Cessna 172 N9884Q accident near Chesterfield, South Carolina

Probable cause

The partial loss of engine power due to a broken exhaust valve. Contributing to the accident was the operator's exceedance of the engine manufacturer's recommended time before overhaul.

NTSB analysis

The pilot stated that while flying pipeline patrol about 500 feet above ground level, the engine began to run “rough” and lose engine rpm with a corresponding loss of power. The pilot adjusted the carburetor heat, throttle, and mixture controls to the “full” positions, as well as adjusting the fuel selector to all positions, with no change in engine performance. He navigated toward the nearest airport and noted that the engine rpm had decayed to 1900 as the airplane descended. The pilot determined that he could not reach the airport and made an emergency landing in trees. Postaccident, the airplane engine started and ran but did not develop full power. Disassembly of the engine revealed excessive wear and a broken exhaust valve. The engine manufacturer recommended overhaul at 2,000 engine hours, or 12 calendar years, whichever occurred first. Examination of aircraft logbooks revealed that the engine had accrued 2,403 hours and nearly 13 years since its last overhaul.

Text from the NTSB. Open the NTSB docket for ERA09LA272 for the full record.