DG Precession

[TheTurtle]

My DG seems to "suck" according to my instructor   it precesses pretty fast.   I was looking at overhaul vs repair vs getting one that has a heading bug.

I have an edo-aire DG now.  no heading bug.  Looking at spruce etc the prices seem to jump from the $400-$500 range for a replacement and then jump to $1200+ for a heading bug as they seem to all slave to an autopilot.  I dont think Ill ever need that since my autopilot which is currently inop has a direction setter on it.  Anybody seen one thats just a dumb bug?

Then I thought hey maybe ill do an HSI and slave it to my KNS80.  WOW  $6000.  so yea.... no. 

second why is there this T thing on the back of the DG?  I was hoping it was leaking at the fitting although I have good vacuum according to my suction gauge and warning light not being on.

[Browncbr1]

When does in error?  If you are doing approaches and going around in the pattern a lot, then that is normal. Accelerating and climbing after a stabilized approach usually gives me 20 degrees or so error Ina matter if just a few seconds after missing.   Especially if your turning while climbing back out.   If it holds pretty good in level flight at stable speed, then it should be fine.  

 

If if there are wires going to that fitting, then it is a suction switch that will turn your vac light on.  

Edited December 3, 2016 by Browncbr1

[TheTurtle]

i have been doing mostly approaches and other hood work which makes it much more noticable but it seems to slip a lot in straight and level as well. 

No wires to that fitting.  they go behind it to lights.

[XXX]

Here is a DG with heading bug, non-autopilot. You would think it would be less than one that has an autopilot pick-up.

I'm doing instrument training as well and I think the heading bug is a big help. It might be worth the extra expense if you will be flying approaches in the soup.

http://www.chiefaircraft.com/rca-11d-7.html

[Bob - S50]

If you are talking big money, and your autopilot is inop, there is a complete used KFC200 for sale on Beechtalk for $3900.

KFC200 $3900

[geoffb]

That looks like my alt static source valve.  No idea why something like that would be attached to a vacuum line.  Unless the picture is showing the back of your VSI, in which case it makes perfect sense.

[geoffb]

One other thing, when I still had the original, bent, instrument panel my DG had significant precession.  Sent it to TGH for checkout and they said it was fine.  The problem was that it was a 0 degree unit and the angle of the lower panel was causing trouble.  Not that I have a flat panel in, it's much better.

[mooniac15u]

On 12/2/2016 at 8:30 PM, TheTurtle said:

My DG seems to "suck" according to my instructor   it precesses pretty fast.   I was looking at overhaul vs repair vs getting one that has a heading bug.

I have an edo-aire DG now.  no heading bug.  Looking at spruce etc the prices seem to jump from the $400-$500 range for a replacement and then jump to $1200+ for a heading bug as they seem to all slave to an autopilot.  I dont think Ill ever need that since my autopilot which is currently inop has a direction setter on it.  Anybody seen one thats just a dumb bug?

Then I thought hey maybe ill do an HSI and slave it to my KNS80.  WOW  $6000.  so yea.... no. 

second why is there this T thing on the back of the DG?  I was hoping it was leaking at the fitting although I have good vacuum according to my suction gauge and warning light not being on.

It looks like some kind of relief valve or pressure switch.  Is it connected to that white wire?  It's hard to tell from the photo.

[N201MKTurbo]

Are you sure you are looking at your DG?

That tubing is too small for vacuum lines. And the way it is plumbed it looks like your static lines. Are you sure you Are not looking at your VSI?

[TheTurtle]

Just now, N201MKTurbo said:

Are you sure you are looking at your DG?

That tubing is too small for vacuum lines. And the way it is plumbed it looks like your static lines. Are you sure you Are not looking at your VSI?

its not unlikely lol.  Going back to the hangar today, ill verify my pics. 

[Guest]

On December 2, 2016 at 8:30 PM, TheTurtle said:

My DG seems to "suck" according to my instructor   it precesses pretty fast.   I was looking at overhaul vs repair vs getting one that has a heading bug.

I have an edo-aire DG now.  no heading bug.  Looking at spruce etc the prices seem to jump from the $400-$500 range for a replacement and then jump to $1200+ for a heading bug as they seem to all slave to an autopilot.  I dont think Ill ever need that since my autopilot which is currently inop has a direction setter on it.  Anybody seen one thats just a dumb bug?

