WPR22FA087 · Beech K35

The pilot of the accident airplane departed the runway, stating that he was planning to remain in the traffic pattern. The pilot was then cleared to land; on the final approach, after crossing the runway threshold and just before the airplane touched down the airplane pitched up, ascended about 50 ft, and subsequently rolled left before entering a near-vertical descent and then impacting the ground. The airplane’s autopilot was repaired 1.5 flight hours before the accident flight, wherein the auto-pilot pitch servo was sent out for repair, reinstalled, and cable tensions were set. Subsequently, an operational check was conducted, which verified proper installation on the ground. The autopilot pitch servo capability is exhausted by a pitch hold setting, meaning that inadvertent activation would merely maintain the airplane’s present pitch profile at the time of activation. Postaccident examination of the pitch trim actuator revealed a 15° tab down position. The elevator tab limits are 4.5° tab up, to 23° tab down. While the pitch servo had been recently installed, it is not likely that the autopilot was engaged in the airport traffic pattern and specifically during landing. Postaccident examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. The cause of the abrupt nose-up pitch attitude during landing could not be determined. Pilot incapacitation was not a factor in this accident.

Verbatim NTSB analysis and probable cause from the NTSB dataset