Bombardier DHC 8-400 (PWC PW150) APU - Maintenance Training Manual PDF

BOMBARDIER DHC 8-400 (PWC PW150) ATA 49 - AUXILIARY POWER UNIT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY B1/B2 MAINTENANCE TRAINING MANUAL Issue 6 - January 2023 Page 1 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT INTRODUCTION The Auxiliary Power Unit (APU) provides 28V D...

BOMBARDIER DHC 8-400 (PWC PW150) ATA 49 - AUXILIARY POWER UNIT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY B1/B2 MAINTENANCE TRAINING MANUAL Issue 6 - January 2023 Page 1 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT INTRODUCTION The Auxiliary Power Unit (APU) provides 28V DC electrical power and bleed air to the aircraft systems. This permits these systems to operate without the use of ground power sources or the aircraft engines. The Hamilton Sundstrand APS 1000 Model (T62T-46C12) APU is a turbine-powered system used to give auxiliary DC electrical power for the aircraft electrical system and bleed air for the Environmental Control System (ECS). The APU is a non-essential system and cannot be operated when the aircraft is in flight. GENERAL DESCRIPTION The APU engine and its associated components are installed in the tail cone. The gas turbine engine drives the gearbox module. The gearbox module reduces the turbine RPM and drives a starter/generator, APU fuel pump and an internal oil pump. The APU gives bleed air to the ECS and the 28V DC to the right main feeder bus. The APU has a control/monitoring system, an air induction/compression system, an exhaust system, a reduction gearbox and a combination starter/generator. The APU incorporates: • • • • • • • • • • • An air induction/compression system An exhaust system A reduction gearbox A lubrication system An ignition system A combination starter/generator Full Authority Digital Electronic Controller (FADEC) A control/monitoring system A control panel Interconnect harness Centralized Diagnostic System (CDS) interface TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 2 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 3 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT OIL SYSTEM PARAMETERS: GENERAL DESCRIPTION CONTINUED LEADING PARTICULARS WEIGHT 140 lbs (dry) OPERATING ALTITUDE -1000 TO 15,000 ft (Ground Mode Only) OIL PRESSURE 35 PSIG (minimum) 60 PSIG (maximum) OIL TEMPERATURE 275 F (135 C) (maximum) OIL TYPE MIL-L-7808 -54°C to +54°C (-65°F to +130°F) MIL-L-23699 -40°C to +54°C (-40°F to +130°F) CAUTION: SEA LEVEL 59 F (15 C) STANDARD DAY: FUEL CONSUMPTION 202 lb/hr (20 SHAFT HORSEPOWER 84 lb/min BLEED FLOW) OUTPUT SHAFT HORSE POWER 60 HP ROTOR SPEED 100% (64,154 RPM) ROTOR OVERSPEED 105% (67,362 RPM) ROTOR UNDERSPEED 95% (54,531 RPM) BLEED AIRFLOW 113 LBS BLEED AIR PRESSURE 48 PSIG DO NOT MIX OR SUBSTITUTE OIL TYPES. USE ONLY ONE OF THE APPROVED OILS. IF APU OIL SUMP LEVEL IS LOW AND THE SAME TYPE OF OIL IS UNAVAILABLE OR UNKNOWN, DRAIN THE OIL SUMP AND CHANGE THE OIL FILTER. FILL THE SYSTEM WITH AN APPROVED OIL. EXHAUST GAS TEMPERATURE (EGT): Start Acceleration 1890°F (1032°C) Steady State 1324°F (717°C) GEARBOX SPEEDS: Input 64,154 RPM Starter/Generator 11,860 RPM (output) Fuel Pump 4,186 RPM (output) Oil Pump 4,379 RPM (output) TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 4 of 98 BOMBARDIER DHC 8-400 (PWC PW150) INTENTIONALLY LEFT BLANK TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 5 of 98 BOMBARDIER DHC 8-400 (PWC PW150) • • AUXILIARY POWER UNIT Starter/Generator Fuel control pump SYSTEM DESCRIPTION The APU control has a FADEC and various valves, sensors, relays and switches. The FADEC controls, monitors and diagnoses all phases of the APU system operation through these components. The FADEC also communicates fault information to the aircraft CDS through an ARINC link. The CDS displays the fault information on the ARCDU units for maintenance troubleshooting, when APU PWR selected ON. The FADEC controls the APU start, fuel flow, ignition, acceleration to 100% speed, and shutdown. The FADEC monitors engine speed, EGT, oil temperature, oil pressure, and ambient pressure. During operation, the APU rotor speed is kept at a constant RPM. Abnormal conditions during operation are recorded as faults in the FADEC Non Volatile Memory. The FADEC provides the necessary sequencing, condition monitoring, fault detection, fault isolation and protection of the APU System. The FADEC also performs the interface functions between the aircraft and the APU. The air induction system consists of an air inlet system located in the aircraft tail cone. The air induction system provides outside air to the APU compressor. Some of the compressed air is bled off the APU and delivered to the aircraft Environmental Control System. A bleed control valve controls the flow of air. The remaining compressed air is heated in a combustor using fuel provided by the APU fuel system, the combustion products then drive the turbine wheel. The energy released drives the compressor and the gearbox. The gearbox drives the starter/generator and the fuel pump. The exhaust gases exit the APU through the exhaust system. The gearbox assembly is a one piece aluminium casting with mounting pads for the engine and gearbox drive accessories. The gearbox also drives the following accessories: • Oil pump TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 6 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU/COMPONENT LOCATOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 7 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT SYSTEM DESCRIPTION CONTINUED POWER-PLANT The Auxiliary Power Unit (APU) gives electrical power to the aircraft right main bus, and bleed air to the Environmental Control System (ECS), when the aircraft is on the ground. The APU power-plant is installed in the tail-cone which has interfaces for the APU fuel line, electrical connections, air inlet assembly, exhaust, starter/generator duct system, fire detection and the fire extinguishing system. The Auxiliary Power Unit (APU) is located in a fireproof titanium compartment which forms the tail cone of the aircraft. The front of the panel is closed by a titanium firewall. Access to the APU is through two hinged doors that are part of the tail cone structure. