Navion hydraulic filter change parts and process

[billla]

NOTES: This information is provided for evaluation by the reader as they see fit. All aircraft service should be completed in compliance with applicable aircraft references and FAA regulations. 14 CFR Part 43 does not address this service as “Preventive Maintenance”.

Introduction
The Navion hydraulic system is one of the more complex aspects of the aircraft but is also trouble-free if maintained in good working order. A clean supply of hydraulic fluid can be guaranteed by regularly replacing the fluid and filter. The Navion Service Manual provides only that during “periodic inspection” to “Remove hydraulic fluid reservoir filter, and check for clogging. Replace with new filter if necessary.” Given the low cost of the maintenance, the relative ease of the service, and the importance of the hydraulic system to safe aircraft operation this maintenance should be completed at annual inspection.

Part Numbers
NOTE: Plane Parts, Inc. (https://www.planepartsinc.com/) sells kit PPHRK1 with all required parts. This section will be better formatted shortly.

Part | Qty. | P/N | Notes
Hydraulic Filter | 1 | P73 | https://www.baldwinfiltersrus.com/baldw ... andle.html
Hydraulic back-up ring | 1 | 8-342 |Replaces 145-58236 Gasket - Hydraulic Reservoir Cover as noted on factory drawing.
Tube fitting boss gasket | 2 |MS28778-8
O-ring | 1 | MS28775- 008
Aircraft 10-32 bolt | 1 | AN3-61A Bolt |Replace as req’d.

NOTE: Owners have reported using automotive or other filters in place of the Baldwin P73 filter specified in the Navion Parts Manual, including the NAPA Gold 1071 or 1080, AC Delco PF-316, or FRAM C-134PL. The specified filter is still readily and inexpensively available; care should be taken making substitutions.

Process
General guidance for hydraulic system maintenance is provided in 12.1 HYDRAULIC SYSTEM in the Navion Service Manual. Also reference Figure 33 Hydraulic Reservoir to ensure correct placement of O-rings and seals as well as the filter itself.

1. Carefully remove line to the 90 degree elbow in the reservoir cover.
2. Remove the reservoir cover by removing the center bolt and set aside.
3. Using a fluid vacuum gun or other pump, remove all the fluid from the reservoir.
4. Carefully remove all components from the reservoir, using Figure 33 to ensure ALL components are removed. Finding "extra" o-rings or seals is not uncommon due to careless prior service.
5. Inspect the interior of reservoir for corrosion or other issues, wipe clean including the top lip.
6. Clean and inspect all components, then lightly lubricate with hydraulic fluid.
7. Replace all components, referring to Figure 33. DO NOT over-tighten the center bolt.
8. Re-attach the line to the 90 degree elbow.
9. Refill the reservoir with AN3580-compatible hydraulic fluid being very careful not to over-fill.
10. Carefully clean up any excess hydraulic fluid.
11. Cycle the flaps using the hand pump twice and verify correct operation.
12. Inspect reservoir carefully for leaks.

Corrections/additions/suggestions for this process are welcome!

[Hal]

Current hydraulic fluid is 5606. Changing filter and fluid once every 5 years is often enough.
Hal

[billla]

Thanks, Hal - what do you base that timeline on?

[ErichR]

Hal,

Where do you drain the fluid at? (To get it all out) And how do you replace it? (Mule or just filling the reservoir back up?)

I was wondering if there was a good flush procedure on this as mine hasn't been changed in 30+ years

~Erich

[Hal]

Bill, 5 year change interval is based on 59 years of owning many Navions (Bought and sold aircraft at our FBO, specialized in Navions).

Erich, Probably a better way, but disconnecting lines at low point and letting drain is one way. Brake systems seem to be the only hydraulics where the oil gets really nasty. Otherwise, just remove filter and clean out reservoir.
Hal

[MartyHill]

I've got an old NAvion inspection checklist that puts the hyd filter in the 500hr service interval.

[billla]

Marty, is it directly from North American or Ryan?

I hear the wisdom and experience for the longer change interval, and as I noted the NAA/Ryan documentation simply notes "periodic" inspection and filter replacement "if necessary". It's obviously the decision of the A&P in terms of what's required.