ATA 36 Pneumatics PDF Issue 6 January 2023

BOMBARDIER DHC 8-400 (PWC PW150) ATA 36 - PNEUMATICS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY B1/B2 MAINTENANCE TRAINING MANUAL Issue 6 - January 2023 Page 1 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS Bleed air sharing can occur only when both engines are in operation an...

BOMBARDIER DHC 8-400 (PWC PW150) ATA 36 - PNEUMATICS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY B1/B2 MAINTENANCE TRAINING MANUAL Issue 6 - January 2023 Page 1 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS Bleed air sharing can occur only when both engines are in operation and both digital channels are functional. GENERAL DESCRIPTION The pneumatic systems control and distribute bleed air for: • • • Pressurization of the cabin and flight compartments Conditioned air for interior temperature controls Avionics equipment cooling Bleed air for the pneumatic systems is supplied by the engines or by an optional Auxiliary Power Unit (APU). The APU supplies the ECS with bleed air before engine start. The engines normally supply bleed air for pneumatics after engine start. The APU can supply bleed air if the engine BLEED switches are both set to OFF. The Bleed Air System (BAS), is part of the Environmental Control System (ECS) which supplies conditioned air to the flight and cabin compartments. Bleed air flows through ducts from each engine along the wing forward spar, through the dorsal fin then to the air conditioning pack. The left digital channel of the Electronic Control Unit (ECU) controls the bleed air system of No.1 engine, and the right digital channel controls the bleed air system of No.2 engine. The left and right digital channels each have analogue channel backup. If a digital channel fails, the related analogue channel will control that system. The ECU uses a differential pressure (flow) sensor to measure the bleed air flow through each Nacelle Shut-Off Valve (NSOV). The ECU uses this bleed airflow data to balance the flow of bleed air from both engines to the ECS. Each digital channel modulates its Nacelle Flow Control and Shut-off Valve (NFCSOV) to maintain 50% total bleed air flow from its engine. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 2 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 3 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED FLOW CONTROL Bleed air flow to the ECS is controlled by the BLEED switches and BLEED flow selector on the AIR CONDITIONING control panel. The BLEED air flow control selector has three positions, MIN, NORM and MAX. After engine start, the bleed control switches can be selected ON, and the BLEED control selector turned to the desired position. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 4 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED FLOW VERSUS SELECTION AND RATING TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 5 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED FLOW CONTROL CONTINUED Bleed air is supplied from the high pressure P3 port or the low pressure P2.7 port of each engine to the ECS. At low power settings, bleed air comes from the HP port, and at high power settings (takeoff climb and cruise) from the LP port. After the left and right engines have started and BLEED 1 and 2 switches have been selected ON, the ECU opens the NFCSOV. The ECU uses data from the engine mounted P3 (HP) bleed air sensor and the Air Data Units (ADU) to select the bleed port. If HP bleed air is within pressure limits, the ECU opens the High Pressure Shut-Off Valve (HPSOV). This lets bleed air from the HP port flow through the pre-cooler to the ECS, deice system and oil cooler ejectors. When the HP bleed air has become too hot for use by the ECS, de-ice system and oil cooler ejectors, the temperature of the HP bleed air is lowered in the pre-cooler by cooling air from the P2.2 bleed port. The ECU opens the P2.2 Shut-Off Valve (SOV), based on the setting of the pre-cooler temperature switch. This will permit the flow of P2.2 bleed air through the pre-cooler to cool the P3. The cooled HP bleed air that leaves the pre-cooler, flows through the NFCSOV and then through bleed air ducts in the wing. When the HP bleed air temperature is correct, the ECU closes the P2.2 SOV. The pre-coolers operate independently on each side of the aircraft. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 6 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM SYNOPTIC DIAGRAM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 7 of 60 BOMBARDIER DHC 8-400 (PWC PW150) • • • • • • • • • • • PNEUMATIC SYSTEMS BLEED AIR GENERAL DESCRIPTION The bleed air system supplies compressed air for: • • • • • Air conditioning Airframe de-icing Door seal pressurization Engine oil cooler ejectors Cabin and flight compartment pressurization Pre-cooler Over-temperature switch Nacelle Flow Control Shut-Off Valve Nacelle Duct Leak Over-temperature Switch P2.2 Shut-Off Valve Overpressure Switch Wing Differential Pressure Sensor Wing Duct Check Valve APU Differential Pressure Sensor Aft Fuselage Duct Leak Over-temperature Switches APU Check Valve The bleed air system delivers air to the: • • • Air