Powerplant and related

Question 1

Name of the engine

Answer 1

T700-GE-401C

Question 2

Type of engine

Answer 2

Front-drive turboshaft

Question 3

The waterwash manifold is an integral part of the _____, which aims a series of jets into_______.

Answer 3

swirl frame, compressor inlet area

Question 4

After passing through the _____, airflow passes through the ________ which impart rotation to the airflow.

Answer 4

inlet cowling, swirl vanes

Question 5

The swirl vanes are ______, to allow passage of fifth stage bleed air via the _____ for anti-icing purposes.

Answer 5

hollow, engine anti-ice valve

Question 6

The _____ prevents foreign particles from entering the compressor. The rotation of the airflow, imparted by the swirl vanes, causes the particles to be thrown outward into _______.

Answer 6

inlet particle separator (IPS), the collection scroll

Question 7

Before discharge airflow is dumped overboard through the _______, it passes over the ______, which are contained in the collection scroll.

Answer 7

blower assembly, swirl vanes

Question 8

After passing through the IPS, clean air passes through the _____, which remove the rotation, providing smooth airflow to the ______.

Answer 8

deswirl vanes, compressor

Question 9

The compressor section consists of_______

Answer 9

five-stage axial and single-stage centrifugal rotor/ stator assembly

Question 10

The combustion section consists of________

Answer 10

flow-through, annular combustion chamber
two igniters
12 fuel injectors (receive fuel via the ODV and supply atomized fuel for combustion)

Question 11

The Ng turbine drives the _____ and ______.

It is a _____________ design.

Answer 11

compressor and accessory gearbox (AGB),

two-stage, air cooled, high performance axial design

Question 12

The Np turbine has two stages that turn the ______

Answer 12

power turbine driveshaft

Question 13

The Np shaft is______, turning inside the _______.

It extends through the front of the engine where it connects to the _______, which in turn connects to the ______.

Answer 13

coaxial, inside the Ng turbine driveshaft

high speed shaft, input module

Question 14

TGT is sensed between___________.

Answer 14

gas-generator and power turbine

Question 15

Approximately _________ percent of total airflow through the engine is used for the combustion process. The remainder is used for:

Answer 15

30 percent for combustion

1. Compressor inlet temperature (T2) air
2. Compressor discharge pressure air (P3)
3. Combustor and turbine cooling
4. Engine oil seal pressurization

Question 16

The AGB is driven by _______

Answer 16

a rotor via the radial driveshaft from the Ng turbine driveshaft

Question 17

Purpose of the Engine Control System

Answer 17

to maintain a constant Np/Nr

Question 18

The HMU provides________, while the DECU ____________.

Answer 18

gas generator control, trims the HMU to satisfy the requirements of the power turbine load and reduce pilot workload.

Question 19

What happens in DECU lockout

Answer 19

The PCL is used to manually control Np/ Nr. TGT limiting, Np governing, and load sharing functions are deactivated. Np overspeed is retained via a direct link between the DECU and ODV.

Question 20

A _____ on the engine control quadrant activates a _____ to prevent the PCLs from being advanced above IDLE with the rotor brake on. If the rotor brake is relased, the ______ energizes and unlocks the PCLs. An _______ is provided on the quadrant, should the _____ fail.

Answer 20

solenoid, mechanical locking device
solenoid
override tab
solenoid

Question 21

The engine driven boost pump on the forward side of the AGB is designed to do 2 things….

Answer 21

1. Provide reliable suction feed from the tank to the engine, minimizing vulnerability and fire hazard in the event of damaged fuel lines
2. Provide discharge pressure to satisfy the minimum inlet pressure requirement of the HMU or high-pressure fuel pump

Question 22

Fuel leaves the high pressure pump, passes through the metering valve and shutoff valve and is then directed through an external line to the oil-to-fuel heat exchanger. Some fuel is tapped to operate various servos in the HMU for the following:

Answer 22

“Ms V’

1. Positioning the METERING valve to ensure proper fuel flow to the engine
2. Positioning a SERVO piston that actuates the variable geometry vane servo and start bleed valve.
3. Amplifying VARIOUS signals (T2, P3, Ng) that influence fuel flow and variable geometry servo position

Question 23

T2, P3 and Ng inputs aid the HMU in controlling _______ and ________ during engine start and normal operation, reducing the chance of compressor stall.

Answer 23

variable stator vanes and anti-ice/ start bleed valve position

Question 24

After fuel leaves the ______, it is routed to the ________, which schedules fuel flow commensurate to the current power demand and is trimmed to the required level by the _____ in response to DECU signals.

