Seamanship Class 4 Flashcards
What types of marine sextant are there?
There are two types in common use, micrometer and vernier sextants. The difference between the two mainly lies in the method of graduating and reading the arc.
What are the three main errors on a sextant?
The three main correctable errors are:
* Perpendicularity error
* side error index error.
When correcting a sextant for errors, is there an order in which they must be corrected?
Yes, errors should be corrected in the following order:
1st - Perpendicularity error
2nd - Side error
3rd - Index error.
What is perpendicularity error?
Perpendicularity error is present if the index mirror is not perpendicular to the plane of the sextant.
What is side error?
Side error is present if the horizon mirror is not perpendicular to the plane of the sextant.
What is index error?
The index arm of the sextant must be parallel to the horizon mirror when the index arm is set at zero. If not, then index error is present.
What fires are foam extinguishers designed for use on, and how?
Foam extinguishers are primarily designed for use on oil fires. The foam should not be discharged into the burning liquid, but instead directed at a vertical structure to allow it to flow gently over the surface, thus forming a seal which prevents the vapours mixing with the atmosphere. In the case of mechanical foam extinguishers do not point the nozzle directly at the oil before activating as water is discharged initially and will create a ‘flash’.
How may a fire hose become damaged?
A fire hose can become damaged by:
-Mildew or by chemicals
- dragging round sharp corners
-being trodden on sudden changes in pressure
-shutting off too quickly.
What are the studs in the anchor cable for?
The studs prevent the individual links deforming (stretching) under stress.
How would you secure an anchor for sea?
To secure an anchor for sea:
-Check windlass brakes are screwed up tight, the compressors are on and both cables are out of gear
-Attach the devil’s claw and hawse pipe covers
-cement spurling pipe covers or attach steel plates with proper
canvas covers.
What signals may a vessel display to show that it is not safe to fire a rocket?
To show that it is not safe to fire asmaket exhibit:
* By day - code flag ‘B’
* by night - red light at the masthead
* in poor visibility - whistle signal ‘GU’
When a BA party is entering a space attached to a lifeline, in the absence of voice communication equipment, what signals can they make?
A system of signals are set up by tugging on the lifeline:
1 pull - we advance
2 pulls - we stop
3 pulls - we return.
What pre-donning checks would you make to a positive pressure
BA set before wearing?
Check the following:
1. Visual inspection of the equipment
2. don the face mask
3. open cylinder fully, check contents (80% or more is required)
4. close cylinder, holding breath, the gauge should not drop more than 10 bars in 10 seconds
5. open cylinder valve, breathing several times to check demand and exhalation valves
6. close cylinder valve and breathe, as air is being consumed whistle must sound between 40-45 bars.
Can a lifting plant be used to lift a person?
A lifting plant can be used to lift personnel only if it is designed for this purpose or in an emergency.
When rescuing a casualty from an enclosed space, what are your priorities?
Priorities in rescuing an enclosed space casualty are:
* Restoration of their air supply at the earliest opportunity, and
* unless the casualty is gravely injured, such as a broken back, removal from the space as quickly as possible.
