B767 ATA 29 Student Book
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Transcript of B767 ATA 29 Student Book
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B767-3S2F ATA 29-00Page - 1 11/7/13 EFF - ALL
HYDRAULIC POWER
CH 29
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ATA 29 HYDRAULIC POWER TABLE OF CONTENTS:
HYDRAULIC POWER TABLE OF CONTENTS.....................................2
INTRODUCTION ................................................................................... 4
HYDRAULIC SYSYTEMS ..................................................................... 6
SERVICING........................................................................................... 8
GROUND POWER CONNECTIONS................................................... 10
PRESSURE TRANSMITTER LOCATIONS......................................... 12
FLIGHT COMPARTMENT CONTROLS & INDICATIONS .................. 14
QUANTITY INDICATING SYSTEM..................................................... 16
RESERVOIR TEMPERATURE INDICATING...................................... 18
HEAT EXCHANGER ........................................................................... 20
TYPICAL LEFT / RIGHT HYDRAULIC FLOW DIAGRAM................... 22
LEFT / RIGHT SYSTEM COMPONENT LOCATIONS........................ 24
ENGINE DRIVEN PUMP (EDP) LEFT & RIGHT CONTROL .............. 26
EDP CONTROL - LEFT AND RIGHT SYSTEM .................................. 28
EDP SUPPLY SHUTOFF VALVE - LEFT & RIGHT SYSTEMS.......... 30
ALTERNATING CURRENT MOTOR PUMP (ACMP) ......................... 32
L / R ACMP CONTROL - PRESSURE AND OVERHEAT IND............ 34
CENTER SYSTEM DIAGRAM ............................................................ 36CENTER SYSTEM COMPONENTS ................................................... 38
CENTER SYSTEM ACMP ELECTRICAL CONTROL......................... 40
AUTOMATIC ISOLATION OF ACMP NUMBER 1 .............................. 42
AIR DRIVEN PUMP (ADP) COMPONENTS ....................................... 44
ADP CONTROL LOGIC....................................................................... 46
ADP OPERATION............................................................................... 48
RAM AIR TURBINE (RAT) .................................................................. 50
RAT OPERATION ............................................................................... 52
RAT CONTROL LOGIC....................................................................... 54
POWER TRANSFORMER UNIT (PTU) STAB TRIM .......................... 56
PTU SYSTEM...................................................................................... 58
PTU CONTROL LOGIC....................................................................... 60
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STUDENT NOTES:
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INTRODUCTION
Location
The three hydraulic systems are identified by location. They are the left, center,
and right systems.
The left system is located in the left engine strut and contains approximately 17
gallons of hydraulic fluid.
The center system is located in or near the right main wheel well and contains
approximately 40 gallons of fluid.
The right system is located in the right engine strut and contains approximately
20 gallons of hydraulic fluid. This equates to a total capacity of approximately
77 gallons.
Multiple Systems
The three systems - left, center, and right - have no interconnection. They are
color-coded on their tubing runs for ease of identification:
Left = Red
Center = Blue
Right = Green
Multiple Pressure Sources
Two Engine Driven Hydraulic Pumps (EDP) are used, one on each engine.
These are primary pumps in the left and right systems.
Four Alternating Current Motor Pumps (ACMP) are used. Two serve as primary
pumps in the center system, while one each serves as the demand pump in the
left and right systems.
An Air Driven Pump (ADP) is the demand pump in the center system. Air power
comes from the airplane pneumatic system, which in turn may be supplied by
engine bleed, APU or a ground source such as an air cart.
A Ram Air Turbine (RAT) pump in the center system which serves as an
emergency source of hydraulic pressure is powered by the slipstream.
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INTRODUCTION
COLOR CODE - RED
RESERVOIR, FILTERS(IN HYDRAULIC BAY IN STRUT)
LEFT SYSTEM
ONE EDPONE ACMP
RIGHT SYSTEM
COLOR CODE - GREEN
RESERVOIR, FILTERS
(IN HYDRAULIC BAY IN STRUT)
ONE EDPONE ACMP
CENTER SYSTEM
COLOR CODE - BLUE
ONE RATRESERVOIR, FILTERS
TWO ACMPONE ADP
(IN OR NEAR RIGHT MAIN WHEEL WELL)
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HYDRAULIC SYSTEMS
General
Each of the three separate hydraulic systems operates with an approximate
pressure of 3000 PSI. Any of the acceptable BMS 3-11, type IV fluids such asSkydrol may be used.
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HYDRAULIC SYSTEMS
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SERVICING
Location
The reservoir service station is located in the right-hand aft body fairing area
immediately aft of the RH wheel well.
Purpose
The reservoir service station provides convenient single point servicing for
checking and maintaining fluid levels in all three hydraulic reservoirs.
Components
A four-position selector valve and switch is controlled by a single lever that
selects the reservoir to be serviced and to be indicated on the hydraulic quantity
gauge.
Note: To attain a proper fluid level in the reservoirs, the reservoirs must
be serviced with all landing gears down, gear doors closed, steering
and flight controls neutral. When servicing right system the brake
accumulator pressure gage must read at least 2500 psi.
The hydraulic quantity gauge is calibrated in percent of full increments
(110%=1.1) with a green band between .80 and 1.1 indications.
Two sight glasses are installed on each reservoir. The lower REFILL sight glass
gives indication to replenish reservoir. The upper OVERFILL sight glass gives
indication to drain reservoir to FULL level.
A pressure-fill port, service filter, and a hand pump with handle and suction hose
are also located in the reservoir service station.
CAUTION: DO NOT EXCEED 150 PSI FILL PRESSURE WHEN SERVICING
HYDRAULIC RESERVOIR. EXCESSIVE PRESSURE COULD
DAMAGE RESERVOIR.
WARNING: CARE SHOULD BE TAKEN NOT TO OVERFILL THEHYDRAULIC RESERVOIR. OVERFILLING CAN CAUSE
HYDRAULIC FLUID TO ENTER THE PNEUMATIC DUCTING
AND THE AIR CONDITIONING PACKS RESULTING IN
SMOKE AND NOXIOUS FUMES ENTERING THE FLIGHT
DECK AND PASSENGER CABIN. REPEATED HYDRAULICCONTAMINATION OF THE PNEUMATIC SYSTEM CAN ALSO
RESULT IN DAMAGE TO TITANIUM DUCTS.
