On October 29, 1998, a Grumman American AA-5A (registration N9956U) operated by Collins E. Brent was involved in an aviation accident near Scott, AR. Investigators recorded the probable cause as: The disengagement of the crankshaft gear due to the maintenance personnel not installing the gear lockplate at the last engine overhaul, resulting in the loosening of the gear retaining bolt, and the subsequent fracture of the gear alignment dowel. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An airplane experienced a total engine power loss during descent, resulting in a short landing, stall, bounce, and nose-over. Investigation found missing crankshaft gear lockplate and loose retaining bolt from the last overhaul.
Accident Overview
During an en route descent to the destination airport, the airplane experienced a total loss of engine power. The aircraft subsequently landed short of the runway. During the landing flare, the airplane stalled, bounced, touched down on the main landing gear, and nosed over.
Engine Examination
Post-accident examination of the engine revealed a lack of gear train continuity. Disassembly of the engine accessory case showed that the crankshaft gear lockplate was not installed and the crankshaft gear retaining bolt had backed out of the crankshaft by approximately 1 3/4 turns. The crankshaft gear alignment dowel was found fractured.
Maintenance History
The engine had accumulated 852 hours since its last overhaul and 13 hours since the last annual inspection. Review of maintenance records indicated that the engine was last overhauled in January 1987 and was returned to service by a Federal Aviation Administration (FAA) certified mechanic.