ICS 2009 Tacoma - HD Neubert & Associates, Inc.
Contents
1. CINIERBALNEE SYSTEM 400 I 1 1 INTRI CALE NOSE UP 36 Stabilator Skin Thickness Variations 2 000 Line I 01342 ALL SINGLES EXCEPT 400 040 THINS 132 400 Q20 ALL SINGLES EXCEPT 400 125 TWINS 1 R 032 400 1 400 1 TWENS 1 1 1 1 37 Torque Tube Dimensions All Singles except 400 2 3115 OD x 105 wall thickness 400 5 2 3115 OD x 161 wall thickness Twins m 2 3115 OD x 161 wall thickness GJ 5 839E6 singles vs 8 316E6 Twins 400 Torsional Stiffness is 30 less on singles than Twins 38 Fatigue Crack Growth Initial flaw required typically 001 inches Stress level including concentration effects must be sufficient to cause crack to grow amp f stress level is below crack growth threshold crack will not grow Creating radius at bore intersections reduces concentration effects amp Verify at 10 year intervals in conjunction with SL 1160 inspection period 39 Hypothesis of Fatigue Failure in Horn Sharp edge between primary amp secondary bores gives a 5 6 stress concentration factor amp Play in trim tab causes stabilator to respond to high frequency impulses from propeller Looseness of control cables allows counterbalance tube and weight to oscillate amp High frequency oscillations create bending stress in horn amplified 5 6 x at the bore intersections Crackin2. 1500 0 T 2 a lt o a 1000 0 500 0 0 0 010 20 0 40 0 60 0 80 0 100 0 500 0 75 LOAD 27 Load Case 3 Strains LEFT STABILZER STRAIN GAGES 1 6 STRAIN ic 3000 0 4000 0 LOAD 28 Load Case 3 Displacements DISPLACEMENTS LVDT WEST UPPER 4 EAST LOWER WEST LOWER EAST UPPER X PRED E UP DISPLACEMENT 001 LOAD 29 Summary An unserviceable torque assembly was re furbished and life cycle tested to DLL and subsequently to DUL Strain and displacement measurements show that during the life cycle testing the torque tube exhibited linear elastic characteristics amp Corrosion on a torque tube if found is a Maintenance issue These tests show conclusively that a corroded torque tube is not an Airworthiness Issue 30 Conclusions SAIB CE 04 88 is now replaced by Piper Service Letter 1160 he Service Letter is not mandatory for Part 91 operations The Service Letter requires torque tube inspection at 10 year intervals amp A corroded torque tube is shown to be Airworthy The Atlanta ACO has no intentions of issuing an AD on the torque tube based on SL 1160 31 Counterbalance Horn Basic Data 4 Part Number 20397 00 Common to all Comanche Models 24 30 39 400 amp Aluminum alloy 2014 T6 forging amp Sliding fit to torque tube 001 tolerance AN 175 33A Bolts
3. looseness in trim drum tab system f Cracked expected failure at 5000 hours Ground run data shows vibration of counterbalance tube at all cruise rpm s amp There are no Piper SL pending AD s or SAIB THIS IS A TYPE CLUB INVESTIGATION FAILURE OF HORN IN FLIGHT WILL BE FATAL 56
4. 19Y 5065P 7818Y 543AS 842PS 6518P Model PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 30 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 30 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 24 PA 30 PA 24 PA 30 PA 30 PA 24 PA 24 PA 24 PA 30 PA 24 PA 24 PA 30 PA 24 PA 30 PA 24 PA 24 PA 24 Brief Description Lost Elec Pwr Gear Up Lng Ft Smith AR Gear vvould not extend Gear Up Lng Prosser VVA Smell smoke Manual Extend Collapse Moab UT Gear Dun No Light Collapse Pell City AL Practicing Approaches Gear Up Lng Georgetown KY Collapse on Landing Atlantic City NJ Gear Up Lng Gulf Shores AL Gear Up Lng Glendale AZ Gear 9 45 Gear Collapse Portland ME Nosegear Collapse San Angelo TX Gear Colllapse Enterprise AL Veered right Right MLG collapse Prescott AZ Eng Problems Gear collapse Colo Springs CO Gear Up Lng Pipestone MN Right MLG Collapse Rome GA Gear Collapse Lumberton NC Right MLG hit on T O Gear Collapse Waupaca WI Elec Failure Gear Up Lng Watsonville CA Right MLG Collapse Pueblo CO Would not extend Gear Up Lng Ft Worth TX Nosegear Collapse Sedona AZ Hard Lng Damage to Nosegear amp wings Pt Clinton OH Gear Collapse Muskogee OK Nosegear Collapse Minneapolis MN Gear Collapse New Bedford MA Left wheel came off Winder GA Elec Failure Gear Up Lng Millinocket ME Left MLG did not lock gear collapse Manassas VA Elec Failure Gear C
