Basic Systems II

Question 1

APU

Answer 1

Auxiliary Power Unit

Question 2

Define the purpose of the APU

Answer 2

(Allied Signal/Garret) self-contained, fully automatic, constant speed, gas turbine, requiring only DC power (BATT), fuel (aft cell), and input signals (HYD 2600 psi) from the helicopter for operation.

Question 3

What section does the APU drive?

Answer 3

The accessory section of the main transmission (XMSN), which indirectly gives you electrical power, and hydraulic pressure.

Question 4

How many pounds of fuel per hour does the APU burn?

Answer 4

175 pounds/hour

Question 5

Where does the APU directly supply air?

Answer 5

To the engine and Integrated Pressurized Air System (IPAS).

Question 6

APU Specifications

Answer 6

*See chart

Question 7

Where is the APU located?

Answer 7

Inboard of the right engine nacelle aft of the main XMSN in the catwalk under a kevlar cover.

Question 8

What panel is the APU accessed?

Answer 8

Through panel L325, then catwalk doors.

Question 9

What is the purpose of the APU enclosure?

Answer 9

Confines the APU in the event of a fire for extinguishing purpose.

Question 10

What does the enclosure inlet screen allow?

Answer 10

Ambient air for cooling

Question 11

What does the air inlet screen allow?

Answer 11

Ambient air to be used for combustion.

Question 12

What is the APU exhaust duct attached to do?

Answer 12

Expel hot gasses.

Question 13

What are the APU power section components?

Answer 13

Two makor sections:
Power Section
Accessory Section

Question 14

What does the APU Power section provide?

Answer 14

81 Shaft Horespower (SHP) to drive the accessory section and the main XMSN accessory section via #7 driveshaft.

Load Control Valve (LCV) mounts to the power section.

Question 15

What is the purpose of the Load Control Valve?

Answer 15

Controls and orutes APU bleed air to IPAS manifold.

Question 16

During APU start, what position is the LCV in?

Answer 16

The LCV is closed during APU start.

Question 17

When and how is the LCV opened?

Answer 17

By electronic control unit at 95% speed.

Question 18

When does the LCV close?

Answer 18

Closes at APU shutdown <95% or when APU FIRE/READY switch is activated.

Question 19

What does the APU Accessory section provide?

Answer 19

The means for starting. Converts turbine wheel speed (56,566) to Power Takeoff (PTO) clutched speed (8216).

Question 21

Increases the low voltage input signal from the ECU into a high voltage output for the APU’s igniters.

Answer 21

Igniter Unit

Question 22

Solenoid activated at less than 75 psi, and sends a signal to the ECU for APU operation.

Answer 22

Low Oil Pressure Switch

Question 23

Vents excess pressure from the APU accessory gearbox.

Answer 23

Vent Port

Question 24

Removes contaminates from the APU oil system. No bypass capabilities.

Answer 24

Oil Filter

Question 25

Provides pressurized oil for lubricating the main bearings, gear meshes, and gear shafts. It also supplies oil for the activation of the PTO clutch.

Answer 25

Oil Pump (Internal)

Question 26

Provides a container for the lubricating oil.

Answer 26

Integral Oil Sump

Question 27

Mounted on right side of the APU and can be viewed through an access port on the bottom of the number 2 engine nacelle.

Answer 27

Oil Sight Gauge *Oil quantity check is required on pre-flight and the oil level should be midway on the sight gauge.

Question 28

Where is the oil sight gauge location?

Answer 28

Panel RN5 under number 2 engine. *Ball bearing is in the center of the sight gauge for proper servicing of oil half full.

Question 29

Allows for draining of the oil sump and to check for metal particles in the oil.

Answer 29

Magnetic Chip/Drain *Chip detector is a maintenance visual inspection only.

Question 30

Receives pressurized fuel from the aircraft aft fuel cell via anelectric fuel boost pump, which is automatically energized when the APU start button is pressed.

Answer 30

Fuel Control Unit *Boost pump is located on the upper right aft fuselage panel in the ammunition bay.

Question 31

Allows pressure to build to build up before being released to the APU fuel nozzles and provides for shutdown of the APU when the APU on button in the crew station is pressed.

Answer 31

Fuel Control Shutoff Valve

Question 32

Provides pressured fuel to APU, located in the ammo bay. Fuel is supplied to the APU from the Aft fuel cell.

Answer 32

Fuel Boost Pump 24-28 * Vdc electrically driven pump

Question 33

Removes contaminates from the APU fuel

Answer 33

Fuel Filter

Question 34

Sends speed information from the APU to the ECU.

Answer 34

Speed Sensor Monopole

Question 35

Requires 2600-3000 psi hydraulic pressure from the utility hydraulic pressure from the accumulator for APU start

Answer 35

Hydraulic Start Motor Utility hydraulic pressure check is required on pre-flight

Question 36

Provides coupling and de-coupling from the XMSN via the number 7 driveshaft.

Answer 36

Power Takeoff (PTO) Clutch *Electronically controlled/hydraulic actuated by the Torque Limiting Control Valve (solenoid valve)

Question 37

When does the PTO clutch engage?

Answer 37

Normal engagement is 60% at 95% NR. Cold weather 95%.

Question 38

Provides operational sequencing control for: Automatic Start, Normal Operation, PTO Clutch Operation, APU Protection, and Continuous Monitoring and managing of APU system.

Answer 38

Electronic Control Unit (ECU)

Question 39

What provides main rotor speed (NR) to the ECU?

Answer 39

ECU - Monitors Main Rotor RPM

Question 40

When will the the APU ON illuminate?

Answer 40

When Ng reaches 95%.

Question 41

When will the ECU initiate automatic shutdown for overspeed or a loss of signal from the speed monopole sensor?

