Magnetic Heading: Understanding Compasses and Variation

Magnetic heading is the direction the airplane is pointing compared with magnetic north. If your aircraft is pointed east, the magnetic heading is about 090 degrees. If it is pointed south, the magnetic heading is about 180 degrees.

That sounds simple until navigation introduces another north: true north. Student pilots need to understand both because charts, winds, runways, instruments, and ATC do not always use the same reference. For a companion explanation, read true course vs. true heading.

Magnetic North vs. True North

True north is the geographic north pole, where lines of longitude meet. Magnetic north is the direction a magnetic compass points.

Those are not the same place, and magnetic north moves over time. Because of that, the difference between true north and magnetic north changes depending on where you are and when the chart data was updated.

That difference is called variation, or magnetic declination.

Why Variation Matters

When you plan a cross-country, you may draw a true course on the chart. But in the airplane, your magnetic compass and heading indicator are normally used in relation to magnetic north.

So you must convert true course to magnetic course by applying variation. A common memory aid is:

• East variation, magnetic least: subtract easterly variation.
• West variation, magnetic best: add westerly variation.

For example, if your true course is 100 degrees and variation is 8 degrees east, the magnetic course is 092 degrees. If your true course is 100 degrees and variation is 8 degrees west, the magnetic course is 108 degrees.

The math is simple. The mistake is usually rushing and applying the correction in the wrong direction.

Heading, Course, and Track

These words are related, but they are not identical.

Heading is where the nose is pointed. Course is the intended path over the ground. Track is the path the aircraft is actually making over the ground.

Wind is the reason they differ. In a crosswind, you may point the nose slightly into the wind to keep the aircraft tracking along the desired course. Your magnetic heading may not match your magnetic course, and that is normal.

The Magnetic Compass

The magnetic compass is simple and important. Many standard aircraft equipment lists include a magnetic direction indicator, and it remains a useful backup even in aircraft with modern avionics. For more detail, review the magnetic compass in aviation.

But the compass is not pleasant to read in turbulence or during maneuvering. It swings, lags, and reacts to acceleration and turning errors. Read it during steady, straight-and-level flight when possible.

Also keep metal objects and magnetic items away from the compass. Headsets, tools, phones, mounts, and other objects can affect compass accuracy if placed too close.

The Heading Indicator

The heading indicator, directional gyro, or electronic heading display is easier to use than the wet compass. It is stable and intuitive, which is why pilots use it constantly during normal flight.

Traditional gyro heading indicators can drift. That means the displayed heading slowly moves away from the actual magnetic heading. In aircraft with a non-slaved heading indicator, compare it with the magnetic compass and reset it during straight-and-level, unaccelerated flight.

A good habit is to check it during cruise, after major turns, and before relying on a precise heading for navigation.

Compass Errors Student Pilots Notice

In the Northern Hemisphere, acceleration and deceleration can make the magnetic compass show turning errors, especially on east and west headings. Turns toward north or south can also show lead or lag behavior.

Do not try to chase every compass swing. If you are using a compass for navigation, make small corrections and wait for it to settle.

Parallax can also matter. If you look at the instrument from an angle, the lubber line may appear to show a slightly different heading. Sit normally and read the instrument straight on.

Weather and Runway References

One practical trap is wind direction. Aviation runway numbers, ATC headings, and many cockpit references are magnetic. Some weather products outside the cockpit may use true direction. Your training should make clear which reference is being used in each context.

When in doubt, ask your instructor and check the specific product or chart. Do not mix true and magnetic numbers casually during flight planning.

A Practical Navigation Habit

For each cross-country leg, write down true course, variation, magnetic course, wind correction, and magnetic heading separately. Do not collapse the steps in your head when you are still learning.

Then in flight, compare heading, outside references, GPS track if available, and checkpoints. If your track is wrong, correct the heading. This is the same practical habit used in a cross-country flight plan: plan carefully, then verify with what the airplane is actually doing.

Magnetic heading is basic, but it is not trivial. Use the right north, apply variation carefully, keep your instruments aligned, and your navigation will become much cleaner.

Official References

• FAA Pilot's Handbook of Aeronautical Knowledge
• FAA Chart Users' Guide
• FAA Airplane Flying Handbook