On April 22, 2000, an Air Tractor AT-401-B (registration N6096P) was involved in an aviation accident near Lawrenceburg, TN. Investigators recorded the probable cause as: The sticking of the number 3 cylinder's exhaust valve in the open position, which resulted in a loss of engine power and the subsequent collision with trees during an attempted forced landing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application flight, the pilot experienced a loud pop and black smoke from the engine. He attempted a forced landing but collided with trees due to the mechanical failure.
What happened
The pilot was conducting an aerial application run when he reported hearing a loud pop followed by the observation of black smoke emanating from the engine exhaust. Recognizing the severity of the situation, the pilot identified a suitable area for a forced landing. However, while maneuvering the airplane to align with the landing site, the aircraft collided with trees.
The investigation
A post-accident examination of the engine revealed that the exhaust valve on number 3 cylinder was stuck in the open position. This mechanical failure likely contributed to the loss of power and the subsequent inability to complete the forced landing safely.
Probable cause
The sticking of the number 3 cylinder's exhaust valve in the open position, which resulted in a loss of engine power and the subsequent collision with trees during an attempted forced landing.