B767 ATA 36 Student Book

PNEUMATICS CH 36

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ATA 36 PNEUMATIC SUPPLY TABLE OF CONTENTS GENERAL…………………………….……………………… ……………..............4 COMPONENT LOCATION ………………………………….….…………............6 CONTROL AND INDICATION………………………………............... ………….8 AIR SUPPLY DISTRIBUTION SYSTEM………………….….………….............10 ENGINE AIR SUPPLY SYSTEM...…………………………...………….............12 ENGINE AIR SUPPLY LOCATIONS ...................………….…………..............14 AIR SUPPLY PRESSURE SWITCHES……………….…….….………..............16 ENGINE AIR SUPPLY SYSTEM………………………….……………...............18 HIGH PRESSURE SYSTEM………………………….…….……………..............20 ENGINE BLEED CONTROL LOGIC…….............………….……….…………...22 ENGINE MANIFOLD PRESSURE CONTROL.........................................……. 24 HPSOV AND PRV……………………………………….……...…….…............... 26 BLEED LIGHT AND MESSAGES............……………………….…………...…...28 INTERMEDIATE PRESSURE CHECK VALVE………….……………...............30 FAN AIR SYSTEM...........……………………………………….………...……….32 AIR SUPPLY PRECOOLER……………………………………………............... 34 PRESSURE REGULATING AND SHUTOFF VALVE……………...…..............36 APU SHUTOFF VALVE CONTROL.................................................................38 APU SHUTOFF VALVE CONTROL..................................................................40 ISOLATION AND ISOLATION CHECK VALVES..............................................42 ISOLATION VALVE CONTROL........................................................................44 AIR SUPPLY INDICATION...............................................................................46 AIR SUPPLY DUCT PRESSURE INDICATION...............................................48 DUCT PRESSURE TRANSMITTERS...............................................................50 OPERATIONAL CHECKS.................................................................................52 GROUND CHECKS..........................................................................................54

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PNEUMATIC SYSTEM - GENERAL Purpose The pneumatic system provides air to the following users: • • • • • • • •

Air Conditioning Cargo Heating Wing Anti-ice Engine Nose Cowl Anti-ice Engine Starting Hydraulic Reservoir Pressurization Total Air Temp Probe Air Driven Hydraulic Pump (ADP)

System Description The system is a supply and distribution system. It consists of three different types of air sources; engine, APU and ground air that are interconnected to the user systems by a distribution system. This course will cover the pneumatic system in general, then in five basic sections: Engine Air Supply, APU Air Supply, Ground Air Supply, Air Supply Distribution and Air Supply Indication.

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PNEUMATIC SYSTEM - COMPONENT LOCATION Location The components of the pneumatic system are located throughout the airplane. The control, monitoring and indication parts of the system are located in the flight compartment and main equipment center. The four basic sections of the pneumatic system are located as follows: Engine air supply system is situated in three areas: on the engine, between the engine and strut and within the engine strut. APU air supply system is situated between the APU firewall and aft pressure bulkhead. Ground air supply system is situated forward of the left air conditioning pack which is forward of the left main wheel well. Air supply distribution system extends from engine to engine and to the APU firewall.

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PNEUMATIC SYSTEM - CONTROL AND INDICATION Description The system incorporates an electronic monitoring/testing system (air supply bite module, E-3) and an electronic control circuit (bleed air control cards, P50) for the engine air supply system. One control panel is provided in the flight compartment on the P5 overhead for the pneumatic system. The control panel incorporates control switches, annunciator lights and a duct pressure gauge. EICAS provides messages on its upper display (CRT) that are associated with the annunciators on the control panel. EICAS also provides duct pressure information on the ECS/MSG page, and as an option, temperature information on the engine bleed air just before it enters the air supply distribution system (precooler out). Interfaces The pneumatic system interfaces with EICAS. The system provides and/or receives information from the air conditioning and the nose cowl TAI systems.

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PNEUMATIC SYSTEM - AIR SUPPLY DISTRIBUTION SYSTEM General Operation The pneumatic system requires minimum crew inputs to operate the system. The engine air supply section is enabled by placing the engine bleed air switchlight to the OPEN position (flow bar displayed). The system is then controlled automatically, providing temperature and pressure regulated air to the various user systems as shown on the graphic. The APU air supply section is also automatically controlled, if it is enabled by placing the APU bleed air switchlight to the OPEN position (flow bar displayed). Once enabled, the APU air supply system will automatically supply air when required to the distribution system. Operation of the ground air supply system requires a ground air cart(s) to be connected to the connector(s). The air flow and temperature is controlled externally at the ground cart(s). The operation of the distribution system consists of selecting the position of the three isolation valves: left, right and center. For normal operation, the left and right valves are selected CLOSED and the center valve is selected OPEN. In this configuration, air from the engines would be available at all times to the center part of the distribution system through the bypass check valves. The distribution system provides air to several user systems but the most important is the air driven hydraulic pump. Additional information on operation will be provided for each of the four basic sections of the pneumatic system, engine air supply, APU air supply, ground air supply and the air supply distribution system, in the following sections of this training manual.

TAT PROBE

14TH STAGE BLEED

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PNEUMATIC SUPPLY - ENGINE AIR SUPPLY SYSTEM Purpose The engine air supply system selects engine bleed air from the High Pressure or Intermediate stage. Air from the engine is temperature and pressure regulated and is ducted to the air supply distribution system as the pneumatic source. System Description Two independent and identical systems are provided, one for each engine. Each system consists of pneumatically controlled valves, electrically enabled pneumatically operated controllers, sensors and pressure and temperature switches. These components function automatically to control the source, pressure and temperature of the engine bleed air. The system is divided into operating functions. These functions are Bleed source control, temperature control, reverse flow control, pressure control and overheat/over-pressure protection. The components that are incorporated into each of the basic functions are as follows: Bleed Source Control The source control components are the high pressure shutoff valve (HPSOV), which is pneumatically controlled by the high pressure shutoff valve controller (HPSOVC). Temperature Control There are three components to control the bleed air temperature. These are the precooler, fan air valve and the fan air sensor. The pressure regulating and Shutoff Valve (PRSOV) as a secondary function will regulate temperature. Reverse Flow Control The 8th stage check valve provides reverse flow control for the 8th stage. The PRSOV provides reverse flow control for the distribution system.

