What happened
On 15 May 2014, an ATR 72-212 A, registration EI-FCY, was conducting a scheduled passenger flight from Cork Airport to Manchester Airport. During the final approach to Runway 2D, the aircraft completed a normal landing; however, as the aircraft decelerated, it began to drift toward the left side of the runway centreline.
The commander took control from the co-pilot and attempted to maintain directional control using rudder and nosewheel steering. Despite these efforts, the aircraft continued to deviate left, prompting the commander to apply the brakes and bring the aircraft to a halt on the left side of the runway. There were no injuries to the 48 passengers or 4 crew members on board, and no damage was sustained by the aircraft.
Following the stop, the crew identified fault lights on the overhead panel indicating that the Multifunction Computer (MFC) modules 1B and 2B had failed. After resetting these modules, the crew was able to taxi the aircraft to the terminal without further issues.
The investigation
The investigation focused on the simultaneous failure of the MFC 1B and 2B modules. The AAIB established that this specific dual failure renders the weight-on-wheels system unavailable, which in turn makes the nosewheel steering inoperative.
During the landing roll, the crew noted that several engine indications were missing from the Engine and Warning Display (EWD). While the aircraft's flight manual suggests that rudder remains effective above 40 knots, the investigation determined that at the speed at which the commander took control, rudder authority alone was likely insufficient to counteract the deviation.
Findings
- The dual failure of MFC modules 1B and 2B caused the weight-on-wheels system to become unavailable.
- This failure directly resulted in the loss of nosewheel steering functionality.
- The crew was not aware of the system failure until after the aircraft had already deviated from the runway centreline.
- The aircraft's speed during the deviation was likely too low for the rudder to maintain sufficient directional control without steering assistance.