APU Flashcards by Matthew Fust

The start accumulator.

(1) Located at STA 555 on the right side of the ramp compartment.

(2) Stores hydraulic fluid under pressure for use in APU start.

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The APU start module.

(1) Located aft and to the right of the APU start accumulator.

(2) Provides signal pressure for the APU motor pump.

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The manual fuel shutoff valve.

(1) Located inside the aft cabin, left side, at STA 540.

(2) It provides an alternate means of shutting off fuel to the APU.

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The manual fuel shutoff valve.

(1) Located inside the aft cabin, left side, at STA 540.

(2) It provides an alternate means of shutting off fuel to the APU.

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The ESU/DESU. An APU Electronic Sequencing Unit (ESU) or Digital Electronic Sequencing Unit (DESU)

(1) Located on the L/H side of the ramp area.

(2) Monitors the APU during start and shut down.

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The APU fuel boost pump.

(1) Located in the left aft intertank area.

(2) It boosts fuel pressure during APU start.

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The APU fuel boost pump.

(1) Located in the left aft intertank area.

(2) It boosts fuel pressure during APU start.

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The APU fuel solenoid valve.

(1) Located in the left aft intertank area.

(2) Stops fuel flow to the APU.

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APU Hydraulic Motor Pump

(a) Motors the APU during start

(b) Provides utility hydraulic pressure to the system.

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APU Hydraulic Motor Pump

(a) Motors the APU during start

(b) Provides utility hydraulic pressure to the system.

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APU Accessory Drive

Provides a mounting pad for the Generator, Motor Pump and the Fuel Control Unit.

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APU Fuel Control

Controls fuel flow to the APU.

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APU Fuel Control

Controls fuel flow to the APU.

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APU Power Turbine Assembly

Provides the power to drive the APU accessories.

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APU AC Generator (20 KVA)

Provides electrical power for ground operation.

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APU AC Generator (20 KVA)

Provides electrical power for ground operation.

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APU Oil Reservoir

Stores Oil for the APU.

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APU Oil Reservoir

Stores Oil for the APU.

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APU

(1) Provides hydraulic and electrical power for:

APU

(1) Provides hydraulic and electrical power for:

(a) Engine starts

(b) Ground maintenance

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Listed below is some general information about the APU

(1) Model: T62−T−2B

(2) Manufacturer: Turbomach (a division of Hamilton Sundstrand Power Systems)

(3) Dimensions:

(a) Weight (including residual fluids) − 74.8 Lbs

(b) Length − 33 inches

(d) Height − 24 inches

(4) Normal rated: 66 Shaft Horse Power (SHP) with a maximum rated 95 SHP

(5) Operates on: JP−8, JP−5, JP−4 fuels

(6) Fuel consumption: 89 Pounds Per Hour (PPH) at the normal rated power with a maximum consumption of 115 PPH, from the left main tank

(7) Single Stage Centrifugal Compressor and Power Turbine

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APU

(1) Drives a motor/pump to pressurize the utility hydraulic system for main engine starting and ground checks

(2) Drives the APU generator to supply power to the electrical system

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The air inlet section:

The air inlet section

(1) Provides the intake of ambient air to the compressor.

(2) The air inlet opening is covered by a wire mesh screen to protect against FOD ingestion.

(3) During operation air is drawn in by the compressor rotor.

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The compressor portion of the turbine assembly is:

The compressor portion of the turbine assembly is a single stage centrifugal-flow (impeller) type compressor rotor.

(1) Air drawn in through the inlet is compressed by the centrifugal impeller.

(2) The compressed air exits the impeller, it enters a diffuser, which changes the direction of the airflow and sends it to the combustor.

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The combustor assembly housing

(1) Holds the liner and its inner wall forms a circular exhaust duct.

(2) Receives air from the compressor diffuser and a portion of the air supplied is mixed with fuel and used in the combustion process (expanded).

(3) Air that is not used in the combustion process is used as cooling air.

(4) The combustor housing has threaded bosses for installation of a spark plug, start fuel nozzle, and fuel manifold.

(5) It directs the combusted (expanded) gasses through the turbine nozzle and onto the power turbine rotor.

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Reduction and Accessory Drive Assembly Equipped with three mounting pads to drive accessories (a)Axial pad drives the hydraulic motor/pump (b)Right angle pad drives the 20 KVA generator (c)Accessory pad drives the APU fuel control assembly

The APU start accumulator pressure is used to operate the utility hydraulic subsystems during an emergency or while on the ground with the APU off. (1) APU Start Accumulator (a) 30 inches long (b) Weighs 28 pounds (c) Capacity is 375 cubic inches of hydraulic fluid (d) Has an attached pressure indication gauge (2) The pressure is checked on preflight (3,000 psi).

