Question

1. The expression for the lift coefficient, , is only valid for angles of attack below 5 degrees.

2. The Prandtl-Glauert correction is only valid for M < 0.8

Select the answer that matches:

Only statement 1 is true

Only statement 2 is true

Both statement 1 and statement 2 are true

Neither statement 1 nor statement 2 is true

Answer 1

Both statement 1 and statement 2 are true.

1. The expression for the lift coefficient being valid for angles of attack below 5 degrees is a common assumption in aerodynamics, as linear aerodynamics (e.g., the lift equation derived from the linear theory) typically holds true only at small angles of attack.

2. The Prandtl-Glauert correction is indeed applicable for compressible flow at subsonic speeds and is generally valid for Mach numbers (M) less than 0.8. Beyond this point, the assumptions made in the derivation of the correction begin to break down, and more sophisticated methods become necessary.

Thus, the correct answer is: **Both statement 1 and statement 2 are true.**