Sept. 26 (UPI) — The National Transportation Safety Board Thursday issued “urgent” safety recommendations warning of the potential for rudder control system problems on some Boeing 737-MAX aircraft.
The NTSB said it issued the warnings to Boeing and the Federal Aviation Administration after discovering that rollout guidance actuators, a key rudder control component, were “significantly compromised” in tests on a pair of Boeing 737-8s, a variant of the manufacturer’s MAX series.
The tests were done in connection with a probe of a Feb. 6 incident in which the rudder pedals of a United Airlines Boeing 737-8 were “stuck” in their neutral position during a landing rollout at Newark Liberty International Airport, the agency said.
There was no damage to the airplane or injuries to the 155 passengers and six crew members in that incident, but the captain was forced to use the nosewheel steering tiller to control the airplane’s direction after touching down, investigators said.
The rollout guidance actuators are made by Collins Aerospace. The NTSB reported it found evidence of moisture in both actuators it tested, determining that a sealed bearing was incorrectly assembled during their production. This could resulting in leaving the unsealed side more susceptible to moisture that can freeze and limit rudder system movement.
Collins has told Boeing more than 353 actuators delivered since February 2017 could be affected by this condition.
The NTSB said it is “concerned” that MAX pilots who follow Boeing’s flight manual instructions to “overpower the jammed or restricted system [using] maximum force” during such rudder freezes could trigger “a sudden, large, and undesired rudder deflection that could unintentionally cause loss of control or departure from a runway.”
The FAA said it is aware of the warning told CNN it will “convene a corrective action review board based upon the NTSB’s interim recommendations and determine next steps” on Friday.
The warning was just the latest in a series of issues affecting the workhorse Boeing 737-MAX line.
A door panel blew out of a MAX jet operated by Alaska Airlines in January, an incident in which no one hurt but which triggered a round of safety investigations into the aircraft’s systems and manufacturing processes.
The reputation of 737-MAX also suffered a pair of severe blows in 2018 and 2019 when a total of 346 people died in a pair of fatal crashes in Indonesia and Ethiopia.