Maneuvering speed

In aviation, maneuvering speed is the maximum speed where full, abrupt control movement in the pitch axis will result in an aerodynamic stall of the aircraft prior to exceeding the design load limit. It has been widely misunderstood that flight below maneuvering speed will provide total protection from structural failure. See American Airlines Flight 587. Due to this accident a CFR Final Rule was issued effective October 15, 2010 clarifying this misconception ^[1]. It is normally designated as V_A in flight manuals, but is not typically shown on most airspeed indicators. V_A is the calibrated design maneuvering airspeed.

In the context of air combat manoeuvring (ACM), the maneuvering speed is also known as corner speed or cornering speed.^[2]

With full elevator deflection at maneuvering speed, an aerodynamic stall will occur, reducing or eliminating lift forces before damage can occur to the aircraft. To increase lift of a given wing, the angle of attack, air density, or the airspeed must be increased. The wing of an aircraft stalls at a specific angle of attack, regardless of airspeed. However, the higher the airspeed, the more lift the wing is capable of producing, and at a certain airspeed it is capable of producing more lift than it can support structurally. The declared maneuvering speed is based on the aircraft's maximum gross weight. At lower weights, maneuvering speed is always lower.

Hypothetically, if an aircraft were flying at a weight equal to its maximum structural load, it would be flying at both stall speed for that weight and maneuvering speed, with no excess angle of attack and lift available to accelerate the aircraft upward. At lower weights, and the same air speed and air density, the aircraft would be flying at a lower angle of attack, well below of stalling condition, and therefore with an excess lift available which could not be structurally supported. Therefore, as gross weight is decreased, maneuvering speed also decreases.

The maneuvering speed decreases as the aircraft's weight decreases from maximum takeoff weight because the effects of the aerodynamic forces become more pronounced as its weight decreases. The flight manuals for some aircraft (such as the Piper Cherokee) specify the design maneuvering speeds for weights below the maximum takeoff weight but sometimes it is left to the pilot to calculate. Using a "Rule of Thumb", the reduction in V_A will be half the percentage reduction in aircraft weight. For example if, with only one person on board, weight is 16% below maximum takeoff weight, then V_A is reduced by 8%.^{[3][citation needed]}

The maneuvering speed depicted on a cockpit placard is calculated for the maximum weight of the airplane, but V_A for other weights may be found in some POHs. The formulas used to calculate V_A for a lower weight is $\scriptstyle V_A \sqrt{W_2 \over W_1}$, where V_A maneuvering speed (at maximum weight), W₂ = actual airplane weight, W₁ = maximum weight.^[4]

See also

• V speeds
• 14 C.F.R. 23.335 "Design airspeeds"

References

1. ^ [1] FAA CFR Final Rule
2. ^ CNATRA P-821 (Rev. 01-08) "Flight Training Instruction, Advanced Naval Flight Officer (T-45C)". Department of the Navy, 2008.
3. ^ "Module content". Recreational Aviation Australia Incorporated. http://www.auf.asn.au/groundschool/umodule2.html. Retrieved 2009–09–03. ^{[dead link]}
4. ^ Jeppesen Instrument/Commercial Manual. 2000. ISBN 0-88487-274-2. 

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