ABBREVIATED AVIATION ACCIDENT REPORT (AAAR)
Source FINAL
1. Case Number 1a. Date of Accident 1b. Time 1c. Aircraft Serial Number 2a. Classification 2b. Category
19800225010 Feb 25 1980 1610 6815993 A FLIGHT
3. Type of Aircraft 4. Period Of Day 5. No Acft Involved 6. Nearest Installation
CH47C DAY 1 GE760 - SCHWABISCH HALL, FRG
7. Accident Location a. Off Post b. Not On Airfield e. GERMANY
8. Organization Involved in Accident
Unit UIC7 UIC6 UIC5 UIC4 UIC3 UIC2 MACOM Station
WC5LAA WDLKFF WAAFFF WAT8FF W0ANAA GE760
180AVCO 223AVBN 11AVGP 7 CORPS USAREUR SCHWABISCH HALL, FRG
9. Organization Accountable for Accident
WC5LAA WDLKFF WAAFFF WAT8FF W0ANAA GE760
180AVCO 223AVBN 11AVGP 7 CORPS USAREUR SCHWABISCH HALL, FRG
10. Estimated Accident Cost
a. Total Loss b. Aircraft Damage c. Man Hrs d. Man Hrs Cost e. Other Mil Damage f. Civilian Damage
Yes $2956896 0 $0 $0 $0
g. Injury h. Total This Aircraft i. Total Accident
$898000 $3854896 $3854896
11. General Data
a. Mission S/M b. Flight Plan c. Data Recorder
S - SERVICE VFR
02 - TEST
d. Night Vision e. Fire f. Fluid Spillage g. Field Training
NONE Yes
12. Flight Data
a. Emergency Duration Phase of Operation
.1 G - CRUISE
AGL KIAS Weight Overgross
120 27807
b. Termination Duration Phase of Operation
.1 G - CRUISE
AGL KIAS Weight Overgross
27807
13. Type Event
37 - Inflight Breakup - -
14. Accident Cause Factors Human Error Material Failure Environmental
UNKNOWN DEFINITE NO
15. Summary
SUMMARY: AIRCRAFT WAS ON A MAINTENANCE TEST FLIGHT FOR INSTALLATION OF THE #1 ENGINE. AT APPROXIMATELY 500 FEET AGL, WHILE CONDUCTING THE TURBINE ENGINE ANALYSIS CHECK (TEAC), THE COMBINING TRANSMISSION PHASING MECHANISM DECOUPLED, RESULTING IN ROTOR MESH. THE FORWARD AND AFT TRANSMISSION AND ROTOR SYSTEMS SEPARATED IN FLIGHT, AND THE AIRCRAFT SUBSEQUENTLY CRASHED INTO A PINE FOREST. THE AIRCRAFT WAS TOTALLY DESTROYED, AND ALL FIVE OCCUPANTS SUSTAINED FATAL INJUREIS DURING IMPACT.
16. COMPONENT AND PART FAILURE/MALFUNCTION DATA
Major Component Information
a. Nomenclature b. Type/Design/Series c. Part Number d. NSN e. MFG Code f. Part Serial No
COMB TRANSMISSION 114D52008 1615010547272 77272 A81278
Part Information
a. Nomenclature c. Part Number d. NSN e. MFG Code f. Part Serial No
BOLT AN17415 5306001801739 88044
g. Cause Failure Functional Group
Material Maintenance Design Manufacture 04 - ROTOR AND TRANSMISSION 13 - COMBINING TRANSMISSION
DEFINITELY NONE SUSPECTED 03 - LINKAGE 35 - TERMINAL
Type Failure Cause Failure
070 - BROKEN S010 - CREEP FROM OVERSTRESS 999 - UNDETERMINED -
17. ENVIRONMENTAL
a. General (1) IMC (2) VMC (3) Unknown
b. Environmental Conditions
1. Weather Conditions 2. Other Conditions
(a) Hail (a) Animals
(b) Sleet (b) Fowl
(c) Fog (c) Surface
(d) Drizzle (d) Noise
(e) Rain (e) Chemicals
(f) Snow (f) Radiation
(g) Lightning (g) Glare
(h) Thunderstorm (h) FOD
(i) Gusty Winds (i) Temperature
(j) Freezing Rain (j) Vibration
(k) Other (k) Dust
