My error, I see now what you're getting at. It didn't hit me even though I wrote
VA must be equal to or greater than VS√n
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 V
A are used to design the empennage and ailerons in part 23, §§ 23.423, 23.441, and 23.455.
V
A 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 V
A= Vs√n will the airplane stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where V
A>V
S√n, the pilot would have to check the maneuver; otherwise the airplane would exceed the limit load factor.
Amendment 23-45 added the operating maneuvering speed, V
O, in § 23.1507. V
O is established not greater than V
S√n, and it is a speed where the airplane will stall in a nose-up pitching maneuver before exceeding the airplane structural limits.
But I think confusion may remain. As a result of the American Flt 587 the FAA put out a "Maneuvering Speed Limitation Statement" addressing a FAR 25 amendment.
The NTSB’s investigation revealed that many pilots might have a general misunderstanding of what the design maneuvering speed (VA) is and the extent of structural protection that exists when an airplane is operated at speeds below its VA. VA is a structural design airspeed used in determining the strength requirements for the airplane and its control surfaces. The structural design requirements do not cover multiple control inputs in one axis or control inputs in more than one axis at a time at any speed, even below VA.
The NTSB found that many pilots of transport category airplanes mistakenly believe that, as long as the airplane’s speed is below VA, they can make any control input they desire without risking structural damage to the airplane. As a result, the NTSB recommended that the FAA amend all relevant regulatory and advisory materials to clarify that operating at or below maneuvering speed does not provide structural protection against multiple full control inputs in one axis or full control inputs in more than one axis at the same time.
This final rule adopts the proposed rule with minor changes that will resolve a longstanding inconsistency in the current requirements that would have been left in place by the proposed rule. This inconsistency, which goes back to at least the 1953 Civil Air Regulations Part 4b, concerns the reference to ‘‘maneuvering speed VA’’ in the existing § 25.1583(a)(3). Sections 1.2 and 25.335(c) define ‘‘VA’’ as the ‘‘design maneuvering speed,’’ not the ‘‘maneuvering speed.’’ Section 25.1507 defines the ‘‘maneuvering speed’’ as an operating limitation that must not exceed the design maneuvering speed, VA. Since the ‘‘maneuvering speed’’ can be less than VA, the reference to ‘‘maneuvering speed VA’’ in the existing § 25.1583(a)(3) is incorrect.
An applicant may wish to establish a maneuvering speed different from the design maneuvering speed, in order to make it easier for pilots to use. For example, the design maneuvering speed, VA, is an equivalent airspeed. Applicants might find it desirable to provide a maneuvering speed as a calibrated airspeed equal to or below the corresponding equivalent design maneuvering airspeed at all altitudes, in order to provide the information in a format that is consistent with that used on the flight deck airspeed indicator. In practice, the maneuvering speed has been identified as VA in AFMs even when it is not always exactly the same as the design maneuvering speed defined in § 25.335(c). We have no evidence of this being unsafe and see no reason to prohibit it in the future. However, in order to address the inconsistency in the regulations, for § 25.1583(a)(3), we have changed the reference to ‘‘the maneuvering speed VA’’ proposed in the NPRM to ‘‘the maneuvering speed established under § 25.1507’’ in this final rule. For new § 25.1583(a)(3)(i) and (ii), we have also changed the references to ‘‘VA’’ proposed in the NPRM to ‘‘maneuvering speed’’ in this final rule. We will continue to allow applicants to refer to this maneuvering speed as VA in AFMs.
For small airplanes, part 23 defines an operating maneuver speed (VO) to serve the same purpose as the maneuvering speed established under § 25.1507. The part 23 approach has one advantage in that there is a unique V-speed abbreviation for pilots to use that differentiates the maneuvering speed used operationally from the design maneuvering speed used to show compliance with the structural type certification requirements. We chose not to introduce a new V-speed term in part 25 because the VA term has historically been used for transport category airplanes for both the speed to be used operationally and for design purposes. Using a new V-speed term could also potentially lead to confusion if different speed terms and definitions are used for new airplane designs compared to current designs.
You go on to explain Vo and how it's related to the entire airframe (by ensuring that the limit maneuvering load factor isn't exceeded), but Va does not do that.
Seems to me that we have to be very specific as to what we're referring to now when mentioning "maneuvering speed". Is it FAR 23 (old), FAR 23 (new), FAR 25, or "corner speed" as referred to by fighter types.
And a question. Why would you have a V
A (or whatever you want call it) where you have to check the control input to avoid exceeding "g" limit? All the old flight manuals that I have define V
A as (direct quote out of a Cessna manual) "maximum speed at which full or abrupt control movements may be used" and lists the weight/speeds,
3800 lbs 130 kts
3050 lbs 117 kts
2300 lbs 101 kts
They are also the maximum recommended turbulence penetration speeds.
Piper manual quotes, "V
A - Maneuvering speed is the maximum speed at which application of full available aerodynamic control will not overstress the airplane".
Convention wisdom has always been to reduce V
A proportionally with reduced weight. Is anyone aware of an aircraft certified where V
A>V
S√n?