SAN FRANCISCO — The rudder control system on certain 737 Boeing models have been found jammed or restricted, prompting the US National Transportation Safety Board (NTSB) to issue urgent safety recommendations to the aircraft manufacturer and to the Federal Aviation Administration (FAA).
The NSTB advisory follows an incident on February 6 in which the rudder pedals on a United Airlines Boeing 737-8, a MAX variant, were “stuck” in their neutral position during the landing rollout at Newark Liberty International Airport in New Jersey.
NTSB investigators tested a rollout guidance actuator, one of the rudder control components from the incident airplane, at the component’s manufacturer, Collins Aerospace. When the incident actuator and an identical unit from another airplane were tested in a cold environment, the actuators’ function was significantly compromised.
Collins Aerospace subsequently determined that a sealed bearing was incorrectly assembled during the production of the actuators, leaving the unsealed side more susceptible to moisture that can freeze and limit rudder system movement.
It notified Boeing that more than 353 actuators that had been delivered to Boeing since February 2017 were affected by this condition.
The rudder rollout guidance actuator, which is installed in the tail of some B-737NG and 737MAX airplanes, is designed to control the rudder’s movement during category IIIB approach, landing and rollout operations. Although it is not used in non-precision landings, the actuator remains mechanically engaged with the rudder system.
NTSB has recommended that Boeing notify flight crews operating 737s with affected actuators, while the FAA will determine if actuators with incorrectly assembled bearings should be removed from airplanes.
If the FAA determines the affected actuators should be removed, aviation regulators in other countries should notify airlines using B737 airplanes to request the removal of the affected actuators until replacements are available, NTSB added. — September 27, 2024