In a significant setback for Boeing Co., already grappling with an ongoing machinists' strike and persistent safety concerns, the National Transportation Safety Board (NTSB) has issued critical safety recommendations for the rudder control systems on certain 737 aircraft.
The advisory targets both Boeing and the Federal Aviation Administration (FAA), highlighting the potential for jammed or restricted rudder control systems on specific B-737NG and 737MAX models. These systems, supplied by Collins Aerospace, have come under scrutiny following a February 6, 2024, incident involving a United Airlines Boeing 737-8, a MAX variant.
Investigations revealed that more than 353 actuators delivered by Collins to Boeing since February 2017 are affected. During the February incident, the rudder pedals of the United Airlines 737-8 became "stuck" in their neutral position upon landing at Newark Liberty International Airport, New Jersey. The captain utilized the nosewheel steering tiller to maintain control, preventing any damage or injuries to the 155 passengers and six crew members on board.
As part of their ongoing investigation, NTSB officials tested one of the rudder control components, the rollout guidance actuator, at Collins Aerospace. This component is crucial for controlling the rudder during Category IIIB approaches, landings, and rollout operations but remains engaged even during non-precision landings.
The cold-environment tests conducted on the incident actuator and an identical unit from another aircraft revealed significant functional compromise due to moisture presence. The investigation traced the issue to incorrectly assembled sealed bearings during production, making them susceptible to moisture ingress, which can freeze and hinder rudder system movement.
Boeing's 737 flight manual directs pilots to "overpower the jammed or restricted system [using] maximum force, including a combined effort of both pilots". However, the NTSB warns that applying such force during landing or rollout could result in unintended large rudder deflections, potentially causing a loss of control or runway departure.
In response, the NTSB has recommended that Boeing develop more refined flight crew procedures beyond the current directive of applying maximum pedal force. Additionally, it has urged Boeing to inform flight crews about the potential for rudder system jamming due to moisture accumulation in the actuators. The FAA is also advised to evaluate whether actuators with the incorrectly assembled bearings should be removed from service and to mandate their replacement if necessary.
Furthermore, should the FAA opt for actuator removal, the NTSB has recommended notifying international aviation regulators overseeing B737 operations to enforce similar measures until replacements are secured.
This development compounds Boeing's challenges, as approximately 33,000 machinists remain on strike since September 13, demanding better pay and benefits. This strike—the first since 2008—has already disrupted Boeing's commercial airplane production and prompted the company to consider cost-cutting measures, including a hiring freeze, reduced supplier spending, and potential temporary furloughs to mitigate the impact.
