The issue involves Boeing's 737, 737 -600/-700,-800,-900, 900ER, 737NG and MAX 8, MAX 9 aircraft equipped with Collins Aerospace SVO-730 RRGAs, both in the US and around the world. According to the NTSB, there are more than 40 airlines outside the US that are operating potentially affected aircraft.
The issue came to light after a incident on a Boeing 737 MAX 8, where the flightcrew were unable to move the rudder pedals during landing rollout. Following a post-incident investigation, it is thought the Collins Aerospace SVO-730 RRGA was the source of the flight control restriction. The FAA says RRGA provides rudder inputs during landing rollout, where directional guidance is provided by the autoflight system after touchdown on CAT IIIB equipped aeroplanes. The aeroplane was equipped with the RRGA, but not electrically connected to the Digital Flight Control System (DFCS).
The FAA said that airlines should instruct pilots that the rudder control system could potentially become jammed or restricted in flight or during landing due to moisture that could accumulate and freeze in the RRGA actuator. If the rudder restriction condition is encountered in flight, Boeing recommends suggests pilots should follow the Jammed or Restricted Flight Controls Non-Normal Checklist (NNC). If this rudder restriction is encountered on the ground, use differential braking to maintain the runway centerline. Flight crews should avoid using nosewheel steering above 100 Knots Indicated Airspeed (KIAS) unless necessary for aeroplane control as a potential for overcontrol exists.
