Flight Details
The accident flight was preceded by a 3.5-hour flight during which the airplane consumed approximately 156 gallons of its 196 gallons of usable fuel. Upon landing, the airplane was refueled with 156 gallons for the return leg.
Preflight Fuel Loss
During the preflight inspection, a line serviceman observed the right main fuel tank sump become stuck in the open position. An estimated 5 to 6 gallons of fuel were lost before the sump seal was regained, though the exact amount could not be determined. The lost fuel was not replaced before departure.
Return Flight and Diversion
Data from an onboard GPS unit indicated the airplane flew the return leg at an altitude of about 4,500 feet mean sea level for approximately 4 hours. About 4 minutes after beginning the descent to the destination airport, the pilot requested to divert to a closer airport. He was cleared for an approach to runway 18R at the new destination.
Accident Sequence
While on approach to land, the pilot reported to the air traffic control tower controller, “we exhausted fuel.” The airplane descended and crashed into a forested area about half a mile from the airport.
Post-Accident Examination
Post-accident examination of the right and left propellers revealed no leading edge impact damage or signatures indicative of rotation at the time of impact. Examination of the airplane wreckage and engines found no malfunctions or failures that would have precluded normal operation. The pilot did not report any problems with the airplane or its fuel state before announcing fuel exhaustion. His acceptance of the approach to runway 18R resulted in the airplane flying at least 1 mile further than if he had requested to land on runway 18L. According to the source, if the pilot had declared an emergency and made an immediate approach to the closest runway when he realized the exhausted fuel state, he likely would have reached the airport.
Toxicological Findings
Toxicological testing revealed cyclobenzaprine and diphenhydramine in the pilot’s system at or above therapeutic levels. Both medications carry warnings that use may impair mental and/or physical abilities required for activities such as driving or operating heavy machinery.
Fuel Calculation
The airplane would have used about 186 gallons of fuel on the 4-hour return flight if the engines burned fuel at the same rate as the previous flight. The fuel lost during the preflight inspection and the additional 30 minutes of flight time on the return leg reduced the airplane’s usable fuel available to complete the planned flight. The pilot likely did not recognize the low fuel state before the fuel was exhausted due to impairment by the medications he was taking.
Probable Cause
The pilot’s inadequate preflight fuel planning and management in-flight, which resulted in total loss of engine power due to fuel exhaustion. Contributing to the accident was the pilot’s use of performance-impairing medications.