Navigation
Navigation tests the pilot's ability to plan and follow a route using charts, magnetism, dead reckoning and radio navigation aids. The exam emphasises practical calculation and correct interpretation of heading, track, wind and compass errors.
Charts and magnetism
- Aeronautical charts show airspace, obstacles, navaids and reporting points; scale determines distance measurement.
- True heading is measured from true north; magnetic heading applies variation. Compass heading also applies deviation.
- Variation is the angle between true and magnetic north; deviation is the aircraft-specific compass error. East variation is subtracted when converting true to magnetic ('east is least').
- The wind triangle relates heading and TAS to wind, producing track and groundspeed.
Dead reckoning and navaids
- Dead reckoning uses time, speed and distance. A PLOG records heading, altitude, fuel and ETAs.
- VOR gives a radial from a station; NDB gives a bearing; GNSS gives position. Always cross-check the selected frequency, ident and sense.
- Time calculations use UTC; local time differences can cause errors in ETA and fuel planning.
Worked example
Heading 090, TAS 120 kt, wind 180/30. The wind is from the right, so the aircraft drifts left. Drift angle = arcsin(30/120) = about 14.5 degrees. To maintain track 090, steer 090 + 14.5 = 104.5 magnetic (assuming no variation/deviation in this simplified example). Groundspeed = 120 x cos(14.5) = about 116 kt. The wind is almost a pure crosswind, so there is little headwind or tailwind component.
Traps that cost marks
Do not add variation when you should subtract it. Do not confuse compass deviation with magnetic variation. Do not use TAS as groundspeed in a wind calculation. Check whether the wind is given as true or magnetic. A VOR radial is 'from' the station, not a bearing 'to' it. Chart scale errors can make a short leg look longer than it is.
Key points
- True heading applies variation; magnetic heading applies deviation to give compass heading.
- East variation is subtracted when converting true to magnetic; west variation is added.
- Wind triangle: heading/TAS plus wind gives track/groundspeed.
- Drift angle = arcsin(crosswind/TAS); groundspeed uses the along-track wind component.
- VOR radials are measured from the station; NDB bearings are relative to the station.
- Use UTC consistently and cross-check ETAs and fuel against the PLOG.