Whiskey Compass

J

JRitt

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Clarksville TN
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Display name:
JRitt
The compass on my 172N had new seals installed on the last annual (11 mo ago) and has leaked out all of it fluid (overnight) again so I want to replace it. Its a surface mount. Can I get any one I want and have it installed? Anybody like one brand/model over another?
 
JRitt said:
The compass on my 172N had new seals installed on the last annual (11 mo ago) and has leaked out all of it fluid (overnight) again so I want to replace it. Its a surface mount. Can I get any one I want and have it installed? Anybody like one brand/model over another?
Click to expand...

If it were me, I'd replace it with a vertical card compass. Come to think of it, I did that in my airplane, and both helos have them as well...
 
RotaryWingBob said:
If it were me, I'd replace it with a vertical card compass. Come to think of it, I did that in my airplane, and both helos have them as well...
Click to expand...
What advantages are there with a vertical card compass over a regular wet compass.
 
JR i have a used compass i bought for in my pick-up but radio interfers with it, if your interested email me i'll sell it for $50 + shipping.
Dave G
P.S. this mounts flush on top of dash.
 
JRitt said:
What advantages are there with a vertical card compass over a regular wet compass.
Click to expand...

Well, for one thing, left is left and right is right. It's also more stable.
 
I've bumped into several of those vertical card compasses in my travels for PIC, and generally speaking, they've been wildly inaccurate. They also have to be mounted so they dangle, and that can make them even harder to read in turbulence or during maneuvering. I'd stick with the classic unit.
 
Ron Levy said:
...they've been wildly inaccurate.
Click to expand...

Hmm... Odd. Not the ones I've seen, but that was only a few, and those were in RV-6s. I know the vertical card ones are supposed to "hold still" better than a regular wet compass. False advertising? One brand better than another, maybe?
 
In my limited experience, ive definitely not found a vertical card to be any better than a regular compass. the only advantage is that it is displayed in the 'normal' orientation like a DG
 
JRitt said:
What advantages are there with a vertical card compass over a regular wet compass.
Click to expand...

Advantages: Easier to read - And it goes right when you turn right just like a DG.

Disadvantages: My CFII says (as Ron does) that the errors are much larger on the vertical ones. Checking the compass card and thinking the reverse number of degrees and setting that is probably as hard as thinking about what your regular compass is really telling you.

I'd go with the slaved HSI. :yes: ;)
 
Jritt;I installed a VCC in my AA1B (the Percision 700; I won't speak for the Falcon Knock offs) and it swung 1-2* in each quaudrant.
In the air it was easy to read and never gave a moments problem in the 2 years I owned the plane. It was accurate enough to set my DG and I never I always got to where I was aiming for.
I've installed (or helped to install) P-700's in 3 aircraft besides my own and only one gave any problems. On that one we Degaussed the cage of the Citabria and added the balancing balls and the VCC was happy.
There's nothing wrong with the old float compass if you're comfortable with it...but once you get used to the DG look and read of the VCC you miss it if you fly without it.

JUMP and YMMV.

Chris
 
JRitt said:
What advantages are there with a vertical card compass over a regular wet compass.
Click to expand...

how about no more of JRitt's problem... fluid leaking out!



If a VCC is showing excess error my guess is:


a) it was not swung properly to begin with or

b) it was installed because someone found a problem 'with the old compass' -- which was truly a problem with the airframe (magnetism in the airframe, someone replace brass screws with steel, new radios interfered with the compass, HH GPS antenna thrown up on the glareshield take your pick or add your own) that was blamed on the old compass. So they installed a VCC and guess what, nothing improved because they diagnosed it inadequately. So they throw up their hands and leave the VCC in place. (and now the stats for VCCs appearing to be 'always in error' increases!)


I like mine.
 
Does anyone have knowledge about this model? It's in my wholesale catalog:

http://www.edmo.com/index.php?module=products&func=display&prod_id=7593&disp=desc&cat_id=505

PAI-7005VR.jpg

VERTICAL CARD COMPASS 5V/RED (PAI-7005VR)

I'm finding it helps to keep notes on various items for that time when I start a project of my own. Very soon, I'll have a house with a double garage and lots of space for a large storage shed.
 
