BU 133 N1940J accident near Missoula, Montana

Probable cause

The pilot’s failure to maintain adequate airspeed and his exceedance of the airplane’s critical angle of attack while executing a return to the runway after takeoff, which resulted in an aerodynamic stall/spin. Contributing to the accident was the pilot’s decision to take off with a known mechanical problem.

NTSB analysis

The airline transport pilot purchased the airplane the day before the accident and was flying it across the country to his home airport. After landing at the accident airport, the pilot spoke on the telephone to a mechanic familiar with the airplane. The pilot reported to the mechanic that, after both of his earlier refueling stops, during the take climb, fuel had entered the cockpit, but after flying for a while, it stopped. The pilot stated that someone was helping him inspect the fuel system, but they were not able to find anything wrong. The mechanic stated that it sounded like a fuel venting problem and recommended that the pilot not fly the airplane until the issue was resolved. The pilot told the mechanic that he needed to get the airplane home and said that he was going to depart with all electrical power off.

On the initial takeoff climb, witnesses saw the airplane enter a steep right turn; this was consistent with the pilot attempting to return to the runway. After turning about 180°, the airplane stalled, entered a spin, and descended to ground impact. Upon impact, a fire erupted, which consumed most of the airplane.

Although the pilot had told the mechanic that he had someone help him inspect the fuel system, no one was identified at the accident airport who reported helping the pilot inspect the fuel system or seeing the pilot or anyone else perform such an inspection. Therefore, it is likely that the pilot experienced the same fuel leakage problem on the accident takeoff that he had experienced after his previous refueling stops. Extensive postcrash fire damage to the fuel system prevented determination of the source of the fuel leak. The fuel selector was found in the "off" position.

Because the pilot choses to take off with no electrical power, he was unable to communicate the reason for his turn to tower controllers. It is likely that the pilot was distracted by fuel entering the cockpit and failed to maintain adequate airspeed as he was returning to the airport to rectify the problem, which resulted in the airplane exceeding its critical angle of attack and an aerodynamic stall/spin.

Toxicology testing identified 10% carbon monoxide in the pilot's specimens. This was likely due to the postcrash fire.

Text from the NTSB. Open the NTSB docket for WPR16FA012 for the full record.