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post #5 of Old 11-10-2012 Thread Starter
Laugther is Good Medicine
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Location: Bonifay, FL 32425 & Huntingdon, Pa 16652
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Re: Now Blow (how to adjust compass) Me Down

Bearing & All,

I have adjusted compasses in aircraft since 1973, it's one of the items we do as a maint. test pilot. Adjusting a sailboats compass was different for me. I did not have a compass rose or hand held master compass to check accuracy. I have re-read all the info. provided in this post and Chapmans section on it. I went back out to the boat and checked the two compasses out.

I removed the stern compass from its mount (just lifted out) and saw the 2 adjustment (N/ S & E /W) screws. I'm famiiar with using these compass adj. screws. I just need to plan out my procedure. I have learned here or relearned things that will effect the compass accuracy. The area I check it in (mag. grn. fault issues) can affect me. I need to turn on -- all the boats equipment that's on normally or not turned on (normally) when under way. When I check an aircraft compass... we turn everything on too. The heated windshields cause the worst problems.

I plan on using my hand held GPS and take along (master compass) a hand held compass to swing my 2 compasses. I have aircaft (compass) work sheets but do not (rarely) fill them out to make adjustments. I do 1/2 's adjustment(s) at NW & SE headings. I quicky .. dial the compass in to 002 deg. error. I turn to N record, E. S. W then back to North. I compare the (aircraft/ boat ?) to master compass/ GPS readings. This was my 1st step to establish (see) how much I'm off from the master compass/ GPS track results.

Here's where I would normally adjust the compass using the N/S E/W screws per the adjustment work sheet results. I look at the results and adjust the compass to be dead on at -- 330 degrees and again at -- 120 degrees & then back to 330 to make a 3rd adj(if needed). After I have brought these two headings into 002 degree accuracy; I recheck N, E, S, W, for results. Most of the time... I can (now) complete the dev. card with saved time & good accuracy.

I have found that these two (NW & SW) headings give me fastest results and (rarely) very little back & forth for a 3rd or 4th adjustment. I was showed this method by a very expereinced maint. test pilot. I have found a handful of compasses that were not adjustable to 002 ( +/ - ) deg. standards. I replaced them with new ones, and they adjusted out or checked out fine.

Last edited by HighFly_27; 11-10-2012 at 12:00 PM. Reason: mistakes
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