ERA18LA074 · Cessna 172 S

The flight instructor reported that, during a local instructional flight along a coastline, he reduced engine power to idle when the airplane was at an altitude of about 2,000 ft above ground level and had the student pilot perform the checklist for an in-flight engine failure. As part of the simulated event, the student also performed the checklist for "unable to start engine." As the airplane reached an altitude of about 1,000 ft above ground level, the student increased engine power to recover, at which time the engine produced about 1,500 rpm and then returned to idle, even as the throttle was further increased. The flight instructor immediately took the flight controls. He turned off the magnetos and the engine. He then turned on the electric fuel pump for 2 seconds and attempted to restart the engine, but the engine produced only partial power. The flight instructor then performed a forced landing to a clearing on a beach. During the landing roll, the airplane's nosewheel sunk into the sand, and the airplane nosed over. The airplane's right wing and fuselage sustained substantial damage.

Postaccident examination of the airplane did not reveal evidence of any preexisting mechanical anomalies that would have precluded normal operation. A postaccident test run of the airplane's engine revealed that it started and operated normally at various power settings up to 2,000 rpm. Thus, given the available evidence, the reason(s) for the partial loss of engine power could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset