MD-11 Flight Crew Operations Manual
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Hydraulics Chapter Hyd
Description and Operation Section 10
Hyd.10.1
Hyd.10 Hydraulics-Description and Operation
General
Three hydraulic systems provide power to operate nose gear steering, landing
gear, wheel brakes, and flight controls.
Hydraulic pressure for each system is provided by two engine-driven pumps.
Three separate, parallel hydraulic systems operate continuously at 3000 psi. Each
system includes an identical 12-gallon capacity hydraulic reservoir. Each
reservoir can be filled from a pressurized ground service unit or from an
unpressurized container by use of a hand pump near the fill panel.
Two electrically-driven auxiliary pumps provide an additional source of pressure
to hydraulic system 3. If the Air-driven Generator (ADG) is deployed, it powers
auxiliary pump 1.
Two hydraulic Reversible Motor Pumps (RMP) provide an alternate source of
hydraulic pressure. One RMP is installed between systems 1 and 3, and the other
is installed between systems 2 and 3.
Two Non-reversible Motor Pumps (NRMP) provide an alternate source of
hydraulic pressure to the rudders and stabilizer trim.
Three bladder-type accumulators in each brake system provide a backup source of
hydraulic pressure, and partial antiskid capability if the hydraulic system
malfunctions. Pressure gauges are installed on each accumulator.
A BRAKE PRESS indicator, on the cockpit brake control panel, allows
verification of brake pressure for aircraft towing.
Heat generated in the engine-driven pumps carries through the case drain lines to
the reservoirs and back through the suction lines to the engine-driven pumps. This
serves as the main heat radiating system. The entire pressure and return network
is a secondary heat radiating system.
Switches on the HYD control panel control hydraulic components and
annunciators. Hydraulic system indications are displayed on the System Display
(SD) when the hydraulic synoptic is selected with the HYD cue switch. Hydraulic
alerts are displayed on the Engine And Alert Display (EAD) and SD.
Hydraulic System Controller
The Hydraulic System Controller (HSC) has two modes, auto or manual. Only one
mode is in control at any time.
October 02, 2006
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