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SERVICING
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GROUND POWER CONNECTIONS
General
Ground power connections consisting of quick disconnects for pressure and
return lines are provided for each hydraulic system. These connections are theattachment points for an external hydraulic pressure source.
The left and right hydraulic systems each have two sets of ground power
connections. One set is in the engine strut hydraulic bays. The pressure
connection is on the EDP filter module and the return connection is on the filter
module. The second set is in the aft right wing/body fairing for the right system
and on the keel beam between the wheel wells for the left and center systems.
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GROUND POWER CONNECTIONS
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PRESSURE TRANSMITTER LOCATIONS
General
The three hydraulic systems each have an independent system for sensing
pressure. Separate circuit breakers provide electrical power to interchangeabletransmitters.
Pressure signals are sent to EICAS computers. Then the computers furnish
EICAS display with hydraulic pressure on the ELEC/HYD maintenance page
only.
Pressure Transmitter Locations
The left and right hydraulic system Pressure Transmitters are located on the
inboard side support rib, of the Inboard Aileron. Access these by lowering the
Training Edge Flaps, they are located near the rear spar.
The hydraulic system Pressure Transmitter for the center system is located on
right-hand main gear wheel well keel beam. It is just above the #1 Alternating
Current Motor Pump (ACMP) Pressure Isolation Valve.
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PRESSURE TRANSMITTER LOCATIONS
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FLIGHT COMPARTMENT CONTROLS & INDICATIONS
Location/Orientation
The control panel for hydraulic systems is located on the left side of the P5
Overhead Panel. The upper section of the control module has system LowPressure and Reservoir low quantity amber lights. The lower section has the
control switches for the Primary and Demand Pumps along with lights for pump
and system conditions.
System Indications
The left and right SYS PRESS lights through a relay controlled circuit, will
illuminate at 1900 PSI or less and go off at 2400 PSI or more if the Engine
Driven Pump (EDP) is on; and will illuminate at 1300 PSI or less and go off at
1700 PSI or more if the EDP is off. The center SYS PRESS" light illuminates at
1300 PSI or less and goes off at 1700 PSI or more from a separate independent
low pressure switch. The "QTY" lights illuminate if the respective reservoir fluidquantity is 48% or less of the normal full amount. All four pump "OVHT" lights
illuminate at 230oF or more and go off at 185oF or less. The EDP overheat is
Case Drain fluid temperature while Alternating Current Motor Pump (ACMP)
overheat is Motor Case fluid temperature.
Primary Pump Switch
The Primary Pump Switches are square alternate action switch lights with an
"ON" legend visible when the switch light is latched in and an amber pump low
"PRESS" light.
Demand Pump Control
The Demand Pump Switches are rotary, three position, "OFF", "AUTO",and
"ON" switches. In "AUTO" the pump runs on demand, for example, when the
primary pump is unable to maintain system pressure. The pumps run
continuously in the "ON" position. In the left and right systems "AUTO" controls
the ACMP by a pressure switch sensing system pressure - 1900 PSI is "on" and
2400 PSI or more is "OFF", with time delays to reduce pump cycling. In the
center system "AUTO" controls the Air Driven Pump (ADP) by the same
pressure settings. The ADP is also controlled by Landing Gear, Flap/Slat and
Spoiler handle position inputs to meet the high hydraulic flow demands of these
systems during take-off, approach and landing.
The left and right Demand Pump "PRESS" lights illuminate at 1300 psi or less
and go off at 1700 psi or more. The center Demand Pump "PRESS" light
illuminates at 1900 psi or less and goes off at 2400 psi or more. The Demand
Pump "OVHT" lights operate at the same temperatures as the primary pumps
with the left and right ACMP sensing Motor Case fluid temperature while the
center "ADP'' senses Case Drain fluid temperature.
EICAS Display Units (P2)
Hydraulic system messages are displayed on the EICAS display unit.
Aft Control Stand (P8)
The engine fire handles control fluid supply to the engine driven hydraulic
pumps and pump de-pressurization solenoid.
Side Panel (P61)
Flight control shutoff valve switches control operation of 6 valves that can
isolate hydraulic flow to the wing and tail systems.
Ram Air Turbine (RAT)
A RAT control switch is located o the P-5 Engine Start Panel, and is used for
manual deployment. This switch also indicates both PRESS and UNLKD
conditions for the RAT
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FLIGHT COMPARTMENT CONTROLS & INDICATION
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QUANTITY INDICATING SYSTEM
Purpose
An all solid state hydraulic quantity monitoring system provides reservoir fluid
level information for each system.
Components
A capacitance probe in each reservoir senses fluid level. As fluid level changes,
the amount of the probe immersed in fluid will vary thus affecting the probe
capacitance. Probes in the left and right reservoirs are interchangeable. A
larger probe is used in the center system reservoir.
The Hydraulic Quantity Monitor is located on the E2-4 shelf in the Main
Electronics Compartment (MEC). The Hydraulic Quantity Monitor provides
conditioned signals to the EICAS computers for fluid level indication, the
Remote Quantity indicator in the hydraulic servicing station in the right wingbody fairing, the "QTY" lights on the P5 overhead panel, and the automatic
isolation of reserve brakes and steering.
Operation
Analog output signals from the Hydraulic Quantity Monitor are digitized by the
EICAS computers and displayed on the EICAS status and maintenance pages
as hydraulic quantity in terms of percent (%) of full. The decimal 1.00 indicates
a full reservoir.
If the reservoir is filled to 1/4 above the full level (1.22), a magenta overfillmessage "OF" will be displayed next to the quantity indication on both the status
and maintenance pages. The "OF" message will be displayed only when the
airplane is on the ground. When the fluid level falls to .75 and lower a magenta
re-fill "RF" message indicating need for refill is added to the decimal display on
EICAS (.75 RF ).
