The heading you planned versus the heading you fly and the five corrections between your plotter and your compass
Learn the five corrections that convert a true course from your sectional chart to the compass heading you actually fly.
Every cross-country flight involves a chain of five corrections between the course line you draw on a sectional chart and the number you read on your magnetic compass. The sequence is: true course, wind correction angle, magnetic variation, and compass deviation, producing a final compass heading. Understanding each step is essential for the private pilot checkride and for arriving at your checkpoints instead of a mile and a half to the side of them.
What Is True Course and How Do You Measure It?
True course is the direction of the straight line drawn from your departure airport to your destination, measured from true north. You determine it by placing a plotter on your sectional chart and reading the angle against a line of longitude.
For example, if your plotter reads 070 degrees, your true course is 70 degrees east of true north. This is the starting number in your navlog, but it is not the heading you fly. It is simply the first value in a chain of corrections.
How Do You Calculate the Wind Correction Angle?
Wind almost always has a crosswind component that will push your airplane off the course line unless you compensate. The wind correction angle (WCA) is the number of degrees you point the nose into the wind to stay on track.
To calculate it, use your E6B flight computer. Enter the wind speed and direction from the winds aloft forecast, your true course, and your planned true airspeed. The E6B returns two values: the wind correction angle and your groundspeed.
If the winds at your altitude are from 020 at 20 knots and you are flying a true airspeed of 110 knots on a true course of 070, the E6B will show a wind correction angle of roughly 8 degrees to the left. The wind is coming from your left, pushing you right, so you aim left to compensate.
True course (070) minus WCA (8) = true heading of 062.
A two-degree error over a 60-nautical-mile leg puts you two miles off course at the far end — enough to miss a checkpoint entirely when navigating by pilotage.
How Does Magnetic Variation Change Your Heading?
Your compass does not point to true north. It points to magnetic north, and the angular difference between the two is called magnetic variation. This value changes depending on your location and is printed on your sectional chart along dashed magenta lines called isogonic lines.
Each isogonic line is labeled with a number and a direction, such as “12°W” or “10°E.” The classic memory aid is:
- East is least — subtract east variation
- West is best — add west variation
If you are flying in the eastern United States with a variation of 12 degrees west, you add: 062 + 12 = magnetic heading of 074. If the variation were 10 degrees east, you would subtract: 062 − 10 = 052.
Checkride examiners expect you to get this right on the navlog and explain the reasoning, not just recite the rhyme.
What Is Compass Deviation and Where Do You Find It?
Compass deviation is caused by the metal, electronics, and wiring inside your specific cockpit creating small magnetic fields that pull the compass off magnetic north. Every airplane has a compass correction card, usually a small placard mounted near the compass.
The card lists headings and how many degrees the compass deviates at each one. You interpolate for your magnetic heading. If the card shows +1 degree near your heading of 074, your compass heading becomes 075.
That is the number you actually hold on the compass.
What Is the Correct Order of Corrections?
The full chain from chart to compass:
- True course — measured from the sectional chart with a plotter
- ± Wind correction angle — calculated with the E6B; gives you true heading
- ± Magnetic variation — read from isogonic lines on the chart; gives you magnetic heading
- ± Compass deviation — read from the airplane’s correction card; gives you compass heading
A common mnemonic for the order is “True Virgins Make Dull Company”: True heading → Variation → Magnetic heading → Deviation → Compass heading. When converting in the opposite direction (compass to true), reverse the order and reverse the signs.
Why Does the Heading Change Once You Are Airborne?
The winds aloft forecast is an estimate. The actual wind at your altitude may differ in speed by 5 knots or in direction by 10 degrees or more. Your planned heading gets you close; verifying against ground references gets you the rest of the way.
The practical cycle is: plan, fly, evaluate, correct.
After takeoff, fly your planned heading and watch for your first checkpoint. If it appears off to one side, the wind is different from what you planned, and you adjust.
A rough in-flight correction technique: If you have flown 30 miles since your last checkpoint and you are 2 miles off course, the error is approximately 4 degrees. Double it — correct 8 degrees into the wind to regain the course line. Once back on track, hold half that correction (4 degrees) to maintain it. This is not exact, but it is effective and demonstrates to an examiner that you understand real-time wind correction.
What Are Common Mistakes With Winds Aloft and the E6B?
- Using magnetic instead of true wind direction on the E6B. Winds aloft forecasts report direction in true degrees. Entering the value as magnetic throws your wind correction off by the full local variation — potentially 10 to 15 degrees.
- Confusing wind direction. The reported direction is where the wind is coming from, not where it is going.
- Wrong altitude reference. Winds aloft altitudes are in MSL, not AGL. The lowest reported altitude is usually 3,000 feet; interpolate for nonstandard cruise altitudes.
- Planning but not verifying. The most common student mistake is writing a compass heading on the navlog and never cross-checking it against ground references in flight.
What Does the Checkride Examiner Expect?
The Airman Certification Standards (ACS) for the private pilot certificate require you to plan and fly a cross-country using dead reckoning and pilotage, arriving at checkpoints within a reasonable tolerance. The examiner will watch for your ability to:
- Walk through each correction on the navlog clearly: true course, WCA, variation, deviation, compass heading
- Recognize when you are drifting off course in flight
- Apply a correction and explain your reasoning
When explaining your navlog, state each step out loud in order. It demonstrates that you understand the process, not just the final number.
Key Takeaways
- True course is not your heading. It is the starting point for a chain of four corrections.
- Wind correction angle compensates for crosswind drift and is calculated with the E6B using winds aloft data reported in true degrees.
- Magnetic variation bridges the gap between true north and magnetic north. Use “east is least, west is best.”
- Compass deviation is unique to your airplane and found on the compass correction card in the cockpit.
- Always verify your heading in flight. The plan gets you close; ground references and real-time corrections keep you on course.
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