ATA 73 - Engine Fuel & Control PDF (Bombardier DHC 8-400, January 2023)

BOMBARDIER DHC 8-400 (PWC PW150) ATA 73 - ENGINE FUEL & CONTROL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY B1/B2 MAINTENANCE TRAINING MANUAL Issue 6 - January 2023 Page 1 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM GENERAL DESCRIPTION The fuel system gives fuel at t...

BOMBARDIER DHC 8-400 (PWC PW150) ATA 73 - ENGINE FUEL & CONTROL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY B1/B2 MAINTENANCE TRAINING MANUAL Issue 6 - January 2023 Page 1 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM GENERAL DESCRIPTION The fuel system gives fuel at the correct pressure and flow to the fuel nozzles. The engine fuel system has these components: • • • • • • • • • • • • • Fuel Oil Heat Exchanger Full Authority Digital Electronic Control (FADEC) Fuel Metering Unit (FMU) with integrated fuel pumps Fuel nozzle adapters Flow divider valve and ecology tank Fuel manifolds Fuel tubes Fuel filter Electrical wiring harness Characterization plug Permanent Magnet Alternator (PMA) Low fuel-pressure-switch Fuel filter impending-bypass switch TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 2 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM LEADING PARTICULARS FUEL PUMPS Low pressure regenerative pump capacity: • • Max fuel flow at 8220 rpm - 4975 pph Max pressure: 151 psid (1041 kPad) High pressure pump capacity: • • 5500 pph 1200 psi (8274 kPa) Inlet pressure: • • • Min - 3.5 psi (24 kPa) Run 50 hours max. with pressure below min. Max - 60 psi (414 kPa) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 3 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM LEADING PARTICULARS CONTINUED TEMPERATURE SENSOR • • Monitors the fuel temperature for the flight compartment indication Air frame supplied TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 4 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM LEADING PARTICULARS CONTINUED FUEL METERING UNIT (FMU) Screens: • • Coarse screen - 0.012 inch (.305 mm) Fine screen - 0.0013 inch (.033 mm) High pressure relief valve: • • Prevents excessive pressure in the FMU Opens at 1450 ± 50 psid (9997 ± 345 kPad) Servo pressure regulator: • • Supply the Metering Valve with regulated servo press Maintains regulated servo supply 220 to 235 psi (1517 to 1620 kPa) above pump interstage pressure backflow filtered 220 to 235 psi (1517 to 1620 kPa) Pressure regulating/motive flow control valve: • • Directs motive flow fuel to MPSOV. Opens at about 10% NH Maintains pressure differential of 40 psid between MV inlet pressure P1 and MV outlet pressure (P2) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 5 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM Vapour venting check valve: • • LEADING PARTICULARS CONTINUED FUEL METERING UNIT (FMU) Pump inlet low pressure switch (airframe): • Metering valve: • • • • • Prevents vapour lock in the FMU that could affect the operation Opens at 2 to 9 psid (14 to 62 kPa) Indicates the FADEC, ECIU, CAS and EMU that the low pressure fuel has dropped below 5.5 ± 0.8 psi (38 ± 5.5 kPa) Controls the fuel flow to the engine Fuel flow (Wf) can vary between 125 pph to 2875 pph Position of the valve is controlled by the FADEC channel A and B. UP INCREASE P2, DOWN - DECREASE P2 LVDT: Linear Variable Differential Transformer. Transmits the metering valve position to FADEC. Dual LVDT for channel A and B Bias to close Metering valve torque motor: • • • Controls the metering valve modulated pressure (PM) to operate the metering valve (up and down movement) Operated by the FADEC channel A and B Spring loaded to close Wf with loss of electrical power Minimum Pressure and Shut Off Valve (MPSOV): • • • Maintains a minimum fuel pressure 250 to 275 psid (1724 to 1896 kPad) in the FMU during low flow condition ex. starting Assists the dual overspeed and shutdown solenoid to start and shutdown the engine Allows the motive flow fuel to supply the motive flow pumps in the system engine and airframe Dual overspeed and shutdown solenoid: • • Used to start and to shutdown the engine Operated by the fire handle airframe TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 6 of 90 BOMBARDIER DHC 8-400 (PWC PW150) INTENTIONALLY LEFT BLANK TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 7 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM DESCRIPTION The fuel is received by the Fuel Metering Unit (FMU) at the regenerative fuel-pump inlet-port from the airframe fuel pumps. The regenerative fuel pump then supplies fuel to the fuel heater. In the fuel heater, the fuel is heated if necessary, filtered and returned to the FMU for metering. The FMU controls the fuel flow to the engine based on demand through the Full Authority Digital Electronic Control (FADEC). The FADEC calculates the amount of fuel to supply based on Nh and Np. The FADEC controls the metering valve in the FMU to control the fuel flow. The metered fuel is then routed to the airframe flow meter and to the flow divider valve through external tubes. Some of the high pressure fuel is returned to the fuel tanks to drive the ejector pumps. The flow divider valve takes metered fuel and distributes the fuel between the primary and secondary fuel manifolds. When the fuel pressure coming from the FMU is low, only the primary manifold is supplied with fuel. As the fuel pressure increases, the secondary manifold is also supplied with fuel. The flow divider valve also recuperates the remaining fuel in the manifolds on engine shutdown. This fuel is then used on the next engine start. The fuel manifolds take the fuel from the flow divider valve and supply the twelve hybrid fuel nozzle adapters. All fuel nozzle adapters are duplex units having both primary and secondary passages. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 8 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - ENGINE FUEL CONTROL SYSTEM SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 9 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM The manifolds deliver the fuel to the nozzles, where it is atomized and sprayed into the combustor. ENGINE FUEL DISTRIBUTION GENERAL DESCRIPTION The engine fuel distribution system, supplies clean fuel to the engine for combustion. The engine receives fuel from the airframe fuel system. The fuel passes through the Fuel Heater and is pumped by an integrated regenerative fuel pump located in the Fuel Metering Unit FMU). The fuel is then metered by the FMU. The metered fuel goes to the Flow Divider Valve which separates it into Primary and Secondary for delivery to the Fuel Nozzles through the Fuel Manifolds. The fuel distribution system has: • • • • • • Fuel Heater Fuel nozzle adapters Flow Divider Valve (FDV) Fuel tubes Fuel manifolds Fuel filter SYSTEM DESCRIPTION Fuel for the engine passes through the oil to fuel heater to prevent ice forming in the fuel. From the fuel heater, the fuel passes through the fuel filter to remove any contaminant particles. The fuel then passes to the flow divider where it is directed to the primary and secondary fuel manifolds. