Question on British compass ?

[Bill Greenwood]

I need to top up the fluid in my compass. It is standard British type, Spitfire, I think the model may be P II. It is the large round one that mounts under the instrument panel. Does anyone know for certain what fluid to use? Most American ones use alcohol, but I seem to recall that a previous one I had may have used a thin oil, I am not sure. By the way it may look antique, but we have found the original one works very well. We tried a modern type but never could get it swung correctly. Thanks

[b29flteng]

I believe all aircraft compasses use naphta. You can find it in any hardware store.

[skymstr02]

Why not use compass fluid? You don't have to reinvent the wheel by trying different compounds that may damage your instrument.

Compass fluid is available at many parts distribution houses, ie, Aircraft Spruce, Chief Aircraft, Wag Aero, etc.

And for clarification, servicing the compass fluid is not preventive maintenance in the FAR's.

[Bill Greenwood]

Sky, that sounds great, but what is in "compass fluid", achohol or kerosene, naptha, etc. ? I don't want to mess up the instrument. Is American compass fluid the same as British? All hydraulic fluid is not the same and not compatable, so -----. Thanks

[b29flteng]

Don't know?????? Maybe someone out here can answer.

[b29flteng]

Did a google search for aircraft compass fluid. Here's one thing I found.

"The case is filled with an acid-free kerosene that dampens oscillations and lubricates the pivot assembly. The pivot assembly is spring-mounted to dampen aircraft vibrations so that the compass heading is more legible."

I found many places that sell refill kits, wether they are compatable with a Britsh manufactured compass, I don't know.

[b29flteng]

Did a google search for aircraft compass fluid. Here's one thing I found.

"The case is filled with an acid-free kerosene that dampens oscillations and lubricates the pivot assembly. The pivot assembly is spring-mounted to dampen aircraft vibrations so that the compass heading is more legible."

I found many places that sell refill kits, wether they are compatable with a Britsh manufactured compass, I don't know.

[Bill Greenwood]

Thanks guys, I think I worked on one of these years ago and what was inside seemed like a thin oil, not alcohol. It probably was kerosene.

[cadet77]

I think that kerosene has a tendency to yellow with age, I saw a similar question on the Stearman Restorers Association website with answer of mineral spirits. The compass fluid bottle label says it is petroleum distillates. If in doubt of the actual contents, check with the compass fluid supplier for the MSDS sheet. As for actual compass requirements, a check with the pertinent instrument manual (if available) or your local instrument shop should narrow the answer.

[Avro Biplane]

Hi Bill,

I have British Avro biplanes fitted with the P compass and understand your concerns, I have just checked British Air Publication A.P. 1743, Vol 1, Section 1, Chapter 2, issued October 1941 (what else!!).

This publication deals specifically with the maintenance of the P type compasses. The instructions are to fill the compass with "a mixture of alcohol and distilled water". Unfortunately, the proportions of alcohol to water is not specified, however the notes do say that proportion is indicated by the specific gravity of the mixture and that this must be measured. There is a table which gives the Stores ref number for compass liquids (sp.gr .81 - .96) plus the Stores ref number for distilled water. I can copy all this stuff for you if you wish. Howard

[HJ]

I've used Airpath Compass Fluid for years in my various P11 and P12 compasses with never a problem.

[Robbie Roberts]

When I was refilling a compass many years back, I contacted Silva, the compass company. They told me to use clear lamp oil- as in oil lamp. It is available at most hardware stores. Don't get the scented stuff- nobody cares how your compass smells.

Robbie

[skybolt2003]

I need to top up the fluid in my compass. It is standard British type, Spitfire, I think the model may be P II. It is the large round one that mounts under the instrument panel. Does anyone know for certain what fluid to use? Most American ones use alcohol, but I seem to recall that a previous one I had may have used a thin oil, I am not sure. By the way it may look antique, but we have found the original one works very well. We tried a modern type but never could get it swung correctly. Thanks

Bill,
Perhaps you know this, but a compass is not an owner repairable part. Nor is an A&P allowed to work on one, other than R&R'ing it. It must be sent to a certified instrument repair station.
Although I'd wager that there are about a million un-logged compass repairs.

[Bill Greenwood]

This owner may contact the instrument shop, but I don't have time to have it sit on their shelf for a month. This is not just a display item that makes the cockpit look authentic, this is the one I fly with. Perhaps the good elves will come in one night and top it off.

[b29flteng]

We hear nothing! We see nothing!