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 8 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU ACCESS AND LOWER INTAKES TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 9 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT SYSTEM DESCRIPTION CONTINUED POWER-PLANT CONTINUED The APU is mounted to the empennage structure and to the tail cone by a three point mounting system. The two forward mounts are attached to the gearbox and the rear mount is attached at the top of the APU. A fish pole hoist is used to install and remove the APU. The hoist is attached to a lug in the APU compartment and uses quick connects to the APU front and rear lifting brackets. The APU is divided into three modules • • • Turbine Module Combustor Module Gearbox Module TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 10 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU LOCATION IN TAILCONE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 11 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT COMPONENT LOCATION AND DESCRIPTION APU ELECTRICAL HARNESS The engine control harness assembly consists of 15 electrical connectors and associated connecting wires. When installed on the APU engine assembly, the engine control harness assembly gives the electrical interface between the electrical components and the connection at the tail-cone firewall bulkhead. INTERCONNECT ELECTRICAL HARNESS The electrical interconnect harness carries the electrical interface from the connection point on the tail-cone firewall bulkhead, to the APU Full Authority Digital Electronic Control (FADEC) which is installed in the rear equipment bay. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 12 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU ELECTRICAL HARNESSES AND INTERCONNECT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 13 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT The upper end of the aft mount is attached to the lower side of the centre upper beam in the tail-cone structure. COMPONENT LOCATION AND DESCRIPTION CONTINUED MOUNTS Mounts are used to support the APU and give vibration isolation to the aircraft structure. The Auxiliary Power Unit mounting system is designed to be failsafe. Max limit flight loads will be supported with any single component failure. In the event of fire, the elastomer may be melted but the mount will snub and the APU location will be maintained within a safe envelope. The mounting system includes the components that follow: • • • • NOTE: A lifting eye is located aft of the upper mount. It is the hoist attachment point used APU installation and removal. Six side mount struts Two gearbox mounts One aft mount One aft strut SIDE MOUNTS The two APU side mounts provide two of the three vibration isolated, failsafe supports for the APU in the tail-cone structure. Each mount has three strut assemblies in a tripod arrangement, a strut bracket, two part vibration isolator, gearbox isolator mount and isolator snubbing washer. Each strut terminates in a standoff fitting attached to the spar of the vertical stabilizer. The firewall incorporates a cup around each fitting, sandwiched between the fitting and the spar. AFT MOUNTS The aft APU mount is the third, of the three, vibration isolated, failsafe supports for the APU. The lower end of the aft mount is attached to the APU at the uppermost point of the turbine combustor flange. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 14 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU FRONT AND TOP MOUNTS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 15 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT COMPONENT LOCATION AND DESCRIPTION CONTINUED INLET DUCT The duct (silencer) interfaces with the aircraft air inlet system to supply ambient air to the APU compressor. The duct is a fireproof, acoustically treated, bonded assembly. The duct has a glassfibre/phenolic resin outer shell of approximately rectangular section, lined with Nomex/phenolic resin honeycomb. This lining has Felt metal acoustic material bonded to the inner surface for improved sound suppression. An inlet screen doubler assembly is sandwiched between the inlet duct flange and the tail-cone inner surface. At the bottom end of the duct where it attaches to the APU is a fireproof silicone rubber seal. It is used to prevent tail-cone compartment air from entering the APU inlet system, while allowing for minor misalignment and relative motion between the APU and the structure. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 16 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU INLET DUCT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 17 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT COMPONENT LOCATION AND DESCRIPTION CONTINUED APU EXHAUST AND TAIL-CONE VENTILATION The exhaust system has an exhaust nozzle and a silenced exhaust duct. These components are not connected and are arranged to form an ejector system for tailcone ventilation. Exhaust gas is discharged from the duct through an upwards pointing outlet at the aft end of the duct. NOTE: The exhaust nozzle is removed as part of the APU. The exhaust duct is easily removed after first removing the APU. Tail-cone ventilation is achieved by using the APU exhaust flow to drive the ejector system. This system cools the APU and tail-cone section. Ambient air enters the tail-cone through a 4” diameter cut-out near the bottom centreline of the tail-cone between the firewall and the access door. This cut-out is protected by a stainless steel 0.25” mesh screen which is located between a riveted titanium doubler and the tail-cone skin. From the cut-out the air is ducted by a tube to the area immediately in front of the oil sump to assist in oil cooling. The air then flows around the APU before being educted into the exhaust ejector gas flow. Soak-back cooling after shutdown is accommodated by convective flow primarily through the normal ventilation system, as the exhaust duct outlet is the highest point of the system. This is supplemented by flow around the outside of the exhaust duct, which has a diametral clearance with the tail-cone structure. NOTE: Operating the APU with the access doors open may result in an oil over heat automatic shutdown. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 18 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU EXHAUST AND TAILCONE VENTILATION TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 19 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT COMPONENT LOCATION AND DESCRIPTION CONTINUED APU DRAINS Drain connections are supplied for: • • • • Fuel pump drive Gearbox breather Inlet plenum Combustor housing These connections have stainless steel tubes to connect them to the drain mast. The drain mast is titanium, airfoil shaped and protrudes through the left door of the tailcone. The mast has a separator plate to segregate the inlet plenum (front) drain from the other drains to prevent ingress of flammable fluids into the inlet. The combustor housing drain valve is threaded into the combustor drain boss. The valve is closed during engine operation by air pressure in the combustor housing. The valve is spring-loaded open when the engine is shut down, to let any accumulation of fuel in the combustor drain into the combustor drain system. All intercostals and frames in the tail-cone and doors, have drain cut-outs or holes at the lowest point to prevent the accumulation of liquids in the tail cone. