Beech P35 N8572M accident near Upland, California

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack, for reasons that could not be determined, which resulted in a subsequent aerodynamic stall and impact with a building.

NTSB analysis

A witness observed, and surveillance video verified, that the airplane took off and then entered a nose-high climb before the left wing dropped and the airplane entered a spin. The airplane disappeared from view as it dropped behind hangars. The witness estimated the airplane’s angle of attack between 30° to 45° nose high. He observed the airplane’s nose drop and the left wing lose lift before the airplane transitioned into a nose-low spin. The witness stated that it sounded like the engine was making full power the whole time and the flaps appeared to be retracted. Postaccident examination of the accident site showed that the airplane clipped the hangar roof before coming to rest on the ground at the hangar entrance. The majority of the airplane was thermally destroyed in the postcrash fire.

Autopsy results indicated that the pilot, who did not hold a current medical certificate at the time of the accident, had heart disease that conveyed at least a mildly increased risk of a sudden impairing or incapacitating cardiac event. There is no autopsy evidence that such an event occurred. However, such an event does not leave reliable autopsy evidence if it occurs immediately before death; whether the pilot’s heart disease contributed to the accident could not be determined. Toxicology testing revealed the presence of ethanol at a very low level in the pilot’s brain tissue; the detected ethanol was likely from postmortem production. Thus, it is unlikely that ethanol contributed to the crash.

Postaccident examination of the airplane and engine revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. Impact signatures on the propeller indicated the engine was likely operating at the time of impact. The high angle of attack observed by the witness and on the airport surveillance video likely resulted in an aerodynamic stall and impact with the building.

Text from the NTSB. Open the NTSB docket for WPR23FA287 for the full record.