ERA22LA159

The pilot was also the owner and builder of the experimental amateur-built airplane. While returning to the airport after a local flight, the engine lost oil pressure, so the pilot diverted toward the nearest airport. The engine then began to run roughly and lost partial power. The airplane was not able to glide to the runway and collided with a ditch in a field during the forced landing. The pilot described that his postaccident examination of the engine revealed that the pinion gear on the pull starter motor fractured into several pieces that entered the accessory gear case, likely seizing the oil pump. About 4 years and 100 flight hours before the accident, the pilot had modified the pull starter motor from its original design so that the motor would fit in the airplane. Postaccident metallurgical examination found that the pull starter motor’s pivot lever was shortened. The pivot lever arm was designed to move the starter clutch and engage the pinion (small) gear to the crankshaft gear. The pinion gear teeth displayed indentations in their surfaces that indicated that they were only partially engaged to the crankshaft gear when the starter was being operated, a condition which was likely the result of the shortened pivot lever. This ultimately resulted in increased stress on the gear teeth during engine start and the subsequent failure of the gear in overstress. The liberated gear teeth likely damaged and seized the engine oil pump, and resulted in the partial loss of engine power.

On March 17, 2022, about 1130 eastern daylight time, an experimental amateur-built Q 200 airplane, N3QP, was substantially damaged when it was involved in an accident near Spring Hill, Florida. The private pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot, who was also the airplane owner, built the airframe and engine. He stated that, during a local flight, the engine lost oil pressure, so he diverted toward the nearest airport. The engine then began to run roughly and lost partial power. Because the airplane would not be able to glide to the runway, the pilot performed a forced landing to a field. Subsequently, the airplane collided with a ditch, resulting in substantial damage to the wings and fuselage. The airplane was equipped with a pull starter motor, which turned a large gear (through a sprag clutch) to a small gear, which drove the crankshaft. The pilot stated that the starter motor was a certificated airplane part that had been operated for about 100 hours since its overhaul in 2018. The pilot also stated that he had modified the pull starter motor to fit in the airplane. The pilot’s postaccident examination of the small gear found that it was fractured into several pieces that had entered the accessory gear case. The pilot added that oil streaks were present on the empennage. The pull starter motor was provided to the National Transportation Safety Board Materials Laboratory, Washington, DC. Metallurgical examination confirmed that the pull starter motor had been modified from its original design. Specifically, the pivot lever was shortened, and the starter motor power switch was removed and replaced with a power cable leading to a battery post. The pivot lever arm that was shortened was designed to move the starter clutch and engage the pinion (small) gear to the crankshaft gear. The pinion gear teeth had displayed indentations in their surfaces that indicated that they were only partially engaged to the crankshaft gear when the starter was being operated. The pinion gear teeth had fractured edges consistent with overstress.