NACA stall-warning indicator

Thopmson, F L
October 1938

The stall-warning indicator employs a total-head tube located close to the wing surface in a region wherein local stalling occurs before the main portion of the wing stalls. The artificial production of a localized stalled region is accomplished by means of a sharp leading edge extending a few inches along the span. An abrupt drop in the total pressure relative to a static reference taken at some convenient point occurs at the stall in this region. Thin drop in total pressure caused the contraction of a pressure cell to which the total-head tube and the static orifice are connected and closed an electrical circuit that actuates a warning signal.

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