The National Transportation Safety Board (NTSB) has issued urgent safety recommendations to Boeing for some 737 aircraft, warning that critical flight controls could jam.
The recommendations were issued to both Boing and the FAA on Thursday. A recent NTSB investigation uncovered the potential for a jammed or restricted rudder control system. This is applicable on some 737NG and 737 MAX aircraft.
The risk of rudder malfunction relates to a manufacturing fault in a rudder actuator component supplied by Collins Aerospace.
The Incident Under Investigation
The NTSB’s recommendation action stems from an incident that occurred on February 6, 2024. A United Airlines Boeing 737-8 MAX was carrying 155 passengers and six crew members. It experienced a directional control problem during its landing at Newark Liberty International Airport.
As the aircraft touched down, the flight crew discovered that the rudder pedals had become unresponsive, essentially “stuck” in their neutral position.
The Pilot Flying managed to maintain directional control of the aircraft using the nosewheel steering tiller. As a result of this action, there was no damage to the airplane or injuries to the 155 passengers and six crewmembers.
Investigation Findings
As part of the subsequent investigation, the NTSB conducted tests on the aircraft’s rollout guidance actuator, a critical component of the rudder control system.
The results found that when exposed to cold conditions, both the incident actuator and a similar unit from another plane exhibited significant functional problems.
Investigators uncovered the presence of moisture within the failed actuators. This discovery led Collins Aerospace finding that a production error had resulted in incorrectly assembled sealed bearings.
This manufacturing flaw left the components vulnerable to moisture intrusion and potential freezing, which could severely restrict rudder movement under certain conditions.
The Scope of the Problem
The implications of this issue are far-reaching. Collins has informed Boeing that over 350 affected actuators have been delivered since February 2017. This potentially impacts a substantial number of both 737 NG and 737 MAX models currently in service worldwide.
This revelation has raised serious questions about the safety of these widely-used aircraft and the effectiveness of current quality control measures in the aerospace supply chain.
Current Procedures and Safety Concerns
Boeing’s current flight manual advises pilots facing rudder issues to use maximum force, including joint efforts by both pilots, to overcome the problem.
However, the NTSB has expressed grave concerns about this approach. Their concern focused on the application of extreme force during critical flight phases. When applied, especially during landing or takeoff, this could lead to sudden, large rudder deflections.
Such uncontrolled movements could potentially cause loss of control or runway departures.
NTSB’s Key Recommendations
In response to these findings, the NTSB has issued a series of crucial recommendations:
- Boeing is urged to develop alternative strategies for pilots facing rudder problems, moving away from the potentially dangerous “maximum force” approach.
- The aircraft manufacturer must alert all flight crews about the potential for rudder system jamming due to frozen moisture in the affected actuators.
- The FAA is called upon to evaluate whether affected actuators should be immediately removed from all aircraft in service.
- If removal is deemed necessary, the FAA should direct U.S. operators to replace these components as soon as possible.
- The NTSB also recommends that the FAA notify international aviation regulators about this critical issue and encourage similar actions globally to ensure worldwide air travel safety.
This is now a developing story.
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