U.S. agency calls for urgent action on Boeing 737 rudder systems

The National Transportation Safety Board on Thursday issued urgent safety recommendations directing the Federal Aviation Administration and Boeing to address the potential malfunction of rudder control systems on certain 737 Max and NG jets.

The recommendations stem from the independent safety agency’s investigation of a February incident in which a United Airlines pilot reported that the rudder pedals on a 737 Max 8 jet became stuck in a neutral position during landing at Newark Liberty International Airport. No injuries were reported to the 161 passengers and crew.

As part of the probe, NTSB investigators tested one of the rudder control components from the airplane, known as a rollout guidance actuator. After testing the actuator and an identical unit from another airplane in a cold environment, they found both had “significantly compromised” ability to function, including excessive moisture.

Collins Aerospace, which manufactured the component, later determined that a sealed bearing was incorrectly assembled during production, leaving the unsealed side more “susceptible to moisture that can freeze and limit rudder system movement.” Collins notified Boeing that more than 353 actuators the company had delivered to Boeing since February 2017 were affected. The rudder system is critical because it helps pilots maneuver the aircraft.

Boeing’s 737 flight manual instructs pilots who encounter issues with the rudder system to use maximum force to “overpower” the system. But if that type of force is applied during landing or rollout, it could cause problems, including “a sudden, large, and undesired rudder deflection that could unintentionally cause loss of control or departure from a runway,” the agency warned.

As a result, the NTSB said it’s recommending to Boeing that it determine appropriate flight crew responses besides applying “maximum pedal force” in those cases. The NTSB is also recommending that the company notify flight crews operating 737s with affected actuators that the rudder control system can jam due to any moisture that has accumulated inside the actuators and frozen.

In addition, the agency is recommending that the FAA determine whether actuators with incorrectly assembled bearings should be removed from airplanes. If the FAA makes that call, it should direct U.S. airlines to remove them until replacements are available and notify regulators in other countries where the jets operate.

United Airlines is the only U.S. carrier that had the component in its planes, and they have been replaced.

In statements, the FAA said it will convene a corrective action review board to determine next steps, while Collins Aerospace said it will continue to work closely with the NTSB and Boeing on the investigation and support Boeing and aircraft operators in mitigating operational impacts.

Boeing did not immediately respond to a request for comment.

These issues already surfaced in a preliminary report issued in March, when NTSB investigators said the captain was able to use “the nose wheel steering tiller to keep the airplane near the runway’s centerline while slowing to a safe taxi speed” after the pedals malfunctioned. After asking the first officer on the flight to check his rudder pedals, he reported the same problem.

Three days after the Feb. 6 incident at Newark, United conducted a test flight of the same aircraft there and was able to duplicate the rudder system malfunction. The NTSB was notified and opened an investigation.

The incident in Newark came just one month after a door panel blew out of a Boeing Max jet operated by Alaska Airlines. No passengers were seriously injured in that accident, but the calamity led to multiple federal investigations of Boeing’s safety and manufacturing systems. The FAA has restricted the number of 737 Max aircraft Boeing can build until the company meets certain quality and safety milestones.

Boeing 737 Max jets were also involved in two fatal crashes - one in 2018 in Indonesia and a second in 2019 in Ethiopia - in which a total of 346 people died.