NTSB Identification: SEA03TA014.
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Accident occurred Friday, November 29, 2002 in Snohomish, WA
Probable Cause Approval Date: 06/25/2003
Aircraft: Hughes OH-6A, registration: N13SD
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.

The pilot reported that about five minutes after departure, in cruise flight, at 100 knots and 1,000 feet msl, the engine rpm fluctuated with a noticeable engine noise reduction. Subsequently N2 rapidly decelerated and the helicopter yawed to the left. The pilot initiated an autorotation, however, due to heavily wooded terrain, the pilot had to maneuver around obstructions to a landing site. During the maneuver, the helicopter collided with a tree branch which broke the chin bubble. At approximately 100 feet agl, the pilot started the deceleration. Approximately 30 feet agl, the forward airspeed was at or near zero. The helicopter descended faster than the pilot anticipated as he pulled in collective to slow the descent and then a significant amount of collective to cushion the landing. The helicopter landed with more force than normal and the helicopter rolled to the right after landing. The right side fore and aft skid legs collapsed at the mid point of the struts and the helicopter came to rest on its right side. The engine was inspected and subsequently removed for an engine test cell run. During the engine test cell run, the engine was found to be making more than rated horsepower at all points.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Loss of engine power for undetermined reasons while in cruise flight. A tree was a factor.

Full narrative available

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