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A different flaw in the MAX’s engine anti-ice system design drew scrutiny in January and forced the company to drop a request for an exemption from key safety regulations. And now, it’s not just the MAX with an engine anti-ice system problem. Airlines have reported a separate issue with a similar system on Boeing’s 787 Dreamliner that has caused what the FAA calls “relatively minor” damage to the engine inlets on some two dozen of these widebody jets in service.

Though the FAA considers neither problem to be an immediate risk to flight safety, in February it issued separate notices of two proposed airworthiness directives to require the fix for the engine anti-ice system on the MAX and to lay out inspection and repair procedures for that system on the 787, pending a redesign that provides a permanent fix… When there is an immediate safety risk, the FAA issues a more urgent emergency directive that must be acted upon before further flight. Jets are grounded until it’s dealt with. That’s not the case with these two proposed airworthiness directives. Indicating that the risk is considered slight, both of the proposed directives will be open for public comments until April. Only after that will action be mandated…

On the MAX, the proposed FAA directive states that Boeing identified a potential single point of failure when it reviewed the internal design of the unit that provides a backup power supply to aircraft systems if the primary electrical system fails. Such a failure could potentially result in the loss of the anti-ice systems on both engines, with no indication or warning that would alert the pilots, the FAA directive states… In November 2022, Boeing sent a service bulletin alerting airlines and describing the required fix, which the FAA will now mandate…

Unlike this MAX issue, the fault discovered on the 787 Dreamliner has resulted in actual damage to engines on passenger aircraft. The FAA airworthiness directive on the 787 states that “damage was found during overhaul on multiple inlets around the Engine Anti-Ice duct within the inlet aft compartment.” Rather than a production issue, it was a matter of the seals being insufficiently durable. Even when the plane was flying in dry air and the anti-ice system was not switched on, the seal degradation led to hot air leaking into the inlet compartment, “exposing inlet components to high temperatures,” the FAA states. Boeing said this resulted in “thermal damage and discoloration to a limited area of the surrounding composite and metallic structure inside the inlet….” The FAA’s proposed airworthiness directive warns that heat damage to the inlet structure could lead to “reduced structural strength and departure of the inlet from the airplane.”

“Departure of the inlet” is a bland way of describing the front of the pod around the engine fan detaching, potentially striking the jet’s wing, tail or fuselage. Such disintegration could result in “subsequent loss of continued safe flight and landing or injury to occupants,” the airworthiness directive states…

“A separate question is how this flaw with the 787 anti-ice duct seals and the single point of failure in the backup power supply on the MAX slipped through the FAA’s original certification of these aircraft.”

Business Insider also reports that Boeing “is holding off on a planned expansion of production for its 737 Max planes after an Alaska Airlines flight lost a chunk of the plane while airborne in January.”