Pressure Control Pressure control is provided by the Pressure Regulating Valve (PRV) for the engine manifold area. The PRSOV controls engine bleed pressure for the air supply distribution system. Overheat and Overpressure Protection A pressure switch and a temperature switch provide protection. The switches, if activated, will affect operational functions.

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PNEUMATIC SUPPLY - ENGINE AIR SUPPLY LOCATIONS Each engine air supply system consists of the following components: • • • • • • • • • • •

Pneumatic Ducts Intermediate Pressure Check Valve High Pressure Shut-Off Valve (HPSOV) High Pressure Controller Pressure Regulator Valve (PRV) PRV Controller Air Supply Precooler Air Modulating Valve Fan Air Temperature Sensor Overheat Temperature Switch Pressure Regulating And Shut-Off Valve (PRSOV)

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PNEUMATIC SUPPLY - AIR SUPPLY PRESSURE SWITCHES Description The Air Supply Over-pressure Switch (114 psi) and PRV Exit Sensor monitor engine bleed air out of the PRV and is measured down stream of the precooler. The PRV Exit Sensor provides information for BITE only. Location The Air Supply Over-Pressure Switch and The PRV Exit Sensor are located in the leading edge of the wing inboard of the engines.

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PNEUMATIC SUPPLY - ENGINE AIR SUPPLY SYSTEM System Interface The bleed air control card provides PRSOV position information to the flow control cards of the air conditioning system. It also provides the same information to the APU air supply valve control circuit. The control circuit for the nose cowl TAI system inputs the bleed air control card to enable the PRV controller if the following is true: there is no strut OVHT (see fire protection), and the engine is not being started. PRV opening can occur for cowl anti-ice with an activated overheat switch. The HPSOV will remain closed. General Operation The system is enabled by placing the engine bleed switch, on the bleed air supply control panel (P5) to ON. This enables the PRSOV, PRV controller and the HPSOV controller. Air is bled from the engine high pressure compressor at the 14th stage bleed ports or the 8th stage bleed ports. The HPSOV controller uses a predetermined schedule, which is dependent on High stage pressure and airplane altitude. At low power settings, the High stage provides the air, and at high power settings, 8th stage is selected. The bleed air control card monitors the HPSOV through the valve's closed limit switch. The card will activate the HPSOV fail indication if the valve is not closed when commanded because of one of the following: High stage is greater than 127 psig, the strut OVHT detection system senses an OVHT (greater than 300 F, 149 C) or the engine bleed air OVHT switch activates (490 F, 254 C). At low power settings, when air is bled off High stage, the 8th stage (intermediate pressure) check valve prevents flow from the High stage into the 8th stage. The PRV and controller regulates the pressure in the engine manifold so that it does not exceed 97+5/-12 psig. Engine bleed air, after flowing through the PRV, flows through the precooler which is part of the primary temperature control section of the engine bleed air system. The precooler has the engine bleed air flowing towards the PRSOV, and cooling engine fan air flowing from the fan air (modulating) valve, through the precooler then overboard. Engine bleed air and cooling fan air are separated by cooling fins. The amount of fan air (cooling air) that flows through the precooler is

controlled by the fan air valve whose position is controlled by the fan air temperature sensor. The sensor is set to control the bleed air temperature to 400° F +/- 30° F. The PRSOV regulates the pressure of the air entering the distribution system to 40 +/- 10 psig. The valve also has reverse flow control that will close the valve if engine manifold pressure is less than the distribution system pressure. The valve incorporates a temperature control circuit that will regulate flow if the temperature of the bleed air exceeds 450° F (232 C). Overpressure and overheat switches monitor engine bleed air at the outlet of the precooler. A pressure of 114 psig or greater in the engine manifold will activate the engine air supply overpressure switch which will activate the BLEED indication circuit (BLEED light and EICAS message ("L(R) ENG PRV") if the PRV is not closed. If bleed air temperature exceeds 490° F +10°/ -5° F, the engine air supply overheat switch will activate and provide a signal to the bleed air control card.The card will output an OVHT signal for indication and another signal to command the PRV and HPSOV controllers to OFF. The circuit may be reset by cycling the engine bleed switch. The BLEED indication circuit will also be activated anytime the PRV or HPSOV are commanded closed and are not closed after a short delay. The air supply bite module monitors the engine air supply system but does NOT provide any inputs for the operation or control of the system.

114 PSI

PRV OR HPSOV OPEN WHEN COMMANDED CLOSED PRECOOLER OUT TEMP >490°

BLEED AIR CARD

CF6-80C2

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PNEUMATIC SUPPLY - HIGH PRESSURE SYSTEM Description The high pressure controller opens and closes the high pressure shutoff valve. The controller is remotely located to avoid harmful temperatures and vibration. The controller is located on the upper left hand side of the engine just aft of the fan cowl. The high pressure controller consists of a cast aluminum body, altitude biased pneumatic switch, internal sensing diaphragm, and a latching shutoff solenoid. Four pressure switches provide BITE LOGIC which will monitor operation of the high pressure controller. Operation The solenoid is commanded to the AUTO or OFF position by signals from the bleed air control card. In AUTO, the HPSOV controller allows the high pressure shutoff valve to operate depending upon high stage pressure. At low altitudes the switchover pressure is 105 psi. Below 105 psi the pneumatic system operates on high stage pressure and above105 psi on intermediate stage pressure. An aneroid changes the switchover pressure linearly from 105 psi at 27,000 feet to 77 psi at 41,000 feet. In the event of electrical power loss, the solenoid remains in the last commanded position. BITE Switches The air supply BITE module monitors the operation of the controller and the valve with BITE pressure switches and position switches. The switches do not have an effect on the operation of the controller or valve. The switches are for indication only. Physical Description The high pressure shutoff valve operates in response to pneumatic servo pressure from the high pressure controller. The HPSOV is located on the right side of the engine and the Controller is on the upper left side of the engine. The valve is spring loaded to close.

