Originally Posted by
Singlecoil
At Va, the aircraft will stall before the positive limit load factor is exceeded. The negative limit load factor can still be exceeded at Va.
The old, "you can push or pull on any control surface and not hurt anything" is totally wrong though you do hear it a lot.
This graph says it all:
It is not required for Va to stall and aircraft when design limit loads are exceeded, nor is it the case for all aircraft.
Some designers make it so that Va is at maneuvering speed - but the thing no one gets is that Va does
not have to equal operating maneuvering speed (Vo)
Vo (operating maneuvering speed) is the speed that an aircraft will stall, etc before the design loads are imposed
Va (design maneuvering speed) does
not have to have anything to do with
stalling - it's part of a
certification process which all speeds are based off. It basically just makes sure the control surfaces stay attached to the aircraft.
Here is the FAA Part 23 (a bit more than I last posted) to clear up the confusion:
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.