5. Aging Aircraft Concerns on Comanche Airplanes ICS National Convention Tacoma WA 15 August 2007 Hans Neubert Copyright 2007 Hans Neubert Pages 1 through 56 Current Fleet Problems Landing Gear Collapse Torque Tube Corrosion Cracking in Torque Tube Horns Limited Availability of Parts Landing Gear Incident Data www faa gov data statistics accident incident preliminary data 4 Data for all GA events by Gear Up Landing S Gear Collapse collected for nearly 5 years 4 Data for all Comanche events by Gear Up Landing amp Gear Collapse retained as subset on Excel spreadsheet Approximately 2 per day for all GA Approximately 2 per month for all Comanche s All Landing Gear Data 1 Jan 02 27 Oct 07 1402 06 GEAL UP g ut hus of JAM 220 Z 7 Date Zooz 8255 ose ue Cod Shy Free 2006 2056 Liv Fe J 30 4 72 Mose 4 ENA CopeASEd o n ST Reel Fe SoS 7087 10 24 losr Ete Lb Gene Fl Sos ir 42 3 JAM 045 uL PA 34 Mose Gehe Cu d eh on Lily 7Weo f wih Je 70 t 2 0 Liles Gent Uf 4 d y MO 5 2603v 022 By Tug UNSAFE GEAL Gede APE Nevk S74 hal 23 WG 020 Ase 0 Ly Duds Tv 528 EwP Degkur Nose GEAR LLAS pag Rou 2 du 6 P 8233 GcfE of 1J nbs m GEMA FADUCAM LY Jal 287680 82 Gina ond Lug
6. ET H ip A 357 H M0 20 Corhhe od LNG SZ pd T7532V 0077 Wt Geht DP letune CA 444 201 HR 020 Miu 7 647 Cogs vj Gate GAR Cott A Sc 4 2 al APF 6337 Mind Gene Srode Mose Sene Dowd LNG SLE 3 Ja f SS P PA24 GENK Woden Ex rea GCbe UP 146 Posez wi 2 44 d72 05 46 Gena Op Pos of SaaS adasP Aiso e4oco Auwce Nose GEAR Pui GAL de 2 44 4 92028 0172 P lag Arne fue han Sum lun 2 4 2 444 95STT avo Qent UP 14 Arn mI s Mad 2giwA MUZ L eqe Ale Lumen Geata Ky Comanche Specific Gear Related Problems Comanche Specific Gear Related Problems Date 1 1 2002 1 13 2002 1 19 2002 2 9 2002 2 24 2002 2 23 2002 2 28 2002 3 16 2002 4 7 2002 4 14 2002 4 17 2002 4 21 2002 4 29 2002 4 29 2002 5 6 2002 5 7 2002 5 26 2002 6 21 2002 6 30 2002 7 4 2002 7 15 2002 7 20 2002 7 26 2002 8 14 2002 8 19 2002 9 7 2002 10 19 2002 10 20 2002 11 7 2002 11 13 2002 11 13 2002 12 14 2002 12 15 2002 1 4 2003 1 12 2003 1 14 2003 2 19 2003 2 13 2003 3 7 2003 3 15 2003 3 16 2003 N Number 7084P 5511P 7176P 7807P 6202P 9055P 6610P 6518P 9140P 6909P 7818Y 7401P 7366P 7961P 7953P 7224P 250LJ 8974Y 6027P 400BK 767WP 5227P 5639P 144TL 9030P 7817Y 7875P 2VQ 7349Y 7390P 8382P 5582P 948SB 6404P 6080P 86
7. d and displacement Transmission is disconnected amp Plot up results Test of Over Center Force and Movement Transmission disconnected Results of Tests Vertical Load pounds 0 1 Untoggle Loads amp Displacement 0 15 0 2 Vertical Movement inches 0 25 Nose Gear Main Gear 11 Summary of Gear Collapse Suggestions Maintenance Maintenance Maintenance amp Replace circuit breaker and solenoid at next annual Check cable conduit preload amp Minimize gear cycles in short time period Lubricate ALL zerk fittings remove excess amp Check log book for 1000 hr AD gear compliance 12 Torque Tube Background Data Corrosion has been observed between the torque tube and the attaching bolts m Piper Service Letters 667A and 772 m Advisory Directive 74 13 10 issued FAA Inspection requires replacement of existing attaching stabilator bolts with corrosion resistant bolts m Replacement of bolts with CRES bolts is terminating action of the AD 13 ICS Action Plan Fearing that a potentially devastating AD could result from the SAIB 1C9 action included m Testimonial letters responding to SAIB from 9 recognized Comanche specialty repair facilities Initiated owners survey of inspection results on both the Delphi and ICS site m Received from Altus an unserviceable torque tube assembly for structural load testing 14 Testimonlal Letter Summa
8. ered Long AN4 bolt Required Heat Horn to 200F in Air Circulating Oven Caution Do not use flame or torch Chill Torque Tube to OF in Freezer Install Rotation Limiter first Slide tube into horn align transverse bolt holes with AN4 bolt Allow to cool to RT Remove AN4 bolt 6 9 YOU WILL HAVE 5 SECONDS TO GET I T RICHT 53 Recommendations SINGLES WI TH LESS THAN 3500 HOURS un Disassemble torque tube assembly at next annual Do not remove counterbalance tube inspect horn for cracks if none found then Create 03 radius at bore intersections Polish radius and bore with 600 grit paper Repack bearings un Re assemble and make log book entry of inspection Repeat at next SL 1160 Compliance inspection period 54 Recommendations SINGLES WI TH MORE THAN 3500 HOURS un Disassemble torque tube assembly within 50 hours a Do not remove counterbalance tube unless horn is cracked inspect horn for cracks at bore intersections If Cracks found locate serviceable horn Piper part PMA part then Create 03 radius at bore intersections Polish radius and bore with 600 grit paper Repack bearings Re assemble and make log book entry of inspection amp replacement Repeat at next SL 1160 Compliance inspection period 55 Summary of Information to Date Horn cracking found on SOME singles Related to Time In Service gt 3500 hours m Related to