The high pressure shutoff valve is a 5.5" disk valve. A half-area pneumatic actuator positions the valve. A piston-type crank drives the disk through a link and crank. The valve shaft extension is hex shaped to allow manual positioning of the valve. A lock pin, normally stored in the actuator cap, must be used to dump actuator servo pressure and lock the valve in the closed position. Failure to use the dedicated lock pin can result in damage to the shutoff valve diaphragm.

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PNEUMATIC SUPPLY - HIGH PRESSURE CONTROL Operation/Control Sequence The high pressure controller and the PRV controller are activated to Auto (ON) by the engine bleed air supply switch, or the engine nose cowl TAI system. The controllers will be inhibited and latched off if an overheat occurs in the engine strut or in the engine bleed air manifold. There is one exception; the PRV controller will not be affected by an OVHT in the engine bleed air manifold when commanded to AUTO by the activation of the engine nose cowl TAI system. Reset of the latching circuits may be accomplished after the overheat condition no longer exists by cycling the engine bleed air switch OFF then to ON. The PRV controller is commanded OFF during the engine start sequence for both engines if the airplane is on the ground and the APU is providing the air. Otherwise only the controller for the engine being started will be commanded OFF. The high pressure shutoff valve's controller (HPSOVC) will be automatically commanded to Auto (ON) during engine start. This will provide pneumatic pressure to the Pressure Regulating Valve (PRV) to ensure positive closure. Backup Operation If a failure occurs in the high pressure control system an indication will be provided. Depending on the faulty component(s), the air supply bite module will record which component is faulty. Also, depending on the fault, the control circuit (bleed air control card) will take action automatically to protect the engine air supply system. The action can be in the form of activating a message on EICAS that requires crew action, or by commanding the PRV, HPSOV, & PRSOV to OFF. The following describes the engine bleed air protection circuit by listing the possible messages and annunciator lights. BLEED Light The BLEED light will illuminate if either the HPSOV or the PRV is open when commanded closed.

ENG PRV message, BLEED light The level "B" message, "L ENG PRV" will be activated if the PRV is commanded closed and does not close within five seconds, or if engine manifold pressure exceeds 114 PSI and the PRV is open. ENG HPSOV message, BLEED light A level "B" EICAS message “L ENG HPSOV" is associated with the High Pressure Shutoff Valve (HPSOV). The message and "Bleed" light are activated by the bleed air control card. The EICAS message and the "Bleed" light will be activated for the following: • HPSOV open and High stage pressure greater than 127 PSIG (PPH switch in the HPSOV controller). • HPSOV commanded to close and does not close. • The Air Supply Bite Module will indicate if the HPSOV or the HPSOV controller is faulty. STRUT DCT LEAK message, DUCT LEAK light The "L STRUT DCT LEAK" level "B" EICAS message and the DUCT LEAK light are activated and latched by the bleed air control card to indicate a strut leak (overheat). The bleed air control card also commands the HPSOV and PRV to OFF for this condition. Reset after cool down, by cycling the ENG BLEED switch. The air supply bite module does not monitor the strut duct leak circuit. L ENG BLD OVHT Message, OVHT Light The L ENG BLD OVHT level "C" message and the OVHT light are activated and latched by the bleed air control card when the air supply OVHT switch activates. In addition the card will command the PRSOV to OFF,HPSOV controller to OFF under all conditions unless Thrust Reversers are selected upon landing and a Strut Overheat condition does not exist. The PRV controller will be commanded to OFF if it is not commanded to AUTO by the ENGINE COWL TAI system. closed. The air supply bite module, if interrogated, will indicate the faulty components.

LEFT BLEED AIR CONTROL CARD

L PRV NOT CLOSED AT 114 PSI L HPSOV NOT CLOSED AT 127 PSI 114 >114 PSI PSI

OFF AUTO 14TH > 127

> 490° F

CF6-80C2

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PNEUMATIC SUPPLY - ENGINE MANIFOLD PRESSURE CONTROL Purpose The pressure regulating valve (PRV) in conjunction with the PRV controller regulates downstream (engine pneumatic manifold) pressure to a level compatible with downstream components and ducting. Location The PRV is just upstream of the precooler on the upper right hand side of the engine. The PRV controller is mounted on the top left side of the engine just aft of the HPC. PRV The PRV is a 5.5 inch butterfly valve and is spring loaded closed when air pressure is removed. The PRV operates in response to control pressure from the PRVC. The HP Valve and the PRV are interchangeable. PRV Controller The PRV controller is a solenoid activated (latching type) pneumatic controller. It includes all the pneumatic-mechanical and electrical-mechanical control functions for the PRV. Operation The PRV and PRV controller operate together to control the engine manifold pressure to 97 +5/-12psig.

ACTUATOR SERVO PRESSURE REGULATED

ELECTRICAL

PRESSURE PORT

CONNECTOR

(DOWNSTREAM OF PRV)

SOLENOID

GE CF6 - 80C2 - 11 O'CLOCK HPC CASE

FILTER

SUPPLY PRESSURE PORT

ACTUATOR

(UPSTREAM OF PRV)

PRESSURE PORT (TO PRV)

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PNEUMATIC SUPPLY - HPSOV AND PRV Ground Handling The High Pressure Shutoff Valve (HPSOV) and the Pressure Regulating Valve are identical and interchangeable. Thus the deactivation procedures for each valve is exactly the same. The airplane operating procedures (crew procedures) are different for each valve. For details see the recommended MEL. The valves may be deactivated to the locked CLOSE position only. The right thrust reverser must be opened to gain access to either valve. The valves may be deactivated (locked close) by removing the locking pin from its stowed position in the actuator. Insure the valve is fully closed (position indicator). If it is not closed, rotate the manual override hex nut until the position indication aligns with the CLOSE mark on the valve. Install the locking pin through the locking crank and into the valve. CAUTION:

IT IS NECESSARY TO LOCK THE THRUST REVERSER IN THE FORWARD THRUST POSITION IF EITHER THE PRV OR THE HPSOV IS DEACTIVATED. REFER TO THE MEL.

