In steady, unaccelerated flight, for a given angle of attack, the necessary lift is achieved at what airspeed?

In steady, unaccelerated flight, for a given angle of attack, the necessary lift is achieved at what airspeed?

• A. The airspeed must equal the corresponding indicated airspeed for that angle of attack.
• B. The airspeed is independent of angle of attack.
• C. Any airspeed can generate sufficient lift for any angle of attack.
• D. Lift is independent of angle of attack.

Answer: (A)

In steady, unaccelerated flight, lift must balance weight. For a given angle of attack, the wing produces a specific lift coefficient. To support the weight with that fixed coefficient, the dynamic pressure must reach a particular value, q = W / (S Cl). Dynamic pressure depends on airspeed, so there’s a unique airspeed that provides the needed lift. The indicated airspeed is the measure of that dynamic pressure in standard atmosphere, so the required airspeed is precisely the corresponding indicated airspeed for that angle of attack. That’s why this option is correct: the airspeed must equal the indicated airspeed corresponding to that angle of attack. The other statements aren’t accurate because lift depends on angle of attack, air density, and speed; you can’t have any airspeed for any angle of attack, and lift is not independent of angle of attack.

In steady, unaccelerated flight, lift must balance weight. For a given angle of attack, the wing produces a specific lift coefficient. To support the weight with that fixed coefficient, the dynamic pressure must reach a particular value, q = W / (S Cl). Dynamic pressure depends on airspeed, so there’s a unique airspeed that provides the needed lift. The indicated airspeed is the measure of that dynamic pressure in standard atmosphere, so the required airspeed is precisely the corresponding indicated airspeed for that angle of attack.

That’s why this option is correct: the airspeed must equal the indicated airspeed corresponding to that angle of attack. The other statements aren’t accurate because lift depends on angle of attack, air density, and speed; you can’t have any airspeed for any angle of attack, and lift is not independent of angle of attack.