Grade of Table 3 2 Item 3 for additional Surface information Grades may slope up or down to provide drainage Exception Essential drainage ditches may be sloped up to 1096 in the primary surface area and grass to within 2 inches of the ground Table 3 4 Accident Potential Zones APZ for C 17 Contingency Airfields Contingency Item Item Airfield N Description Semi Prepared and AM 2 Remarks 18 APZ 1 762 Limit where possible the following within the APZ Length 2 500 ft Actions that release any substances into the air that would impair visibility or otherwise interfere with operating aircraft such as steam dust and smoke Actions that produce electrical emissions which would interfere with aircraft and or communications or navigational aid systems Actions that produce light emissions direct or indirect reflective that might interfere with pilot vision 2 APZ 1 Width 152 m 500 ft Items that unnecessarily attract birds or waterfowl such as sanitary landfills feeding stations or certain type
155. s a percent of the maximum density at CE 55 4 The minimum compacted layer thickness is 6 inches for an airfield 5 Select material will have a CBR 20 and subgrade CBR 4 8 Stabilization There are two major types of stabilizing procedures mechanical and chemical Mechanical stabilization involves any of the following compaction blending of aggregates or adding a bitumen Chemical stabilization involves the addition of material such as lime cement or fly ash that chemically reacts with the Soil or itself to improve properties of the soil See FM 5 410 Military Soils Engineering for further information As discussed previously stabilization may be used to increase the strength provide dust proofing reduce the maintenance effort required for continued operations and increase performance by improving the shearing resistance during operations Stabilization of a contingency airfield is appropriate when time and logistics allow for it to be accomplished and the mission requirements are substantial enough to require it Functions of stabilization for traffic areas and non traffic areas of the airfield are listed in Table 12 5 pp 12 19 see FM 5 430 00 2 AFJPAM 32 8013 Vol Il Table 12 6 pp 12 21 see FM 5 430 00 2 AFJPAM 32 8013 Vol Il provides a table listing dust control and waterproofing materials that can be used and their appropriate application Atch 1 27 of 162 25 November 1997 4 8 1 Stabilization Recomme
156. s of crops or vegetation Explosive facilities or activities Troop concentrations such as housing areas dining or medical facilities and recreational fields that include spectators Atch 1 14 of 162 25 November 1997 Table 3 5 Imaginary Surfaces for C 17 Contingency Airfields Contingency Item Airfield Description Semi Prepared and AM 2 Remarks Runway length plus 305 m 1 000 ft Centered on the runway Includes lengths of clear zones 55 m 180 ft Centered on the runway Transverse Minimum 2 096 Transverse grades may slope up or Grades within Maximum 5 0 down to provide drainage ditches Primary Surface Centerline of drainage ditches must be established away from runway shoulders to prevent water from backing up onto the shoulder area Exception Essential drainage ditches may be sloped up to 1096 in the primary surface area and clear zones Do not locate these ditches within 27 5 meters 90 feet of an Assault Landing Zone centerline Such ditches should be essentially parallel with the runway 4 Lateral Safety 27 5 Measured from the runway centerline Zone Inner Edge 90 ft Coincident with the lateral edges of the primary surface Lateral Safety 42 5 140 ft from the runway centerline Connects the primary and the in direction of surface drainage Zone Outer Edge approach departure clearance surfaces Horizontal No Requirement Surface Approach 152 5 m Measured from runway end Depa
157. selected based upon their service behavior Suggested CBR values for such materials are Graded Crushed Aggregate 100 Macadam 100 Bituminous Binder 100 Limerock 80 Stabilized Aggregate 80 Soil Cement 80 Sand Shell or Shell 80 Sand Asphalt 80 Other Strength Factors C 3 3 2 1 Surface and Subsurface Drainage Locate depth of water table Atch 1 94 of 162 25 November 1997 Look at contours in area signs of surface drainage problems and wet or swampy areas Coarse grained soils have better internal drainage Moisture content plays significant role in bearing capacity Note the size and depth of any storm drain culverts under the pavement C 3 3 2 2 Cut fill areas indicate possible feature changes based on changing subsurface layers C 3 3 2 3 Frost Areas Subgrade strengths are reduced significantly during thaw periods if the potential exists for structural failure due to frost Detrimental frost action will occur if the subgrade contains frost susceptible materials the temperature remains below freezing for a considerable amount of time and an ample supply of ground water is available If all three conditions exist and frost damage is apparent Frost Area Soil Support Indexes FASSIs are used in lieu of CBRs F1 and S1 Soils 9 0 FASSI F2 and S2 Soils 6 5 FASSI F3 and F4 Soils 2 3 5 FASSI Clays silts and some gravelly and sandy soils with high percentages of fines
158. ses of a 447 kip C 17 aircraft Enter Figure 4 1 with 1 000 passes and draw a vertical line to just below the 450 kip gross weight curve From this point draw a horizontal line to the vertical axis to determine the minimum required CBR The required subgrade CBR for 1 000 passes of a 447 kip C 17 is approximately 18 CBR Step 4 Since the required CBR is greater than the in place CBR 18 4 then the subgrade must be improved structurally to support mission requirements First determine the thickness of 18 CBR material required above the in place subgrade to support mission requirements Enter Figure 4 2 at the top with the in place subgrade CBR 4 and draw a vertical line down until it intersects the design gross weight of the C 17 or 447 kips Next draw a horizontal line from this intersection until it intersects the design pass level of 1 000 passes Finally draw a vertical line from this intersection downward until you intercept the required thickness The design requires 21 inches of 18 CBR material be placed over the in place subgrade in order to support 1 000 passes of a 447 kip C 17 aircraft Step 5 Available aggregate and construction resources are limited and the construction of a 21 inch structural layer would be prohibitive A stockpile of Atch 1 40 of 162 25 November 1997 AM 2 landing mat is available and a decision is made to determine the plausibility of an AM 2 mat surfaced airfield First determine the minimum
