Aircraft Flux Valve Operation Quiz and Flashcards

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Questions and Answers

What is the primary function of a magnetic compass in an aircraft?

To display the aircraft's orientation in respect to the Sun

To display the aircraft's altitude

To display the aircraft's speed

To display the direction in which the aircraft is heading (correct)

What is the role of the magnetic compass in aircraft that employ a remote indicating compass system and radio navigational aids?

Backup navigation system

Primary heading reference

Primary navigation system

Standby compass (correct)

What is the Earth's magnetic field composed of?

Only a horizontal component

A magnetic north pole and a magnetic south pole

Only a vertical component

A horizontal component and a vertical component (correct)

Which component of the Earth's magnetic field is useful in determining magnetic heading?

Horizontal component Signup and view all the answers

What is the Earth's magnetic field similar to?

A huge permanent magnet Signup and view all the answers

What will a freely suspended permanent magnet on the surface of the Earth do?

Align itself with the lines of flux linking the two magnetic poles Signup and view all the answers

What is the location of the Earth's magnetic south pole?

74°N 101°W 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 isogonic lines on a magnetic variation map?

To show the lines of equal magnetic variation Signup and view all the answers

What is the angle of magnetic inclination at the magnetic equator?

0° Signup and view all the answers

What happens to the magnetic poles and lines of flux over a period of years?

They shift slowly Signup and view all the answers

What is the purpose of a direct-reading compass?

To display the direction of magnetic north Signup and view all the answers

What is the direction of the lines of force at the magnetic poles?

Vertical to the surface Signup and view all the answers

What is the term for the grid of an aeronautical navigation chart?

True North Signup and view all the answers

Why must aeronautical charts be periodically updated?

Because of changes in the Earth's magnetic field Signup and view all the answers

What is the effect of aircraft heading on magnetic variation?

It does not affect the variation Signup and view all the answers

What is the purpose of using a liquid in a magnetic compass?

To reduce the effects of friction and wear on the pivot Signup and view all the answers

What property is desirable in a liquid used in a magnetic compass?

Low freezing point Signup and view all the answers

What is the purpose of a flexible element in a liquid-filled compass?

To compensate for changes in the liquid's volume with temperature Signup and view all the answers

What is the result of external leaks in a liquid-filled compass?

The compass becomes unserviceable Signup and view all the answers

Why is low power lighting used in a direct-reading compass?

To reduce the effects of magnetic fields on the compass Signup and view all the answers

What is deviation in a magnetic compass?

An error in the compass's indication due to local magnetic fields Signup and view all the answers

How is deviation error minimized in a magnetic compass?

By adjusting the compensating magnets Signup and view all the answers

What is the purpose of a compass correction card?

To correct for deviation errors Signup and view all the answers

What is the purpose of a compensator in a direct-reading compass?

To reduce the effects of local magnetic disturbances Signup and view all the answers

What is the construction of a compensator in a direct-reading compass?

Two pairs of magnets with bevel gears made of a non-magnetic material Signup and view all the answers

What is the primary function of a direct-reading magnetic compass in an aircraft?

To show the direction in which the aircraft is heading with respect to the Earth's magnetic meridian Signup and view all the answers

What type of compass is used as a standby compass on modern jets?

Vertical panel mounted compass of American design Signup and view all the answers

What is the purpose of the iridium-tipped pivot and sapphire cup in the suspension of the magnet system?

To reduce pivot friction to a minimum Signup and view all the answers

How are the cardinal points identified on the compass card?

With letters Signup and view all the answers

What is the purpose of mounting the magnet system pendulously?

To align the compass with the horizontal component of the lines of force Signup and view all the answers

Why is it important to check the calibration of a direct-reading compass before use on Australian aircraft?

To ensure the compass is calibrated for operation in southern latitudes Signup and view all the answers

What is the primary reason for filling compasses with a liquid?

To make the compass aperiodic Signup and view all the answers

What is the purpose of the spider in the compass fluid?

To damp the movement of the magnet system Signup and view all the answers

What is the effect of gravity on the magnet system assembly?

It decreases the dip angle Signup and view all the answers

What is the dip angle at latitudes above 60° north and south?

Unreliable Signup and view all the answers

What is the total number of deviation coefficients that must be obtained and analysed for each aircraft heading?

Five Signup and view all the answers

Which coefficient is corrected by rotating the compass or flux valve until the compass reads the corrected heading?

Coefficient A Signup and view all the answers

What is the primary purpose of dealing with coefficients A, B, and C in practical compass compensation?

