tsgarp wrote: ↑Fri Apr 15, 2022 11:27 amVa is the speed above which full deflection of the controls
will result in the acceleration of the aircraft exceeding it's maximum designed load factor.
(Emphasis added)
Except that's not true.
Va, Vb, Vc, and Vd are the design speeds. The aircraft designer can choose them to be what he or she wants them to be - that's why they're called "design speeds". Having chosen that speed, there's no need to go back and adjust the controls to make your supposed but very precise condition that at that exact speed "full deflection of the controls
will result in the acceleration of the aircraft exceeding it's maximum designed load factor" come true.
If you look back to CAR 3, under which most GA planes in existence were certified, it says:
§ 3.184 Design air speeds. The design air speeds shall be chosen by the designer except that they shall not be less than the following values:
Your misunderstanding of what Va stems from your belief that Va represents a determined speed at which something
will happen - some limit
will be exceeded - determined either by prediction, or by testing. It isn't that. Various tests of the aircraft have to be done at Va, and some terrible possible consequences of using the control have to be delayed until at least Va, but the designer can nominate a Va to be whatever they want, subject to the limits in CAR3 or 14 CFR 25.335. They are then on the hook for building an aircraft strong enough.
It's the difference between "you can fly this fast, do *this*, and not exceed a limit" vs. "if you fly this fast, and do *this*, you will exceed a limit." - or equivalent to the latter, and equally incorrect, "this is as fast as you can fly and do *this* in safety".
Denker addresses different uses of Va in See How It Flies, 2.14.2 (
https://www.av8n.com/how/htm/aoa.html#s ... ring-speed)
Particularly:
Finally, we should note that there are two different concepts that, loosely speaking, are called maneuvering speeds.
The design maneuvering speed, which we can denote Va(d), is primarily of interest to aircraft designers, not pilots. The designer must choose a value for Va(d) and then build an aircraft strong enough to withstand certain stressful maneuvers at that speed. Higher values of Va(d) promote safety, by forcing the design to be stronger.
The maneuvering speed limitation, which we can denote Va(l), is of interest to pilots. It is an operating limitation. It appears on a placard in the cockpit. Lower values of Va(l) promote safety, by restricting certain operations to lower, less-stressful airspeeds.
To my mind, Va is the "design manoeuvring speed", and is defined in the regulations as something at the free choice of the designer, subject to the limits publisned. If you want to invent a limiting speed for pilots, call it something else.
DId you hear the one about the jurisprudence fetishist? He got off on a technicality.