NATOPS Ch 2: Powerplant And Related Systems

Question 1

5 Sections of the Engine and Related Components

Answer 1

Inlet, compressor, combustor, turbine, exhaust. The engine incorporates an integral water wash manifold, Inlet Particle Separator, top mounted accessory section, engine driven fuel boost pump, HMU, EDECU, a self-contained lubrication system, engine condition monitoring, and diagnostics provisions.

Question 2

Inlet Section

Answer 2

Includes inlet cowling, swirl frame, front frame, main frame, accessory section, and scroll case. The water wash manifold is an integral part of the swirl frame, which directs a series of jets into the compressor inlet area.

Question 3

Inlet Airflow

Answer 3

Inlet cowling (can be heated w/ 5th stage bleed air via the Inlet Anti-Ice Valve, inlet faring also perforated with small slits)

Then swirl vanes (impart rotation, also hollow for hot bleed air from the Engine Anti-Ice Valve)

Then IPS (prevents foreign particles from entering into compressor). Particles go to collection scroll. Air from collection scroll passes over scroll vanes which are filled with hot oil, this cools the oil. Good air goes through de swirl vanes.

Question 4

Compressor

Answer 4

5 stage axial, single stage centrifugal rotor/stator assembly.

Question 5

Combustion Section

Answer 5

Flow through, annular combustion chamber, 2 igniters, 12 fuel injectors that receive fuel from the ODV.

Question 6

Gas generator Turbine

Answer 6

Ng turbine drives the compressor and the AGB. It is a 2 stage, air cooled, high performance axial design.

Question 7

Power Turbine

Answer 7

Np turbine: 2 stages, turns power turbine shaft. Shafts are coaxial. Power turbine shaft connects to high speed shaft, then to the input module.

Consists of:

• Power turbine rotors
• Power turbine drive shaft
• Power turbine case
• Exhaust frame

TGT sensed between gas generator and power turbine.

Question 8

Engine airflow

Answer 8

30% of the total airflow through the engine is used for combustion. The remainder is used for:

• Compressor inlet temperature air (T2)
• Compressor discharge pressure air (P3)
• Combustor and turbine cooling
• Engine oil seal pressurization

Question 9

Main Frame and Accessory Section

Answer 9

Main Frame contains:

• Oil tank
• Oil level sight gauge
• AGB supports

Accessory section mounts to the rear of the main frame at the 12 O’clock position, above the scroll case. AGB is driven by a rotor via a radial drive shaft from the Ng turbine drive shaft.

Rear face drive pads:

• Engine starter
• HMU
• IPS blower
• ODV

Front face drive pads:

• Alternator
• Engine driven fuel boost pump

Mounting cavities:

• Lube and scavenge pump
• Chip detector

Face ported pads:

• oil cooler
• Fuel filter
• Oil filter

Question 10

Parts of the Engine Control System

Answer 10

HMU, ODV, EDECU, engine driven alternator, series of fuel control valves.

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

Question 11

PCL in OFF

Answer 11

PAS mechanically shuts off fuel at the shutoff valve within the HMU.

Question 12

PCL in IDLE

Answer 12

The HUM automatically controls the start sequence fuel flow allowing the engine to achieve self sustaining combustion.

Question 13

PCL in FLY

Answer 13

Sets the maximum level of power that could be supplied if demanded.

Question 14

PCL in LOCKOUT

Answer 14

PCL is used to manually control Np and Ng. TGT limiting, Np governing, and load sharing functions are deactivated and must be manually controlled. The Np overspeed protection system is retained via a direct link between the EDECU and the ODV. To return to automatic engine control, the PCL must be moved to IDLE and then returned to FLY.

Question 15

Load Demand System

Answer 15

With the PCL in FLY, the HMU responds to collective position, through a Load Demand Spindle, to automatically control engine speed and provide required power. When the PCL is moved to LOCKOUT and then to some intermediate position, the engine will still vary power in response to collective position.

Question 16

HMU Components

Answer 16

Val F4orsyth Ng eeds SML TV

Vapor vent
High pressure Fuel pump
Some fuel is tapped off to operate various servos in the HMU for the following
(1) Positioning a metering valve to ensure proper fuel flow to the engine
(2) Positioning a servo piston that actuated the VGVS and (3) start bleed valve
(4) Amplifying various signals (T2, P3, Ng) that influence fuel flow and VG servo position
Ng Governor
Shutoff Valve
Metering Valve
Linear Variable Displacement Transducer
Torque Motor Servo
Variable Geometry Vane Servo

Question 17

Fuel flow in HMU

Answer 17

Fuel enters the high pressure engine driven fuel pump in the HMU, then leaves the pump and passes through the metering valve and shutoff valve and is then directed through an external line to the oil to fuel heat exchanger.

Question 18

Inputs to the HMU

Answer 18

HMU responds to 2 mechanical linkages and one electrical signal from the cockpit.

1) Mechanical: LDS, HMU directly coordinates Ng speeds to the approximate power required but the rotor system based on collective position
2) Mechanical: PCL, Position of the PCL manipulated the PAS at the HMU setting the desired power setting.
3) Electrical: EDECU, actuates the TMS in the HMU to precisely trim Ng speed for power turbine control and load sharing.

Question 19

HMU responds to the PCL for:

Answer 19

1) Fuel Shutoff
2) Setting engine start fuel flow with automatic acceleration to ground idle
3) Setting permissible Ng up to maximum
4) Fuel priming
5) EDECU override capability (LOCKOUT)

HMU also responds to T2, P3, and Ng. These inputs aid the HUM in controlling variable stator vanes and anti-ice/start bleed valve position during engine start and normal operation, reducing the chance of compressor stall.

