Navigation (General Navigation, Radio Navigation)
Navigation covers the route from planned track to actual position: charts, coordinates, track and heading, wind triangle, variation and deviation, plus VOR, NDB, DME, GNSS and transponder use.
General navigation
- True track is measured from true north; magnetic track uses magnetic north; compass heading includes deviation.
- Wind correction angle (WCA) converts track to heading: heading = track ± WCA. Then apply variation and deviation to obtain compass heading.
- Variation east is subtracted from true to obtain magnetic; deviation depends on the aircraft compass card.
- Use the chart scale and current wind; do not mix units or chart datums.
Radio navigation
- VOR gives bearing from the station; the CDI centres when the selected radial matches. TO/FROM indicates direction relative to the station.
- NDB/ADF gives relative bearing; station passage and drift correction require interpretation.
- DME gives slant range, not ground distance; error increases at high altitude and close range.
- GNSS provides position, track and groundspeed; RAIM and database currency matter.
- Transponder codes: 7700 emergency, 7600 radio failure, 7500 unlawful interference.
Worked example
True course 090°, variation 5°E, deviation +2°, wind correction −10°. True heading = 090 − 10 = 080°. Magnetic heading = 080 − 5 = 075°. Compass heading = 075 − 2 = 073°. If the result is negative, add 360°.
Traps that cost marks
- Applying variation in the wrong direction.
- Mixing true track with magnetic heading.
- Treating DME as horizontal distance.
- Forgetting to update the GNSS database and check RAIM.