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 10 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - ENGINE FUEL CONTROL BLOCK DIAGRAM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 11 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM reaches 28 ± 3 psid (193 ± 21 kPad). This protects the fuel heater in the event that oil passages are blocked in the fuel heater, or if the oil pressure becomes too high. COMPONENT LOCATION AND DESCRIPTION The oil bypass valve also has a thermal sensor on the fuel side. The thermal sensor keeps the valve fully opened when the fuel temperature is below 90°F (32°C). As the fuel temperature increases above 90°F (32°C), the thermal sensor starts closing the oil bypass valve. FUEL HEATER The fuel heater heats the fuel to prevent the formation of ice crystals. The fuel heater is an integral assembly made of aluminium castings consisting of a heater assembly and a filter assembly. Both assemblies are welded together and reinforced with struts. When the fuel temperature reaches 120°F (49°C), the valve is fully closed and the oil bypasses the heater. The unit also has a fuel temperature probe in the port at the fuel filter outlet. The fuel heater is installed on the left side of the engine on the LP compressor case. It is connected to the FMU through two transfer tubes located on the forward face of the fuel heater. Two transfer tubes located at the bottom of the heater connect it to the main oil-filter-housing. The heat transfer matrix has an aluminium plate/fin that has separate oil and fuel passages. Heat from the oil is conducted through the walls of the passages and heats the fuel that flows through the adjacent fuel passages. An impending bypass switch reads the pressure drop across the unit and sends a signal to the Caution and Warning panel in the flight compartment when a filtration component needs replacement. The switch indicates an impending bypass when the pressure differential is 18 to 21 psid (124.1 to 145 kPad). A 150 micron absolute strainer is installed up-stream of the heat transfer matrix. It is sized to prevent contamination of the matrix and resistant to freezing of the water contained in the fuel. This strainer is protected by a bypass valve equipped with a bypass indicator. The fuel heater incorporates an oil bypass valve on the oil side of the unit which is both pressure and temperature controlled. The oil bypass valve is pressure sensitive and will bypass oil when the oil pressure TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 12 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL HEATER AND TRANSFER TUBES TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 13 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL NOZZLE ADAPTERS The fuel nozzle adapters deliver fuel to the combustion chamber, mix it with air and atomize it for combustion. The twelve fuel nozzle adapters are installed on the turbine support case. The nozzle part of the adapter is inserted into the turbine support case and is directed towards the front of the engine. The nozzle protrudes into the combustion chamber through holes in the dome of the combustion chamber outer-liner. Fuel manifolds connect the fuel nozzles together. All twelve fuel nozzle adapters are duplex units that have both primary and secondary orifices. The primary fuel orifice is located in the centre of the nozzle and the secondary fuel orifices surround the primary orifice. The primary fuel orifices get fuel from the primary fuel manifold. The secondary orifices get fuel from the secondary fuel manifold. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 14 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL NOZZLE ADAPTOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 15 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM COMPONENT LOCATION AND DESCRIPTION CONTINUED FLOW DIVIDER VALVE The flow divider valve (FDV) divides the fuel flow between the primary and secondary fuel manifolds or starting and steady state operation. The flow divider housing is made of cast aluminium and is installed on a bracket located at the bottom of the gas generator case. Two fuel manifolds, left and right, are connected to the FDV. Each fuel manifold has two connections to the FDV • • One for the primary fuel flow One for the secondary fuel flow. A fire shield is mounted around the ecology reservoir for fire resistance purposes. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 16 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FLOW DIVIDER SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 17 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM COMPONENT LOCATION AND DESCRIPTION CONTINUED FLOW DIVIDER VALVE CONTINUED During start, fuel from the FMU flows into the FDV. A pressure regulator maintains primary fuel pressure 125 psi (862 kPa) above the secondary fuel pressure. The excess fuel flow is bled to the secondary manifold through the regulator. Fuel stored in the ecology reservoir is also returned to the manifolds through the action of the ecology piston. A restricted orifice in the ecology circuit slows the transition of the piston this allows the fuel nozzles to operate normally during start. At low fuel flow conditions, fuel is routed to both the primary and secondary manifolds. The pressure regulator maintains a constant pressure differential between them. As fuel flow increases, the FDV equalizes the pressure between the primary and secondary manifolds to limit the maximum pressure of the system. Equalization is maintained up to the maximum flow condition. When the engine is shut down, the fuel left in the fuel manifolds is collected in a 33 cc ecology reservoir integral to the FDV by the action of a piston and a spring. This fuel is used during the next engine start. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 18 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FLOW DIVIDER TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 19 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL FLOW-METER The two fuel tubes route fuel from the Fuel Metering Unit (FMU) to the fuel nozzle adapters. One goes from the FMU to the Fuel Flow-meter. The other goes from the flow-meter to the Flow Divider Valve (FDV). The flow-meter detects fuel flow and sends this information to the flight compartment for display on the ED. FUEL FLOW TRANSMITTER The fuel flow transmitter converts fluid flow into an electrical signal. The fuel flow transmitter measures flow rates from 80 to 2875 lbs/hr (36 to 1304 kgs/ hr). The incoming flow stream is imparted on an impeller by a turbine. The reaction torque of the fuel impeller is directly proportional to the product of mass flow rate and angular velocity. The time difference between start and stop pulses of the transmitter signal is directly proportional to the mass flow rate. The aircraft signal conditioning equipment in the Integrated Flight Cabinet (IFC) multiplies the time difference by a scale factor to determine the mass flow rate of the fuel. This flow rate is shown on the Engine Display (ED). