Incident Summary
During takeoff, an explosion occurred inside the left wing, resulting in a short-duration fire. The flight continued and landed uneventfully.
Findings
Examination of the aircraft revealed that the upper and lower wing skins were displaced, and fire damage was noted aft of the battery box. The positive battery cable was chafing against an open adel clamp located near the battery box; the PK screw was not in place. Arcing was noted on the battery cable.
Testing of the left auxiliary fuel tank revealed seepage from the fuel tank vent line. The fuel tank was not properly secured inside the wing. Damage to the external portion of the auxiliary fuel tank near the vent line was noted.
Evidence of previous fuel seepage from the left wing auxiliary fuel tank was found, including damage on the ground beneath the left wing area greater than damage to the ground beneath the right wing area. Additionally, a wax-type residue was found on the lower wing skin in the area of the fuel seepage.
Maintenance Manual Reference
The service manual indicates that electrical cables should be checked for condition every 100 hours.