Beech 35B33 N9745Y accident near Berlin, Maryland

Probable cause

The failure of the No. 3 cylinder exhaust valve, which resulted in the total loss of engine power during takeoff.

NTSB analysis

The pilot stated that, shortly after he retracted the landing gear during the initial climb after takeoff, the airplane began to vibrate and the engine lost power. The pilot initiated a 180° return to the runway, but unable to reach it, performed a forced landing to a golf course.

Postaccident examination of the airplane’s engine revealed that the No. 3 cylinder sustained catastrophic damage, including heavy mechanical damage to the piston and separation of the exhaust valve, a portion of which was lodged under the intake valve. Numerous pieces of metal consistent with material from the No. 3 piston head were found in the oil sump. Given this information, it is likely that the loss of engine power was due to the failure of the No. 3 exhaust valve.

The engine manufacturer's maintenance manual recommended that this engine be overhauled at 1,500 hours of operation or every 12 years, whichever occurred first. The maintenance manual also recommended that a borescope be used to inspect the engine’s cylinders during every 100-hour/annual inspection in conjunction with a compression test. The engine maintenance records listed the compression test results during previous annual inspections but did not indicate whether the cylinders had been inspected with a borescope. At the previous annual inspection, about 1 month before the accident, the engine total time was 1,769.1 hours. Additionally, the engine was manufactured about 37 years prior to the accident and had not been overhauled. The investigation did not determine if the impending failure of the exhaust valve could have been detected and corrected had the borescope inspections been performed and/or the engine had been overhauled.

Text from the NTSB. Open the NTSB docket for ERA18LA181 for the full record.