Originally Posted by
SlimLonggood
Flightpath,
An asymmetric aerofoil will produce lift at 0' AoA, you have to go to negative to produce 0 lift.
All airliners have asymmetric aerofoils.
Well, technically it really depends upon where you define zero - but in general terms you are right.
That said, I know from personal experience that many asymmetric aerofoiled aeroplanes (the C152 aerobat being an obvious example) are extremely reluctant to generate useful amounts of lift inverted - zero to negative AoA in other words. I would expect something similar from any airliner - invert it, it'll end up pitching (nose-up, world down...) into an inverted dive. Goodness only knows how much height you'd take to recover from that: a couple of tens of thousands of feet most likely.
G