Navigation
Navigation tests dead reckoning, the wind triangle, chart work and the practical use of GPS. The PPL exam expects you to convert true to magnetic and to calculate heading, groundspeed and fuel.
Direction and charts
True direction is measured from true north; magnetic from magnetic north. Variation east means magnetic is less than true; variation west means magnetic is greater. Deviation is the compass error; compass = magnetic − east deviation. Use the chart's variation and the aircraft's deviation card.
Wind triangle
Wind direction is given as the direction it comes from. Apply the wind vector to the true course to get heading and groundspeed. A crosswind requires a heading into wind; a headwind reduces groundspeed.
Time, fuel and GPS
Time = distance/groundspeed. Fuel = rate × time. GPS gives track and groundspeed, not heading; do not allow the GPS to replace a nav log.
Worked example
True course 090°, TAS 100 kt, wind 020°/20 kt. Crosswind component = 20 sin70° ≈ 18.8 kt; headwind = 20 cos70° ≈ 6.8 kt. Drift angle = arcsin(18.8/100) ≈ 10.8°, so heading 079°T. Groundspeed ≈ 100 cos10.8° − 6.8 ≈ 91 kt. With 8°W variation, magnetic heading = 079 + 8 = 087°M.
Traps
Adding variation instead of subtracting it, or vice versa; using IAS for TAS; forgetting to apply wind; quoting GPS track as heading; mixing nautical miles and statute miles.