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The 737Max's design decisions seem to have been driven by their desire to maintain their 737NG type-rating. So even though it is aerodynamically a different ai

The 737Max's design decisions seem to have been driven by their desire to maintain their 737NG type-rating. So even though it is aerodynamically a different aircraft (with the engines further out), it mimics the 737NG with an effective emulator. For pilots certified on the 737NG, apparently minimal retraining is required to fly the 737Max. Using this analogy, the MCAS system was seemingly put in place to behind-the-scenes manage a flight-envelope condition on the Max that would not happen on the NG. So what happens when the 737Max hardware has a failure? How is the failure condition reported and managed by the flight crew? Are all failures on the 737Max passed through like they were 737NG failures? Does the flight crew respond as if they were flying a 737NG or a 737Max? Correctly mimicing a 737NG during proper flight and under failure conditions seems like a tall order.

msbarnett 7y ago
This is somewhat of a misunderstanding of the situation. The 737Max was built to provide a more fuel efficient model compatible with all of the 737-sized gates and etc stuff airlines owned. They did this by slapping bigger engines on, but to make them fit they pushed them forward of the wing (can’t make the plane taller or it doesn’t fit all the etc it’s supposed to be compatible with). Big, front positioned engines messed up the aerodynamics. Now, at speed, as a plane got closer to (but not at) the stall angle, forces suddenly inverted, and it became much easier to pitch up into a stall than push down away from it. This violated FAA rules that say for a commercial plane to be certified, at any point short of a stall it must always be harder to pull into it than push out. Boeing decided to add some software to automatically push the nose down when you get to the force inversion point. This uses the stabilizers to add force to the stick, so the pilot always has that extra force making it easier to push out of a stall than pull into it, meeting the FAA requirement. This is MCAS. Thus MCAS is in no way a “737NG emulator”. You could call the plane a 797 and you’d still need it to meet fundamental certification requirements about stick forces. Ie) it’s not so much mimicking an older 737 as it is just pretending to be a sanely designed commercial airframe at all. The type certification stuff only enters into it when Boeing didn’t want to tell people about MCAS because it might have caused them to think harder about the need for more training, the lack of which was a selling point for them.

msbarnett 7y ago

This is somewhat of a misunderstanding of the situation. The 737Max was built to provide a more fuel efficient model compatible with all of the 737-sized gates and etc stuff airlines owned. They did this by slapping bigger engines on, but to make them fit they pushed them forward of the wing (can’t make the plane taller or it doesn’t fit all the etc it’s supposed to be compatible with). Big, front positioned engines messed up the aerodynamics. Now, at speed, as a plane got closer to (but not at) the stall angle, forces suddenly inverted, and it became much easier to pitch up into a stall than push down away from it. This violated FAA rules that say for a commercial plane to be certified, at any point short of a stall it must always be harder to pull into it than push out. Boeing decided to add some software to automatically push the nose down when you get to the force inversion point. This uses the stabilizers to add force to the stick, so the pilot always has that extra force making it easier to push out of a stall than pull into it, meeting the FAA requirement. This is MCAS. Thus MCAS is in no way a “737NG emulator”. You could call the plane a 797 and you’d still need it to meet fundamental certification requirements about stick forces. Ie) it’s not so much mimicking an older 737 as it is just pretending to be a sanely designed commercial airframe at all. The type certification stuff only enters into it when Boeing didn’t want to tell people about MCAS because it might have caused them to think harder about the need for more training, the lack of which was a selling point for them.