"Icebound" wrote

Well, the 172's horn seems to be basically the same principle as
blowing across the mouth of an open beer bottle.

Not all C-172s...some have the electric vane. The one that I fly does.

I don't know how other stall horns were designed, but it was my
impression that a stall horn is supposed to be designed to go off a
little before the true stall.

(c) During the stall tests required by §23.201(b) and §23.203(a)(1), the
stall warning must begin at a speed exceeding the stalling speed by a
margin of not less than 5 knots and must continue until the stall occurs.


...does that mean that for most other aircraft, I would have to be
aware that the stall horn will go off suddenly and completely?

Yes, but at least 5 knots above the actual stall per Part 23.

Bob Moore
ATP CFI