Overview
The design maneuvering speed (VA) is a structural design airspeed used in determining the strength requirements for the airplane and its control surfaces. At or below VA, the wings are unable to produce enough lift to exceed their design structural load limits. While the aviation community has learned a significant amount about VA since the crash of American 587, there is a significant amount about VA that is still unknown.
Commentary
As angle of attack increases at a constant airspeed, the load factor must increase. For a constant load factor, however, a higher airspeed results in a lower angle of attack since additional lift is being created by the airspeed instead of angle of attack. While flying at airspeeds at or below VA, the angle of attack of the wings required to sustain level, unaccelerated flight is higher than required for flight above VA — the effect is that at a slower airspeed with a constant load factor, the wing is closer to the critical angle of attack than at a faster airspeed. Therefore, when the aircraft is below VA, a wing increasing in angle of attack will reach its critical angle of attack prior to reaching its limit load factor – this means that below VA, a wing will stall before it is able to generate the lift required to exceed its limit.