If the fluid level falls to .48 and lower an amber "QTY" light on the P5 overhead
panel is illuminated and an advisory "(L,C,R) HYD QTY" message is displayed
on the upper EICAS.
Two sight glasses on each reservoir also indicate fluid status. Absence of fluid
at the lower sight glass indicates the need to refill. Fluid appearing in the upper
sight glass indicates an overfill condition.
Dispatch Deviation
HYD QTY (EICAS or Low QTY Lights.) "INOP":
Check applicable Hydraulic System reservoir level for proper fluid quantity
using the fill indicator at the fill station.
A sight gauge installed on each reservoir may be used to check the
reservoir fluid level if the fill indicator at the fill station is inoperative.
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QUANTITY INDICATING SYSTEM
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RESERVOIR TEMPERATURE INDICATING
Operation
A variable resistance temperature transmitter is mounted on each hydraulic
reservoir. As the hydraulic fluid temperature changes, the EICAS computer
measures the change in resistance and indicates the temperature on the lower
EICAS display.
The left EICAS computer controls the temperature indication for the left and
center reservoirs while the right EICAS computer controls the right reservoir
temperature indication. This system is provided for maintenance
troubleshooting and high reservoir temperatures will not result directly in other
fault annunciation. Reservoir temperature indication is shown on the EICAS
ELEC/HYD maintenance page in degrees centigrade.
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RESERVOIR TEMPERATURE INDICATING
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HEAT EXCHANGER
Description
Three identical heat exchangers cool case drain fluid for all hydraulic pumps
except the RAT. For adequate heat dissipation, a minimum of 600 gallons offuel must remain in each wing fuel tank.
Locations
The heat exchangers are installed in the inboard ends of the left and right wing
fuel tanks as indicated:
Left hydraulic system, WS 288 on stringer 2, 3, 4 and 5 LH wing
Center hydraulic system, WS 288 same stringers, RH wing
Right hydraulic system, WS 313.5 same stringers, RH wing
They are mounted on angle strips on top of stringers.
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HEAT EXCHANGER
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TYPICAL LEFT / RIGHT HYDRAULIC FLOW DIAGRAM
Flow Path
A reservoir pressurization module maintains a head pressure in the reservoir.
Fluid flows to the Engine Driven Pump (EDP) is through a reservoir standpipe.
The EDP provides 3000 psi hydraulic fluid to operate right system components.
A fire switch operated supply shutoff valve in this supply line can be closed to
prevent fluid from going to the engine driven pump in the event of an engine
shutdown due to fire.
EDP case drain fluid is used for lubrication and cooling of the pump.
Pressure and case drain outputs are filtered in a common module. Case drain
fluid is cooled in a fuel cooled heat exchangers.
An Alternating Current Motor Pump (ACMP) is a demand source of system
pressure. A separate filter module filters ACMP case drain and pressure output.
Pump pressures and system pressure are monitored by pressure switches.
System pressure is also monitored by a pressure transducer and transmitted to
the EICAS computers. System fluid returning to the reservoir passes through a
return filter.
Loads
Right system pressure is provided to the:
Ailerons
Spoilers
Lateral Central Control Actuators (LCCA)
Rudder
Elevator autopilots and Power Control Actuators (PCA)
Normal brake system
Power transfer unit motor
A motor-operated shutoff valve provides control of fluid flow for the Engine
Driven Hydraulic Pumps (EDP). The hydraulic lines to the tail (empennage)
area and the wing units have isolation valves for maintenance use. If loss of
both hydraulic systems occurs for Stabilizer operation, a Power Transfer Unit
(PTU) pressurizes left system return fluid and provides it to the stabilizer control
module.
Left Hydraulic System
The left hydraulic system is similar to the right system. Check valves and fuses
are installed in the left system rudder and elevator pressure and return lines toprotect the left hydraulic system in the event of a loss of a horizontal or vertical
stabilizer.
Loads
The left hydraulic system supplies power for primary flight controls and some
secondary controls.
Ground Power Connection
Ground hydraulic power connections are located on the EDP and return filtermodules in the aft part of the engine strut.
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TYPICAL LEFT / RIGHT HYDRAULIC FLOW DIAGRAM
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LEFT / RIGHT SYSTEM COMPONENT LOCATIONS
Engine
The Engine Driven Pump (EDP) is located on the forward, left side of the
Accessory Gear Box.
Aft Engine Strut
The reservoir, EDP Supply Shut Off Valve, Alternating Current Motor Pump
(ACMP), return filter module, EDP filter module, ACMP Filter Module, Reservoir
Pressurization Module, and ground service connections are all located in the aft
engine strut area.
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LEFT / RIGHT SYSTEM COMPONENT LOCATION
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ENGINE DRIVEN PUMP (EDP) LEFT & RIGHT CONTROL
EDP Location
Each EDP weighs approximately 38 pounds and is located on the engine
gearbox.
EDP Connections
Pressure and case drain hoses have check valve fittings at the pump, while the
supply hose is connected by a self sealing disconnect.
Compensators Valve and Depressurization Solenoid
The spring in the compensator valve operates the valve to direct flow to the
control piston to maintain system pressure at approximately 3000 psi during
normal operation (no flow).
The EDP has a maximum flow rating of 37 gpm at 3700 rpm at 2850 psi. Pump
output is approximately 24 gpm at idle engine speed.
The pump is depressurized (no flow condition) by powering a solenoid operated
valve. This directs pressure to the compensator valve to reduce yoke angle and
to the blocking valve to cut off the hydraulic output. The solenoid may be
powered by the pump control switch (P-5) in the OFF position or by using the
fire handle
Secondary Pressure Sources (System Demand)
The left and right hydraulic systems each have an Alternating Current Motor
Pump (ACMP) as a demand source of pressure. These (pump) sources are
triggered "ON" when the primary pumps cannot maintain sufficient pressure. In
the left and right systems, each ACMP rated at 7 gpm. These are identical to
and interchangeable with the ACMP'S used in the center system as primary
pumps.