To activate, reverse the above procedures. It is very important to insure the locking pin is properly reinstalled in the stowed position. If it is not installed completely, the valve will not operate correctly because the actuator pressure will be vented to ambient around the pin.

POSITION SWITCHES

HEX FOR MANUAL OPERATION

ELECTRICAL

LOCKING PIN

CONNECTIONS

HOLE LOCKING CRANK VALVE

___________

ACTUATOR

VALVE INLET

ACTUATOR SERVO PRESSURE

LOCKING PIN (STOWED POSITION)

VALVE OUTLET

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PNEUMATIC SUPPLY - BLEED LIGHT AND MESSAGES Review Pneumatic Supply Bleed Normal Parameters Engine air supply system controls the pressure, temperature, and flow of bleed air: • 8th stage intermediate air • 14th stage for high pressure When high stage pressure increases to 105PSI (+/-5) the HPC closes the HPSOV. The PRV keeps air pressure to 97PSI (+5/-12) before entering the precooler. The precooler is an air-to-air heat exchanger that uses fan air for cooling. The Fan Air Temperature Sensor works to keep precooler output temps at 400F (+/_30F). The PRSOV contains a temp controller which keeps bleed air temps below 490F. At 442F (+/-7) PRSOV moves toward closed. At 490F PRSOV goes fully closed. The PRSOV also contains a pressure controller which keeps downstream pressure at 40PSI (+/-10). Overpressure switch condition 114 psi. Abnormal Conditions for Bleed Light and Messages Conditions illustrated in graphic for Bleed Light. Message will specify which valve is responsible.

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PNEUMATIC SUPPLY - INTERMEDIATE PRESSURE CHECK VALVE Physical Description The intermediate pressure check valve is an in-line check valve. The valve consists of an outer shell, inner shell with strut supports, piston guide and a sliding valve plate/piston assembly. The duct in which the valve mounts is a 5.5 inch diameter duct. An arrow on the body of the valve indicates direction of flow. When the pressure upstream of the intermediate check valve becomes greater than that downstream, the valve plate and attached piston of the intermediate pressure valve, slide open. The piston guide in the inner shell guides the plate/ piston assembly when moving. When the pressure upstream of the intermediate pressure check valve becomes less than that downstream, the plate/piston assembly slide closed. This prevents reverse flow through the valve. The check valve is located on the engine at the 3 o'clock position. Removal of the check valve requires opening of the right T/R.

VALVE PLATE SUPPORT STRUT

INNER SHELL

OUTER SHELL _______________________ _______________

FROM 8TH STAGE BLEED AIR SOURCE

FROM HIGH STAGE PISTON GUIDE

BLEED AIR SOURCE

VORTEX GENERATOR

VALVE PISTON

FLOW

INNER SHELL

VALVE PLATE (CLOSED) VALVE

FRONT VEIW

PLATE (OPEN)

ENGINE MANIFOLD DUCTING OUTER SHELL

INTERMEDIATE PRESSURE CHECK VALVE B767-300

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PNEUMATIC SUPPLY - FAN AIR SYSTEM

Valve Operation

Sensor Description

The fan air modulating valve opens and closes in response to pressure signals from the fan air temperature sensor.

The fan air temperature sensor mounts in the duct between the precooler and the PRSOV (pressure regulator and shutoff valve). The sensor body contains a lever and crank operated by a bimetallic temperature probe. The temperature probe projects into the duct. A ball poppet regulator valve and air filter are located in the pressure supply line of the sensor unit. Two pressure switches and a temperature sensor provide information to the BITE system. Sensor Operation The fan air temperature sensor modulates the servo pressure that controls the fan air valve. The valve is spring loaded open. With the system pressurized the valve then closes. Increasing temperature causes the poppet to open, servo pressure then vents and the fan air modulating valve opens. Below 370° F (188° C), all temperature bias is removed and the valve remains closed. At 370° F the valve begins to open and when the temperature reaches 430° F (221° C) the valve is full open. Valve Description The fan air modulating valve is a nine-inch diameter pneumatically actuated disk valve. The valve mounts at the cooling air inlet to the precooler. The valve consists of a half-area actuator spring-loaded to the open valve position. The actuator contains a diaphragm-operated poppet attached to a spring compensated lever. A cooling shroud surrounds sensitive valve components. The shroud allows cooling air to pass over the components to prevent overheating. A locking crank and pin is mounted on the actuator. The locking pin when installed in the locking crank manually locks the valve 48 +/- 4° from the valve closed position and vents supply pressure.

The actuator modulates the disk to maintain a bleed outlet air temperature at 400° +/- 30° F (204° C). The valve begins to open at 370° F (188° C) and fully opens at 430° F (221° C). BITE Switches and Sensor Two BITE pressure switches, a BITE temperature sensor and valve limit switches are used to monitor the system's integrity. The air supply BITE module uses the following logic to identify faults in the fan air system: • When bleed air temperature is below 265° F (129° C), the sensed servo pressure (switch 1) . should be greater then 9.25 psig and the fan air valve should be closed. • When bleed air temperature is above 445° F (229° C), the servo pressure (switch 2) should be open and the fan air valve should be open. The BITE module first tests the fan air sensor. If no faults are found, then it tests the fan air valve for faults. A fault in the sensor will inhibit a fault indication of the valve. If no faults are found in either the sensor or the valve the BITE module, then tests the precooler by monitoring the precooler out temperature through the fan air sensor.

