Originally Posted by
Pilot DAR
The yellow arc on some airspeed indicators is not necessarily related to Va. Va will generally be slower than the bottom of the yellow arc. Va is the maximum speed at which the pilot could overstress the plane with large pitch control inputs. Slower than that speed, a large control input would result in a stall, which would automatically unload the stress on the wings. .
Mmmm....
Va is a design speed, it does not vary with weight. The only time Va has any relationship to stalling in FAR 23 is if Va is chosen to be Va min.
I am aware of many aircraft manuals giving Va for weight. FAR 23 is clear, Va is determined at the design weight. These operating manual "Va's" are really more like VO, but I have no idea how they have been determined.
Below is a cut and paste of AC 23-19A which is very clear in the lack of relationship between Va, stall and structural strength - except in one particular circumstance, that if the designer decides to us Va=Va min
"48. What is the design maneuvering speed VA?
a. The design maneuvering speed is a value chosen by the applicant. It may not
be less than Vs√ n and need not be greater than Vc, but it could be greater if the applicant chose the higher value. The loads resulting from full control surface deflections at VA are used to design the empennage and ailerons in part 23, §§ 23.423, 23.441, and 23.455.
b. VA should not be interpreted as a speed that would permit the pilot
unrestricted flight-control movement without exceeding airplane structural limits, nor
should it be interpreted as a gust penetration speed. Only if VA = Vs √n will the airplane
stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where
VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would
exceed the limit load factor.
c. Amendment 23-45 added the operating maneuvering speed, VO, in § 23.1507.
VO is established not greater than VS√n, and it is a speed where the airplane will stall in a nose-up pitching maneuver before exceeding the airplane structural limits."