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United States Army Aviation Center

Fort Rucker, Alabama

April 2007

STUDENT HANDOUT

TITLE: AH64D ENGINES AND RELATED SYSTEMS

FILE NUMBER: 11-0909-4.0

PROPONENT FOR THIS STUDENT HANDOUT IS: COMMANDER, 110th AVIATION BRIGADE ATTN: ATZQ-ATB-ACD Fort Rucker, Alabama 36362-5000 FOREIGN DISCLOSURE RESTRICTIONS: This product/publication has been reviewed by the product developers in coordination with the USAAVNC, FT RUCKER foreign disclosure authority. This product is releasable to students from foreign countries on a case-by case basis.

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TERMINAL LEARNING OBJECTIVE (TLO): At the completion of this lesson the student will: ACTION: Operate the AH-64D, T700-GE-701 and 701C engines. CONDITION: As an AH-64D pilot, given an AH-64D helicopter or training device, with TM 1-1520-251-10/CL. STANDARD: In accordance with (IAW) TM 1-1520-251-10/CL. A. ENABLING LEARNING OBJECTIVE (ELO) #1: ACTION: Identify the characteristics of the T700-GE-701 and 701C engines CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10.

a. General description. (1) The AH-64D Helicopter, depending upon configuration, is equipped with two T700-GE-701 (-701) or T700-GE-701C (-701C) manufactured by General Electric. The engines were designed for ease of maintenance.

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(2) Engine Location. The engines are located in nacelles mounted outboard of the center fuselage, just aft of the main transmission. Engine 1 (ENG1) is mounted on the left side of the aircraft, while Engine 2 (ENG2) is mounted on the right side, as viewed from the rear of the aircraft.

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Figure 3. Engine Characteristics.

. (3) Engine characteristics: (a) The T700-GE-701 engine is a front drive turboshaft engine with a single-spool gas generator section consisting of a six-stage compressor (five vane-axial stages and one centrifugal stage), a through-flow annular combustion chamber, an air-cooled two-stage axial-flow gas generator turbine, and a free two-stage axial-flow power turbine. The power turbine shaft extends through the engine and connects, via a splined shaft, to a nose gearbox. (b) The -701 and -701C engines are 25 inches in diameter.

(c) The -701 and -701C engines have no designated time between overhaul limit and are overhauled on a on-condition basis only.

(d) Maintenance can be accomplished using only ten hand tools.

External lines and hoses for fuel and oil have been reduced by internal routing. Lockwire has been replaced by self-locking nut and inserts.

(e) The -701 weighs 437 pounds dry and the -701C weighs 456

pounds dry. (f) The -701 is 47 inches in length, and the -701C is 46.12

inches in length. (g) If the helicopter has the FCR installed, it will have -701C

engines installed. No FCR installed, the AH-64D may have –701 or -701C, but no mixing of engines.

(h) Output power of the -701 is; 1694 Shaft Horse Power (SHP)

Intermediate Rated Power (IRP) (30 minute limit), 1715 SHP MAX (10 minute limit), and 1723 SHP continuous (2.5 minute limit). The -701C’s output power is; 1800 SHP IRP (30 minute limit), 1890 SHP MAX (10 min limit), and 1940 SHP continuous (2.5 minute limit).

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(4) Engine Position Orientation All locations, clock positions, and direction of rotation will be described as viewed from the rear of the engine/aircraft. The direction of rotation of the engine is clockwise.

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(5) Engine Mounts (a) The engines are attached to the nacelles with primary and secondary mounts. 1. The primary engine mounts consist of the forward inboard mount assembly, aft inboard link assembly, and forward lower mount. 2. The secondary engine mounts consist of the aft lower mount, link assembly, and the aft lower rod assembly. 3. When the engine is installed in the nacelle, the primary mounts will support the engine and take up the vertical and side loads. The secondary mounts will support the engine should a primary mount fail.

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(6) Engine Modules Design: (a) The engine was designed under the modular maintenance concept, allowing replacement of entire subsystems in a minimum amount of time. (b) The engine is divided into four modules: 1. Cold section module 2. Hot section module 3. Power turbine module 4. Accessory section module.

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(c) Cold section module: 1. The cold section module is designed to clean, direct, and then compress the air. The cold section module is the most forward module of the engine. 2. The cold section module is composed of three sections: the inlet section, compressor section, and diffuser section. 3. Inlet section components: a. Swirl frame: The swirl frame directs air into a rotating or swirling motion to the front frame. The swirl frame is housed in the forward structure of the cold section module. It is comprised of 12 fixed swirl vanes that are hollow and permit passage of hot air for anti-icing purposes. b. Front frame: The front frame straightens airflow from the swirl frame for entry into the compressor. The front frame is housed in the main frame.

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c. Main frame: The main frame forms the outer surface of the compressor inlet flow path and is located in the center section of cold section module. d. Scroll case: The scroll case provides a flow path for foreign object removal and cooling air flow for the Digital Electronic Control Unit (DECU) on the –701C or the Electronic Control Unit on the -701. The scroll case is mounted to the aft side of the main frame. 4. Compressor section: a. Compressor stators: The compressor stators direct air flow through the rotors at the most efficient angle and are located forward of each compressor rotor. The compressor stators consist of two stages of variable stators and three stages of fixed stators. b. Compressor rotors:

The compressor rotors compress engine inlet air for combustion, cooling, and bleed air. They are housed in the center of the compressor section. 5. Diffuser section: a. Diffuser case: The diffuser case houses the diffuser and receives compressor discharge air from the compressor section and guides it to the combustion chamber. It is attached to the rear flange to the compressor section and the forward flange of the mid frame. b. Diffuser: The diffuser increases the compressor discharge area, reducing the speed of the airflow, causing the air pressure to increase. The diffuser is mounted inside the diffuser case. c. Mid frame: The mid frame provides the housing for the combustion liner. The mid frame is attached to the rear of the diffuser case. It has ports for attaching 12 fuel nozzles and 2 igniter plugs.

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(d) Hot Section Module: 1. The hot section module provides the necessary area for the mixing of fuel and air for combustion. The hot section module is located aft of the cold section module. 2. The hot section module consists of the combustion liner, stage 1 and stage 2 nozzles, stage 1 and stage 2 gas generator turbine rotors, and a gas generator turbine stator. 3. Combustion liner: The combustion liner provides an area for combustion and is housed inside the mid frame in the cold section module. 4. Stage 1 and stage 2 nozzles: The stage 1 and stage 2 nozzles direct hot expanding gases from the combustion liner to the stage 1 and 2 gas generator turbine rotors. The stage 1 and stage 2 nozzles are located aft of the combustion liner. 5. Stage 1 and 2 gas generator turbine rotors: The stage 1 and 2 gas generator turbine rotors provide the power to drive the compressor rotors. The stage 1 and 2 gas generator turbine rotors are mounted on the aft end of the compressor shaft.

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6. Gas generator turbine stator: The gas generator turbine stator provides the shroud and support assembly for the stage 1 and stage 2 components. This assembly directs the air flow from the stage 2 gas generator rotor to the stage 3 turbine nozzle. It is mounted into the turbine case.

(e) Power Turbine Module: 1. The power turbine module extracts energy from hot expanding gases and converts it into mechanical energy (Shaft Horsepower (SHP)). The power turbine module is located on the aft section of the engine. 2. The power turbine module consists of the stage 3 turbine nozzle, power turbine rotor assembly, and exhaust frame. 3. Stage 3 turbine nozzle: The stage 3 turbine nozzle directs hot gases from the gas generator to the power turbine rotor assembly. This nozzle is housed in the forward section of the turbine case.