AIR SUPPLY BITE MODULE

VALVE CLOSED POSITION SWITCH POPPET PRESSURE REGULATING CONTROL

TO BITE MODULE

REGULATED CONTROL PRESSURE

NO. 1 BITE

POPPET AND

PRESS. SWITCH

NOZZLE

PRESS. 9.25 PSI TEST PORT

IF

THEN

TEMP

VALVE

<265` POSITION SWITCHES

CLOSED

VALVE CONTROL LEVER

LOCKING PIN

AMBIENT

OPEN

SIGNAL PRESSURE

COOLING AIR

INCREASING TEMP

TEMP PROBE (BIMETALLIC)

LOCKING PIN SLOT

-

FILTER

TEMPERATURE

FAN AIR

PR

<2.25PSI OPEN

PRESS. SWITCH BALL POPPET REGULATOR COMPENSATING PRESS. 2.25 PSI SPRINGS

AMBIENT VALVE FEEDBACK CONTROL CAM LEVER

>445`

NO. 2 BITE

SENSOR DIAPHRAGM

OPEN

>9.25PSI CLOSED

BLEED AIR

BITE TEMP SENSOR INLET

BLEED AIR

TO PRESSURE REGULATING & SHUTOFF VALVE

FROM PRECOOLER

CLOSE LOCKING PIN HOLE OPEN

PRSOV (REF)

POSITION SIGNAL PRESSURE LOCKING FROM PRECOOLER LOCKING SWITCH CONNECTIONS CRANK CRANK FILTER ACTUATOR

CONTROL PRESSURE ELECTRICAL CONNECTION

LOCKING PIN

TEMPERATURE REGULATED CONTROL PRESSURE FROM FAN AIR TEMPERATURE SENSOR

BITE PRESSURE SWITCHES

BITE TEMP SENSOR

BLEED AIR TEMP PROBE

DISK

UP

ACCESS DOOR FRAME FWD

OUTLET PORT TO PRECOOLER

NOTE: VIEW FROM RIGHT SIDE OF ENGINE INTO STRUT ACCESS DOOR

FAN_AIR_MODULATING_VALVE

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FILTER __________________________


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PNEUMATIC SUPPLY - AIR SUPPLY PRECOOLER Purpose The precooler is the part of the engine bleed air temperature control system that transfers the heat from the bleed air to the fan air without mixing the two together. Location The precooler is mounted to the lower engine strut firewall. The precooler is in the area between the engine and engine strut and is accessible by opening the thrust reverser and core cowling. Physical Description/Features The air supply precooler is an air-to-air heat exchanger of the cross-flow type. The unit consists of layers of fins separated by parting plates and closure bars. The bleed air inlet receives pressure regulated bleed air from the PRV. A pressure sense port on the precooler provides servo pressure to the fan air valve, which is attached to the fan air inlet. Operation The precooler allows heat from engine bleed air to be absorbed by cooler fan air. Bleed air and fan air flow at approximately right angles to each other, separated by the fin-plate arrangement. Heat from the bleed air is absorbed by the fan air via the fins and plates, thereby cooling the bleed air to a nominal 400 +/- 30° F (204° C).

MOUNTING POINTS 2 OF 4 BLEED AIR OUTLET TO PRSOV

FAN AIR INLET

BLEED AIR INLET FROM THE PRV

FAN AIR OUTLET

FWD

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PNEUMATIC SUPPLY - PRESSURE REGULATING AND SHUTOFF VALVE Purpose The Pressure Regulating and Shutoff Valve (PRSOV) provides four basic functions: • ON/OFF control of the engine bleed air system • Pressure regulation of the engine supplied bleed air • Engine bleed air temperature limiting (protection) and prevents reverse flow from the pneumatic distribution system into the engine bleed air system Location The PRSOV is mounted to the six inch (15 cm) ducting downstream of the precooler in the engine strut (pylon). Physical Description/Features The multipurpose PRSOV is a pneumatically operated and electrically controlled valve. The valve incorporates a valve body and disk, an actuator, a pressure controller, a reverse flow limiter, a temperature probe, limit switches, pressure switches, a solenoid, and devices for locking the valve closed. The spring loaded closed valve has a valve shaft extension which is splined to the valve disk and a locking crank. The locking crank extends on either side of the valve shaft and one end is used as an actuation arm for the Open/Close limit switches. The other end has a threaded hole which allows the valve to be locked closed when a lock pin is installed. The lock pin is stowed on the valve. The locking crank has a hex for manual operation of the valve. Electrical control is provided by a latching type solenoid. Pressure switches and position switches are installed to provide information for the Air Supply BITE MODULE and the engine bleed air control circuit. The valve serves as a firewall shutoff valve and constitutes a part of the firewall.

Operation The solenoid is energized to the AUTO position by a signal from the bleed air control card. The valve is pneumatically actuated to maintain 40 +/- 10 psi. The BITE pressure and position switches provide information to the air supply BITE module. BITE The BITE module monitors the valve for faults. It compares the OFF solenoid signal to the closed position switch (valve should be closed); the 60 psi pressure switch to the OFF position switch (valve should be closed); and the 20 psi pressure switch to the OPEN position switch (valve should be open). Ground Handling The MEL requires that at least one PRSOV be operational, along with several exceptions, to dispatch the airplane. The dispatch deviations guide (DDG) provides the steps required to satisfy the exceptions. One of these exceptions requires the failed PRSOV to be in the closed position. To insure the valve stays in the closed position, the locking pin may be installed in the locking pin hole in the locking crank when the valve is fully closed. If the valve is not fully closed, use a wrench on the hex, rotating the locking crank until the locking pin hole aligns with a hole in the valve body. When restoring the PRSOV to normal operation, insure the LOCKING PIN is installed in its stowed position securely. If the pin is not installed or not installed completely, the valve will not operate.

