Amateur-built 701 N128CF accident near El Centro, California

Probable cause

A partial loss of engine power during the initial climb after takeoff due to oil starvation because of the failure of the No. 2 oil pump drive coupling.

NTSB analysis

The pilot reported that, during the initial climb after takeoff, the airplane sustained a partial loss of engine power and that he initiated a forced landing to a wet, muddy, wheat field. During the landing roll, the nosewheel of the airplane dug into the soft terrain and the airplane nosed over. A postaccident examination of the engine revealed that the No. 2 cylinder and piston exhibited signatures consistent with oil starvation. During disassembly of the engine oil pump system, the No. 1 shaft/bearing assembly for the oil pump system was intact and operational. The No. 2 drive coupling was found damaged, out of alignment, and not functioning. This condition would result in the oil supply system supplying oil at a sporadic rate, below minimal volume and pressure, which would result in oil starvation primarily to the No. 2 cylinder assembly.

Text from the NTSB. Open the NTSB docket for WPR11LA187 for the full record.