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 20 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL FLOW METER TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 21 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL MANIFOLDS The fuel manifolds deliver fuel to the fuel nozzle adapters. There are two manifolds on the engine. One manifold is on the left side and the other is on the right side. Each fuel manifold connects six fuel nozzle adapters to the FDV. Each fuel manifold consists of six manifold adapters that are equally spaced. Manifold adapters are interconnected by two flexible hoses. One for the primary fuel path and one for the secondary fuel path. The manifold adapters are made of stainless steel and have a dual bore main section, a mounting flange and welded-on fittings where the flexible hoses are crimped. The flexible hoses are surrounded by metallic braiding for strength. They are covered with a silicon-rubber fire sleeve for fire resistance. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 22 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL MANIFOLDS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 23 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL FILTER The fuel filter removes solid contaminants from the fuel stream. The filter is located downstream of the heat transfer matrix and supplies filtered fuel to the engine. The fuel filter bowl and filter element are an integral part of the fuel heater installed on the left side of the engine on the LP compressor case. The fuel filter is a 10 micron nominal/25 micron absolute unit. It is located downstream of the heat transfer matrix. Particles between the 10 to 25 micron sizes may pass through the filter, but particles above 25 micron in size will not. The filter is protected by a bypass valve and a bypass indicator. The filter is not cleanable. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 24 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL FILTER TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 25 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION INTRODUCTION The engine fuel control system gives fuel at the required pressure and flow to control the engine power. The engine fuel control system has these components: • • • • • Full Authority Digital Electronic Control (FADEC) Fuel Metering Unit (FMU) Fuel Control Electrical-Wiring-Harness Characterization Plug Permanent Magnet Alternator (PMA) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 26 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION GENERAL DESCRIPTION The engine fuel control system manages the engine powerplant by: • • • • • • • Supplying fuel flow scheduled as a function of the selected PLA Engine ratings Measured torque Ambient conditions Detects and accommodates an Nl decouple by engine shutdown Supplies voltage to the Propeller Electronic Control (PEC) above 40% NH speed Detects and indicates faults The fuel flow is controlled by the FMU metering valve which is controlled by the Full Authority Digital Electronic Control (FADEC). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 27 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM The connectors are: SYSTEM OPERATION FULL AUTHORITY DIGITAL ELECTRONIC CONTROL (FADEC) PURPOSE The FADEC electronically controls the engine within safe thermal and mechanical operating limits. The FADEC sends an electrical signal to the Fuel Metering Unit (FMU) to control engine power. This signal controls the fuel flow to the engine as a function of the selected Power Lever Angle (PLA), engine ratings, measured torque and measured speeds. The FADEC also: • • • • • • • • Controls the P2.7 Handling Bleed Off Valve (HBOV) during handling to prevent compressor stall Controls the P2.2 Handling Bleed Off Valve to prevent compressor stall Prevents an engine overspeed Supervises engine starts and engine shutdowns by controlling the ignition exciter Detects and accommodates an Nl decouple by engine shutdown Supplies voltage to the Propeller Electronic Control (PEC) above 40% NH speed Detects and indicates faults. Communicates to other units through the Universal Asynchronous Receiver Transmitter (UART) and ARINC data bus interfaces. Also communicates with the Engine Display and the Engine Monitoring Unit (EMU) in maintenance mode • • • • • J1: Connects the engine components to the FADEC channel A J2: Connects the engine components to the FADEC channel B J3: Connects the characterization plug to the FADEC channel A J40: Connects the airframe components to the FADEC channel A J50: Connects the airframe components to the FADEC channel B The FADEC is a dual-channel microprocessor-based controller. Each channel has identical hardware and software. The hardware in each channel incorporates a central processor, an Input/Output (I/O) gate array, appropriate I/O interfaces and a fully independent overspeed system. Hardware discretes, utilized for channel control, and a cross talk serial bus are the only links between channels. The independent overspeed protection system uses redundant NH signals from the engine to command a fuel shut off in the event of an NH overspeed. The overspeed trip is set at 108% NH. The overspeed circuitry is tested each time the engine is shut down. The FADEC calculates the maximum rated power available for each rating from the inputs that follow: • • • • • Ambient temperature and air pressure data from the ADU Air temperature from the T1.8 sensor located in the engine inlet Ambient pressure data from a FADEC mounted sensor Selected bleed mode Selected rating From these inputs and in conjunction with the propeller speed, the FADEC displays the torque target on the Engine Display (ED). The FADEC then increases or decreases the fuel flow through the FMU to match the indicated torque to the target torque, if the PLA is in the Rated Power detent. The FADEC is installed on the left side of the inlet case and mounted on vibrationresistant bushings. Five connectors on the back of the FADEC give connection points for the engine and airframe components that interface with the FADEC. