Beech C23 N9246S accident near Prescott, Arizona

Probable cause

The pilots' improper inflight fuel management, which resulted in a total loss of engine power due to fuel starvation.

NTSB analysis

The pilot/owner and the pilot-rated passenger were making a multiple-leg cross-country trip. The day before the accident on two legs of the trip, the airplane's engine had run rough and experienced a partial power loss; both instances occurred after reaching cruise flight altitude and leaning the engine's fuel/air mixture. Due to the engine anomaly, the pilots elected to divert the night before the accident rather than continuing to the final destination in night conditions. The pilot/owner then consulted her mechanic, who attributed the power loss to vapor lock as a result of the weather conditions and instructed her to lean the mixture during the next pre-takeoff engine run-up.

The next morning, the pilots performed a preflight inspection. The airplane was not fueled before departure, and both pilots stated that the fuel onboard was adequate for the flight; however, neither provided the specific fuel quantity contained in each tank. The pilots departed with the left fuel tank selected and established a cruise altitude of 10,500 ft; the pilot/owner stated that she "did not lean the mixture at all" during the flight. About 50 minutes from the destination, the pilots switched the fuel selector from the left fuel tank to the right tank. Nearing their destination airport, they initiated a cruise descent and retarded the throttle to 1,800 rpm; the engine subsequently experienced a total loss of power. They attempted to restore engine power by cycling the throttle and mixture control but were unable to restart the engine. They did not switch fuel tanks. After determining that the airplane would not reach the runway, the pilots performed a forced landing to desert terrain. The airplane subsequently impacted the ground hard and bounced before it came to rest in an area of sparse desert vegetation about 1/2 mile from the airport.

A postaccident examination revealed that the fuel system was intact and not damaged during the accident; the right tank was found void of fuel, and the left tank contained about 10 gallons. Examination of the fuel sensor system showed that both the left and right fuel gauges erroneously indicated fuel was available when the fuel transmitters were placed in the empty position. An engine test run revealed no anomalies.

Based on the information provided by the pilots, the airplane likely departed on the accident flight with about 30 total gallons of fuel. Although fuel computations using the pilots' flight plan indicated that the right fuel tank, which was selected at the time of the engine power loss, should have had about 8 gallons of usable fuel remaining, the tank was void of fuel at the accident site.

The fuel consumption figures provided in the pilot's operating handbook indicated that the airplane's fuel consumption during the flight would have ranged from about 8.7 gallons per hour (gph) to 10.2 gph depending on the engine power setting and with the fuel-air mixture leaned to maximum power then slightly enrichened. Given that the fuel system was intact and that the right tank was completely void of fuel, the loss of power was likely the result of fuel starvation due to inflight fuel mismanagement.

Text from the NTSB. Open the NTSB docket for WPR16LA128 for the full record.