NO. 1 BITE PRESS SWITCH

NO. 2 BITE PRESS SWITCH

PRESSURE CONTROL 40 +/ - 10 PSI

LOCKING PIN HOLE LOCKING_PIN

FROM STARTER P < 20 PSI

LOCKING PIN (STOWED)

TEMPERATURE CONTROL 450`F - 490`F

VALVE ACTUATOR (SPRING LOADED CLOSED)

P > 60 PSI

REVERSE FLOW CHECK CONTROL ÄP.18 PSI

AIR SUPPLY BITE MODULE

AUTO/OFF

CLOSE

SOLENOID CONTROL

AUTO

OFF

LOCKING CRANK HEX

OPEN/CLOSE POSITION SWITCHES

TO AIR

FROM

FAN AIR TEMPERATURE SENSOR

LEFT_SIDE_VIEW

SUPPLY DISTRIBUTION

PRECOOLER

LOCKING PIN (STOWED POSITION)

INLET PRESSURE VALVE BODY

SHUTOFF SOLENOID MAIN FILTER POSITION SWITCHES

TEMPERATURE SENSOR

PRESSURE REGULATING AND SHUTOFF VALVE

TEMPERATURE SENSOR PROBE

DISK

ELECTRICAL HEX FOR CONNECTOR MANUAL OPERATION (VALVE SHAFT BITE PRESSURE EXTENSION) SWITCHES (NOT SHOWN)

VALVE_ROTATED_FOR_CLARITY

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PNEUMATIC SUPPLY - APU SHUTOFF AND CHECK VALVES Description The APU shutoff valve is a 4.5 inch diameter, duct mounted, disk valve. It is located in the APU air supply duct just forward of the APU firewall. It opens or closes to allow supply air from the APU to enter the air supply distribution system. A 115 volt ac motor drives the valve. The valve consists of an electrical actuator, a body and disk assembly, and a manual override. The disk assembly opens and closes in response to the electrical actuator or the manual override. The valve can be locked in either open or closed positions. The disk assembly pivots on a shaft within the body. One end of the shaft engages the output shaft of the actuator. Actuator position determines the position of the disk. APU Check Valve The APU check valve is a 6-inch, duct-mounted, dual flapper-type, check valve. It mounts in the APU air supply duct forward of the APU shutoff valve. The valve prevents air flow from the engines or ground air connector from entering the APU. The check valve consists of two semi-circular flappers hinged about a pin. The pin runs through the center of the valve body normal to the valve body axis. Normal airflow (away from APU) overcomes the helical torsion spring and drives the check valve flappers open until contact is made with the check valve stop pin. Reverse airflow aids the helical torsion spring to close the check valve.

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PNEUMATIC SUPPLY - APU SHUTOFF VALVE CONTROL Description Power requirements for the APU shutoff valve include 115v ac power for valve operation, 28v dc for relay control and switchlights, and 5v ac for white bar lights. Description/Operation To open the APU AIR SUPPLY valve the following conditions must be met. The APU start switch moved to the START position, which will cause the APU START/ON relay to energize. The APU operating above 95%. The APU FIRE switch in the normal position. The APU AIR SUPPLY switch selected to the ON position and the APU AIR SUPPLY OVERRIDE relay relaxed. This override relay will be relaxed if any of the following sets of conditions is satisfied: • • • •

Starting either engine Both engines N2 RPM is below 50% The center isolation valve is closed Both left and right PRSOVs are closed

Closing of the APU air supply valve can be done by selecting the APU air supply to the OFF position. The valve will close automatically whenever all of the following are met: left or right PRSOV(s) open, the center isolation valve open an engine is not being started and either engine(s) N2 above 50%. The valve will also close automatically when the APU is selected off, or the APU fire switch is in the fire position or the battery switch is placed off. (The battery bus supplies the power for the APU start/on relay). Valve Indication The "VALVE" light will illuminate in the APU air supply valve switchlight if a disagreement exists between commanded and actual valve position. If the disagreement lasts longer than six seconds, a level "C" APU BLEED VALVE message will be displayed by the EICAS.

START

R ENG STARTING

1

APU START/ON RELAY ENERGIZED

L ENG STARTING

2

CENTER ISOLATION VALVE CLOSED

3

APU N2 > 95%

APU FIRE SW IN NORMAL (FLT COMPT)

1

APU AIR SUPPLY VALVE

BOTH ENGINES N2 < 50%

R PRSOV CLOSED

4

APU AIR SUPPLY SWITCH SELECTED TO ON (P5)

5

APU AIR SUPPLY OVERRIDE RELAY NOT ENERGIZED COMMAND SIGNAL DISAGREES WITH ACTUAL VALVE POSITION

L PRSOV CLOSED

1

"OPEN"

AUX PWR CONTROL UNIT

V A L V E

APU AIR SUPPLY VALVE COMMAND SIGNAL

VALVE LIGHT (P5)

"C" APU BLEED

EICAS MESSAGE (6 SECOND DELAY)

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PNEUMATIC SUPPLY - ISOLATION AND ISOLATION BYPASS CHECK VALVES Description/Location Isolation Valve There are three isolation valves in the air supply system. The left and right isolation valves are located in their corresponding air supply body crossover ducts. The center isolation valve is in the APU air supply duct just aft of the crossover duct, on the forward wall of the left wheel well. All three isolation valves are non-modulating 6-inch diameter disk valves. The valves are powered by 115 volt ac. A lever normally engaged with the motor drive disengages to allow manual movement of the disk independent of the valve motor. Isolation Bypass Check Valve Two isolation bypass check valves are mounted directly under the left and right isolation valves. The check valves are flapper-type valves with a 5-inch diameter inlet and a 4-1/2 inch-diameter outlet. The check valves consist of two semi-circular flappers attached to a hinge pin. The hinge pin runs through the center of the valve body. Airflow in the direction of the arrow on valve body overcomes a helical torsion spring and drives the valve flappers open until contact is made with the check valve stop pin. Reverse airflow aids the helical torsion spring in closing the valve flappers. Note:

Clamps with safety latches must be installed on the inboard side of the left and right isolation valves and bypass check valves and on the lower side of the center isolation valve.