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 28 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - POWER REQUEST BLOCK DIAGRAM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 29 of 90 BOMBARDIER DHC 8-400 (PWC PW150) • ENGINE FUEL CONTROL SYSTEM NPT feedback signal SYSTEM OPERATION This loop is used to control engine power as a function of propeller speed during low power operation on the ground. POWER MANAGEMENT The control software gives closed loop control of the engine in response to inputs from the pilot and other aircraft systems. Steady State Limit Loops ensure that the thermal and mechanical limits of the engine are not exceeded, as a result of the requested setting from the outer governing loops. These limits apply to the speed of the engine spools, NH, NL and NPT and engine torque. Control of engine power is achieved by deriving a fuel flow request from the main, or outer governing loops after applying various transient and steady state engine limits. In addition, the control system is prevented from requesting fuel flows that exceed the hydro-mechanical limits of the Fuel Metering Unit (FMU). The Power Request Logic uses these primary pilot inputs: Transient Limit Loops limit the change in requested gas generator speed, derived from the governing loops. This protects the engine from: • • • • PLA CLA ECS bleed selection Engine derate • • • A fuel flow rate limit is also used to limit fuel flow commands to within the capabilities of the FMU. The Power Request Logic uses these ambient conditions: • • • Surge Flameout Overtorque Altitude Airspeed Temperature POWER REQUEST LOGIC The Power Request Logic also uses an UPTRIM signal from the remote PEC, under failure conditions, to calculate the requested engine power. During Power Governing, the power request and the power feedback is used to command the fuel flow required to achieve and maintain the requested engine power. Power governing is the primary mode of control during flight takeoff, climb and cruise and in reverse. The power setting logic determines the requested power as a function of engine rating, pilots inputs, remote engine failure and ambient conditions. These inputs effect requested power are described in the following table: During Power Turbine Speed Under-speed Governing, the fuel flow request is computed from the: • Power turbine speed (NPT) under-speed schedule TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 30 of 90 BOMBARDIER DHC 8-400 (PWC PW150) INPUT TYPE INPUT EFFECT ON POWER REQUEST Pilot Activated PLA Schedules % of rated power as a function of PLA Pilot Activated CLA Selects engine power rating and propeller governing speed for normal operation Pilot Activated Rating Discretes Pilot Activated ECS Bleed Selection Pilot Activated Power Derate Selection ATPCS Uptrim Command Ambient Conditions Ambient Temperature Ambient Conditions Ambient Pressure Thermal rated power of the engine will change with ambient temperature, ambient pressure (altitude) and airspeed Ambient Conditions Delta Pressure (Airspeed) Thermal rated power of the engine will change with ambient temperature, ambient pressure (altitude) and airspeed Allows the selection of power ratings that differ from the standard mode of operation Biases the rated power downward to compensate for the effect of requested bleed on the engine thermal rating. Also used to discriminate between Maximum Continuous and Maximum Takeoff ratings Biases the takeoff rated power downward in the decrements of 2% to a limit of 10% Automatically changes power rating from Normal to Maximum Takeoff upon receipt of the Uptrim discrete from the remote PEC Used to determine the thermal rated power of the engine. ENGINE FUEL - POWER REQUEST LOGIC TABLE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 31 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED POWER SETTING WITH THE POWER LEVER The power lever modulates power requests from Full Reverse (0°) to Rated Power Detent (77.5° to 82.5°). Ground handling is achieved at any PLA below Flight Idle (35°). Above 35°, the power request increases linearly with increasing PLA until the Rated Power Detent. Moving the power lever in the over travel region (82.5° to 100°) increases requested power up to 125% of maximum takeoff rating. It also results in an increase of engine software limits. In this region the propeller control system automatically sets propeller speed to 1020 rpm. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 32 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - POWER LEVER ANGLES TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 33 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED RATING SELECTION WITH THE CONDITION LEVER Rating selection occurs concurrently with propeller speed selection when the condition lever is moved to the detent positions. The propeller control converts the Condition Lever Angle (CLA) to a position and transmits this as discrete information to the FADEC through the PEC/FADEC serial data buses. For all condition lever positions, the Rated Power is achieved when PLA is in the rating detent 77.5° to 82.5°. When the PLA is reduced below the detent position, the power request for all positions converge to a single point at 55°. In the PLA overtravel region, the power request for all ratings converge to 125% maximum power at 95°. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 34 of 90 BOMBARDIER DHC 8-400 (PWC PW150) INTENTIONALLY LEFT BLANK TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 35 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED SELECTION OF ALTERNATE POWER RATING AND PROPELLER SPEED COMBINATIONS (RATING DISCRETES) Alternate combinations of propeller speed and engine power rating can be set by using the MTOP, MCL and MCR Rating Discretes in the flight compartment. These discretes, transmitted to the FADEC by the Engine Cockpit Interface Unit (ECIU), override the rating normally selected as a function of CLA under certain conditions. When the optional MTOP discrete is activated, the Maximum Take-Off Power (MTOP) is selected by FADEC whenever the condition lever is in the 1020 rpm position. The MTOP rating is defined as the maximum available power certified for take-off operation. The MTOP switch is an alternate action switch. When CLA is in the 900 rpm position and the MCR discrete is selected, the Maximum Climb (MCL) rating normally associated with this propeller speed is overridden by the Maximum Cruise (MCR) rating. The MCL rating discrete is a momentary action switch, so any movement of the CLA will base engine rating selection on the new CLA position. Alternatively, the MCL rating can be recovered, at the same CLA position, by selecting the MCL discrete. The MCL discrete is also a momentary action switch. Selection of MCL at a CLA of 850 rpm is also possible using the MCL rating discrete. The MCL discrete is also a momentary switch. