Magnetic Compass Errors: Acceleration

Summary

This video explains the magnetic compass and the acceleration error caused by magnetic dip. It discusses how the magnetic field affects compass readings based on location, with a focus on the northern and southern hemispheres. At the equator, the magnetic force is horizontal, but as you move toward the poles, the compass tilts due to the vertical component of the magnetic field. Acceleration or deceleration during flight can cause temporary errors in compass readings, particularly when flying east or west. The video provides practical examples for both hemispheres, using acronyms like 'ENDS' and 'SAND' to remember the effects of acceleration and deceleration.

Takeaways

• 😀 The magnetic compass is a simple device, consisting of a magnet free to rotate around a pivot point, but it has inherent errors that pilots must be aware of.
• 😀 The main errors affecting the magnetic compass are magnetic variation, compass deviation, and magnetic dip, which can lead to acceleration and turning errors.
• 😀 Magnetic dip occurs due to the earth's magnetic field, with lines being parallel at the equator but becoming more vertical near the poles.
• 😀 At the equator, the magnetic field acts horizontally, while at the poles it is more vertical, affecting the compass's orientation.
• 😀 Magnetic dip causes the compass to tilt when away from the equator, resulting in potential errors under certain conditions like acceleration or deceleration.
• 😀 Acceleration or deceleration can cause inertia to affect the compass, resulting in temporary erroneous heading indications.
• 😀 In the northern hemisphere, during acceleration, the compass will show a false turn to the north, and during deceleration, it will show a false turn to the south (mnemomic: 'accelerate north, decelerate south').
• 😀 The effect of acceleration error is most noticeable when flying on an east or west heading, and is less prominent when flying on a north or south heading.
• 😀 In the southern hemisphere, the acceleration and deceleration effects are opposite to those in the northern hemisphere (mnemomic: 'south accelerate, north decelerate').
• 😀 The magnitude of the acceleration error depends on the latitude and the rate of acceleration or deceleration, and it is related to the magnetic equator, not the geographic equator.

Q & A

What is a magnetic compass and how does it work?

A magnetic compass is a magnet free to rotate around a pivot point. It aligns with the Earth's magnetic field, and the needle points in the direction of magnetic north. Its simple design allows it to provide heading indications, but it can also experience certain inherent errors.

What are the inherent errors of a magnetic compass?

The inherent errors of a magnetic compass are magnetic variation, compass deviation, and magnetic dip. These errors can be further divided into acceleration and turning errors.

What is magnetic dip and how does it affect a compass?

Magnetic dip refers to the tilt of the magnetic compass due to the vertical component of the Earth's magnetic field. At the poles, this vertical component causes the compass needle to tilt, which can cause inaccuracies in the compass reading, especially when the aircraft accelerates or decelerates.

How does magnetic dip affect the compass at the equator versus the poles?

At the equator, the magnetic field is horizontal, so the compass needle is balanced and rotates correctly. Near the poles, the magnetic field becomes more vertical, causing the compass to tilt and experience errors due to magnetic dip.

What is the acceleration error in a magnetic compass?

The acceleration error occurs when the aircraft accelerates or decelerates. In the northern hemisphere, the inertia caused by acceleration causes the compass to deviate slightly to the north, and deceleration causes it to deviate to the south. The opposite happens in the southern hemisphere.

What acronym helps remember the acceleration error in the northern hemisphere?

The acronym 'ENDS' helps remember the acceleration error in the northern hemisphere: 'Accelerate North, Decelerate South'.

How does the acceleration error manifest when flying east or west?

When flying east or west in the northern hemisphere, acceleration causes the compass to deviate to the north, and deceleration causes it to deviate to the south. These errors disappear once the aircraft returns to a constant speed.

Why is the acceleration error less noticeable when flying north or south?

When flying north or south, the center of gravity, pivot point, and inertia are aligned, so the compass does not experience any tilting. As a result, there are no acceleration or deceleration errors in these headings.

How does the acceleration error differ in the southern hemisphere?

In the southern hemisphere, the acceleration error is reversed. When flying east or west, acceleration causes the compass to deviate to the south, while deceleration causes it to deviate to the north. This is the opposite of the northern hemisphere's effects.

What is the difference between the geographic equator and the magnetic equator?

The geographic equator is the Earth's physical equator, while the magnetic equator is the line where the Earth's magnetic field is most horizontal. The magnetic equator does not always align with the geographic equator, and the effects of magnetic dip depend on the position relative to the magnetic equator, not the geographic one.