Cessna 172 N924MM accident near Lynchburg, Virginia

Probable cause

The stuck No. 2 cylinder exhaust valve, which resulted in a partial loss of engine power and a subsequent forced landing and impact with a ditch.

NTSB analysis

The flight instructor reported that, shortly after the student pilot conducted the takeoff for the instructional flight, they felt the engine vibrate and the airplane shudder. They then noticed that the rpm had decreased and that the engine's performance had degraded. The instructor took the controls and lowered the nose to prevent a stall. He attempted to land on the intersecting runway, and the airplane touched down with about 100 ft of runway remaining. Realizing that the airplane could not be stopped within the remaining runway, the instructor steered the airplane right to avoid a steep drop-off past the runway end. The airplane subsequently impacted a ditch and then came to rest in grass in a nose-down position. The left wing sustained substantial damage.

Postaccident examination of the engine revealed that the No. 2 cylinder exhaust valve was stuck open. Given this evidence, it is likely that the stuck exhaust valve resulted in the partial loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA19LA019 for the full record.