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 36 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - ALTERNATE POWER RATING SELECTIONS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 37 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED ENVIRONMENTAL CONTROL SYSTEM (ECS) BLEED SELECTION The power requested at a given power rating is a function of the selected ECS bleed when the engine is operating at the thermal limit. The ECS bleed selection is translated in bleed levels, used for thermal power rating calculations. Higher amounts of ECS bleed results in less thermal rated power. This may reduce the power requested for a given power rating, depending on the ambient conditions. The FADEC discriminates between single and dual ECS bleed by using the following logic. Dual engine level is used unless the power rating is MTOP, demanded by Uptrim only, or ECS is selected OFF on the remote engine. The ECS bleed selection is also used by FADEC to distinguish between MTOP and Maximum Continuous Power (MCP). BLEED MTOP/MCP OFF MTOP MIN MTOP NORMAL MCP MAX MCP TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 38 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED POWER DERATE SELECTION Before take-off the power can be reduced for take-off in the NTOP rating using the power derate function. To derate the requested power, the Power Derate discrete is pressed, with the CLA at the 1020 rpm position and PLA below the rated power detent. Selection of the Power Derate discrete momentary switch decreases the NTO requested in steps of 2% to a limit of 10%. Selection of the Power Derate Reset discrete, at any time, resets the derate to 0%. A Power Derate is permitted only when it is confirmed, through cross powerplant communication, that both FADEC channels of each powerplant have received a Power Derate command. The Power Derate function cannot be activated in MTOP or MCP rating. If an Uptrim is commanded from the remote powerplant, the requested derate will apply to the MTOP requested power. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 39 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED AUTOMATIC TAKE-OFF POWER CONTROL SYSTEM The Automatic Take-off Power Control System (ATPCS) increases the power of an engine if the other engine loses power. This is referred to as Uptrim, or, Automatic Take-Off Thrust Control System (ATTCS). The local engine FADEC will respond to the Uptrim signal from the remote Propeller Electronic Control/Autofeather (PEC/AF) unit by changing from NTOP to MTOP/MCP. The ATPCS is active during take-off and go around manoeuvres. The local ATPCS is armed when: • • Both local and remote PLA are high Local engine torque is high If the local engine fails (indicated by low torque), an Uptrim signal is sent by the local PEC to the remote FADEC. An Uptrim condition is shown in the flight compartment by: • • • Uptrim indication Change in engine rating from NTOP to MTOP/MCP Change in the torque bug from NTOP to MTOP/MCP TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 40 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED MECHANICAL AND THERMAL POWER LIMITS The engine power limit logic is the lowest value between the mechanical power limit and the thermal power limit for the selected rating. The mechanical power limit is set as a function of the engine rating. The thermal power rating is set as a function of: • • • • • • Rating selected Ambient temperature Aircraft altitude Aircraft speed ECS bleed air extraction Power turbine shaft speed RATING SELECTED MECHANICAL POWER SHP MTOP/MCP 5071 NTOP 4580 MCL 4058 MCR 3947 TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 41 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM (NHHP), to obtain the requested power and deliver the requested NH. The authority of the power loop is restricted by mechanical and operational limits in the NH. SYSTEM OPERATION These limits are built into the gas generator limiting loop. POWER MANAGEMENT CONTINUED ENGINE CONTROL LOGIC The control logic is structured as these three loops: • • • Outer control loop Intermediate control loop Inner control loop OUTER CONTROL LOOP There are two parallel outer control loops: • • Power governing loop Power turbine under-speed (NPT U/S) loop POWER GOVERNING LOOP (OUTER LOOP) The power governing loop is active in forward and reverse power control. The power governing loop will govern the engine to a requested power. The philosophy of the PW150A is to close loop on power. The principal control loop is the power governing loop. The actual engine power is measured using the Torque/NPT sensors and compared to the requested power. The FADEC attempts to eliminate the difference between requested power and actual power. The power control loop will determine the gas generator speed required TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 42 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - ENGINE CONTROL LOOPS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 43 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM speed of the engine. This value is 64% or 20,000 rpm. SYSTEM OPERATION The Flight Idle (FI) speed is a variable NH to maintain zero thrust in flight. The Flight Idle speed is varied as a function of ambient pressure and ambient temperature. POWER MANAGEMENT CONTINUED The schedule between GI and FI is a straight line extrapolation between the points. NPT UNDERSPEED GOVERNING LOOP (OUTER LOOP) The fan out points, found at approximately 10° and 40° PLA, are set above the GI and FI speeds respectively to allow for smooth transition on to the Power Governing Loop. The NPT U/S function is primarily for ground taxiing manoeuvres. It maintains a propeller speed of 660 Np to make sure AC generator power is available. The control system closes loop on propeller speed and determines the NH to set the required NPT. Thrust is then controlled through the minimum blade angle schedule in the PEC. This gives a direct relationship between PLA and propeller blade angle. This loop is normally active during ground handling and taxiing. High power, high torque or high airspeed will cancel the NPT U/S governing loop. The loop will also be cancelled if the PEC determines that the propeller control system is unable to control through the PEC/FADEC RS422 digital communication bus. NH max loop above 40° PLA rises quickly, to avoid any restriction of the power loop until it intercepts the maximum NH limit allowed. The lower limit rises by always maintaining a positive power gradient with respect to PLA and without interfering with the Power Governing Loop authority. In reverse similar criteria are used to determine the upper and lower bounds of the Gas generator Limit Loop. GAS GENERATOR LIMITING (OUTER LOOP) The NH limiting logic in FADEC prevents NH exceeding a given threshold, which is determined as a function of PLA and ambient conditions. The limits, NH max and