I’m reading about the Boeing 737 Max 8 incidents involving Lion Air Flight 610 and Ethiopian Airlines Flight 302.
In both flights, erroneous AoA data from the pilot side AoA sensor fouled airspeed and altitude measurements for the pilot side FCC which triggered an airspeed disagree and altitude disagree with the correct First Officer FCC.
My question is how is AoA data used to calculate altitude and airspeed, I’m an aerospace engineer and in school we are taught that conventionally, things like altitude and airspeed is measured with static pressure, stagnation pressure etc.
I can’t find any straight forward answers online other than folks on Quora taking a whole essay to say “well AoA data is used to calculate it in the ADIRU” which doesn’t explain anything.
Edit: I just remembered how AoA is used to correct pitot-static pressure and varying angles of attack because the tube isn’t head on into the incoming flow but that still leaves the question of altitude? are they incrementally multiplying the velocity by time to get a displacement and taking the sin(pitch) to get altitude? that’s my guess.
In: Engineering
so, not an engineer, but my understanding is that a their will be dynamic pressure changes brought on by the planes motion, as the plane pushes though the air, so to properly eliminate those you need to know the planes angle of attack. to quote wiki:
>
in flight, the air pressure varies slightly at different positions around the aircraft’s exterior, so designers must select the static ports’ locations carefully. Wherever they are located, the air pressure that the ports observe will generally be affected by the aircraft’s instantaneous [angle of attack](https://en.wikipedia.org/wiki/Angle_of_attack).[^([12])](https://en.wikipedia.org/wiki/Static_pressure#cite_note-12) The difference between that observed pressure and the actual atmospheric pressure (at altitude) causes a small [position error](https://en.wikipedia.org/wiki/Position_error) in the instruments’ indicated altitude and airspeed
so, to properly account for that change, you need to know AoA
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