North American NAVION A N91472 accident near Alameda, California

Probable cause

The pilot’s failure to maintain airspeed while maneuvering for an emergency landing, which resulted in an aerodynamic stall. Contributing to the accident was the loss of engine power for undetermined reasons during initial climb.

NTSB analysis

A pilot-rated witness reported that the airplane’s initial climb was normal and that the engine sounded good; however, as the airplane continued to climb, the engine lost power as if the throttle had been retarded or the mixture control placed in the idle cutoff position. The witness further reported that the airplane began a descending left turn and continued to descend until he lost sight of it. Another pilot reported hearing “emergency emergency” transmitted on the control tower frequency shortly after the accident airplane was cleared for takeoff. Examination of the accident site revealed that the airplane impacted terrain in a steep nose-down attitude. Postaccident examination of the airframe and engine revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation.

The airplane was equipped with auxiliary wing tip fuel tanks, and the five-point positive lock fuel selector valve was found in the right tip tank position. The fuel selector rotated freely and flow continuity was confirmed for each position. The left and right auxiliary tip tanks were separated from the wing tips and contained fuel; the left and right main tanks were breached; and the main auxiliary tank was intact and contained fuel. The flight manual supplement for the tip tanks stated that the auxiliary tip tank fuel was to be used in level flight only. However, it could not be determined if the fuel selector valve’s position as found resulted in fuel starvation to the engine and the subsequent loss of engine power.

The flight path observed by the witness and the damage to the airplane were consistent with the pilot maneuvering the airplane for an emergency landing and allowing the airspeed to decay, which resulted in an aerodynamic stall.

Text from the NTSB. Open the NTSB docket for WPR11FA184 for the full record.