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ENGINE DRIVEN PUMP (EDP) LEFT & RIGHT CONTROL
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EDP CONTROL - LEFT AND RIGHT SYSTEM
EDP Push Switch
The control switch for the EDP is a square shaped alternate action push-button
switch on the P5 overhead panel. Both the white "ON" mechanical flag and theamber "LOW PRESS" light are located on the face of the switch.
Function
As the pump is switched to the "OFF" condition, the white "ON" is hidden by a
mechanical shutter and the pump depressurization solenoid valve is energized
to close and prevent further fluid flow to the system. The pump will continue to
run as long as the engine rotates. There is no time limit to pump operation while
depressurized as long as a supply flow to the pump is available.
The pressure light is always active and will illuminate when the pump is de-
pressurized or pressure at the pump outlet is low (at or below 1900 psi).An EICAS advisory message will identify the pump (i.e., L HYD PRIM PUMP).
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EDP CONTROL - LEFT & RIGHT SYSTEM
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EDP SUPPLY SHUTOFF VALVE - LEFT & RIGHT SYSTEMS
General
An Engine Driven Pump (EDP) supply shutoff valve is located at the forward
end of each engine strut bay. It is mounted on the engine strut aft bulkhead.
Access is through the engine strut left access panel.
Operation
The two position valves are electrically operated and are normally open. Valve
position is controlled through the associated engine fire switch and is controlled
with 28vdc power from the battery bus. When the valve is selected closed, the
EDP depressurization solenoid is also energized. A red valve position indicator
extends from the side of the valve/motor drive housing to show valve position.
The valve cannot be manually operated.
CAUTION: PUMP OPERATION OF MORE THAN 5 MINUTES WITH THEVALVE CLOSED AND ENGINE TURNING MAY DAMAGE THE
PUMP. SEE THE MAINTENANCE MANUAL FOR INSPECTION
PROCEDURE.
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EDP SUPPLY SHUTOFF VALVE LEFT & RIGHT
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ALTERNATING CURRENT MOTOR PUMP (ACMP)
Primary Pressure Source
The center system has two Alternating Current Motor pumps (ACMP) rated at 7
gpm each as its primary hydraulic source.
General Description
ACMPS act as demand pumps in the left and right hydraulic systems to
augment the Engine Driven Pump (EDP) and provide hydraulic power for
ground systems tests when the engines are not operating. Two ACMPs are the
primary pumps in the center hydraulic system. The 4 pumps are identical and
interchangeable.
Two types of pumps are available, Abex or Vickers. The pumps are similar in
output and operation. Both are variable displacement, pressure compensated,
constant horsepower hydraulic pumps. The electric motors are 115 volt threephase, continuous duty, explosion proof units. They are fluid cooled and each
has a thermal switch that closes at 225F for overheat indication. The AC
motors draw approximately 45 amps at maximum power and approximately 167
amps peak starting current per phase. The ABEX ACMP has an external ripple
damper to smooth the pump output. It is rated at 6 GPM at 2850 PSI at 5700
RPM. Below 2850 PSI the pump is compensated so that pump delivery will
increase to 12 GPM at 1200 PSI.
The Vickers ACMP has an internal ripple damper. It is rated at 7 GPM at 2850
PSI at 5700 RPM. Below 2850 PSI, the pump is compensated so that pump
delivery increases to 14 GPM at 1500 PSI.
Maintenance Practices
Continuous pump operation is possible when the system heat exchanger is in a
fuel tank containing a least 4020 lbs of fuel (600 gal., 1827 kg). If the fuel tank
contains less than 4020 lbs limit operation to 10 minutes followed by a minimum
of 20 minutes cooling. Stop pump operation if hydraulic reservoir fluid
temperature exceeds 100C or the pump overheat light/message illuminate.
Secondary Pressure Sources (System Demand)
The center system Air Driven (ADP) pump, is rated the same as primary
(EDP's) in left and right systems, but are not interchangeable. . Also in the
center system has a Ram Air Turbine pump (RAT) rated at 11.3 gpm, used to
power flight controls in emergencies only.
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ALTERNATING CURRENT MOTOR PUMP (ACMP)
B767 3S2F ATA 29 00
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L / R ACMP CONTROL - PRESSURE AND OVERHEATINDICATION
Alternating Current Motor Pump (ACMP) OFF or ON
The ACMP low pressure light (L9) is connected to the ACMP low pressureswitch (S30). It is illuminated when the pump switch (S7) is in the OFF
position and when the pressure is below 1300 PSI with the switch ON. The
system low pressure light is connected to on the Engine Driven Pump (EDP)
filter module.
ACMP Auto Mode
When Engine Driven Pump (EDP) pressure drops to 1900 psi for longer than
0.3 second, the EDP low pressure switch turns on the ACMP. The on control
relay latches on a ground through relay (K126). This relay closes a circuit thru
(K128) ACMP Off Control relay, energizing the power relay in the ACMP
Electrical Control Unit (ELCU M896) turning on the ACMP.
The EDP low pressure sense relay (K127) switches the system low pressure
light (L3) from pump control pressure switch (S32) to the ACMP low pressure
switch (S30). The EDP low pressure light (S4) always responds to the EDP
pressure switch (S31) regardless of the position of the ACMP control switch
(S4).
If pressure at the ACMP low pressure switch (S30) drops below 1300 psi, both
the ACMP low pressure light (L9) and system low pressure light (L3) illuminate.
The ACMP low pressure light (L9) is connected to the pump control pressure
switch (S30) when the ACMP is not running. When the ACMP turns on, the
ACMP On control relay (K126) switches the ACMP low pressure light (L9) to the
ACMP low pressure switch (S30).
When the EDP pressure is restored above 2400 PSI the EDP pressure sense
relay (K127) is de-energized enabling the ACMP OFF control relay (K128) to
energize after a 15-second time delay. As the ACMP OFF control relay (K128)
energizes, it interrupts the holding circuit to the ACMP ON control relay (K126)
turning off the ACMP.
