Navigation
Navigation combines general navigation-charts, magnetism and the wind triangle-with radio navigation aids and their in-flight use.
General navigation
- Chart projections: Mercator gives constant course with distorted scale; Lambert conformal conic approximates straight great circles; polar stereographic is used near the poles.
- Magnetism: variation is between true and magnetic north; deviation is aircraft magnetism. Convert true to magnetic to compass.
- Wind triangle: track, heading, drift and groundspeed. Drift is the angle between heading and track.
Radio navigation
- VOR: the radial is magnetic from the station; the CDI centres with TO/FROM. Intercept at 30–45°.
- NDB/ADF: relative bearing; distinguish homing from tracking.
- DME: slant range; at high altitude it reads greater than ground distance.
- ILS: localizer 90/150 Hz and glideslope typically 3°; decision altitude or height.
- GNSS: RAIM, RNP and integrity; check notams.
Worked example
Track 090°T, TAS 120 kt, wind 180°/30 kt. The wind is a pure crosswind from the right. Drift = arcsin(30/120) ≈ 14°. Heading = 090° - 14° = 076°T into wind. Groundspeed = √(120² - 30²) ≈ 116 kt. Apply variation and deviation to obtain compass heading.
Traps
- Setting heading equal to track in a crosswind.
- Reading a VOR radial as a bearing to the station.
- Ignoring DME slant range at close range or high altitude.