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Joined: Mon May 28, 2001 11:30 am

Overhauling Gyros And Other Avionics Questions

Sun May 02, 2004 10:22 am

I am the member of a flying club that has had a difficult time with overhauled gyros. We have used 3 different shops in the last five years, and each time the product that comes back has been substandard. We have three aircraft, 1 1973 182 and 2 1976 172's, and we are looking into once again changing gyro shops.

Do any of you have any recommendations as to what gyro shop will offer a good overhauling job on gyros? We occasionally get luckly, and a turn coordinator or attitude indicator will last a year or so, but often we get the gyro back from the shop and it will work a few weeks and then it will fail.

Our policy is that we have an extra gyro (both turn coordinator and attitude indicator), so we always have one on the shelf that is able to be put in an airplane should one fail. However, as soon as we get a gyro back from the shop, we immediately put it in the plane to make sure it will work until the warranty expires (often it won't).

On another note, does anyone have any ideas where to get an Cessna/ARC IN-346A ADF indicator (just the indicator itself, no associated radio)? Any avionics "chop shops" that you could point me too?

If any of you have any suggestions at all, it would be great. I'm sorry if this isn't the type of post that is expected in Tech/Ops, but a lot of you have a wealth of GA experience to offer.

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Joined: Tue Nov 09, 1999 6:20 pm

RE: Overhauling Gyros And Other Avionics Questions

Sun May 02, 2004 1:44 pm

We don't use overhauled gyros for that very reason. New ones aren't that much more expensive (~$800 as opposed to ~$600 for the last DG we did), and we've found that overhauled ones generally suck too. We decided that going with new ones would save money in the long run.

We also have decided to ditch the ADFs over a slow upgrade path to GNS 430s. Also, it's my experience that airplanes with the older style ADF antenna (with the wire from the vertical stab to the top of the cabin) seem to work better than the "all in one" antenna on the bottom of the fuselage. Regardless, of our 4 airplanes that had ADFs, only two of them worked (both have the older style antennas). One of those still works quite well, the other works somewhat decently. One of the ones that didn't work we replaced with a GNS 430, and the other works for about a week after we get it fixed and then sucks again (newer style antenna). Mostly we've given up on the damn ADFs.

The plane we put the 430 in is flying a LOT more now, though some of that is probably due to the fact that its avionics absolutely sucked before the upgrade (the 430 wasn't the only upgrade).
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RE: Overhauling Gyros And Other Avionics Questions

Sun May 02, 2004 6:17 pm

The "all in one" antenna is called a goiniometer... Dont know if the spelling is correct, but I always get good reception with the ones on the UND planes...
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RE: Overhauling Gyros And Other Avionics Questions

Sun May 02, 2004 9:17 pm

The "all in one" antenna is called a goiniometer... Dont know if the spelling is correct, but I always get good reception with the ones on the UND planes...

Not quite....a goniometer is the older style ADF indicator. The "all-in-one" antenna is just called a "combined loop". Both goniometer based and newer SIN/COS driven ADF systems can use combined loops although that they are not available for all models. Other ADF systems that you typically find in airliners (older ones) have the goniometer built into the remote unit and repeat the ADF bearing on an RMI via a synchro interface.

GNS 430s are just fine and dandy, but they can't teach you how to perform an NDB approach. So I still consider an ADF essential for navigation training, and for if you are flying to an airport that has no published GPS or other approaches. (Yes they still exist)

Not to mention you can't listen to AM stations on a GNS 430...

With respect to gyros, overhauled units can be just fine. My experience though is that you need to find a shop as close by as possible. The damage typically gets done in the shipping and handling so the closer the better.

Also, use very good packing. The bigger the better. A box 5 or 6 times the width of the gyro is not outrageous. And cushion it well with very pliable material. Shipping? First class with all as many Fragile stickers that will fit on the box. Don't let your gyro languish on a truck for a week as it makes its way to you across the country.

You may want to also ask your repair station about the bearings they use. Many US shops are using aftermarket bearings that we here in Canada consider "bogus parts". Many Canadian shops have been fighting Transport Canada for policy that would allow them to use these much cheaper bearings citing unfair advantage. But I hope they lose the fight. If your instrument shop uses these bearings, you may want to ask them to provide you with a warranty and honor it if their overhauled crap quits prematurely.

If you are experiencing failures on air driven gyros, you may also want to check the pneumatic pressure on your airplanes. Many many many airplanes run with pressure well outside (higher or lower) than prescribed. It has to be pretty much dead on to promote gyro longevity.

Do you store your gyros on a hard shelf? The act of placing a gyro on a wooden shelf can subject the unit to forces well above its design limits. Gently placing it on concrete is about 100 times worse. Line your gyro shelf with a piece of foam rubber and train your technicians to REALLY treat gyros like eggs. They don't write that on gyros just for kicks.

One last thing, have your shop begin the practice of shipping gyros with one of those impact stickers. You can even place it on the unit yourself before you ship it for overhaul. If you receive it without a sticker or if it indicates an impact...send it back.

[Edited 2004-05-02 14:18:50]
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RE: Overhauling Gyros And Other Avionics Questions

Tue May 04, 2004 12:18 am

email me through my profile
I may be able to help
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533

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