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Magnetic Compass

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Magnetic Compass

Old 30th Oct 2001, 17:27
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Post Magnetic Compass

Can anyone tell me the type of fluid used in a basic GA Magnetic Compass - and is it at all toxic?(And no, I havn't been drinking it )
Thanks for any replies in advance.
Regards
LF
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Old 30th Oct 2001, 21:30
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I think it's a methanol based compond. There was a CHIRP report published about a year ago where a chappie was nearly killed by a compass leaking onto his carpet on a hot day, the fumes caused himself to nearly pass out and his wife to suffer a serious asthma attack. He eventually landed - what apparently he thought was quite a good landing at the time but was actually about 50 yards off the side of the runway.

G
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Old 31st Oct 2001, 15:25
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Wink

Thanks Genghis, I knew I had read something about it, but couldnt remember where. Ours has a small leak on the climb - but no adverse affects noticed - new one on order.
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LF
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Old 31st Oct 2001, 19:30
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The CHIRP web site has the report here.
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Old 31st Oct 2001, 20:53
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Does anyone know if its correct that the inclination of a MAG Compass in an airline aircraft is adjusted for the amount of inclination that is present at its "home base" = main place of operation? Must be something to it bc inclination is different all over the world and on our ac its always hanging to one side except on the ground at home base...
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Old 31st Oct 2001, 21:17
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I read somewhere that up to, and during the 2nd world war, magnetic compasses were filled with.....whiskey! (?)

A few mechs would *drain* them, and replace with kerosene, but that quite quickly would perish the rubber seals and markings.

I think it is now a mixture that, as well as not being drinkable, will not eat away at anything.

I don't think this is an urban myth?
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Old 1st Nov 2001, 08:39
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magnum, the inclination of a magnetic compass is due to the vertical component of the Earth's magnetic field, which changes from place to place around the world.
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Old 1st Nov 2001, 14:11
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In most cases the liquid is a SILICON fluid (U don't wanna drink that) which:
- is resistant to expansion/contraction caused by T changes
- is not corrosive
- has a low viscosity, a low FZ pt & a high boiling pt.

MF
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Old 3rd Nov 2001, 09:45
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Talking

Old ARB required a compass swing if the aircraft changed its hemisphere of operation !!
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Old 5th Nov 2001, 15:57
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Magnum is almost certainly right, since by definition, compass swings are likely to be carried out at home base anyway.

Compasses are adjusted for Southern or Northern Hemisphere operation and I think that the old ARB rule is still accepted as good-practice. There is an amusing typo in the current Light-Aero Spares catalogue, advertising compasses for "North Hampshire" or "South Hampshire" use, which is a bit too restrictive for me.

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Old 7th Nov 2001, 14:11
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I thought that Isopropanol was the common liquid for compasses and the like. It is in the family
Methanol
Ethanol
Propanol, Isopropanol
Butanol etc

It is an alcohol with a vapour pressure a little below our favourite ethanol, but still toxic and unhealthy in vapour form in an enclosed cockpit.

ET
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Old 7th Nov 2001, 14:42
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Arrow

Yet another answer:

According to Transport Canada Instrument Procedures Manual, the Magnetic Compass is filled with acid-free white kerosene.

Rgds
CB
edited for spelling- it's early here!

[ 07 November 2001: Message edited by: Code Blue ]
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Old 10th Nov 2001, 17:24
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Lightbulb

The type of fluid inside a compass is a simply a function of who manufactured it. All of the above answers are correct except for the whiskey! [It wouldn't work anyway as contrary to highland legends, whiskey is mostly water.] That urban legend came about in the 'good old days' from an excuse used to explain the bottle of Scotch kept in the calibration kit.

I once caught a Tamil labourer in our calibration workshop in Singapore mixing up a jug of alcohol and orange juice for a party. He was using our 100% Isopropyl alcohol

We do often hear of mass death incidents where poor workers have been drinking a bad brew - it seems like I nipped an incident in the bud there.

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