Symmetrical airfoils will not generate lift if the angle of attack is
zero. The F104 has a symmetrical airfoil and cruises at about 3 degrees
positive AOA. Similarly, constant altitude inverted flight is possible
only if the airfoil has a positive angle of attack relative to the
earth. Lots of forward stick, in other words. In knife flight, the
fuselage is yawed so it has a positive angle of attack and is
generating lift and it is usually symmetrical, too. The slab-sided F4
flew fine on its side at 500 KIAS. As for the 'true' explanation of
lift, any time you have to juggle four simultaneous differential
equations, pilot instruction becomes very unwieldy and the students
doze off. This approach, to me, is picking nits.
Walt BJ.
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