159. situations They can be conducted on paved or unpaved runways semi prepared Since training airfields are for long term operations semi prepared surface structural and Atch 1 4 of 162 25 November 1997 dimensional requirements are more stringent than for contingency airfields Stabilization may be required 1 5 Purpose The purpose of this document is to provide criteria and guidance to DoD organizations concerned with planning design construction evaluation and maintenance of semi prepared airfields for contingency and training operations of the C 17 This document will remain in effect until the criteria and data are incorporated into FM 5 430 00 01 02 AFJPAM 32 8013 Volumes and II Planning and Design of Roads Airfields and Heliports in the Theater of Operations Criteria for planning and design of airfields for C 17 routine and training operations will be contained in El 02C013 AFJMAN 32 1013 Atch 1 5 of 162 25 November 1997 Section 2 Aircraft Characteristics See Figures 2 1 and 2 2 for horizontal vertical and landing gear dimensions Horizontal Dimensions Length 174 0 feet Height 55 feet 1 inch Wing Span angst tips 169 feet 9 inches Location of outboard engine 45 feet 9 inches Location of inboard engines 24 feet 5 inches Vertical Clearances Top of fuselage 24 feet 1 inch Top of vertical stabilizer 55 feet 1 inch Bottom of wing tip 13 feet 10 inches Bottom of outboard engin
160. ssentially parallel with the runway Note 1 For C 17 airfields without parallel taxiways provide a method for turning around at both ends of the usable surface The turnarounds should be 55 m 180 ft long and 50 m 165 feet wide including the runway overrun width with 45 fillets and be constructed to same structural and gradient standards as the runway overrun The aircraft must be positioned within ten feet of the runway edge prior to initiating this turn Provide an expanded hammerhead or taxiways and aprons if the airfield maximum on ground requirement is greater than one Atch 1 12 of 162 25 November 1997 Table 3 2 Overruns for C 17 Contingency Airfields Contingency Item Airfield Description Semi Prepared and AM 2 Remarks Overrun 91 5 m The overruns must be constructed to the same 300 ft standards as the runway Overruns for mat surfaced runways must also be constructed with mat 2 Overrun 275m Width 90 ft 3 Longitudinal See Remarks The grade must be constant and is the same as Grade of the last 150 m 500 ft of the runway end Overruns 4 Transverse See Remarks Same as runway end Grades should slope Grade of downward from overrun centerline Overruns 3 3 Clear Zones Accident Potential Zones and Imaginary Surfaces The clearance and grade requirements for assault landing zones are established to provide a reasonable level of safety at forward operating locations during contingencies Criteria for clear
161. subgrade surface CBR requirements beneath the landing mat from Figure 4 3 Enter the chart at the bottom with the design aircraft passes 1 000 and draw a vertical line until it intersects the design gross weight of the aircraft From this intersection draw a horizontal line across to the vertical axis to determine the minimum subgrade CBR that is required beneath the AM 2 mat The required subgrade CBR for 1 000 passes of a 447 kip C 17 on AM 2 landing mat is 3 2 CBR or 3 5 CBR Step 6 Since the required subgrade CBR beneath the AM 2 matting is less than the existing in place subgrade CBR 3 5 lt 4 the surface CBR requirements are met Next determine the minimum thickness of the subgrade required to support the mission s design traffic Enter Figure 4 6 for a 450 kip C 17 with the in place CBR of 4 and draw a vertical line until it intersects the design pass level of 1 000 Then draw a horizontal line until it intersects the vertical axis to determine the minimum thickness of 4 CBR material required beneath the AM 2 matting A thickness of 5 inches of 4 CBR material is required beneath the AM 2 mat to support 1 000 passes of a 447 kip C 17 Since the in place CBR of 4 exists for a depth of 12 inches the thickness requirements beneath AM 2 mat are met and AM 2 mat surfacing is sufficient to support the design mission traffic 4 11 4 Example 4 Information provided by headquarters indicates that the airfield in Example 3 will be required
162. sure for the C 17 Move vertically to the 38 1 ESWL curve and then horizontally to the right edge of the chart Draw a straight line from this point through the CBR line at 20 and read 4 000 coverages Multiply 4 000 coverages by 1 37 to determine the allowable number of passes which is 5 480 e Step 2 Evaluate Surface Layer Thickness Select the Semi Prepared Surface Evaluation Curve for the C 17 Enter the top of the chart at 8 inches drawing a vertical line Line 1 downward through the aircraft pass curves Enter the bottom of the chart at 400 000 Ibs and draw a vertical line up to the 15 CBR curve then horizontally to intersect with Line 1 The point of intersection indicates an allowable pass number of approximately 2 500 e Step 3 Evaluate the Subgrade Enter the top of the chart at 16 inches drawing a vertical line Line 1 downward through the aircraft passes Atch 1 102 of 162 25 November 1997 Enter the bottom of the chart at 400 000 Ibs and draw a vertical line up to the 5 CBR curve then horizontally to intersect with Line 1 The point of intersection indicate an allowable pass number of approximately 1 000 e nthis example the subgrade layer results in the lowest allowable number of passes The maximum allowable number of C 17 passes at a gross weight of 400 000 Ibs is 1 000 C 7 1 2 4 A Subgrade Strength Chart Figure C 11 is also useful in that it provides subgrade strengt