Then I thought hey maybe ill do an HSI and slave it to my KNS80.  WOW  $6000.  so yea.... no. 

second why is there this T thing on the back of the DG?  I was hoping it was leaking at the fitting although I have good vacuum according to my suction gauge and warning light not being on.

That is your alternate static valve and should be on the back of the VSI.  It's shown in some of the older parts books.

Clarence

[TheTurtle]

ok thats embarassing.  It IS on the back of the VSI.  I was working on that at the same time. Speaking of which....  The VSI was showing a 300foot decent when standing still.  I adjusted the screw to set the needle back to 0.  Flew it and the needle decided +300foot was its new 0..  I readjusted it today back to 0.  Any suggestions on whats up with that?  Turning the screw to adjust the needle was very tight.

Attached is a pic of the back of the DG.  Looks like somebody didnt use a hose clamp on the vacuum hose.  Ill cross my fingers and clamp that and hope it slows the precession down some.

 

 

[Browncbr1]

The vacuum gauge switch looks to be hooked up directly to your DG behind the blue vac line fitting in that photo.  So, if your gauge or lights are normal, then the DG is getting normal vacuum.  

Edited December 11, 2016 by Browncbr1

[TheTurtle]

Just now, Browncbr1 said:

The vacuum gauge switch is hooked up directly to your DG in that photo.  So, if your gauge or lights are normal, then the DG is getting normal vacuum.  

yep gauge show 5.5 in cruise.  I was doing some straight and level yesterday and the DG just slips way to fast.  And my compass badly needs swinging so its  double cluster.  Im under the hood with dumb gauges building hours and resetting the dg against a wonky compass is interesting. Its going in for annual this month so Im going to either replace or overhaul the DG and replace the whisky compass with a card style. 

[Browncbr1]

Yea, if you have good auction and the DG goes off a bunch during straight and level, I would send it in.  I set by DG maybe once every 20 minutes when in cruise.  And the adjustment is less than 5 degrees.  

When I am going missed and turning to an option heading, I got in the habit of looking at GPS track until I complete the turn, then reset DG.  That usually gets me pretty close.  You could also do a timed turn

[Sean S]

This happened to my DG Saturday night. Out for overhaul, be back in two weeks.

IMG_4171.MOV

[Marauder]

9 hours ago, Bayern Speed said:

This happened to my DG Saturday night. Out for overhaul, be back in two weeks.

IMG_4171.MOV

That's not precession, that is Bermuda Triangle stuff.

[Sean S]

8 hours ago, Marauder said:

That's not precession, that is Bermuda Triangle stuff.

Good news is it lasted 41 years, original DG to the aircraft!

[TheTurtle]

On 12/5/2016 at 5:10 PM, M20Doc said:

That is your alternate static valve and should be on the back of the VSI.  It's shown in some of the older parts books.

Clarence

I was thinking about this yesterday as I was studying for IR written.  or instead of studying I should say.. 

If thats the alternate static valve and you are in hard imc and getting knocked around and your static ports freeze over or whatever; you have to dig up behind your panel hopefully not grabbing a handful of rats nest wires, and spin or pull that thing?  Seems like a terrible place to put it.  From another thread on MS it doesnt look like this was factory?   

[cnoe]

I was thinking about this yesterday as I was studying for IR written.  or instead of studying I should say.. 
If thats the alternate static valve and you are in hard imc and getting knocked around and your static ports freeze over or whatever; you have to dig up behind your panel hopefully not grabbing a handful of rats nest wires, and spin or pull that thing?  Seems like a terrible place to put it.  From another thread on MS it doesnt look like this was factory?   

In the case of blocked static a good choice is to break the glass lens of your VSI.

Also, it's common for the vacuum lines on your DG and AI to not have hose clamps.


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[Guest]

6 hours ago, TheTurtle said:

I was thinking about this yesterday as I was studying for IR written.  or instead of studying I should say.. 

If thats the alternate static valve and you are in hard imc and getting knocked around and your static ports freeze over or whatever; you have to dig up behind your panel hopefully not grabbing a handful of rats nest wires, and spin or pull that thing?  Seems like a terrible place to put it.  From another thread on MS it doesnt look like this was factory?   

To operate the valve you push it up, opening it. There is no reason in my mind that you could not install the valve form a newer model in your plane.

Clarence