TM 1-4920-446-13 & P
1-13. Electric Motor. Power is supplied by a 20 horsepower, 220/440 volt, 3-phase, 60 hertz, electric motor (Figure 1-2
and Figure 1-5).
1-14. Hydraulic Hoses. Three hydraulic hoses are provided with the test stand. The 1/2 and 3/4 inch diameter hoses
connect the high pressure system to the aircraft hydraulic system. The 1 inch diameter hose is the suction return line
from the aircraft. Each hose has a quick disconnect fitting protected by a dust cap on each end. Each hose connects to
the applicable quick disconnect fitting mounted on the rear of the frame. When not in use, the hoses can be stored on
hooks on the front of the cabinet.
1-15. Electrical Cable Assembly. The external cable is approximately 56 feet long. It has a female plug on one end to
plug into a hangar or flight line electrical receptacle. The 6 wires at the other end attach to the test stand electrical sys-
1-16. Hydraulic Pump . The hydraulic pump is a high pressure, variable stroke, variable pressure, axial piston type.
It includes a pressure compensator and handwheel stroke control. The rotation is clockwise (facing the input shaft),
1800 rpm, and output of 10 gpm at 3, 000 psi, and 5 gpm at 5, 000 psi. It incorporates a 1/4 inch needle valve for pres-
sure compensator shutoff. Pressure and volume adjustments may be fixed at any point within the range of 800 to 5, 000
psi and 0 to 10 gpm. The pump mounting bracket attaches the pump to the electric motor. A removable panel on the
bracket allows access to the flexible coupling attached to the motor output and pump input shafts.
1-17. Hydraulic Reservoir.
a. The hydraulic reservoir stores hydraulic fluid (MIL-H-83282) and supplies it for test stand functions. The reser-
voir holds 22 gallons of hydraulic fluid, 20 of which are usable. A 3 gallon space above the normal full level allows for
expansion. A bolted access plate on top allows reservoir clean out and incorporates the fill tube with removable cap. An
electrical float type fluid level assembly is installed in the reservoir. It's connected to a fluid level gauge on the instru-
b. The reservoir can be removed by lifting off the cabinet, draining the tank, disconnecting plumbing and wiring, and
removing 4 bolts.
1-18. High Pressure Filter. A filter (Figure 1-2) is located in the high pressure output line. A micronic filter element
within the filter gives the pressurized fluid a final cleaning before outlet to the aircraft. A warning light on the operator's
control panel indicates high differential pressure between the filter inlet and outlet. Should a filter element become
clogged, the warning light will come on.
1-19. Low Pressure Filter. A low pressure filter (Figure 1-2) is incorporated in the outlet line from the system boost
pump. The filter cleans hydraulic fluid before it enters the high pressure pump section. The filter housing' incorporates a
drain plug, a filling port, and an air bleed valve which can be opened (using a screwdriver) to release entrapped air.
1-20. Protective Devices and Instrumentation (Figures 1-3 and 1-4).
a. A thermal relief valve limits pressure in the low pressure section caused by thermal expansion of fluid.