787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Hydraulics -
System Description
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 13.20.3
There are certain airplane failure modes which require one or more of the demand
pumps, left, right or center to load shed to allow the electrical system to provide
power to other systems. The indication is LOAD SHED showing on the hydraulic
synoptic next to the demand pump symbol.
Ram Air Turbine (RAT)
The RAT, when deployed, provides 5000 psi hydraulic power to the primary flight
controls connected to the center hydraulic system. The RAT provides hydraulic
and electrical power throughout the flight envelope. (Refer to Ram Air Turbine
(RAT) Generator in Chapter 6, Section 20, for additional information.) In flight,
the RAT deploys automatically if any of the following occur:
• both engines have failed
• all three hydraulic system pressures are low
• loss of all electrical power to captain’s and first officer’s flight instruments
• loss of all four EMPs and faults in the flight control system occur on
approach
• loss of all four EMPs and an engine fails on takeoff or landing
The RAT can be deployed manually by pushing the RAM AIR TURBINE switch
on the hydraulic panel. A spring-loaded actuator is used to deploy the RAT either
automatically or manually. Once deployed, the RAT cannot be stowed in flight.
August 14, 2009
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