Main; Flushing Hydraulic System; Hydraulic System Operational Checks Using Piper Test Unit; Hydraulic Test Unit (Optional) - Piper Cheyenne IIIA Airplane Maintenance Manual

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. Main
1. Flushing Hydraulic System.
When hydraulic system is contaminated, drain and flush entire system to remove contaminated
fluid. Determine cause and type of contamination and proceed as follows:
(a) Remove engine cowlings (refer to 71-10-00).
(b) Disconnect hydraulic lines at engine driven pumps.
(c) Drain hydraulic fluid from power pack reservoir using suction, fill, and drain fitting on bracket
located at lower aft comer of nose access panel opening behind hydraulics components cover.
(d) Disconnect hydraulic lines at actuating cylinders and drain fluid from all hydraulic lines.
(e) Remove and replace filter elements located on engine firewall. Flush out filter bowls.
(f) Flush hydraulic system with clean hydraulic fluid (MIL-H-5606). Examine several seals and
cylinder bores for damage.
(g) When hydraulic system is completely flushed and no indication of contamination exists,
reconnect previously disconnected fittings and replenish system with clean hydraulic fluid.
(h) Bleed hydraulic system (described in Bleeding the Hydraulic System) and check for leaks.
(i) Replace engine cowlings (refer to 71-10-00).
2. Hydraulic System Operational Checks Using Piper Test Unit.
The test unit (P/N 753 080) can be used to check hydraulic systems, the hydraulic power pack
landing gear cycling operation, power pack operating pressure checks and adjustments etc, all
performed without operating engines.
The unit consists of an electric, motor driven hydraulic pump, bypass valve, fluid reservoir, filter,
pressure gauge, hoses, and adapter fittings housed in a metal cabinet and mounted on casters.
3. Hydraulic Test Unit (Optional).
Multi-purpose hydraulic test units can also be used to provide the same functions as the Piper unit.
The test unit must be capable of duplicating and monitoring the operating pressures and the flow
rate given in 29-00-00, Chart 2.
NOTE: The following procedures are written for Piper or optional hydraulic test units. Use proper
operating manual for specific unit being used.
4. Connecting Test Unit.
(a) Remove access panel on right side of nose section. Open access in hydraulics components
cover.
(b) If system requires filling only, remove protective cap from suction; fill and drain valve mounted
on bracket on lower aft comer of nose access panel opening. Connect pressure hose from test
unit. Open valve on suction port, place control lever in up position, and proceed to fill system
per instructions with test unit. Observe fill lines so not to overfill reservoir.
(c) If system is to be operated during various ground checks, overhaul, or inspection of
components, remove protective caps from suction and pressure ports, connect test unit
pressure hose to pressure port and test unit suction hose to suction port. Open valve on
suction port and operate test unit according to supplied instructions.
EFFECTIVITY:
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29-10-00
Jan
10/90