General Navigation
What the exam tests
General navigation tests latitude and longitude, great circle and rhumb line, magnetism, heading and track, wind triangle, groundspeed, ETA, map reading and the 1-in-60 rule. The exam expects direction conversions and simple mental arithmetic.
Core rules
- Track is the path over the ground; heading is where the nose points. Drift is the angle between them.
- True heading to magnetic heading: subtract easterly variation, add westerly. The rhyme is east is least, west is best.
- Wind correction angle opposes drift: to maintain track, turn into wind.
- Groundspeed = distance / time. Fuel = burn rate x time.
- 1 in 60: a 1 nm offset at 60 nm is about 1 degree; at 120 nm, 1 degree is about 2 nm.
Worked example
An aircraft flies 60 nm in 20 minutes. Groundspeed is 60 / (20/60) = 180 kt. After 60 nm the aircraft is 2 nm left of track. Using 1 in 60, track error is about 2 degrees. To close the error over the remaining 60 nm, the pilot needs a further 2 degrees, so the heading change is about 4 degrees right, not 2 degrees.
Traps
Do not add easterly variation when converting true to magnetic. Do not confuse heading with track. Do not use the 1-in-60 rule beyond small angles without correction. Do not mix nautical miles and kilometres.