ACMP Anti-cycle Protection
The anti-cycle protection circuit in the ACMP ELCU is energized whenever the
ACMP demand pump switch (S7) is in either the AUTO or ON position. The
anti-cycle protection circuit prevents the ACMP from restarting automatically
after an ELCU auto shutdown for an electrical fault. To restart the ACMP afteran ELCU auto shutdown the anti-cycle protection circuit must first be reset by
turning the demand pump switch (S7) to the OFF position.
Engine Start
Left ACMP operation is inhibited on the ground during the engine start cycle on
either engine.
Overheat Indication
ACMP overheat indication is controlled by a temperature sensing switch on thepump which monitors hydraulic fluid temperature in the pump housing. The
switch will close at 225 degrees F causing the ACMP overheat light to illuminate
and the EICAS advisory message "L DEMAND HYD OVHT" to appear.
Takeoff Operation Right System Only
When in the ground mode the right ACMP will run continuously whenever the
slats are commanded to takeoff either by the flap handle or the alternate
position select and slat arming switches, as sensed by the flap/slat electronics
unit (FSEU). This is to ensure uninterrupted braking power in the event of a
RTO due to right engine failure.
Note: Right system shown in graphic, left system similar.
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CENTER SYSTEM DIAGRAM
Reservoir
This reservoir is similar to those in the left and right systems, but it holds more
fluid. The center reservoir is a 14.7 gallon container holding 8.6 gal. When full,
actual volume may be obtained as status on EICAS; otherwise, low quantity will
be indicated by an amber "RSVR/QTY" light. The temperature of hydraulic fluid
in the reservoir is available on the EICAS ELEC/HYD maintenance page.
Alternating Current Motor Pump (ACMP)
The Primary Pumps in the center system are Alternating Current Motor Pumps
(ACMP) units with Alternate Action switch lights for control on the P5 panel.
Each switch light has an amber low pressure "PRESS" light operating from a
switch in the respective ACMP filter module at or below 1300 psi. Overheat
"OVHT" amber lights for each ACMP illuminate at 230oF in each motor case.
Air Driven Pump (ADP)
The Demand Pump in the center system is air driven by a turbine and controlled
by a rotary switch with "OFF", "AUTO" & "ON" positions the same as the left and
right ACMP'S. The "AUTO" mode is controlled through this select switch and
S29 pressure switch in the filter module, or an anticipatory circuit involving Gear,
Flaps, Slats and Speedbrake handle. Protection from turbine over-speed is
provided by a trip mechanism. Overheating (230oF) of the fluid is detected in
the case drain fluid in the filter module.
Ram Air Turbine (RAT)
The RAT is automatically deployed by low engine n2rpm (50% or less) on both
engines while in flight with airspeed greater than 80 knots. Manual deployment
may be performed by an Alternate Action type switch on the P5 overhead panel.
A separate pressure switch (1700 psi) in the RAT mode in the right wheel well
turns on the green "Press" light in the switch light on the P5 panel for RAT
pressures of 1700 psi or greater. The RAT may be retracted, after proper blade
orientation, on the ground only.
A check valve in the hydraulic line from center system primary and demand
pumps makes it possible for the RAT developed pressure to only power primary
flight controls, Stabilizer and Spoilers. A separate relief valve permits RAT over-
pressure flow to the reservoir.
Isolation Valves
Two isolation valves may be used to direct below standpipe hydraulic fluid
through C1 to the reserve brake and steering system. These valves (reservoirisolation and pressure isolation) are controlled by the reserve brake and
steering switch on the P1-3 panel. This switch will also turn on the C1 Hydraulic
Pump. Isolation valve failures are indicated by the RSV BRAKE VAL EICAS
message.
System Pressure
The center system pressure transmitter is located upstream of the #1 ACMP
Isolation Valve so that the full range of system pressure may be available for
crew maintenance surveillance on EICAS even through #1 ACMP has been
isolated for reserve brakes and steering. The system pressure light switch is
downstream of the pressure line isolation valve and will illuminate as the valve
closes unless the ADP or #2 ACMP are on.
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CENTER SYSTEM DIAGRAM
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CENTER SYSTEM COMPONENTS
Right-Hand Wheel Well Keel Beam
Two Alternating Current Motor Pumps (ACMP), Reservoir And Reservoir
Pressurization Module, two ACMP Isolation Valves, two ACMP Filter Modules, a
system Pressure Transducer, a System Low Pressure Switch, system Return
Filter and RAT Control/Checkout Module are located in right main wheel well.
Right-Hand Wing To Body Fairing Area
The Ram Air Turbine (RAT) and hydraulic reservoir service panel are located in
compartments aft of right-hand main wheel well. The reservoir air
pressurization service/check-out module for all three hydraulic systems is also
located aft of the right wheel well.
Left-Hand Wing To Body Fairing
The Air Driven Pump (ADP) is located in the compartment just aft of the left
main wheel well.
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CENTER SYSTEM ACMP ELECTRICAL CONTROL
Power Sources
The #1 Alternating Current Motor Pump (ACMP) is always operable with power
on the left AC/DC buses. ACMP #1 can also be turned on by the Reserve
Brakes and Steering Switch if the pump control switch (S2) is off.
The #2 ACMP is only operable when the right AC/DC buses are powered and
there are two generators supplying power, in which case either one or both Bus
Tie Breakers (BTB'S) will be open.
When there is only one source of power, either in flight or on the ground, both
BTB's will be closed. When both BTB's are closed, the #2 ACMP can be
operated only through secondary contacts in the Electrical Control Units (ELCU)
of the other three ACMP'S when the associated ACMP is off.
The control circuit through the left hydraulic system ELCU is disabled duringengine start. This prevents #2 ACMP from coming on line when the left ACMP
drops off during an engine start with only one generator power source available.
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CENTER SYSTEM ACMP ELECTRICAL CONTROL
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AUTOMATIC ISOLATION OF ALTERNATING CURRENTMOTOR PUMP (ACMP) NUMBER 1
Purpose
Isolation Valves controlled by the Reserve Brakes and Steering Switch provides
a means of pressurizing alternate brakes and nose wheel steering using the #1
ACMP and fluid isolated below the standpipe level from the center reservoir. If
center system fluid is lost, isolation of fluid occurs automatically at the low
quantity warning level. If both center and right hydraulic systems are lost this
system allows for regaining brakes and nose wheel steering. If only the center
system is lost, steering may be regained while brakes remain on the right
hydraulic system.
