Amateur-built RV-4 N418GM accident near Pageland, South Carolina

Probable cause

Maintenance personnel’s improper installation and inspection of the crankshaft idler gear, which resulted in a loss of engine power.

NTSB analysis

The pilot stated that during cruise flight the engine made a popping sound and subsequently experienced a loss of power. He performed an emergency landing on a road and during the landing roll the airplane struck a ditch. A postaccident examination of the engine revealed that the crankshaft idler gear was missing a lock plate, which likely resulted in the idler gear vibrating loose from the engine case, leading to the loss of engine power. The lock plate was not found and no other anomalies were noted during the examination. An annual conditional inspection on the engine was conducted 10 days prior to the accident; the engine was overhauled about 320 flight hours prior to the accident. Based on the evidence and records, it is likely that the lock plate was not installed during the last overhaul.

Text from the NTSB. Open the NTSB docket for ERA10LA316 for the full record.