Navigation
This domain covers chart work, direction, the wind triangle, dead reckoning, the 1-in-60 rule and flight-planning calculations. The exam rewards method: draw the vectors, label true and magnetic, and check units.
Direction and charts
- True north, magnetic north and compass north differ by variation and deviation. Variation east, magnetic least; variation west, magnetic best.
- A great circle is the shortest route; a rhumb line is a constant track.
- Positions use latitude and longitude; 1 minute of latitude ≈ 1 NM.
The wind triangle
- Heading plus wind gives track and groundspeed. Apply wind to true heading, then convert to magnetic and compass.
- Crosswind component = wind speed × sin(angle); head or tailwind = wind speed × cos(angle).
- 1-in-60: a 1° error gives 1 NM off track after 60 NM.
Worked example
TAS 100 kt, required track 000°, wind 270°/20 kt. The wind is a direct crosswind. Drift = arcsin(20/100) ≈ 11.5°, so steer 349° true to make good 000°. Groundspeed = √(100² − 20²) ≈ 98 kt. If variation is 10°E, the magnetic heading is 339°.
Traps
- Applying wind to the heading rather than the track.
- Adding easterly variation when converting true to magnetic; it should be subtracted.
- Using IAS for navigation instead of TAS.
- Forgetting that deviation is aircraft-specific and comes from the compass swing.
- Mixing nautical miles, statute miles and kilometres.