Amateur-built VANS RV-9A N362TS accident near Marianna, Florida

Probable cause

Failure of the propeller speed reduction gearbox for undetermined reasons. Contributing to the accident was the pilot’s decision to disregard the manufacturer's mandate to replace the gearbox, the manufacturer's failure to provide owners with technical substantiation for the replacement, and the pilot's decision to overfly several suitable off-field landing sites in an attempt to glide to a distant airport.

NTSB analysis

The owner/pilot reported that, at an altitude of about 4,000 feet in his experimental amateur-built airplane equipped with a non-certificated propeller speed reduction unit (PSRU) gearbox, he heard a loud "bang." Although the engine continued to run normally and the pilot could control the engine rpm, the pilot determined that he was no longer obtaining thrust from the propeller. In his attempt to glide to an airport about 13 miles from the failure location, the pilot overflew multiple fields and sections of roadway that were suitable for an off-field landing. The airplane struck trees 3 miles short of the intended airport, and the pilot was seriously injured. Postaccident examination revealed that the PSRU gearbox had failed catastrophically, with the result that the engine was unable to transmit power to the propeller. Investigation revealed that the accident PSRU gearbox was the manufacturer's first generation version, referred to as "Gen-I." At the time of the accident, third-generation "Gen-III" gearboxes were current, and the manufacturer had previously determined and notified owners that replacement with the Gen-III version was mandatory. The pilot was aware of the manufacturer's mandate regarding the gearbox replacement, but based on cost and time-in-service reasons, he decided not to replace his Gen-I gearbox. While the gearbox manufacturer "mandated" that owners replace their previous model gearboxes, and his published information clearly stated that he had safety concerns about the previous model gearboxes, he was actually unable to force them to replace the gearboxes. Since the manufacturer did not provide the gearbox owners with substantiating data such as failure rates, time in service, or a catalog of failure events, gearbox owners could have concluded that the manufacturer's mandate was motivated by economic, instead of safety, reasons.

Text from the NTSB. Open the NTSB docket for ERA09LA477 for the full record.