Components
Pressure Isolation Valve, Number 1, is a motor driven valve that shuts off
hydraulic pressure to all center systems except nose wheel steering and thealternate brake system.
Supply Isolation Valve, Number 2, is a motor driven valve that switches the #1
ACMP hydraulic supply from the reservoir standpipe to the bottom of the
reservoir to access the reserve fluid supply below the standpipe.
Reserve Brakes and Steering switch is a lighted push-button switch containing a
white "ON" legend and an amber "VALVE" light located on the P1-3 panel.
Reset/Disable switch is a toggle switch on the P-61 panel to reset the automatic
isolation system or to disable the auto function while performing ground
maintenance.
Operation
Actuation of the reserve brakes and steering switch turns on the #1 ACMP, if off,
and shows the "ON" legend in the switch.
Electric power is first supplied to drive the Supply Isolation Valve to the closed
position. When fully closed, the Supply Isolation valve directs power to drive thePressure Isolation Valve to the alternate position. An amber "VALVE" light in
the lower half of the reserve brakes and steering switch will illuminate to indicate
a disagreement between the switch position and the position of either valve. If
the disagreement exists for 6 seconds an EICAS advisory message "RSV
BRAKE VAL" will be annunciated.
With the reserve brakes and steering switch in the unlatched position, both the
Pressure and Supply Isolation Valves will operate to the closed and alternate
positions respectively when center system fluid reaches "LOW" quantity level
(48%) and the airplane is in flight. The pump (#1 ACMP) then must be activated
by pressing the reserve brakes and steering switch or the #1 ACMP switch. A
white "ISOLATION" light on the P-61 right side panel will illuminate when either
isolation valve is not in the open (normal) position.
While the Reserve Brakes and Steering switch is selected "ON", center system
pressure will still be transmitted to the EICAS computer. However the system
low pressure switch (S-35) is isolated from pressure causing the center system
low pressure light to illuminate and the EICAS C level message (Low
Pressure) to appear.
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S1 RES BRK &STRG RESET
SW
NORMAL
DI SABLE
RESET/
S2 ACMP C1
SEL SWI TCH (P1- 3)
SEL SW( P5)
K124 ( P36)
SOURCE SELECT MAI NT PNL ( P61)
TO EI CAS
SENSE RLY
K2
K4 PWR K5 TD RELAY
TD
SEC
10
SUPPLY
POWER
BUSGND SVC115V AC
L20
HYD QTY
P11 CB PANEL
P11 CB PANEL
L/ R EI CAS COMPUTERS
VAL" BRAKE"RSV
6 SEC
2
13
C SYS
I SOLATI ON VALVE
RES BRKS & STRG
L15
SET
RESET
L- 1
VLV RLY
. 3 SEC TD
TD
QTY MON
M1216 RESERVE BRAKES & STRG HYD
HYD SYS C NO. 2
K1 I SLN
LOWK3
RLY
LATCH
QTY
P5
1
"C HYD QTY"
1
1
MD & T POWER1
1
AI R
GND
M122 HYD
wI SOLATED
PRESS SW
S33 ACMP C- 1
PTO PUMP
PRESS
ON
QTY
AUTO
a
VALVE
ON
a
L BUS28V DC
' C' SYSLOW
( E2-4)V110 NO. 1 I SOLATI ON
V111 NO. 2 I SOLATI ON
VALVE, PRESS.
VALVE, SUPPLY
RI GHT WHEEL WELL KEEL BEAM
M342 HYD SYS C
NC
D474
NO. 2 I SOLATI ON
ACMP NO. 1
N0. 1
RESERVOI R
NO. 2)( ADP/ ACMP
TO SYS
I SOLATI ON VALVEHYD SYS C NO. 2
PUMP C1 PRESS
LEGEND
VALVE
RETURN
EXCHANGERTO HEAT
AIR
RETURN
PRESSURE
SUPPLY
CLOSED
NOT
OPEN
NOT
NOT OPEN
OPEN
M
OPEN
NC
CLOSE
LI GHTPRESS.TO SYS
PRESS. XMTR
C PRESS.S35 HYD SYS
NCP
NC
CLOSED
CLOSED
NOT
OPEN
NOT
OPEN
NOT OPEN
OPEN
M
OPEN
NC
CLOSE
S33 ELEC HYD
TO RETURN
NC
1700 PSI
P
STEERI NG
NOSE GEAR
VALVEI SOL
GEAR ACTUATI ON
NOSE LANDI NGBRAKES
CLOSED
FWD
EI CAS PRESSURE
I NDI CATI ON
ON
AUTOMATIC ISOLATION OF ALTERNATING CURRENT MOTOR PUMP (ACMP) NUMBER 1
1
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AIR DRIVEN PUMP (ADP) COMPONENTS
General
The pump is a single unit with a pressure regulator/shutoff valve and modulating
valve to control air which turns a turbine driven hydraulic pump. A muffler is
installed in the inlet air duct to the turbine to reduce the noise level, and an
exhaust duct directs the "spent" turbine air overboard.
Hydraulic Pump
The hydraulic pump produces 37 gpm at 2850 psi while turning at 5683 rpm.
The Variable Displacement, Constant Pressure pump regulates turbine speed
by load and has a compensated cutoff with (0) zero flow at 3025 psi. At low
flow, turbine speed is decreased; with 2300 rpm at no load and 5683 at rated
load. The ADP pump is driven through a 5.158:1 gear reduction gearbox
lubricated with mil 7808 engine oil.
The case drain fluid cools the gearbox oil through a heat exchanger in the fuel
tank in the right wing.
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AIR DRIVEN PUMP (ADP) COMPONENTS
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ADP CONTROL LOGIC
Purpose
The demand logic circuit controls operation of the pump under different
conditions.