c. Aircraft Icing No Yes d. Turbulence No Yes
19. MOON ILLUMINATION DATA
a. Above Horizon b. Visible c. Degrees Above Horizon d. Percent Illumination e. Clock Position
No Yes No Yes
20. WIRE STRIKE DATA
a. Wire Strike b. WSPS Installed c. WSPS Engaged
No Yes No Yes No Yes
d. WSPS Cut Wire e. WSPS Functioned f. Wires Struck
No Yes No Yes Number wires 0 Dia.(inches)
21. PERSONNEL DATA
Person # 1 c. Grade d. Sex e. Duty
E4 MALE CE - CREW CHIEF/FLIGHT ENGINEER
f. SVC g. UIC h. Role i. On Controls
A - ACTIVE ARMY WC5LAA U - UNKNOWN No Yes
j. Lab Test k. Hrs Slept 24 l. Hrs Worked 24 m. Hrs Flown 24
Yes No
n. RL o. FAC p. Injury q. MTDS Total Flt Hrs
1 2 3 1 2 3 A - FATAL 0
Person # 2 c. Grade d. Sex e. Duty
E5 MALE IE - INSTRUMENT FLIGHT EXAMINER
f. SVC g. UIC h. Role i. On Controls
A - ACTIVE ARMY WC5LAA U - UNKNOWN No Yes
j. Lab Test k. Hrs Slept 24 l. Hrs Worked 24 m. Hrs Flown 24
Yes No
n. RL o. FAC p. Injury q. MTDS Total Flt Hrs
1 2 3 1 2 3 A - FATAL 0
Person # 3 c. Grade d. Sex e. Duty
E4 MALE PPM - POWER PLANT MECHANIC
f. SVC g. UIC h. Role i. On Controls
A - ACTIVE ARMY WC5LAA U - UNKNOWN No Yes
j. Lab Test k. Hrs Slept 24 l. Hrs Worked 24 m. Hrs Flown 24
Yes No
n. RL o. FAC p. Injury q. MTDS Total Flt Hrs
1 2 3 1 2 3 A - FATAL 0
Person # 4 c. Grade d. Sex e. Duty
W3 MALE PI - PILOT
f. SVC g. UIC h. Role i. On Controls
A - ACTIVE ARMY WC5LAA N - NONE No Yes
j. Lab Test k. Hrs Slept 24 l. Hrs Worked 24 m. Hrs Flown 24
Yes No 7 8 0
n. RL o. FAC p. Injury q. MTDS Total Flt Hrs
1 2 3 1 2 3 A - FATAL 319
Person # 5 c. Grade d. Sex e. Duty
W3 MALE MP - MAINTENANCE PILOT
f. SVC g. UIC h. Role i. On Controls
A - ACTIVE ARMY WC5LAA N - NONE No Yes
j. Lab Test k. Hrs Slept 24 l. Hrs Worked 24 m. Hrs Flown 24
Yes No 0 8 0
n. RL o. FAC p. Injury q. MTDS Total Flt Hrs
1 2 3 1 2 3 A - FATAL 1002
22. IMPACT/PROTECTIVE/ESCAPE/SURVIVAL/RESCUE DATA
a. Aircraft Space Compromised b. Escape/Survival Difficulties c. Protective/Restraint Equip Functioned
No Yes No Yes No Yes
24. FINDINGS AND RECOMMENDATIONS
Findings
FINDING (MATERIEL FAILURE - CONTRIBUTING): DURING A MAINTENANCE TEST FLIGHT FOR INSTALLATION OF THE #1 ENGINE, THE COMBINING TRANSMISSION PHASING ARM ATTACHING BOLT SHEARED AND ALLOWED THE INTERNAL PHASING MECHANISM TO DECOUPLE. THIS FAILURE RESULTED IN A LOSS OF POWER TO THE FORWARD MAIN TRANSMISSION AND SUBSEQUENT MESHING OF THE FORWARD AND AFT ROTOR SYSTEMS. THE BOLT SHEARED DUE TO UNDEFINED FORCES GENERATED WITHIN HE COMBINING TRANSMISSION WHICH WERE TRANSMITTED THROUGH THE PHASING MECHANISM TO THE BOLT. PRELIMINARY CCAD USASC 80-314 CH-47C 68-15993: 1. ANALYSIS REVEALED A FAILED OR SEPARATED 1/4 INCH BOLT P/N 174-15 IN HE DEPHASING ARM ASSY OF THE COMBINING XMSN (REF FIG 76 ITEM 118B PG 468 TM 55-1520-209-23P DATED APR 77). 2. THE BOLT HEAD & NUT AS MISSING AND IT APPEARED THAT THE BOLT HAD FAILED FROM SHEAR OVERSTRESS, CAUSE UNKNOWN. 3. THIS FAILED BOLT, P/N AN 174-15, PROBABLY CAUSED A MALFUNCTION OF THE DEPHASING COUPLING BY ALLOWING THE XMSN TO BECOME PREMATURELY DISENGAGED. 