163. t the design procedure for the use of AM 2 matting should proceed if sufficient mat is available Otherwise alternate means of strengthening the in place subgrade should be explored as discussed earlier 4 12 Drainage Design Adequate surface drainage should be provided in order to minimize moisture damage to the airfield The rapid removal of surface water reduces the potential for absorption and helps to ensure more consistent soil strength The surface geometry of the airfield should be designed so that drainage is provided at all points Depending upon the surrounding terrain surface drainage may be achieved by a continual cross slope or by an interconnected series of cross slopes Except in special circumstances the two year storm frequency is considered a satisfactory design frequency for contingency airfields Design of surface drainage should be in accordance with TM 5 820 3 AFM 88 5 Chapter 3 Requirements for subsurface drainage are outlined in TM 5 820 2 AFM 88 5 Chapter 2 4 13 Dust Control The primary objective of a dust palliative is to prevent soil particles from becoming airborne as a result of wind or traffic Dust palliatives must be able to withstand the abrasion of wheels and tracks The abrasive action of aircraft landing gear may be too serious for the use of some dust palliatives However the use of dust palliatives in non braking areas should be considered especially in arid and semi arid climates No one product has bee
164. t 80 Sand Shell or Shell 80 Sand Asphalt 80 DCP DATA SHEET 1 No of hammer blows FEATURE DATE between test readings TEST LOCATION 2 Accumulative cone No of DCP CBR Depth penetration after each set of Blows Penetration p Blow Set Index in hammer blows 1 60 7 3 Difference in accumulative penetration 2 at start and end of each hammer blow set 4 3 divided by 1 b Enter 1 for 17 6 Ib hammer 2 for 10 1 Ib hammer 6 4 x S 7 From CBR versus DCP correlation table C 2 or C 3 8 Previous entry in 2 divided by 25 4 rounded off to 0 2 in Suggested DCP Data Sheet Atch 1 156 of 162 25 November 1997 DCP DCP DCP Index in Blow CBR Index in Blow CBR Index in Blow CBR mm blow mm blow mm blow lt 3 0 10 100 12 18 56 57 2 20 3 2 0 11 92 0 50 17 58 3 1 0 12 84 13 16 59 60 3 0 3 80 14 0 55 15 61 62 2 40 2 9 0 13 76 15 0 60 14 63 64 2 50 2 8 0 14 70 16 0 65 13 65 66 2 60 2 7 0 15 65 17 0 70 12 67 68 2 6 0 16 61 18 19 11 69 71 2 80 2 5 4 60 20 21 0 80 10 72 74 2 4 0 17 57 22 23 0 90 9 75 77 3 00 2 3 0 18 53 24 26 1 0 8 78 80 2 2 5 0 19 50 27 29 7 81 83 2 1 0 20 47 30 34 6 84 87 3 40 2 0 21 45 35 38 5 88 89 3 50 1 9 0 22 43 39 4 8 92 96 1 8 0 23 41 440 4 7 97 101 4 00 1 7 6 40 41 1 60 4 6 102 107 1 6 0 24 39 42 4 4 108 114 1 5 0 25 37 43 4 3 115 121 1 4 7 0 26 35 44 4 2 122 130 5 00 1 3 0 27 34 45 4 1 131 140 1 2 0 28 32 46 1 80 4 141 152 1 1 0 29
165. t the underlying weak layer the airfield requires structural improvement to withstand the design traffic Structural improvements for contingency airfields include the addition of an aggregate or select fill layer s stabilization of the natural subgrade as discussed previously or the use of AM 2 matting The design criteria for aggregate surfaced and AM 2 mat surfaced airfields is presented below 45 40 35 30 25 CBR 10 100 1 000 10 000 AIRCRAFT PASSES Figure 4 1 Unsurfaced Strength Requirements for the C 17 Aircraft 4 10 2 Aggregate Surfaced Design The design of an aggregate surfaced contingency airfield for the C 17 aircraft is necessary if the in place subgrade CBR cannot support the design mission requirements The first step was accomplished by evaluating the proposed site for the unsurfaced criteria Doing so provides the designer with the minimum required surface CBR to support C 17 aircraft operations at the design pass level The next step is to use Figure 4 2 to determine the minimum required thickness of the minimum CBR determined from Figure 4 1 4 10 3 AM 2 Mat Surfaced Design Heavy cargo aircraft may not be able to operate on unsurfaced airfields due to the soil strength requirements Th
166. tant FM 5 430 00 2 AFJPAM 32 8013 Vol Il A proper description of the field condition at a proposed site includes the following elements e ground cover vegetation natural slopes soil types classification soil density moisture content soil consistency soft or hard existing drainage natural soil strength in terms of California Bearing Ratio The information listed above is needed to determine the construction effort required to provide an airfield capable of supporting the design number of operations of the C 17 aircraft 4 3 Base Subbase and Subgrade A semi prepared pavement structure typically consists of three layers the existing subgrade a subbase and a base course A semi prepared airfield may or may not have a subbase or a base If the existing material the subgrade is determined to be capable of supporting aircraft operations no subbase or base will be required A subbase may consist of subbase material and a select material if a select material is available and of better quality than the subgrade see FM 5 430 00 1 AFPAM 32 8013 Vol 1 Chapter 5 The subgrade potential subbase and Atch 1 24 of 162 25 November 1997 potential base materials need to be identified according to the Unified Soil Classification System USCS The evaluation portion of this document details the USCS and field procedures for identifying soils and categorizing them according to the USCS 4 4 Soil Strength The strength
