What happened
On 2 April 2019, an Airbus A3/19-131, registration G-DBCD, was operating a commercial passenger flight from London Gatwick to Palma De Mallorca. Prior to departure, maintenance engineers had performed work to deactivate the No 1 spoiler to allow the aircraft to fly under the Minimum Equipment List (MEL) provisions.
During the cruise phase, the crew noticed the aircraft was flying with a slight left wing-down attitude and a light vibration. While the crew monitored the situation and consulted maintenance control, the flight continued toward the destination. However, during the approach with the autopilot engaged, the selection of full flaps caused the aircraft to roll noticeably to the left and deviate from the flight director. This was accompanied by buffeting and the repeated extension and retraction of the right-wing spoilers.
At 800 ft agl, the handling pilot disconnected the autopilot, which resulted in a further left roll that required significant sidestick input to correct. The crew managed to maintain the approach profile and landed the aircraft without further incident. Upon arrival, inspections revealed that the No 1 spoiler had been left in the maintenance position with the maintenance key still installed, allowing the surface to 'float' up in the airflow.
The investigation
The investigation examined the maintenance procedures performed prior to departure. It was established that two engineers had attempted to deactivate the spoiler actuator to resolve a flight control status message. The work was conducted in heavy rain and cold temperatures, which impacted the engineers' ability to use their digital maintenance tablets and complete the technical logbook.
Investigators found that the engineers had not fully adhered to the Aircraft Maintenance Manual (AMM) procedure. The digital interface used to access the manual was difficult to navigate, as it did not support multiple tabs and required repetitive scrolling. Furthermore, the engineers were working on an unfamiliar task and were influenced by previous experiences where maintenance keys were left in place during hangar maintenance.
Findings
- The No 1 spoiler was left in the maintenance position with the maintenance key installed.
- Improper adherence to the AMM procedure was the primary cause of the error.
- Adverse weather conditions, including heavy rain, made the use of digital maintenance tablets difficult and less responsive.
- The maintenance information was difficult to interpret due to complex sentence construction and the need to navigate through various modification states.
- No physical check or independent verification was performed to confirm the spoiler was correctly deactivated.
- The technical logbook entry was incorrectly certified by an engineer whose approval did not cover the specific task.