Magnetic Compass

Question 1

Requirements SOLAS

Answer 1

SOLAS Ch5,
All ships irrespective of size to have,
Properly adjusted standard magnetic compass, or other means, independent of and power supply, to determine the ships heading and display the reading at the main steering position

A pelorus or compass bearing device or other means, independent of any power supply, to take bearings over an arc of the horizon of 360°

Means of correcting heading and bearings to true at all times

Question 2

Irish Law

Answer 2

Merchant Shipping Navigational Equipment Rules 1985

SI 280 of 1985

Question 3

Full Compensation

Answer 3

1. Balance the VFI and note the value of H
2. Check the lubber line is in the fore and aft line
3. An estimated amount of flinders bar is shipped, usually forward
4. The spheres are shipped halfway along their brackets
5. Ship steadied on each intercardinal compass heading, the deviation observed and coefficient D calculated. The spheres are adjusted to alter the deviation by the amount of the calculated coefficient
6. The compass is unshipped, ship steadied on NESW amd value of landa found
7. The ship is steadied on east west magnetic, and the heeling error is corrected using vertical force instrument
8. Assuming coefficient B larger than coefficient C, steady the ship on E W, observe deviations, calculate coefficient B and correct with fore and aft magnets
9. Steady ship on N S, observe deviation, coefficient C calculated, correct with athwartships magnets
10. Swing ship slowly and observe deviations, preferably 16 points
11. Calculate residual approximate coefficients to ascertain any important inaccuracies which may require a second swing and readjustment

Question 4

Apparent A

Answer 4

Compass card not accurately centred
North/South needle not parallel
Lubber line not in fore and aft line
Azimuth mirror out of true

Question 5

Spare mag compass reg

Answer 5

> 150gt