To correct for installation errors and magnetism Signup and view all the answers

What is the characteristic of the mounting holes of the components that are corrected by coefficient A?

Slotted Signup and view all the answers

What is the origin of the deviation produced by coefficient B?

Soft and hard iron magnetism Signup and view all the answers

When an aircraft in the southern hemisphere on an easterly heading increases its speed, what direction does the magnet system appear to rotate?

anticlockwise Signup and view all the answers

What is the primary reason for not installing a direct-reading compass near the instrument panel?

Interference from electrical wiring looms Signup and view all the answers

What is the primary function of a flux valve in a remote-indicating compass system?

To detect the Earth's magnetic field as an electromagnetically induced voltage Signup and view all the answers

What is the characteristic property of the material used to manufacture the flux valve's spokes and horns?

It is easily magnetized but loses its magnetism once the external force is removed Signup and view all the answers

What is the purpose of the collector horns in the flux valve?

To concentrate the magnetic field Signup and view all the answers

What happens to the magnet system when an aircraft in the southern hemisphere on an easterly heading decelerates?

It rotates in a clockwise direction Signup and view all the answers

What is the advantage of a remote-indicating compass system with a directional gyro?

Enhanced stability during turns and acceleration changes Signup and view all the answers

What is the purpose of the damping oil in the flux valve assembly?

To minimize pendulous jarring caused by rapid attitude changes Signup and view all the answers

What is the advantage of mounting the magnetic compass sensing element far away from the instrument panel?

Elimination of the problem of interfering magnetic fields Signup and view all the answers

What is the purpose of the Hooke's joint in the flux valve sense element?

To allow the element to tilt to about 25° Signup and view all the answers

What is the effect of the small change in voltage output from the secondary coils?

To produce an output indicative of the aircraft's heading Signup and view all the answers

What is the purpose of the longitudinally orientated magnets in a compass?

To compensate for error on east/west headings Signup and view all the answers

Where should the flux valves be positioned?

Well away from any magnetic influences Signup and view all the answers

What is the effect of acceleration on the pendulous card in a compass?

It causes the card to tilt and the magnet system to rotate Signup and view all the answers

What is the direction of the magnetic field produced by the magnets in a compass?

Dependent on the direction of rotation of the pinion Signup and view all the answers

What is the purpose of the gyro erection or levelling system?

To maintain the inner gimbal perpendicular to the outer gimbal Signup and view all the answers

What is the purpose of the laterally orientated magnets in a compass?

To compensate for error on north/south headings Signup and view all the answers

What is the rate at which the outer gimbal precesses in azimuth when the error signal is detected?

1-2 degrees per minute Signup and view all the answers

What is the purpose of the fast-align mode in the slaving system?

To synchronise the gyro to align with the magnetic heading Signup and view all the answers

What is the effect of turning on the pendulous card in a compass?

It causes the card's centre of gravity to swing outward and rotate Signup and view all the answers

What is the origin of the name 'slaved gyro'?

The process of slaving the gyro to the magnetic heading Signup and view all the answers

What is the significance of the magnetic angle of dip in a compass?

It affects the extent and direction of turning error Signup and view all the answers

When is the turning error greatest in a compass?

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

What is the purpose of the dot/cross flag in the compass system?

To monitor the compass system's synchronisation with the Earth's magnetic field Signup and view all the answers

What is the effect of acceleration on the magnet system in a compass?

It causes the magnet system to rotate under the influence of the vertical component of the Earth's magnetic field Signup and view all the answers

What is the purpose of the knob on the bezel of the compass system?

To allow rapid manual synchronisation of the card heading to the flux valve heading Signup and view all the answers

What is the indication of the compass system's synchronisation with the Earth's magnetic field?

The pointer is between the dot/cross Signup and view all the answers

What is the characteristic of acceleration error in a compass?

It is greatest when an aircraft is accelerating in a westerly or easterly heading Signup and view all the answers

Why is a compass card made pendulous?

To allow the compass to operate at higher latitudes without an excessive tilt angle Signup and view all the answers

What is the purpose of the compass control panel in more complex systems?

To provide a separate control for the compass system Signup and view all the answers

What happens when DG is selected on the compass panel?

The DG is free of MAG inputs. Signup and view all the answers

What is the effect of hard iron magnetism on compass readings?

A single-cycle error. Signup and view all the answers

What is the source of hard iron magnetism in an aircraft?

