More than 40 foreign operators of Boeing 737 aircraft may be using planes with rudder components that could pose safety risks, a US federal agency has warned.
The National Transportation Safety Board (NTSB) issued urgent safety recommendations about the potential for a jammed rudder control system after a February incident involving a United Airlines flight.
The NTSB added it had learned two foreign operators suffered incidents in 2019 involving rollout guidance actuators.
“We are concerned of the possibility that other airlines are unaware of the presence of these actuators on their 737 airplanes,” NTSB Chair Jennifer Homendy said in a letter to Federal Aviation Administration (FAA) Administrator Mike Whitaker.
The issue is the latest setback for Boeing, which has faced a series of safety questions after a mid-air emergency in January involving a new Alaska Airlines 737 MAX 9 missing four key bolts.
The NTSB is investigating an incident in February in which the rudder pedals on a United 737 MAX 8 were “stuck” in the neutral position during a landing at Newark. There were no injuries to the 161 passengers and crew.
Boeing shares fell 2.7 per cent on Monday.
The NTSB said there were no longer any 737s flying with US airlines with the affected actuators, which were installed in some 737 MAX and prior-generation 737 NG planes that included an optional landing system.
But it warned that 271 impacted parts may be installed on aircraft in service operated by at least 40 foreign air carriers and 16 may still be installed on US-registered aircraft and up to 75 may have been used in aftermarket installation.
The carriers that may be using the parts were not identified.
The European Union Aviation Safety Agency (EASA) said on Tuesday it was aware of the NTSB report. “EASA is in close contact with the FAA and will take action as needed,” a spokesperson said.
Ms Homendy, who spoke to Mr Whitaker about the problem last week, said she was concerned the FAA "did not take this issue more seriously until we issued our urgent safety recommendation report."
The FAA insisted it was taking the NTSB recommendations seriously and it was scheduled to do additional simulator testing in October after the corrective action review board met on Friday.
United said last week the rudder control parts at issue were in use in only nine of its 737 aircraft originally built for other airlines and the components were all removed earlier this year.
Boeing, which declined to comment on Monday, said last week it had informed affected 737 operators of a "potential condition with the rudder rollout guidance actuator" in August.
