FAA Sport Pilot Airplane (SPA)Airspace and NavigationHard
A pilot plans a true course of 090° with a true airspeed of 100 knots. Winds aloft are forecast from 360° at 30 knots. Using the wind correction angle formula WCA = arcsin[(wind speed × sin(wind angle))/TAS], what true heading should the pilot fly to maintain the course?
- A107°
- B117°
- C090°
- D073°
Show answer & explanationAnswer & explanation
Correct answer: D. 073°
The wind angle relative to course is 360°−90°=270° (a direct crosswind from the left). WCA = arcsin(30×sin270°/100) = arcsin(0.30) ≈ 17°. Since the wind is from the left of course, the pilot must crab left (subtract WCA), giving a true heading of 090°−17°=073°.
Why the other options are wrong
- A. This incorrectly adds the WCA instead of subtracting it for a left crosswind.
- B. This adds an incorrect larger WCA in the wrong direction.
- C. This ignores the wind correction angle entirely.
Wind Correction Angle (WCA) & True Heading
The angle applied to a true course to correct for wind drift, calculated using the wind triangle, then applied left or right of course depending on wind direction.
- WCA = arcsin[(wind speed × sin(wind angle))/TAS]
- Wind from the left of course requires heading correction to the left (subtract)
- Wind from the right of course requires heading correction to the right (add)
Memory trick: Crab into the wind — nose points toward where the wind is coming from.