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4. Power turbine rotor assembly: The power turbine rotor assembly extracts heat energy from the gas generator and transmits it as mechanical energy to the helicopter drive system. It is attached to the power turbine driveshaft. It consists of the third and fourth stage turbine rotors and the stage 4 turbine nozzle. 5. The Power Turbine (PT) driveshaft is hollow to receive the torque sensor reference shaft (or tube). The torque sensor reference shaft is fastened (pinned) to the PT shaft only at the forward end. The power turbine drives the PT shaft at the aft end of the shaft, and the force to turn the transmission is taken at the front end of the shaft. The PT shaft will torque (twist) commensurate with the amount of torque applied. The greater the torque applied, the greater the amount of twist. Since the reference tube is pinned to the PT shaft only at the front end, the reference tube will always retain its position relative to the front end of the PT shaft. As applied torque causes the PT shaft to twist, the relationship of the aft end of the PT shaft and the aft end of the reference tube changes. The amount of twist in the PT shaft can readily be measured against the reference tube. The amount of PT shaft twist, then, is directly proportional to torque applied. Torque readings will be discussed later in this lesson.

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6. Exhaust frame: The exhaust frame provides a path for hot exhaust gases and supports the “C” oil sump and the aft end of the driveshaft assembly.

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(f) Accessory section module: 1. The accessory section module provides mounting for engine-driven accessories and provides for engine starting. 2. The accessory section module is mounted to the top of the main frame of the cold section module. 3. The accessory section module has internal passages for oil and fuel flow, thus reducing external lines and fittings. 4. Mounting pads and bosses are provided on the front and rear to facilitate installation of accessory section module driven components. 5. The accessory section module is driven by the radial driveshaft and drives the Inlet Particle Separator (IPS).

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(7) Air Turbine Starter (ATS) (a) The air turbine starter rotates the compressor, through the accessory section module, until the engine reaches an Ng speed that permits it to be self-sustaining. (b) The air turbine starter is mounted on the rear of the accessory gearbox, right side. (c) The air turbine starter has a power section and a reduction section. The starter uses a self-contained, wet sump oil system that holds 200 cc of MIL-L-23699 oil or MIL-L-7808 oil. (d) A one way sprag clutch allows the air turbine starter turbine wheel to drive the output shaft. (e) The starter has a decoupler installed in the output shaft that will disengage the starter from the engine if the sprag clutch fails to disengage or if too much air pressure is applied to the starter inlet. (f) To prevent an overtorque condition to the engine, the starter output shaft has a shear section that will shear if the starter torque exceeds 500’inch pounds. (g) The Air Pressure Regulator and Shutoff Valve (PRSOV) provides air in the required amounts from the Integrated Pressurized Air System (IPAS) to the air turbine starter. The air pressure regulator and shutoff valve is coupled to the air turbine starter. (h) The air pressure regulator is an air-actuated solenoid-controlled valve. It is spring-loaded to the closed position and is operated by the No. 1 and No. 2 engine start/off/ignition override switches. (i) The air PRSOV has a mechanical indicator to indicate whether the valve is in the open or closed position.

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(8) Radial Driveshaft (a) The radial driveshaft is driven from the compressor rotor Power Takeoff (PTO) gear to drive the accessory section module. (b) The radial driveshaft is driven by the air turbine starter to rotate the compressor rotors for engine starting. (c) It is located inside the accessory section module on the right side. (d) The radial driveshaft is splined at the lower end and connected to the compressor rotors via a PTO with a bevel gear system.

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(9) Inlet Particle Separator (IPS) The IPS provides separation of foreign particles from the inlet airflow to protect the engine from erosion and damage, and consists of following components. (a) Swirl frame The swirl frame has 12 fixed canted vanes that cause rotation of the incoming air to rotate and separate heavier particles from the lighter air. These particles, and a portion of the inlet air, are discharged into the collection scroll case. (b) Collection scroll case The collection scroll case provides the flow path for particles to the IPS blower. It also has an opening at the 6 o’clock position for cooling of the engine Electronic Control Unit (ECU) (-701) or Digital Electronic Control Unit (DECU) (-701C). (c) IPS blower The IPS blower, driven by the AGB at 22,000 rpm at 101% Np, draws particles from the collection scroll case and vents them overboard. (d) Overboard vent The overboard vent is a duct which allows the separated particles to exit the engine nacelle through the exhaust nozzels.

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(10) Engine Cooling and Exhaust System The engine cooling and exhaust system work together. The exhaust system assists the engine in development of cooling airflow. The engine cooling air cools the exhaust gases and components. (a) Engine Cooling 1. Each engine is cooled by air routed through the engine nacelle. Airflow is drawn into the nacelles by the infrared suppressor developing a low pressure area in the rear of the nacelle. This low pressure area draws cool ambient air from the transmission bay through the engine firewall louver assembly and the engine nacelle top and bottom fixed louvers during engine operation. 2. Additionally, each nacelle has an engine cooling louver on the underside of the nacelle to aid in cooling after engine shutdown. These cooling louvers are moveable doors controlled by 5th stage bleed air. The moveable door is shut by engine bleed air pressure during engine operation and spring loaded open during engine shutdown. (b) Exhaust System 1. The engine exhaust components function with a dual purpose. They allow hot exhaust gases to be expelled from the engine and by system design provide Infrared (IR) suppression. 2. The primary nozzle provides a path for engine exhaust gas airflow, which creates a low pressure that draws cooling air through the engine compartment.

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3. The secondary nozzles mix exhaust gases from the engine with ambient air for exhaust gas cooling. The insides of the secondary exhaust nozzles are painted with low-reflective paint to reduce IR signatures. 4. The inlet particle separator transition duct provides exit for foreign objects from the inlet particle separator, and provides additional cooling air for lowering engine exhaust gas temperature. Check on Learning: 1. On which side of the AH-64D is ENG 1 located? _________________________________________________________________________ 2. Engine rotation direction is to the 3 o’clock position, is that clockwise or counter-clockwise? _________________________________________________________________________ 3. Output power of the –701 and -701C is the same Shaft Horse Power (SHP) at Intermediate Rated Power (IRP). True or False? _________________________________________________________________________ 4. Primary engine mounts will support the engine and take up the vertical and side loads, but will the secondary mounts support the engine if a primary mount should fail? _________________________________________________________________________ 5. Name the four engine modules. _________________________________________________________________________ 6. The ATS serves what purpose? _________________________________________________________________________ 7. What is the purpose of the radial driveshaft? _________________________________________________________________________ 8. What is the purpose of the IPS? _________________________________________________________________________

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B. ENABLING LEARNING OBJECTIVE (ELO) #2: ACTION: Identify the functions of the engine fuel system CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10.

a. Engine Fuel System: (1) The engine fuel system provides pressurized, filtered fuel in the required amounts for proper combustion for varying power demands. (2) The engine fuel system components consist of: (a) Fuel boost pump (b) Fuel pressure sensor (c) Fuel filter and bypass sensor (d) Hydromechanical Unit (HMU) (e) Overspeed and Drain Valve (ODV) (f) Fuel manifold and injectors

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(3) Fuel boost pump: (a) The fuel boost pump draws fuel from the fuel system and increases fuel pressure to the HMU. (b) The boost pump is mounted on the front of the accessory module section just left of center. (c) The fuel boost pump is an engine-driven, non-self-priming, suction and pressure pump which ensures negative pressure reducing fire hazard if fuel system is damaged.

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Figure 20. Fuel Pressure Sensor

(4) Fuel Pressure Sensor (a) The fuel pressure sensor monitors fuel pressure between the boost pump and the HMU. (b) The sensor is located on the left side of the accessory gearbox. (c) The fuel pressure sensor is a normally closed switch. During normal operation, fuel pressure will open the switch when fuel pressure increases to 10 to 11 psi. (d) If the engine fuel pressure drops below 9.0 psi, the switch will close and the SP will receive a complete circuit signal. The SP will send a caution message to the UFDs (ENG1 FUEL PSI LOW). Additionally, the SP will signal the DP to display a message to the MPDs (ENG 1 FUEL PSI LOW). (e) Two seconds after the SP is powered up on battery power, the SP will verify that the pressure switch is in the normally closed position. If the switch is open or disconnected, the SP will send an advisory message to the UFDs (#1 FUEL SNSR FAIL). After AC power is applied, the SP will send a fault message to the MPDs (#1 FUEL SNSR FAIL).

