NTSB Issues Urgent Safety Recommendations on Boeing 737 Rudder System
9/26/2024
​​​Rudder control system could jam or become restricted on some 737NG and 737MAX airplanes

WASHINGTON (Sept. 26, 2024) — The National Transportation Safety Board Thursday issued urgent safety recommendations to The Boeing Company and the Federal Aviation Administration in response to the potential for a jammed or restricted rudder control system on some 737 airplanes.

The NTSB is investigating a Feb. 6, 2024, incident 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, Newark, New Jersey. The captain used the nosewheel steering tiller to control the airplane’s direction after touching down. There was no damage to the airplane or injuries to the 155 passengers and six crew members. A preliminary report detailing the circumstances of the event was published on March 12.

NTSB investigators tested one of the rudder control components from the incident airplane, a rollout guidance actuator, 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.

Investigators found evidence of moisture in both actuators, which failed testing. Collins Aerospace subsequently determined that a sealed bearing was incorrectly assembled during production of the actuators, leaving the unsealed side more susceptible to moisture that can freeze and limit rudder system movement.

Collins notified Boeing that more than 353 actuators that Collins had 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.

Boeing’s 737 flight manual instructs pilots confronted with a jammed or restricted rudder to “overpower the jammed or restricted system [using] maximum force, including a combined effort of both pilots.” The NTSB expressed concern that this amount of force applied during landing or rollout could result in a large input to the rudder pedals and a sudden, large, and undesired rudder deflection that could unintentionally cause loss of control or departure from a runway.