conditioning system De-ice system Oil cooler ejectors The BLEED switches on the AIR CONDITIONING control panel and the APU control panel determine the bleed air source. The system is protected from: • • • Over-temperature Over-pressurization Leakage The left nacelle bleed air system is identical to the right nacelle system. Airframe de-icing air is supplied through either the high pressure or low pressure bleed air port. The de-icing air is passed through the pre-cooler to protect the components of the deice system from overheating. The Bleed Air System (BAS) is part of the Environmental Control System (ECS) which supplies conditioned air to the flight and cabin compartments of the aircraft. The BAS has these components: • • • Bleed Stage Pressure Switch High Pressure Shut-Off Valve Pre-cooler Temperature Switch TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 8 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM DIAGRAM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 9 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR GENERAL DESCRIPTION CONTINUED The BAS has a series of air ducts which transfer bleed air from the engines or the Auxiliary Power Unit (APU) to the Environmental Control System (ECS). The Bleed Air System (BAS) starts in the nacelles, where it collects compressed air from the engines. In the nacelles, the BAS has valves, heat exchangers, sensors and switches to select, monitor and condition the bleed air drawn from the left and right engines. Bleed air flows from the two engines through the ducting on each wing forward spar to the wing centre section. The wing bleed air ducts, one from each nacelle, join at the wing centre section to combine the two engine bleed air flows into one air flow. Each wing bleed air duct has an over pressure switch, a differential pressure sensor and a check valve to monitor and control the supply of engine bleed air. The ducts have shrouds and sensors to contain and detect leaks. The next section of bleed air ducting transfers the combined engine bleed air flow from the wing centre section through the dorsal fin of the fuselage to the tail. This section of air ducts also has a shroud to contain air leaks. The last section of the BAS is in the aft fuselage. This section transfers the bleed air from the engines or from the Auxiliary Power Unit (APU) to the air conditioning pack. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 10 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 11 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS and does not flow through the pre-cooler. However, the low pressure air does flow through the deice part of the De-ice Pre-cooler before it flows to the deice system. BLEED AIR The airflows from the high and low pressure engine bleed ports join upstream of the nacelle shut-off valve. Shrouds are installed around the P3 bleed air ducts, between the engine and the pre-cooler, to reduce the surface temperature. SYSTEM OPERATION The De-ice Pre-cooler cools both the P3 and the P2.7 air before the air flows to the de-ice system. It also use the P2.2 air to cool the P3 or the P2.7 air. The bleed air system in each nacelle has these units: • • • • • • • • • Pre-cooler Bleed stage pressure switch High pressure shut-off valve High pressure venturi Low pressure check valve Nacelle shut-off valve Pre-cooler temperature switch Over-temperature switch Oil cooler ejector shut-off valve The bleed air system collects compressed air from the high pressure (HP P3 stage) or low pressure (LP P2.7 stage) bleed ports of each main engine. The use of either the HP port or the LP port depends on the engine power setting. The ECU uses pressure data from the engine mounted P3 bleed air and environmental data from the Air Data Units (ADU) to determine which port supplies the bleed air. If the P3 bleed air is not too high in pressure, the ECU opens the High Pressure ShutOff Valve (HPSOV). This allows bleed air from the P3 port to supply the Environmental Control System (ECS). A flow-limiting venturi in the high pressure duct limits the maximum flow of high stage (P3) bleed air drawn from each engine. A Pre-cooler Temperature switch on the input to the High Stage Pre-cooler senses when the temperature of P3 air is too high and will cause the P2.2 Shut-off valve to open. This allows P2.2 air to flow through the High Stage Pre-cooler, cooling the P3 air. The bleed air from the low pressure engine port is cooler than the high pressure air TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 12 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM (SHOWN P3 REGULATED) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 13 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR SYSTEM OPERATION CONTINUED Selection of the BLEED 1 and/or BLEED 2 toggle switches on the flight compartment AIR CONDITIONING control panel provides a signal to the ECU to open the Nacelle Flow Control Shut-Off Valve (NFCSOV) in the related engine. The Environmental Control System (ECS) Electronic Control Unit (ECU) modulates the NFCSOV to provide engine air sharing. The bleed air then flows through the wing duct check valves to the ECS pack. The Wing Duct