CHAPTER 12

HYDRAULIC POWER

Page

TABLE OF CONTENTS 12-00-01/02

DESCRIPTION

General 12-10-01

Description 12-10-01

Controls and Indicators 12-10-02

COMPONENTS

Hydraulic System Block Diagram 12-20-01/02

CONTROLS AND INDICATORS 12-30-01

FUNCTIONAL SCHEMATICS

Hydraulic System 12-40-01/02

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HYDRAULIC POWER

GENERAL

The hydraulic power system consists of three,parallel, continuously pressurized systems.Each system is powered by two engine-drivenhydraulic pumps. Additionally, two electricalauxiliary pumps are provided in system 3.Emergency hydraulic power is available fromone of these auxiliary pumps when poweredby the air-driven generator (ADG). Two,reversible motor-pumps can transfer powerfrom an operating to an unpressurized systemin the event of engine failure, and two, non-reversible motor-pumps will provide transferof power to certain components of the flightcontrol system.

DESCRIPTION

ENGINE-DRIVEN PUMPS

Each of the three engines has a left and righthydraulic pump to pressurize the three, nor-mally independent, hydraulic systems. Thesesystems power the flight controls, horizontalstabilizer, landing gear, brakes, and nose-wheel steering. The pumps are normally con-trolled by individual switches on the FlightEngineer's Panel. A fire shutoff valve in eachsystem controls the fluid supply to both pumpsof the associated engine. If electrical controlpower for any pump is interrupted, that pumpwill remain operational, or will start automat-ically if previously turned OFF.

AUXILIARY PUMPS

Two electrical auxiliary hydraulic pumps inhydraulic system 3 are primarily for grounduse with the engines shut down. The auxiliarypumps can be individually controlled from theFlight Engineer's station or simultaneouslycontrolled by a switch on the Pilot's OverheadPanel. Additionally, auxiliary hydraulic pump1 can be used as an emergency pressuresource for the flight controls. In the eventof loss of all three engines, the ADG can bedeployed to provide electrical power directlyto one auxiliary pump.

REVERSIBLE MOTOR-PUMPS

The reversible motor-pumps are installed totransfer pressure from an operating hydraulicsystem to an unpressurized hydraulic system(1-3 and 2-3). Pressure can be transferred ineither direction. No fluid transfer takes place,the transfer of energy is mechanical. Controlswitches for these pumps are on the FlightEngineer's panel. If the fluid in the reservoirof either the operating system or the systembeing pressurized falls below a preset mini-mum, that motor-pump combination will au-tomatically stop operating.

NON-REVERSIBLE MOTOR-PUMPS

Two, non-reversible motor-pumps providetransfer of hydraulic pressure from one systemto another to power the lower rudder, upper

JLSep 1/91 12-10-01

rudder, and horizontal stabilizer. The non-reversible motor-pumps may be deactivatedby moving the RUDDER STBY PWR switch toOFF. For a detailed description and func-tional diagram of these components, refer toFlight Controls, Chapter 9.

HYDRAULIC SYSTEMENHANCEMENT

Hydraulic system enhancement consists of amotor operated shutoff valve and check valvein system 3. This maintains integrity if thereis an uncontained failure of engine 2. Thesystem uses reservoir level sensing to detectfast or slow leakage, and automaticallyshuts off the system 3 elevators and 3-2

non-reversible motor pump when the fluid inthe reservoir reaches a predetermined level.Enough fluid in system 3 remains for pitch androll through use of horizontal stabilizer trimand lateral controls powered by system 3. AHYD SYS 3 ELEV OFF light in the cockpit willcome on when the shutoff valve is closed.

CONTROLS AND INDICATORS

Controls, indicators, and annunciator lightsare on the Flight Engineer's Upper Panel No.2 and No. 3, Overhead Panel, and Glare-shield. Illustrations of these major panels arein Chapter 1. Individual controls and indica-tors are illustrated and described in anothersection of this chapter.

12-10-02JL

Sep 1/91

HYDRAULIC SYSTEM - Controls and Indicators

Motor PUMP Switch (1-3) (2-3)OFF — Depressunzes pump output Can

be overridden by auto-slat extendsignal

ON — Mechanical ly in terconnectsapplicable systems to transferpressure from one system to theother in event of loss of pressurein one system

ARM—Will pressurize associated motorpumps(s) if any engine N2 speeddrops below 45%, or an auto-slatextend signal is present

Note Regardless of switch position,motor pumps are turned on when AutoSlat extension system is activated

TEMP HI Lights (6)Indicate above normal temperature atrespective engine driven pump Will alsocause MASTER CAUTION and HYD cuelights to come on

ENG HYD PUMP Switch (1, 2, 3, L)

ON — Pump provides pressure tosystem

OFF — Depressunzes pump output ifelectrical power is available

Hydraulic TEMP Gage (3)Indicates temperature of fluid in hydraulicreservoir in degrees centigrade Pointermoves to a position below zero if elec-trical power fails

HYD PRESS Gage (3)Displays pressure in respective hydraulicsystem Pointer moves to zero if electricalpower fails A system operating fromengine driven pumps may display slightlydifferent pressures from a systemoperated by motor pumps due todifferences in pump characteristics

