What happened
On 30 June 2016, an Airbus A319-111, registration G-EZEW, departed Bristol Airport for Lisbon, Portugal. The aircraft was operating a commercial passenger flight with 144 passengers and 6 crew members on board. During the initial climb phase, the Pilot Flying (PF) requested the retraction of the landing gear. In response, the Pilot Monitoring (PM) mistakenly moved the flap lever to position 0.
This action caused the slats and flaps to begin retracting while the aircraft was at a low altitude of approximately 190 ft. As a result, the aircraft's pitch increased and the airspeed began to drop. The PF responded with a nose-down input to maintain speed, preventing the airspeed from falling below 153 kt. After the flaps were fully retracted, the PF noticed a significant increase in the minimum selectable speed (Vls) and instructed the PM to re-extend the flaps to position 1. While the slats began to extend again, the flaps remained retracted due to the aircraft's system logic. The crew stabilized the climb by increasing thrust to the TOGA setting and eventually engaged the autopilot.
The investigation
The investigation established that the PM had been preoccupied with thoughts of a previous flap mis-selection event that had occurred at the same airport. This mental preoccupation acted as a trigger, leading to an action slip where the PM performed the incorrect lever movement while intending to retract the gear.
Data analysis showed that at the moment of the error, the aircraft's angle of attack and airspeed were within a range that prevented the Alpha/Speed lock protection from inhibiting the slat retraction. The investigation also noted that the operator had identified this type of error as a vulnerability in highly practiced, routine tasks that can be performed automatically without conscious thought.
Findings
- The primary cause of the incident was a pilot error involving the inadvertent movement of the flap lever to position 0.
- The PM's focus on a previous similar incident served as a cognitive trigger for the mis-selection.
- The aircraft's Alpha/Speed lock protection did not activate because the airspeed and angle of attack were not yet at the critical thresholds required to inhibit the movement.
- The crew's recovery actions, including corrective pitch and increased thrust, were effective in maintaining safe flight parameters.
Safety action
Following the incident, the operator implemented several measures to prevent recurrence, including:
- Reviewing training and guidance for managing aircraft in low-energy states at low altitudes.
- Implementing training focused on 'active monitoring' of switch and lever selections.
- Amending Standard Operating Procedures (SOPs) to ensure the correct lever is identified before movement.
- Developing training to help crews manage distractions during routine tasks.