NH min, are derived from operational and mechanical restrictions. The upper bound, NH max Limit, is determined by operational restriction required on the power loop. The NH max Limit, NH max and NH min bound the power loop at PLA greater than 40° and PLA below 10°. The authority of the Power Governing Loop is large in the forward and reverse power regimes. The lower limit of the Gas Generator Limiting Loop is determined as follows: The Ground Idle (GI) point, PLA = 20° is determined as the minimum self-sustaining TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 44 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - POWER GOVERNING LOOP AUTHORITY TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 45 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM NH SPEED GOVERNING LOOP INTERMEDIATE LOOP SYSTEM OPERATION POWER MANAGEMENT CONTINUED The Outer Control Loop and Outer Control limiting Loops derive a selected NH request speed. The FADEC attempts to eliminate the difference between the requested NH speed and the actual NH. The Gas Generator Loop determines the requested gas generator speed fuel flow (WF NH). NPT O/S LIMITING (OUTER LOOP) ACCELERATION AND DECELERATION INTERMEDIATE LOOP The NPT Overspeed Control Limit in the FADEC prevents the power turbine speed from exceeding a given threshold (NH NP TO/S). This is set as a function of PLA and ambient conditions. The engine is limited in rate of acceleration and deceleration by the acceleration and deceleration limits, WF ACC and WF DEC. These limits calculate a fuel flow request, to limit the engine on the programmed acceleration or deceleration schedule. The NH Accel or Decel Limiting Schedule provides compensation as a function of NH and ambient conditions. This ensures that the system meets the required transient accel and decel, including slam manoeuvres, without causing engine surge or flameout. This logic calculates a gas generator speed request value, based on the power turbine overspeed reference and the power turbine speed feedback. The propeller control system includes independent mechanical overspeed protection, to coarsen propeller blade angle when NP exceeds 104%. This NP O/S governor is locked out in reverse. The FADEC NPT O/S Governing loop becomes the primary means of protection. The propeller overspeed governor set point, when not locked out, is below the FADEC NPT O/S schedule. TORQUE LIMITING OUTER LOOP The Torque Limiting Logic in FADEC prevents engine torque from exceeding a given threshold. This is a function of PLA and ambient conditions. The logic calculates a gas generator speed request value based on the torque limit reference and the torque feedback. TRANSIENT OVERTORQUE LIMITING (OUTER LOOP) The Torque Limiting Logic in FADEC prevents any torque from exceeding a fixed steady state threshold. In the event of a spurious feathering of the propeller at high power, the transient overtorque can exceed this threshold. FADEC uses anticipation in this control loop to rapidly reduce NH to prevent overtorque in excess of 150%. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 46 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - ENGINE CONTROL LOOPS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 47 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM The FADEC software sets these “soft” fuel flow limits: • • SYSTEM OPERATION POWER MANAGEMENT CONTINUED NL LIMITING INTERMEDIATE LOOP The NL Overspeed Control Logic in the FADEC prevents the low pressure turbine speed from exceeding a given threshold. This is a function of PLA. The logic calculates a fuel flow request value, WF NL, based on the NL limit reference and the NL feedback. Wf/P3 Acceleration Rate Limiting (Intermediate Loop) The Wf/P3 Accel Rate Limit scheduling, WF/P3 ACC, becomes active after an engine surge is detected and controls the fuel flow to the engine. FADEC recognizes a surge by an abrupt reversal these two parameters: • • To not request more fuel flow than the FMU can deliver, Wf MAX To not request a fuel flow less than the engine requires to maintain a flame, Wf MIN The fuel flow requested by the Intermediate Control Loop, after being rated and range limited, goes through a selection process. The selection process is between the start fuel flow, WF START and the run fuel flow (WF REQ), and is a function of engine mode selection. The fuel flow is then converted into a metering valve position. The fuel flow effector minor loop compares the FMU metering valve position request with the measured metering valve position. The valve position signal is from the FMU metering valve LVDT. The system closes loop and gives the metering valve position to control the fuel flow to the engine. The feedback metering valve position is then converted into a feedback fuel flow (WF FB). WF FB is compared with the requested Intermediate Control Loop fuel flow. Rate of change of P3, P3 dot Rate of change of NH dot, NH dot dot The Wf/P3 Accel limiting Loop is active for 1.5 seconds maximum and lags the Wf increase that results from a rapid P3 increase. This is due to the abrupt decreases and increases of P3 during surge. FUEL FLOW INNER LOOP The fuel flow requested by the Intermediate Control Loop is limited in rate of acceleration by the fuel flow rate limiter. The Wf dot accel limit avoids these fuel flow limits: • • Engine acceleration limits, Wf dot NH MAX/MIN FMU hardware rate limitations, Wf dot FMU MAX/MIN At all operating conditions, the fuel flow is limited by the WF dot limit, to a value below the FMU hardware limitation. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 48 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - ENGINE CONTROL LOOPS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 49 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM After passing through the servo filter, the pump flow divides, with engine flow passing through the metering valve and excess flow going to the Pressure Regulating and Motive Flow Control Valve (PRV/MFC). SYSTEM OPERATION The PRV/MFC senses the upstream metering valve pressure P1 and the downstream pressure (P2). It varies the amount of fuel bypass by holding the difference between P1 and P2 constant. POWER MANAGEMENT CONTINUED COMPONENT LOCATION AND DESCRIPTION This pressure difference is changed with fuel temperature by bimetallic discs acting on the PRV spring. This keeps the metering valve mass flow constant at a fixed valve position regardless of the fuel density change due to temperature. FUEL METERING UNIT (FMU) The FMU modulates the engine fuel flow over the entire operational envelope of the engine in response to signals sent by the FADEC. The FMU flow path has: • • • • An inlet filter Wash type fine filter Metering valve Minimum pressure and shutoff valve An adjustment screw in the valve cap changes the