Defective Rudder Actuators in Boeing 737s

B737 Rudder Failure Blog Picture

NTSB Raises Concerns Over Potential Defective Rudder Actuators in Boeing 737s

The National Transportation Safety Board (NTSB) recently issued an urgent safety recommendation concerning Boeing 737 aircraft, specifically addressing potential issues with the Collins Aerospace SVO-730 rudder rollout guidance actuators. This alert follows a serious incident in February 2024 at Newark Liberty International Airport (EWR), where the rudder pedals on a United Airlines 737 MAX 8 jammed during landing rollout. 

What Happened?

During the incident, the captain reported that the rudder pedals failed to respond to the normal application, raising serious concerns about the integrity of the rudder system. Subsequent tests at Collins Aerospace revealed that the malfunction was caused by moisture in the actuators, which became frozen due to incorrect assembly of a sealed bearing. This compromised the rudder system’s performance, especially after cold soaking. The tests concluded that this issue could impact multiple 737NG and 737 MAX aircraft with the affected actuator units.

B737-Rudder-System

The Potential Impact

According to the NTSB, more than 353 defective actuators were delivered to Boeing since February 2017, potentially affecting both U.S. and foreign operators. This discovery has led to significant concerns about the safety of certain Boeing 737NG and 737 MAX aircraft that are still flying with these faulty components.

The NTSB also raised the alarm that Boeing’s mitigation procedures for overcoming a jammed rudder during landing — applying maximum pedal force — could result in sudden, unwanted rudder deflections. In challenging conditions, such as during a high-crosswind landing or an engine-out scenario, the jammed rudder could cause the aircraft to veer off course, creating a potentially dangerous situation.

Current Status and Boeing’s Response

On August 28, 2024, Boeing informed the NTSB that 25 U.S.-registered planes were known to have the affected actuators installed. Of these, nine belonged to United Airlines, and the faulty parts had already been removed. The remaining 16 U.S. aircraft were leased to foreign operators, but there remains uncertainty about how many planes worldwide still carry the defective actuators.

While Boeing has reassured operators that 737 aircraft can be safely flown without the rudder rollout guidance actuator, they also acknowledged the issue and are working on a plan to remove and replace the faulty units across the fleet. Boeing determined that the faulty actuator does not pose an “immediate threat to safety,” but they are committed to reducing any unnecessary risks by replacing the affected units. 

NTSB’s Four Key Recommendations

To address the issue, the NTSB has issued the following recommendations:

1. Boeing should develop alternative flight crew responses beyond applying maximum pedal force during a jammed or restricted rudder situation.

2. Notify flight crews operating Boeing 737s with affected actuators that rudder control may become jammed due to moisture accumulation in the actuator.

3. The FAA should determine whether actuators with incorrectly assembled bearings should be removed from U.S.-operated planes, and if so, direct operators to remove them until replacement units are available.

4. If required, the FAA should notify aviation regulators globally to encourage foreign operators of Boeing 737 aircraft to remove faulty actuators as well.

What’s Next?

Boeing has committed to working on a replacement plan and sharing a timeline with both domestic and foreign operators. Meanwhile, pilots and operators are urged to remain cautious, particularly during landing rollouts, and to refer to any updated guidance provided by Boeing or the FAA.

The NTSB’s recommendations are part of a proactive effort to ensure that the Boeing 737 fleet remains safe and that any potential issues are addressed before they lead to accidents. While there was no damage to the United Airlines aircraft involved in the February 2024 incident, and no injuries were reported, this near-miss highlights the importance of staying vigilant and addressing even the smallest mechanical concerns in aviation.

Final Thoughts

Safety is paramount in the aviation industry, and this incident serves as a reminder that all components — big or small — must function flawlessly to ensure the safety of passengers and crew. As Boeing continues its efforts to replace the faulty actuators, pilots and operators are encouraged to follow any updated protocols and take extra precautions when flying affected aircraft.

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