Purpose. The D5 hydraulic test stand is
designed to fill or flush the aircraft hydraulic system with
micronically-filtered hydraulic oil. It also tests the
aircraft hydraulic systems and provides hydraulic
pressure for testing the systems without running the
Principles of operation. The hydraulic
fluid may be taken from either the test stand reservoir or
the reservoir in the aircraft being tested, through the
suction inlet. Once obtained, the hydraulic fluid is then
forced under pressure by the high pressure pump to the
selected pressure outlet, and then through one of the
external hoses to the aircraft. Fluid is returned to the
test stand through either the 1/2 or 3/4 inch outlet,
depending upon the outlet selector valve setting, or
through the one-inch return line. There is complete
instrumentation on the control panel to indicate
hydraulic pressure, suction pressure, hydraulic reservoir
level, and fluid temperature. The test stand can deliver
hydraulic fluid at the rate of 10 gpm at pressures up to
3,000 psi and, with reduced flow, 5 gpm or less at
pressure from 3,000 to 5,000 psi.
Safety practices and procedures. The
following special precautions should be observed when
using the hydraulic test stand:
· Unpressurize the test stand before
disconnecting or connecting any hoses or
· Do not stand downwind of and close to the
· Be aware of the hazards associated with a
fluid in a hose at high pressures.
· Avoid contamination in both the test stand
and the aircraft systems by servicing from
a previously unopened can that has been
applicable maintenance manual for detailed instructions.
The following general procedures pertain to the
operation of the D5 hydraulic test stand:
Maneuver the test stand into a
suitable position for hose connection.
Apply the handbrake.
Start the gasoline engine and allow
it to warm up for about 10 minutes.
Connect the hoses to the aircraft.
Select either test stand reservoir or
aircraft reservoir as the source of hydraulic fluid.
Apply pressure, perform the task,
and monitor the control panel.
shutdown and stop the test stand.
inspections should be made before using the D5
hydraulic test stand.
Fuel tank and hydraulic reservoir.
Check fluid levels and refill as required.
Control panel. Check for security of
handles and free movement of controls. Push press-to-
test indicators; replace indicator lamp if necessary.
Engine. Check oil level.
Battery. Check electrolyte level.
Trailer. Check tire pressure. Check
handbrakes lever for proper operation.
Maintenance. Consult the applicable
maintenance manual for scheduled and preventive
Aircraft jacks. Aircraft jacks consist essentially
of a pump assembly, a cylinder and ram
assembly, and a base assembly. Depending on
the design and lifting capacity of the jacks, the
base assembly can be flat or a tripod style,
mounted on casters.
Purpose. Aircraft jacks are designed to
raise the entire aircraft or a specific portion of the
aircraft so that maintenance can be performed. Jacks
come related with different lifting capacities, ranging
from 3 tons to over 25 tons.
Principles of operation. A generalized
jack hydraulic schematic diagram is shown in figure 9-6.
The pump handle is moved up and down to raise the
cylinder and rams. On the up stroke of the pump
handle, the pump piston draws hydraulic fluid from the
reservoir. On the down stroke, the piston pushes the
hydraulic fluid under pressure through the spring-loaded