What happened
On May 11, 2004, at 07:03 local time, an Airbus A320-214, registration EC-HTD, operated by Iberia, was performing a scheduled domestic flight from Madrid-Barajas to Bilbao. The aircraft was carrying 55 passengers and 6 crew members. Shortly after departing from runway 36R, approximately 30 seconds into the takeoff roll, the flight attendant notified the flight deck that passengers believed the wing was breaking apart. Upon investigation, the crew noted that the right engine's thrust reverser appeared to be deployed.
The crew requested an immediate return to Madrid-Barajas. During the subsequent landing on runway 33, the aircraft sustained damage. Upon inspection at the parking stand, it was discovered that the fan cowls of both engines had detached. This separation caused deformations to the engine nacelles at the wing junctions, impacts on the left wing leading edge (specifically the interior slat area), and damage to the vertical stabilizer. Fragments of the detached cowls were found scattered within the airport perimeter. There were no fatalities or injuries during the incident.
The investigation
The CIAIAC investigation focused on the maintenance history and the aircraft's preparation for flight. The investigation established that several scheduled maintenance checks (800-hour, 500-hour, and weekly inspections) had been performed the previous night. However, a specific task—an engine run-up to check for leaks following an oil and filter change—remained incomplete because noise restrictions at Madrid-Barajas prevented the run-up until 06:00, coinciding with a shift change.
Due to adverse weather conditions, the maintenance personnel had closed the fan cowls rather than leaving them in their usual open position. Crucially, the cowls were left with the locking pins unengaged and unsecured. The investigation found that the handover process between the departing and arriving maintenance shifts was flawed; the required information regarding incomplete tasks was not properly recorded in the shift handover log, and the incoming personnel were not notified of the pending work. Furthermore, the aircraft's flight logs incorrectly indicated that all scheduled inspections had been completed, leading to the aircraft being released for flight.
Findings
- The primary cause of the incident was that the aircraft was released for service with the engine fan cowls closed but with the locking pins unengaged and unsecured.
- This occurred because scheduled maintenance tasks were not completed, and the improper shift handover procedure prevented the incoming maintenance crew from identifying the pending work.
- The flight crew failed to detect the unsecured cowls during the pre-flight walkaround, a failure exacerbated by the fact that the inspection was conducted at night under adverse weather conditions.
- The inspection was further compromised because the locking pin handles were the same color as the cowls, making them difficult to distinguish, and the crew had not been specifically trained to recognize the visual cues of unlatched pins on this specific engine configuration.
- The aircraft was not equipped with the latest service bulletin updates (Goodrich SB RA32071-117) which included fluorescent paint on the handles to improve visibility.