# Accident 19980616013669A: Hughes 369HS, Pacific Ocean, American Samoa, June 16, 1998 - Type: FAA accident report (Accident/Incident Data System), as reported - Date: June 16, 1998, 14:00 local time - Place: Pacific Ocean, American Samoa - Airport: Pacific Ocean - Damage: Destroyed - Phase of flight: To Vertical (Helicopter Only) - Operating rules: General operating rules (Part 91) - Aircraft: N95MS, a cancelled registration (https://openairdocs.org/deregistered/N95MS-2018-01-24) (OpenAirDocs) - Registry model: Hughes 369HS (registry code 4470728, https://openairdocs.org/model/hughes-369hs) (OpenAirDocs) - Registry engine: Allison 250-C20 series (registry code 03020, https://openairdocs.org/engine/allison-250-c20-series) (OpenAirDocs) - Reported make and model: HUGHES 369HS - Reported engine: ALLSN 250C20B - People aboard: 2 - Fatal injuries: 2 - Pilot flight hours: 1,120 total, 260 in this make and model, 115 in the last 90 days - NTSB investigation: [NTSB LAX98LA200](https://openairdocs.org/ntsb/LAX98LA200) (OpenAirDocs) - FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/) - Page: https://openairdocs.org/incident/19980616013669A ## Narrative As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^. (.4) WITNESSES REPORTED THAT THE HELICOPTER TOOK OFF FROM THE SHIP, AND ABOUT 85 AGL, IT STARTED SPINNING TO THE RIGHT. THE PILOT CALLED 'NO CONTROL, MAYDAY,' ON THE RADIO. THE HELICOPTER NOSED DOWN AND IMPACTED THE WATER. THE AIRCRAFT WAS RECOVERED, EXCEPT FOR THE AFT PORTION OF THE TAIL ROTOR DRIVESHAFT AND TAILBOOM, INCLUDING THE TAIL ROTOR GEARBOX AND ALL TAIL ROTOR SYSTEM ROTATING COMPONENTS. THE WRECKAGE WAS SHIPPED TO THE UNITED STATES FOR EXAMINATION. THE AIRCRAFT HAD UNDERGONE A MAJOR OVERHAUL/REBUILD AND ANNUAL INSPECTION FOLLOWING A PREVIOUS ACCIDENT ON MARCH 11, 1997. AFTER COMPLETING 1.4 HOURS OF TEST FLIGHTS, THE HELICOPTER WAS THEN PARTIALLY DISASSEMBLED AND TRANSPORTED TO CALIFORNIA, AND SUBSEQUENTLY SHIPPED TO AMERICAN SAMOA. MAINTENANCE PERSONNEL IN HAWAII REASSEMBLED THE AIRCRAFT, AFTER REPLACING SEVERAL PARTS. THE OWNER OF THE MAINTENANCE FACILITY STATED SOME OF THE LIFE-LIMITED COMPONENTS WERE REPLACED WITH PARTS WITH LESS ACCRUED TOTAL TIME. HE REPORTED THAT THEY HAD TO ADJUST THE SHIM ON THE TAIL ROTOR DRIVESHAFT BECAUSE IT WAS 'WAY OFF, TOO TIGHT.' NO TEST RUN WAS PERFORMED AFTER REASSEMBLY. EXAMINATION OF THE HELICOPTER FOLLOWING RECOVERY REVEALED THE FORWARD TAIL ROTOR DRIVESHAFT COUPLING EVIDENCED A FRACTURE AND SEPARATION. THE FORWARD PORTION OF THE COUPLING REMAINED ATTACHED AT THE MAIN TRANSMISSION OUTPUT PINION, WHILE THE AFT PORTION OF THE COUPLING REMAINED ATTACHED TO THE FORWARD END OF THE TAIL ROTOR DRIVESHAFT. THE COUPLING BOLTS EVIDENCED SMEARING OF THE BOLT HEADS. SCANNING ELECTRON MICROSCOPY REVEALED A TOTAL OF EIGHT FRACTURE SURFACES. SIX FRACTURE SURFACES DISPLAYED FEATURES CONSISTENT WITH FATIGUE, ALTHOUGH MUCH OF THE MECHANICAL DAMAGE PREVENTED IDENTIFICATION OF ORIGIN LOCATIONS, AND THE OTHER TWO FRACTURE SURFACES EXHIBITED FEATURES CONSISTENT WITH OVERSTRESS SEPARATION. FURTHER, THE COUPLING IS DESIGNED WITH A BUILT-IN FAIL-SAFE FEATURE THAT WILL CONTINUE TO PROVIDE TORQUE TRANSMISSION IN THE EVENT THAT A FLEX FRAME LEG OR BOLT FRACTURED. WHEN THE FAIL-SAFE ENGAGES, THE UNBALANCE OF THE COUPLING INCREASES WITH A RESULTANT INCREASE IN THE VIBRATION, ALERTING THE PILOT TO TAKE THE APPROPRIATE ACTION AND LAND. (.19) HELI WAS TAKING OFF FOR A FISH SPOTTING MISSION WHEN IT LOST POWER ON DEPARTURE FROM SHIP AND CRASHED IN WATER. (-23) THE PILOT ONLY HAD A PVT PILOT HELICOPTER RATING AND HIS MEDICAL HAD RE VERTED TO A 3RD CLASS. HE ALSO WAS THE MECHANIC FOR THIS HELICOPTER ATTACHED TO THIS TUNA BOAT. SINCE THIS PILOT/MECHANIC RECEIVED FATAL INJURIES, NO CORRECTIVE ACTION IS PLANNED. ## The NTSB's investigation of this event (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB LAX98LA200](https://openairdocs.org/ntsb/LAX98LA200), Jun 16, 1998: Hughes 369HS (N95MS), Pacific Ocean (Pacific Ocean), destroyed, 2 fatal. Probable cause: The improper shimmying of the tail rotor driveshaft by maintenance personnel which induced fatigue in the tail rotor driveshaft coupling causing it to fail, which resulted in a loss of tail rotor… ## Other reports on N95MS (1) Matched to the same aircraft by N-number and date. - [Accident 19970311002879A](https://openairdocs.org/incident/19970311002879A), Mar 11, 1997: Hughes 369HS (N95MS), American Samoa, Destroyed. Fish spotting plane collided with ocean returning to ship helipad. Had lost power. Cracked plastic compressor case. From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.