Check Valves prevent the bleed air of one engine from affecting the other engine. The single rotary BLEED flow selector is used to regulate the bleed air flow rate by the ECU. The Auxiliary Power Unit (APU) also supplies compressed air to the bleed air system for ground operation. Selection of the bleed air (BL AIR) switch-light on the APU CONTROL panel turns on the APU bleed air. APU bleed air can only be used when both of the engine bleeds are turned off. Bleed air can be supplied from either the high pressure P3 port or the low pressure P2.7 port on each engine. A check valve in each engine P2.7 bleed duct prevents the back-flow of high pressure P3 bleed air into the P2.7 bleed port. Each engine must be operating to supply bleed air to its oil cooler ejector. The deice system will receive bleed air if one or both engines are operating. Check valves in the wing ducts prevent the use of bleed air from the APU for the deice system and oil cooler ejectors. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 14 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM (SHOWN P2.7 REGULATED) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 15 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS If the pack switch is set to MAN (manual mode), the left digital channel responsible for the auto mode transfers control of the left nacelle shut-off valve to the left analogue channel. This also applies to the right digital channel and right analogue channel which control the right nacelle flow control shut-off valve. BLEED AIR SYSTEM OPERATION CONTINUED The ECU is the heart of the Bleed Air System for control and monitoring. The Electronic Control Unit (ECU) has two channels left and right. Each channel has a digital automatic portion that has a power supply, processor, low level Input/Output (I/O) and motor driver board. Each channel also has an analogue manual portion that acts as a limited function backup to the digital channel. The left digital channel controls the left side pneumatics, and the right digital channel controls the right side pneumatics. If one digital channel loses power or fails, the analogue channel will provide backup control of the nacelle shut-off valve, the bleed protective devices and the bleed Caution indications. On the failed side, only the Low Pressure bleed air is available, but the safety functions are retained. The analogue channel takes control of the functions only when the digital channel malfunctions or if the PACKS switch on the AIR CONDITIONING control panel is set to MAN (manual). The analogue channels keep the nacelle shut-off valves fully open (50 mA drive current to the torque motors). The protection circuits remain active but balanced bleed air (bleed sharing) from both engines is not possible. This is because the analogue channels do not have differential pressure sensors inputs to sense bleed air flow. The analogue channels keep the nacelle shut-off valves fully open during these conditions: • • • Failure of one digital channel A or B Failure of both digital channels Pack selected to manual The left digital channel and right analogue channel receive electrical power from the 28V DC L MAIN bus. The right digital channel and left analogue channel receive electrical power from the 28V DC R MAIN bus. This permits continued left and right channel control if one 28V DC bus loses power. For example, if the left digital channel loses electrical power because of bus failure, the left analogue channel is still powered by the remaining bus. The left digital channel and left analogue channel share control of the left nacelle flow control shut-off valve. If the left digital channel loses power or fails, the left analogue channel automatically takes control of this valve. The right digital channel and right analogue channel share control of the right nacelle flow control shut-off valve. If the right digital channel loses power or fails, the right analogue channel automatically takes control of this valve. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 16 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR CONTROL BLOCK DIAGRAM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 17 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS nacelle shut-off valves to keep the air supply from each main engine equal. BLEED AIR Under analogue control, bleed flow control is transferred to the Pack FCSOV (PFCSOV). During digital control, the ECU modulates the PFCSOV to give a flow slightly higher than the combined engine flow. SYSTEM OPERATION CONTINUED Bleed air selection and de-selection are selected from the AIR CONDITIONING control panel or the APU control panel. The digital channel in control of shared functions determines if engine bleed or APU bleed is to be used, from the position of the three bleed switches. The digital channel in control is determined by WOW. This ensures that there is a minimum flow change should a transfer to analogue control take place. When the APU is supplying bleed air, flow control is normally at the PFCSOV, but may be degraded by the APU FADEC based on the APU EGT. Selection of the BLEED 1 and BLEED 2 switches on the AIR CONDITIONING