4. PRELIMINARY METALLURGICAL REPT INDICATES THAT BOLT (P/N AN 174-15) FAILED THROUGH DOUBLE SHEAR MECHANISMS AT THE DEPHASING LEER/HOLLOW PIN INTERFACE. THE SHEARED BOLT'S SURFACE METAL FLOW AND ITS DISPLACEMENT IN THE HOLLOW PIN INDICATED THE BOLT WAS SHEARED INTHE CCW DIRECTION AND RESPECTIVELY, THE HOLLOW PIN WAS ROTATED INTHE CLOCKWISE DIRECTION. 5. NO MATERIAL DISCREPANCIES WERE NOTED. 6. VISUAL AND BINOCULAR EXAMINATION OF BLADE (S/N A2-2841) FRACTURE SURFACES INDICATES OVERSTRESS MECHANISMS. NO EVIDENCE OF A PROGRESSIVE TYPE FAILURE WAS NOTED. 7. ANALYSIS IS CONTING. ESTIMATED DATE FOR COMPLETION OF FINAL REPT IS 11 APR 80. FINAL CCAD USASC 80-314 CH-47C 68-15993 CONCLUSIONS: A. A FAILED 1/4 INCH BOLT IN THE DEPHASING ARM ASSEMBLY OF THE COMBINING XMSN PROBABLY CAUSED A MALFUNCTION OF THE DEPHASING COUPLING BY ALLOWING THE COMBINING TRANSMISSION TO BECOME PREMATURELY DISENGAGED. THE BOLT APPARENTLY FAILED FROM OVERSTRESS MECHANISMS, CAUSE UNKNOWN. NO EVIDENCE OF PROGRESSIVE TYPE FAILURE WAS NOTED. B. METALLURGICAL BRANCH REPT INDICATED THAT THE DEPHASING LEVER BOLT (AN 174-15) FAILED THROUGH DOUBLE SHEAR MECHANISMS AT THE DEPHASING LEVER/HOLLOW PIN INTERFACE. C. ANALYSIS OF BOTH ENGINES REVEALED NO MATERIAL DISCREPANCIES WHICH COULD HAVE CONTRIBUTED TO PREMATURE FAILURE. THE ENGINES WERE PROBABLY OPERATING AT NORMAL OPERATING (RPM) RANGE AT THE TIME OF MISHAP BASED ON THE FOLLOWING: METAL PARTICLES FUSED TO THE URBINE COMPONENTS, HIGH SPEED RUB ON HE POWER SHAFTS AND INSIDE DIAMETER OF HE COMPRESSOR SHAFTS, AND AN EVENLY DISTRIBUTION OF INGESTED DIRT THROUGHOUT THE ENGINES. D. ESTIMATED OF TORQUE (POWER) BEING PRODUCED BY THE ENGINES AT TIME OF MISHAP WAS INDETERMINATE. E. ANALYSIS ALSO FAILED TO DISCLOSE ANY PPEBREAKUP MALFUNCTION OF OTHER MAJOR COMPONENTS OR ASSOCIATED PARTS RECEIVED (AS EXHIBITS) FROM CH-47C, S/N 68-15993. ALL DAMAGE(S) NOTED WERE CONSIDERED SECONDARY, THE RESULTS OF OVERSTRESS CAUSED BY IMPACT. RECOMMENDAATIONS: SINCE HE CAUSE FOR BOLT (AN 174-15) FAILURE IS NOT KNOWN, RECOMMEND THAT THE DEPHASING CAPABILITIES OF ALL CH-47 SERIES COMBINING XMSN ASSEMBLIES BE IMMEDIATELPY DISCONTINUED AND TO UTILIZE A SUITABLE LOCKOUT OR INTER-CONNECTING SLEEVE OR COLLAR BETWEEN THE BALANCED SHAFT AND THE OUTPUT SHAFT TO PRECLUDE RECURRENCE.
Recommendations
RECOMMMENDATION: A. UNIT LEVEL ACTIONS. NONE. B. HIGHER COMMAND ACTINS. NONE. C. ARMY LEVEL ACTIONS (1) TSARCOM DEFINE THE CAUSE FOR BOLT FAILURE/TRANSMISSION DECOUPLING AND TAKE APPROPRIATE ACTION TO ELIMINATE THE PROBLEM. (2) UNITED STATES SAFETY CENTER (USASC) CONTINUE TO SUPPORT THE ESTABLISHMENT AND APPROVAL OF THE REQUIREMENT FOR AN ACCIDENT INFORMATION RETRIEVAL SYSTEM (AIRS) ON U.S. ARMY AIRCRAFT TO ENHANCE MISHAP INVESTIGATION. STATEMENT OF REVIEWING OFFICIAL CONCUR WITH THE FINDINGS OF THE U.S. ARMY AIRCRAFT ACCIDENT REPORT CONCERNING CH-47C, SERIAL NUMBER 68-15993.