Piper PA32RT N31981 accident near Bulverde, Texas

Probable cause

The partial loss of engine power due to excessive carbon deposits that resulted in one or more stuck exhaust valves.

NTSB analysis

The pilot reported the airplane did not accelerate as usual during the takeoff roll. To avoid obstacles at the end of the runway, the pilot continued the takeoff. The airplane cleared powerlines, trees, and a school, but was nearing a stall so the pilot decided to make a forced landing in a field. During the landing the airplane collided with a tree, resulting in substantial damage to the right wing and fuselage.

Examination of the engine found excessive carbon deposits around the No. 4 cylinder exhaust valve. A large amount of carbon buildup was found on the rocker arm, rocker shaft, and valve spring. The rotator cap also had carbon deposits and exhibited a groove wear pattern consistent with a lack of cap rotation. The exhaust valve guide had excessive wobble and movement within the guide. The No. 5 exhaust valve also displayed signatures of carbon buildup but not to the same extent as the No. 4.

No other anomalies were detected with the engine or airframe.

The loss of engine power was likely due to at least one stuck exhaust valve.

Text from the NTSB. Open the NTSB docket for CEN22LA413 for the full record.