APU Start Module (1) Controls the mode of operations of the APU motor/pump by applying or removing the signal pressure to the motor/pump compensator (2) Contains a manual depressurization valve, which is used to depressurize the APU start accumulator and the reservoir pressurization accumulator to facilitate maintenance on the utility system The valve is located on the bottom center of the module. (3) The pressure indicator should indicate system pressure in the APU start accumulator.

APU motor/pump provides 3350 psi of hydraulic pressure to start the main engines.

Airframe mounted APU fuel boost pump. (1) Located in the aft left intertank area at STA 444 (2) Supplies fuel at 5-40 PSI to the APU driven fuel pump (3) Operates on 24/28 Volts Direct Current (Vdc) off the hot battery bus, or the essential bus depending on the position of the battery switch (4) Energized when the APU start switch is placed to the “RUN” position

APU fuel solenoid valve (1) Mounted on the boost pump (2) Stops the flow of fuel to the APU during an ESU/DESU shutdown of the APU (3) Energized open when the APU start switch is placed to the “RUN” position

APU fuel pump is mounted to and driven by the accessory drive pad.

Acceleration control assembly controls the maximum operating speed of the APU. (1) Normal rated speed of the APU is 58,225 RPM. (2) Maximum allowable speed of the APU is 65,794 RPM.

Main metering valve has automatic altitude compensation up to 15,000 feet.

Manual shutoff valve (1) Has an airframe access panel for operation while outside the aircraft. (2) Can be used to shut down the APU during an emergency when performing maintenance without direct access to the APU switch on the overhead panel

The BATT switch is a two position switch. (1) The “ON' position provides normal starting of the APU using the 24/28 Vdc essential bus. (2) The “OFF” position provides emergency starting of the APU using the 24/28 Vdc battery bus. q. APU Switch (1) A three position switch that connects DC power to the APU system (2) “RUN” position sends 28 VDC to the ESU/DESU to provide power and to reset the BITE indicators. (3) Also sends 28 VDC through the fault relay to electrically open the fuel solenoid valve, energizing the airframe mounted fuel boost pump providing fuel pressure to the APU. (4) The “START” position connects 28 Vdc to the ESU/DESU which controls the APU Start. (5) The “OFF” position removes power from the ESU/DESU, shutting down the APU.

ESU/DESU (1) Sequences the start procedure of the APU (2) Continuously monitors the APU operation (3) After releasing the APU start switch, the ESU/DESU automatically sequences the steps for a successful start of the APU. (4) During operation, the ESU/DESU runs a check on itself and the APU. (5) The box has a decal that lists possible faults for the codes displayed by the fault indicators. (6) The ESU/DESU contains Built-In Test Equipment (BITE) indicators. (7) There are 4 (ESU) or 5 (DESU), magnetically latched fault indicators. (8) Should the ESU/DESU shutdown the APU, BITE indicators will display the cause of the shutdown. (9) An adapter plug is provided to connect the ESU/DESU to the CH-47 aircraft wiring system.

Event/time meter provides accurate tracking of APU starts for the purpose of maintenance and inspections.

Oil sump. (1) Mounted on the lower portion of the reduction drive (2) Held in position by a clamp and sealed with a packing (3) Bowl type with a three quart capacity (4) Has an oil level sight gage that faces the No. 1 side of the aircraft. (5) The fill cap is used as a dipstick to check oil level, and contains a screen to prevent contamination when servicing the sump. (6) Oil pressure for the APU is maintained between 15-40 PSI by a pressure relief valve located in the main oil gallery.

Oil pressure switch (1) Mounted on the accessory drive housing (2) Monitors oil pressure (3) Sends a signal to the ESU/DESU

APU – Start as follows: NOTE: (1) UTIL PRES light — On.

APU – Start as follows: NOTE: (1) UTIL PRES light — On. Caution: (2) APU switch — RUN for _ to __ seconds. (3) APU switch — START for _ seconds, then RUN. (4) APU RDY light — Check on. (5) UTIL PRES light — Check out. If the light does not go out within 30 seconds after the APU RDY light illuminates, APU switch OFF.

APU – Start as follows: NOTE: If the start is not completed or the APU is automatically shut down, do not turn the BATT switch OFF. Set the APU switch to OFF, check the BITE indicators on the ESU, and record the display for maintenance. Then turn the BATT switch OFF. Wait one minute for cooling before attempting a restart. Failure to allow the APU to cool may cause a premature shutdown on restart due to over temperature. (1) UTIL PRES light — On. CAUTION: If a start results in a roar with flame in the exhaust (hot or torching start), shut down the APU by setting the APU switch to OFF. (2) APU switch — RUN for 6 to 10 seconds. (3) APU switch — START for 2 seconds, then RUN. (4) APU RDY light — Check on. (5) UTIL PRES light — Check out. If the light does not go out within 30 seconds after the APU RDY light illuminates, APU switch OFF.

