The lift surfaces must be flown faster or at higher AOA at higher altitudes to produce the same amount of lift. True or False?

The lift surfaces must be flown faster or at higher AOA at higher altitudes to produce the same amount of lift. True or False?

• A. True
• B. False
• C. Not applicable
• D. It depends

Answer: (A)

Lift comes from air pushing over the wing, and it grows with air density, speed, and the wing’s lift coefficient (which increases with angle of attack up to stall). At higher altitudes the air is thinner, so for the same wing area and angle of attack you get less lift. To keep producing the same lift, you must increase dynamic pressure, which means flying faster, or increasing the angle of attack to raise the lift coefficient (up to the stall limit). In practice, both methods are used, but increasing speed also increases drag and increasing angle of attack brings you closer to stall. Therefore, this statement is true.

Lift comes from air pushing over the wing, and it grows with air density, speed, and the wing’s lift coefficient (which increases with angle of attack up to stall). At higher altitudes the air is thinner, so for the same wing area and angle of attack you get less lift. To keep producing the same lift, you must increase dynamic pressure, which means flying faster, or increasing the angle of attack to raise the lift coefficient (up to the stall limit). In practice, both methods are used, but increasing speed also increases drag and increasing angle of attack brings you closer to stall. Therefore, this statement is true.