
Originally Posted by
Gordon Misch
Pete - At high AOA there is a pressure gradient below the wing, with pressure decreasing downward from the wing's lower surface. I demonstrated this by tufting my jury struts. The tufts tend downward, to below the flight path angle.
Given that the static source is closer to the wing than pitot source, as with the stock Piper arrangement, then the static component of total pressure is unequal between the two, and the reduced difference in total pressure between pitot and static source displays as artificially low airspeed. This is at least part of the too-low airspeed reading at high AOA, at least on my plane with the stock pitot-static configuration.
The reading I've done suggests that pitot angle is not a significant influence on dynamic pressure for "small" angles. If I recall correctly, "small" in this context might be something on the order of 20 deg or so.
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