The Magnetic Compass is the oldest and most familiar type of compass and is used in different forms in aircraft, ships, and land vehicles. In navigation, direct reading compass ισ an instrument for determining direction on the surface of Earth by means of a magnetic pointer that aligns itself with Earth’s magnetic field.

Variation is the difference between True North and Magnetic North. The Variation for your local area is found by looking at the Compass Rose on your chart. It shows a Magnetic North Arrow, the local variation and the annual rate of change. There are usually several Compass Roses on the chart, look at the one nearest your position.

Deviation: Compass is nothing else but a magnet that always seeks for the Magnetic North. Aeroplanes have a lot of sources that create electromagnetism. Even the airframe itself, since it’s made of metal, affects the compass. To compensate for these errors, a deviation card is installed by the mechanics to help us calculate our real heading.

Magnetic Dip is the tendency of a magnet to align with the Earth's magnetic field lines, causing the north end of a compass needle to dip down in the Northern Hemisphere (positive dip) and up in the Southern Hemisphere (negative dip). The Magnetic Compass will tend to dip more at the poles than closer to the magnetic equator.

Magnetic Dip: Turning Errors: A turning error that can take place involves a turn from a Northerly heading, during that time the compass will briefly indicate a turn in the opposite direction. The other turning error can take place when turning from a Southerly heading, which will cause the compass to indicate a turn in the correct direction, but this will occur at a faster rate.

Remember UNOS (northern hemisphere):

• Undershoot North
• Overshoot South

Magnetic Dip: Acceleration/Deceleration Errors: An acceleration and deceleration error can occur in the Northern Hemisphere, when an aircraft accelerates the compass will begin to show a turn to the north, and as the aircraft decelerates the compass will show a turn to the south. In the Southern Hemisphere, the opposite effect will take place.

Remember:

ANDS (Northern Hemisphere):

• Accelerate North
• Decelerate South

SAND (Southern Hemisphere):

• South Accelerate
• North Decelerate

The cause for the DIP error on the direct-reading compass is the inclination of earth's magnetic field lines.