General Navigation
General Navigation tests great-circle and rhumb-line tracks, chart use, magnetism, wind triangle and time. The exam expects sign discipline and approximate mental arithmetic.
Earth and charts
Great circle is shortest; rhumb line is constant track. Mercator exaggerates high latitudes; Lambert conformal preserves shape. Variation is the angle between true and magnetic north; deviation is compass error.
Worked example
True course 090°, variation 5°W, deviation 2°E. Magnetic course = true + west variation = 095°. Compass course = magnetic − east deviation = 093°. If wind is from 360° at 20 kt and TAS 100 kt, the heading must be turned into wind and groundspeed is slightly less than 100 kt.
Time
UTC is used in flight planning; local time differences must be applied carefully. Sunrise/sunset and ETA calculations use groundspeed, not TAS.
Traps
Adding variation when it should be subtracted; confusing deviation with variation; using TAS for ETA; ignoring convergence.