Amateur-built Series 5 N743JT accident near Yucca Grove, California

Probable cause

The pilot’s improper repair of the oil sump, which resulted in a loss of oil pressure and collision with terrain during a precautionary landing.

NTSB analysis

The pilot reported the engine run-up and takeoff were normal. While in cruise flight the pilot noticed a slight drop in oil pressure. With no increase in oil temperature or other engine warnings he decided to continue the flight while monitoring the engine parameters. A short time later the oil pressure began to drop at a faster rate. He decided to perform a precautionary landing. He shut down the engine and configured the airplane for landing on a highway service road, but while on approach he noticed the landing area was obstructed by light poles. He maneuvered the airplane towards an adjacent dirt field; however, the terrain was much rougher than anticipated, and the airplane nosed over during roll out after striking scrub brush.

The engine’s oil sump had a crack in its mounting flange that resulted in a loss of oil on previous flights, but not at a significant rate. The crack was then improperly repaired by the pilot, who used epoxy putty to seal it rather than having it welded or replaced. During the accident flight, which was the first since the repair, the crack propagated beyond the putty fill area and the putty unbonded, resulting in most of the engine oil being expelled out of the crack.

Text from the NTSB. Open the NTSB docket for WPR24LA121 for the full record.