Compared to an unswept wing, a swept wing generally exhibits what lift characteristic at high speeds?

• A. Lower lift coefficient at subsonic and supersonic speeds
• B. Higher lift coefficient at subsonic speeds
• C. Higher lift coefficient at supersonic speeds
• D. Same lift coefficient at all speeds

Answer: (A)

Sweeping a wing back changes how the air flow interacts with the wing, reducing the effectiveness of lift for a given speed and angle of attack. The back-swept geometry makes the flow see a smaller component of the flow normal to the wing’s lifting surface, which lowers the lift-curve slope and the lift produced at a given AoA. This effect is present in both subsonic and supersonic regimes: the wing is less efficient at generating lift per degree of angle of attack than an unswept wing, so the lift coefficient is generally lower across these high-speed ranges. The design trade-off, though, is that sweep raises the speed at which drag from shock waves becomes significant (the critical Mach number), which is why swept wings are favored for high-speed flight overall.