What happened
On 5 March 1998, a Reims Cessna F406, registration PH-FWD, was conducting a positioning flight from Glasgow to Edinburgh. Approximately ten minutes after departure, while cruising at 4,000 feet, a warning light indicating the door was unlocked illuminated on the cockpit panel.
In response to the alert, the handling pilot decreased the airspeed to approximately 160 knots. A crew member moved to the rear of the cabin to inspect the door and initially observed that all latches and handles appeared to be in the correct stowed position. However, two minutes later, the upper section of the door opened abruptly. Shortly thereafter, the lower section of the door failed at its hinges and became detached from the aircraft due to the force of the slipstream. The detached component was not recovered.
Despite the loss of the door section, the aircraft maintained normal handling characteristics. The crew proceeded to Edinburgh Airport, notifying Air Traffic Control of the situation during the approach. The aircraft landed safely without further complications.
The investigation
The investigation was based on the aircraft accident report submitted by the pilot. The inquiry focused on the sequence of the door's failure and the state of the locking mechanisms. The pilot-in-command noted that although the standard door closing procedures had been performed prior to departure, it was possible that the lock pins failed to engage properly.