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 20 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU DRAINS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 21 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE GENERAL DESCRIPTION The engine assembly of the Auxiliary Power Unit (APU) supplies shaft power to the gearbox module which has mounting pads for the starter/generator, and fuel control unit. Bleed air from the compressor section is supplied to the Environmental Control System (ECS) through a port on the right side of the engine. The Engine Assembly is a single-spool, gas turbine engine with a single-stage centrifugal compressor, an annular combustor and a single-stage radial inflow turbine. A Full Authority Digital Electronic Controller (FADEC) controls operation of the Engine Assembly. The engine assembly has the following three modules: • • • Turbine Module Combustor Module Gearbox Module TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 22 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - ENGINE MODULES TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 23 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT prevents compressor discharge air from bypassing the combustor. ENGINE TURBINE NOZZLE/CONTAINMENT ASSEMBLY COMPONENT LOCATION AND DESCRIPTION The Nozzle/Containment assembly has a containment ring and a turbine nozzle. The turbine nozzle is attached to the containment ring by seven radial pins. TURBINE MODULE Four bolts that pass through the diffuser and the air intake housing secure the complete assembly by fasteners on the forward side of the air intake housing. The turbine module has the following components: • • • Inside the turbine nozzle are 21 vanes, which direct the high velocity gas stream to the turbine wheel. Hot gas flows through the wheel and discharges axially through the turbine exhaust. Rotational energy derived from the hot gas flow stream by the turbine wheel drives the compressor and the shaft loads imposed by the generator and APU. Air Inlet Housing Balanced Rotor Assembly Turbine Nozzle/Containment Assembly AIR INLET HOUSING The Auxiliary Power Unit (APU) Air Inlet Housing assembly interfaces with the air inlet system to supply ambient air to the APU compressor. The air inlet housing supplies air to the compressor and provides a rigid support between the gearbox and combustor assemblies. The cast Inconel housing serves as the air inlet and supports the rotating assembly, diffuser and turbine nozzle containment assembly. The housing also provides containment for the compressor wheel of the rotor assembly in the event an over-speed above 110% causes the rotor assembly to burst. BALANCED ROTOR ASSEMBLY The single stage rotor is a balanced assembly that has an overhung radial compressor wheel and turbine wheel positioned on a two-bearing shaft system. The bearings are located in the air intake housing. A stationary segmented seal plate between the compressor and turbine wheel TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 24 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - COMBUSTOR AND TURBINE ASSEMBLIES TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 25 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE COMPONENT LOCATION AND DESCRIPTION CONTINUED COMBUSTOR MODULE The combustor module includes the following components: • • Combustor Housing Combustor Liner The combustor housing is attached to the air inlet housing with bolts. The Combustor Module consists of the combustor housing, combustor liner, start and main fuel nozzles, fuel manifolds, and associated hardware. A 2.5 inch bleed port is provided on the right side of the combustor housing for the extraction of bleed air for the Environmental Control System (ECS). Compressed air from the impeller is discharged into the combustor housing which forms a plenum surrounding the combustion chamber liner. When required, bleed air is ducted off this plenum and the remainder of the air enters the combustion chamber liner through dilution holes. Combustion takes place within the annular type combustor chamber liner, in the vicinity of the fuel injectors. Dilution air is added to produce a uniform flame and subsequent hot gas stream. Two start nozzles, six air atomizing fuel injectors, two ignitors and one radial pin go through the combustor chamber and help to locate it in the housing. A single combustor drain valve is threaded into the combustor drain boss. The drain valve is closed during engine operation by air pressure in the combustor housing. The valve is spring loaded open when the engine is shutdown. This ensures any accumulation of fuel in the combustor is drained overboard through the combustor drain system. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 26 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - COMBUSTOR MODULE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 27 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE COMPONENT LOCATION AND DESCRIPTION CONTINUED GEARBOX MODULE The gearbox housing is a machined aluminium casting. The casting provides, at the bottom, a fireproof oil sump. All gear shafts are supported in the housing by roller and ball bearings. The aft section of the gearbox provides a flange for the attachment to the engine turbine module. The gearbox has a main output pad for the starter/ generator and a second pad for the fuel control/pump assembly. Bosses on the housing allow for the mounting of high oil temperature and low oil pressure switches. GEAR REDUCTION SPEEDS The gearbox module provides for the reduction of the turbine rotor speed to those speeds that are required for starter/generator, fuel pumps, and oil pump drives. The input quill drives a set of fixed star gears, which transfer power to a ring gear. The oil pump gear is driven from the output shaft. The fuel pump gear is driven through a single idler gear. The fuel pump gear includes an air/oil separator for gearbox venting. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 28 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - GEARBOX MODULE GEAR ROTATIONS TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 29 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL INTRODUCTION The Engine Fuel and Control System delivers the fuel required to start and maintain a constant 100% RPM under varying load conditions and field elevations. • • • • • • • • • • Start Fuel Valve Main Fuel Valve Flow Divider Purge Check Valve Start Fuel Nozzle Main Fuel Nozzle Start Fuel Manifold Main Fuel Manifold Fuel Filter Assembly Fuel Filter Element The Engine Fuel and Control system monitors and supplies fuel to the APU. The system automatically compensates for field elevation and APU load conditions. Operation of the APU is controlled by the FADEC engine control system. GENERAL DESCRIPTION Fuel delivery to the APU fuel control and pump assembly is by gravity from the left wing fuel tank. The APU fuel valve is opened and closed by the FADEC during normal start and stop operations. The APU fuel valve is also closed during the following conditions: • • • • Auto shutdown relay APU caution relay Weight off wheels (WOFFW) signal from the PSEU Fire Control amplifier APU fuel valve status is shown on the Fire Protection Panel (FPP) in the flight compartment. The Full Authority Digital Electronic Control (FADEC) supplies the signals that operate the fuel control of the APU. The system has the components that follow: • • FADEC Fuel Control Assembly TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 30 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU FUEL VALVE CONTROL ELECTRICAL SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 31 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL GENERAL DESCRIPTION CONTINUED SYSTEM DESCRIPTION The gearbox driven fuel control receives fuel from the aircraft fuel system. Fuel flows through the low pressure centrifugal fuel pump to the fuel/oil cooler, fuel filter, high pressure fuel pump, the fuel servo valve and to the fuel solenoid manifold assembly. Excess fuel is circulated through the relief valve across the high pressure fuel pump. A differential pressure valve is in parallel with the fuel servo valve to maintain a constant differential pressure across the fuel servo valve. This results in a fuel flow linear relationship to the servo current command from the FADEC. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 32 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU FUEL SYSTEM SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 33 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL SYSTEM DESCRIPTION CONTINUED The Auxiliary Power Unit (APU) receives fuel from the aircraft left wing tank. Fuel flows to the APU when the APU fuel shutoff valve is open. Pushing the APU Control Panel PWR switch ON causes the FADEC to send 28V DC to open the valve. At start initiation, the Full Authority Digital Electronic Control (FADEC) records the Exhaust Gas Temperature (EGT). This EGT value is used for reference during the start sequence where specific rises in EGT need to occur before the start sequence can continue. The FADEC also records the ambient air pressure for field elevation compensation of the fuel supply. During the start sequence the FADEC uses signals from the speed sensor to initiate the transition to each successive stage of the start sequence and then to monitor Auxiliary Power Unit (APU) operation for over-speed/ under-speed conditions. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 34 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU FUEL FEED SYSTEM TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 35 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL SYSTEM DESCRIPTION CONTINUED FADEC The Full Authority Digital Electronic Controller (FADEC) is a microprocessor based controller. The FADEC has the necessary functions for control sequencing, condition monitoring, fault detection, fault isolation and protection of the APU system. The FADEC also transmits fault and maintenance data to the aircraft Centralized Diagnostic System (CDS) through an ARINC 429 data link. This data is used to provide APU maintenance information. During operation FADEC also monitors the: • • • • Exhaust gas temperature Oil pressure Oil temperature Turbine speed The conditions that follow will cause an APU shutdown: • • • • • • • • • • • • • Power switch OFF Oil pressure <35 psig (241 kPag) Oil temperature >275°F/135°C EGT >1890°F/1032°C on start EGT >1324°F/718°C during run Turbine speed <95% Turbine speed >105% Starter/Generator Overheat Weight off wheels signal (from the PSEU) Fire (test) Fire (detected) Loss of both EGT sensors Loss of both speed sensors TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 36 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU CONTROL SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 37 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT EVENT 14-17 FADEC initiates updates to EGT, AMB, Oil Data On On Off START SEQUENCE 50 Starter switched off Off On Off The Full Authority Digital Electronic Control (FADEC) controls the fuel flow to provide starting and operation of the Auxiliary Power Unit (APU). 60 GCU ready to generate Off On Off The start sequence begins with the momentary start command signal from the APU CONTROL panel. 70 + 60 msec Start fuel valve De-energized Off On Off 85 Ignition turned off Off On Off 95 + 3 sec APU Ready To Load Off Off ENGINE FUEL AND CONTROL SYSTEM DESCRIPTION CONTINUED This opens the fuel servo valve. The start fuel valve is energized open at 3% gas generator (Ng) speed and fuel flows to the two start nozzles and is ignited by the two ignitors. When 70% Ng speed is reached the main fuel valve is energized open and fuel flows to six additional main fuel nozzles. START LIGHT WARN LIGHT RUN LIGHT % RPM On A flow divider valve that is located in the fuel solenoid manifold assembly opens when fuel pressure reaches 300 psid (2068.4 kPad). The valve makes sure proper fuel pressure is maintained and limited to the start nozzles. The start fuel valve stays open until 70% Ng speed is reached and then is deenergized closed. At this time, the purge check valve, located down stream of the start fuel valve, opens to push residual fuel from the start fuel manifold and nozzles. The start fuel check valve is opened by APU compressor air pressure (PCD) when fuel pressure is no longer present. The valve supplies a continuous PCD air flow through the nozzles during APU operation. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 38 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - START SEQUENCE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 39 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL SYSTEM DESCRIPTION CONTINUED STOP SEQUENCE The stop sequence can begin in one of two methods: Full Authority Digital Electronic Control (FADEC) generated auto shutdown: • • • • • • • • • • • Illogical switch input example: - APU ON switch pushed while either Weight Off Wheels (WOFFW) signal from the PSEU is present Airborne operation Low oil pressure Both speed signals failed Over-speed Under-speed Both EGT probes fail High EGT Main fuel valve failed (open, short, stuck) High oil temperature FADEC internal timer fail Aircraft generated auto shutdown: • • • • • APU fire detection system APU fire bottle low pressure Generator overheat #1 WOW indicating air mode #2 WOW indicating air mode At any time that a major failure is detected by the FADEC, the APU is automatically shutdown. The ‘fault’ signal closes the fuel valves and illuminates the APU Caution light in the flight compartment, the WARN annunciation on the APU control panel, and extinguishes the RUN light. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 40 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - STOP SEQUENCE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 41 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION FUEL CONTROL ASSEMBLY The servo valve is energized open at start up. The fuel servo receives milliamp signals from the Full Authority Digital Electronic Control (FADEC) to maintain 100% Ng speed during all APU load conditions. In the shutdown sequence the FADEC maintains current to the fuel servo valve for 0.5 seconds and then de-energizes the valve. The differential pressure valve is in parallel with the fuel servo valve to maintain a constant 100 psi differential pressure across the fuel servo valve. This results in a fuel flow linear relationship to the servo current command from the FADEC. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 42 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU FUEL CONTROL ASSEMBLY LOCATION TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 43 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED START FUEL VALVE The start fuel valve is installed on the fuel solenoid manifold assembly. The valve is energized open at 3% Ng speed and fuel flows to the two start nozzles and is ignited by the ignitors The valve stays open to 70% Ng speed + 60 msec and then is de-energized closed. MAIN FUEL VALVE The main fuel valve is installed on the fuel solenoid manifold assembly. The valve is energized open when 70% Ng speed is reached to allow fuel flow to the six main fuel nozzles. The valve stays open during engine acceleration and throughout engine operation. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 44 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU START FUEL VALVE AND MAIN DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 45 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED COMBUSTOR DRAIN CHECK VALVE The valve is threaded into the combustor drain boss and is closed, during engine operation, by air pressure in the combustor housing. The valve is spring loaded open when the engine is shut down, to let any accumulation of fuel in the combustor drain into the combustor drain system. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 46 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - COMBUSTOR DRAIN AND CHECK VALVE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 47 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED FLOW DIVIDER (AND PURGE CHECK VALVE) The flow divider valve is located in the fuel solenoid manifold assembly. The valve opens when start fuel pressure reaches 300 psi (2068.4 kPa). This will make sure proper fuel pressure is maintained and limited to the start nozzles. The purge check valve is spring loaded and is opened by the engine compressor air pressure (PCD) when start fuel pressure is not present. The open purge check valve routes a continuous flow of air from the compressor to purge the residual fuel from the start fuel manifold and start nozzles. The air flow also cools and prevents the fuel from coking the start nozzles. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 48 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU FLOW DIVIDER AND PURGE CHECK VALVE TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 49 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED START FUEL NOZZLE The two start fuel nozzles are threaded into individual nozzle assemblies and installed in the combustor housing with bolts. START FUEL MANIFOLD The flexible start fuel manifold is located on the engine combustor housing and supplies fuel to the two start fuel nozzles. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 50 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - START FUEL MANIFOLD AND NOZZLES LOCATOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 51 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED MAIN FUEL NOZZLE The six fuel nozzle assemblies are installed in the combustor housing with bolts. MAIN FUEL MANIFOLD The main fuel manifold is flexible and is attached around the engine combustor housing. The manifold supplies fuel to the six fuel nozzle assemblies. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 52 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - MAIN FUEL MANIFOLD AND NOZZLES DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 53 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED FUEL FILTER ASSEMBLY The low-pressure, 10 micron fuel filter protects the fuel control from contamination. The filter differential pressure indicator and bypass valve are located on the side of the filter housing. The impending bypass indicator gives a visual warning when fuel flow through the filter becomes restricted and a pressure differential of 1 to 2 psid (6.89 to 13.8 kPad) occurs. The filter bypass valve will open at a pressure differential of 7 psid (48.3 kPad) to let fuel bypass the filter and maintain flow through the system. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 54 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - FUEL FILTER LOCATOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 55 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED DATA MEMORY MODULE The Data Memory Module (DMM) is a solid state unit located on the bottom side of the Auxiliary Power Unit (APU). The DMM stores APU operating hours, fault history (50 shutdowns and advisory faults), plus APU and Full Authority Digital Electronic Control (Full Authority Digital Electronic Control (FADEC) serial numbers. The FADEC updates the DMM at the same time it updates its own Non-Volatile Memory. If the FADEC or the DMM is replaced, the data is transferred to the unit that has been changed automatically. AMBIENT PRESSURE SENSOR The Ambient Pressure Sensor (APS) is mounted on the left side of the air inlet assembly and senses air inlet pressure to the engine. Pressure signals are sent to the FADEC for altitude correction of the fuel scheduling. After ready to load, which occurs at 95% plus 3 seconds, ambient pressure is used by the FADEC to set the minimum and maximum fuel set points. If the APS fails, the FADEC uses the preset standard day/pressure altitude value. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 56 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - DMM AND APS LOCATOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 57 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT ENGINE FUEL AND CONTROL COMPONENT LOCATION AND DESCRIPTION CONTINUED SPEED SENSOR The sensor is installed to the air inlet housing. The sensor is a single probe, dual coil device. The magnetic probe extends through the air inlet housing and aligns with the lobes on the quill shaft. The dual coils give redundant speed signals. The sensor generates redundant sinusoidal signals, which are transmitted to the FADEC and used for start sequencing and speed sensing (over-speed and under-speed). The two signals are averaged by FADEC to give the rated speed. If the difference between the two signals exceeds 5%, the FADEC will use the higher value. Failure of one signal will result in an advisory fault. Loss of both signals will cause an automatic APU shutdown. THERMOCOUPLE The two single-element, closed end, chromel/alumel thermocouples are located on the APU exhaust flange and extend into the exhaust gas stream. The thermocouples are installed 90° apart, at the five and eight o’clock positions and supply millivolt signals that are used by FADEC for exhaust gas temperature sensing. The FADEC averages the two signals to give the exhaust gas temperature. If the difference between the two thermocouples is greater than 93.3°C (200°F), the FADEC will use the higher value. An open or short failure of one thermocouple will result in an advisory message. Failure of both thermocouples will cause an APU shutdown. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 58 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU SENSORS DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 59 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT IGNITION/STARTING INTRODUCTION The Auxiliary Power Unit (APU) ignition system is used to initially start the fuel burning and the starter system provides the initial rotation of the APU. The starting and ignition system includes the controls, indicators and switches for automatic starting, and acceleration of the APU to a sustained running speed of 64,154 RPM at 100%. GENERAL DESCRIPTION The Ignition/Starting system includes the components that follow: • • • • Auxiliary Power Unit (APU) Control Panel Starter/Generator Ignition Exciter (1) Ignitor Plugs (2) The APU is started by pushing the START switch on the APU CONTROL panel. The start sequence and operating sequence are then automatically controlled by the Full Authority Digital Electronic Control (FADEC). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 60 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU IGNITION SYSTEM DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 61 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT IGNITION/STARTING COMPONENT LOCATION AND DESCRIPTION APU CONTROL PANEL The panel is the input and information output to the flight crew. The APU CONTROL panel is installed on the right side of the flight compartment overhead panel. Four switches and one annunciator are installed side-by-side. The panel is supplied with 5V DC background lighting when selected. The START switch is a momentary switch, the other switches are alternate actuation switches. Pushing the power (PWR) switch applies 28V DC power from the right side essential bus CB (F7) to the Full Authority Digital Electronic Control (FADEC), enabling APU functions and the control panel advisory lights. This also closes contacts in the Power Control Relay (K10) which supplies 28V DC from the right side essential bus CB (R7) to the FADEC. This power also is used to close the APU fuel relay (K3). Relay (K3) now will supply 28V DC from the left essential bus CB (S7) to open the wing fuel valve. Pushing the START switch starts the auto start sequence. The FADEC signals the Generator Control Unit to begin the start sequence. The relays are located on the relay panel behind the wardrobe. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 62 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU CONTROL PANEL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 63 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT IGNITION/STARTING COMPONENT LOCATION AND DESCRIPTION CONTINUED The outlet duct, also of fireproof composite construction, is bolted to the QAD at the inboard end. The outlet duct incorporates a fireproof silicon composite seal at the outboard end where it interfaces with the tail-cone right side access door. The brushes and commutator are completely enclosed within the casting and are therefore not exposed to the tail-cone fire zone. A bi-metallic strip in the stator assembly provides a means for indicating a starter/ generator overheat. STARTER/GENERATOR The DC Starter/Generator is an electromagnetic rotating machine that has two distinct modes of operation. In “Starter Mode” the machine converts electrical 28V DC power into mechanical torque that is used to drive the Auxiliary Power Unit (APU) rotor for engine starting. In “Generator Mode” the machine converts mechanical power from the gearbox into electrical 28V DC power. The modes of operation are controlled by the Full Authority Digital Electronic Control (FADEC) and the Generator Control Unit (GCU). The 28V DC, 400 A starter/generator is mounted on the forward face of the gearbox, coaxial with the rotor. The unit comprises the starter/generator and a quick attach/detach adapter (QAD). The QAD incorporates the cooling air outlet. The APU gearbox pad conforms to standard MS 3327-2, and the QAD is attached to it via six studs and self-locking nuts. A V-band clamp attaches the starter/generator to the QAD. When an overheat condition is detected the FADEC will receive a APU shutdown signal from the Generator Control Unit (GCU) and the APU will shutdown. The GCU will turn on the GEN OHT lamp on the APU CONTROL Panel and the FADEC will turn on the APU caution lamp on the Caution Warning Panel. The Starter/Generator is a four pole machine, with a design speed of 12,000 RPM. During the start sequence it is energized by 28V DC from the aircraft electrical system. At 50%speed the starter is de-energized. When the APU reaches 95% speed plus 3 seconds the generator function is available. The generator supplies electrical power to the aircraft right main bus and has the same generating capacity as the aircraft main generators. Although the generator is of the same capacity as the main engine generators they are not interchangeable. The (GCU) regulates the generator output and controls the starter/generator contactor. The GCU is located under the cabin floor near the main engine GCU. The drive spline is of the “wet” type, lubricated by air oil mist from the gearbox. Any oil leakage will be entrained in the cooling airflow to exit overboard through the discharge duct, and therefore will not enter the tail-cone fire zone. The starter/generator is an air cooled unit and has an integral cooling fan. The inlet system comprises a short titanium inlet duct with a metal mesh screen at the tail-cone penetration located in the lower forward skin, an interconnecting fireproof duct, and an inlet duct which is part of the starter/generator. Each end of the composite duct is secured and sealed with a fireproof silicone composite boot and hose clamps. