NTSB Identification: FTW03LA066.
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Accident occurred Sunday, December 22, 2002 in Fritch, TX
Probable Cause Approval Date: 03/30/2004
Aircraft: Hughes 369E, registration: N5234Y
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The helicopter was damaged during a forced landing after a loss of engine power while in cruise flight. The 14,700-hour pilot stated that at 5,100 feet MSL, the generator warning light illuminated. The pilot switched the generator "OFF" and back "ON" in an attempt to reset it, and was unable to reset the generator. The pilot then recycled the circuit breaker to try to reset the generator, and was still unable to reset the generator. The pilot pulled the generator circuit breaker and aborted the flight. Approximately 15 minutes after the generator failure, the engine out light illuminated and an audio warning came on, engine and rotor RPM started to decay and the pilot initiated autorotation. The auto re-ignition light illuminated during autorotation, but the engine would not spool back up to normal RPM. The pilot continued with the autorotation to a small clearing. During the final phase of the autorotation the pilot performed a cyclic flare to increase rotor RPM and arrest forward movement. The pilot leveled the helicopter a few feet off the ground and pulled the collective to arrest descent, at that point rotor RPM decayed and the helicopter dropped four feet AGL. The helicopter spun approximately 180 degrees from the original heading and impacted the ground nose first, on a heading of 30 degrees. Examination of the generator revealed that its drive-end bearing had failed. Bearing cage pieces fell out during disassembly. A Pc air leak test was performed and a air was detected emanating from the Pc air tube from the power turbine governor (PTG) to the engine fuel control unit (FCU). The tube was fractured approximately 90% circumferentially just above the coupling nut that attaches the tube to the FCU. A new Pc air tube (same part number) was installed and the engine was operated in a test cell. The engine was operated in accordance with the model 250-C20B Production Test Specifications. With the engine in the standard test configuration, response times were within normal limits and the engine met all performance parameters. Further metallurgical examination of the Pc tube revealed evidence of fatigue.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The loss of engine power due to the failure of the generator input drive-end bearing, which resulted in excessive vibrations that induced a fatigue fracture of the Pc line leading to the engine fuel control unit. A contributing factor was the lack of suitable terrain for the forced landing. Full narrative available
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