McDonnell Douglas 369E N1502

Summary

On 25 June 2003 at about 15:00 local time, a McDonnell Douglas 369E registered N1502, operated by USDA APHIS Wildlife Services, was involved in an accident near Big Timber, Montana, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

25 June 2003 at 15:00

Classification

Accident

Location

Big Timber, Montana, United States

Coordinates

45.9186, -109.8711

Aircraft

McDonnell Douglas 369E

Registration

N1502

Category

Helicopter

Engines

1

Operator

USDA APHIS Wildlife Services

Operating rule

Public Use

Purpose of flight

Public Use

Phase of flight

Not recorded

Route

Big Timber → Helena

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

SEA03TA116

2 people had minor injuries.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full 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.

Quoted verbatim from the NTSB record.