Beech A36 N2038Y accident near Big Bear, California

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack and failure to maintain adequate airspeed on short final while operating in adverse wind conditions, which resulted in an aerodynamic stall and impact with terrain.

NTSB analysis

Nearing the end of a cross-country flight, the pilot entered the airport traffic pattern for a landing at an airport that was surrounded on all quadrants by mountainous terrain. ADS-B data showed the pilot overshot the extended runway centerline when turning onto final approach. On short final the airplane’s airspeed decreased, and surveillance video footage revealed that the airplane’s right wing dropped, followed by a right roll and rapid descent. Subsequent video footage showed the airplane momentarily entered a level attitude, followed by the right wing dropping again. The airplane then entered a roll to the right and a rapid uncontrolled descent until it impacted the ground.

The airport’s automated weather observation system (AWOS) indicated that visual meteorological conditions (VMC) prevailed over the accident site, with unrestricted visibility and clear skies. The calculated density altitude at the time of the accident was about 8,200 ft. Weather data revealed thermodynamic and wind profiles that supported mountain wave activity, including updrafts and downdrafts near the accident site. Forecasting models indicated a hydraulic jump across the area at the time of the accident, which implied strong vertical motions that would likely have produced variations in the airplane’s airspeed and the potential for severe to extreme turbulence.

A review of the airplane’s performance using ADS-B data and the environmental conditions, including the strong southerly wind at the time of the accident, determined that after the pilot overshot the final approach, he initiated a 20° left turn to rejoin the final approach track. Based on ADS-B heading, altitude, and airspeed data, the increased load factor of the pilot’s right-wing aileron deflection and low airspeed likely exceeded the right wing’s critical angle of attack.

The National Weather Service (NWS) issued an urgent weather advisory about 1300, about 30 minutes before the accident flight departed. The urgent advisory identified that the accident site area was expected to encounter wind from the southwest at 25 to 35 mph with gusts to 60 mph. Additionally, the NWS issued a G-AIRMET valid for occasional moderate turbulence below 16,000 ft over the accident site, and advisories for mountain obscuration and strong surface winds immediately bordering the accident site.

A search of the FAA-contracted Automated Flight Service Station provider’s records indicated no contact from the pilot for any weather briefing information on the day of the accident. A separate search of ForeFlight weather products indicated that the pilot did not have an account, and no weather briefings or flight plans were filed for the accident airplane on the day of the accident. It is unknown what weather information, if any, the pilot checked or received before or during the accident flight.

Text from the NTSB. Open the NTSB docket for WPR23FA173 for the full record.