ADP Switch "OFF" - no ADP operation
Pump Switch "AUTO" - the ADP runs dependent on the conditions listed
below
Pump Switch "ON" - ADP continuous run solenoid is energized and the
pump runs continuously
Operation (Auto Mode)
Various conditions control the ADP operation with the switch in "AUTO"; they
are low center hydraulic system pressure, both Alternating Current Motor Pump
(ACMP) switch positions "OFF", gear disagree, slat disagree, flap disagree, andspeed brake handle armed while on the ground.
Low Pressure Operation
Low center hydraulic system pressure (1900 PSI) sensed by S29 causes the
ADP to run for a minimum of 15 seconds. This condition is controlled by relays
K153 & K684. ADP operation is continued for 15 seconds to ensure system
pressure is maintained above 2400 PSI.
Other Auto Operation
ADP operation in "AUTO" is continuous if:
Both center ACMP switches are "OFF"
Slats disagree with flap lever position sensed by the PSEU
Flaps disagree with flap lever position sensed by the FSEU Landing gear and landing gear lever positions disagree sensed by the
PSEU
Speed brake lever "ARMED" with the airplane in ground mode
Hydraulic Generator Commanded ON
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ADP OPERATION
Operation
The ADP is turned on by either continuous run or demand run solenoid valves.
Control air is supplied from the regulator/shutoff valve at 13 psi through a jet
pipe which is positioned by the hydraulic pump Swash Plate and ModulatingValve output pressure.
The hydraulic pump swash plate angle is controlled by the pump output
pressure. Movement of the swash plate to increase flow deflects jet pipe to
"fast" side and opens the modulating valve to increase air flow to the turbine. A
large swash plate angle due to low pressure, or high flow demand, increases
valve opening to increase pump output. Pump output is 37.0 GPM at 2850 PSI
at 5683 RPM. A small swash plate angle from high pressure or low flow
demand, reduces valve opening to decrease pump output. Pump output is near
0 GPM at 3025 PSI at 2300 RPM.
Over-Speed Control
An electronic topping circuit prevents over-speed from a sudden drop in
hydraulic pressure. A Monopole Sensor sends a turbine speed signal to the
Over-Speed Control Card (M1057) in the P-50 card file. Maximum speed is
limited to 6000 - 6600 RPM. An over-speed condition causes rapid interruption
(pulse modulating) of the signal to the controlling solenoid.
A centrifugal over-speed switch provides over-speed shutdown by closing the
regulator/shutoff valve if turbine speed reaches a maximum of 7100 - 7700
RPM. An over-speed shutdown is magnetically latched and the ADP cannot be
restarted until the solenoid valve is manually reset by a test/reset switch on thedoor of the P36 panel in the equipment center. This switch can also be used to
test the over-speed shutdown solenoid circuit.
ADP Over-Speed Annunciators
The ADP Over-Speed Control Card (M1057), located in the P-50 card file
contains three LED'S that annunciate ADP conditions labeled DS 1 - on O/S,
DS 2 - AUTO O/S and DS3 - pwr in. Lights DS 1 and DS 2 will illuminate
whenever over-speed topping occurs in the relevant mode and is out when
speed is reduced back to normal range. The lights will not be on if thecentrifugal switch has caused a shutdown to occur. "DS3" is on any time the
ADP is operating.
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ADP OPERATION
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RAM AIR TURBINE (RAT)
General
The RAT is an air turbine driven hydraulic pump that provides emergency
hydraulic power for the flight controls in the event that power is lost on both
engines. The RAT is stowed inside the right aft body fairing.
Operation
When deploying, the RAT pivots downward to extend the turbine into the
airstream. An electric motor drives the unit for both deployment and stowing.
The Motor extends and retracts the RAT by rotation of a motor arm and
actuation link. A 15 Degree Limit Switch, permits partial retraction of the RAT so
that the blade can be locked and the blade centered switch can be closed.
Down and Up Limit Switches provide extend/retract motor shutoff at full down or
full up travel limits. A Manual Override Switch, located on P5 panel, permits
manual selection of RAT extension either in air or on ground.
Hydraulic Pump
The Abex variable displacement, compensated pump has a rated output flow of
11.3 gpm at 2140 psi at 4165 rpm. Turbine/hydraulic pump speed ratio is 1:1.
Turbine Blades
Two variable pitch blades are controlled by a counterweight and governor spring
inside the turbine hub. Governed speed is 4165 +/-45 rpm at a minimum
airspeed of 125 knots. A lock plunger prevents blade rotation when the RAT is
in the stowed position, and prevents complete RAT retraction unless the turbineblade is locked in the proper position for stowing. Blade lock and switch
activation occurs when the RAT has been retracted 13.5 degrees from the
fully-extended position.
A Teleflex Cable unlocks the turbine blade and opens the blade lock and
centered switch when RAT is extended.
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RAM AIR TURBINE (RAT)
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RAT OPERATION
Extension
Automatic deployment of the RAT is triggered in the air mode only by having low
N2speed (less than 50%) on both engines and an airspeed greater than 80
knots.
Manual electric control of extension of the RAT may be performed by a RAT
Guarded Override Select switch on the P5 overhead panel at any time, in flight
or on the ground.
Retraction
The retraction of the RAT is possible only on the ground and is triggered by a
guarded switch near the checkout module on the keel beam in the right main
gear wheel well. The RAT cannot be retracted beyond 15 degrees until the
propeller blade is centered with the locking pin in place so that the blade lockand centered switch can complete the retract circuit.
Ground Checkout
To accomplish the ground checkout of the RAT, the center system must have
hydraulic pressure flow capability of 17 gpm or better. The two center ACMP'S
both on will not provide enough flow. The ADP or a ground source of hydraulic
power must be used.
By pulling the handle on the checkout module in the right main gear wheel well,
the RAT is back-driven hydraul ically. A Tachometer Module has lights to
indicate the speed range for governor/RAT check.
Green indicates on speed
Red indicates over-speed
No light Indicates under-speed
A lamp test switch is also provided, however the RAT must be rotating in order
to test the lamps.
