Accident Description
The pilot reported that the airplane was descending from 8,000 feet after releasing skydivers. At approximately 3,000 feet, the airplane's door opened and contacted the underside of the wing. The pilot reduced speed and attempted to close the door, but observed that the door had warped and the window was missing.
Damage and Inspection
A postflight inspection revealed that the window had separated from the door in flight and contacted the right horizontal stabilizer, resulting in substantial damage to the stabilizer.
Examination Findings
An examination by a Federal Aviation Administration inspector determined that the door had been modified with a top hinge for skydiving operations. The door was secured by two pin-type latches that inserted into holes on the fore and aft sides of the door frame. The forward pin hole showed no damage, while the aft pin hole was torn, indicating that the latch pin was inserted at the time the door opened.