12-33 Drain and Flush
NOTE
Drain and flush hydraulic system if oil turns dark or emits bad
odor.
WARNING
Keep limbs clear of flight controls when operating test pump.
Hydraulic forces can cause injury.
1. Refer to Figure 12-4. Remove filler-vent plug. Place a suitable drain container under
F902-1 (pressure) and F902-2 (suction) line assembly T-fittings, and remove caps.
Pour small amount of new A257-15 fluid into hydraulic reservoir to purge suction line.
Pressure line will drain in following step, when D516-1 cap is removed.
2. Replace filter per Section 12-32.
3. Connect MT384 (or equivalent) 0.8-1.2 gpm hydraulic test pump assembly to T-fittings.
(Pressure and suction fittings are different sizes to ensure correct connection.)
4. Service hydraulic reservoir per Section 12-31.
5. Disconnect D205-18 hose assembly (return) from reservoir. Place line into drain
container; cap union with a T-fitting cap.
6. Activate test pump and inspect hydraulic system for leaks.
7. Simultaneously fully raise collective and move cyclic fully forward then simultaneously
fully lower collective and move cyclic fully aft. Monitor reservoir fluid level and fill as
required. Repeat procedure until return line fluid is clean.
8. Simultaneously fully raise collective and move cyclic fully aft then simultaneously fully
lower collective and move cyclic fully forward. Monitor reservoir fluid level and fill as
required. Repeat procedure until return line fluid is clean.
9. Turn off test pump and disconnect equipment. Remove cap and connect hose assembly
(return) to reservoir. Using back-up wrench, standard torque hose nut per Section 20-
32 and torque stripe per Figure 5-1. Install caps on T-fittings, special torque caps per
Section 20-33, and torque stripe per Figure 5-1.
10. Bleed hydraulic system per Section 12-34.
11. Remove cap and filter and visually inspect element for contaminants. If debris is found,
repeat drain and flush procedure. If filter is clean, install filter & cap and special torque
cap per Section 20-33.
12. Service hydraulic reservoir per Section 12-31.
SEP 2012 R66 Maintenance Manual Chapter 12 Servicing Page 12.11
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