Safety Board Warns of Rudder Control Defect in Some Boeing Planes

The National Transportation Safety Board on Thursday issued a safety alert and recommendations for some Boeing planes, warning that a defect could cause the rudder control system that helps steer the aircraft to jam.

The warning applies to some of the company’s 737 Max and 737NG jets. It stems from the agency’s investigation into a United Airlines Boeing 737 Max 8 that experienced “stuck” rudder pedals while landing at Newark Liberty International Airport in February.

The safety board said it had been notified that more than 350 of the defective parts were delivered to Boeing, but it was not immediately clear how many planes with the affected component might be in service. The Federal Aviation Administration said it believed United was the only U.S. operator that had the faulty parts, and United said it had removed the components from its nine affected planes.

The safety board urged the F.A.A. to determine whether the faulty parts should be removed from service and, if so, to mandate that U.S. operators replace them. It also recommended informing international aviation regulators to encourage similar actions. The F.A.A. said in a statement that it had “been monitoring this situation closely” and would convene a panel to determine its next steps.

The warning adds to a string of safety woes for Boeing, which is already under intense scrutiny from regulators after incidents including a panel that blew off a jet midair this year. An audit conducted by the F.A.A. after that incident found dozens of problems throughout the 737 Max’s manufacturing process.

The safety board opened its investigation into the rudder control issue on Feb. 6, after the captain of a 737 Max 8 had to use the nose wheel steering tiller to maintain control of the plane when the rudder pedal became stuck while landing at Newark. A plane’s rudder control is primarily used on takeoff and landing to maintain the direction of the plane’s nose.