Answer 24

high-pressure fuel pump, metering valve, torque motor servo

Question 25

The HMU, via the _______, provides feedback to the DECU to null the torque motor servo input, stabilizing metering valve movement and preventing ________. Excess fuel is then routed back to______

Answer 25

LVDT, preventing engine oscillation/hunting, the pump inlet

Question 26

The Ng overspeed valve is set to trip at_____. A spring loaded ball valve ports fuel pressure causing the minimum pressure valve to secure flow to the engine.

Answer 26

110 plus or minus 2 percent

Question 27

The actual level of engine power in FLY is normally more than required by the helicopter. It's intentionally placed at a higher level for 2 reasons:

Answer 27

1. Fail safe to high power. There are enough engine protection functions within the HMU that neither engine damage nor stall can occur during or following loss of the electrical signal to the torque motor. All you need to do after a failure is retard the PCL manually to a more desirable level 2. Power available with OEI.

Question 28

The HMU provides:

Answer 28

1. Rapid engine transient response through collective compensation 2. Automatic fuel scheduling for engine start 3. Ng overspeed protection. Mechanically limits Ng to 110 plus or minus 2 4. Ng governing. HMU receives T2, P3, and Ng inputs from their respective sensors, which are used to schedule fuel for minimum flow, max flow, and VGV control 5. Accelerating limiting. Ng governor ensure any PCL motion will result in safe engine operation and not cause engine damage. Inadvertent shutdown will not occur. 6. Flameout and compressor stall protection. HMU adjusts variable geometry vane position and opens the anti-ice/ start bleed valve to prevent compressor instability.

Question 29

When the PCL is advanced to IDLE, the shutoff valve in the HMU opens and allows metered fuel to flow to the ODV, which has four main functions:

Answer 29

1. Provides main fuel flow to the 12 fuel injectors during engine start operation. 2. Purges the main fuel manifold overboard, after engine shutdown, through a shutoff and drain valve to prevent coking of the fuel injectors 3. Traps fuel upstream, which keeps the fuel/ oil heat exchanger full, so that system priming is not required prior to the next start. 4. Returns fuel back to the HMU if the Np overspeed is energized or if the DECU hot start preventer is activated.

Question 30

All essential engine electrical functions are provided by the _______. The engine alternator contains separate windings providing ___ power to the _____, ______, and ____ signal to the vertical instruments.

Answer 30

alternator, AC, ignitor assembly, EDECU, Ng

Question 31

Np Governing

Answer 31

The Np sensor located on the left side of the power turbine section provides an Np signal to the EDECU. Actual Np is compared to a reference Np to compute a speed error input signal for use in electrical control computation.

Question 32

Np Overspeed Protection

Answer 32

The Np overspeed system is composed of redundant circuits, which rely on a signal from the Np overspeed and torque sensor located on the right side of teh power turbine section. The overspeed system is actuated at 120% Np. WEhen Np exceeds 120%, a signal is sent from the EDECU to the ODV, diverting fuel to the inlet of the HMU, causing engine flameout. Warning: A popped No. 1 ENG OVSP or No. 2 ENG OVSP cb shall not be reset in flight. Resetting a popped No. 1 or No. 2 ENG OVSP cb may initiate an engine overspeed signal and result in engine failure.

Question 33

TGT Limiting

Answer 33

Measured TGT is compared to a fixed reference TGT. When the temperature is above the reference, a signal is generated to reduce fuel flow. When TGT approaches 878 C, the EDECU prevents any further increase in fuel flow to the engine. The EDECU incorporates a maximum rated power (MRP) limiter that limits TGT to 866 plus or minus 10 C. If power demand is increased further, Np/Nr will droop below 100%; Np governing will be sacrificed to protect the engine against overtemperature.

Question 34

Engine Load Sharing

Answer 34

Torque signals are compared between the two engines via the respective EDECUs. A torque error signal is generated if one engine torque is less than the other. The torque matching system operates by increasing power on the lower torque engine, while not directly affecting the higher torque engine.

Question 35

Engine Speed Trim

Answer 35

An ENG SPD TRIM switch, located on the upper console, with positions INCR and DECR, controls the Np of both engines simultaneously. There is no individual engine trim capability. The ENG SPD TRIM switch supplies a reference electrical signal to the EDECUs for controlling Np as required between 96 and 101% Np.

Question 36

Manual Contingency Power

Answer 36

The TGT limit can be increased by placing the CONTGCY PWR switch on the collective to the ON position. This sends a signal to the EDECU to allow TGT to increase to 903 °C; however, the maximum contingency range power (CRP) limiter will prevent further increase in fuel flow to the engine at 891 °C ±10 °C. The #1 and #2 ENG CONTGCY PWR ON advisories indicate that contingency power has been selected. Placing the CONTGCY PWR switch to the ON position automatically deactivates the environmental control system (ECS).