9. g migrates to aft side of horn after forward portion cracks and looses circumferential stiffness 40 P Samples of Cracked Horns Investigation to Isolate Cause Determine frequency of counterbalance weight at various rpm s with snug amp loose trim tab amp Determine if propeller impulse frequency corresponds to weight frequency Determine stresses in horn due to a Frequency response m Bolt torque a Shrink fit of counterbalance tube 42 Vibration Test Set up Accelerometer fabricated using electret microphone Prop pulses measured with pitot tube pressure transducer Data taken with oscilloscope captured to video camera Stabilator position restrained using split foam cover Movement of counterbalance weight measured using Moire Fringe method and dial indicator captured to 2 video camera Measurements at 2100 2200 2300 2400 2500 rpm Excessive trim tab play simulated with undersized tab bushing 43 Vibration Data to Date Counterbalance weight oscillation using dial indicator m Plus minus 010 inches all rpm s Data from 7 7 07 o Response from accelerometer pitot tube setup a No data collected Check out electronics and retry amp When operational perform flight data collection m Dial indicator data from mini cam 44 Preliminary Vibration Data Finite Element Analysis CAD model supplied by Garrett Sager I CS member on 7 11 07 from fur
10. nished reversed engineering drawing Import Iges file into m Strand 7 FEA software m Nastran FEA software Perform static and dynamic analysis Bolt torque on horn interference fit to balance tube Frequency response due to vibration data Modes and mode shapes 46 Horn Drawin FKGUIG CUCA IR INC u m FEIN TI 3 5 N AUB8IY N L Neubert E cac ites MEL P rata Streel kade i Li EI 1714 A Hr HORN TEE I PIPER CENANEHE SERIES we 2 p i 47 Horn 3D Rendering from CAD file Type Club Support Harley McGatha reports Piper willingness to fabricate new production parts new tooling needed m Price and delivery unknown m Pricing data collected announcement soon amp Fabricate New Production units via PMA by denticality Horn has been reverse engineered Critical dimensions are from Piper drawing 49 New PMA Horn based on Piper Horn Removal amp Replacement of Counterbalance Tube Removal requires a push extraction fixture amp nsertion requires an alignment fixture Heat Horn by convective oven Chill Counterbalance tube in freezer m Tapered ANA bolt to align counterbalance tube hole to horn hole 51 Disassembly of Counterbalance Tube Arbor Press Required Denny Haskin s Fixture Neubert Fixture 52 Insertion of Counterbalance Tube Alignment Fixture Required Alignment Tap
11. not found any evidence of corrosion on the torque tube as 15 pictured in SAIB CE 04 08 amples of Torque Tube Corrosion 00000 ses 5 5 pete 2s SUSUR xk he 16 Samples of Torque Tube Corrosion Torque Tube Test Specimen PA 24 250 unserviceable unit received from Altus amp Torque Tube cleaned up using 180 grit media Precise measurements made after clean up Coated with zinc chromate and paint Adapter fittings load reaction fittings and base plate fabricated 18 Initial Condition Surface Pitting after Cleanup 20 Strain Gaged Specimen 1 Load Condition Selection Select symmetrical pull up at forward CG at 227 mph CAS Vne m Largest tail down load at 2000 Ib and 5 9 fwd cg 24 260 m Tail Down Load 1753 ib at 3 8g Design Limit Load m Moment S Shear satisfied at 4296 semi span amp Torque Load from CAR3 Part 23 a Maximum control wheel pull load 200 Ib m Torque 5600 in Ib at 3 8g Design Limit Load amp Bending and Torque Conditions Combined Load is offset from Torque Tube centerline by 3 2 inches m Load Condition covers all single models except 400 s 22 Test Setup 25 Test Setup 24 Test Setup 25 Load Case 1 Load LOADS vs 165 STABILIZER REACTION LOAD Ibs LOAD 26 Load Case 3 Loads LOADS 096 vs Ibs lt STABILIZER REACTION
