LAX99GA083 · McDonnell Douglas 369E

While the pilot was maneuvering about 550 to 650 feet agl, the engine chip light illuminated followed by a complete loss of engine power. She performed an autorotation to a large, open field, flared high about 100 feet agl, then collided with the ground. The skids were found spread outward with the belly touching the ground. Two of the main rotor blades displayed evidence of coning. Post-accident investigation revealed that all components of the lubrication system were intact and functional. When the turbine was disassembled, bearings 6 through 8 were found destroyed and displayed evidence of heat distress and oil starvation. The number 5 bearing evidenced heat distress. The nos. 1 through 5 bearings and the gearbox were lubricated, but there was no visual evidence of oil present downstream from the number 5 bearing. There was scoring and debris present in the oil pump scavenge chamber. Over a period of about 72 flight hours and 1 1/2 months, there were 10 reported engine chip light activations. After three chip lights were reported, the turbine, gear box, and compressor assembly were replaced. Engine chip lights were reported six more times. The number 5 bearing and snap ring were found spinning; a new number 5 bearing was installed. The day of the accident, the chip light came on during a maintenance ground run, then came on again before the engine quit. According to the Allison Engine Operation and Maintenance Manual, 'a maximum of four occurrences of magnetic chip warning lights encountered within any 50 hours of engine operation requires removal of the engine for shipment to an Allison Authorized Maintenance Center (AMC).'

Verbatim NTSB analysis and probable cause from the NTSB dataset