spring force to give a rate of adjustment on metering valve gain during FMU calibration. PRV damping is provided by a screened orifice. Fuel enters the inducer and regenerative boost stage of the integral two stage pump where it is immediately pressurized to provide flow to the Fuel Oil Heat Exchanger (FOHE). From the FOHE, fuel is returned to the FMU. Fuel temperature is sensed and a signal is sent to the flight compartment fuel temperature gauge. The fuel then enters the high pressure gear stage of the pump. High pressure fuel then passes through the coarse and fine filters. Flow passes along the outside of the filter and gives a fine filtered fuel supply (PF) for various components in the FMU. The required filter area is minimized by maintaining a flow velocity past the filter element. Washing action prevents accumulation of deposits on the fine screen. Cleaning is not required. The servo pressure regulator (PR) supplies the metering valve with a fine filtered pressure source that is maintained at constant 220 psid (1516.85 kPad) above interstage pressure. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 50 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL METERING UNIT SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 51 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM The pressure is modulated by the dual coil torque motor. SYSTEM OPERATION Engine fuel flow is scheduled by the FADEC through a command signal to the torque motor. POWER MANAGEMENT CONTINUED The current input to the torque motor modulates the flapper, allowing fuel to flow either into or out of the metering valve piston end, depending on direction of flapper motion. In this manner, metering valve velocity is controlled by a current input to the torque motor. COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL METERING UNIT (FMU) CONTINUED As the metering valve position changes, the fuel flow metering window area changes with a known relationship. The PRV/MFC splits pump excess flow into two paths: • • Metering valve position is detected by a dual coil LVDT attached to the valve spool. To the motive flow line and then to the tank ejector pumps To the pump interstage (pd) As the engine spools up during start, pump flow in excess of metered flow and leakage is first bypassed to the motive flow line. This occurs as soon as the FMU is placed in the ON condition by de-powering the overspeed/shutdown solenoid. This opens the flow path to the motive flow line through the Minimum Pressure and Shutoff Valve (MPSOV). At some point before reaching idle speed, pump excess flow or motive flow, reaches approximately 1050 pph. The LVDT electrical position is utilized by the FADEC to close the minor loop around the metering valve servo. When the metering valve is at the correct fuel flow position, the FADEC returns the torque motor to there null position, where the metering valve velocity is zero. The torque motor is designed with a null bias. In the event of loss of current from the FADEC, the torque motor returns to a zero current position, which drives the metering valve to the shutoff position. At this point the motive line is saturated due to the back pressure of the ejectors. After this point the PRV/MFC slews to open the bypass path to Pd. Any additional pump excess flow is now bypassed to Pd. From this point on the PRV/MFC regulates P1-P2 to 40 psid (275.79 kPad) in the same manner as a standard PRV, bypassing excess flow to Pd. The metering valve is a half area type servo valve. Regulated servo pressure (PR) acting on a half area servo piston is balanced by a modulated pressure acting on the valve area. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 52 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL METERING UNIT SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 53 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM pump flow to the pump interstage. SYSTEM OPERATION With the MPSOV closed, the PRV will regulate a fixed pressure of 40 psid (275.79 kPad) across the metering valve window and PRV damping orifice. POWER MANAGEMENT CONTINUED After commanding a normal shutdown, the FADEC at some point during engine spooldown will command the metering valve to its shutoff position. COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL METERING UNIT (FMU) CONTINUED From the metering valve, engine fuel flow then passes through the Minimum Pressure Shut Off Valve (MPSOV). The MPSOV provides a minimum control inlet pressure for proper operation of other control features. The MPSOV opens when metering valve downstream pressure P2 reaches a level sufficient to overcome the spring force in the valve. In addition, the MPSOV, upon shutdown provides for motive flow shutoff and a manifold drain feature to drain the fuel manifold on engine shutdown. When the MPSOV closes, the path from the PRV/MFC is cut-off, motive flow stops and the motive flow line is depressurized. At the same time, a seal on the valve spool passes over a series of holes in the valve sleeve, porting the manifold to the motive flow discharge port, allowing the manifold to drain. A dual coil solenoid is provided to shutoff metered flow to the engine when energized by the FADEC for either normal shutdown, or overspeed. This cuts off flow through the shutdown circuit and drops P1 pressure to 40 psid (275.79 kPad) above drain. A vapour vent check valve and orifice vents vapour when the aircraft boost pump is initiated prior to starting the engine. With the aircraft boost pump on, pump interstage pressure is increased to 35 psig (241.32 kPag). Because the motive flow line is depressurized, the vapour vent check valve will open and any vapour in the boost pressure lines will be returned to the tank through the motive flow line. As motive flow increases and pressurizes the motive line, the check valve is closed, closing off this leakage path. The orifice limits the rate of fuel leakage from boost to motive line while the leakage path is open. A second, completely independent single channel solenoid, allows the pilot to shutdown fuel flow to the engine. When either solenoid is opened, downstream metering valve pressure is ported to the spring side of the MPSOV through the PRV damping orifice. When this occurs, the higher pressure plus spring force closes the MPSOV and provide drop tight sealing to the engine. In addition , the spring side of the PRV senses a lower pressure and opens to bypass TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 54 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL METERING UNIT SCHEMATIC (SHOWN NORMAL/OVERSPEED SHUT DOWN) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 55 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL METERING UNIT (FMU) CONTINUED The FMU has two integral fuel pumps: • • A low pressure pump A high