Originally Posted by
zzuf
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;
....
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
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.