An airplane's maximum structural maneuvering speed (Va) is 108 KIAS at its maximum gross weight of 2,700 lb. The airplane is now being flown at a reduced weight of 2,200 lb after fuel burn. What is the approximate reduced Va, and why does this matter for turbulence penetration?
- A84 KIAS, because Va decreases in direct proportion to the percentage weight decrease
- B108 KIAS, because Va is a fixed structural limit that does not change with aircraft weight
- C118 KIAS, because a lighter airplane can safely fly faster in turbulence without risk of exceeding structural limits
- D97 KIAS, because Va decreases with weight and using the higher gross-weight Va at this lighter weight increases the risk of exceeding load limits before the wing stalls
Show answer & explanationAnswer & explanation
Correct answer: D. 97 KIAS, because Va decreases with weight and using the higher gross-weight Va at this lighter weight increases the risk of exceeding load limits before the wing stalls
Va varies with the square root of the weight ratio: 108 × √(2,200/2,700) = 108 × √0.815 = 108 × 0.903 ≈ 97 KIAS. At lower weights, the wing stalls before generating enough lift to exceed load limits, but this protection is only valid at the reduced Va; flying at the higher gross-weight Va risks structural damage in turbulence at the lighter weight.
Why the other options are wrong
- A. Va varies with the square root of the weight ratio, not directly proportional to weight change.
- B. Va is not fixed; it varies with weight, only the aerodynamic and structural limits are fixed.
- C. Incorrectly increases Va, which is the opposite of the correct relationship.
Maneuvering Speed (Va) vs Weight
Va is the maximum speed at which full, abrupt control deflection can be applied without exceeding structural load limits; it decreases with the square root of decreasing weight.
- New Va = old Va × √(new weight ÷ old weight)
- At lower weights, the wing stalls at a lower speed before load limits are exceeded, so Va decreases
- Flying at the gross-weight Va when lighter can allow speeds that exceed structural limits before stalling
Memory trick: Lighter plane, lower Va — don't fly turbulence at the heavy-weight number.