Air Tractor AT502 N502S accident near Tappen, North Dakota

Probable cause

The partial loss of engine power for reasons that could not be determined based on the available evidence.

NTSB analysis

The pilot reported that he noticed degraded engine performance when the airplane was about halfway down the runway during takeoff for the aerial application flight. Specifically, the engine torque decreased from 1,700 ft-lbs at the start of the takeoff to 1,500 ft-lbs. He determined that there was not enough runway to abort the takeoff and stop the airplane, so he applied full power and dumped the product load. The engine continued to lose power, and the airplane subsequently continued off the end of the runway and nosed over in high vegetation. Postaccident examination of the airplane and engine, including individual testing of several engine components, confirmed that the engine was producing power during the impact sequence, but no determination could be made as to how much power the engine produced. The examination did not reveal any mechanical malfunctions or failures that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for CEN18LA249 for the full record.