12. ollapse Panama City FL Gear Up Lng Front Range CO Gear Up Lng Borrego Springs CA Gear Collapse Fayetteville NC Malfunction Lng on road Jackson MI Gear Up Lng Mertle Beach SC Gear Up Lng Honolulu HI Elec Failure Gear Up Lng Martinsburg PA Gear Up Lng Toms River NJ Gear Collapse Enterprise AL Gear Collapse Ft Myers FL Eng Probs Gear Up Lng Williams AZ Gear Up Lng Glendale AZ that s twice see 3 16 02 Landing Gear Collapse Causes Maintenance Neglect m Worn out parts Insufficient lubrication m Misadjusted switches fatigued wires m Excessive friction in gear cables and bearings m High amperage draw on motor and solenoids improper rigging and cable preload m Main gear pivot fitting amp nose gear clevis failure 9 Vagueness in Service Manual m Preload on cables not well written Landing Gear Overcenter Positions Adjustment of Down Limit Switches Service Manual Twin Paragraph 7 44 d Items 3 amp 4 m 3 Disconnect the retraction transmission by pulling up on the release lever and manually retracting the landing gear using the emergency extension lever 4 At the point where the green light goes out apply reward pressure on the nose gear and inward pressure on the main gear The gear should not unlock Evaluation of Gear Down Pressure amp Simple set up using bathroom scale jack long stick and dial indicator Push up at pivot point 4 Measure loa
13. ry Johnston Aircraft Service Dave Johnston Clifton Aero Tim Talley Penn Air Inc Dan Claycomb Liebfried Aviation Inc Andy Liebfried Swift Aviation Services August Mazzella Squire Aircraft Inc Bob Squire FACILITY REPRESENTATIVE VVebco Aircraft Bob Weber Aircraft Engineering Inc Bill Turley Iliff Aircraft Repair amp Service Charles lliff FINDINGS OF CORROSION I have reviewed SAIB CE 04 08 and have never encountered anything remotely similar to what these pictures show In some instances some corrosion found but never to the extent displayed in the SAIB We have never found any serious amount of corrosion We have never seen experienced or heard of the amount of corrosion shown in the pictures accompanying the SAIB We have not found on our inspections the severe rust pits shown in the SAIB on the O D of the stabilator torque tube We find corrosion but none that could be considered unairworthy The difficulty in a re occurring inspection is that disassembly will provide more damage at the hands of inexperienced technicians than a quality process and treatment for the tube on a one time or long term inspection basis We have never discovered as extensive corrosion as depicted and feel that as repetitive an inspection would be unnecessary and may cause more damage to the area outweighing the benefit While doing an annual inspection always check all components of the empennage and have
14. through torque tube Reamed fit AN 174 22A Bolts through counterbalance tube Reamed fit Counterbalance tube is a press fit into horn 0015 maximum interference 32 The Problem amp First reported by Denny Haskins in Mar 07 Flyer amp nternal cracking initiating at intersection edge of Primary and Secondary bores Average TIS when cracking is observed 3500 hours Expected TIS when failure is expected 5000 hours Observed to occur on Singles only 180 250 260 NOT ALL SINGLES HAVE SHOWN SIGNS OF HORN CRACKI NG 33 So Why are Some Horns Cracking Believed to be due to Maintenance Neglect caused by A Excessive Trim Tab Movement m Trim Drum vertical play Rod End ball socket play Trim Tab bushings bolt play amp B Control Cable tension incorrectly adjusted Maximum Tab Movement 076 inches 050 recommended Control Cable Pre Tension 22 pounds 24 recommended 34 Why Only 180 250 260 Singles Significant differences in design to Twins 400 amp Significant differences in balance to Twins 400 amp Prop wash inboard amp Thinner torque tube wall thickness Smaller Stabilator attachment bolt size amp Thinner Stabilator skin thickness amp Different trim drum support structure 35 Counterbalance Arm and Weight C CONTROL CABLE NISE DOWN 1 I COLNTERBALANCE SYSTEM SINGLES COUNTERBALANCE SYSTEM TWINS il il Y
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