167. tected and the design is valid 4 11 2 Example 2 Developments in the theater of operations require the design of a second contingency airfield to support 200 passes of a C 17 The special tactics team determined that the soil s in place CBR at the second site is 12 for a depth of approximately 20 inches beyond which the CBR of the material increased This airfield will not possess a parallel taxiway Step 1 The design aircraft has been designated as the C 17 The design gross weight of the C 17 is 447 kips which seems reasonable in regard to mission requirements Step 2 The design aircraft passes stated were 200 however for design purposes as noted in Example 1 400 passes will be used to account for taxi movements Step 3 Using Figure 4 1 determine the minimum required subgrade strength to support 400 passes of a 447 kip C 17 aircraft Enter Figure 4 1 with 400 passes and draw a vertical line to just below the 450 kip gross weight curve From this point draw a horizontal line to the vertical axis to determine the required CBR The required subgrade CBR for 400 passes of a 447 kip C 17 is approximately 15 CBR Step 4 Since the required CBR is greater than the in place CBR 15 gt 12 then the subgrade must be improved structurally to support mission requirements First determine the thickness of 15 CBR material required above the subgrade Atch 1 39 of 162 25 November 1997 to support mission requirements Enter Figure 4 2
168. ter a valid start of the deceleration must be sustained at less than braking threshold for the braking to be determined to have ended and the vehicle to have stopped The brake end time is then taken as the beginning of this time window The time between the brake start and brake end times is the Braking Time The average deceleration will be calculated over this interval unless you have specifically included in the average the deceleration during the Brake Delay Time as well The Stopping Time Window can be adjusted between 00 00 sec and 02 55 sec the default value is 00 10 secs D 3 4 2 2 6 PFT Trig This is the brake pedal force in Newtons required to trigger the instrument when using the pedal force transducer Not applicable to the Bowmonk AFM2 model unit D 3 4 2 2 7 Max Over The time window interval in seconds over which the developed or sustained peak friction reading is determined This setting will cause the friction value to be the greatest lowest value seen as the window is scanned across the data D 3 4 2 3 Trim Parameters The Bowmonk unit is programmed with some adjustable parameters whose values can be changed This editing option allows their value to be changed D 3 4 2 4 Trim Zeros This menu allows the user to periodically check and trim the transducer zero levels Zeroing can be done on any flat surface by following the prompts on the display Properly trimmed zeros allow the instrument to be used to make accurate meas
169. the 1 4 points so that the airfield is divided into 4 test sections see Figure D 9 As shown in Figure D 9 the skid testing should be conducted just outside the C17 wheelpaths to either side The skid vehicles though much smaller than the aircraft can prematurely degrade the runway surface and potentially reduce the available friction The distance between the C 17 main tire groups is approximately 25 feet With the aircraft on the centerline the center of the wheelpaths are about 12 5 feet from the centerline The width of each main group of 6 tires is 7 5 feet adding another 4 feet for a total of 17 feet to the outside edge of either tire group Allowing another 10 for lateral wander of the aircraft between landings the inside edge of the skid vehicle should then Atch 1 130 of 162 25 November 1997 located 27 feet from the centerline Since the four wheeled skid vehicles have a 6 foot wheel base the center of the skid vehicle should be located 30 feet from centerline during a skid If possible the driver should perform each skid test on a virgin section of runway one that hasn t been skidded on yet This can be done by skidding a little further up or down the runway or moving the vehicle sideways 2 to 3 feet if two runs have to be made in approximately the same location The actual skid locations patterns and sequences are not critical to the friction testing procedure Much more important is that the areas on whic
170. the airfield whereas a coverage takes into account the fact that aircraft wander somewhat and the wheels do not follow the same identical path on each pass To determine the number of passes multiply the number of coverages by the pass coverage ratio for the aircraft and traffic area being evaluated Example Determine the allowable number of passes for a 400 000 Ib C 17 aircraft on the following soil cross section 8 Aggregate Surface Course CBR 20 Subgrade CBR 10 Solution e Step 1 Evaluate Surface Course Strength Enter the Surface CBR nomograph chart at 98 PSI the expected contact tire pressure for the C 17 Move vertically to the 38 1 ESWL curve and then horizontally to the right edge of the chart Draw a straight line from this point through the CBR line at 20 and read 4 000 coverages Multiply 4 000 coverages by 1 37 to determine the allowable number of passes which is 5 480 e Step 2 Evaluate Surface Layer Thickness Subgrade CBR Select the Semi prepared Surface Evaluation Curve for the C 17 Enter the top of the chart at 8 inches drawing a vertical line Line 1 downward through the aircraft pass curves Enter the bottom of the chart at 400 000 Ibs and draw a vertical line up to the 10 CBR curve then horizontally to intersect with Line 1 The point of intersection indicates an allowable pass number of approximately 450 n this example the subgrade layer results in the lowest allowable