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 64 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - STARTER/GENERATOR LOCATOR TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 65 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT IGNITION/STARTING COMPONENT LOCATION AND DESCRIPTION CONTINUED IGNITION EXCITER The ignition exciter is installed on the left side of the engine. The exciter is a capacitor discharge unit that uses 28V DC to give intermittent high voltage to the ignitor plugs. Operation of the exciter is controlled by the FADEC during the start sequence. The exciter generates high voltage outputs that can be lethal. When replacing the ignition exciter, be sure electrical power is removed from the exciter for a minimum of 5 minutes. Disconnect ignitor cables from the ignitor plugs. Discharge the exciter by touching the ignitor cable ends to the ignitor plug shells. Be sure exciter is fully discharged before removing the ignitor cables and exciter. IGNITOR PLUGS Two ignitor plugs are installed, one on the left side and one on the right side of the engine. The ignitor plugs are threaded into the engine combustor housing. The 10 millimetre, gap type ignitors supply a high voltage intermittent spark that ignites the fuel-air mixture in the combustor. The ignitors are connected to the ignition exciter by two separate shielded ignition cables. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 66 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU IGNITION SYSTEM DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 67 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT AIR INTRODUCTION The Auxiliary Power Unit (APU) bleed air system supplies compressed air for the Environmental Control System (ECS). GENERAL DESCRIPTION The aircraft air inlet supplies air to the Auxiliary Power Unit (APU) air inlet assembly that is then compressed by the APU compressor. The compressed air is used in the operation of the APU and to supply air to the aircraft Environmental Control System (ECS). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 68 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU BLEED AIR SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 69 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT Modulating bleed air flow in response to the APU exhaust gas temperature limits allows generator loads to have priority over bleed air delivery. AIR BLEED VALVE SYSTEM DESCRIPTION The bleed valve is an electro-pneumatic butterfly valve that is normally closed. The Auxiliary Power Unit (APU) bleed valve is controlled by the Full Authority Digital Electronic Control (FADEC). When BL AIR OPEN is selected on the APU CONTROL PANEL, the FADEC will fully open the bleed valve. Bleed air flow is now controlled at the Environmental Control System (ECS) pack inlet flow control and shutoff valve by the ECU control in accordance with the mass flow schedule. The valve is located on the APU combustor housing bleed air duct and controlled by the Full Authority Digital Electronic Control (FADEC). The FADEC receives a signal from the BL AIR switch on the APU CONTROL panel. The FADEC will modulate the APU bleed valve in the closed direction as required to limit the APU exhaust gas temperature (EGT) to 692°C (1278°F), overriding the ECS pack inlet valve. Selecting either engine BLEED 1 or 2 switch ON will interrupt the bleed demand signal to the FADEC via relay K11; the FADEC will close the APU bleed valve. A leak in either the APU or dorsal duct will cause the associated temperature switch to close. This will close a relay which interrupts the bleed demand signal to the FADEC. The K6 relay incorporates a ground latching circuit which requires the APU bleed switch or POWER to be cycled to unlatch. The relay is located on the relay panel behind the wardrobe. To prevent APU reverse wind-milling in the event that the bleed valve fails open, a check valve is installed in the APU bleed pipe in the rear fuselage. . Control of the bleed valve is accomplished by the bleed servo valve receiving milliampere signals from the FADEC. The FADEC receives signals from the APU exhaust gas thermocouples and the flight compartment APU bleed air switch. The FADEC uses signals from the APU exhaust thermocouples to control the bleed valve during bleed air delivery. If the APU exhaust temperature reaches 692°C (1278°F) the bleed valve will be modulated to reduce bleed air flow. This will allow the bleed valve to deliver the maximum air flow without exceeding the APU exhaust gas temperature limits. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 70 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - BLEED VALVE AND DUCT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 71 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT AIR CONTROLS AND INDICATORS BLEED AIR SWITCH When the BL AIR push switch on the Auxiliary Power Unit (APU) Control Panel is pushed, 28V DC from the APU control circuit breaker (F7) is directed through the engine bleed logic relays (K6, K11) to the APU Full Authority Digital Electronic Control (FADEC). The FADEC will then command the bleed valve to open. The logic relay K11 prevents the selection of APU bleed air when either #1 or #2 engine bleed air is selected. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 72 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU CONTROL PANEL AND BLAIR SWITCH ELECTRICAL SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 73 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT AIR CONTROLS AND INDICATORS CONTINUED OVER HEAT/DUCT LEAK In the event of a bleed supply over-temperature or a leak in the duct which supplies air to the Air Conditioning Unit, the #1 and #2 BLEED HOT caution lights will come on and the green OPEN light on the APU CONTROL panel will go out. