- The NTSB issued an urgent warning to airlines that fly the Boeing 737.
- A piece of the rudder control system on 737 Next-Generation and 737 Max aircraft can lose functionality in cold weather conditions.
- The NTSB has recommended that the FAA “determine if actuators with incorrectly assembled bearings should be removed from airplanes.”
The National Transportation Safety Board Thursday issued an urgent warning to airlines that fly the Boeing 737, saying an issue first seen on a United Airlines flight in February could cause issues on other planes.
According to the NTSB, a piece of the rudder control system on 737 Next-Generation and 737 Max aircraft, the two most recent generations of the manufacturer’s best-selling plane, can lose functionality in cold weather conditions.
A United Airlines flight returning from Nassau, Bahamas, to Newark on Feb. 6 had its rudder pedals stuck in the neutral positions during the landing roll. The NTSB said the captain was able to control the plane using its nosewheel steering system. No injuries were reported to passengers or crew during that incident.
Even so, the agency investigated and found issues with the plane’s rudder system.
The agency said in a statement:
NTSB investigators tested one of the rudder control components from the incident airplane, a rollout guidance actuator, at the component’s manufacturer, Collins Aerospace. 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.
National Transportation Safety Board
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Collins Aerospace said more than 353 actuators assembled since 2017 were affected, according to the NTSB.
The NTSB directed Boeing to determine and notify airlines of appropriate pilot responses if a similar incident occurs and to alert pilots “that the rudder control system can jam due to moisture that has accumulated inside the actuators and frozen.”
The agency has also recommended that the Federal Aviation Administration “determine if actuators with incorrectly assembled bearings should be removed from airplanes, and if so, to direct U.S. operators to do so until replacements are available.”
The FAA said that United Airlines is the only U.S. operator that had the components, and “it is the FAA’s understanding that the units are no longer in service.”
The agency also said Thursday it accepted NTSB’s recommendation. “As a party to the investigation, the agency has been monitoring this situation closely,” the FAA said in a statement. “Tomorrow, we will convene a corrective action review board based upon the NTSB’s interim recommendations and determine next steps.”
This is the latest headache for Boeing, which is under pressure from an ongoing machinist strike and increased regulatory pressure from Capitol Hill in the wake of a January incident in which an Alaska Airlines 737 Max lost a piece of the fuselage during a flight.