Navigation Instruments Flashcards Preview

(Me) OOW: Notes > Navigation Instruments > Flashcards

Flashcards in Navigation Instruments Deck (14):
1

What Navigation Instruments can be used from the Bridge?

•Azimuth Mirror
•Sextant
•Gyro/Magnetic Compass
•ECDIS

2

How to take bearings of Celestial/Terrestrial objects with the Azimuth Mirror?

•Point arrow up to take bearing of celestial
•Point arrow down to take bearing of terrestrial

3

What can be Azimuth Mirror be used for?

•Position Fixing.
•Collision Avoidance (Bearing opening = Passing Astern, Bearing Closing = Passing ahead.
•Determining the Compass Error.

4

How may an error occur in the Azimuth Mirror?

If the prism is not horizontal on its axis.

5

What "Correctable Errors" exist on the Sextant, and how are they corrected?

•Perpendicularity
•Side Error
•Index Error

6

What "Non-Correctable Errors" exist on the Sextant?

??

7

What is the advantage of a Magnetic compass over a Gyro compass?

The magnetic compass can determine direction heading from the steering position independent from a power supply.

8

Explain the importance of the Gyro compass?

The gyro compass holds importance because it is relied upon for input by much of the navigational aids located on the bridge.

9

What are the two types of compass cards?

Dry and Wet.

10

What is the liquid inside the bowl of a wet card compass and their ratio?

The liquid inside the wet card compass is a mixture of 2 parts ethyl alcohol to 1 part distilled water.

11

What do the ethyl alcohol and distilled water components of a wet card compass sustain?

•Ethyl alcohol will reduce freezing point in cold conditions.

•Distilled water will reduce evaporation in warm tropical
climates.

12

How would you remove a bubble from a compass?

• Turn the bowl upside down and remove the filling cap
and top it up with pure alcohol. If it is a bowl without a
filling cap inject the alcohol with a syringe.

13

The chief mate tell you the magnetic compass has frozen, what are your actions?

• Obtain the spare bowl from the Nav locker.
• Ensure the correct alcohol to water ratio 2:1 is present.
• Replace the liquid in the frozen bowl with 2:1

14

What maintenance would you carry out every watch as OOW on the magnetic compass?

• Take the compass error.
• Check for bubble in the
compass
• Check for free movement of
the compass card using a
magnet, also known as deflection error.
• Check for any structural changes around the compass.
• Check location of all
corrector magnets, given on
back o
deviation card, DO NOT
ADJUST.
• Check for electrical
installations not allowed
within 1.5m
of magnetic compass.
• Report any problems to
Master.