Navigation
What you must know
Study the Earth's coordinate system, latitude and longitude, and great circles vs rhumb lines. Learn chart projections: Mercator, Lambert conformal conic, and their properties. Understand magnetic variation and deviation, and the conversion between true, magnetic, and compass headings (TVMDC: True Virgins Make Dull Company). Study the triangle of velocities: true airspeed, wind vector, and ground speed. Learn dead reckoning, pilotage, and NDB/VOR/ILS/DME/GNSS principles, including VOR radials and CDI indications, and ILS localizer/glideslope. Study time, speed, distance calculations and fuel flow.
Traps
Questions test whether variation is added or subtracted, and whether the error is east or west. Another trap is the difference between a radial from a VOR and the bearing to the station. Also expect the 1-in-60 rule: a 1° error over 60 NM equals 1 NM off track. Watch for wind correction sign errors.
Worked example
True heading 090°, variation 10° W, deviation 2° E. Variation west is added to true to get magnetic: 090 + 10 = 100° M. Deviation east is subtracted to get compass: 100 − 2 = 098° C. So the compass heading is 098°.
Rule of thumb
Use TVMDC: True to Magnetic add west variation / subtract east; Magnetic to Compass add east deviation / subtract west. Reverse for the other direction.