pressure pump Both pumps are engine-driven. Fuel from the low pressure pump is routed to the FOHE. From the FOHE, fuel is routed to the inlet of the high pressure pump. From there, it enters the metering portion of the FMU. The coarse screen mesh is 0.012 inch (0.3048 mm). The fine screen mesh is 0.0013 inch (0.03302 mm). The main fuel pump is a positive displacement gear type pump. It has these components: • • • Inducer stage to boost the fuel pressure from pump inlet to regenerative boost stage Regenerative boost stage to supply fuel flow at the appropriate pressure level to the high pressure (HP) gear stage HP gear stage (to provide high pressure fuel flow to the FMU) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 56 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL METERING UNIT SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 57 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM Pump drive spline lubrication is provided from the AGB. Pressurized oil is forced into the centre of the gearbox drive shaft at the base of the PMA. From there it passes along the inside of the shaft, through the gearbox end spline, through another hole in the shaft and into the PMA housing. Oil return channels in the PMA stator housing return the oil to the gearbox. The pump end spline does not have positive lubrication oil circulation, but uses deadheaded oil from the centre of the drive shaft. SYSTEM OPERATION POWER MANAGEMENT CONTINUED COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL METERING UNIT (FMU) CONTINUED Fuel entering the pump first passes through the inducer stage where the pressure is increased before entering the boost stage. A port is provided at the pump inlet for a low pressure switch. The signal from the switch goes to FADEC, from FADEC the signal goes to the ECIU and then to the Caution and Warning light. Fuel then passes to the regenerative boost stage. Here the pressure is increased to a level to prevent cavitation and compensate for losses in the FOHE and the fuel filter. Fuel returning from the FOHE and filter enters the HP gear stage. The HP gear stage supplies the necessary fuel flow and pressure for fuel control and engine operation. The pump gears are driven at accessory gearbox speed by a spline drive shaft. A carbon face seal prevents fuel from entering the pump/PMA interface cavity. Any fuel entering the cavity is drained overboard. A high pressure relief valve (in the FMU) protects the pump and control components from excessive pressure. The valve relieves at 1450 psi (9997.39 kPa) and spills excess flow and pressure back to the inlet side of the pump. After passing through the high pressure gear stage, fuel exits the pump and goes to the fuel control section. A quill shaft between the gearbox end spline and the pump end spline allows for misalignment. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 58 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL METERING UNIT (FMU) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 59 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL CONTROL ELECTRICAL WIRING HARNESS The fuel control electrical wiring harness connects the sensors, the FMU and the PEC to the FADEC. The harness has these connectors: • • • • • • • • • • • • • • • • • • P1, FADECA P2, FADECB P4, NH sensor A P5, NH sensor B P6, HP Handling Bleed Off Valve (HBOV) P7, FMUA P8, LP HBOV B P9, LP HBOV A P10, FMUB P11, Torque sensor A P12, Torque sensor B P13, MOT/T6 sensor P14, T1.8 sensor P15, P3 sensor P16, NL sensor P17, PMA A P18, PMA B P19, Propeller Electronic Control Unit TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 60 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL CONTROL ELECTRICAL HARNESS DETAIL 1 TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 61 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL CONTROL ELECTRICAL HARNESS DETAIL 2 TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 62 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - FUEL CONTROL ELECTRICAL HARNESS DETAIL 3 TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 63 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED COMPONENT LOCATION AND DESCRIPTION CONTINUED T1.8 TEMPERATURE SENSOR A dual platinum resistance temperature sensor measures the intake air temperature. The sensor is located in the intake just upstream of the first stage low pressure compressor. The sensed temperature is used to calculate engine ratings. Calculated engine ratings are used to: • • Automatically set maximum rated power Show maximum rated torque in the flight deck Intake temperature measured by the T1.8 sensor is used by the local FADEC and transmitted to the opposite FADEC. The two values are averaged in each FADEC to make sure that Rated Torque shown on the Engine Display (ED) is the same for both engines. T1.8 is the primary source of intake temperature to the FADEC. The maximum allowable difference between local and opposite T1.8 is ± 2 °C. The secondary source of intake air temperature comes from the Air Data Unit (ADU). The FADEC also monitors the ADU Static Air Temperature (SAT) on both channels. The SAT from the ADU can also be used as the primary source (depending on the rating selected). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 64 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL - T1.8 TEMPERATURE SENSOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 65 of 90 BOMBARDIER DHC 8-400 (PWC PW150) ENGINE FUEL CONTROL SYSTEM SYSTEM OPERATION POWER MANAGEMENT CONTINUED COMPONENT LOCATION AND DESCRIPTION CONTINUED CHARACTERIZATION PLUG The characterization plug gives trim values for torque calculations to the FADEC and to the PEC. It also identifies the engine model to the FADEC. The characterization plug is installed on the FADEC at the J3 connector. The plug is connected physically to FADEC channel A only. The trim values are passed to channel B by the FADEC internal communication bus. The plug is attached to the turbomachinery with a lanyard. This is to make sure that the plug remains with the turbomachinery if the FADEC is removed from the engine. The characterization plug can only be replaced with a plug of the same class. The trim values of the plug are marked on the reduction gearbox data plate. Inside the plug there are connections for four resistors. Two are used for the torque shaft gain slope and bias offset trim values and a third one is used for the engine model identification. The fourth resistor location is unused. The value of each resistor is determined during the engine test and can only be done by a qualified overhaul facility. A sealing compound is put on the resistors after their installation in the plug. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 73 - ENGINE FUEL & CONTROL Issue 6 - January 2023 Page 66 of 90 BOMBARD