The International Cessna^® 170 Association

The AN type DG in my plane looks like it has two vacuum ports. One is capped off with a pipe fitting. I would like to relocate the vacuum hose to the other side (port). Can you pull vacuum from either port? I can't tell if there are any marking on it.

I think the other side is vacuum to pull another instrument so they are in series.
If I remember right, my old Sperry DG was in series with the T&B.

There should be some marking on it.

I finally got a picture under the panel. I see there is an air inlet port on the back of the DG. (Shouldn't this has some sort of filter?)

I would like to move the vacuum hose to the left port and move the plug to the right. Would this be ok?

It MIGHT be ok. Air is sucked into or pushed into the outlet. That stream of air in is directed over a veined flywheel which is spun up. You have identified the inlet and you have identified one possible outlet where your vacuum hose is attached. If the other pipe plug opens to the same area as your current vacuum hose then it would seem either one of the sides could be used. You could remove the plug and see if you can tell if both plug bosses open to the same area. You could as someone who has the exact same gauge which I realize your trying to do or you could try it.

Here is a Youtube video of a gyro being run. DON'T do what this guy is doing.
https://youtu.be/2MA5_Gm_gsc

In the old days gyros of this type typically all had their own filter built into the inlet. And so it was not uncommon to not see a common filter as we do today. Looks like this one does not have an inlet filter. Yes the air entering it should be filtered for longevity of the gauge and anything up stream.

Pull that bowling ball out of the panel and get back some useful load

If you take them apart, they make really cool desk art.

nippaero wrote:I finally got a picture under the panel. I see there is an air inlet port on the back of the DG. (Shouldn't this has some sort of filter?)

I would like to move the vacuum hose to the left port and move the plug to the right. Would this be ok?

Yes, you can do this. Also that air inlet on the back normally has a round replaceable screen filter under that cover. If that filter is not in there, you should then have some kind of external filter.

Thanks Bruce. I am going to switch them and see what happens. I bet that inlet port has a lot of junk in the built in filter.

bagarre wrote:Pull that bowling ball out of the panel and get back some useful load

Lol, the thought has crossed my mind!