SEA03TA116 · McDonnell Douglas 369E
USDA APHIS Wildlife Services McDonnell Douglas 369E · Accident: total loss of engine power (mechanical failure) en route
From Big Timber Airport (6S0) to Helena Regional Airport (HLN)
Event
- NTSB case
- SEA03TA116
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Government
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
McDonnell Douglas 369E
- Aircraft type
- McDonnell Douglas 369
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N1502
- Operator
- USDA APHIS Wildlife Services
- Onboard fatalities
- Unknown
- Route
- From Big Timber Airport (6S0), Big Timber, MTTo Helena Regional Airport (HLN), Helena, MT
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Public Aircraft
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · cruise
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Total loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Compressor assembly › Disconnected
- Compressor assembly › Fatigue
- Compressor assembly › Fractured
- Compressor assembly › Fretted
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
While operating at an altitude of about 40 feet and 40 knots airspeed on a low level coyote predation flight the pilot of the (Hughes) McDonnell Douglas 369E helicopter heard a loud bang and observed both the "Engine Out" and "Auto Relight" warning lights illuminate. The pilot reduced collective and immediately transitioned to a forced landing onto uneven terrain during which the helicopter touched down hard and the right skid separated. Post-crash examination of the Rolls Royce (Allison) 250-C20B turboshaft engine revealed that the compressor coupling adapter had fractured circumferentially resulting in the disconnection of the compressor from the turbine assembly. Further examination revealed that the Rolls Royce (Allison) manufactured compressor adapter coupling had been installed approximately 1,005 hours earlier and that the separation had been the result of multiple fatigue fractures in the coupling associated with severe fretting on the adapter's outer diameter where it inserts into the spur adapter gearshaft.
Probable cause
Fretting on the outside diameter of the compressor coupling adapter which resulted in fatigue and subsequent fracture of the adapter, and ultimately the disconnection of the compressor from the turbine assembly. Contributing factors were low rotor RPM, uneven terrain and collapse of the right skid on landing.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA03TA116
- Event ID
- 20030701X00979
- Case number
- SEA03TA116
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: a6e9a17a2c512c75ebcd7c3e296d4d81c03681e6fcaeef48ad2af35e8434e278; retrieved 2026-09-18T21:17:40.034Z.