The triangle of velocities
True heading plus wind gives track and groundspeed. Add variation to get magnetic and deviation to get compass — east is least, west is best when going from true to magnetic. A useful mental rule: drift in degrees is roughly the crosswind component divided by the true airspeed in miles per minute.
Chart craft
A 1:500,000 chart is the standard VFR chart in much of the world: 1 cm equals 5 km. Mark planned tracks, safety altitudes and 10-degree drift lines, and select landmarks that are unique, large and ahead of the aircraft rather than beside it.
Radio aids
A VOR gives bearing information along radials and is line of sight; an NDB with an ADF is subject to night effect, coastal refraction and thunderstorm error. DME measures slant range, so directly overhead a station at 6,000 ft it reads about one nautical mile even when you are on top of it.
GNSS
Satellite navigation gives excellent position accuracy but needs integrity monitoring (RAIM/SBAS) to be trusted for approaches. Always cross-check GNSS against a conventional aid or against the chart — the classic error is entering a correctly formatted waypoint that is not the one you intended.
KEY TAKEAWAYS
- ▸Variation east — magnetic least. Variation west — magnetic best.
- ▸DME reads slant range, not ground distance.
- ▸1:500,000 VFR chart: 1 cm = 5 km.
Check-ride
Six questions from this module. Score 70% or better to have it signed off in your training record.