US transport safety board warns that some Boeing 737 rudders could jam

US plane maker working with supplier to 'develop additional guidance to address' potential issue

About 350 parts, supplied by Collins Aerospace for some 737 Max and 737 NG aircraft, are affected by the issue, according to the NTSB. Reuters

The US National Transportation Safety Board has warned that a faulty component in some Boeing 737 aircraft could cause the plane’s rudder control system to jam.

About 350 parts are affected. They were supplied by Collins Aerospace, a unit of RTX, for some 737 Max and 737 NG aircraft, according to the NTSB. The agency issued urgent safety recommendations to the US Federal Aviation Administration and Boeing.

The FAA said United Airlines Holdings is the only US airline that had the affected parts. The agency said its “understanding” is that the carrier is no longer using them.

A sealed bearing on the components, known as actuators, was incorrectly assembled during production, according to the NTSB. That left the unsealed area more susceptible to moisture that could freeze and limit movement of the rudder system, the agency said.

Boeing said it is working with its supplier to “develop additional guidance to address” the potential condition with the rudder system. It told operators of a possible issue in August. “We will also ensure flight crews have the appropriate operating procedures,” a spokeswoman said.

A spokesman for RTX said the company will “continue to work closely with the NTSB and Boeing on this investigation,” adding it was supporting the plane maker and airlines to mitigate the impact on operations.

The issue is the latest headache for Boeing, which has been in crisis mode since January after a fuselage panel blew off a 737 Max aircraft shortly after take-off. The plane maker is also dealing with a contentious labour strike that has idled its jetliner factories near Seattle.

The NTSB said it discovered the flaw during its investigation of a February 6 incident in which rudder pedals on a 737 Max 8, operated by United Airlines, got stuck during landing at Newark Liberty International Airport in New Jersey. No one was injured and the plane was undamaged.

The NTSB said Boeing should examine its procedures for pilots who encounter similar scenarios. The agency also recommended that the company notify crews operating planes with the affected component that the system could jam during flight.

The safety board urged the FAA to determine whether the faulty parts should be removed from planes and, if so, direct operators to take action. In addition, the NTSB said the FAA should notify aviation regulators overseas if it determines removal is appropriate.

The FAA said it accepted the NTSB’s recommendation and that it would convene a review board on Friday to determine the next steps. The agency said it is a party to the NTSB’s probe and has been monitoring the situation closely.

Boeing shares were little changed in after-hours trading on Thursday. The stock is down around 40 per cent this year.