control panel turns on the left and right engine bleed air systems respectively. The rotary BLEED MIN/NORM/MAX selector is used to control the amount of bleed air flow. Selection of the BL AIR switch, on the APU CONTROL PANEL, turns on the APU bleed air system. Selection of the BLEED 1 and BLEED 2 switches causes the ECU to open both nacelle shut-off valves. This allows bleed air to flow from the left and right engines. Selection of the OFF switch causes the ECU to close the nacelle shut-off valve. This stops the flow of engine bleed air to the ECS. While bleed air to the ECS is stopped, low pressure P2.7 bleed air from each engine will still flow to the deice system and the oil cooler ejectors. The pack air flow is selected on the BLEED MIN/NORM/MAX selector. For operation with both engines and both packs operating, each ECU digital channel regulates its nacelle shut-off valve for minimum, normal, or maximum pack air flow. The flight condition determines the amount of flow for each of these levels. The ECU also regulates the nacelle shut-off valve in each nacelle to supply 50% of the total flow demand. This ensures equal flow sharing between each engine. The ECU receives signals from the left and right differential pressure sensors which are located in the bleed air duct just after the nacelle shut-off valves. The ECU modulates the left and right TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 18 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR CONTROL BLOCK DIAGRAM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 19 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS The motor driver has output interfaces for the torque motors and the discrete outputs. BLEED AIR The analogue backup has its own power regulation circuitry, thermistor, potentiometer and discrete inputs. It also has torque motor and discrete outputs. ELECTRONIC CONTROL UNIT The analogue backup provides duct temperature control, ECS (pack) shutdown logic and bleed system on/off control. The Electronic Control Unit (ECU) controls and monitors the bleed air system for the following: • • • • • Bleed flow Bleed pressure Bleed temperature Bleed differential Bleed duct leak The ECU uses sensors and switches to monitor temperature, pressure, flow rates and valve positions. The ECU responds to the pilot commands to configure the Bleed Air System for bleed source selection. The ECU and the Bleed Air System have redundant configurations to permit continued ECS operation with mechanical and electrical component malfunctions. The ECU is installed in the avionics bay under the centre floor boards. The ECU has two channels (left and right). Each channel has a digital (automatic) part that has a power supply, processor, low level Input/Output (I/O) and motor driver board. Each channel also has an analogue channel manual part that acts as a limited function backup to the digital channel. The power supply provides all the internal voltages for the digital system. It supplies the power for the solenoid drivers and the pressure sensor excitations. The processor contains the microprocessor RAM and EEPROM memory. It also has the ARINC 429 and RS422 communication circuitry. The low level I/O board has the Analogue/Digital interface for the thermistors, RTD, potentiometer and pressure signal inputs. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 20 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - ECS ELECTRONIC CONTROL UNIT (ECU) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 21 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR BLEED STAGE PRESSURE SWITCH The Bleed Stage Pressure Switch commands open the HPSOV when HP air is less than the switch actuation pressure to ensure sufficient de-ice pressure. The switch: • • Opens at 82 psi (565 kPa) increasing pressure Closes at 77 psi (531 kPa) decreasing pressure The bleed stage pressure switch is installed on a bracket aft of the pre-cooler. The switch controls the High Pressure Shut-off Valve (HPSOV) independently of the ECU when engine bleed is selected off, or de-ice is selected on. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 22 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED STAGE PRESSURE SWITCH TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 23 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR HIGH PRESSURE SHUT-OFF VALVE The High Pressure Shut-off Valve selects the engine bleed port that is used to meet ECS flow and pressure requirements. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 24 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - HIGH PRESSURE SHUT-OFF VALVE (HPSOV) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 25 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR HIGH PRESSURE SHUT-OFF VALVE The High Pressure Shut-off Valve (HPSOV) is a pneumatically operated, torque motor actuated butterfly valve. The HPSOV is installed in line with the high pressure ducting between the engine (P3) bleed air port and the pre-cooler. The high pressure ducting in the nacelle is enclosed in a composite shroud from the bleed port to the HPSOV. This reduces the possibility of ignition in the event of a fuel spillage. The valve has a wire mesh filter upstream of the torque motor to protect the servo from contamination. The valve also has a locking pin. The pin locks the valve in the closed position to allow the servo air to vent to ambient. HPSOV SWITCHING SCHEDULE With the flight compartment Bleed Switch in the OFF position, HPSOV control is given to the Bleed Stage Pressure Switch. This will prevent over-pressurizing the engine bleed system. With the flight compartment Bleed Switch in the ‘ON’ position, HPSOV control is given to the ECSECU. The ECSECU will change the operating point of the HPSOV. Based on the P3 pressure from a engine mounted P3 sensor, via FADEC and the input output processors, the ECSECU will be operating the HPSOV on the basic schedule. With aircraft in a decent mode of greater than 450 ft/min the ECSECU will set a higher operating point for the HPSOV to maintain maximum air available to the environmental system. When the wing de-icing system has been activated, the control of the HPSOV is given to the Bleed Stage Pressure Switch. This will insure that sufficient bleed pressure is available to the de-icing system at all altitudes and engine power settings. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 26 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - HPSOV CONTROL SCHEMATIC (SHOWN BLEED ON) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 27 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR HIGH PRESSURE SHUT-OFF VALVE CONTINUED HPSOV SWITCHING SCHEDULE CONTINUED The HPSOV opens when the torque motor is energized. When the HPSOV is in the open position, it allows P3 air to flow through to the pre-cooler to supply the ECS and/ or the deice systems. The ECU uses (P3) information supplied by FADEC to control the opening and closing of the HPSOV when deice is selected off and engine bleed is selected on. When the bleed air switches on the air conditioning panel are selected off, or de-ice is selected on, the control is removed from the ECU and the bleed stage pressure switch will open or close the HPSOV. The HPSOV has a closed position micro-switch that informs the ECU of the status of the valve (BIT). If an over-temperature, overpressure or bleed leak occurs in the system, the ECU will close the HPSOV automatically. If electrical power is lost to the valve, the torque motor will cause the valve to pneumatically close. Also, if there is a loss of bleed air, the spring in the actuator will close the valve. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 28 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - HPSOV SWITCHING SCHEDULES TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 29 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR PRE-COOLER TEMPERATURE SWITCH The Pre-cooler Temperature Switch is used to open the P2.2 shut-off valve when high pressure air is being used and it requires cooling. The pre-cooler temperature switch is installed in the ducting between the HPSOV and the pre-cooler. The pre-cooler switch monitors the temperature of the engine bleed air entering the pre-cooler. If the bleed air entering the pre-cooler is greater than 550°F (288°C), the switch will open sending a signal to the ECU to open the P2.2 shut-off valve. This allows cooling P2.2 air to pass through the pre-cooler. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 30 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - PRECOOLER TEMPERATURE SWITCH TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 31 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR PRE-COOLER The Pre-cooler reduces the temperature of the bleed air using the P2.2 air for cooling. The pre-cooler is installed on the upper forward face of the nacelle mid-frame. It is a two-part plate and fin, cross flow, air to air heat exchanger which uses low temperature P2.2 bleed air to cool high pressure P3 bleed air. A smaller de-ice pre-cooler, integral to the high stage pre-cooler, reduces the temperature of the bleed air sent to the deice system. This pre-cooler uses a continuous flow no flow control valves of P2.2 bleed air and operates during selection of either P3 or P2.7 bleed air. The flow of P2.2 bleed air through the de-ice pre-cooler absorbs heat from the P3 or P2.7 bleed air. This reduces the temperature of the P3 or P2.7 bleed air to acceptable levels, before it flows to the deice system. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 32 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - PRECOOLER TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 33 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR OVER-TEMPERATURE SWITCH The Over-temperature Switch is used to signal the ECS ECU to shutdown the bleed system in the event of an over-temperature condition downstream of the bleed precooler. The over-temperature switch is installed upstream of the Nacelle Flow Control ShutOff Valve (NFCSOV). It is a protective switch that monitors bleed air temperature. If the temperature of the bleed air is greater than 660°F (349°C), the over-temperature switch will open. This sends a signal to the ECU to close the nacelle flow control shutoff valve, the HPSOV and the P2.2 valve for the affected side. The ECU will then turn on the related BLEED HOT caution light and log a fault code in the Central Diagnostics System (CDS). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 34 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - OVERTEMPERATURE SWITCH TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 35 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR NACELLE FLOW CONTROL AND SHUT-OFF VALVE The Nacelle Flow Control and Shut-off Valve is used for on/off control of the pneumatic system flow and for modulation of the flow for the purpose of bleed flow sharing. The nacelle flow control shut-off valve is a pneumatically operated, torque motor actuated butterfly valve. The valve is installed in line with the pre-cooler outlet duct and the wing ducting. The valve has a wire mesh filter upstream of the torque motor to protect the servo from contamination. The valve also has a locking pin, that locks the valve in the closed position to allow the servo air to vent to ambient. Selection of the BLEED 1 and/or BLEED 2 switches on the AIR CONDITIONING control panel opens the related NFCSOV. The ECU uses this valve to control the flow of bleed air to the ECS. The ECU regulates the NFCSOV according to the settings of the BLEED, PACKS and MIN/NORM/MAX switches, on the AIR CONDITIONING control panel. The ECU digital channel regulates the NFCSOV in each nacelle to supply 50% of the total flow demand. This ensures equal flow sharing between each main engine. The NFCSOV has a closed position micro-switch which informs the ECU of the status of the valve (Bit). If electrical power is lost to the valve, the torque motor will cause the valve to pneumatically close. Also if there is a loss of bleed air, the spring in the actuator will close the valve. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 36 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - NACELLE FLOW CONTROL SHUT-OFF VALVE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 37 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR NACELLE DUCT LEAK O/TEMPERATURE SWITCH The Nacelle Duct Leak Over-temperature Switch shuts down the related bleed system supply if it senses a duct leak. The nacelle duct leak over-temperature switch is installed on a bracket next to the nacelle shut-off valve, and is connected to the shroud outlet with rigid tubing. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 38 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - DUCT LEAK OVERTEMPERATURE SWITCH TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 39 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR NACELLE DUCT LEAK O/TEMPERATURE SWITCH CONTINUED This switch detects a bleed air leak in the front spar duct system. If the temperature in the ducting is greater than 360°F (182.2°C), the switch opens sending a signal to the ECU to close the related NFCSOV and HPSOV and the P2.2 valve. The ECU turns on the related BLEED HOT caution light and also sends a fault code to the Central Diagnostic System (CDS) identifying a duct leak. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 40 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - LEAK DETECTION CONCEPT SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 41 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR P2.2 SHUT-OFF VALVE The P2.2 Shut-off Valve is used for on/off control of the P2.2 bleed port air supplied to the pre-cooler for cooling of HP supply air. The P2.2 shut-off valve is a pneumatically operated, torque motor actuated butterfly valve. The valve has a wire mesh filter upstream of the torque motor to protect the servo from contamination. The P2.2 shut-off valve is installed in line with the P2.2 low pressure ducting and the P2.2 inlet at the bottom of the pre-cooler. When opened by the ECU P2.2 air is routed to the pre-cooler. Operation is controlled by the pre-cooler inlet temperature switch operation. The valve has two closed position micro-switches that give valve position information to the ECU and to Full Authority Digital Electrical Control (FADEC). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 42 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - P2.2 SHUT-OFF VALVE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 43 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR OVERPRESSURE SWITCH The Overpressure Switch shuts down the bleed system to prevent damage caused by over-pressurization. The overpressure switch is installed on a bracket in the wing leading edge, and is connected to the bleed air ducting with rigid tubing. It is a protective switch that monitors nacelle bleed pressure. If the pressure in the nacelle ducting is greater than 100 psi (690 kPa), the overpressure switch will close. This sends a signal to the ECU to close the affected NFCSOV, the HPSOV and the P2.2 valve. The ECU causes the related BLEED HOT caution light to come on. A fault message is logged in the CDS. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 44 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - OVERPRESSURE SWITCH TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 45 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR WING DIFFERENTIAL PRESSURE SENSOR The Wing Differential Pressure Sensor measures the pressure differential between the inlet and flow sensing venturi throats mounted in the wing ducting. The differential pressure and the venturi characteristics are used to compute the flow through the venturi. The wing differential pressure sensor is installed on a bracket in the wing root leading edge, and is connected to bleed air ducting with rigid tubing. The differential pressure sensor has two pressure ports. One port senses the pressure upstream of the wing venturi and the other port senses the pressure at the throat of the venturi. The ECU uses a differential pressure (flow) sensor to measure the bleed air flow through each nacelle flow control shut-off valve. The ECU uses this bleed airflow information to balance the flow of bleed air from both engines to the ECS. Each digital channel in the ECU modulates its nacelle flow control shut-off valve to maintain 50% total bleed air flow from its engine. Bleed sharing can occur only when both engines and both digital channels are operating. There is no analogue channel function for bleed air sharing. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 46 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - WING DIFFERENTIAL PRESSURE SENSOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 47 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR WING DUCT CHECK VALVE The Wing Duct Check Valve prevents reverse flow in the bleed supply line from a nacelle. The wing duct check valve is a dual flapper, spring loaded check valve. The valve is installed in the bleed air ducting along the wing leading edge. It is held open by bleed air from the engine. The check valve closes during single engine or APU operation, to prevent bleed air from flowing into the bleed air ducting. The check valve also prevents reverse flow into both engine bleed air systems when the APU is supplying the bleed air. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 48 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - WING DUCT CHECK VALVE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 49 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR APU DIFFERENTIAL PRESSURE SENSOR The APU Differential Pressure Sensor measures the pressure differential between the inlet and throat sensing venturi mounted on the APU bleed air ducting. The differential pressure and the venturi characteristics are used to compute the flow through the venturi. The APU differential pressure sensor is installed on a bracket on the APU bleed air ducting in the aft fuselage. It is connected to the bleed air ducting by rigid tubing. The differential pressure sensor has two pressure ports. One port senses the pressure upstream of the APU venturi and the other port senses the pressure at the throat of the venturi. The differential pressure data is sent to the ECU. The ECU uses this differential pressure and the temperature data to regulate the bleed air flow through the pack flow control and shut-off valve. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 50 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - APU DIFFERENTIAL PRESSURE SENSOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 51 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR AFT FUSELAGE DUCT LEAK OVER-TEMPERATURE SWITCHES The Aft Fuselage Duct Leak Over-temperature Switches detect a bleed air leak in the engine or APU bleed air ducting near the air conditioning pack inlet. Two aft fuselage duct leak over-temperature switches are installed on a bracket on the aft fuselage tee duct. If the temperature in the ducting is greater than 360°F (182.2°C), the switch contacts will open. If either sensor detects a leak, the ECU will shut down both nacelle bleed air systems. Also, a relay system will interrupt the bleed air demand to the APU FADEC, which will close the APU bleed valve. The ECU will turn on both BLEED HOT caution lights and record a fault code. The APU FADEC will close the APU bleed valve. The BL AIR OPEN advisory light on the APU panel goes OFF. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 52 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - AFT FUSELAGE DUCT LEAK OVERTEMPERATURE SWITCH TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 53 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR APU CHECK VALVE The APU Check Valve is a redundant valve that prevents reverse flow to the APU during normal operation. The primary means is the APU bleed valve. The APU check valve is a dual flapper, spring loaded check valve. The valve is installed in line with the APU bleed air ducting in the aft fuselage. It is held open by bleed air coming from the APU. It allows bleed air to flow to the air conditioning pack but prevents reverse flow to the APU from the engine bleed air system. