Air Accidents Investigation Branch
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During the flare to landing at Belfast International Airport the co-pilot, who was Pilot Flying (PF), discovered that the rudder was extremely difficult to move. The commander immediately took control of the aircraft and used the nosewheel steering for directional control on the runway. Examination of the aircraft on the following day showed that the rudder was almost immoveable from either set of rudder pedals in the cockpit or by physically pressing on the rudder outside the aircraft.
A number of faults with the rudder control system were uncovered during the investigation but the major cause of the extreme rudder stiffness was the degradation of the steel rudder rear quadrant support bearings due to corrosion. The sealed nature of the bearings and their installed location precluded visual inspection of their condition. Moisture ingress in the vicinity of the bearings had likely contributed to their degraded condition. The installation of the rudder damper may also have contributed to the rudder stiffness, albeit to a lesser extent.
A Service Bulletin which recommended replacement of all flight control bearings with corrosion-resistant stainless steel bearings had not been embodied on the aircraft.
The operator took actions to ensure the continued airworthiness of its ATR fleet. The manufacturer also took, or has committed to taking, a number of safety actions to address issues identified during the investigation. These include updating the Illustrated Parts Data for some flight control bearings to specify stainless steel equivalents as the preferred part number, updating troubleshooting guidance and publishing a communication to remind operators of the existing recommended Service Bulletin.