Navigation Charting, Plotting and Flight Planning Instruments
Projections
The Mercator projection shows rhumb lines as straight lines and great circles as curves; scale expands with latitude, so it is unsuitable for polar navigation. Lambert conformal conic charts are standard for mid-latitude enroute and approach charts: the cone touches or cuts the standard parallels, great circles plot almost straight, and scale is nearly constant. Polar stereographic charts serve high latitudes, and transverse Mercator is used for grid-based mapping. Grid north differs from true north by the grid convergence, which must be applied when using grid references.
Plotting and the wind triangle
The wind triangle relates true airspeed, wind velocity and groundspeed. Drift is the angle between heading and track; the crosswind component divided by TAS gives drift in radians. Track and groundspeed are plotted first, then heading and TAS applied, with variation to give magnetic heading.
Flight planning
A flight log combines leg distance, forecast wind, TAS, GS, ETA, fuel flow and reserves. Chart reading includes minima, transition altitude, airspace and obstacles; scale and protractor work must be checked against the printed scale bar.
Worked example
TAS 180 kt, required track 090°, wind 315°/30 kt. The wind angle to track is 135°, so the head/tail component is 30 × cos 135° = −21 kt (a 21 kt tailwind) and the crosswind is 30 × sin 135° = 21 kt from the left. Drift = 21/180 rad ≈ 6.7°, so heading = 090 − 7 = 083°. Groundspeed = 180 × cos 6.7° + 21 ≈ 200 kt.
Traps
Plotting true track but flying it as magnetic; using the latitude scale for distance at high latitude on a Mercator chart; ignoring grid convergence; and forgetting the wind when converting between heading and track.