As Boeing works to address engine anti-ice issues with its 737 Max, the Federal Aviation Administration now says it is taking steps to address risks associated with the anti-ice system on 787s.

A proposed FAA rule released on 16 February relates to a problem involving missing seals that can allow hot air from 787 engine anti-ice systems to overheat multiple engine inlets.

The proposal, which comes after Boeing addressed the issue last year in memos to operators, would require airlines to inspect 787s for heat damage and to replace components as needed. If finalised, it would apply to all US-registered 787s – 110 jets, including 787-8s, 787-9s and 787-10s.


Source: Boeing

“The FAA has received a report indicating that damage was found during overhaul on multiple inlets around the [engine anti-ice] duct within the inlet aft compartment,” says the proposed rule. “After investigation, it was found that the seals between the inner and outer ducts, and between the outer duct and the aft compartment, were missing.”

Those missing seals enabled air from the engine anti-ice system to leak “into the aft compartment, exposing inlet components to high temperatures”, the proposal says. “This condition, if not addressed, could cause damage around the [engine anti-ice] duct, leading to reduced structural strength and departure of the inlet.”

Boeing in September last year notified operators of the risk by issuing Alert Requirements Bulletins. Those documents call for operators to inspect some 787s for heat damage, and if necessary to replace seals and repair or replace engine inlets.

The agency’s proposed rule would require operators complete the steps in Boeing’s bulletins. But while those bulletins applied to just some 787s, the FAA’s proposal seeks to encompass “all model 787-8, 787-9 and 787-10 airplanes”, it says.

The FAA calls the move an “interim action” to be taken as it completes an ongoing investigation.

Boeing did not respond to a request for comment.

The company and FAA have been busy addressing engine anti-ice concerns involving the company’s 737 Max.

Last year, the FAA issued an airworthiness directive requiring airlines to instruct pilots not to use the Max’s anti-ice system unless in “actual or anticipated icing conditions”. Use in dry air for more than 5min could result in “engine inlet cowl temperatures exceeding design limits” and failure of the engine inlet inner barrel, the FAA said.

The company also last year asked the FAA to temporarily exempt its in-certification 737 Max 7 from some airworthiness rules. The exemption, if approved, would have allowed regulators to certificate the Max 7 despite it not initially meeting regulations due to the anti-ice system problem.

Under criticism from lawmakers and pilot unions, Boeing backed down, rescinding its exemption request in January. Instead, it is working on a technical fix expected to be completed within one year.

On 15 February, FlightGlobal reported another engine anti-ice system issue involving the 737 Max, this one related to the risk that failure of the jets’ standby power system control unit could make the anti-ice system inoperative.

Boeing addressed that issue in a November 2022 bulletin to customers. The FAA now intends to mandate Boeing’s fix for the problem.