(7)
When completing operation, check that pump switch is in ON position.
NOTE: The engine-driven pump should be left in the ON position after maintenance has been performed. This will help to prolong the life of the depressurization solenoid which becomes energized when the pump switch is placed in the OFF position.
(8)
Close ground interconnect valve and disconnect electrical power.
(9)
Remove ground lock from nose gear if maintenance is complete.
D. Pressurize Hydraulic System A (System A Engine-Driven Pump)
CAUTION: DO NOT OPERATE SYSTEM A PUMPS MORE THAN 2 MINUTES UNLESS THE NO. 1 FUEL TANK CONTAINS AT LEAST 1675 LBS/760 KG OF FUEL. IF PUMPS ARE OPERATED 2 MINUTES WITHOUT FUEL IN TANK, ALLOW RESERVOIR TO RETURN TO AMBIENT TEMPERATURE BEFORE RESUMING TEST.
(1)
Install ground lock assembly in nose gear.
(2)
If engine run is required to pressurize hydraulic system, using engine No. 1 or 2 (Ref Chapter 71-00, Power Plant - General).
(3)
If pressurization can be accomplished by motoring engine, refer to 71-09-100, Power Plant (JT8D) - Operating Procedures.
(4)
Remove ground lock from nose gear if maintenance is complete.
3. Depressurize Hydraulic System A
A. Shut off source of hydraulic power and wait 5 to 10 minutes to allow system pressure to dissipate through internal leakage to the return system.
B. Depressurize reservoir if any lines are being opened (Ref 29-09-30 MP).
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4. Flush Hydraulic System A
A. General
(1)
The following procedure is provided to flush the hydraulic system after replacement of a failed engine-driven hydraulic pump.
(2)
If, following this procedure, severe contamination is suspected due to a collapsed filter element, the case drain filter element should again be replaced after 1 week of normal operation. After 2 months of operation, all system filter elements should be replaced.
(3)
If fluid contamination exists from a chemical source, the fluid and filter elements should be replaced in accordance with 29-00 MP.
(4)
Whenever hydraulic system components are disassembled, cleaned, overhauled or installed, flushing with BMS 3-11 hydraulic fluid only is recommended to avoid fluid contamination within the operational system by incompatible materials.
WARNING: FIRE-RESISTANT HYDRAULIC FLUIDS CONFORMING TO BMS 3-11 MAY CAUSE SKIN IRRITATION. AVOID PROLONGED OR REPEATED CONTACT WITH SKIN. IN CASE OF EYE CONTACT, FLUSH EYES WITH WATER AND OBTAIN MEDICAL AID. IN CASE OF INGESTION, OBTAIN MEDICAL AID.
B. Flush Hydraulic System
(1)
Depressurize hydraulic system A.
(2)
Replace applicable case drain filter element (Ref 29-11-41, Unit Servicing).
(3)
Replace applicable system A pressure filter element (Ref 29-11-71, Unit Servicing).
(4)
Replace system A return filter elements (Ref 29-11-111, Unit Servicing).
(5)
Pressurize hydraulic system A using engine-driven pump (Ref par. 2.C.).
(6)
Cycle all hydraulic subsystems (except landing gear) at least six times at maximum rate.
(7)
Replace applicable case drain filter element and system A pressure filter element with clean elements.
(8)
Restore system to normal configuration.
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HYDRAULIC SYSTEM A - INSPECTION/CHECK
1. Hydraulic System A Check
A. Check Hydraulic System A Tubing
(1) Check hydraulic tubing in the nacelle area for discoloration which indicates overheating of hydraulic fluid. The tubing is accessible by raising the applicable engine cowl panels.
B. Check Hydraulic System A Filters
(1)
At regular intervals replace or clean system A case drain filter element. During removal, inspect magnetic plug and filter element for contamination.
NOTE: If paper filter element is used, examine for contamination by cutting the element and laying the paper out flat.
(2)
If excessive amount of metal particles are found in the case drain filter proceed with the following steps:
(a)
Remove and overhaul the associated pump.
(b)
Clean case drain filter bowl and replace element. See 29-11-41, System A Hydraulic Pump Case Drain Filter.
(c)
Check system pressure and return filters.
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