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PNEUMATIC SUPPLY - ISOLATION VALVE CONTROL Operation Power requirements for the valves include 115 volts ac power for operation, 28 volts dc power for the indication part of the circuit, and 0-5 volts ac power for white flow bar illumination (panel lights). There is a separate switchlight to control each valve (left, right, and center). The CENTER ISOLATION VALVE control switchlight is normally selected to the OPEN position and is guarded to that position. The control circuits for the three valves are similar so only the circuit for the left valve is shown. When the control switchlight is pressed to OPEN (Flow Bar Displayed), 115 volts ac powers the valve open. When the valve control switchlight is pressed again (Flow Bar Not Displayed), 115 volts ac powers the valve closed. 28 volts dc provides power to the indication relays which control the amber disagreement lights and the EICAS indications. The amber VALVE light is on during valve actuation and off when valve reaches its commanded position. This is determined by the limit switches on each valve. If the amber light remains on for greater than six seconds, a disagreement between the valve position and command is indicated on EICAS as a level C message. Indication power is provided by the STBY bus. Operating power is provided by the XFR BUS. Its closed indication relay provides a discrete input to the ENG EEC. The Center ISLN VLV CONTROL SWITCH provides a discrete input to the L ENG EEC. The Center ISLN VLV closed IND relay is part of the control circuit for the APU AIR SUPPLY VALVE. Operation - Simplified There is a separate switchlight to control each isolation valve (left, right, and center). The CENTER ISOLATION VALVE switchlight is guarded in the valve open position. When the switchlight is depressed to open, 115 volts ac powers

the valve open. When the valve switchlight is depressed again, 115 volts ac powers the valve closed. 28 volts dc is provided through relay logic for the amber valve disagreement light. The amber VALVE light is on during valve actuation and off when valve reaches its selected position. This is determined by the limit switches on each valve. If the amber light remains on, a disagreement between the valve position and selected is indicated. If the disagreement last longer than 6 seconds the EICAS advisory message L(C)(R) BLD ISLN VAL Will be displayed.

LEFT ENGINE AIR

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PRESSURE INDICATION SYSTEM - AIR SUPPLY INDICATION Purpose The air supply indication system provides information to the flight crew and maintenance personnel. The system monitors and displays normal and abnormal system conditions. Description The system consists of engine bleed air control cards, duct pressure indication, an air supply bite module, overheat and valve operation annunciation. The duct pressure indicating circuit has transducers in each air conditioning compartment, and display is provided on EICAS and on the air supply control panel. The air supply bite module is located in the main equipment center. The air supply bite module receives information from the left and right bleed air supply system components, air/ground relays, air driven hydraulic pump operation, and both bleed air control cards. The air supply bite module can be interrogated for system faults when the engines are not operating. The module has memory of up to eight flights.

490° F

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PRESSURE INDICATION SYSTEM - AIR SUPPLY DUCT PRESSURE INDICATION Description The right and left air supply duct transmitters are connected to short sensing lines to monitor air pressure on either side of the distribution system. Output signals from these transmitters are routed to the duct pressure indicator and to the two EICAS computers. Operation The pressure transmitters are powered by 28 volts dc from the L and R dc buses. In the pressure transmitters, pressure variations cause a bellows to move the wiper arm of a potentiometer. The resultant voltage from the potentiometer is amplified and then routed to an EICAS computer where it is processed for display on the lower EICAS display unit. The transmitter voltages are also routed to a dual air supply duct pressure indicator which is powered by 115 volts ac from the left 115 volt ac bus. The signal voltages vary from 0.4 to 5.2 volts dc for the pressure range of 0-80 psi. The signal from each pressure transmitter is processed by a servo amplifier. The servo amplifier powers a torque motor which in turn rotates the left or right indicating needle, as appropriate. Whenever the input voltage changes, the torque motor will rotate the display needle until the servo amplifier's input signal is nulled out by a voltage from the rebalance potentiometer which is equal in amplitude, but opposite in polarity.

28V DC L BUS C1332 LEFT AIR SUPPLY DUCT PRESS 28V DC R BUS C1342 RIGHT AIR SUPPLY DUCT PRESS IND 115V AC L BUS C4221 AIR SUPPLY DUCT PRESS IND PWR

POWER SUPPLY DC B

POWER SUPPLY

L AIR SUPPLY DUCT PRESS TRANSMITTER

P11 OVERHEAD CIRCUIT BREAKER PANEL SERVO AMP

TORQUE MOTOR

DC

C CR O

REBALANCE POTENTIOMETER

60

20

S

POWER SUPPLY

80

T A L

A

0

SERVO

TORQUE MOTOR

AMP

ECS/MSG

S

DC

DUCT PRESS PSI

40

LEFT EICAS COMPUTER

+ -

B

+ -

DUCT PRESS

L 45

R 35

K

EICAS LOWER DISPLAY UNIT (P2)

U S

R AIR SUPPLY DUCT PRESS TRANSMITTER

DC

RIGHT EICAS COMPUTER

REBALANCE POTENTIOMETER

DUAL AIR SUPPLY DUCT PRESSURE INDICATOR(P5)

TO LEFT COOLING PACK B

TO TAT PROBE HEAT & RAIN REPELLENT

TO FWD CARGO HEAT

V44 L AIR SUPPLY ISLN VLV

V45 R AIR SUPPLY ISLN VLV

L ENG BLEED AIR PNEUMATIC GROUND CONNECTIONS

TO RIGHT COOLING PACK A

R ENG BLEED AIR

V46 C AIR SUPPLY ISLN VLV APU BLEED AIR

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PRESSURE INDICATION SYSTEM - DUCT PRESSURE TRANSMITTERS Purpose The pressure transmitters provide a variable signal to the dual duct pressure gage, (P5) and to the EICAS computers for duct pressure indication. Location The transmitters are mounted to support brackets near access doors forward of the Air Conditioning compartments. Description The transmitters consist of a housing with an electrical connector on one end and an pneumatic connector on the other. There is an amplifier, a potentiometer, and a bellows assembly contained in the housing.