171. the laptop computer Note the serial numbers that are displayed when program starts up Check to see if the unit you wish to download matches one of these numbers The serial number of the unit is located on the bottom of the test summary strip chart printout If not then data cannot be downloaded Click on OK button on windows program to start it Click on UPLOAD button to begin process of uploading During the upload do not disturb the computer Bowmonk or connecting cable Once uploading is complete access and browse through database to ensure that the recently collected test data has downloaded Exit database If another unit is not going to be downloaded immediately then exit completely from the AFM2 program If the AFM2 program remains running and the computer suffers from a glitch lockup or shutdown due to sleep mode or low battery the database will be corrupted resulting in loss of data and requiring re installation of software Disconnect cable and shutdown both the Bowmonk and computer to save power if they are not going to be used immediately Reset unit to prepare for next series of tests D 3 3 4 Clearing and Resetting Bowmonk The following steps are required to ready the unit for the next series of tests This procedure will clear out all the test results collected so far Unit settings will not be affected by this procedure Press RESET to turn unit on if not already on Displ
172. to get the file unsurf1 O exe then type get unsurf1 O exe Note All programs on the WWW homepage and FTP site are compressed executables Upon first time execution of any program multiple files will be extracted therefore it is vital that each program is put in its own subdirectory with no other files when it is first executed 1 2 Definitions 1 2 1 Acronyms ACN Aircraft Classification Number CBR California Bearing Ratio DCP Dynamic Cone Penetrometer ETL Engineering Technical Letter FASSI Frost Area Soil Support Index FTP File Transfer Protocol HMMWV High Mobility Multi purpose Wheeled Vehicle Atch 1 3 of 162 25 November 1997 e PCASE Pavement Transportation Computer Aided Structural Design and Evaluation computer Programs PON Pavement Classification Number RCR Runway Condition Rating RRM Rolling Resistant Material SPACI Semi prepared Airfield Condition Index SST Special Tactics Team UNSEVA Unsurfaced Evaluation Program UNSURF Unsurfaced Design Program USCS Unified Soil Classification System VAMP Visual Assault Zone Marker Panel VFR Visual Flight Rules 1 2 2 Terms e Pass The movement of an aircraft over a specific spot or location on a pavement feature e Base or Subbase Courses Natural or processed materials placed on the subgrade e Subgrade Natural in place soil upon which a pavement base or subbase course is constructed e Compacte
173. to support 5 000 passes of a C 17 rather than the original 1 000 passes Redesign the airfield accordingly Step 1 The design aircraft and its design gross weight are denoted above as a 447 kip C 17 Step 2 Due to changes in mission requirements the design pass level was increased from 1 000 passes to 5 000 passes Step 3 Following the guidance in Step 3 of the example above the unsurfaced criteria minimum surface CBR requirement is determined to be a 23 CBR Since the in place subgrade CBR is much less than the required subgrade CBR 4 lt 23 the in place subgrade must be improved structurally to support the mission s design traffic Step 4 Use the guidance in step 4 of the above example to determine the minimum required thickness of an aggregate or select fill layer of at least a 23 CBR to be placed above the in place subgrade material The criteria in Figure 4 2 indicate that approximately 25 inches of a 23 CBR material is required to support 5 000 passes of a 447 kip C 17 Atch 1 41 of 162 25 November 1997 Step 5 Since logistics prohibits the use of a large amount of fill AM 2 mat surfacing should be considered As shown in step 5 above determine the minimum surface subgrade CBR required to support AM 2 matting for the design mission traffic From Figure 4 3 it is determined that a 10 CBR material is required to support mission requirements Since the in place subgrade CBR is less than the required CBR 4 10 t
174. true dry strength of the soil A 2 2 3 1 2 Ball Test Alternative to Pat Test e Procedure Select enough material to mold into a ball about one inch in diameter Mold the material until it has the consistency of putty adding water if necessary From the molded material make at three test specimens 1 2 inch diameter balls Allow the test specimens to dry in the air sun or by artificial means as long as the temperature does not exceed 60 degrees C Test the strength of the material by crushing between the fingers Results No strength The dry specimen crumbles into powder with mere pressure of handling ML Low strength The dry specimen crumbles into powder with some finger pressure ML or MH Medium strength The dry specimen breaks into pieces or crumbles with considerable finger pressure MH or CL High strength The dry specimen cannot be broken with finger pressure but will break into pieces between the thumb and a hard surface CL or CH Very High strength The dry specimen cannot be broken between the thumb and a hard surface CH Note Natural dry lumps about 1 2 inch in diameter may be used but do not use the results if any of the lumps contain particles of coarse sand The presence of highly cementitious materials in the soil such as calcium carbonate may produce exceptionally high strengths A 2 2 3 2 Roll or Thread Test Procedure A representative portion of the sample is mixed with
