I have a theory that could explain the AOA sensor malfunction indication and the crashes, while also explaining why MCAS is wrongly accused of being the main culprit.
If you look at the position of the engine intakes on the MAX 8, they have been brought forward and up, to maintain ground clearance despite installing a larger fan.
The MCAS system has been added to counter the balance effects compared to the -800, but let's leave this aside for a minute and focus purely on aerodynamics.
My theory is that due to the new position and size of the fan, where the fan intake's upper edge is protruding above the wing's extrados even when the aircraft is level VS. ram air, the MAX 8's engines may be too high and sucking a lot of ram air that previously came into contact with the wing to contribute to lift generation, causing the wing to locally stall prematurely. In addition, it's possible that the position of the new engines vis a vis the wings is causing ram air to become turbulent ahead of the wing and creating a shadow effect for the wing sections situated behind the engine.
Basically, my theory is that the higher position of the engine intakes is reducing the flight envelope of the MAX 8 by causing premature, undetected stalls.
In my flight training days, we would practice the powered stall recovery with the instructor and this reminds me of that phenomenon.
-it explains why the Lion Air aircraft went out of envelope in the climb after take-off: an already high angle of attack during climb, followed by a local undetected stall of the wing, which expands into a power-on stall potentially supported by flap retraction.
-The AOA sensors indicate a malfunction because they are outside preset parameters. Essentially, they are not malfunctioning, but they appear to be malfunctioning as the aircraft is in a stall but not within the expected parameters of a stall.
-The trim may be running amock and contributing to a difficult recovery, again, because it is operating outside the parameters.
Please look at the high position of the engine intakes and compare them to the -800.
They are crazy high and imagine how they will be shadowing a good portion of the wing's leading edge in a climb with a higher angle of attack.https://static.seattletimes.com/wp-cont ... 60x967.jpg
Last edited by Waterbomber2
on Wed Mar 13, 2019 4:23 am, edited 2 times in total.