All of the above. Signup and view all the answers

What is the effect of soft iron magnetism on compass readings?

A two-cycle error. Signup and view all the answers

When does the greatest soft iron magnetism error occur?

On NE, SE, SW, and NW headings. Signup and view all the answers

What is the purpose of the synchronising indicator mode selector?

To synchronise the DG with the MAG Flux. Signup and view all the answers

What happens when Slaved (SLA) is re-selected?

The DG will align to magnetic north at a rapid rate. Signup and view all the answers

What is the purpose of the course/heading set knob?

To control the heading bug on the indicator. Signup and view all the answers

Why is it important to understand aircraft magnetism?

Because it is a potential source of error in compass readings. Signup and view all the answers

What is the difference between hard iron and soft iron magnetism?

Hard iron is permanent, while soft iron is temporary. Signup and view all the answers

Study Notes

Direct-Reading Compass

The primary function of a direct-reading magnetic compass is to show the direction in which an aircraft is heading with respect to the Earth's magnetic meridian.
There are two common types of direct reading compasses: Vertical panel mounted compass of American design and Suspended type of British design.

Construction of Direct-Reading Compass

The compass consists of a non-magnetic metal or plastic case which houses the magnet system.
The magnet system consists solely of a single annular cobalt-steel magnet, to which is attached a compass card.
The suspension consists of an iridium-tipped pivot secured to the centre of the magnet system and resting in a sapphire cup supported in a holder or stem.

Magnetic Inclination

The compass magnet system is mounted pendulously, with the magnet below the point of suspension to counter the effect of dip.
Gravity acting on the magnet assembly pulls it into a smaller angle, reducing the apparent dip angle in aircraft compasses to approximately 3 degrees between the latitudes 60° north and south.

Compass Fluid

The primary reason for filling compasses with a liquid is to make them aperiodic.
Liquids used include mineral or alcohol, and some special silicone liquids.
Desirable properties of a liquid include having a low freezing point, low viscosity, no corrosive properties, and remaining free from discolouration.

Compass Illumination

Direct-reading compasses are illuminated by a small bulb for nighttime or low-light flying.
Power to supply this is usually fed through either screened cable or a twisted pair to minimize the magnetic field produced by current flow in the wire.

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, and is measured during compass calibration.
The adjustment phase of the calibration procedure is called compass compensation (compass swinging).

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.
Every compass is fitted with a compensator which is calibrated during a compass swinging process to minimise the effects of the local magnetic disturbances.

Slaved Gyro

Remote compass systems commonly use an electrically driven directional gyro, often remotely mounted, to provide short-term stability of magnetic heading presentation.
The gyro slaving system detects any mismatch between the flux valve and the gyro heading output caused by real and apparent gyro drift.

Compass Indicating Elements

Magnetic heading information is presented in a vertical card format on a variety of instruments depending on the system.
The compass card is driven by a servomechanism which rotates in response to heading changes.
The aircraft's magnetic heading is read off under the lubber line placed at the top of the dial.### Magnetic Poles
The magnetic pole in the northern hemisphere is actually a magnetic south pole, and vice versa.
This explains why the north pole of a suspended bar magnet (or a compass needle magnet) points towards the north.
The geographic and magnetic poles are not located together.
The Earth's magnetic south pole is located at approximately 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).
A magnetic compass aligns to the Earth's magnetic flux, which may be oriented either side of true north (Magnetic North).
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.
An installed compass and a compass that has been removed from the aircraft are both equally affected by variation.
Magnetic variation maps show lines of equal variation, called isogonic lines (or isogonals).
Isogonic lines enable pilots to determine the magnetic variation at a specific location.

East and West Variation

There is no practical way to compensate (adjust) a direct reading standby compass for variation because variation changes as the aircraft travels.
Variation is the difference between true north and magnetic north at a specific geographical location (aircraft position).
Variation does not change as aircraft heading changes.
A compass cannot be compensated for variation.
The pilot must take variation into account and correct for it when navigating.

Magnetic Inclination or Dip

In a magnet, the lines of force emerge vertically at the north magnetic pole and descend vertically into the south magnetic pole.
The Earth's lines of force behave similarly, emerging at the South Pole and returning at the North Pole.
The lines of force form great arcs around the surface of the Earth, being horizontal only at the magnetic equator.
The angle the lines of force make with the Earth's surface at any given place is called magnetic inclination or magnetic dip.
The angle varies from zero degrees at the magnetic equator to 90 degrees at the magnetic poles.