Incident
A DC-9 arrived at Carswell Air Force Base at 01:12 CST following a flight from Kelly AFB. USAF personnel offloaded and reloaded the aircraft with cargo. Engine start occurred at 02:04, and the crew received taxi instructions for runway 17. The aircraft took off at 02:09. At or immediately after rotation, the main cargo door opened. The crew declared an emergency and climbed to 2,500 feet mean sea level before entering a right turn. Approximately 5 nautical miles north of the airport, the captain initiated a shallow right turn for base leg. The aircraft crossed the extended centerline, prompting the captain to tighten the turn to establish position relative to the runway threshold. During this maneuver, the air load on the door likely caused it to rapidly move to the full-open over-the-top position. The sudden door opening produced unexpected changes in yawing and rolling moments. The captain, possibly partially disoriented, may not have sensed the increasing roll and nose-down pitch, failing to correct the changing attitude until a critical bank angle and altitude loss occurred. The DC-9 struck the ground in an inverted, nose-down, left-wing-low attitude and disintegrated.
Cause
Investigation revealed that the first officer, when closing the main cargo door, did not hold the door control valve T-handle in the closed position long enough for the latching hooks to engage over the door sill spools. External latched and locked indicators were applied incorrectly, leading the first officer to believe the door was properly latched because the handle pointed more toward the 'locked' chevron than the 'unlocked' chevron. Additionally, one of the two open-door warning light switches was malfunctioning. Due to the wiring configuration, this malfunction rendered the entire door warning system ineffective.
The official probable cause was the loss of control of the airplane for undetermined reasons following the in-flight opening of the improperly latched cargo door. Contributing factors were inadequate procedures used by Evergreen Airlines and approved by the FAA for pre-flight verification of the external cargo door lock pin manual control handle, the failure of McDonnell Douglas to provide flight crew guidance and emergency procedures for an in-flight cargo door opening, and the failure of the FAA to mandate modification to the door-open warning system for DC-9 cargo-configured airplanes, given previously known occurrences of in-flight door openings.