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Cat B- Mod 11 Aircraft Systems > 11.5.3 Instruments- Compasses > Flashcards

11.5.3 Instruments- Compasses Flashcards

1
Q

What must be installed in a position where it can be seen from both pilot stations?

A

Direction indicator, non stabilised magnetic compass.

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2
Q

What is the indicated heading?

A

The angle between the aircraft’s longitudinal axis, which is shown with the lubber line, and the direction to the North Pole.

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3
Q

What is true heading?

A

True north based on geographic north pole

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4
Q

What is the difference between magnetic north and true north?

A

2000km

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5
Q

What is the angle between true north and magnetic north called?

A

Variation

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6
Q

How much does magnetic north move a year?

A

40 miles per year

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7
Q

How often does Jeppesen update their maps?

A

Every 56 days

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8
Q

What is inclination?

A

The field lines decline to the earths surface.

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9
Q

What are names for the horizontal and vertical components of the magnetic field?

A

Isogonal and Isoclinic

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10
Q

At latitudes above 70 degrees the horizontal component is so weak that a compass is not useable, what should be used instead?

A

Directional gyro or inertial stabilised system.

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11
Q

What is hard iron magentism?

A

Permanent form of magnetism, caused by the presence of iron or steel parts in the structure.

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12
Q

What does the effect of hard iron magnetism have on the aircrafts compass?

A

Bar magnets lying longitudinally, laterally and vertically around the compass position.

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13
Q

To analyse the effect of hard iron the imaginary bar magnets are annotated as?

A

Component P,Q and R

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14
Q

What is soft iron magnetism?

A

Temporary form of magnetism caused by the magnetically soft metallic parts of an aircraft.

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15
Q

What does the effect of soft iron magnetism depend upon?

A

The aircrafts heading and the local angle of dip.

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16
Q

Soft iron magnetism: what is a positive deviation?

A

Deflecting the compass to the right. (Easterly)

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17
Q

Soft iron magnetism: what is a negative deviation?

A

Needle deflects to the left. (Westerly)

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18
Q

What is the only electrical part in a direct reading compass?

A

Light

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19
Q

In commercial aircraft what is the direct reading compass called?

A

Standby

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20
Q

What is the lubber line and what does it do?

A

Vertical line on the standby compass that shows the heading on a rotating compass scale.

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21
Q

When is there no influence on the heading direction of the standby compass?

A

When going north or south.

22
Q

What happens to the standby compass when the aircraft accelerates?

A

It shows a lower heading.

23
Q

How can deviation be minimised?

A

Using small adjustable magnets inside the compass called compass compensation.

24
Q

During compass compensation set up how often is the deviation recorded?

A

Every 90 degrees.

25
Q

What is the B coefficient during compass compensation?

A

Difference between the east and west deviations, divided by 2.

26
Q

What is the C coefficient during compass compensation?

A

Difference between the north and south deviations, divided by 2.

27
Q

For a B correction where does the aircraft normally stay pointing?

A

Easterly

28
Q

For a C correction where does the aircraft stay pointing?

A

Northerly

29
Q

What is coefficient A?

A

A constant error which is the same on all headings.

30
Q

How is an error in coefficient A corrected?

A

Rotating the compass or changing the compass card.

31
Q

What is coefficient B?

A

Varies as a function of the sine of the compass heading. It is usually associated with fore-and-aft permanent magnetism.

32
Q

How is coefficient B corrected?

A

Using fore and aft magnets

33
Q

What is coefficient C?

A

Varies as a function of cosine of heading.

34
Q

What is coefficient C usually associated with?

A

Athwartship and permanent magnetism.

35
Q

What does Athwartship mean?

A

Across the aircraft from side to side.

36
Q

How is coefficient C corrected?

A

With athwartship magnets.

37
Q

What kind of cased light is used in a magnetic compass to avoid deviation?

A

Brass, with contra-wound filament.

38
Q

What is a flux valve?

A

Magnetic sensory device that electrically transmits the information to the aircrafts system.

39
Q

What does a flux valve ‘Z’ mean?

A

Vertical intensity

40
Q

What does a flux valve ‘F’ mean?

A

Total intensity

41
Q

What does a flux valve ‘X’ mean?

A

North

42
Q

What does a flux valve ‘Y’ mean?

A

East

43
Q

Where is the flux valve located?

A

Far away from all magnetic fields of the aircraft.

44
Q

How does the pilot monitor the flux system?

A

With a slaving annunciator

45
Q

What two modes of operation does the flux valve have?

A

Slave and free

46
Q

What does free mode do in a flux capacitor?

A

Flux valve disconnected so it does not monitor or auto realign.

47
Q

What does slave mode mean in the flux system?

A

Default mode, connected and working to information provided by the flux valve.

48
Q

In the flux system how many Hz is the excitor energised with?

A

400Hz

49
Q

In the flux system where does the output of the coils go?

A

Selsyn Unit

50
Q

What does a selsyn unit do?

A

Compares the detected magnetic heading with that indicated on the instrument.

51
Q

After a compass swing the cumulative deviation must not exceed…?

A

5 degrees

52
Q

Why do modern aircraft not need compass swings?

A

Because they have INS and GPS.

Cat B- Mod 11 Aircraft Systems (28 decks)

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