FAA Flight Instructor Airplane (FIA)Navigation and AirspaceHard
A pilot plans a leg with a true course of 060° and a true airspeed of 130 knots. The forecast wind is from 030° at 20 knots. Using the wind component relationship, what is the approximate groundspeed?
- A100 knots
- B113 knots
- C147 knots
- D130 knots
Show answer & explanationAnswer & explanation
Correct answer: B. 113 knots
The angle between the wind direction (030°) and course (060°) is 30°. Headwind component = 20 × cos(30°) = 20 × 0.866 ≈ 17 knots. Groundspeed = TAS − headwind component = 130 − 17 = 113 knots.
Why the other options are wrong
- A. This overestimates the headwind component beyond the calculated 17 knots.
- C. This incorrectly adds the headwind component instead of subtracting.
- D. This ignores the wind's headwind component entirely.
Headwind/Tailwind Component
The portion of wind acting along the aircraft's course, calculated as wind speed × cosine of the angle between wind direction and course.
- Angle measured between wind FROM direction and course
- Headwind reduces groundspeed, tailwind increases it
- Crosswind component uses sine of the same angle
Memory trick: 'Cosine for the push, Sine for the shove.'