You draw a line on the chart, measure its angle, and now you need to know what to put on the heading indicator. In between sit three corrections: the wind, the difference between true and magnetic north, and the error of the compass itself. The FAA test asks about each of them, often with a calculation. Once you see them as a single chain, the whole topic becomes mechanical.
The chain is TC → (WCA) → TH → (VAR) → MH → (DEV) → CH. Correct into the wind. From true to magnetic, east is least, west is best: subtract easterly variation, add westerly. The wind correction angle is about the crosswind component ÷ (TAS ÷ 60).
Course, Heading, Track
Three words that students mix up, and exam questions rely on it:
- Course: the path you intend to fly over the ground, measured on the chart.
- Heading: the direction the nose points.
- Track: the path you actually fly over the ground.
In no wind, all three are the same. With a crosswind, the airplane drifts, so to hold the course you point the nose a little into the wind. The angle between the course and the heading is the wind correction angle (WCA). The angle between the heading and the track, if you do not correct, is the drift angle.
The Chain From Course to Compass
| Step | Start | Apply | Result |
|---|---|---|---|
| 1 | True course (TC) | Wind correction angle (WCA) | True heading (TH) |
| 2 | True heading (TH) | Variation (VAR) | Magnetic heading (MH) |
| 3 | Magnetic heading (MH) | Deviation (DEV) | Compass heading (CH) |
Variation is the angle between true north and magnetic north. It depends on where you are and is shown on the sectional chart by dashed magenta isogonic lines. Deviation is the error of the airplane’s own compass, caused by magnetic fields in the airplane, and is shown on a small correction card near the compass.
Variation: Which Way Do You Go?
Going from true to magnetic, remember “East is least, west is best”:
- Easterly variation: subtract it (magnetic is smaller).
- Westerly variation: add it (magnetic is bigger).
Going from magnetic to true, reverse it. That is the question the test likes: “when converting from magnetic course to true course, you should add easterly variation and subtract westerly variation”. The rule never depends on the heading you are flying.
Wind Correction
The wind blows the airplane sideways, and you counter by pointing the nose into it. Two numbers matter: the angle between the wind and your course, and the wind speed.
- Crosswind component = wind speed × sin (angle between wind and course)
- Headwind or tailwind component = wind speed × cos (that angle)
A wind straight across your course (90°) is all crosswind. A wind straight on the nose is all headwind and needs no correction at all.
A good approximation for the correction:
WCA ≈ crosswind component ÷ (TAS ÷ 60)
A Worked Example
You fly a true course of 090° at 100 knots true airspeed. The wind is from 360° at 20 knots. Variation is 5° west. The compass card says to add 2° on this heading.
1. Wind correction. The wind is exactly 90° to your course, so the whole 20 knots is crosswind. WCA ≈ 20 ÷ (100 ÷ 60) = 20 ÷ 1.67 ≈ 12°. The wind comes from the north, so you correct to the left (north), into the wind:
TH = 090° − 12° = 078°
2. Variation. West variation is added going from true to magnetic:
MH = 078° + 5° = 083°
3. Deviation. The correction card says add 2° here:
CH = 083° + 2° = 085°
You steer 085 on the compass. And the groundspeed? The airplane is crabbing across the wind, so a bit of airspeed is spent on the correction: GS ≈ TAS × cos(WCA) = 100 × 0.98 ≈ 98 knots.
4. Time and fuel. For a 60 nautical mile leg, time = 60 ÷ 98 × 60 ≈ 37 minutes. At 8 gallons per hour, fuel ≈ 8 × 0.61 ≈ 4.9 gallons.
Notice the order. You never convert true to magnetic until the wind is already in the heading, because the wind works relative to the true course.
Headwind, Tailwind and Groundspeed
Even without crosswind, the wind changes your groundspeed:
- A headwind subtracts from your TAS, so the trip takes longer and uses more fuel.
- A tailwind adds to your TAS, so the trip is faster.
- Time = distance ÷ groundspeed, and fuel = time × fuel flow.
Always use groundspeed, not airspeed, to calculate time and fuel. It is a very common test trap.
A Related Rule: VFR Cruising Altitudes
Your magnetic course also decides your VFR cruising altitude. Above 3,000 feet AGL and below 18,000 feet MSL:
- Magnetic course 0° to 179°: odd thousands plus 500 feet (for example 3,500, 5,500, 7,500)
- Magnetic course 180° to 359°: even thousands plus 500 feet (for example 4,500, 6,500, 8,500)
Use the course, not the heading: with a strong crosswind they can fall on opposite sides of 180°.
Common Mistakes
- Correcting the wrong way. If the wind is from the right, point the nose to the right of your course.
- Mixing up the direction of variation. Write TVMDC (True, Variation, Magnetic, Deviation, Compass) and “east is least” at the top of your page and use them every time.
- Using airspeed instead of groundspeed for time and fuel.
- Confusing wind direction. Wind is given as the direction it comes from.
- Doing it in the wrong order. Course to true heading, then variation, then deviation.
Practice It
AltiPrep FAA has navigation questions on heading conversion, wind correction, groundspeed, time and fuel, each with a worked explanation, so you can drill the arithmetic until it is automatic.
This article is a study aid. For real navigation, use current charts and your airplane’s own compass correction card.
Keep reading: FAA Private Pilot Knowledge Test: Format, Subjects and How to Pass · How to Read a METAR and TAF · Weight and Balance Explained · VFR Weather Minimums and Airspace Classes · Stalls and Load Factor Explained
Frequently asked questions
What is the difference between course, heading and track?
The course is the path you intend to fly over the ground. The heading is the direction the nose points. The track is the path you actually fly over the ground. With a crosswind, the heading differs from the course by the wind correction angle, and if you do not correct, the track drifts away from the course.
In which order do you convert a true course into a compass heading?
Start with the true course (TC), apply the wind correction angle to get the true heading (TH), apply variation to get the magnetic heading (MH), then apply deviation to get the compass heading (CH). The chain is TC, WCA, TH, VAR, MH, DEV, CH.
Do you add or subtract variation?
From true to magnetic, add westerly variation and subtract easterly variation: east is least, west is best. From magnetic to true, do the opposite: add easterly variation and subtract westerly variation.
Which way do you correct for a crosswind?
Always turn into the wind. If the wind is from the right of your course, your heading will be to the right of your course. The stronger the crosswind component and the slower the airplane, the larger the correction.
Is there a quick way to estimate the wind correction angle?
Yes. Find the crosswind component (wind speed multiplied by the sine of the angle between the wind and the course) and divide it by your true airspeed divided by 60. For a 20-knot crosswind at 100 knots true airspeed that gives 20 divided by 1.67, about 12 degrees.