MD-11 Flight Crew Operations Manual
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Hydraulics -
Description and Operation
Hyd.10.3
In manual, the pilot commands the left pump on or off, and the right pump armed
or off. In auto, the HSC commands the left pump on or off, and the right pump
armed, on, or off.
Engine-driven pumps are interchangeable.
Electric Auxiliary Pumps
Two electrically-driven auxiliary pumps, installed in system 3, are used to
pressurize system 3 on the ground or in flight. These pumps also pressurize system
1 via the 1-3 RMP, and system 2 via the 2-3 RMP.
In an emergency, auxiliary pump 1 is automatically controlled and powered by a
deployed ADG. The ADG remains in the hydraulic mode unless the ADG/ELEC
switch on the ELEC control panel is pushed.
The flight crew controls the auxiliary pumps with the HSC in auto or manual
mode.
When either auxiliary pump is commanded on, the recirculation fans are
automatically commanded off. When the auxiliary pumps are commanded off, the
recirculating fans are automatically commanded back on.
Reversible Motor Pumps
Two Reversible Motor Pumps (RMP) allow transfer of pressure from an operating
hydraulic system to a non-operating hydraulic system. Pressure is transferred in
either direction. No fluid transfer takes place. The transfer of energy is
mechanical. RMPs are installed between systems 1-3, and between 2-3. The
RMPs pressurize a system to 3,000 psi in about 3 seconds when driven by a fully
pressurized system. A pressure differential between the connected systems causes
pumping direction reversal. If there is no flow demand, the delivery from the
pump stops.
The RMPs are commanded off when:
• The reservoir fluid quantity on either side of the RMP is less than 1
gallon.
• The ADG is deployed and ADG/ELEC switch on the ELEC control panel
is not illuminated.
Both RMPs are commanded on at automatic slat extend and when any engine N2
rpm is less than 45 percent during taxi or takeoff/land flight phases.
In the manual mode the RMPs are manually commanded on or off. In the auto
mode the RMPs are commanded on or off by the HSC.
October 02, 2006
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