Navigation
Navigation
Navigation questions test the relationship between track, heading, wind and navigation specification. The exam expects calculation and chart interpretation, not memorising every avionics page.
Core rules
- True track is measured from true north; magnetic heading is true heading corrected for magnetic variation. Variation east is subtracted when converting true to magnetic; west is added.
- Wind correction angle opposes drift. Heading = track plus or minus wind correction.
- Groundspeed is the along-track component of TAS and wind; crosswind reduces groundspeed.
- RNAV allows operation on any desired path within coverage; RNP adds on-board performance monitoring and alerting.
- GNSS is not infallible: RAIM, interference and NOTAMed outages matter.
Worked example
An aircraft must track 090°T at TAS 300 kt. Wind is 360°/30 kt. The wind is from the north, so it pushes the aircraft south of track. Crosswind component is 30 kt; wind correction angle = arcsin(30/300) ≈ 6°. To stay on track the aircraft must point 6° left, heading 084°T. Groundspeed ≈ √(300²−30²) ≈ 299 kt. With 5°W variation, magnetic heading = 084 + 5 = 089°M. The controller should expect a slower groundspeed than TAS and a left crab.
Traps
Do not add variation in the wrong direction. Do not use groundspeed as TAS. Do not assume RNAV equals RNP; RNP requires performance monitoring. Do not treat a GNSS outage as impossible; have a conventional navigation fallback.