175. ttached to each end of the aluminum support pole s by this method Attached to the top end of each pole is a bungee system that is made up of 10 millimeter double nylon coated bungee cord Each of the two bungee systems consists of a single 52 inch long unstretched piece of bungee cord This cord is folded and crimped in the middle forming a loop and at each of the two ends The three loops that are formed by this crimping are fitted with three 2 inch long 0 187 inch diameter quick link connectors The connector at the middle of the bungee is attached to the top of the aluminum pole A 9 inch aluminum tent stake is attached to each of the four bungee ends to the bottom of each pole and to each of the two stiffeners at the bottom edge of the panel 3 6 1 4 Additional Equipment In addition to the 6 aluminum tent stakes common to all VAMP models there are six 8 inch eight 8 inch for the VAMP C Model steel spikes attached by stainless steel safety cable These spikes are much stronger than the aluminum stakes and they allow for the use of the VAMP on extreme surface conditions such as asphalt Atch 1 23 of 162 25 November 1997 Section 4 Structural Design Criteria 4 1 Introduction This section presents the procedures for the structural design of semi prepared airfields for the C 17 aircraft This criteria is submitted as a supplement to that given in AFJPAM 32 8013 FM 5 430 00 2 Planning and Design of Roads Airfields and H
176. types and tread designs should be used Detailed descriptions of each vehicle are provided in the following sections Table D 1 Nominal Tire Pressures Tread Depth and Make Tread Tire Depth Vehicle Type Pressure new Tire Make HMMWV 20 psi 3 4 Goodyear Wrangler R T II 2 psi 36 x 12 50 16 5 LT load range C Six Pax Truck 60 psi 15 32 Goodyear Wrangler AT 5 psi 235 85R16 m s load range E Quad rear tires 7 5 psi 18 32 Dunlop KT645 1 psi AT 25 x 10 12 Motorcycle 20 psi 13 32 Dunlop K750A rear tires 2 psi 4 60 17 4 P R Note Tires used should be in good condition with a tread depth at least half of that when new with no flat spots or other abnormalities D 2 1 AFSOC STT AN MRC 144 HMMWV The AN MRC 144 system is the combination of an M 998 HMMWV and an AN GRC 206 communications pallet see Figure D 2 The AN MRC 144 HMMWV Package is the standard air traffic control ATC communication vehicle used by combat controllers from the SST This HMMWV has a gross weight of approximately 6 600 Ibs 5 500 lbs HMMWV and 1 100 Ibs communications pallet The communications pallet should be located so that it is directly behind the rear passenger seats this was the configuration used in testing some HMMWVs still have communications pallets located in a forward position where the rear passenger seats are If a communications pallet is not located in the vehicle then provisions should be made to securely place an equi
177. uld be used depending upon the judgment of the engineer from the standpoint of the climatic region A 1 4 Fine Grained Soils Fine grained soils are those in which more than half the material by weight passes a No 200 sieve Fine grained soils are not classified on the basis of grain size distribution but according to plasticity and compressibility A 1 4 1 Silts e ML Inorganic silts and very fine sands rock flour silty or clayey fine sands or clayey silts with slight plasticity The plastic index plots below the A line and the liquid limit is less than 50 e MH Inorganic silts micaceous or diatomaceous fine sandy or silty soils plastic silts The plastic index plots below the A line and the liquid limit is more than 50 e OL Organic silts and organic silt clays of low plasticity The plastic index plots below the A line and the liquid limit is less than 50 A 1 4 2 Clays e CL Inorganic clays of low to medium plasticity gravelly clays sandy clays and silty clays lean clays The plastic index plots above the A line and the liquid limit is less than 50 e CH Inorganic clays of high plasticity fat clays The plastic index plots above the A line and the liquid limit is more than 50 e OH Organic clays of medium to high plasticity The plastic index plots below the A line and the liquid limit is more than 50 A 1 4 3 Borderline Fine Grained Soils Fine grained soils which plot in the shaded portion of the plasticity chart ar
178. um resource requirements From the mission statement or an estimate of the situation determine the minimum number of design aircraft passes that will accomplish the mission For contingency airfields that have a parallel taxiway one aircraft pass is defined as one takeoff and one landing For contingency airfields that do not possess a parallel taxiway one aircraft landing and one takeoff each count as an aircraft pass Thus if an airfield is to be designed for 100 aircraft operations landings and takeoffs the design aircraft passes would be 100 if the design includes the construction of a parallel taxiway If a parallel taxiway is not in the overall design then the design aircraft passes should be 200 Additional design passes should be incorporated if multiple aircraft movements are expected on the airfield For each additional movement expected one design aircraft pass should be added to the design traffic level 4 9 4 Traffic Area Military airfields are typically divided into traffic areas based upon the frequency and type of aircraft loading All pavement facilities of contingency airfields are classified as Type A traffic areas Type A traffic areas are pavement facilities that receive channelized traffic and the full design weight of the aircraft 4 9 5 Soil Strength The strength of the in place subgrade will determine the type of surfacing required if any and the allowable number of passes of the design aircraft The strength of th
179. umber converted into an average mean friction with the values calculated by a Bowmonk unit may be used to perform an operational check In addition this procedure can be used to determine the contingency airfield friction and C 17 RCR if a Bowmonk unit should not be available or is functioning improperly The most to least preferable vehicles for this testing are still the HMMWV six pax quad and cycle The following steps are required to perform this operational check 1 Perform safety checks 2 Review skidding procedure 3 Review Bowmonk settings and operational sections if checking Bowmonk for proper operation 4 Install Bowmonk unit in chosen vehicle if checking unit for proper operation 5 Identify a long smooth level area to perform skid test If performing this procedure in lieu of Bowmonk measurements at a contingency airfield line up at appropriate location to perform the next skid test 6 Place marker at chosen area orange cone flag etc and observer if available 7 Observer should be at marker position the same longitudinal distance down the runway but a safe distance laterally displaced 50 feet left or right of skid location 8 Select appropriate test speed considering operational equipment and safety factors Higher speeds 40 mph or greater are preferred as they are more accurate 10 Setup Bowmonk unit for normal operation if applicable 11 Begin acceleration as per normal skid procedure
