General Navigation
General Navigation tests Earth geometry, coordinates, magnetism, charts, time, wind triangle and navigation systems. Expect practical calculations of track, heading, groundspeed, ETA and fuel.
Core rules
- Great circle is the shortest path; rhumb line is a constant track.
- Variation is the angle between true and magnetic north; deviation is aircraft compass error.
- Wind triangle: groundspeed and drift come from TAS, wind direction and wind speed.
- Time equals distance divided by groundspeed.
- Use a consistent sign convention for easterly and westerly variation.
- Chart scale, projection and grid convergence affect plotted tracks.
Worked example
TAS 120 kt with a direct headwind component of 20 kt gives GS = 120 minus 20 = 100 kt. For 300 nm, time = 300 divided by 100 = 3.0 h. If the wind instead gives a 20 kt tailwind, GS = 140 kt and time = 300 divided by 140 = 2.14 h, about 2 h 09 min.
Traps
- Applying wind as a scalar instead of a vector.
- Mixing true and magnetic references.
- Using TAS as groundspeed.
- Sign errors in easterly or westerly variation.