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 54 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - APU CHECK VALVE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 55 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BLEED AIR CONTROLS AND INDICATIONS The AIR CONDITIONING panel has the following controls relating to the Bleed Air System: • • • BLEED 1 switch BLEED 2 switch BLEED MIN/NORM/MAX selector BLEED 1 SWITCH Selection of the BLEED 1 switch sends a signal to the ECU. The ECU opens the left nacelle flow control shut-off valve to supply bleed air to the system. BLEED 2 SWITCH Selection of the BLEED 2 switch sends a signal to the ECU. The ECU opens the right nacelle flow control shut-off valve to supply bleed air to the system. BLEED MIN/NORM/MAX SELECTOR The rotary BLEED MIN/NORM/MAX selector is used to control the amount of bleed air flow. Selection to MIN causes the ECU to modulate the nacelle flow control shut-off valve to the min position for air flow. Selection to NORM causes the ECU to modulate the nacelle flow control shut-off valve to the normal position for air flow. Selection to MAX causes the ECU to modulate the nacelle flow control shut-off valve to the maximum position for air flow. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 56 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - BLEED AIR SYSTEM, AIR CONDITIONING CONTROL PANEL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 57 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS respective BLEED switches and/or the APU BL AIR switch-light are cycled through OFF. BLEED AIR CONTROLS AND INDICATIONS FAILURE AND SYSTEM MALFUNCTION ANNUNCIATORS The Bleed Air System has the following caution lights: • • #1 BLEED HOT #2 BLEED HOT The #1 BLEED HOT caution light comes on when: • • • Left Bleed Overpressure Switch detects a pressure of greater than 100 psig Left Bleed Over-temperature Switch detects a temperature of greater than 660°F (349°C) Left Nacelle Duct Leak Over-temperature Switch detects a temperature of greater than 360°F/182°C The #2 BLEED HOT caution light comes on when: • • • Right Bleed Overpressure Switch detects a pressure of greater than 100 psig Right Bleed Over-temperature Switch detects a temperature of greater than 660°F (349°C) Right Nacelle Duct Leak Over-temperature Switch detects a temperature of greater than 360°F (182°C) Both #1 & #2 BLEED HOT caution lights come on when: • • Aft Duct Leak Over-temperature Switch detects a temperature greater than 360°F (182°C) APU Duct Leak Over-temperature Switch detects a temperature of greater than 360°F (182°C) A BLEED HOT caution light will remain ON until the cause is removed and the TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 58 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS - CAUTION AND WARNING PANEL, BLEED HOT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 59 of 60 BOMBARDIER DHC 8-400 (PWC PW150) PNEUMATIC SYSTEMS BIT logic can also examine the signals from the pressure and temperature sensors to determine if they operate correctly. INTERFACES When the ECU detects a BIT fault, an applicable fault code is stored in its non-volatile fault memory. A failure detected in a digital channel causes the ECU to transmit the fault code signal to the Central Diagnostic System (CDS) that will bring on the ECS AUTO FAIL light on the maintenance panel. The Bleed Air System interfaces with the following systems: • • • • • • Air conditioning Airframe de-icing Engine oil cooler ejectors Air Data unit Cabin and flight compartment pressurization Engine FADEC CENTRALIZED DIAGNOSTIC SYSTEM (CDS) The Centralized Diagnostic System (CDS) monitors, records, tests, and shows the condition of the pneumatic systems. Inside the ECU, the digital channels use an RS422 digital data bus to communicate with each other. The ECU uses the ARINC 429 digital data bus to communicate to other aircraft systems. The ARINC 429 receivers of both digital channels are connected to the aircraft wiring. The CDS lets aircraft maintenance personnel: • • • Read malfunction reports from last or previous flight legs Perform fault isolation Read the part number of the monitored Line Replaceable Units (LRU) NOTE: Only the ARINC 429 transmitter of the left digital channel is connected to the aircraft wiring. The CDS is used for troubleshooting. It is not approved as the only return-toservice-test after maintenance is completed. Use the procedures described in the Aircraft Maintenance Manual (AMM). SYSTEM TESTS The ECU does high level operational checks of the ECS system as part of continuous BIT. For the ECS, the tests examine that the pack flow is within permitted limits and that the pack discharge temperature is reasonable. Failure of these high level tests causes the ECU to do low level tests to identify the failed component. The ECU also performs self tests on its digital and analogue channels and the applicable interfaces. The high pressure shut-off valves, nacelle shut-off valves and the APU shut-off valve each have a position switch to identify when the valve is closed. The P2.2 SOV has three electrically isolated position switches to identify an open or closed valve position. The digital channels use one of the three switches for its Built-In-Test (BIT). During its BIT, the ECU compares the commanded state (open or closed) of the valve to the actual state identified by the position switch. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 36 - PNEUMATICS Issue 6 - January 2023 Page 60 of 60