Incident Overview
Upon landing at the destination airport, the pilot was informed that he would have to pay a ramp and parking fee unless he purchased a minimum of 15 gallons of fuel. Although the airplane did not require additional fuel for the subsequent flight, the pilot chose to buy fuel to avoid the fees.
Refueling and Overflow
While the refueler was servicing the left auxiliary fuel tank, between 1 and 5 gallons of fuel were allowed to overflow. The exact volume of overflow was not specified beyond that range.
Engine Start and Explosion
Approximately 15 minutes after the refueling, the pilot attempted to start the left engine. Simultaneously, an explosion occurred in the left wing. The engine did not start, but the pilot believed at the time that the engine had backfired, coinciding with the explosion.
Post-Incident Examination
Subsequent examination of the left wing revealed damage consistent with an internal explosion. The fuel cells were found to be intact, full of fuel, and not leaking.