The Federal Aviation Administration (FAA) issued a safety alert Tuesday over the potential for limited or jammed rudder movement on certain Boeing 737 airplanes.
This follows the National Transportation Safety Board (NTSB) on Sept. 26 urging the FAA and Boeing to issue safety recommendations after some 737 airplanes experienced jammed or restricted rudders.
According to the FAA, at issue is an optional system on some Boeing Model 737 series airplanes equipped with the Collins Aerospace SVO-730 Rudder Rollout Guidance Actuators (RRGA). The RRGA “provides rudder inputs during landing rollout, where directional guidance is provided by the autoflight system after touchdown,” they said in the recent alert.
The FAA said preliminary findings revealed the jammed rudder was likely due to moisture entering the actuator and freezing during the flight. They warned that Boeing 737 airplanes with the SVO-730 RRGA mechanism are at risk of the same. They said the same planes with the RRGA actuator removed were unaffected.
Officials also recommended that flight crews follow the Jammed or Restrict Flight Controls Non-Normal Checklist if the condition is encountered during flight or use differential braking to keep the plane on the runway’s centerline if it is encountered after a landing, in addition to other technical recommendations.
According to the NTSB, the RRGA actuators were installed in the tail of some Boeing 737NG and 737MAX airplanes. Upon investigation of the moisture build-up, Collins Aerospace determined that a sealed bearing in their actuator was incorrectly assembled during production, leaving the unsealed side at risk of collecting moisture.
According to the NTSB, the aerospace company notified Boeing that more than 353 actuators had been delivered to Boeing since February 2017.
NTSB safety officials had recommended that the FAA determine whether the actuators at issue should be removed from airplanes, direct U.S. operators to do so if needed, and notify other operators outside the United States.
The recent FAA alert didn’t address whether the actuators should be removed.
On Sept. 30, NTSB officials said 271 impacted parts were likely installed on airplanes in service and operated by at least 40 foreign air carriers. In addition, 16 may be installed on U.S. registered airplanes, and up to 75 may be used in aftermarket installations.
Boeing on Tuesday said it is working under the oversight of the two agencies and has “reminded operators of the proper actions that flight crews should take if they encounter rudder restriction.”
In August, the airplane manufacturer notified affected 737 operators of a “potential condition with the rudder rollout guidance actuator.”
In a statement last month, United Airlines said the RRGA actuators were only in nine of its 737 aircraft, initially built for other airlines. However, the actuators have since been removed.
The FAA also said Tuesday that an Aeromexico Boeing 737 MAX experienced sensations in the flight deck after a rudder pedal malfunction.
According to the NTSB, a Feb. 6 incident in which the rudder pedals on a United Airlines Boeing 737-8 were stuck in the neutral position during landing at Newark Liberty International Airport is still under investigation. No damage to the plane or injuries to its passengers and crew were reported.
Reuters contributed to this report.