Noticed a slight noise from the backup AI

[bradp]

Hi All,

I noticed a slightly different hum than I was used to as my once primary now backup AI was spinning down.  Seems to erect within about 10 seconds of the vacuum working.

I suppose that, if this is an indication of needing an overhaul in the near future, I'll have two options:

1- send the unit it as-is. If so who are current recommended shops for attitude indicator overhaul?

2- replace the AI with an electrically driven one.  Given I have a PFD with a 4hr battery, I might be comfortable with this approach (vs keeping the vacuum system).  I could get rid of the vacuum system entirely if I put the G5 that interfaces to the autopilot and ditch the DG as well.  Anyone gone the electric AI driving an old century autopilot route?

Thanks!

Brad

[MIm20c]

Does your old AI connect to the AP at all?

[bradp]

Yes it's an attitude autopilot 

[Bob - S50]

4 minutes ago, bradp said:

Yes it's an attitude autopilot 

Not sure, but I don't think your plan 2 will work.  I assume your PFD is Aspen.  The G5 is not approved as a backup, only a primary AI.  Also, I'm pretty sure (almost positive) that it currently cannot send attitude information to a legacy autopilot.  The G5 HSI version can send data to your autopilot for navigation, but not for attitude.  A Sandia 340 might be a legal backup but I don't think it can send info to your autopilot either.

Does Aspen make a converter that will drive your model of autopilot?  If so, you could do that, then buy a non-vacuum ADI as a backup and pull the vacuum system.

You might be stuck with your vacuum driven AI until you have other autopilot options.  Hopefully before too long you'll be able to replace yours with either a Trio or Trutrack and then put that Sandia 340 in (if legal) as your backup.  Then you can pull the vacuum system.  With luck, you might be able to sell some of the other parts to help offset the cost.

[N201MKTurbo]

FWIW

Attitude gyros can get pretty bad before they cause any real problems. They only truly fail when the precession exceeds the ability of the erection system to keep them erect. 

If it is just starting to get noisy on shutdown with no other symptoms it probably has a few hundred more hours in it. 

I would just wait for your next maintenance event where the plane will be down for a while and send it out then, instead of taking the plane out of service just to fix the autopilot attitude source.

[bradp]

43 minutes ago, Bob - S50 said:

Not sure, but I don't think your plan 2 will work.  I assume your PFD is Aspen.  The G5 is not approved as a backup, only a primary AI.  Also, I'm pretty sure (almost positive) that it currently cannot send attitude information to a legacy autopilot.  The G5 HSI version can send data to your autopilot for navigation, but not for attitude.  A Sandia 340 might be a legal backup but I don't think it can send info to your autopilot either.

Does Aspen make a converter that will drive your model of autopilot?  If so, you could do that, then buy a non-vacuum ADI as a backup and pull the vacuum system.

You might be stuck with your vacuum driven AI until you have other autopilot options.  Hopefully before too long you'll be able to replace yours with either a Trio or Trutrack and then put that Sandia 340 in (if legal) as your backup.  Then you can pull the vacuum system.  With luck, you might be able to sell some of the other parts to help offset the cost.

Yes Bob - I'll still need a gyro based AI with an autopilot output even if I do dual G5's.  I was wondering whether if it does need to be replaced whether I could do something like a castleberry life saver electric mechanical gyro attitude indicator with an autopilot output if it the indicator fails. 

12 minutes ago, N201MKTurbo said:

FWIW

Attitude gyros can get pretty bad before they cause any real problems. They only truly fail when the precession exceeds the ability of the erection system to keep them erect. 

If it is just starting to get noisy on shutdown with no other symptoms it probably has a few hundred more hours in it. 

I would just wait for your next maintenance event where the plane will be down for a while and send it out then, instead of taking the plane out of service just to fix the autopilot attitude source.

Cool turbo that's good to know.  Thanks.

 

[MIm20c]

I know the lifesaver gyro is lacking AI outputs. Not sure about the other one you mentioned.