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 74 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - APU BLEED HOT TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 75 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT During engine operation, centrifugal force lets the oil flow through the internal passages to the ball and roller bearings. Oil return from the rotor bearings is accomplished by gravity flow to the gearbox oil sump. OIL The oil system contains the components that follow: INTRODUCTION The Auxiliary Power Unit (APU) oil system supplies pressurized oil to the gearbox and the engine rotor assembly to lubricate and cool the gears and the bearings. GENERAL DESCRIPTION A positive displacement gear type oil pump is located inside the gearbox and supplies oil flow to the system. The oil pump supplies oil to the gearbox and the engine rotor assembly through the fuel/oil cooler where the oil is cooled by fuel. If oil flow is restricted through the cooler, a cooler bypass valve opens at 65 to 70 psig (448 to 483 kPag). The valve is located in the gearbox. The oil is filtered through a 10 micron replaceable filter and then flows into the oil system. • • • • • • • • • • • • • • Gear type pump De-prime valve Fuel/oil cooler Fuel/oil cooler bypass valve Filter Pressure relief valve High temperature switch Low pressure switch Oil/air separator Carbon seal drain Labyrinth seal Oil filler port Sight glass Magnetic chip detector/drain plug The oil pressure relief valve, located between the oil filter and the gearbox oil jets, maintains the system oil pressure of 60 psig (414 kPag). The valve is a non-adjustable component. High oil temperature and low oil pressure switches monitor the oil system. If either low oil pressure or high oil temperature condition occurs, the Auxiliary Power Unit (APU) will automatically shutdown. The gears and bearings are lubricated and cooled by oil jets and oil mist that is generated by the rotating gears. The oil/air separator is part of the fuel control gear and separates the oil from the air inside the gearbox. The oil returns by gravity to the oil sump and the air is vented overboard through the drain mast vent. Lubrication and cooling of the rotor bearings is supplied by the gearbox oil pressure system. Oil is injected into the hollow pinion shaft that is splined into the rotor shaft. The pinion shaft delivers oil to the passages located inside the rotor shaft. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 76 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - OIL SYSTEM SCHEMATIC TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 77 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT OIL FILTER OIL Oil filtration is supplied by a disposable 10 micron filter. The oil filter bypass valve assembly includes a visual impending by pass indicator and a bypass valve. The indicator is visible when differential pressure across the filter reaches 60 to 80 psid (414 to 552 kPad). The bypass valve opens when the differential pressure across the filter reaches 105 to 125 psid (724 to 862 kPad). COMPONENT LOCATION AND DESCRIPTION OIL PUMP A positive displacement gear type oil pump is located inside the gearbox and supplies oil flow to the system. DE-PRIME VALVE OIL PRESSURE RELIEF VALVE The oil pressure relief valve, located between the oil filter and the gearbox oil jets, maintains the system oil pressure of 60 psig (414 kPag). The valve is a non-adjustable and non-replaceable component. The de-prime valve is a solenoid operated valve and is located on the lower, right side of the gearbox. The valve is energized open by the Full Authority Digital Electronic Control (FADEC) to prevent the oil pump from supplying oil during engine start-up and shutdown. This reduces the load on the starter/generator during cranking to improve acceleration. Above 50% engine speed the de-prime valve is de-energized closed and the oil pump produces oil flow. During engine shutdown the de-prime valve is energized open by the FADEC for 16 seconds, to prevent oil pump output and to let the oil remaining in the system drain back into the sump. FUEL/OIL COOLER The Fuel/Oil cooler is located on the lower, right side of the gearbox. The cooler is a fuel/oil heat exchanger that uses fuel from the fuel control to supply cooling of the oil. FUEL/OIL COOLER BYPASS VALVE The valve is located in the gearbox. In the event the oil flow is restricted through the cooler, the cooler bypass valve opens at 65 to 70 psig (448 to 483 kPag). TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 78 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - OIL SYSTEM COMPONENTS DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 79 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT OIL COMPONENT LOCATION AND DESCRIPTION HIGH OIL TEMPERATURE SWITCH The high oil temperature switch is a normally open switch and closes if the oil temperature is more than 275°F ± 5°F (35°C ± 3°C). A closed switch will result in the Auxiliary Power Unit (APU) shutting down. LOW OIL PRESSURE SWITCH The Low Oil Pressure Switch senses oil pressure downstream of the oil filter. The normally closed switch opens when oil pressure is more than 35 ± 5 psig (241 ± 34.5 kPag) and remains open during normal operation of the APU. Oil pressure is not monitored until the APU has reached 100% speed and the switch has been closed for 12 seconds. A closed switch will initiate a shutdown of the APU. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 80 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT - OIL SYSTEM SWITCHES DETAIL TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - January 2023 Page 81 of 98 BOMBARDIER DHC 8-400 (PWC PW150) AUXILIARY POWER UNIT OIL COMPONENT LOCATION AND DESCRIPTION OIL/AIR SEPARATOR The oil/air separator is part of the fuel control gear and separates the oil from the air inside the gearbox. The oil returns by gravity to the oil sump and separated air is vented overboard through the drain mast vent. CARBON SEAL The carbon face seal prevents oil in the bearing area from entering the compressor. The stationary seal supplies a leak proof seal between the rotating inner race of the roller bearing and the carbon face seal. LABYRINTH SEAL The Labyrinth Seal is pressed on to a machined shoulder located on the hub of the compressor wheel. The seal uses engine compressor air to give a non-contact air seal between the Labyrinth Seal and the bearing area. The air across the seal is vented into the carbon seal drain passage. If oil leaks through the carbon face seal, the Labyrinth Seal prevents oil from entering the compressor. TO BE USED FOR MAINTENANCE TRAINING PURPOSES ONLY ATA 49 - AUXILIARY POWER UNIT Issue 6 - Janua