TM 1-1520-238-23
7-14.8
Change 9
7.3A.
RE-BLEED PRIMARY AND/OR UTILITY HYDRAULIC SUBSYSTEMS – continued
e. Re-bleed Auxiliary Power Unit (APU) and start motor.
NOTE
Method I is the optimum method for re-bleeding.
(1) Upon completion of steps 1 through 10 and APU run, purge circuit. Repeat steps 1 through 6 (bypass
step 7 if actuators are not articulated) and complete steps 8 through 10.
NOTE
Method II is an alternate method for re-bleeding hydraulic components.
(2) If using Method II, upon completion of steps 1 through 10, repeat step 5. Leave aircraft power on (use
external power if battery becomes run down.
(3) Verify that aircraft’s utility accumulator pressure is Zero (0) (Ignore nitrogen pre-charge) and that utility
manifold level is “within the green” or greater. Do not discharge air.
(4) Verify APU is serviced with lubricating oil (item TBD, App H) and that intake/exhaust areas are clear for
rotation.
(5) Select APU RUN/SELECT switch to RUN only.
(6) Pull out APU FIRE PULL handle and verify that boost pump stops operating and fuel shutoff valve
closes.
(7) Ensure that APU exhaust is clear of personnel, then select APU RUN/START switch to START.
(8) Operate aircraft hand pump and view turbine rotation through exhaust. Rotation should occur within
two to three strokes and synchronize with pump operation. Operate pump for minimum of 30 cycles.
CAUTION
GSU must not be used to bleed the Auxiliary Power Unit (APU) start motor circuit. Equip-
ment damage can result.
(9) Select APU RUN/START switch to OFF and push in FIRE PULL handle, then shut down aircraft
electrical power.
(10) Connect GSU pressure and return hoses to utility GSE panel. Start GSU and set pressure to 3000 + or
-200 psig.
(11) Service utility manifold to correct fluid level (mid-green). Service manifold with additional air to deplete
fluid, if required. Wait for utility accumulator gauge to stabilize at 3000 + or -200 psig.
(12) Set GSU pressure to 0 and shut down. Remove GSU pressure and return hoses from utility GSE panel.
(13) Re-install dust caps/plugs to panel and hoses, Stow GSU.
END OF TASK
