DWYER MICHAEL D Q

Full Narrative

On March 17, 2022, about 1130 eastern daylight time, an experimental amateur-built Q200 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.