Question 37

Auto Contingency Power

Answer 37

In addition to existing manual contingency power, the EDECU also provides automatic contingency power, enabled in OEI conditions. When the torque from one engine is below 50% (180 ft-lb), the opposite engine EDECU will automatically reset the TGT limiter from 866 °C ±10 °C to a maximum limit of 891 °C ±10 °C. The #1 and #2 ENG CONTGCY PWR ON advisories will not illuminate to indicate that contingency power has been activated.

Question 38

Dual-Engine Auto-Contingency Power

Answer 38

Dual engine auto-contingency power allows the EDECU to bypass the 10-min TGT limit of 866 °C ±10 °C, and limit the aircraft at the contingency power TGT limit of 891 °C ±10 °C. For this feature to activate, one or more of the following conditions must exist: a. Np drops below 96%. b. Greater than 3% droop between reference power turbine speed (Np) and actual Np reference set point. c. Greater than 5% per second Np droop rate exists with Np less than or equal to Np reference set point.

Question 39

Np Overspeed Test

Answer 39

The test mode is activated by the ENG OVERSPEED TEST A and B buttons. When both switches are actuated, the Np overspeed limit is re-referenced to 96% Np. If power turbine speed decreases when either switch is pressed individually, the opposite test switch may be faulty

Question 40

EDECU Lockout

Answer 40

After being moved momentarily to LOCKOUT, the PCL is used to manually control Ng and Np. As a result, engine power is no longer controlled by the EDECU; it is set by PAS and LDS positions only. With the PCL in LOCKOUT, the torque motor servo is disabled, therefore deactivating TGT limiting, Np governing, and load sharing. The Np overspeed protection system is retained when in LOCKOUT. To regain automatic engine control, the PCL must be moved to IDLE then returned to FLY.

Question 41

Cockpit Signals

Answer 41

Provides Np, TGT, and torque signals to data concentrator (DTC) for cockpit display.

Question 42

Hot Start Prevention

Answer 42

Detects a hot start when TGT exceeds 900 °C with Ng below 60% and Np below 50% and automatically stops fuel flow by tripping the ODV. Fuel flow is restored when TGT either decreases to 300 °C or after 25 seconds, whichever occurs first. Hot start prevention can be disabled by pressing and holding the ENG OVSP TEST A or B button for the duration of the start sequence. A self-test of the hot-start prevention system is performed while conducting a normal Np overspeed system test.

Question 43

Fault Diagnostic System

Answer 43

The EDECU incorporates signal validation for selected input signals within the electrical control system. If a failure has occurred while the engine is operating, the failed component or related circuit will be identified by a preselected fault code. It is possible to have more than one fault code detected and each code should be treated as an individual fault. Once both engines are shut down, fault codes will be displayed numerically on the engine torque indicator with a brief description in text below the vertical instruments on the WCA page. Codes are displayed starting with the lowest code (4 seconds on and 2 seconds off), rotating through all codes, and then repeating the cycle. They can be suppressed and recalled by pressing either one of the ENG OVSP TEST buttons. Once the problem has been corrected, the codes will be cleared and may be verified after operating the engine at FLY.

Question 44

Note: Failure to suppress the EDECU fault codes will prevent ____________ due to the torque signal being relayed to the AFCC computer.

Answer 44

AFCS ground checks and automatic blade fold from operating

Question 45

Transient Droop Improvement

Answer 45

The TDI system is designed to initiate power turbine acceleration early by using anticipator signals from the TDI Nr sensor located on the left accessory module and a collective position sensor in the mixing unit. Circuits in the EDECU increase fuel flow to the engine via the HMU torque motor servo at low torque settings when collective demand is increased rapidly or in the event of rapid Nr decay

Question 46

Auto Ignition System

Answer 46

When an Np overspeed condition is reached and during the Np overspeed test, the overspeed valve located in the ODV is opened to reroute fuel flow to the HMU inlet. When Np drops below 120%, the auto-ignition system closes the overspeed valve and turns on the igniters for 5 seconds to relight the engine. The Np overspeed/auto-ignition system will continue cycling until Np/Nr is controlled. A yaw kick may be experienced each time engine relights.

Question 47

Ng Decay Relight Feature

Answer 47

The auto-ignition system also includes an Ng decay rate relight feature. If an engine flames out for any reason and exceeds a specified Ng deceleration rate, the auto-ignition system will turn on the igniters for 5 seconds in an attempt to relight the engine. The Ng decay rate relight feature is disabled below 62% Ng.

Question 48

The ac powered ignition system includes an ignition exciter unit, mounted on the right side of the engine main frame, and _________ .

Answer 48

two igniter plugs