have always thought of Va as the speed where if you applied full control deflection, the surface would stall before it could provide enough force to exceed the max load factor of the aircraft meaning you could safely use full deflection of controls below Va.

Not really, if you fully apply elevator, rudder or ailerons at Va, the horizontal surface, vertical surface and the ailerons must be able to carry the loads - stalling doesn't come into it. See FAR 23.423, 441, 445.
There is no FAR 23 standard which requires the wings to carry the loads generated by full elevator deflection, or flying to the stall at Va.
The exception, in a roundabout way, is when Va=Va min.
In fact FAR25 full elevator application at Va specifically states that "accelerations exceeding the maximum positive manoeuvre load factor need not be considered".

I don't know how the Va v's stall misunderstanding developed, but it goes back many years and was probably contributed to by:
1. Regulatory operations departments and airworthiness not communicating with each other;
2. The standard Vg diagram is really generic and only shows one of the many possible speeds for Va - that happens to be Va min, which of course, is the only stall related Va speed;
3. Operations people looking at the Vg diagram and not reading the written standard which shows Va can really be any speed above Va min;
4. Aircraft manufacturers published Va speeds scheduled against weight for some aircraft. Clearly, control surface stuctural strength doesn't reduced with weight.
But IF the published Va was Va min this approach actually provides some useful stall v's structural strength information. It may be that manufacturers airworthiness staff
didn't communicated wth the operations manual people at this level of detail; and
5. Perhaps many aircraft were designed to Va=Va min, but your example of the Citabria and Decathlon is interesting. Va was called Vp in CAR 3 (circa 1949) and was pretty much the same as the current Va

FAR 25 different wording, but is similar to FAR 23, I don't know what the latest FAA standards will require - it could just require the structure to be "safe" and leave the applicant to convince the authority.You need to know the basis of the selection of Va. Is it greater than Va min? Also one should consider the various ways you can get a G "overswing" beyond that you expected for the speed you are flying at.

Some of my thoughts, starting with the Citabria and Decathlon. According to my copy of the AFMs, the Citabria's Va is 120 mph and the Decathlon is 132 mph so I don't understand jonkster's comment?

At least the FAA is doing something about the disconnect between certification and operations with some education and rule changes https://www.aopa.org/news-and-media/...-understanding
Not retrospective but "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."

Good that the FAA has clarified "For airplanes where VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would exceed the limit load factor." The way that I dealt with it but many have dealt with it differently.

Some airplanes used the simplified loading criteria of the old Appendix A where Va(min) was calculated without regard to the actual stall speed by the equation Va min=15.0*sqrt(N1*W/S). Designers make up the flight envelope and design maneuvering speed prior to the prototype being flown and many do not revisit it after the real stall speed is known.

The odd manufacturer recognises that Va is determined simply from power off stall speed measured with slow deceleration and the cg at one end of the range but do a dynamic stall with max power and at the other end of the cg range then the dynamic stall is at a speed quite different than that Vs sqrt(g).

One airplane that I am familiar with has Vs of 52 KIAS (49 KCAS), design maneuver speed 134 kts IAS (133.5 KCAS) but then not surprisingly full back stick at 121 KIAS (120 KCAS) will produce 6 G, the limit load factor. (hopefully the numbers work, as I've done them very quickly) Pilots think that they can give it full back stick at 134 kts - 7.4 G - hmmm, no wonder we saw broken airplanes.

Meanwhile CASA's CAAP 155-1, Aerobatics, still has a dangerously incorrect and unhelpful description of Va and furthermore is generally irrelevant after Part 61.

Thanks Djpil, almost forgotten Appendix A.
The concern for me is that, in Australia, both CASA and ATSB, after many years, still promote this potentially dangerous misunderstanding.
ATSB investigators and CASA FOI's should know better.
Having said that, any seach for Va info on the web will produce mostly incorrect information.
While the FAA airworthiness standards people have been somewhat active to correct misunderstandings, I don't think this is the case for their GA operations people.
I think the AA flight 587 A300 fin separation gave the airlines and FAA airline operations people a reality check.
At least you can ensure your students get the message!
Cheers

Go ahead...Make my day.....

Having worked at the company during the incident, I want to make it very clear that the CP of the time always welcomed and supported pilots making safe decisions to postpone flights.
However, the comments from the owner on the same matter are a straight up lie and frankly disgusting.

That must be a new policy. When I was there I never experienced, or heard anyone else describe what you are implying.