Earth's Magnetic Poles

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Questions and Answers

What is the polarity of the magnetic pole in the northern hemisphere?

True north pole

Geographic north pole

Magnetic north pole

Magnetic south pole (correct)

Why does the north pole of a suspended bar magnet point towards north?

Because of the rotation of the Earth

Because it is repelled by the magnetic south pole

Because it is attracted to the geographic north pole

Because of the Earth's magnetic flux lines (correct)

Where is the Earth's magnetic south pole located?

At the South Pole

At about 74°N 101°W (correct)

At the equator

At the geographic North Pole

What is the significance of the shifting magnetic poles and lines of flux?

It requires periodic updates of aeronautical charts Signup and view all the answers

What is the direction that the grid of an aeronautical navigation chart is aligned to?

True North (TN) Signup and view all the answers

What is the term for the difference between true north and magnetic north at a geographic location?

Magnetic variation Signup and view all the answers

What is the purpose of compass compensation in an aircraft?

To align the aircraft on a series of known headings and adjust the compensating magnets Signup and view all the answers

What is the effect of local magnetic fields in the aircraft on an installed magnetic compass?

It causes deviation in the compass indication Signup and view all the answers

What is the purpose of a compass correction card in an aircraft?

To correct for deviation errors during flight Signup and view all the answers

What happens to the deviation error when the aircraft heading changes?

It changes Signup and view all the answers

What is the term for the process of adjusting the compensating magnets to obtain the minimum possible residual deviation error?

Compass swinging Signup and view all the answers

What type of components fitted to an aircraft have the potential to distort the Earth's magnetic field?

Components containing iron Signup and view all the answers

What is the effect of acceleration on the pendulous card in an aircraft?

Two distinct errors: turning error and acceleration error Signup and view all the answers

What causes the centre of gravity of the pendulous card to swing outward and rotate during a turn?

Centrifugal acceleration Signup and view all the answers

When is the turning error greatest in an aircraft?

When turning from a northerly or southerly heading Signup and view all the answers

What determines the direction and extent of turning error in an aircraft?

Aircraft heading, hemisphere, magnetic angle of dip, and angle of tilt of the magnetic card Signup and view all the answers

What happens to the magnet system of the pendulous card when it is tilted?

It is free to rotate under the influence of the vertical component of the Earth's magnetic field Signup and view all the answers

How does the turning error in the southern hemisphere compare to that in the northern hemisphere?

It is a mirror image Signup and view all the answers

What is the reason why a direct-reading compass is not installed on an instrument panel?

To avoid interference from magnetic fields and electrical wiring Signup and view all the answers

What is the primary advantage of a remote-indicating compass system over a direct-reading compass?

It is less prone to interference from magnetic fields Signup and view all the answers

What is the main benefit of incorporating a directional gyro into a remote-indicating compass system?

It enhances the system's stability during turns and acceleration changes Signup and view all the answers

What is the function of a magnetic field detector in a remote-indicating compass system?

To sense the magnetic field Signup and view all the answers

What is the term used to describe the influence of magnetic fields on a compass?

Soft and hard iron magnetism Signup and view all the answers

What is the primary component of a pure remote-indicating compass system?

Magnetic field detector and heading indicator Signup and view all the answers

What is the purpose of a compass check?

To compare with previous compass swing records to determine serviceability Signup and view all the answers

What is the term for the adjustment of a compass to minimize deviation errors?

Compensation Signup and view all the answers

What is the purpose of a Compass Correction Card?

To indicate the difference between the compass reading and the actual magnetic heading Signup and view all the answers

What is the cause of deviation in a magnetic compass?

Local magnetic fields in the aircraft Signup and view all the answers

What is the term for the measurement of the deviation of a compass installed in an aircraft?

Calibration Signup and view all the answers

What is the characteristic of a Direct Reading Compass?

It has the magnetic sensing element and heading indication located in the one instrument Signup and view all the answers

Study Notes

Magnetic Poles

The magnetic pole in the northern hemisphere is a magnetic south pole, and vice versa.
The Earth's magnetic south pole is located at about 74°N 101°W, which is 2000 km from the geographic North Pole.

Magnetic Variation or Declination

The grid of an aeronautical navigation chart is aligned to the geographic north pole (True North, TN).
A magnetic compass aligns to the Earth's magnetic flux, which may be oriented either side of true north (Magnetic North, MN).
The difference between true north and magnetic north at a geographic location is termed magnetic variation, variation, or declination.
Variation is measured in degrees of error east or west of true north.
Variation changes with geographic location, but it is not affected by aircraft heading.

Deviation

Deviation is an error in the indication of an installed magnetic compass caused by local magnetic fields in the aircraft.
Deviation error changes as aircraft heading changes.
Deviation error is measured during a compass calibration.
If the measured deviation is out-of-limits, it can be minimised by adjusting the compass (compass compensation or compass swinging).

Compass Correction Card

The compass correction card is used to correct for deviation errors by the pilot.
The card is mounted close to the compass and indicates the difference between the compass reading and the actual magnetic heading.
The recorded deviation for each Magnetic Heading (MH) is used to calculate the corresponding Compass Heading (CH).

Direct Reading Compass Compensation

Any components fitted to an aircraft that are magnetisable (i.e., contain iron) have the potential to distort the Earth's magnetic field.
The effect of acceleration on the pendulous card can be classified into two distinct errors: Turning error and Acceleration error.

Turning Error

Turning error occurs when an aircraft is in a coordinated turn, causing the pendulous card to remain vertical to the plane of the aircraft.
The extent and direction of turning error are dependent on the aircraft heading, the hemisphere in which the aircraft is flying, the magnetic angle of dip, and the angle of tilt of the magnetic card.

Acceleration Error

Acceleration error is caused by the force of centrifugal acceleration produced by the turn.

Remote-Reading Compass

A remote-reading compass is mounted away from the instrument panel to eliminate interference from magnetic fields.
The system consists of a magnetic field detector and a heading indicator, which may incorporate a directional gyro for increased stability.

Compass Terminology

Calibration is the measurement of the deviation of a compass installed in an aircraft, any necessary compensation of this deviation, and the recording of the residual deviation.
Compensation is the adjustment of a compass to minimise deviation errors caused by the magnetic properties of an aircraft.
Compass correction card is a card mounted near a compass that indicates the difference between the compass reading and the actual magnetic heading.
Deviation is an error in the indication of a magnetic compass caused by local magnetic fields in the aircraft.
Direct Reading Compass is a compass that has the magnetic sensing element and heading indication located in the one instrument.

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Description

Learn about the Earth's magnetic poles and how they differ from the geographic poles. Understand how the magnetic poles affect the behavior of magnets and compasses. Discover the location of the Earth's magnetic south pole and how it changes over time.