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My understanding of flight is that the primary aspect is the angle of deflection, and the purposes of the shape of the wing is to maximise efficiency. Could a commercial airliner with asymmetric aerofoil sustain inverted flight by keeping its nose up, or something similar?

For the purposes of the question, ignore issues with the fuel or engine, and assume that the wing shape is fixed and not specifically built to accommodate inverted flight, including not having flaps or anything in the aileron department.

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Yes, based purely on the wing shape an airliner could fly upside down and maintain a straight inverted flight. The lift of the wing is a function of the vertical angle of the airflow, the angle of attack.

from aImage source

The picture shows an airfoil pointed upwards, but the same forces apply when the wing nose point downwards. Then turn the picture upside down, and you have lift pointing upwards again.

The situation is valid for an asymmetric airfoil as well, the only difference being that it provides lift at AoA zero. Zero lift is provided at a slight negative angle of attack, so the aircraft nose will be further up when inverted, still below the stall angle though.

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  • $\begingroup$ Thanks. Can you please link me to a paper that talks about this? I am not believed. $\endgroup$ – Piomicron Nov 29 '17 at 15:01
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The only case I could find of an airliner flying inverted for any period of time was Alaska Air 261. The jackscrew that set the incidence on the horizontal stabilizer stripped out due to shoddy maintenance, putting the stabilizer in a severe nose down position that elevator and trim input couldn't correct. For a minute or two, the pilots did manage to hold the plane inverted in an attempt to counteract the broken stabilizer, but the plane ended up crashing into the sea due to the inability of the pilots to regain full control.

So the answer would be a qualified 'maybe', as it is unknown how much of a contributing factor the inverted flight was to the final descent.

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