NTSB Factual Report

On December 22, 2002, at approximately 1445 central standard time, a Hughes 369E helicopter, N5234Y, registered to and operated by Amistad Aviation of Amistad, New Mexico, was substantially damaged during a forced landing following a loss of engine power near Fritch, Texas. The airline-transport pilot and his passenger were not injured. Visual meteorological conditions prevailed and a flight plan was not filed for the Title 14 Code of Federal Regulations Part 91 business flight. The cross-country flight originated at 1400 from a private feed yard near Syracuse, Kansas, and its destination was a feed yard near Gruver, Texas.

The 14,700-hour pilot stated in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that approximately 1430, while in cruise flight 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, but 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 circuit breaker, turned off the generator switch, and turned the helicopter southwest to the closest airport, Tradewind Airport, near Amarillo, Texas. In order to conserve battery power, the pilot turned off all non-essential loads.

The pilot reported that 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 entered an 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 pilot added that the helicopter spun approximately 180 degrees from the original heading and impacted the ground nose first, on a heading of 30 degrees. The pilot reported that the engine was still running at the time of impact, so he closed the fuel shutoff valve to stop the engine. The helicopter skidded about 15 feet, turned to the left about 45 degrees, and came to rest in an upright position on its nose. All main rotor and tail rotor blades were accounted for. The main rotor blades severed the tail boom. The landing gear skids were severely damaged.

Examination of the engine by the manufacturer revealed no external damage to the engine, and no visual anomalies were noted to any of the engine accessories. Examination of the starter/generator by the manufacturer revealed that the generator drive-end bearing had failed. Bearing cage pieces fell out during the starter 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.

NTSB Probable Cause

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.