The International Cessna^® 170 Association

Hello All
My AN style Direction Gyro was wandering. I sent it to KC for rebuild and reinstalled. It still wanders. They will check it out for me but before I send it back i want to know if there is something I should be doing first.
It is plumbed exactly like the Cessna parts book shows except that I am using a 8" venturi and I have filtered air going the back of the D/G and the Artificial Horizon.
I am showing 5" vacuum at cruise and don't usually climb above 2500 feet. I have all the proper fittings and 3/8 hose to the vacuum source.
I removed the filtered air and the fittings and now have 5.75" vacuum and no change.

Dick Bryant
N2704C
Plymouth MA

Don’t know what you men by “wandering” but I suspect it may be precession and that may be due to a poor re-build.

Also don’t know who “KC” is… but I highly recommend “Aircraft Quality Instruments” in Wichita for gyro repair: http://flyaqi.com/

I am sorry.
AQI did the rebuild in KS not KC.

Dick

Perhaps the problem is your running to much vacuum, An AN gyro was designed to be run on 3" of vacuum hence they are able to be used nicely with a 4" venturi vacuum system. I'd check with the overhauler for their opinion.

It’s Sunday, Bruce…. you’re probably thinking of a 3-1/8” gyro…. AN gyros are expecting 3.5” vacuum….. 3-1/8” gyros expect 4.5” vacuum.
But in any case, that is a design minimum…. not a maximum….and the 5” he’s experiencing should operate either type. (In fact, my AN types work perfectly even at “high” altitude (10K+) where less than 3.5” occur on my system because (I suspect) they are already spooled up.

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