KLM MD-11 - Reservoirs and Accumulators; Engine-Driven Pumps

MD-11 Flight Crew Operations Manual
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Hydraulics -
Description and Operation
Hyd.10.2
If an active HSC channel fails, control is automatically transferred to an alternate
HSC channel. Should the second HSC channel fail, the system automatically
reverts to the manual mode, and the crew manually operates the hydraulic system
for the remainder of the flight.
In the auto mode the HSC performs the following functions:
• Controls the hydraulic system components which supply and route
hydraulic pressure.
• Monitors the phase of flight and configures components accordingly.
• Conducts a preflight pressure test of the auxiliary hydraulic pumps and
RMPs when initiated by the flight crew.
• Conducts a test of engine-driven hydraulic pumps after engine start.
• Reconfigures the hydraulic systems for various component, system, and
aircraft failures.
• Monitors itself and hydraulic components for proper operation and reports
faults to the Centralized Fault Display System (CFDS) and EIS.
• Reverts to manual mode if the auto mode is inoperative or if any
combination of hydraulic system, and/or aircraft abnormal operation
requires more than four engine-driven hydraulic pumps to be commanded
off.
Reservoirs and Accumulators
Identical pressurized reservoirs are provided for each system. Mounted on each
reservoir is a fluid quantity transmitter, low level switch, fluid temperature sensor,
and a pressure relief valve. The 12-gallon reservoir is normally serviced to about
6 gallons. Each hydraulic system has a bladder-type accumulator to store
pressurized fluid. After engine shutdown, reservoir pressure is maintained for
about 8 hours.
Engine-Driven Pumps
Left and right engine-driven hydraulic pumps are mounted on the accessory drive
for each engine. The left pump normally powers its respective system. The right
pump is armed to operate if the left pump pressure drops below a predetermined
value. The left pump low pressure switch electrically commands the right pump
on. When the left pump pressure rises above a predetermined value, the right
pump is electrically armed after 20 seconds. The HSC monitors the right pump
and commands the right pump on or armed if it does not automatically respond to
the electrical commands given by the left pump pressure switch.
The pump FAULT light on the HYD control panel illuminates if pump pressure is
low and the pump is on, or if pump case drain temperature is high.
October 02, 2006