1 — Track, Heading and the Wind Triangle
A navigation log turns a line drawn on a chart into the numbers you actually fly: a heading to hold, a time for each leg, and the fuel it burns. Everything starts with one idea — where you point is not where you go.
- Track is the path over the ground — the line you drew on the chart, from one waypoint to the next.
- Heading is where the nose points. In any wind that isn’t straight down the track, the two differ.
The wind blows the aeroplane sideways (drift), so to make good your track you must point the nose into the wind by the wind correction angle (WCA). This is the wind triangle — three vectors that always close:
Heading and true airspeed make the air vector; add the wind and you get the track and groundspeed you actually make over the ground.
Air vector + wind vector = ground vector. Heading and true airspeed (TAS, from Lesson 4) give the air vector; the wind shifts it to the ground vector — the track you make good and the groundspeed you make over the ground.
2 — Heading: Wind Correction Angle and Groundspeed
Solving the triangle gives you two numbers for the leg:
- Wind correction angle — turn the nose into the wind. A wind from the left needs a correction to the left; a wind from the right, to the right. The stronger the crosswind component and the slower your TAS, the bigger the angle.
- Groundspeed — TAS adjusted for the along-track wind. A headwind component slows your groundspeed (longer legs); a tailwind speeds it up.
True heading is simply true track ± WCA — add when correcting right, subtract when correcting left.
3 — From True to Compass: Variation and Deviation
The chart is drawn against true north, but your compass points to magnetic north, and the compass itself has small errors. So a true heading becomes a flyable compass heading in two steps — the classic T → V → M → D → C chain:
Variation comes from the chart’s isogonals and changes with location; deviation is your aircraft’s own compass error, read from its compass card. In central Europe variation is only a few degrees.
- Variation is the angle between true and magnetic north, read from the isogonal lines on the chart. Apply it with “East is least, West is best” — variation East, subtract; variation West, add.
- Deviation is your individual aircraft’s compass error, caused by its own metal and electrics. Read it from the compass correction card on the panel, and apply it the same way.
4 — Time, Fuel and Staying on Track
Once you have groundspeed, the rest of the leg falls out:
- Leg time = distance ÷ groundspeed × 60 → minutes. (A 30 NM leg at 90 kt groundspeed = 20 minutes.)
- Leg fuel = leg time × fuel flow (Lesson 7). Sum the legs for trip fuel, then add the reserves.
And once airborne, you check your progress against the line with the 1-in-60 rule:
5 — Put It Together: the Nav-Log Calculator
This is the whole leg in one place. Set the true track you drew, your TAS, the wind (given as the direction it blows from), the variation, the leg distance and fuel flow — and read off the heading to fly, the time and the fuel:
Wind is the direction it blows from. Heading solves the wind triangle; magnetic heading applies variation (East −, West +). Time = distance ÷ groundspeed; fuel = time × fuel flow. Illustrative figures — plan with your POH and current charts.