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Figure 21. Fuel Filter/Fuel Bypass Sensor

(5) Fuel filter: (a) The fuel filter filters the fuel coming from the engine fuel boost pump. The filter is a disposable 30-micron filter element with bypass capabilities. (b) The fuel filter is located on the forward lower left side of accessory module section. (6) Fuel bypass sensor: (a) The fuel bypass sensor is a pressure sensitive switch that will close when the fuel filter is in a bypass condition. The fuel filter bypass sensor closes when differential pressure across the fuel filter reaches 18 to 22 psid. When closed, the SP will receive a complete circuit signal. The SP will send a caution message to the UFDs (ENG 1 FUEL BYPASS). The SP will also signal the DP to apply a message to the MPDs (ENG 1 FUEL BYPASS). (b) The filter housing has an impending bypass indicator that will cause a red indicator button to protrude when the differential pressure across the filter reaches 8 to 10 psid. This indicator can be inspected at pre-flight and post-flight inspections.

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(7) Hydromechanical Unit (HMU) (a) The HMU provides high pressure fuel pumping, metering, flow computation, pressurization, and shutoff. The HMU provides Ng speed control, compressor variable geometry scheduling and actuation, and anti-icing and start bleed valve actuation. (b) The HMU is mounted on the aft center of the accessory module section. The HMU controls and inputs are: 1. Power available spindle: The power available spindle provides input from the power lever for shutoff, start, ground idle, and maximum continuous Ng speed. The power available spindle is mounted on the rear of the HMU at the upper right side. 2. Load demand spindle: The load demand spindle provides an input from the collective stick for different load demands. The load demand spindle is mounted on the rear of the HMU at the lower right side.

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3. DECU/ECU inputs: The HMU responds to electrical inputs from the DECU/ECU to precisely trim Ng speed. This provides for both power turbine speed control and turbine temperature limiting for more exact load share control. The HMU can deactivate the DECU/ECU in the event of a DECU/ECU failure by movement of the power lever to the LOCKOUT position. 4. Engine parameters: The HMU responds to sensed engine inlet air temperature (T2), compressor pressure (P3), and gas generator speed (Ng) which influence fuel flow and variable geometry position of the stator vanes. Additionally, Ng overspeed protection is provided mechanically by the HMU in the event the gas generator exceeds 110% ± 2 Ng. The reaction of the HMU to an Ng overspeed results in an engine flameout, the same as an Np overspeed. However, the Ng overspeed flameout is a result of centrifugal flyweights closing a fuel orifice within the HMU stopping fuel flow to the ODV.

(8) Overspeed Drain Valve (ODV) (a) The ODV delivers fuel through the main fuel manifold to the 12 fuel injectors for starting and operation. (b) When the engine is shut down, the ODV purges the fuel injectors and manifold of fuel to prevent coking of the injectors. (c) During an engine overspeed, the ODV stops fuel flow to the injectors and diverts it back to the HMU inlet to prevent destructive Np overspeed.

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(d) The ODV incorporates three valves to control its functions: the selector valve, inlet and pressurizing valve, and the overspeed solenoid valve. 1. The selector valve and the inlet and pressurizing valve operate for the engine start, operation, and engine shutdown functions. 2. The overspeed solenoid valve receives an electrical signal from the DECU/ECU when an overspeed condition exists (119.6% ± 1 Np). This opens the solenoid valve stopping fuel flow to the injectors.

(9) Fuel Manifold and Injectors (a) The fuel manifold receives fuel from the overspeed drain valve and delivers it to 12 fuel injectors. The fuel injectors inject fuel into the combustion liner to maintain engine operation. (b) The fuel manifold and injectors are attached to the diffuser and mid frame casing assembly.

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(12) Fuel system operation: (a) Fuel enters the engine fuel system through the engine-driven fuel boost pump. (b) The fuel boost pump increases fuel pressure to 45 psi, and forces it through passages in the gearbox to a pressure sensor and fuel filter. (c) The fuel pressure sensor monitors fuel pressure between the boost pump and the HMU. During normal operation, fuel pressure will open the switch when fuel pressure increases to 10 to 11 psi. If the engine fuel pressure drops below 9.0 psi, the switch will close and the SP will receive a complete circuit signal. (d) The fuel filter has an impending bypass indicator button, which will give a visual indication of fuel filter contamination. The fuel filter has a bypass relief valve that internally bypasses the fuel filter when the filter is dirty. The fuel filter bypass sensor closes when differential pressure across the fuel filter reaches 18 to 22 psid. When closed, the SP will receive a complete circuit signal. (e) The HMU increases the fuel pressure, controls the fuel flow, and routes the fuel to the fuel/oil cooler. (f) Fuel from the HMU flows through the oil cooler for engine oil cooling/fuel warming and into the overspeed drain valve. Fuel from the overspeed drain valve flows to the 12 injectors and into the combustion section to maintain engine operation.

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Check on Learning: 1. What does the engine fuel system provide to the engine? __________________________________________________________________________ 2. The fuel boost pump is an engine driven, non-self-priming, suction and pressure pump, which ensures negative pressure. Why? __________________________________________________________________________ 3. When engine fuel pressure drops below 9.0 psi, the pressure switch will close and the SP will receive a complete circuit signal. The SP will send a caution message to the UFD, and then will signal the DP to display a message on the MPD. Will this illuminate the MSTR CAUT push button and caution tone (Beattle-beattle)? __________________________________________________________________________ 4. Which occurs first, the fuel filter housing red indicator button popping or the UFD message, ENG 1 FUEL BYPASS? __________________________________________________________________________ 5. The HMU provides mechanical Ng overspeed protection to the engine at what percent Ng? __________________________________________________________________________ 6. The ODV receives an electrical signal from the DECU/ECU when an Np overspeed exists, opening the overspeed solenoid valve which stops fuel flow to the injectors (causes flameout). At what Np speed does this occur? __________________________________________________________________________

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C. ENABLING LEARNING OBJECTIVE (ELO) #3: ACTION: Identify the functions of the engine lubrication system CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10.

a. Engine lubrication system: (1) The engine lubrication system is a self-contained, pressurized, recirculating, dry sump system. It stores and distributes engine oil to lubricate and cool engine components. It also provides temporary emergency lubrication for main shaft bearings in the A and B oil sumps. The engine lubrication system consists of the: (a) Lube and scavenge pump (b) Oil filter (c) Oil filter bypass sensor (d) Cold oil relief valve

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(e) Oil pressure transmitter (f) Oil sumps A, B, and C (g) Chip detector (h) Oil cooler (i) Oil cooler bypass valve (j) Oil tank

(2) Lube and Scavenge Pump (a) The lube and scavenge pump is a seven-element gerotor pump with one pressure element and six scavenge elements. (b) The pump provides pressurized oil to the engine components that require lubrication, and scavenges oil from the sumps. (c) The pump is located on the front center section of the accessory module section. (d) There are six scavenge screens that collect large particles before they enter the lube and scavenge pump.

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(3) Oil filter: (a) The oil filter is a disposable 3-micron filter element, which filters oil drawn from the engine oil tank. (b) The filter bowl has an impending bypass indicator that will cause a red indicator button to protrude when the differential pressure across the filter reaches 40 to 60 psid. This indicator shows the need to change the oil filter and can be inspected at pre-flight and post-flight inspections. It has a thermal lockout to prevent the indicator from activating if the oil temperature is less than 100 to 130°F to prevent a false trip during cold starts. (c) The oil filter bypass valve will bypass the oil filter when the differential pressure across the filter slightly exceeds the high setting of the oil filter bypass sensor (80 psid).

