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9.5.3 The Earth's magnetic field

The internal composition of the Earth means that it can be considered as a large

magnet with a magnetic field around it and with magnetic poles, where the

magnetic field is strongest at each end.

9.5.3.1 Inclination

A freely suspended magnetic needle will form an angle, called inclination, with

the Earth's surface depending on where on the surface the needle is located.

See the gray arrows on the illustration next page.

At the magnetic equator, midway between

the magnetic poles, the angle will be zero (the

curved line), which means that the magnetic
needle will lie horizontally parallel to the

Earth's magnetic field. This is where there is

the least error when we turn or change speed

when flying.

o
Above the magnetic poles the angle is 90 , and the magnetic needle will
therefore be almost vertical (as shown in the drawing on the previous page).

The magnetic needle is used in the aircraft's magnetic compass. The steering

course is indicated by the direction the needle (the red part of the needle) points,
since the compass needle will point north regardless of the aircraft's direction.

A compass rose with a division in degrees is arranged so that it follows the needle

in motion, and we can read which direction the aircraft's nose is pointing.

We call this our "compass heading"

Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 832