What happened
On 12 December 2015, a Ryanair Boeing 737-800, registration EI-DLR, was parked at position 101 in Terminal 2 of Barcelona Airport. The aircraft had arrived from Seville and was in the process of disembarking passengers via the air bridge (finger) connected to the left forward door (L1).
During the disembarkation, a flight attendant noticed the aircraft's nose behaving unusually. The flight crew confirmed that the air bridge was lifting the aircraft. In response, the crew instructed the remaining passengers to sit down and fasten their seatbelts to prepare for a potential impact. Shortly thereafter, the L1 door and its hinges collapsed under the weight of the aircraft. The nose of the aircraft dropped from an estimated height of 2 meters, striking the nose gear. The remaining passengers were evacuated through the rear door. Two passengers sustained minor injuries, including a knee injury and physical discomfort due to anxiety.
The investigation
The CIAIAC investigation focused on the mechanical failure of the air bridge's self-leveling system. Investigators conducted functional tests on the air bridge, which included the recently renovated finger 101. While the specific failure mode could not be perfectly replicated during testing, investigators identified a latent failure in the hydraulic elevation circuit's electrovalve, which could randomly freeze in an open position.
Further examination of the renovation work performed by the UTE (a joint venture) revealed that the new programmable logic controller (PLC) had increased the activation interval for the hydraulic pump from 1 second to 600 seconds. This change meant that once the electrovalve failed, the hydraulic pressure remained active for an extended period, allowing the uncontrolled lifting to continue until the bridge reached its physical limit.
Findings
- The uncontrolled lifting of the air bridge was caused by the combination of a failed electrovalve in the hydraulic elevation circuit and a modified software parameter that increased the pump activation interval.
- The renovation of the air bridge, completed months prior, introduced a new software logic that failed to account for the potential failure modes of existing hydraulic components.
- The flight crew and cabin crew acted effectively to mitigate passenger risk by halting disembarkation and instructing passengers to secure themselves before the door collapsed.