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(4) Oil filter bypass sensor: (a) The oil filter bypass sensor is a pressure-sensitive switch that will close when the differential pressure across the oil filter is 60 to 80 psid, indicating the engine oil filter is in an impending bypass condition. This will allow pilot warning before bypassing actually occurs. (b) The sensor is mounted on the forward side of the engine accessory module section. (c) When the oil filter bypass sensor switch closes, the SP will receive a complete circuit signal and send a caution message to the UFDs (ENG 1 OIL BYPASS), with a caution tone. The SP will also signal the DP to apply a message to the MPDs (ENG 1 OIL BYPASS).

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(5) Cold oil relief valve: (a) The cold oil relief valve protects the engine lubrication system from excessive pressure during initial starts. (b) The relief valve is a conventional poppet valve with a cracking pressure of 120 to 180 psi.

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(6) Oil pressure transmitter: (a) The oil pressure transmitter is a variable reluctance type pressure transmitter that supplies an electrical signal proportional to engine oil pressure to the SP. The SP processes the engine oil pressure information and sends it to the DP to be displayed on the MPD ENG SYS page. (b) The SP monitors the oil pressure transducer output and will display the low oil pressure message on the UFDs (ENG 1 OIL PSI LOW) and the MPDs (ENG 1 OIL PSI LOW) when pressure is below 20-25 psi.

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(7) Sumps A, B, and C: The A, B, and C sumps provide cavities for oil scavenging. The sumps house a reservoir to store oil for emergency lubrication. They also house the main engine bearings. (a) The A sump is housed in the front frame cold section module and contains an emergency oil reservoir and main output shaft bearings, # 1, # 2, and # 3. (b) The B sump is housed in the mid-frame hot section module and contains an emergency oil reservoir and main output shaft bearing # 4. (c) The C sump is housed in the exhaust frame, power turbine module and contains main output shaft bearings # 5 and # 6. There are no emergency lubrication provisions in the C sump. (8) Emergency lubrication: (a) Normal operation 1. Oil is continuously supplied to the all three sumps, pressurizing the emergency reservoirs in A and B sumps, keeping them full. This pressure forces oil out the main jet, lubricating the bearings. 2. The emergency jets, using 4th stage bleed air and oil from the emergency reservoir, sprays an oil mist on the bearings, lubricating the bearings. (b) Emergency operation 1. The oil supply to the emergency reservoir is lost; therefore, oil will not be forced out the main jet. Since the main jet receives oil from the top of the reservoir, the oil will not drain through the main jet. 2. The emergency jet receives oil from the bottom of the reservoir through a tube that prevents gravity draining.

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3. The emergency jet, using 4th stage bleed air pulls oil from the emergency reservoir and sprays an oil mist on the bearing, providing approximately 30 seconds of emergency lubrication for the bearings at 75% Ng.

(9) Chip Detector: (a) The chip detector attracts metal particles that may be present in the engine oil system. The chip detector consists of an outer shell with internal magnet, electrical connector, removable screen, and has no fuzz suppression (burning-off) capabilities. (b) The chip detector is located on the forward portion of the engine accessory gearbox. (c) When metal particles bridge the gap on the magnet, the SP will receive a complete circuit signal and send a caution message to the UFDs (ENGINE 1 CHIPS). The SP will also signal the DP to apply a message to the MPDs (ENGINE 1 CHIPS).

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(10) Oil cooler: (a) The oil cooler cools the engine oil by transferring the heat from the oil to the fuel. (b) The oil cooler is a tube and shell type heat exchanger and is mounted on the left front side of the accessory module section. (c) The fuel that is used as the coolant is provided via the boost pump, fuel filter, and HMU.

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(11) Oil cooler bypass valve: (a) The oil cooler bypass valve directs oil to the oil tank when the oil cooler becomes clogged. (b) The bypass valve is mounted on the front center of the accessory module section. (c) The bypass valve is a conventional poppet valve with a cracking pressure of 22 to 28 psi.

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(12) Oil tank (a) The oil tank stores the engine oil supply and is an integral part of the cold section module, main frame. (b) The oil tank holds approximately 7.3 quarts of MIL-L-23699 or MIL-L-7808 oil. It has a gravity fill port with an oil tank cover located at the 2 o’clock position on the tank. (c) The oil level visual indicators are located on both sides of the tank. (d) The oil tank has an oil drain plug at the bottom of the tank and a coarse pickup screen (strainer) near the tank bottom to keep sizable debris from entering the pressure pump inlet.

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(13) Lubrication system operation: (a) The oil is picked up from the oil tank by a self-priming lube pump. The lube pump output pressure varies with RPM and temperature. The minimum oil pressure at all power settings is 22.5 psi and the maximum is 120 psi. (b) Oil flows from the pump through a three-micron disposable filter element. (c) The oil filter bypass valve will bypass the oil filter when the differential pressure across the filter slightly exceeds the high setting of the oil filter bypass sensor (80 psid.) (d) The impending bypass indicator for the filter will pop out at 44 to 60 psid. Once popped, the filter assembly must be removed, inspected, and the button reset. Additionally, the bypass indicator has a thermal lockout to prevent the indicator from activating if the oil temperature is less than 100° to 130°F to prevent a false trip during cold starts. (e) The bypass sensor switch will sense oil pressure differential across the filter. When the pressure differential reaches 60 to 80 psid, the oil filter bypass sensor switch will close. When the oil filter bypass sensor switch closes, the SP will receive a complete circuit signal and send a caution message to the UFDs. The SP will also signal the DP to apply a message to the MPDs. This will allow pilot warning before bypassing actually occurs.

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(f) Oil flows from the filter to the accessory gearbox for gear and bearing lubrication. The cold oil relief valve will open at 120 psi to relieve high oil pressure and return oil to the accessory module section. (g) The oil flows through the oil pressure transmitter which supplies an electrical signal to the SP. The SP provides the oil pressure signals to the DP for display on the MPD ENG SYS page. The oil flows to the A, B, and C sumps. The oil to B sump flows through a check valve that closes on engine shutdown to prevent the oil from flooding the sump. (h) Emergency lubrication for the number 1, 2, 3, and number 4 bearings is provided by the reservoirs located in A and B sumps. Six scavenge pump elements return oil from the sumps. The A sump uses two elements, the B sump uses one element, and the C sump uses three elements. (i) The accessory module section scavenges by gravity flow through the scroll vanes into the oil tank. Each of the lube pump scavenge elements has an inlet screen to aid in fault isolation. (j) Oil flows over the chip detector. When metal particles bridge the gap between the magnet and outer shell, the SP will receive a complete circuit signal and send a caution message to the UFDs. The SP will also signal the DP to apply a message to the MPDs. (k) Oil flows to the oil cooler and into the scroll vanes for cooling and back into the tank. Should the oil cooler or scroll vanes become clogged, the oil cooler relief valve will open at 22 to 28 psi and allow oil to flow directly into the tank.

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Check on Learning: 1. The engine oil filter has an impending bypass indicator that will cause a red indicator button to pop out when differential pressure across the filter reaches 40-60 psid. Will this send a signal to the SP? _________________________________________________________________________ 2. What protects the engine lubrication system from excessive pressure during initial starts? _________________________________________________________________________ 3. The oil pressure transmitter is responsible for sending a low oil pressure signal to the SP. When the SP receives this signal, what is the engine oil pressure? _________________________________________________________________________ 4. Emergency lubrication for the number 1, 2, 3, and 4 bearings is provided by oil misting from jets, using reservoirs in A and B sump. Does the C sump provide any emergency lubrication provisions? _________________________________________________________________________ 5. How long is emergency oil lubrication provided when Ng is 75%? _________________________________________________________________________ 6. Is the engine chip detector fuzz burning or non-fuzz burning. Why? _________________________________________________________________________

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D. ENABLING LEARNING OBJECTIVE (ELO) #4: ACTION: Identify the functions of the engine electrical system CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10.

a. Engine Electrical System (1) The engine uses electrically operated accessories to: control anti-icing airflow, ignite the fuel air mixture in the combustor, and control the engine power level. The engine electrical system provides all electrical power required throughout the engines operating range without primary use of airframe electrical power. In addition, electrical indication and warning devices assist the pilot in engine operation.

