For Sovereign Aircraft Only - Changing MIL-H-5606 or MIL-PRF-83282 Fluid in Hydraulic Power Units to

**Document as reference only provided by Tronair. For up to date procedures, please request document from manufacturer.

Changing MIL-H-5606 or MIL-PRF-83282 Fluid in Hydraulic Power Units to MIL-PRF-87257

1. Remove cap from reservoir drain assembly and open drain valve to remove fluid from reservoir.

2. Remove plug fitting in lower portion of the cooler to drain fluid from cooler.

3. Remove and drain pressure filter bowl.

4. Drain return filter assembly:

a. Remove element from filter assembly and either:

i. Suck fluid from filter bowl or,

ii. Remove top panel from unit and unscrew filter bowl from assembly and drain.

5. Return unit to running condition using original filter elements.

6. Replace fittings and close valve at the bottom of the reservoir.

7. Remove existing fittings from the pressure and return hoses.

8 Connect external pressure hose to external return hoses using a union (contact Tronair for available kit), open the pressure and return ball valves on the back of the unit.


9. Add minimum amount of new fluid to unit reservoir.

10. Set reservoir selector valve to the HPU position.

11. Open by-pass valve and start unit.

12. Open flow control valve to 1⁄2 maximum flow position, adjust pressure control to minimum necessary to maintain flow.

13. Close by-pass valve (make sure ball valves on back of unit are open) and allow fluid to cycle for 30 minutes.

14. Shut down unit and repeat draining procedure (go to step 1).

15. Replace filter elements with new elements.

16. Install Tronair KHC-3766 Coupling Kit on pressure and return hoses.

17. Change labels on unit to reflect the new fluid type.

18. Service unit reservoir (do not exceed maximum level).

19. Refer to operation manual for bleeding procedure to eliminate trapped air from system.

20. Send a fluid sample for evaluation ( flash.html), if acceptable; unit is ready to return to service.

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