WARNING: CARE SHOULD BE TAKEN WHILE OPERATING THE RATAS THE BLADES TURN AT A HIGH RATE OF SPEED. BE
SURE TO FOLLOW ALL PRECAUTIONS IN THE
MAINTENANCE MANUAL.
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RAT OPERATION
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RAT CONTROL LOGIC
Automatic Deployment
Automatic extension / deployment of the RAT is possible in the AIR mode when
both engines are shut down.
The electrical drive of the RAT to the deployed position will stop as the motor -
driven drive arm hits a down limit switch (S365). Any time the RAT is not full up
(as limited by the up limit switch S369), The amber unlocked light will illuminate
in the M49 module on the P5 panel.
The RAT green pressure light will illuminate when its developed pressure is
1700 psi or above.
Manual Control
Manual electric control of the RAT is with the guarded switch (S7) on (M49)module on the P5 panel. It is possible to do this at any time while on the ground
or in flight. For this sequence, a separate Override Limit (down) switch (S501)
is used - operating from the motor driven arm.
The unlock and pressure lights are always active.
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RAT CONTROL LOGIC
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POWER TRANSFORMER UNIT (PTU) STAB TRIM
General
The power transfer unit (PTU) is a backup system to provide hydraulic power for
the stabilizer. If the left and center hydraulic systems are not operational to
drive the stabilizer ball-screw hydraulic motors, the PTU enables the righthydraulic system to provide a third power source for stabilizer trim.
The PTU components are located in the stabilizer compartment on bulkheads
above the stabilizer trim ball-screw mechanism. The PTU system is connected
to the left and right hydraulic systems and the left stabilizer trim control module.
The system contains the following hydraulic components:
Right hydraulic system shutoff valve module
Motor/pump assembly
Pressure filter module Case drain filter module - Left hydraulic system isolation valve module
Relief valve
Check valves
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PTU SYSTEM
Power Transfer Unit
The power transfer unit is commanded ON automatically to provide hydraulic
power to drive the stabilizer in the event both left and center hydraulic systems
fail.
The following components in the power transfer unit (PTU) system provide
hydraulic pressure to the left stabilizer trim module from an isolated left
hydraulic system supply source. Pressure is supplied by the right hydraulic
system pumps.
Left System Isolation Valve
The isolation valve is installed in the left system pressure line to the stabilizer
trim module. The valve has two positions and is operated by a DC motor.
When the valve is in the OFF (closed) position, it helps to isolate the part of the
left hydraulic system which contains the PTU pump and the stabilizer trim
module. When the valve is in the ON (open) position, it permits the usual flow of
left system pressure to the stabilizer trim module.
Right Hydraulic System Shutoff Valve
The shutoff valve is installed in the right system pressure line to the PTU motor.
The valve has two positions and is operated by a DC motor. When the valve is
in the ON (open) position, it supplies right hydraulic pressure to operate the
PTU motor. When the valve is in the OFF position, it removes right system
pressure to the PTU motor. The shutoff valve also has a position indicator and
manual override lever.
Filter Modules
Filter modules are installed in the pump pressure and case drain lines. The
filters are non by-passable. The pressure filter cannot be cleaned. The case
drain filter can be cleaned.
Relief Valve
A relief valve, installed between the left elevator feel computer and the left
Stabilizer Trim Control Module (STCM), prevents loss of isolated left system
hydraulic fluid through the elevator feel port of the left STCM. The relief valve is
closed when pressure at the STCM feel computer port is less than 100 psi.
PTU Return Compensator Module
The return compensator module is installed in the left system return line from the
stabilizer trim module. The return compensator module includes a bypass valve
and a compensator that contains about four cubic inches of fluid. When the left
hydraulic system is operating correctly, fluid that flows from the stabilizer trim
module through the left system return line to the reservoir must flow through the
return compensator. Flow through the compensator is initially blocked by the
bypass valve. This causes fluid to be pushed into the compensator. When the
compensator is full, the fluid pressure in the line increases until it opens the
bypass valve to permit flow of fluid through the compensator to the left return
system. When a failure in the left hydraulic system causes the PTU system tooperate, the left system isolation valve closes. This removes left system
pressure from the stabilizer trim module. When the pressure in the stabilizer
trim module return line decreases to 45 to 50 psi, the bypass valve in the
compensator closes to isolate the PTU system from the left return system. The
fluid in the compensator is pushed out by the piston and spring and becomes a
source of fluid for the PTU pump inlet.
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PTU SYSTEM
TRAINING MANUALFOR TRAINING PURPOSES ONLY
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PTU CONTROL LOGIC
System Control
Operation of the PTU is controlled automatically.
Power
Electrical power from the left 28 vdc bus is used to operate the PTU control
relays, the right hydraulic system shutoff valve and the left hydraulic system
isolation valve.
Left Hydraulic System Isolation Valve
When the airplane is in the air, air/ground system No. 2 connects the left
hydraulic system isolation valve controls to the left hydraulic system pressure
and quantity indication of the left reservoir.
The left hydraulic system isolation valve closes under either of the following
conditions:
The hydraulic quantity monitored in the left reservoir falls below 0.48
The left hydraulic pressure produced by both the Engine Driven Pump
(EDP) and the Alternating Current Motor Pump (ACMP) is low.
If one of these conditions is removed, the left hydraulic system isolation valve
remains closed for an additional time of 20 seconds to prevent nuisance signals
of short duration from operating the isolation valve intermittently.
Right Hydraulic System Shutoff Valve
When the left hydraulic system isolation valve is commanded closed, the right
hydraulic system shutoff valve is controlled by the control wheel stabilizer trim
control switches and the center hydraulic system pressure.
Loss of center hydraulic system pressure and a stabilizer electric trim commandfrom either the captain's or the first officer's control wheel switches, cause the
right hydraulic system shutoff valve to open and start PTU operation.
The right hydraulic system shutoff valve remains open as long as a stabilizer
electric trim signal is present and the center hydraulic pressure is low. When
the stabilizer electric trim signal is removed, or the center hydraulic pressure is
restored, the right hydraulic system shutoff valve is commanded to close.
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PTU CONTROL LOGIC