Cessna 414 N4765G accident near Modesto, California

Probable cause

The pilot’s exceedance of the airplane’s critical angle of attack and failure to maintain proper airspeed during a turn to final, resulting in an aerodynamic stall and subsequent impact with terrain. Contributing to the accident was the pilot’s distraction due to a non-critical radio anomaly.

NTSB analysis

Shortly after taking off, the pilot was instructed to change from the airport tower frequency to the departure control frequency. Numerous radio transmissions followed between tower personnel and the pilot that indicated the airplane’s radio was operating normally on the tower frequency, but the pilot could not change frequencies to departure control as directed. The pilot subsequently requested and received approval to return to the departure airport. During the flight back to the airport, the pilot made radio transmissions that indicated he continued to troubleshoot the radio problems.

The airplane’s flight track showed the pilot flew directly toward the runway aimpoint about 1,000 ft from, and perpendicular to, the runway during the left base turn to final and allowed the airplane to descend as low as 200 ft pressure altitude (PA). The pilot then made a right turn about .5 miles from the runway followed by a left turn towards the runway. A pilot witness near the accident location observed the airplane maneuvering and predicted the airplane was going to stall. The airplane’s airspeed decreased to about 53 knots (kts) during the left turn and video showed the airplane’s bank angle increased before the airplane aerodynamically stalled and impacted terrain. Postaccident examination of the airframe, engines, and review of recorded engine monitoring data revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation.

Toxicology testing showed the pilot had diphenhydramine, a sedating antihistamine, in his liver and muscle tissue. While therapeutic levels could not be determined, side effects such as diminished psychomotor performance from his use of diphenhydramine were not evident from operational evidence. Thus, the effects of the pilot’s use of diphenhydramine was not a factor in this accident.

The accident is consistent with the pilot becoming distracted by the reported non-critical radio anomaly and turning base leg of the traffic pattern too early during his return to the airport. The pilot then failed to maintain adequate airspeed and proper bank angle while maneuvering from base leg to final approach, resulting in an aerodynamic stall and impact with terrain.

Text from the NTSB. Open the NTSB docket for WPR23FA092 for the full record.