Incident Overview
After takeoff, as the airplane climbed through 500 feet above ground level, the cabin entry door, which had been closed by the copilot at the pilot's request, came open. The pilot executed a return to the departure airport, where the airplane was landed without further incident.
Damage Assessment
The door remained attached at the hinge, but approximately half of the door skin was pulled away, resulting in substantial damage to the airplane pressure vessel.
Pilot and Operator Statements
The pilot stated that the CABIN DOOR annunciator was never illuminated. Following the event, the operator reported that all door latches were found in the extended positions.