180. urements of ground slope Note that the zero trimming surface does not have to be exactly horizontal but it must be flat Make the first measurement with the instrument handle nearest to you then rotate the instrument through 180 degrees and make the second measurement with the handle pointed away from you D 3 4 2 5 Adjust Clock This menu allows the time to be changed to compensate for daylight savings time On selection the minutes value will flash to indicate it can be adjusted press UP ARROW or DOWN ARROW to change then ENTER to save the new value The hours value will then flash and can be adjusted likewise The date can only be changed at the factory D 3 4 2 6 Re Calibrate Shows the latest calibration information and allows the factory distributor to re calibrate the instrument Press P to print a calibration report Calibration reports are supplied by the manufacturer when a unit is purchased or re calibrated Copies of this report should be made and stored in appropriate locations for future reference Units must be shipped back to manufacturer once a year for yearly calibration D 3 5 Operational Checks The following sections detail procedures that can be performed before or after deployment if necessary to verify proper operation of the Bowmonk unit These are recommended as predeployment activities due to the length of time and manpower required to perform these tests These tests are also useful for Atch 1 125 of 16
181. urements to RCR D 6 1 Convert Bowmonk Mean Deceleration Readings into Aircraft RCR Values This section describes the first method which is by far the most accurate Data collected with the Bowmonk can be used in Table D 7 to convert the friction measurements into an equivalent C17 RCR The mean deceleration measurements are used to calculate an overall average mean value This average value is compared to the values in column two mean and the appropriate C17 RCR value is determined D 6 2 Alternate Friction Prediction Procedures There are two alternate friction prediction procedures correlating the soil type to RCR and directly measuring the skid distance with a ground vehicle and correlating to RCR Of the two alternate procedures measuring the skid distance is more accurate and is preferred over correlating RCR to soil type only Table D 7 Stopping Friction Guidance Preliminary HUMVEE Semi Prepared Surface Condition Bowmonk Runway Reading RCR o 40 Unstabilized Visibly dry dry depth 2 gt 61 20 Cement Stabilized Visibly dry no puddles gt 61 20 Either Damp to wet N A 4 Note Average of all eight mean decel in g readings Table D 8 Correlation Between Soil Type and RCR USCS Water Soil Type Classification Content 17 RCR Well Graded Gravels GW Dry 20 Clean Sands lt 5 fines SW SP Dry 22 Clayey Sands Silty Sands gt 12 fines SC SM Dry 22 Low Plasticity Clays amp Silts CL ML Dry 2
182. valent amount of dead weight Atch 1 111 of 162 25 November 1997 sandbags water tanks etc in the same location The HMMWV should be operated with the transmission in the high range unlocked position D 2 2 Air Force Standard Six Passenger Pickup Truck six pax The six pax is a standard Air Force six passenger two or four wheel drive truck see Figure D 3 The research testing was performed with a 4WD model operated in the 2WD mode Subsequent skid tests have been performed using both the 4WD and the 2WD models with no discernible difference in the test results D 2 3 AFSOC STT Quad The Quad is a 400cc 4 wheel 4WD vehicle used on assault zones by the STTs see Figure D 4 The primary use for this vehicle is for rapid transportation of runway navigational aids and assisting in the establishment of the assault zone The quad must be operated in 2WD mode for this friction procedure D 2 4 AFSOC STT Motorcycle The motorcycle is a national stock listed Kawasaki 250cc dirt bike see Figure D 4 The motorcycle is modified with infra red headlights rifle racks and equipment racks Figure D 4 shows the motorcycle and the quad performing friction tests on a contingency airfield Figure D 2 HMMWV with Communications Pallet Performing Skid Test Atch 1 112 of 162 25 November 1997 Figure D 3 Air Force 6 Pax Truck Performing Skid Test with C 17 in Background Figure D 4 Motorcycle and Quad Performing F
183. ve on a pavement The PCN is a number that expresses the capability of a pavement to support aircraft operations ACNs for the C 17 for maximum gross weight maximum operating and minimum operating weight for contingency and training operations on semi prepared airfields are shown in the following table Figure 2 3 shows ACN values for any C 17 weight A more detailed discussion of the ACN PCN procedure and CAN values for the C 27 and C 130 are contained in Appendix C Aircraft Classification Numbers Subgrade Strength Aircraft High Medium Low Ultra Low Wt Kips 13 A CBR z9 13 B CBRz4 8 C CBR 4 D 586 68 75 85 109 447 47 53 60 77 279 21 28 30 37 110 Subgrade Strength 100 A High CBR 13 90 B Medium 9 13 C Low 24 8 80 D Ultra Low CBR lt 4 z 70 T gt 60 4 10 250 300 350 400 450 500 550 600 Aircraft Gross Weight kips Figure 2 3 Aircraft Classification Number for C 17 for Contingency Operations Atch 1 9 of 162 25 November 1997 Turning Criteria Experience has shown that tight turns on semi prepared airfields damage the surface and produce foreign object damage Therefore star turns are not recommended The criteria in figure 2 4 are the basis for the hammerhead dimensions contained in this document Type Steering Effective Tire Slippage Minimum Taxiing Radii Feet Turn Input Turn Angle Angle X Y A R3 R4 RH5 R6 Optimal 65 max 52 8 6
