Definition of Va (maneuvering speed) and Vno
January 15th, 2008 | 
Author: Thought I would post a recent thread from our forum:
Here was the question that was asked:
Could you please give me a detailed explanation of maximum structural cruising speed. I’m confused as to why it is higher than manuevering speed and doesn’t change with weight like Va does if they both are turbulent air penetration speeds?
Thanks for your help.
And here was the answer:
Hi! Great Question! I actually had to do some “research” for this one!
Va. Known as maneuvering speed. This has to do with the MAX speed at which you can safely stall an airplane. During certification, this has to do with forces measured on the elevator (see image below). Any speed above Va you would exceed structual limits before reaching a stall (not good)
Vno. Maximum structual cruising speed. This has to do with wind gusts measured on the wings. I have to do a little more research but my source told me below the yellow arc it is 20 in. per second gusts and in the yellow arc it is 15 in per second gusts. This has to do with the wings bending and twisting. Not structural limits on the elevator.
Some instructors teach students that Va is turbulent penetration speed which is really not completely accurate and may confuse things. It also may have to do with the fact that Va wasn’t a required certification until the 50’s or 60’s.
Hopefully this helps some.
Instructor.
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I had also done some research years ago as I could not get a good answer either. From a US Navy flight training manual I got that Va is the speed at which the aircraft would exceed its upper load limit before stalling. My interest was also what was the actual Va during flight, its not really what is in the manual. From a aircraft aerobatics manual I got a formula. Square root of the upper load limit times the stall speed. Try it out, I did. First you need to determine your actual stall speed at your given flight condition and you’ll have to fly to do this. This makes more sense than the old “any full deflection of the control …” and you can see why Va is not on the ASI as well.
The term Va is widely misunderstood in the aircraft operation community. The only time Va is related to stall speed is if an aircraft designer selects Va (minimum) for his design. He is permitted to select any speed for Va. providing it is above Va (min).
Also Va is only concerned with the design of the rudder/fin, elevator/stab, ailerons and their attachments.
AC 23-19A states:
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 Vsv 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 vn will the airplane
stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where
VA>VSvn, 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 VSvn, and it is a speed where the airplane will stall in a
nose-up pitching maneuver before exceeding the airplane structural limits.