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(2) The interconnecting wiring harnesses provide all engine electrical system components power to operate and monitor engine performance. Interconnecting wiring harnesses are color-coded to aid the mechanic. The yellow harness supplies power and control system trim signals. The blue harness passes all overspeed and torque signals. The green harness conducts engine condition monitoring (crewstation instrumentation). The harnesses are sealed and encapsulated to prevent intrusion of oil and liquid moisture. (3) The engine electrical system consists of the following components: (a) Alternator (b) Ignition System (c) Electronic Control Unit (ECU)-701, and Digital Electronic Control Unit (DECU)-701C. (d) Thermocouple Harness (e) Power Turbine (Np) and torque and overspeed sensors (f) History Recorder (-701) and History Counter (-701C) (g) Engine anti-ice/start bleed valve

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(4) Alternator (a) The engine-driven alternator supplies 115 Vac electrical power for the engine electrical system. (b) The alternator is mounted on the front of the accessory gearbox center section. (c) The engine-driven alternator consists of a rotor and a stator. It contains three separate sets of windings for its three functions: Ignition power, ECU/DECU power, and Ng speed signal. It is the loss of any or all of these three windings that will result in the following conditions, depending on the type engine installed:

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1. Alternator failures on –701 with ECU: a. When the engine alternator power is lost completely or the winding for ECU power fails (most severe), the crewstations will lose Np, Torque, and Ng signals. b. Additionally, the engine will increase to maximum power (overspeed) and display ENGINE1 or ENGINE2 OVERSPEED on the UFD and ENGINE1 or ENGINE2 OVERSPEED on the MPD. Engine control will have to be monitored by TGT indication and oil pressure. However, Np overspeed protection (discussed later) will not be lost due to back-up 115 Vac, 400 Hz, airframe power from the generators.

CAUTION

-701: Complete failure of the alternator or of the winding providing Ng speed signal will activate the MSTR WARN light and ENGINE1 OUT or ENGINE2 OUT voice message and UFD messages. The pilot shall check the Nr on ENG page and be prepared to carry out the actions for a high side failure. Thereafter, reference TGT and ENG OIL PSI, along with FUEL PSI ENG and OIL PSI NOSE GRBX messages on the UFD. -701C: Following a complete failure of an alternator, operation of the corresponding engine and all indications from engine instruments will be normal, except that Ng indications will be lost and will activate the MSTR WARN light and ENGINE1 OUT or ENGINE2 OUT voice message and UFD.

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c. When the winding for Ng speed signal is lost, the Ng indication for the affected engine will read 0%. This loss of signal will activate the MSTR WARN light and ENGINE1 or ENGINE2 OUT voice, UFD, and MPD messages. d. When the winding for ignition power is lost, the crew will not be able to restart the engine after shutdown. The power to the ignition exciter and the lead that controls the ignition switch will not function. 2. Alternator failures on –701C with DECU: a. When the engine driven alternator power is lost, or the winding for the DECU fails, airframe 115 Vac 400 Hz power is provided as a backup to prevent the engine from going to maximum power or overspeed. Engine operation and Np and torque signals to the crewstation all remain normal. b. If the winding providing the Ng speed signal to the aircraft is lost, the Ng indication for the affected engine will be 0%. This will cause the MSTR WARN light and ENGINE1 or ENGINE2 OUT to activate. c. When the winding for ignition power is lost, the crew will not be able to restart the engine after shutdown. The power to the ignition exciter and the lead that controls the ignition switch will not function.

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(5) Ignition system components (a) The ignition system provides engine ignition during starting only. (b) The ignition system consists of an exciter that is located on the right side of the engine cold section. The exciter rectifies the alternator voltage to 5000 to 7000 Vdc and applies the voltage to the igniters. (c) There are two electrical ignition leads that are connected to the igniter plugs. Two igniter plugs are located at the 4 and 8 o’clock positions on the mid frame.

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NOTE: Instructor should explain that the DECU is used only on the –701C engine and the ECU is only used on the –701 engine. The operation of the ECU is similar to that of the DECU, except for the hot start prevention, Maximum Torque Rate Attenuator (MTRA), signal validation fault codes, and the differences already covered during alternator malfunctions. (6) ECU/DECU (a) The ECU or DECU is installed below the compressor casing. The ECU and DECU control the engine and provide operational information to the crewstations. (b) The ECU/DECU accepts the following inputs: 1. AC power from the engine driven alternator. 2. T4.5 thermocouple signal for TGT information. 3. Np sensor signal for power turbine governing and indication. 4. Np overspeed/torque sensor signals for load matching and overspeed protection. 5. Np reference adjustment to permit variation of Np speed from 85% to 105%. 6. Torque signal from opposite engine for torque matching.

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7. HMU feedback signal for engine speed stabilization. (c) ECU (-701) operation 1. The ECU monitors the opposite engine torque to provide torque matching/load sharing by increasing power on the lower torque-producing engine to match the higher torque engine. 2. Additionally, the ECU also receives opposite engine torque inputs to enable contingency power. When this input signal is 51% torque or below, contingency power is automatically enabled. However, contingency power is not applied until the flight crew pulls in collective above 860 +/- 12°C. The ECU automatically allows the normal operating engine to increase its TGT limit, thereby increasing its torque output. 3. The ECU incorporates a steady state dual and single engine TGT limiting function, which restricts fuel flow within the HMU to prevent engine overtemperature. a. Dual engine TGT limiting occurs at 860 +/- 12°C (848-872). b. Single engine TGT limiting occurs at 917 +/- 12°C (905-929). c. In the event of an ECU malfunction, system operation may be overridden by momentarily advancing the engine power lever of the affected engine to LOCKOUT and then retarding the lever past the FLY position to manually control engine power. This locks out the ECU from all control and limiting functions except Np overspeed protection. (d) DECU (-701C) operation The DECU provides the same functions as the ECU plus the following enhancements: 1. The DECU can be fully powered by either the engine alternator or airframe 115 Vac 400 Hz power. 2. A Maximum Torque Rate Attenuator (MTRA) function is built into the DECU control logic designed to reduce the risk of exceeding the dual engine torque limit during uncompensated maneuvers. Uncompensated maneuvers are any maneuver where pedal or cyclic inputs are made but no collective input occurs. Large transient torque increases can occur during rapid left hovering turns or rapid roll reversals in flight. a. The MTRA reduces fuel flow to limit the rate of torque increase to 12% per second when transient engine torque exceeds 100% during an uncompensated maneuver. b. Any collective input or when operating in single engine mode will disable MTRA and allow normal torque rate increases. 3. The DECU provides an automatic Hot Start Prevention (HSP), which prevents overtemperature during engine starts.

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When the DECU detects TGT exceeding 900°C with Ng below 60% and Np below 50%, a signal is sent to the ODV shutting off fuel flow to the manifold, which causes the engine to shut down automatically. 4. The DECU has a torque spike suppression algorithm that locks out the torque signal below 35% Np. a. This prevents torque spike indications in the crewstations during startup and shutdown. b. It also prevents yawing of the aircraft during engine restart in flight. 5. The DECU also provides signal validation for selected input signals within the electrical control system. Signals are continuously validated when the engine is operating at or above flight idle. If a failure has occurred on a selected input signal, the failed component or related circuit will be identified by a pre-selected fault code. The checking of fault codes is a maintenance function. See Operator’s Manual, Chapter 2, for Fault Codes.

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(7) Thermocouple harness assembly (a) The thermocouple harness assembly measures the temperature of the gases at the power turbine inlet. (b) The thermocouple harness assembly is mounted around the turbine case, power section module. (c) The DECU/ECU provides the Turbine Gas Temperature (TGT) signal to the SP, which sends it to the Display Processor (DP) for display on the MPD ENG page.

