Hot Under the Collar

U.S. regulators are warning operators of Boeing 737-MAX family aircraft to limit use of the jets’ engine inlet and anti-icing system in dry air.

The FAA contends overheating of the engine inlet leading edge—that part of the engine assembly heated by bleed-air tapped from the powerplant’s hot-section—occasions risk of parts separating from the engine’s housing.

In 2018, a Southwest Airlines passenger perished after part of the engine housing of an older Boeing’s 737 model jet aboard which she was traveling separated, breaking the window beside which she was seated and striking her. The referenced instance was ascribed, ultimately, to a broken fan-blade.

The FAA conceded it has, to date, received no reports of 737 MAX engine inlets overheating. The agency’s concerns derive, rather, of a June 2023 flight-testing analysis by which the potential for such failures was ostensibly identified.

The Federal Aviation Administration alleges the risk to the flying public is sufficiently serious to merit issuance of a mitigating order, likely an Airworthiness Directive, in only 15-days—and without solicitation of public comment.

After the vague and reductionist fashion characteristic of the agency, the FAA set forth the heated inlets of the CFM International LEAP-1B turbofan engines by which every extant iteration of Boeing’s 737-MAX family of narrow-body jets is powered could separate and strike an aircraft window, causing decompression and instantiating a hazard to passengers occupying window seats.

Boeing maintains overheating of the LEAP-1B inlets—which are produced by Boeing, not CFM International—a joint venture of General Electric and France’s Safran—can occur only under “very specific” conditions and was wholly unheard of until recently.

In a statement, the Arlington, Virginia-based aerospace titan asserted: “Boeing has identified measures to mitigate the potential issue [of engine inlet anti-ice systems] and is working with our customers to deploy those measures while a permanent fix is developed.”

The FAA is reportedly dictating changes to 737-MAX Aircraft Flight Manuals (AFM) requiring pilots to eschew use of engine inlet anti-ice for more than five-consecutive minutes in dry air.

The FAA states: “ … during certain combinations of altitude, total air temperature, and engine settings, the engine inlet inner-barrel could be heated beyond its design limit … which could cause the inlet-barrel to fail and damage the inlet cowl.”

The FAA further suggests parts separating from aircraft engine housings could break not only windows, but possibly strike vital aircraft giblets, causing pilots to lose control of their machines.

The FAA should have published its hastily-contrived rule in the U.S. Federal Register on Thursday.

FMI: www.faa.gov