Navigation
What the exam tests
Navigation covers dead reckoning, the wind triangle, magnetic variation and deviation, charts, time, fuel, and the use of GNSS and ground-based aids for VFR and IFR flight.
Core rules
- True heading ± variation = magnetic heading; magnetic heading ± deviation = compass heading. 'Variation east, magnetic least': subtract easterly variation from true.
- The wind triangle relates true airspeed, wind velocity, and ground speed. Crosswind component = wind speed × sin(wind angle); headwind component = wind speed × cos(wind angle).
- Drift angle ≈ arcsin(crosswind ÷ TAS) for small angles. Heading must be turned into wind to maintain track.
- 1 minute of latitude = 1 nautical mile. 1 degree of longitude = 60 NM × cos(latitude).
- GNSS gives position, track, and ground speed, but the pilot must still monitor raw data and NOTAMs for RAIM or jamming.
Worked example
TAS 100 kt, track 090°T, wind 020°/20 kt. The wind angle to the track is 70°. Crosswind = 20 × sin 70° ≈ 18.8 kt; headwind = 20 × cos 70° ≈ 6.8 kt. Drift ≈ arcsin(18.8 ÷ 100) ≈ 10.8°. The wind is from the left, so turn left: heading ≈ 079°T. Ground speed ≈ 100 × cos 10.8° − 6.8 ≈ 91 kt.
Traps
Do not apply variation to magnetic headings the wrong way. Do not use TAS as ground speed in wind. Do not ignore compass deviation after maintenance or in a new aircraft.