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(8) Np and torque overspeed sensors (a) The sensors are monopole, permanent magnet pickups. The Np sensor monitors the rotation speed of the power turbine driveshaft and provides power turbine speed (Np) signals to the DECU/ECU. (b) The torque and overspeed sensor monitors the rotation speed of the power turbine driveshaft for overspeed protection. It also monitors the relationship of the torque sensing tube reference teeth to the driveshaft teeth as the torque sensing tube twists from engine torque. The torque and overspeed sensor provides torque and overspeed signals to the DECU/ECU. (c) The DECU/ECU sends the Np and torque signals to the SP, which sends them to the DP for display on the MPD ENG page. The DECU/ECU uses the overspeed signal to perform an automatic engine shutdown in the event of an engine overspeed. (d) The Np sensor extends through the exhaust frame strut at the 10:30 o’clock position. The torque and overspeed sensor extends through the exhaust frame strut at the 1:30 o’clock position.

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(9) History Recorder/History Counter (a) The history recorder is mounted at the 2 o’clock position on the swirl frame. (b) The history recorder records and displays Low Cycle Fatigue (LCF) events, time at temperature index, and engine operating hours. NOTE: The history recorder is used for the –701 engine. The –701C uses an engine history counter. The history counter displays are similar to those of the history recorder. 1. The Low Cycle Fatigue (LCF) 1 indicator displays the actual number of times the engine parts experience mechanical stress above 95% Ng. When the engine exceeds 95% Ng, a count is made on the indicator. The indicator will not make an additional count until Ng drops below 50% (40% for –701C), then increases to exceed 95% again. 2. The Low Cycle Fatigue (LCF) 2 indicator displays the actual number of times the engine experiences high thermal stress events. When the engine exceeds 95% Ng, a count is made on the indicator. The indicator will not record another count until RPM drops below 86% Ng, then increases above 95% again. 3. The time/temperature index indicator advances when engine temperature reaches 90% of maximum continuous power temperature. The number of counts is a function of time and temperature. It counts faster as temperature increases. 4. The hours indicator displays actual running time in hours. Running time starts when Ng exceeds 50% and stops when Ng drops below 40% (60% and 55% on –701C).

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(10) Engine anti-ice/start bleed valve The engine anti-ice/start bleed valve, mounted on the mainframe at the 7 o’clock position, controls anti-icing airflow to the engine and bleeds excessive compressor discharge pressure during engine start and low speed acceleration mode. (a) Mechanically controlled by the HMU during starts through the same linkage that positions the Inlet Guide Vanes (IGVs) and variable geometry stator vanes. Opens and closes at different Ng speeds dependent upon ambient air temperature. (b) Electrically selected by the INLET button on the A/C UTIL page. (c) When INLET is enabled the anti-icing airflow (5th stage bleed air) is delivered to the engine via the engine inlet anti-ice valve. Nose gearbox heater blankets also activated (covered in utility systems). (d) The anti-ice/start bleed valve is “Fail Safe” to the open position. This means that the valve is electrically closed and mechanically opened. Therefore, in the event of an airframe electrical system failure, the anti-ice/start bleed valve opens.

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Figure 49. Check Overspeed Test/Generator Reset Panel

(11) Check Overspeed Test/Generator Reset Panel (a) The electrical system additionally provides a ground checking capability for the Np Overspeed system. (b) The CHK OVSP TEST panel is used to verify backup AC power is available for ENG1 and ENG2 circuitry, in the event of an engine driven alternator failure.

WARNING

The T700-GE-701 and T700-GE-701C engine is designed to shut down when an overspeed condition is sensed. The OVSP TEST circuit trips the overspeed protection system at 95 – 97% NP and should never be performed in flight. A power loss will result. Only maintenance is authorized to make this check.

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Check on Learning: 1. With a –701 engine installed, what MPD ENG page indications will be lost with an alternator failure? __________________________________________________________________________ 2. With a –701C complete alternator failure or lose of the Ng winding, what other indications besides the loss of Ng signal will be displayed in the crewstation? __________________________________________________________________________ 3. Once the engine is self-sustained during the start process, are the igniter plugs used any more prior to engine shutdown? __________________________________________________________________________ 4. What are some of the additional functions provided by the DECU that are not available on the ECU? 1. _______________________________________________________________________ 2. _______________________________________________________________________ 3. _______________________________________________________________________ 4. ______________________________________________________________________ 5. _______________________________________________________________________ 5. In the event of an airframe electrical system failure, what position will the anti-ice/start bleed valve be in? __________________________________________________________________________

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E. ENABLING LEARNING OBJECTIVE (ELO) #5: ACTION: Identify engine control system functions. CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10.

a. Engine Control System The engine control system consists of the engine power lever quadrants, the engine chop controls, the load demand system, and the overspeed control system.

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(1) Power lever quadrants: (a) The power levers on the pilot’s and CPG’s power lever quadrants are used to transmit power selections to the HMU via flexible ball-bearing control cables attached to the Power Available Spindle (PAS). The power levers are located on the left console in each crew station. The power quadrants each have NO. 1 (left) and NO. 2 (right) written beneath the power levers to identify which engine they control. Additionally each power lever has a stop release lever under each handle, to allow power levers to advance or retract beyond mechanical stops. (b) The pilot’s quadrant has mechanical stops that prevent the pilot’s and CPG’s power levers from accidentally being moved from FLY to LOCKOUT or from IDLE to OFF positions. The stops are released by squeezing the stop levers. (c) The CPG’s power quadrant has no mechanical stops, but the stop release levers are electrically connected by a solenoid to the PLT release levers so that the mechanical stops on the pilot’s quadrant are activated electrically. Since the CPG stop release levers are electrically operated, electrical power must be applied to manipulate the power levers from the CPG station, Therefore, the ignition switch must be placed in BATT or EXT PWR (with external power applied). (d) To move the power lever from IDLE to FLY requires the rotor brake switch to be OFF, which releases a power lever locking solenoid. (e) Power levers positions: 1. OFF: The off position has no fuel flow to the engines. Fuel is shutoff at the HMU

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2. IDLE: The idle position is for starting and low power ground operation. This position has a mechanical stop to prevent inadvertent movement of the power levers to OFF. 3. FLY: The fly position is the normal position for flight. The engines are under HMU and ECU/DECU control to automatically schedule fuel flow to maintain Np at a constant operating RPM. This position has a mechanical stop to prevent inadvertent movement of the power levers to LOCKOUT. 4. LOCKOUT: This position disables the DECU/ECU automatic fuel metering mode allowing manual control of the engine speed. a. The stop release must be squeezed to release power lever to advance into LOCKOUT. This must be immediately followed by a power lever reduction to a position between IDLE and FLY, to prevent overtemp or overspeed of the engine in LOCKOUT. b. With the power lever in LOCKOUT, advancing the power lever toward FLY will increase engine speed; retarding the power lever toward IDLE will reduce engine speed. NOTE: Advancing the POWER lever of the engine with low torque and TGT to LOCKOUT disables the automatic temperature limiting for the engine. The engine must be controlled manually to ensure that it does not exceed operating limits. 5. The pilot’s quadrant has a rotor brake switch, a master ignition switch, APU start pushbutton, engine start/ignition override switches for engines NO. 1 and NO. 2, and a power lever friction adjustment lever. The engine start (ENG START) switches will be discussed in this section, but other functions will be covered during associated lessons. a. Engine Start/Ignition Override Switch The ENG START switch is a three-position switch, START/OFF/IGN OVRD. The switch is spring-loaded to OFF from the START position but is discreet for the Ignition Override position (IGN OVRD). (1) START (Forward): Momentarily placing the switch into the START position will initiate an automatic start sequence. An ENGINE1 START or ENGINE2 START advisory message will appear on the UFD, and the MPD ENG page will display start status window, with ON in white text when engine start is initiated. Pressurized air is then directed through the start control valve to the air turbine starter. The start sequence will automatically terminate at approximately 52% Ng speed. During engine start, the sequence must be monitored for abort start criteria (TM 1-1520-251-10, Pg. 8-10.1, Para 8-17). (2) OFF (Center): No engine start function.

