On Thursday, the National Transportation Safety Board made urgent safety recommendations to The Boeing Company and the Federal Aviation Administration concerning the risk of a jammed or limited rudder control system in certain 737 aircraft.
United Airlines 737
The NTSB is looking into an incident that occurred on February 6, 2024, involving a United Airlines Boeing 737-8, a MAX variant, where the rudder pedals were “stuck” in a neutral position during the landing rollout at Newark Liberty International Airport in Newark, New Jersey. The captain utilized the nosewheel steering tiller to steer the aircraft upon landing. Fortunately, there was no damage to the aircraft, and none of the 155 passengers or six crew members were injured. A preliminary report outlining the details of the incident was released on March 12.
Presence of moisture in the actuators
NTSB investigators examined one of the rudder control components from the aircraft involved in the incident, specifically a rollout guidance actuator, at its manufacturer, Collins Aerospace. When the incident actuator was compared with a similar unit from a different airplane in a cold setting, the performance of both actuators was notably impaired.
The investigators discovered moisture present in both actuators, which resulted in their failure during the testing process. Collins Aerospace later concluded that a sealed bearing had been incorrectly installed during the production of these actuators, making the unsealed side more vulnerable to moisture that could freeze and hinder rudder system movement.
Collins informed Boeing that over 353 actuators supplied to them since February 2017 were impacted by this issue. The rudder rollout guidance actuator, located in the tail section of certain B-737NG and 737MAX aircraft, is responsible for regulating the rudder’s motion during category IIIB approach, landing, and rollout procedures. While it is not utilized for non-precision landings, the actuator remains mechanically linked to the rudder system.
Boeing’s Procedure for Jammed Rudder
Boeing’s 737 flight manual advises pilots facing a jammed or obstructed rudder to “overpower the jammed or restricted system [using] maximum force, including a combined effort of both pilots.” The NTSB raised concerns that applying such force during landing or rollout could lead to a substantial input on the rudder pedals, potentially resulting in a rapid, significant, and unintended rudder deflection that might inadvertently lead to loss of control or runway departure.
The NTSB has suggested that Boeing “determine appropriate flight crew responses besides applying maximum pedal force” in these situations during flight or landing. Furthermore, the NTSB recommended that Boeing inform flight crews operating 737s with the affected actuators about the possibility of the rudder control system jamming due to moisture buildup within the actuators that could freeze.
NTSB Recommendation
Additionally, the NTSB recommended that if the FAA concludes that the affected actuators should be removed, they should notify aviation regulators in other countries that oversee B737 operators and encourage them to mandate the removal of affected actuators until replacements can be provided.
Boeing’s downfall
Over the past five years, Boeing has faced numerous challenges, some of which have been tragic while others have been quite embarrassing. Many of these issues have had severe financial repercussions.
Two deadly incidents involving its 737 Max, one occurring in October 2018 and the other in March 2019, resulted in the loss of 346 lives and triggered a 20-month suspension of Boeing’s top-selling aircraft, along with a halt in deliveries to address a design flaw associated with the accidents.
Following that, Boeing was confronted with more inquiries concerning the quality and security of its aircraft. This investigation intensified on January 5 after an Alaska Airlines 737 Max experienced a door plug blowout shortly after takeoff. The incident prompted multiple federal investigations, one of which found the jet had left a Boeing plant without the four bolts required to secure the door stopper. Despite this, no one was killed or critically injured.
From then on, Boeing agreed to sign a guilty plea to federal criminal charges related to misleading the Federal Aviation Administration during the Max’s initial examination. The company’s agreement with the US Justice Department requires it to function under the close supervision of a monitor appointed by the court.
Click here to read the full report released by NTSB