Accident Overview
The accident occurred during a familiarization flight for a pilot in the left seat, conducted by a pilot-in-command in the right seat. The flight was intended to reach a nearby airport for fuel. Shortly after takeoff, one of the pilots reported an engine problem and stated they were diverting to an alternate airport. The airplane impacted a building and terrain approximately 10 minutes after departure.
Witness Accounts
A witness along the flight path reported hearing the engines accelerating and decelerating, followed by popping sounds. Several witnesses near the accident site reported hearing no engine sounds before impact.
Fuel Examination
Postaccident examination revealed very minimal fuel leakage on the ground. Only 23 ounces of aviation fuel were collected from the airplane’s five fuel tanks. No evidence of preimpact failure or malfunction was found for either engine or propeller. The damage to both propellers was consistent with low-to-no power at impact.
Fuel Quantity Indicator Examination
The fuel quantity transmitter (tank unit) was examined. Resistance between pins A and B (ends of the resistor element) was within specification. However, when monitoring potentiometer pin C, an open circuit was found between the wiper and the resistor element. X-ray imaging revealed a fractured electrical conductor between the wiper and pin C. Visual inspection showed no shorting, burning, or damage to the wire insulation. The National Transportation Safety Board (NTSB) Materials Laboratory examined the fractured conductor and found intergranular fracture surfaces with fatigue striations on multiple individual wires.
It is likely that the fatigue-fractured conductor strands caused the fuel gauge to indicate more fuel than was actually on board. This would have led the pilot to believe there was adequate fuel for the flight, consistent with the pilot’s decision to decline additional fuel before departure. The estimated fuel remaining since the last fueling (between 15 and 51 gallons) was substantially more than the actual amount at the start of the accident flight (between 8 and 10 gallons). The discrepancy may have resulted from insufficient settling time during fueling or operational usage of the airplane. Ultimately, the fuel supply was likely exhausted during the flight, resulting in loss of power to both engines.
Probable Cause
The official probable cause was a total loss of engine power due to fuel exhaustion. Contributing to the fuel exhaustion was the fatigue fracture of an electrical wire in the tank unit, which likely caused an inaccurate fuel quantity indication.
Other Findings
The effects from the right seat pilot’s use of cetirizine and the identified ethanol in the left seat pilot (likely from sources other than ingestion) did not contribute to the accident.