What happened
On June 20, 2021, a Diamond DA 42 NG, registration EC-MCO, was conducting a local flight for a CPL(A) multi-engine proficiency test near Utrera, Spain. The aircraft was operated by Flight Training Europe S.L. and was occupied by an examiner and a student pilot.
Approximately 20 minutes into the flight, while cruising 19 NM northeast of Jerez Airport (LEJR), the crew received a "DOOR OPEN" alert on the Garmin G100 and Integrated Cockpit System (ICS). Shortly after this alert, a loud impact was heard, and the passenger door detached from the aircraft. The examiner immediately took control of the aircraft, verifying that the airframe's structural integrity remained intact.
The crew reduced engine power and performed a turn to locate the lost door, but the search was unsuccessful. The crew declared a PAN-PAN urgency signal to Jerez Tower and returned to the airport. The aircraft landed safely on runway 20 at 15:10 local time. The two occupants were uninjured, though the aircraft sustained significant damage to the door hinges and the door itself was lost.
The investigation
The CIAIAC examined the condition of the aircraft's door frame and the flight data recorded by the Garmin G1000. The investigation focused on whether the detachment was caused by a mechanical failure or human error.
Inspectors found that the door frame and locking recesses showed no signs of damage or deterioration. However, the forward hinge anchor point was damaged, and the rear hinge's movable part was broken. The investigation also reviewed maintenance records, noting that a 2000-hour inspection, which included functional tests of the door locking mechanism, had been completed only nine days prior to the accident.
Findings
- The investigation ruled out mechanical failure of the locking mechanism, as the door frame and recesses were undamaged.
- The primary cause of the detachment was the inadequate closing and locking of the passenger door by the student pilot.
- It is believed that while the door was closed enough to engage the micro-switch and trigger the initial lock, it had not passed the point required to prevent spontaneous opening.
- Aircraft vibrations likely caused the mechanism to gradually shift until the bolts retracted from their housings, allowing the wind to catch the door and tear it from the airframe.
- The crew managed the emergency effectively, following established procedures and communicating clearly with Air Traffic Control.