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(3) IGN OVRD (Aft): Position is discreet and will be used to abort automatic start sequence or disengage air turbine starter output shaft if sprag clutch fails to disengage, which is evident by the ENGINE 1 or ENGINE2 START advisory UFD message remaining illuminated after 66-68% Ng. Additionally, IGN OVRD will be used to cool the engine internal temperature, by initiating a start sequence, turning (motoring) the engine without ignition or fuel being applied. An ENGINE1 or ENGINE2 ORIDE advisory message on the UFD, additionally the MPD ENG page ground format will be display OVRD in start status window when the switch is in the IGN OVRD position.

Figure 52. Collective Flight Grip/CHOP Button (2) Engine CHOP Control a. The guarded chop (CHOP) button on the flight grip of the collective provides a means to immediately and simultaneously reduce both engines electronically to idle.

CAUTION Application of collective during CHOP operations will cause Load Demand system to allow the engines to spool up. b. Raising the red spring loaded guard and pressing the button will remove the Np reference from both engines ECU/DECU. 1. When the Np reference is removed, the engines will immediately decelerate to idle speed.

Engine CHOP Button

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2. When the engine chop is selected an ENG CHOP warning message will be appear on the UFD and a voice message will announce “Engine Chop”.

CAUTION

Conditions permitting, POWER levers should be retarded to IDLE before resetting CHOP button. c. Pressing the CHOP switch a second time will reapply the Np reference signal to both engines 1. When the Np reference is reapplied, both engines will immediately accelerate to the governed speed referenced by the position of the power lever. 2. The ENG CHOP warning message on the UFD will blank.

CAUTION

With the POWER levers in FLY, resetting the CHOP button will cause an erroneous ENG1 and ENG2 OUT warning to be activated. d. To reset the engines, both power levers should be retarded to the IDLE position before the engine CHOP switch is pressed. This will prevent rapid and simultaneous engine acceleration to the FLY governed speed while minimizing excessive torque application to the airframe and drive train.

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(3) Load Demand System a. Collective engine droop potentiometer 1. The collective engine droop potentiometer provides a collective stick position input to the number 1 and number 2 engine DECUs/ECUs for droop (a decrease in engine RPM when power is applied) compensation. 2. The collective engine droop potentiometer is mounted to the canted bulkhead and at the base of the collective control stick assembly in the pilot’s crew station. 3. The collective droop potentiometer is a dual-wound potentiometer, which generates an electrical signal proportional to the amount of stick movement. 4. The collective engine droop potentiometer is provided +15 Vdc by both DECUs/ECUs. The output of the potentiometer is applied to both engine DECUs/ECUs to aid in maintaining 101% Np during power demand changes (collective stick movement). b. Turbine Speed Control Unit 1. The turbine speed control unit enables setting the reference Np signals to the DECU/ECU to aid in controlling fuel flow to both engines. 2. The turbine speed control unit is mounted on the forward bulkhead in the aft avionics bay. The turbine speed control unit is a sealed electronic unit with a RPM (Np) reference adjustment screw.

Collective Engine Droop Potentiometer

Turbine Speed Control Unit HMU

ECU/DECU

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c. HMU Spindles 1. The power available spindle converts push-pull motion from the power levers to rotary motion of the HMU input shaft. 2. The load demand spindle converts push-pull motion from the collective sticks to rotary motion of the HMU input shaft. 3. The power available spindle is located on the upper aft portion of the HMU. 4. The load demand spindle is located on the lower aft portion of the HMU. 5. The HMU will respond to both of the spindles input to adjust or meter fuel mechanically, and the ECU/DECU will respond with electrical fuel metering to the spindle inputs as well. (4) Np Overspeed Protection System (OPS) The OPS prevents destructive turbine overspeed. The system receives power turbine speed signals from the torque and overspeed sensors located in the exhaust frame. If the Np meets or exceeds 119.6± 1%, two frequency sensing circuits (CKT A and B) output a signal to the overspeed system which causes the ODV to shut off fuel flow to the engine. Check on Learning: 1. Which power lever quadrant requires electrical power (BATT or EXT PWR) to manipulate engine power levers? _________________________________________________________________________ 2. When a power lever is advanced into LOCKOUT, what automatic features are lost? _________________________________________________________________________ 3. What are three conditions that would require the use of the ignition override switch? _________________________________________________________________________ 4. What is the condition of both engines once the engine chop button is activated? _________________________________________________________________________ 5. What are the Power Available Spindle (PAS) and the Load Demand Spindle

(LDS) on the HMU attached to in the crewstations?

_________________________________________________________________________

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F. ENABLING LEARNING OBJECTIVE (ELO) #6: ACTION: Identify MPD engine interface display features. CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10.

a. MPD Engine (ENG) page display formats The engine operational parameters are displayed on the MPD ENG page. The ENG page has three formats: a “Ground” format, an “In-flight” format, and an “Emergency” format. Each format has different display features and conditions that are dependent on the engine and related systems operating modes.

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(1) ENG Page “Ground” Format (a) After APU power up or AC power applied, the left MPD in both crew stations defaults to ENG ground format page. (b) ENG page ground format will remain until both engines are running and power levers are in FLY. (c) The ENG ground format will also be displayed if the starter is engaged during flight (engine in-flight restart). (d) ENG page ground format displays torque, TGT, Np, Nr, Ng, oil pressure, primary, utility, and accumulator hydraulic systems pressures, and starter indications (start status window).

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(2) ENG Page “In-flight” Format (a) An autopage will occur from ENG page ground format to in-flight format when both power levers are advanced to FLY. (b) The upper half of the ENG page in-flight format displays the same indications as ground format. (c) The lower half of the page will list active warnings in RED, and cautions in YELLOW as they occur in two text fields, in order of priority. However, the warnings will not display in this format until the ENG page emergency format has been acknowledged. (d) Additionally, the engine oil pressure and hydraulic systems status windows will be displayed in the upper right area of the in-flight page when: 1. Oil Pressure When oil pressure is less than 23 psi or greater than 120 psi. 2. Hydraulic Systems Pressure When hydraulic pressure is less than 1260 psi or greater than 3300 psi for more than 5 minutes or greater than 3400 psi for more than 5 seconds. NOTE: Display of the HYD PSI status window takes priority over the ENGINE OIL PSI status window on the ENG page in-flight format.

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NOTE: Engine oil pressure and hydraulic systems pressure indications can always be selected and viewed from the ENG Systems (SYS) page. Oil pressure from the ENGINE status window, and hydraulic pressure from HYD PSI status window.

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(3) ENG Page “Emergency” Format (a) The ENG page emergency format is autopaged in response to all aircraft warnings. (b) The upper half of the ENG page emergency format displays the same indications as the ground and in-flight formats. (c) The lower half of the page will display a window containing the immediate action steps associated with the active warning conditions. This text, displayed in WHITE, is provided to allow the crew to rapidly verify procedures once immediate corrective action has been taken. (d) The ENG page emergency format will revert to in-flight format when the crew member has selected the acknowledge button (B4, ACK). (e) CPG can turn –off autopaging by selecting DMS UTIL Page.

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(4) ENG ETF Page (a) Select the ETF page from the ENG page, it will display the current ETF for each engine and the Aircraft Torque Factor (ATF). The displayed values must be verified with the current aircraft logbook values (logbook values take precedence). This is normally part of a Data Management Systems (DMS) configuration check. (b) Selecting ETF1 or ETF2 pushbuttons and entering the new value via the Keyboard Unit (KU) may change the ETF value. This is normally accomplished by maintenance after an engine topping check is performed and the ETF is manually calculated. However, it may be required if the values from the ETF page do not match the logbook entries. NOTE: The maximum power check (topping check) for determining ETF is a maintenance function and is performed by a maintenance test pilot. The last topping check for ENG1 and ENG2 may be checked from ENG ETF page by selecting ENG1 or ENG2 for data, and then selecting LAST. The TGT value displayed in topping check window is the value that the engine selected will limit (limiter setting). NOTE: The use of the TEST button is for Maintenance Test Pilots only.

