What happened
The aircraft experienced a total loss of power and subsequently crashed due to fuel exhaustion. The incident occurred after the airplane had been airborne for a duration of 3 hours and 41 minutes. Prior to the flight, the pilot confirmed that the fuel tanks were filled to capacity at the time of takeoff.
The investigation
An analysis of the flight planning documents and the aircraft's documented conservative fuel burn rate indicated that the airplane should have retained sufficient fuel to remain airborne for at least 4 hours and 37 minutes. This calculation was based on a consumption rate of 13 gallons per hour against an aircraft fuel capacity of 60 gallons.
A mechanical examination of the fuel system revealed significant defects in the fuel bladder cells. Investigators found that several retaining clips were loose, leading to general collapsing and distortion of both cells. Logbook entries indicated that an airworthiness directive intended to remedy this specific issue had been complied with only 41 flight hours prior to the accident.