The National Transportation Safety Board (NTSB) on Thursday warned Boeing and the Federal Aviation Administration (FAA) that the rudder control system on some 737 Next Generation and 737 Max 8 planes could fail or become limited. An urgent safety advisory has been issued.
The rudder controls the side-to-side movement of the aircraft's nose, also known as yaw motion.
The agency is in the midst of investigating a February accident in which the rudder pedal of a United Airlines Boeing 737 Max 8 “stuck” in the neutral position during a landing deployment at Newark Liberty International Airport in New Jersey.
At the time, the captain had to rely on the nose wheel steering tiller to control the plane's direction after touchdown, the NTSB said.
Pilots reported that the plane taxied to the gate “without incident” and all 155 passengers and six crew members were able to deplane. No injuries were reported.
As part of the investigation, NTSB investigators tested one of the crash plane's rudder control components at component manufacturer Collins Aerospace.
Researchers found that the functionality of the components was “significantly impaired” after testing in cold environments. Collins Aerospace then discovered that the parts had been incorrectly assembled during manufacturing.
As part of Boeing's 737 flight manual, pilots whose rudder becomes stuck or restricted are instructed to “suppress the stuck or restricted system.” [using] Maximizes the combined effort of both pilots. ”
However, NTSB investigators found that applying this amount of force during landing or deployment “results in large inputs to the rudder pedals and sudden, large, and undesired rudder deflections that can lead to unintentional loss of control or deviation from the runway.” “There is a possibility of deviations,” he said, expressing concern. . ”
In its recommendations, the agency suggested that aircraft manufacturers determine “appropriate flight crew responses other than applying maximum force” to such situations during flight and landing.