184. water until it can be molded or shaped without sticking to the fingers This moisture content is referred to as being just below the sticky limit Prepare a nonabsorbent rolling surface by placing a sheet of glass or heavy wax paper on a flat or level support then shape the sample into an elongated cylinder and roll the prepared soil cylinder on the surface rapidly into a thread approximately 1 8 inch in diameter If the moist soil rolls into a thread it has some plasticity Atch 1 52 of 162 25 November 1997 The number of times it can be rolled into a thread without crumbling is a measure of the degree of plasticity Soils that cannot be rolled are nonplastic e Results Soil may be molded into a ball or cylinder and deformed under very firm finger pressure without crumbling or cracking High plasticity CH Soil may be molded but it cracks or crumbles under finger pressure Medium plasticity CL Soil cannot be lumped into a ball or cylinder without breaking up Low plasticity CL ML or MH Soil forms a soft spongy ball or thread when molded Organic material OL or OH Soil cannot be rolled into a thread at any moisture content Nonplastic soil ML or MH The higher the soil is on the plasticity chart the stiffer the threads are as they dry out and the tougher the lumps are if the soil is remolded after rolling Note Micaceous silts and sands can be rolled due to the flaky nature of the mica
185. wet and add material if necessary Rescarify if material is added Grade to a proper cross section Rewet as needed Compact to obtain the optimum density Repeat steps 6 and 7 if necessary to obtain the optimum density with the compaction equipment available N 97 STABILIZED LAYER FAILURE Procedure One 1 Determine the stabilizing additive and amounts 2 Pulverize 3 Add material if necessary 4 Obtain optimum moisture content 5 Add the identical stabilizing additive 6 Mixthe materials Be sure to scarify at least 2 inches into the existing stabilized material to achieve a proper cold joint both below and around the repair area 7 Grade to a proper cross section 8 Add additional water if necessary to obtain optimum moisture content 9 Grade and compact in lifts to obtain the optimum density 10 Check the cold joints for proper adhesion with a pneumatic roller if available 11 If failure is evident repeat steps 6 10 Procedure Two 1 Remove all failed material 2 up repair stabilized material on site 3 Follow procedure in TM 5 822 7 Appendix D page D 11 See TM 5 822 7 Appendix D page D 11 for specific guidance Atch 1 81 of 162 25 November 1997 APPENDIX C Structural Evaluation Procedures for Contingency Operations C 1 Introduction This appendix presents the basic criteria and procedures used to determine the structural suitability or lo
186. ywood boxes to use the units with the six pax quad and cycle The box for the six pax should be constructed so that it will hold the Bowmonk unit securely and allow the unit to be strapped in level on the front seat using the middle seat belt Boxes for the quad and cycle should be constructed so that they hold the units firmly so the units can be slid in and out of the boxes and these boxes should be attached to the equipment racks with plastic wire zip ties Bungee cord should be placed across the Atch 1 114 of 162 25 November 1997 top of the boxes and units to hold them securely in place In the HMMWV the unit should be placed on the level platform front and center between the driver and passenger seat and secured in a forward and down position with bungee cords The unit must be placed so that the arrows on its lid are pointing forward in the direction of travel to within 10 degrees The unit does need to be securely fastened so that once it is installed it will maintain its original position throughout the field tests particularly with no forward or backward movement possible The recommended mounting locations for each vehicle are shown in Table D 2 Figure D 6 provides a look at how the Bowmonk is installed in a HMMWV Table D 2 Recommended Mounting Locations for Bowmonk Vehicle Type Recommended Mounting Location Six Pax On the seat by the driver HMMWV Between driver and passenger secured to platform Quad On front equip
187. zed Streaks or stripes are indications that mixing has not been thorough and weak areas will result if the mixing is not continued Add water as needed to maintain optimum Atch 1 28 of 162 25 November 1997 moisture content If the weather is dry and windy moisture will be lost rapidly during mixing requiring more frequent additions of water 4 8 3 4 Grade Control If the material must be stabilized in place it should be brought to the final grade and the final elevation plus an additional thickness for the expected reduction due to compaction after pulverizing and before the addition of the stabilizing agent The addition of the stabilizing agent and subsequent mixing should not significantly affect the grades and elevations A reduction of 10 to 30 percent in layer thickness can be expected due to compaction A small trial section should be constructed to determine the loss in thickness that can be expected for the local conditions It is important that the materials be placed as close as possible to final grades prior to compaction Minor adjustments in the grades following initial compaction can result in thin layers of material that may delaminate and cause potential FOD and roughness problems Once compaction is begun the grades should not be adjusted If the grades have to be adjusted a minimum depth of six inches of material should be pulva mixed the grade adjusted and then compaction begun again 4 8 3 5 Compaction Compa

ETL 97-9 Criteria and Guidance for C

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