FROM LEFT ENGINE

SEE

DUCT PRESSURE TRANSDUCERS

D

FROM LEFT ENGINE

DUCT PRESSURE TRANSDUCERS

LEFT DUCT PRESSURE TRANSDUCER

PNEUMATIC DUCT (REF)

FROM APU FWD

FROM RIGHT ENGINE

D

RIGHT DUCT PRESSURE TRANSDUCER

FROMAPU FROM APU

2 1 1

141 - 999

2

101 - 139

FWD

D

1 141 - 999

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AIR SUPPLY BITE SYSTEM - OPERATIONAL CHECKS Description The air supply bite module uses 115 volt ac power from the left bus. When both engines are operating, operational logic is provided to the bite module for left and right system monitoring. Operation High Pressure Shutoff Valve The module will fault the shutoff valve for the following: • High stage pressure greater than 127 psi (pressure switch No.1, PHH open) and the valve disk is open (position switch). • High stage pressure is less than 62 psi (pressure switch No. 2, PHL closed) and the valve disk is closed (position switch). • High pressure controller solenoid with OFF signal and the valve disk is open (position switch). High Pressure Controller The module will fault the controller for the following: • High stage pressure greater than 127 psi (pressure switch No. 1, PHH) and control pressure is greater than 14 psi (PC servo pressure switch). • High stage pressure less than 62 psi (HP pressure switch No. 2, PHL) and control output pressure not within supply pressure by 20 psi (differential pressure switch, PH-PC). • Controller solenoid OFF signal applied and servo pressure is greater than 14 psi (PC servo pressure switch). Pressure Regulating Valve and Controller The module will fault the valve/controller for the following: • Overpressure switch closed and the valve disk open (position switch). • Controller solenoid OFF signal applied and the valve open (position switch).

Pressure Regulating and Shutoff Valve • The module will fault the pressure regulating and shutoff valve for the following: • Solenoid OFF signal applied and the valve disk open (position switch). • Downstream pressure is greater than 60 psi (PR pressure switch No. 1) and the valve disk is open (position switch). • Downstream pressure less than 20 psi (PR pressure switch No. 2) and valve disk is closed (closed position switch). Inhibits test if temperature is greater than 420° F (216° C), (fan air bite temperature sensor) or if the high pressure shutoff valve is closed and high stage pressure is less than 62 psi. • Temperature greater than 550° F (287° C) (fan air bite temperature sensor). Fan Air Modulating Valve The module will fault the valve for the following: • Temperature is greater than 430° F (221° C), as sensed by the fan air bite temperature sensor, and the valve is not open as sensed by the position switch. The valve fault is inhibited if the fan air temperature sensor is faulty. • Temperature less than 265° F (129° C) as sensed by the fan air bite temperature sensor, and the valve is not closed, as sensed by the position switch. The valve fault is inhibited if the fan air temperature sensor is faulty. Fan Air Temperature Sensor The module will fault the sensor for the following: • Temperature less than 265° F (129° C) as sensed by the fan air bite temperature sensor and pressure is less than 9.25 psi as sensed by pressure switch No. 1. • Temperature greater than 445° F (229° C), as sensed by the fan air bite temperature sensor, and pressure is greater than 2.25 psi, as sensed by fan air control pressure switch No. 2. Air Supply Bite Module The bite module conducts a self-test using temperature sensors and position switches to test for out-of-range checks, ground position check, and open wire tests.

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AIR SUPPLY BITE SYSTEM - GROUND CHECKS Description/Operation The air supply BITE system identifies and stores LRU faults that occur within the engine air supply system. The BITE module continuously checks the system operation and identifies components faults. The processor stores this information in a nonvolatile memory for up to eight flights. When power is applied to the module, the main routine activates a self-test. The first one is a comprehensive test, it takes less than two seconds. If the comprehensive test fails, the main routine automatically turns on the BITE module lamp and stores the fault. All other module functions are inhibited when this lamp is on. If the lamp stays on you must replace the Air Supply BITE module. If the lamp goes off, or never came on, the main routine continues. The main routine then starts periodic testing. This is a shorter test. The module will return to the comprehensive test if power is interrupted or if a fault is found. If everything is OK, the main routine will select a mode. It can select from two modes. Operational Check Mode If the airplane is in the air, or there is at least one engine running, the main routine selects the operational check mode. In the operational check mode the module continuously checks to make sure all components in the engine bleed and BITE systems are operating correctly. Any detected faults are stored in memory. The switches and the LED lamps on the front panel of the module are inactive in the operational check mode. Ground Check Mode When the airplane is on the ground with both engines shutdown, the main routine selects the ground check mode. In this mode the module continuously monitors the wiring and BITE components. If they are not in their engine off position, a fault is stored in memory.The front panel switches and lamps are enabled. If faults are detected, BITE stores the faults in its memory, no lamps turn on.

Built-In Test The air supply BITE module incorporates circuitry to isolate functional failures of components due to critical wire and connector failures, as distinguished from component failure, and records intermittent flight failures that may not repeat on the ground. Identification of failed items is stored in the air supply BITE module. Actuation of the PRESS TO TEST switch on the BITE panel will test power to the unit and the function of the panel lights and displays. Actuation of the BITE switch will cause the light of the failed item to be illuminated. Fault indicators are stored in previous fault memory for eight flights, after which they are automatically cleared. Verification Test After replacement of failed LRU, actuation of the VERIFY switch will confirm that the replacement LRU is installed correctly, its basic function is operable and its interfaces have been re-established. If the NO FAULT light illuminates during verification, verification is OK and allows reset of the BITE data store. Failure to pass the verification test is indicated by illumination of the failed LRU light. Reset During reset, all "BITE STEP" faults are cleared from nonvolatile memory. The "VERIFY" switch must be pressed and the "NO FAULT" light illuminated before the "RESET" switch is pressed.

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