46 Magnetism

Question 1

Magnetic meridian

Answer 1

the direction of the horizontal component of the earth’s magnetic field at a point

Question 2

Magnetic dip

Answer 2

the angle between the local horizontal and the total magnetic field

Question 3

Secular change

Answer 3

verage value changes in the earth’s magnetic field over time, reflecting changes in the Earth’s core = unpredictable

Question 4

Deviation:

Answer 4

The angular difference between compass north and magnetic north
Caused by deviating effects of magnetic material and electrical disturbances within the aircraft
Measured in degrees east or west

Question 5

Hard iron magnetism

Answer 5

Caused by the permanent magnetism (metal structures) and DC circuits of the aircraft
Remains constant with changes to heading and magnetic latitude
Considered permanent

Question 6

Soft iron magnetism

Answer 6

caused by the magnetism induced into soft material. Consists of magnetic fields induced solely by the earth’s magnetic field
varies with changes in heading and magnetic latitude

Question 7

Reducing the deviating effect on a compass

Answer 7

Sensor placement: on wingtip or in tail
Compensate for hard magnetism: introduce an equal/opposite magnetic field at the sensor
Calculate deviation: provide a correction card for several headings or actually calculate after heading changes