Magnetics and the Standby Compass Flashcards Preview

Basic Instruments > Magnetics and the Standby Compass > Flashcards

Flashcards in Magnetics and the Standby Compass Deck (17):
1

Example of ferris material

Steel
Cast iron

2

Colour of the north seeking magnet

The blue end

3

To increase a magnets strength

Bigger, heavier and longer

4

Magnetic variation

Variation is the angular difference between 2 meridians

5

Field components

H field - drives the compass towards its respective pole

Z field - caused by dip and increases in as you go towards the pole

6

Aclinic/ isoclinic lines

Lines of 0 dip

7

Magnetic poles move at a rate of

10 miles a year

8

The poles flip every

450,000 years

9

Short term predictable and unpredictable changes in magnetic equator

Predictable - changes in the suns orbit
- daily changes in the height of the ionosphere

Unpredictable - solar winds, interacting with the magnetic field, more significant at high latitudes

The poles moving as the earth rotates

10

Magnetic direction

Taken from magnetic north

Half a diamond/arrowhead

11

Isogonal

Lines of equal variation

Variation is shown on charts as isogonal

12

The compass swing

Re calibrates the compass to minimise deviation

The a/c has to be free from any magnetic interference, engines not running

A/c is turned around for every degree and values are compared with a reference instrument and put on a deviation card

13

E type standby compass

Read visually
No electrical inputs and outputs
Reliable and not easy to read

Freely suspended magnet which will seek its nearest pole either side of the magnet

14

Lubber line

White vertical line on the glass if the compass

Reference to the a/c longitudinal axis

15

Improving sensitivity

Improved by using 2,4 or 6 high quality permanent magnets

Short magnets also help keeping the CG low

More magnets promote sensitivity

16

Aperiodicity

Describes the need for the magnet to settle down quickly after turbulence or a manoeuvre

Achieved by filling the compass bowl with oil which promotes damping

17

Errors

Due to the compass being on a pivot the CG is displaced N or S of the pivot due to the dip causing a “couple”

Manoeuvres cause inertia which acts on the magnets CG

Accelerations due east/west cause the max error
Error is about 20-30 degrees