When airspeed is low, the angle of attack must be relatively high to maintain balance between lift and weight.

When airspeed is low, the angle of attack must be relatively high to maintain balance between lift and weight.

• A. True
• B. False
• C. Not enough information
• D. Depends on altitude

Answer: (A)

Lift depends on both the speed of the air and how the wing’s angle of attack affects the lift coefficient. The lift equation shows that lift rises with dynamic pressure (which falls as speed drops) and with CL, which increases as you raise the angle of attack up to the stall limit. So when you slow down but still need the same lift to balance weight in level flight, you must increase CL. The way to do that in steady flight is to pitch up, which raises the angle of attack. This keeps lift roughly equal to weight until you get close to stall, at which point further increasing angle of attack no longer increases lift and can cause a loss of lift. Because of this relationship, the statement is true in normal operating conditions. Density changes with altitude, so the exact angle isn’t fixed, but the trend—lower speed requiring a higher angle of attack to maintain lift—is consistent.

Lift depends on both the speed of the air and how the wing’s angle of attack affects the lift coefficient. The lift equation shows that lift rises with dynamic pressure (which falls as speed drops) and with CL, which increases as you raise the angle of attack up to the stall limit. So when you slow down but still need the same lift to balance weight in level flight, you must increase CL. The way to do that in steady flight is to pitch up, which raises the angle of attack. This keeps lift roughly equal to weight until you get close to stall, at which point further increasing angle of attack no longer increases lift and can cause a loss of lift. Because of this relationship, the statement is true in normal operating conditions. Density changes with altitude, so the exact angle isn’t fixed, but the trend—lower speed requiring a higher angle of attack to maintain lift—is consistent.