Navigation
Scope
Navigation tests the Earth model, magnetism, charts, time, dead reckoning, radio navigation and performance-based navigation. Calculation questions are common.
Core rules
- True course is measured from true north; magnetic course uses magnetic north. Variation east is subtracted from true; variation west is added.
- Deviation is the difference between magnetic and compass north, caused by aircraft magnetism. “Variation west, magnetic best; deviation east, compass least.”
- A great circle is the shortest path; a rhumb line cuts meridians at a constant angle.
- VOR gives bearing, DME gives slant range, NDB gives relative bearing, ILS gives lateral and vertical guidance.
- PBN specifies RNAV/RNP performance; RNP includes on-board performance monitoring and alerting.
Worked example
True course 090°, variation 10°W, deviation 3°E. Magnetic = 090 + 10 = 100°M. Compass = 100 − 3 = 097°C. Reasoning: westerly variation makes magnetic larger than true; easterly deviation makes compass smaller than magnetic. Apply variation to true, then deviation to magnetic.
Traps
Applying variation in the wrong direction; mixing heading and course when wind is present; using a Mercator chart as if it preserved great-circle bearings; forgetting that DME reads slant range.