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ENG ETF LAST Topping Check Page

Count-Down Timers

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(5) Count-Down Timers (a) Count-down timers are displayed in place of engine numbers at the base of the vertical tape parameters for torque and TGT and under Ng indications when time limited engine operations are entered. Timers will alert crewmembers of time remaining before exceeding a limitation. (b) Count-Down timers are displayed in WHITE on the MPD ENG page in all formats. (c) Timers when displayed, decrement based on parameters listed in TM 1-1520-251-10 for engine type installed (-701 or –701C). (d) When a timer decrements completely, it displays 0:0 until reset by making the appropriate control input to exit the time limited parameter. (e) Multiple timer operations are available for up to four timers simultaneously. This process can involve up to four timers when exceeding –701C engine TGT limitations. (f) Additionally, engine TGT values are displayed on the FLT page and the HMD symbology below torque indication value based on parameters listed in TM 1-1520-251-10 for engine type installed (-701 or –701C). NOTE: During multiple timer operations, the highest timer number (1-4) value will be displayed. Earlier timers will continue to run. As power is reduced, each preceding timer value will be displayed, and each timer will be reset, automatically, in order. (6) Display Parameters Operation of these systems are indicated by color digital readouts and/or vertical tapes with operational limit markings. (a) Digital readouts 1. Color-coded according to normal (green), cautionary (yellow), and minimum/maximum (red) operating ranges of the monitored parameter. 2. Used to identify parameter limitations, as they are more accurate and provide fine resolution. (b) Parameters displayed with vertical tape incorporate color coding and shape coding (tape width) to delineate the normal, caution, and maximum operating ranges. Tapes are displayed in three different widths and colors based on operating conditions. 1. Narrow/green: Safe or normal range of operation 2. Medium/yellow: Range where special attention should be given to operation. 3. Wide/red: The limit above or below green or yellow ranges where continued operation is likely to cause damage or shorten component life.

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NOTE: Refer to TM 1-1520-251-10, Chapter 2 and 5 for engine parameters. Check on Learning: 1. The MPD ENG page displays what three formats?

_________________________________________________________________________ 2. What two status windows(only one at a time) may appear in the upper right of the in-flight format, when their associated systems are outside normal operating ranges? ________________________________________________________________________ 3. Which status window of the two has priority when both systems are out of limits? ________________________________________________________________________ 4. When the ENG page autopages to emergency format in response to an active warning, how do you revert back to in-flight format? ________________________________________________________________________ 5. What engine parameters utilize the count-down timer feature? ________________________________________________________________________

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G. ENABLING LEARNING OBJECTIVE (ELO) #7: ACTION: Identify Engine Health Indicator Test (HIT) procedures. CONDITION: Select from a list, without the use of notes or references. STANDARD: IAW TM 1-1520-251-10. a. Engine Health Indicator Test (HIT) (1) Engine strength or health is determined by the performance of the maximum power check. Performed by a maintenance test pilot, this test collects engine data at specific operating parameters to develop the Engine Torque Factor (ETF) for each engine. This is a measurement of the efficiency of the engine as compared to an optimum (100%) efficient engine. (2) As an engine operates, it ingests Foreign Object Debris (FOD), reducing the engine efficiency by coating internal surfaces with dirt/grime or by eroding/damaging compressor blades. As the engine efficiency degrades, it must run hotter to produce the same torque. (3) This degradation is checked before the first flight of the day by the performing The engine Health Indicator Test (HIT) check. In this check, the engine is operated at a given set of parameters and TGT is recorded and compared to the baseline TGT. If the aircraft HIT TGT exceeds the published HIT TGT limits, it is an indication that the engine performance has degraded to a point where cleaning and/or mechanical repairs must be performed. (4) If cleaning and mechanical repairs do not enable the engine to pass the HIT check, a maximum power check is then performed to determine the engine health. If still within power limits, a new baseline TGT for the HIT check is established, and the engine is returned to service. If out of limits, the engine is replaced. NOTE: Show slides #124 and 125. b. Health Indicator Test Procedures (1) AUTO HIT Check Procedures (a) Performance of the HIT check can be accomplished by the use of two different methods, AUTO or Manual HIT Check. Both methods will be discussed. NOTE: The use of TM 1-1520-251-10/CL should be used to perform HIT check. (b) HIT check may be performed at anytime prior to the first flight of the day, however, it is outlined in the Before Taxi Check. (c) To begin HIT, the helicopter is positioned into the prevailing wind. NOTE: If the ECS is in the heating mode, select A/C UTIL page and deselect BLEED AIR 1 and 2.

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(d) Set engine ANTI-ICE to OFF, on the A/C UTIL Page. (e) POWER levers – Set to FLY verify Np/Nr is 101%. (f) Retard POWER lever on engine not being checked to IDLE. (g) Increase collective pitch to 60% TORQUE and hold for at least 30 seconds. NOTE: If conducting AUTO HIT check perform the following: (h) A/C PERF page – Select HIT. NOTE: BASELINE reference numbers should be verified prior to selecting ENG 1 or ENG 2 buttons, for AUTO HIT calculation. The BASELINE values are used by the SP to determine if the engines will PASS/FAIL the HIT check. BASELINE values from the aircraft logbook take precedence. (i) ENG 1 button – Select. Check TORQUE 60%, Np/Nr RPM 101% and TGT stabilized. (j) CALCULATE HIT button – Select. (k) MPD – Note PASS/FAIL. (l) Aircraft HIT log – Record as necessary. NOTE: REF TGT from BASELINE Page is Table TGT on the HIT log sheet in the helicopter logbook. (m) A/C UTIL Page –Select. (o) ANTI-ICE INLET – ON. Note TGT increase of at least 50ºC. (p) ANTI-ICE INLET – OFF. Note TGT decreases to approximately initial value. (q) POWER lever, non-test engine – FLY. Verify torque matching. (r) Repeat step 8 through 16 for ENG 2. (2) Manual HIT Check procedures: NOTE: When using TGT reference table, FAT must be rounded up and pressure altitude must be rounded off to the nearest value.

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(a) To begin HIT, the helicopter is positioned into the prevailing wind. NOTE: If the ECS is in the heating mode, select A/C UTIL page and deselect BLEED AIR 1 and 2. (b) Set engine ANTI-ICE to OFF, on the A/C UTIL Page. (c) POWER levers – Set to FLY verify Np/Nr is 101%. (d) Retard POWER lever on engine not being checked to IDLE. (e) Increase collective pitch to 60% TORQUE and hold for at least 30 seconds. 1. Record date, A/C hours, FAT pressure altitude, TGT on HIT log sheet in helicopter logbook. Manually calculate and record HIT check TGT margin. (f) A/C UTIL page – Select. (g) ANTI-ICE INLET – ON. Note TGT increase of at least 50ºC. (h) ANTI-ICE INLET – OFF. Note TGT decreases to approximately initial value. (i) POWER lever, non-test engine – FLY. Verify torque matching.

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(j) If TGT margin is within acceptance limits engine performance is satisfactory. If margin is 5ºC or less from the limit, make appropriate entry in remarks section of DA form 2408-13-1. (k) Repeat step d through j for the other engine. 1. If TGT margin is out of limits, repeat check. Ensure that all procedures are followed. 2. If TGT margin is still out of limits, do not fly the helicopter. Make appropriate entry in remarks section of DA form 2408-13-1. Check on Learning: 1. What are the two types of HIT checks that can be performed?

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2. How can you prevent the ECS from automatically activating the heating mode? _________________________________________________________________________ 3. If checking BASELINE page and values are different from those annotated on the HIT Log , what should be done? _________________________________________________________________________ 4. When TGT margin is within _______ degrees or less of the table TGT limit, a write up on the DA Form 2408-13 required? _________________________________________________________________________ 5. When the TGT values are getting closer to the established limits what does indicate? _________________________________________________________________________

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