Central Gyro Filter Replacement

[FLYFST]

Any procedural advice on replacing the Central Gyro Filter?  On my 1990 M20J it is a Rapco RA-D9-18-1 that has just a few hours left on the recommended 500 hr replacement cycle.  It is the alternate installation in the Service Manual (MAN123, Figure 37-1) located inside the instrument panel on the pilot's side and appears to be very difficult to get to from the top of the instrument panel.  Advice on how much to tighten would also be great as the Service Manual (MAN123, Section 37-13-04) only says don't over tighten.

thanks in advance - Hank

Edited July 2, 2022 by FLYFST
Additional details

[Guest]

There should be a 3/8" nut in the engine compartment that holds the filter to the aft side of the firewall.  The filter should have a bushing inside it to prevent collapsing between the two end caps for the filter.

Clarence 

[EricJ]

If you think any of your gyro instruments may need service soon and the system isn't giving you any trouble right now, perhaps think about deferring the replacement unless/until you need to overhaul one of the gyro instruments.    The only reason for saying that is that some overhaul shops (repair stations) won't warranty an overhaul unless the filter is replaced when the overhauled instrument is installed.   So if you replace the filter now and need to do an overhaul in the near future, you may just need to replace it again.

 

[Fly Boomer]

6 hours ago, FLYFST said:

It is the alternate installation in the Service Manual

My eyes are not what they used to be (or anything else for that matter), but I'm not seeing a substantive difference between the "regular" mounting and the "alternate".  What is the difference?

[FLYFST]

Regular has one filter attached to the back of the AI and in my case HSI, while the alternate has a single filter attached to the firewall and to which each instrument connects. The alternate configuration is shown on the lower right corner of the diagram.

All the best -Hank


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[FLYFST]

There should be a 3/8" nut in the engine compartment that holds the filter to the aft side of the firewall.  The filter should have a bushing inside it to prevent collapsing between the two end caps for the filter.
Clarence 

Thanks Clarence, that helps. Any recommendations on how tight to turn the nut and avoid crushing the filter? The shop that last installed mine had it finger tight at best.
Hank


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[FLYFST]

If you think any of your gyro instruments may need service soon and the system isn't giving you any trouble right now, perhaps think about deferring the replacement unless/until you need to overhaul one of the gyro instruments.
 

Thanks EricJ. No clear problem that I can point to. However, in a discussion with AutoPilotsCentral they mentioned making sure to change that filter on the 500 hr schedule as it can be the hidden cause of gyro problems.
Hank


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[Fly Boomer]

11 minutes ago, FLYFST said:

Regular has one filter attached to the back of the AI and in my case HSI, while the alternate has a single filter attached to the firewall and to which each instrument connects.

Got it.  I was misreading the diagram.  Thanks!