Panel Mounted Whiskey Compass
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Panel Mounted Whiskey Compass
Can anyone provide a mfg and part number for the panel mounted compass in the 170B??? Appreciate any help I can get. Regards, Chuck
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zero.one.victor
- Posts: 2271
- Joined: Tue Apr 23, 2002 12:11 am
Seems like a vertical-card compass would be easier to work with than a whiskey compass,especially if you didn't have a (vertical-card) DG. I've thought many times about installing one,but I've had several people tell me that they're junk. I see that Spruce sells a cheapie ($185) as well as a spendier one ($255),the spendier one is TSO'd.
I usually use the compass (track) feature on my GPS to set my DG,don't have to do any corrections for course but do have to reset it every time I make a major change in direction if there's much wind aloft.
Being a VFR kinda guy,I often forget to set the DG at all til I'm in the pattern at my destination!
Eric
I usually use the compass (track) feature on my GPS to set my DG,don't have to do any corrections for course but do have to reset it every time I make a major change in direction if there's much wind aloft.
Being a VFR kinda guy,I often forget to set the DG at all til I'm in the pattern at my destination!
Eric
John, I think you'll be disappointed in the vertical card compasses. They have a very high failure rate. They are non-liquid dampened and as such they are constructed with an internal spindle-mount that becomes easily jarred off-center. They then hang up, and jam with extraordinary loss of sensitivity. Many times the mere act of installing them causes them to fail. Turbulence will always make you wonder and lose confidence in it.
On top of which, all the cool things you once knew about magnetic compass behavior (and subsequently forgot) will become moot.
(A-N-D-S, Accelerate-North, Decelerate-South,....and T-V-M-D-C, "True-Virgins-Make-Dull-Companions". Well, maybe that second one doesn't become moot, but you get the idea!)
If you want to make the little numbers behind the lubber-line move to the right....then make a right turn. To make 'em move left, ...turn left. That's all you gotta remember.
The reason you have a Directional Gyro is to get past the "bouncy" and momentary-opposite swing behavior of the magnetic compass. But if you'll go back and re-study mag compass behavior, and learn to use those idiosyncrasies to your advantage,....there'll be still one more cool reason you fly vintage/classic taildraggers and ordinary people don't/can't qualify!
On top of which, all the cool things you once knew about magnetic compass behavior (and subsequently forgot) will become moot.
(A-N-D-S, Accelerate-North, Decelerate-South,....and T-V-M-D-C, "True-Virgins-Make-Dull-Companions". Well, maybe that second one doesn't become moot, but you get the idea!)
If you want to make the little numbers behind the lubber-line move to the right....then make a right turn. To make 'em move left, ...turn left. That's all you gotta remember.
The reason you have a Directional Gyro is to get past the "bouncy" and momentary-opposite swing behavior of the magnetic compass. But if you'll go back and re-study mag compass behavior, and learn to use those idiosyncrasies to your advantage,....there'll be still one more cool reason you fly vintage/classic taildraggers and ordinary people don't/can't qualify!
Perhaps it depends upon the brand of vertical card compass that matters with regard to the failures. All of our CRJs have the vertical card unit, and I have not seen one fail in the last five years. Not saying one has not failed, but I have never seen one written up in the MX log and never heard any of the mechanics or pilots talking of a vertical card compass failure. I suppose I need to find out the manufacturer of the unit. I have not normally paid any attention to the compass in the plane since FMS is installed, but now I've been looking at it a lot to see how it behaves. I do notice the hangups in the turns, but upon rolling out to near wings level, the vertical unit always comes quickly around and stabilizes nicely.
Of course keeping the wet compass would be cheaper. What is the proper fluid level in a wet compass? I can see the top of the fluid in my glass window. I always thought it a bit low. I do know the unit needs to be swung. It is 20 degrees off while facing north or south, but seems close when on an easterly or westerly heading. I suppose taking the little plate off of the bottom will expose the adjustment screws
Of course keeping the wet compass would be cheaper. What is the proper fluid level in a wet compass? I can see the top of the fluid in my glass window. I always thought it a bit low. I do know the unit needs to be swung. It is 20 degrees off while facing north or south, but seems close when on an easterly or westerly heading. I suppose taking the little plate off of the bottom will expose the adjustment screws
John, 2734C in Summit Point, WV
You can purchase compass repair kits and fluid from San-Val, Spruce, etc. There are basically only four items needed. The paper window-gasket, the rubber window-gasket, the rubber rear-diaphragm, and the fluid. A small screwdriver and a clean plastic tupperware or glass bowl about 5 inches deep are the only necessary tools.
Take your compass apart carefully by removing the front and rear screws. Remove the window gaskets (inner rubber and outer paper) and the rubber diaphragm. Replace the window gaskets with new. Submerge the compass face-down in the bowl of fluid, and gently rock it about to dislodge any trapped air-bubbles. Insert the diaphragm into the fluid and turn it upside down under the fluid to release trapped air. (The diaphragm is installed convex side out to provide maximum fluid capacity inside the compass.) Attach the rear cover, again being careful to release any trapped air. Remove the compass from the bowl, and set it on newspaper to let it dry out a few hours. (Or VERY gently blow it dry with compressed air. Don't stress that rear diaphragm.)
Strain the excess, unused fluid thru a coffee filter to return it to it's storage can. Save it for any future need. (The gaskets are cheap. It's the fluid that costs $10 or so per qt.)
Re-install the compass. Twist any compass lite wiring as if it were safety wire, to nuetralize any stray DC electric current from influencing the compass when your instrument lighting is used.
Point the aircraft North with all electrics except landing lites on and engine runnning. Adjust BOTH adj. screws to the nuetral position (Small dot on screw even with small dot on case.) Notice the error.