PRESS LO lights (6)Indicate low pressure at respectiveengine-driven pump Will also cause allMASTER CAUTION and HYD cue lightsto come on Low pressure switch willturn on PRESS LO light when outputpressure of respective engine drivenhydraulic pump is not sufficient to powerthe system PRESS LO light(s) will notcome on for a respective pump in AUTOcontrol unless that pump does not res-pond to a demand for pressure

ENG HYD PUMP Switch (1, 2, 3, R)

AUTO—Pump provides pressure tosystem only when systempressure decay takes placeWhen system pressure isrestored, the "on-demand 'pump will automatically returnto an EDV, ( e l e c t r i c a l l ydepressunzed) condition

ON — Pump provides pressure tosystem

OFF — Depressunzes pump output ifelectrical power is available

HYD QTY Gage (3)Indicates fluid quantity in hydraulic reservoir Should be read when system ispressurized Indicator needle remainsstationary if electrical power fails Resetbugs to quantity indicated Chevron markon gage indicates minimum recommended hydraulic quantity for preflight Whenquantity is less than approximately onegallon a low level switch disables theassociated motor pump(s)

NOTEOn aircraft with SB 29-128 the minimumquantity chevron will be at 5 25 gallons onthe system 3 gage

FLIGHT ENGINEER'S UPPER PANEL NO 3

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HYDRAULIC SYSTEM - Controls and Indicators

AUX PUMP 2 Switch

Both positions of the switch are momentary.

START - Aux pump 2 is turned on supplying pres-sure to hydraulic system 3.

STOP - Momentarily placing switch to STOP posi-tion will deenergize auxiliary pump 2.

AUX PUMP 1(ADG) Switch

Both positions of the switch are momentary.

START - Aux pump 1 is turned on supplying pressureto hydraulic system 3.

STOP - Momentarily placing switch to STOP posi-tion will deenergize auxiliary pump 1.

HYD FIT CONTROL Lights

The 1-3 PUMP switch, 2-3 PUMP switch, and SYS 3switch are used for maintenance ground-test functions.If one or more lights are on during cockpit preparationthey should be turned off by pushing associated light.

ADG Switch

R EMERELEC - Right emergency bus is energized when

the ADG is deployed.

HYD - Switch is normally in HYD position. WhenADG is deployed, auxiliary pump 1 is pow-ered and pressurizes hydraulic system 3.Both motor pumps are also disabled.

AUX HYD PUMPS Switch

START - Momentarily placing switch to the STARTposition and releasing will start auxiliary 1(ADG) and auxiliary pump 2. Auxiliary hy-draulic pumps are normally used for cock-pit preparation and maintenance checks.

STOP - Momentarily placing switch to STOP willdeenergize both auxiliary hydraulic pumps.

AUX HYD PUMPS ON Light

Indicates that auxiliary pump 1 (ADG) and/or auxiliarypump 2 has been activated.

FLIGHT ENGINEER'SUPPER PANEL NO. 2

OVERHEAD PANEL

1-3/2-3 PUMP VALVE OPEN light effective on aircraftwith SB 29-109 or production equivalent.

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Jun 1/97

HYDRAULIC SYSTEM - Controls and Indicators

1-3/2-3 PUMP VALVE OPEN Light

Indicates that motor pump 1-3 and/or 2-3 isolationvalve(s) is in transit and/or open.

AUX HYD PUMP ON Light (1,2)

Indicates that auxiliary pump 1 and/or 2 have beenturned on.

HYD FILTER PRESS HI Light

Warns of an impending filter clog and/or pump discrep-ancy. Low fluid temperature may also cause light tocome on.

NOTES

1. installed in system 2 with SB 29-103 or productionequivalent.

2. Installed in all 3 systems with SB 29-110 or produc-tion equivalent.

3. Removed with SB 29-125 or production equivalent.

4. Removed and replaced with a HYD SYS 3 ELEV OFFlight with SB 29-128. See below.

HYD SYS 3 ELEV OFF Light

Comes on when the elevator shut off valve in hydraulicsystem 3 is closed. MASTER CAUTION light illuminateson airplanes with SB 29-132 installed.

INSTALLED ON AIRPLANES WITH SB 29-128.

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HYDRAULIC SYSTEM

NOTES1 HYD FILTER PRESS HI light installed in hydraulic system 2

only with SB 29 103 or production equivalent2 HYD FILTER PRESS HI light installed in systems 1 2 and

3 (illustrated) with SB 29 110 or production equivalent3 HYD FILTER PRESS HI light is removed with SB 29 125 or

production equivalent4 SB 29 128 ncorporation (ill strated) results in the following

HYD FILTER PRESS HI light is removedElevator control electric shutoff valve is installedCheck valve is installedHYD SYS 3 ELEV OFF light is installedMinimum quantity chevron on HYD QTY gage is movedfrom 3 75 gallons to 5 25 gallons

1-3/2-3 PUMP VALVE OPEN light effective on aircraftwith SB 29-109 or production equivalent.

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