A crosswind component of 12 knots at Mach 0.6 results in a drift angle of how many degrees?

A crosswind component of 12 knots at Mach 0.6 results in a drift angle of how many degrees?

• A. 1 degree
• B. 2 degrees
• C. 3 degrees
• D. 4 degrees

Answer: (B)

The drift angle is the small angle between where the airplane is pointing and where it actually travels because of a crosswind. It comes from the relationship tan(drift) = crosswind component / true airspeed. For small angles, drift in radians is approximately crosswind / TAS. First estimate TAS from Mach 0.6: using a standard speed of sound near 661 knots, TAS ≈ 0.6 × 661 ≈ 397 knots. With a crosswind of 12 knots, tan(drift) ≈ 12 / 397 ≈ 0.0302. The angle in radians is about 0.0302, which converts to degrees as 0.0302 × (180/π) ≈ 1.7 degrees, i.e., about 2 degrees. So the drift angle is roughly 2 degrees.

The drift angle is the small angle between where the airplane is pointing and where it actually travels because of a crosswind. It comes from the relationship tan(drift) = crosswind component / true airspeed. For small angles, drift in radians is approximately crosswind / TAS.

First estimate TAS from Mach 0.6: using a standard speed of sound near 661 knots, TAS ≈ 0.6 × 661 ≈ 397 knots. With a crosswind of 12 knots, tan(drift) ≈ 12 / 397 ≈ 0.0302. The angle in radians is about 0.0302, which converts to degrees as 0.0302 × (180/π) ≈ 1.7 degrees, i.e., about 2 degrees.

So the drift angle is roughly 2 degrees.