APU operation (1) APU start is automatic and controlled by the ________. (2) The ESU/DESU monitors _____ and ________ gas temperature on the APU. (3) The ESU/DESU will _____ ______ the APU when a limit is exceeded. (4) The ___ ___ indicating light is a press-to-test light that is activated by the ESU/DESU. Illuminates when the APU is __ __ _____ and Exhaust Gas Temperature (EGT) is ____. (5) UTIL PRES indicating light is a press-to-test light. UTIL PRES will extinguish when the _______ _______ ______ _____ is within normal operating range. (1) During APU start or operation, the DESU/ESU monitors the APU start sequence and operation. (2) The APU start solenoid valve is activated by the Electronic Sequencing Unit (ESU) when the APU start switch is placed in the start position. (3) The solenoid valve is controlled by the ESU during the APU start to remove fluid pressure from the APU motor pump when the APU reaches 90% N1.

APU operation (1) APU start is automatic and controlled by the ESU/DESU. (2) The ESU/DESU monitors speed and exhaust gas temperature on the APU. (3) The ESU/DESU will shut down the APU when a limit is exceeded. (4) The APU RDY indicating light is a press-to-test light that is activated by the ESU/DESU. Illuminates when the APU is up to speed and Exhaust Gas Temperature (EGT) is normal (5) UTIL PRES indicating light is a press-to-test light. UTIL PRES will extinguish when the utility hydraulic system pressure is within normal operating range. (1) During APU start or operation, the DESU/ESU monitors the APU start sequence and operation. (2) The APU start solenoid valve is activated by the Electronic Sequencing Unit (ESU) when the APU start switch is placed in the start position. (3) The solenoid valve is controlled by the ESU during the APU start to remove fluid pressure from the APU motor pump when the APU reaches 90% N1

What is the primary purpose of the CH-47F Auxiliary Power Unit (APU)?

To provide power for ground operations and in-flight emergencies ## Footnote The APU is used for starting engines and supplying electrical and hydraulic power.

What are the components of the CH-47F APU?

The components include: * Engine * Fuel Control * AC Generator * Accessory Drive * APU Motor/Pump ## Footnote Each component plays a crucial role in the operation of the APU.

What are the four sections of the APU Engine Assembly?

The sections are: * Intake * Compressor * Combustor * Exhaust ## Footnote These sections work together to facilitate the combustion process and power generation.

Fill in the blank: The APU fuel burn rate is approximately ______ PPH from the left main tank.

90 ## Footnote This rate indicates the efficiency and consumption of fuel during APU operation.

What must be checked during the pre-flight procedures for the APU?

Pre-flight checks include: * APU Oil Level * APU Start Accumulator * APU Start Module * Digital Electronic Sequence Unit (DESU) * Manual Shutoff Valve * APU Exhaust Duct ## Footnote These checks ensure the APU is ready for operation and safe to use.

True or False: The APU can be operated in-flight at any time.

False ## Footnote The APU is intended for ground operation only, except during emergencies.

What does the Digital Electronic Sequence Unit (DESU) do?

The DESU controls and monitors the APU operation ## Footnote It sequences the start procedure and checks operational parameters.

What should the APU Start Accumulator read during pre-flight?

3000 PSI ## Footnote This ensures the accumulator is charged and ready for starting the APU.

List the immediate actions to take in the event of an APU fire.

Immediate actions include: * Turn APU switch OFF ## Footnote This action is critical to prevent further damage and ensure safety.

What is the function of the APU Motor/Pump?

Provides RPM to start the APU and hydraulic pressure for ground operations ## Footnote It is essential for initiating the APU and maintaining hydraulic pressure.

What should be done if the UTIL PRES light does not go out within 30 seconds after the APU RDY light comes on?

Turn off the APU (APU Switch OFF) ## Footnote This indicates a potential issue with the APU that needs to be addressed.

How long should the APU switch be in the RUN position before moving to START?

5 seconds ## Footnote This delay helps to ensure the APU is properly primed for starting.

What are the operational restrictions on the APU?

Restrictions include: * Ground operation only * No starting with a tail wind over 25 knots * Prohibited in-flight operation except during emergencies ## Footnote These restrictions are in place for safety and operational integrity.

What is the purpose of the APU Fuel Control?

Manages fuel to maintain the APU at 100% speed ## Footnote This component is vital for ensuring optimal performance of the APU.

What does the APU Generator provide?

Provides AC power to the aircraft for ground operations and in-flight emergencies ## Footnote It is crucial for electrical support while the APU is running.

What should be done if the APU failed to start or shut down?

Check the BITE indicators on the DESU and record the display for maintenance ## Footnote This helps in diagnosing the issue and ensuring proper maintenance procedures are followed.

Fill in the blank: The APU is not a ______ type turbine.

free-air ## Footnote This distinguishes it from other turbine engines where sections can rotate independently.

What action should be taken after an APU restart attempt?

Wait 1 minute for cooling before attempting a restart ## Footnote This helps prevent overheating and potential damage to the APU.