Point the aircraft South, and adjust out ONE-HALF of the error using the NS screw. Point the aircraft East and note the error. Point it West and adjust out ONE-HALF the observed error.
Point the aircraft North, and adjust out 1/2 the error again. Confirm that South heading is within 1/2 of the error just removed during the last Northerly adjustment. Point East and adjust out 1/2 the error. Point West and confirm that any observed error is 1/2 or less of the observed Easterly error.
Confirm all cardinal points around the compass (each 30 degrees) read within 1/2 of the largest observed error and create a compass correction card. (If any errors exist larger than 7 degrees, you should try to determine if any stray objects are lying about, or you probably have stray magnetism in the aircraft to locate and nuetralize by degaussing or lead insulation sheets.) An official airport compass "rose" is the proper place to swing a compass.
Take your compass apart carefully by removing the front and rear screws. Remove the window gaskets (inner rubber and outer paper) and the rubber diaphragm. Replace the window gaskets with new. Submerge the compass face-down in the bowl of fluid, and gently rock it about to dislodge any trapped air-bubbles. Insert the diaphragm into the fluid and turn it upside down under the fluid to release trapped air. (The diaphragm is installed convex side out to provide maximum fluid capacity inside the compass.) Attach the rear cover, again being careful to release any trapped air. Remove the compass from the bowl, and set it on newspaper to let it dry out a few hours. (Or VERY gently blow it dry with compressed air. Don't stress that rear diaphragm.)
Strain the excess, unused fluid thru a coffee filter to return it to it's storage can. Save it for any future need. (The gaskets are cheap. It's the fluid that costs $10 or so per qt.)
Re-install the compass. Twist any compass lite wiring as if it were safety wire, to nuetralize any stray DC electric current from influencing the compass when your instrument lighting is used.
Point the aircraft North with all electrics except landing lites on and engine runnning. Adjust BOTH adj. screws to the nuetral position (Small dot on screw even with small dot on case.) Notice the error.
Point the aircraft South, and adjust out ONE-HALF of the error using the NS screw. Point the aircraft East and note the error. Point it West and adjust out ONE-HALF the observed error.
Point the aircraft North, and adjust out 1/2 the error again. Confirm that South heading is within 1/2 of the error just removed during the last Northerly adjustment. Point East and adjust out 1/2 the error. Point West and confirm that any observed error is 1/2 or less of the observed Easterly error.
Confirm all cardinal points around the compass (each 30 degrees) read within 1/2 of the largest observed error and create a compass correction card. (If any errors exist larger than 7 degrees, you should try to determine if any stray objects are lying about, or you probably have stray magnetism in the aircraft to locate and nuetralize by degaussing or lead insulation sheets.) An official airport compass "rose" is the proper place to swing a compass.
ALL HAIL GEORGE! Mighty man of C170 mechanical mystery 
Thanks to your urgings, I am going to service my wet compass and give it one more chance to fly right. I suppose the vertical card units do so well in the jet because they are not tossed around on a regular basis with low level flying, and the vibration is much less as well. I'll let you know how the servicing went. 
Thanks to your urgings, I am going to service my wet compass and give it one more chance to fly right. I suppose the vertical card units do so well in the jet because they are not tossed around on a regular basis with low level flying, and the vibration is much less as well. I'll let you know how the servicing went. John, 2734C in Summit Point, WV
One more tip on swinging your compass: Do so with the controls held in the nuetral position, as that is the position at which they spend most of their time inflight. Aircraft with panel-mounted wet-compasses sometimes will show deviations with the controls placed at their extreme travel. (But when you are inflight with the controls in that extreme position #1) it's unlikely you are trying to hold a constant heading and #2) whatever your compass is reading inflight when the flight controls are at their extreme limits is not going to be what holds your attention.
Another few tips about servicing your compass:
When you remove the front cover, before removing the window, examine the glass very carefully. Notice it is actually "bevelled" glass. Also notice that the upper edge is longer than the lower edge. Make certain you reinstall it correctly. (Also handle it carefully, as it is brittle glass. If you get heavy with a screwdriver trying to pry it loose from an old stuck rubber gasket you may chip or break it.)
When you adjust/swing your compass, (this should be obvious, but....) use a non-magnetic screwdriver such as plastic or brass. You can make one out of simple heavy-gauge copper or brass wire or brazing rod by simply bending one end into a loop for a handle, and smashing the other end flat with a hammer. Check to make certain the alloy used does not influence the compass.
Lastly: This type of repair is only supposed to be undertaken on certificated aircraft by a properly licensed/certificated instrument shop. A logbook entry must only be entered into the logs by such an authorized person. I cannot seem to find any such entry's anywhere in my logs so my own compass must never have had any problems.
Another few tips about servicing your compass:
When you remove the front cover, before removing the window, examine the glass very carefully. Notice it is actually "bevelled" glass. Also notice that the upper edge is longer than the lower edge. Make certain you reinstall it correctly. (Also handle it carefully, as it is brittle glass. If you get heavy with a screwdriver trying to pry it loose from an old stuck rubber gasket you may chip or break it.)
When you adjust/swing your compass, (this should be obvious, but....) use a non-magnetic screwdriver such as plastic or brass. You can make one out of simple heavy-gauge copper or brass wire or brazing rod by simply bending one end into a loop for a handle, and smashing the other end flat with a hammer. Check to make certain the alloy used does not influence the compass.
Lastly: This type of repair is only supposed to be undertaken on certificated aircraft by a properly licensed/certificated instrument shop. A logbook entry must only be entered into the logs by such an authorized person. I cannot seem to find any such entry's anywhere in my logs so my own compass must never have had any problems.