Incident Overview
A twin-engine turboprop airplane was cruising at 8,000 feet mean sea level when the left engine's outboard aft upper accessory case cowl door separated from its mount. The detached cowl door struck the top surface of the left wing, outboard of the engine nacelle, and penetrated the wing's fuel cell. This penetration resulted in fuel siphoning from the damaged cell.
Pilot Actions
In response to the fuel siphoning, the pilot performed a precautionary shutdown of the left engine. The airplane was subsequently landed without further incident.
Relevant Airworthiness Directive
Airworthiness Directive (AD) 91-18-11, effective September 3, 1991, required structural modification of the aft upper cowl assembly doors to prevent in-flight separation.