There is a line along the wing leading edge where the flow divides with some going over the top of the wing and some going underneath. That line is called the stagnation point. It is close to the nose of the airfoil at low angles of attack and moves downward as the angle is increased. The stall warning vane is located such that as the wing approaches the stall angle the stagnation point moves past the vane causing it to be blown the other way by the change in flow from below to above the wing. The warning must actuate not less than five nor more than ten knots above the stall speed.

The switch is positioned to the initial location during production and it is checked during production flight test. There is an adjustment available of about 3/8 inch.

For an aircraft like the Cessna 172 and Piper Cherokee, the stagnation point moves a sizable fraction of an inch. For wings the size of a typical R/C model the range would be almost micrometer size. Although the same principle applies, in practice it would require a level of precision that would be difficult to say the least.