The International Cessna 170 Association

Well ... I found out that up high, there was the hint of an "aroma" and clearly, the makeup of the source might make one feel that all was truly right with the world! I appreciate the FAA information. R/Lee

I once looked up the compass fluid's MSDS. They give little information on it other than it is odorless mineral spirits. One can purchase low odor mineral spirits from the local hardware merchant. It works quite well at about 1/10th of the cost.

I appreciate the information ... thank you!

This Old Thread was being researched to supply a "link" to a Member who called me and inquired about servicing his compass. I think I've already given a correct answer on page-one of this thread, but there appears to be a "legal" view being bandied-about as to whether or not it truly may be serviced by the local A&P or under his supervision.

I believe the most-correct answer is found in FARs:
§65.81 General privileges and limitations.
(a) A certificated mechanic may perform or supervise the maintenance, preventive maintenance or alteration of an aircraft or appliance, or a part thereof, for which he is rated (but excluding major repairs to, and major alterations of, propellers, and any repair to, or alteration of, instruments).....

So that is what the "rule" says.

Some say "What happens in the hangar....stays in the hangar..."

I wonder what the statute of limitations is on the several that I've resealed/refilled over the years.

Rhetorical-tongue-in-cheek question: (Does the rule apply to an Owner?... or just to a "certificated mechanic"... ??

Mine is very dark and almost unreadable in low light situations. I've been wondering if it's the fluid that has turned dark, or the painted numbers that have darkened or both. I have been delaying opening it up to see, but have not been ready yet to open up a potential can of worms. I need to do something about it though.

Hineywheel Bill wrote:Mine is very dark and almost unreadable in low light situations. I've been wondering if it's the fluid that has turned dark, or the painted numbers that have darkened or both. I have been delaying opening it up to see, but have not been ready yet to open up a potential can of worms. I need to do something about it though.

That is exactly why I just replaced the original in my new-to-us "training plane 172". The original is so dark it's unusable. (It was a real trick evading thunderheads while flying westbound-into-the-sun on the ferry-flight with a drifting DG.)

I obtained an excellent replacement from Texas Salvage.... and plan to open up the original to see what can be done to it. I suspect it was re-filled at some point with the wrong fluid which darkened the card. Some folks in the arena have recommended kerosene, naptha, baby-oil, mineral-spirits and all kinds of fluids that may not be as suitable as they think. I suggest paying for a can of the genuine compass fluid rather than take that risk on what has become an expensive instrument. I hope to be able to clean it up and will let you know how that goes.

Thanks! I'd be interested in hearing how that turns out. If I do reseal and refill the original I will definitely order the correct fluid, I'm not smart enough to out-think the instrument manufacturer.

I just located a logbook entry dated 6/2/2010 in which the A&P entered that the (now too-dark/illegible) compass was sealed and filled with "filtered mineral spirits".
(I also note that he did not "approve" it for RTS.)

George, Are you saying he didn’t sign that logbook entry? His signature constitutes a return to service for the work performed. Here’s FAR 43.9(a)(4):

If the work performed on the aircraft, airframe, aircraft engine, propeller, appliance, or component part has been performed satisfactorily, the signature, certificate number, and kind of certificate held by the person approving the work. The signature constitutes the approval for return to service only for the work performed.

It’s actually redundant to write “this XYZ is approved for return to service” and then sign the logbook.

That "filtered mineral spirits" might be the problem. It might be with mine as well, though I have seen no log entry about it. Soon I will order a fluid/seal kit and hope that it lightens up a bit.

Aripath AP1000 Compass Fluid is ISOALKANES/MIXTURE OF C10-C13 ISOPARAFFINS according to MSDS at one source. Aviall says the AP1000 and AP4000 are the same and is a product made by Chevron Phillips called SOLTROL® 130 Isoparaffin Solvent according the the MSDS they list.

The Airpath B16 in my basement has been surviving nicely for years filled with a clear paraffin lamp oil I bought at ACE Hardware.

Mine looks sort of like somebody put swamp water in it.
Hopefully I can clean it up though.

My compass started to leak , so it went into the instrument shop next door. I was going to leave it with them but was told it was a five minute job. The dampening fluid used was Johnny Walker. I had seen the bottle on the shelf and often wondered why it was still there and what did they use it for .[besides the normal activity with Johnny walker]. Compass works just great .

n2582d wrote:George, Are you saying he didn’t sign that logbook entry? His signature constitutes a return to service for the work performed. Here’s FAR 43.9(a)(4):

If the work performed on the aircraft, airframe, aircraft engine, propeller, appliance, or component part has been performed satisfactorily, the signature, certificate number, and kind of certificate held by the person approving the work. The signature constitutes the approval for return to service only for the work performed.

It’s actually redundant to write “this XYZ is approved for return to service” and then sign the logbook.

Thanks for the reminder.

Holy crap! I love it when mole hills are turned into mountains! You can't fly with the back seat out! O-360 isn't approved on floats That shoulder harness is not STC'd