The Magnetic Compass: A Reliable and Fun Instrument

Introduction

The magnetic compass is one of the most reliable instruments in aviation. Despite its age, it continues to play a crucial role in navigation. In this blog, we will explore the principles of flying with a magnetic compass and how it can be used to fly specific headings.

Understanding the Magnetic Compass

At a basic level, we are taught that the compass lags to the north and leads to the south. This lag and lead are approximately based on the latitude you are at. For example, in California, where the latitude is around the 38th parallel, the compass will lag by about 30° to the north and lead by about 30° to the south.

Flying Specific Headings

While the lag and lead are important to know, there is more to flying with a magnetic compass. Here are a few key principles:

1. Don't Believe It When Turning

When you're turning, it's important not to rely on the magnetic compass. Even a slight indication of a turn on the turn coordinator means you should disregard the compass. In order to read your heading accurately, make sure the miniature airplane wings or the pink line on a glass panel are level.

2. Pull Headings In

If you want to fly a heading to the left of the lubber line, you need to pull it in. For example, if you see a heading of 330 to the left, imagine yourself pulling that heading in towards you. This mental exercise helps you stay on track.

3. Graduated Scale

Many people are aware of the 30° lag and lead to the north and south, but the compass actually has a graduated scale. At due east and west, the lag or lead is zero. As you move from north to west, the lag gradually decreases. For example, going from north to west on a heading of 330, the lag would be 20°. This graduated scale allows for flying even more specific headings with the magnetic compass.

A Practical Demonstration

Let's see how these principles work in practice. Imagine you are flying on a heading of west (270°) and you want to turn to a heading of south (180°). Here's what you would do:

1. Begin a standard rate turn to the right.
2. Keep turning until the compass needle reaches 330° under the lubber line (L).
3. Level your wings and ensure there is no turn indicated on the turn coordinator.
4. Finally, look at the compass and confirm that you are now heading south.

By following these steps, you can make precise heading changes using just the magnetic compass.

Timed Turns: A Fine Tuner

In addition to specific headings, timed turns can also be used as a fine-tuning technique. For example, if you need to turn left to a heading of 240° from a north heading, you can use the compass and timed turns to make small adjustments.

Here's how it works:

1. Start the turn to the left.
2. Once the compass reads 230°, roll out and level your wings.
3. Ensure there is no turn indicated on the turn coordinator.
4. Check the compass again to confirm your new heading.

If you find that your heading is slightly off, you can make further adjustments using timed turns. This technique allows for precise navigation, even when small corrections are needed.

Conclusion

The magnetic compass remains an essential instrument in aviation. By understanding its principles and using techniques like specific headings and timed turns, pilots can navigate accurately and confidently. Practice these skills and remember to always set your heading indicator to your magnetic compass for reliable navigation.

Thank you for reading! If you have any specific topics you'd like us to cover in future blogs, please leave a comment below. Don't forget to check out our Ground School app for more aviation insights. Fly safe and happy flying!