From the Avionics West of Tennessee website

http://www.avionicswest.com/articles.htm

How about the Vertical Card Compass? Well for years I slammed the vertical card compass because in nine out of ten aircraft they wouldn’t fall into calibration. The problem is industry wide, in most cases they are worthless. (Sure, I heard about a friend of a friend that had one that worked properly but I never met anyone personally who did.) It became a policy in our shop to refuse to install the vertical card compass because of the problems we encountered. We found problems with this compass in every aircraft regardless of the manufacturer. They oscillated and had gross errors on some headings. Finally one day I was sitting around with nothing to do so I thought I’d try to find out why the vertical card compass didn’t work as it should. After all, they meet TSO C7c-1 but why don’t they work in the aircraft. The first thing I did was disassemble a vertical card compass. The quality of the machine work inside was great. I found a basically square magnet with a gear on it suspended in a gimbal. Another gear was attached to a shaft and turned the compass card. Real basic stuff. I noted that if I rotated this compass in certain directions the card would oscillate it slightly shook the case. Ten degrees difference in heading and the oscillation would cease.. I blame this on the square magnet, maybe a different design would help. But I still didn’t see any reason the vertical card compass would not properly swing. As I moved this compass around in open air, I found this compass seemed to point in properly. So out to the hanger we go looking for an innocent victim to install the compass in. In the corner sat a lonely C-172 waiting to be worked on. We pulled the little Cessna out and checked the wet compass that was already installed. We found this compass was accurate within +/- two degrees. So out came the factory Airpath and in went the vertical card compass. We found during our swing that on "North" through "East" was right on but between 120 and 240 we had over forty degrees of error and no way to adjust it out! My first words were "Typical vertical card compass". We removed the suspect compass and found that now it didn’t track properly out of the aircraft as it did prior to installation. What happened? Did the installer drop it or did it get magnetized? Now we disassemble the case again and find the magnet had come out of the gimbal. Our question was, "why?" We thought that since this vertical card compass was "used", maybe it was already in the failing mode and finally bought the farm. Now I have to figure out what is going on. The parts department now orders a new PAI-700/28 vertical card compass to the tune of $366.50. It arrived in a couple days and I walked around outside to verify the thing appeared to track correctly and it did. This time I personally installed the vertical card compass in the 172 and to the compass rose we went. This time I found errors of thirty degrees in the 60-120 area. So out came the vertical card compass and in went the trustworthy wet compass. As before, the wet compass was working fine. As I walked outside with the recently purchased compass I now found that the thing had different readings than before when I pointed it in the same direction! We disassembled the new vertical card compass and found the magnet had partly separated from the gimbals, much like the first compass that failed! " What gives?" we questioned. We completely disassembled the vertical card compass and found the magnet was held in the gimbal by small pin but the top of the magnet just floated on its gimbals. We carefully reassembled this compass. For some reason the installer was pointing to the inside of the vertical card compass showing me why he thought the compass failed. As he got closer with the screwdriver the magnet pulled out of the top gimbal again. What this told us was that anytime you install the vertical card compass with normal "magnetic" tools you run a high risk of pulling the magnet out of the gimbal therefore causing the compass to fail. Again we properly assembled the vertical card compass and installed the case with a brass "non-magnetic" screwdriver. We installed it in the Cessna again using the brass non-magnetic tool. We found this compass now would come within three degrees of the proper magnetic heading. This was great. What we found was that probably in prior installations we used steel screw drivers that destroyed the compass before we had finished the installation! I flew the Cessna and found on some heading the compass card had a little oscillation but even with this little problem the vertical card was superior to the wet compass. We were all happy that we finally solved the problem on why vertical card compasses usually don’t work. Then someone said, "What if the pilot lays a flashlight near the compass"? We did and as my luck would have it the compass now had gross errors on some headings. We removed the vertical card and reinstalled the wet compass much to my disappointment. I think that if the top gimbal had a small recessed hole and the top of the magnet had a pin to help hold the magnet in the gimbals better this thing would work but we can’t change the design.

The vertical card compass has some advantages over the wet compass. It looks like a directional gyro and you turn toward the number you want to go to instead of backward like you do with the wet compass. The vertical card compass doesn’t have the lead and lag problems associated with the wet compass. The down side of course is the vertical card compass is prone to problems and large errors. I am determined to find a way to make the vertical card compass work in our Cessnas. You haven’t heard the last on this subject!
 
Any aircraft without a whiskey compass in the cockpit somewhere,
is just plane wrong.
 
We have a vertical card compass in the R182 but it's mounted from the top of the cabin behind the windscreen. Nothing is laid nearer than about twelve inches but even then it may be keys or a knee board. Headsets are usually off to the side if on the glare shield or hanging on the yoke. This could be the reason I've never noticed any significant error other than standard lead or lag errors. Steve, I gather all of your installation attempts were right on top of the glare shield.
 
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Ron Levy said:
I've bumped into several of those vertical card compasses in my travels for PIC, and generally speaking, they've been wildly inaccurate. They also have to be mounted so they dangle, and that can make them even harder to read in turbulence or during maneuvering. I'd stick with the classic unit.
Click to expand...

Finally, someone agrees with me about this! I don't like them because they block your view out the windshield (my Cherokee has a panel-mounted whiskey compass that doesn't block the windshield at all). I guess if I already had a center post mounted compass AND it developed a leak, I might replace it with a VCC. Otherwise, I can think of better ways to spend $300.
 
gprellwitz said:
Kenny, Steve didn't write that; he attributed it to Avionics West of TN.
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Oops.. sorry about that. I had read through it and was just thinking of him as the source. Thanks, Grant.

Tell me if I'm wrong, though. The impression from the writing is they were mounted right on the glare shield rather at the top of the windscreen.
 
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