NTSB Identification: DEN01LA103.
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Accident occurred Monday, May 28, 2001 in Bennett, CO
Probable Cause Approval Date: 02/20/2002
Aircraft: Hall Lancair 4P, registration: N707SH
Injuries: 3 Minor.
NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
While in cruise flight, the oil pressure warning light illuminated, and the oil pressure gauge fluctuated between 0 and 10 psi. The engine made a loud noise and began to vibrate and lose power. A forced landing was made in an open field. After touch down, the left main and nose landing gear buckled, then the right main gear collapsed, shearing off the right wing. During the engine disassembly and inspection, it was discovered that the starter adapter drive shaft had fractured forward of the oil scavenge pump gears at a snap ring groove. This allowed pressurized lubricating oil to be discharged through the turbocharger turbine and compressor oil seals. Metallurgical examination concluded that the fracture was in fatigue and had initiated at multiple origins at the snap ring groove root fillet.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: unsuitable terrain on which to make a forced landing. A contributing factor was a fatigue fracture of the starter adapter drive shaft, which resulted in a loss of engine power due to oil starvation. Full narrative available
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