Answer 41

108%

Question 42

What monitors oil pressure and sends a signal to the ECU?

Answer 42

Low Oil Pressure Switch * Oil Pressure below 75 psi *If oil psi is not above 75 psi at 95% APU Ng for 10 seconds

Question 43

While monitoring exhaust gas temperatures, what causes ECU auto shut down?

Answer 43

-Loss of temp signal from thermocouple -1785+/-25 degrees F at 60% APU speed - 1340 +/- 25 degrees F at 100% APU speed

Question 44

What output signals does the ECU provide to control?

Answer 44

Ignition Unit Fuel Control Load Control Valve Solenoid APU Operational Status to MP Fuel Shutoff Valve Hydraulic Start Solenoid Valve PTO Clutch Solenoid Valve

Question 45

What does the APU control switch?

Answer 45

-Provides the means to start and stop APU -Located on the pilot's power lever quadrant -Momentary action switch, NVS green ON lable

Question 46

APU start/shutdown minimum requirements?

Answer 46

-Battery or external power -Min 2600 psi HYD accumulator -Fuel in Aft cell -Oil level check

Question 47

What are the APU start up sequences?

Answer 47

APU has begun auto start sequence - APU ECU has power, 95% APU speed -Aircraft is on the ground APU speed 95%. Load control valve open, providing pressurized air to IPAS.

Question 48

Should the APU (or AGPU) be ON or OFF prior to moving the power levers?

Answer 48

APU (AGPU) should be ON.

Question 49

What one warning is associated with the APU?

Answer 49

APU Fire Warning

Question 50

What one caution is associated with the APU?

Answer 50

If the APU is ON and the aircraft is in the air.

Question 51

What advisory messages are associated with the APU?

Answer 51

Overtemp Overcurrent Low Oil Pressure Oil Sw Overspeed ECU Stop

Question 52

What is the IPAS compromised of?

Answer 52

A series of manifolds, ducts, valves, tubing, regulators, actuators, and two main engine starters.

Question 53

Pneumatic power for the IPAS is generated by what?

Answer 53

Engine bleed air, APU, or AGPU air.

Question 54

Limits the flow of bleed air to 6.5% of the total engine compressor core flow in the event of an IPAS leak.

Answer 54

Low Pressure Venturi

Question 55

Where is the low pressure venturi mounted?

Answer 55

Directly on the engines at the low-pressure bleed air port (compressor).

Question 56

Where does the low pressure venturi connect?

Answer 56

To the IPAS ducting leading to the engine bleed air Pressure Regulator Shutoff Valve (PRSOV).

Question 57

Primary source of bleed air?

Answer 57

ENG #1 and ENG #2

Question 58

What is the secondary source of bleed air?

Answer 58

Single Engine

Question 59

When on the ground, primary source is?

Answer 59

APU (or AGPU)

Question 60

If bleed air is turned off, everything loses bleed air except?

Answer 60

Hydraulics

Question 61

What interconnects the PRSOVS to ensure both engines are supplying an equal amount of bleed air?

Answer 61

Flow Share Sense Lines

Question 62

What prevents backflow of fifth stage/ pressurized air?

Answer 62

Engine/APU Bleed Air Check Valve

Question 63

Receives and distributes IPAS air from APU, ENG to components.

Answer 63

Primary Manifold/Low Pressure Manifold

Question 64

Receives air in the 450F to 500F (232C to 258C) temperatures and limits them to 450F.

Answer 64

Bleed Air Precooler

Question 65

What W/C/A's are associated with IPAS?

Answer 65

No warnings or cautions. Only four Advisories.

Question 66

Uses IPAS air for heating the crew stations and the Air Particle Serparator.

Answer 66

ECS

Question 67

Converts pneumatic energy to shaft power for starting or motoring the main engines.

Answer 67

Air Turbine Starter (ATS)

Question 68

At what percentage does air to ATS shut off, and ignition is terminated?

Answer 68

52%

Question 69

Regulates the IPAS pressure for the fuel boost pump, fuel transfer pump valve to 19 +/- 3.

Answer 69

Fuel System Pressure Regulator

Question 70

Provides reliable feed from the aircraft fuel tank to the Engine.

Answer 70

Fuel Boost Pump

Question 71

Pneumatically driven pump that allows transfer of fuel between the forward and aft fuel cells.

Answer 71

Fuel Transfer Pump

Question 72

Uses IPAS air to create a low-pressure area aft of the probe (100 KTAS) for optimum detection of ice.

Answer 72

Ice Detector Probe

Question 73

Designed to remove the oxygen in the fuel cells to a level enough to inhibit combustion.

Answer 73

Nitrogen Intering Unit (NIU)

Question 74

IPAS air supplies actuator pressure to close louvers if activated by the fire extinguishing panel.

Answer 74

Louver Actuator

Question 75

Prevents or removes moisture (fogging) on inside canopy side panels of both crewstations.

Answer 75

Canopy Defog

Question 76

Primary and utility hydraulic reservoir pressure regulator are reducing high pressure bleed air to 31 +/- 3.

Answer 76

Primary and utility hydraulic reservoir pressure regulators

Question 77

Max pressure going to hydraulics is?

Answer 77

55 +/- PSI

Question 78

Primary fuels

Answer 78

JP-4, JP-5, JP-8

Question 79

What is the purpose of the fuel breakaway valves?

Answer 79

Reduce fire hazards by sealing the cells and lines during a high-impact landing.

Question 80

What is maximum useable capacity of internal auxiliary fuel tank?

Answer 80

100 Gals

Question 81

What is the indication that the NIU has failed?

Answer 81

The indicator on the NIU test panel has three white triangles

Question 82

Fuel Transfer Messages

Answer 82

FWD or AFT Fuel shutoff valve fail, transfer pump fail