The National Transportation Safety Board issued “urgent safety recommendations” for some Boeing 737 planes including the 737 MAX.
The agency said that some flight controls can become jammed.
An actuator that is attached to rudders on some 737 NG (Next Generation) and 737 Max planes could not work, CNN reported. Pilots on board a United Airlines flight in February said their rudder pedals were stuck in a neutral position.
No one was hurt and the pilot controlled the aircraft using the nosewheel steering system, USA Today reported.
The actuator was manufactured by Collins Aerospace, according to the NTSB.
The issue crops up in cold weather.
“When the incident actuator and an identical unit from another airplane were tested in a cold environment, the actuators’ function was significantly compromised. Investigators found evidence of moisture in both actuators, which failed testing. Collins Aerospace subsequently determined that a sealed bearing was incorrectly assembled during production of the actuators, leaving the unsealed side more susceptible to moisture that can freeze and limit rudder system movement,” the NTSB said, according to USA Today.
There were more than 350 defective parts sent to Boeing but how many were used is not clear, The New York Times reported.
Collins Aerospace responded with a statement to the newspaper which read, “We have and continue to work closely with the N.T.S.B. and Boeing on this investigation. We are supporting Boeing and operators to mitigate operational impacts.”
The company said the actuator is part of a system that “includes layers of redundancy.”
The NTSB said Boeing had a procedure in place if the rudder jammed.
“Boeing’s 737 flight manual instructs pilots confronted with a jammed or restricted rudder to ‘overpower the jammed or restricted system (using) maximum force, including a combined effort of both pilots,” the agency said.
But the NTSB said that having to hit the pedals so hard during landing or a rollout “could result in a large input to the rudder pedals and a sudden, large, and undesired rudder deflection that could unintentionally cause loss of control or departure from a runway,” CNN reported.
The NTSB recommended that Boeing come up with a different fix and warn pilots about the potential issue with the rudder.
The FAA is monitoring the situation and will start a review board based on the NTSB’s recommendations.
United Airlines is the only US carrier that has 737s with the faulty parts but are no longer in use, CNN reported.
Boeing had several issues in the past year including when a door plug came off an Alaska Airlines 737 Max midflight. The FAA also found that there were dozens of issues during the manufacture of the 737 Max planes, the Times reported.
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