"The Federal Aviation Administration is mandating a new round of safety fixes before Boeing's 737 MAX jets can return to the air, this time targeting assembly line lapses that could result in a dual engine power loss in the event of a lightning strike."
In other words, a separate series of 737 MAX crashes could potentially occur apart from the MCAS software pushing the plane down, e.g.
In this case, the FAA directive (posted Tuesday in The Federal Register) requires Boeing to inspect and fix a metallic lining that serves as a shield against lightning strikes for engine control wiring. In this case, the evident cuts and tears in the aluminum foil conductor would prevent a protective Gaussian "pillbox" surface from being formed, i.e. to cover the engine attachments on the wings. Such a pillbox, which we teach in basic electrostatics, spreads charge evenly over the relevant surfaces so that it dissipates without incident. A tear or discontinuity in the conductor defeats the protective purpose, allowing the lightning charge to be conducted into the engines' wiring - with the likely resulting loss of power in the engines.
As noted in the WSJ piece, the FAA document covers 128 MAX 737 jets currently grounded in the U.S., but is also applicable to all 737 MAX aircraft assembled so far. The reason for the latter? Because "the entire fleet may be affected by the identified unsafe condition."
The FAA estimates a time of 12 hours to check and repair each foil tear on each, and still expects the planes to be ready "by mid 2020" -which I personally believe borders on fantasyland, Pollyanna expectation. Why? Because there remains the problem with two thirds of MAX jets having "some type of debris in their fuel tanks". This was revealed in the course of separate inspections of hitherto undelivered planes and can no more be ignored than the torn aluminum conducting foil. That, plus the complications of getting the MCAS software to work in the context of an aerodynamically flawed design could take years to resolve, if ever.
Oh yeah, then there is the additional problem of relocating the wiring bundles - which the FAA (if it has good sense and really wants no more crashes) is leaning to. The wire bundles are located behind the cockpit and under the cabin floor. The need for relocating the wiring is because they help to control movable panels in the tail and power other related systems. This is in at least a dozen locations, from the rear of the aircraft to the main electronics compartment beneath the cabin and behind the cockpit. Any short circuit or "arcing" of the current between the wires has the potential to cause control problems for pilots which the MCAS may not be able to correct.
Estimated time to fix each in terms of relocation? The FAA allows some 2 weeks per plane. Do the math: 128 jets currently grounded in the U.S. alone, with wiring relocated, and you will see the timeline stretches out for a lot longer than "mid 2020".
The MAX 737 ready by this summer? NO way in this alternate universe- or any other!
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