Question 20

HMU Operation

Answer 20

• HMU operates as a conventional gas generator control when there is not input to the torque motor from the EDECU
• HMU provides fuel scheduling for min flow, max flow, and variable stator vane control
• HMU fuel metering system controls fuel flow to the engine during all operating conditions
• Metering valve schedules fuel flow commensurate to current power demand and is trimmed to the required level by the TMS in response to EDECU signals.
• The HMU, via the LVDT then provides a feedback signal to the EDECU to null the TMS input

Question 21

Ng Overspeed

Answer 21

If the Ng servo within the the Ng governor reaches a position corresponding to an overspeed, a spring loaded ball valve ports fuel pressure causing the minimum pressure valve to secure flow to the engine. The Ng overspeed valve is set to trip at 110 +/- percent Ng.

Question 22

PAS-LDS-HMU Interaction

Answer 22

• PAS sets maximum available Ng
• Placing the PCL in FLY allows Ng to reach setting that provides intermediate power
• Collective movement adjusts available Ng to a power level approximately equal to the rotor load demand power
• The actual level of engine power in FLY is normally more than required by the helicopter

Question 23

HMU Fail Safe to High Power

Answer 23

• Torque motor, when energized, is designed to reduce the schedule to the desired power level
• Loss of TM electrical current causes the schedule to return to the highest power level
• A schedule that is biased high due to engine electrical failure doe not cause power limiting
• With all the engine protection functions in the HMU operational, neither engine damage nor stall can occur during or following loss of electrical signal to the TM

Question 24

HMU, Power Available with OEI

Answer 24

• In the event of a failure of one engine, the remaining engine’s gas generator can increase power sufficiently up to its limit (C power) to carry the load at the given LDS setting
• Load demand signal is introduced to the HMU through the LDS
• When LDS is reduced from max setting (adjusting the collective), Ng is reset from PAS setting to provide immediate and accurate gas generator response.
• This new Ng setting is trimmed by the EDECU to satisfy the Np governing and load sharing functions

Question 25

Functions of the HMU

Answer 25

The HMU provides: RANN AF 1) Rapid engine transient response through collective compensation 2) Automatic fuel scheduling for engine start 3) Ng overspeed protection 4) Ng governing (T2, P3, Ng), used to schedule fuel for min flow, max flow, and VGV control 5) Acceleration limiting. Ng governor ensures and PCL motion will result in safe engine operation and will not cause engine damage. Except for intentional shutoff of the the PCL, an inadvertent shutdown will not occur during PCL motion. 6) Flameout and compressor stall protection. HMU adjusts VGV position and opens the anti-ice/start bleed valve to prevent compressor instability.

Question 26

Overspeed and Drain Valve

Answer 26

Four main functions: 1) Provides main fuel flow to the 12 fuel injectors 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 EDECU hot start preventer is activated

Question 27

HMU Fuel Flow Limiting

Answer 27

- Ng value will be below NATOPS Ch4 limits, TGT will be below either IRP or CRP limiter values. Torque will also be within Ch4 limits. - Regions of of HMU fuel flow limiting are to the left of the peak values of specification torque on Ch22 P. A. Curves. 1) Under certain combinations of PA and temp with high power setting from the collective, the max fuel flow provided by the fuel pump is limited by the physical size of the fuel lines within the HMU and the ODV. For EDECU engines, this condition may occur with C power on or off (prior to the IRP TGT limiter). 2) HMU is also designed to protect the compressor section by limiting fuel flow as a function of Ng and the ambient temp. Called engine pressure ratio (EPR) limiting and has been associated with the term Ng limiting. EPR limiting can occur under cold ambient temps at any PA.

Question 28

Alternator

Answer 28

All essential engine electrical functions are powered by the alternator. The engine alternator contains separate windings providing AC power to the igniter assembly, EDECU, and Ng signal to the VIDS.

Question 29

EDECU Overview

Answer 29

- Trims the HMU within acceptable engine limits to maintain Np governing while automatically limiting TGT. - Cooled by scavenge airflow in the collection scroll case of the IPS Control parameters: - Np sensing (governing) - Np overspeed and torque sensing (load sharing, cockpit torque indication, and Np overspeed protection) - TGT monitoring (temp limiting circuit) EDECU receives the following inputs from the cockpit 1) ENG SPD TRIM switch 2) C PWR switch 3) ENG OVERSPEED TEST A and B buttons The EDECU receives the following input signals from the helo: 1) Torque from the other engine 2) Np demand 3) 400 Hz backup power 4) HMU (LVDT) The EDECU sends the following signals to the cockpit: 1) Torque 2) Np 3) TGT 4) C power

Question 30

Functions of the EDECU

Answer 30

16 Total 4N MEET FATHEADS Np governing Np overspeed protection Np overspeed test Ng decay relight feature Manual C power Engine speed trim EDECU lockout TGT limiting Fault diagnostics Auto C power Transient droop improvement ``` Hot start prevention Engine load sharing Auto Ignition system Dual auto C power Signals ```

Question 31

Np Governing

Answer 31

Np sensor on left side of power turbine sends signal to EDECU. Actual Np compared to reference Np to compute speed error.

Question 32

Np overspeed protection

Answer 32

Signal from Np overspeed and torque sensor on right side of power turbine. Overspeed system actuated at 120%. When Np exceeds 120%, signal is sent from the EDECU to the ODV, diverting fuel to the inlet of the HMU causing engine flameout.

Question 33

TGT limiting

Answer 33

Measured TGT compared to reference TGT. If temp is above reference, signal is generated to reduce fuel flow. When TGT approaches 878, the EDECU prevents any further increase in fuel flow to the engine. MRP limits TGT to 866 +/- 10. If power is increased further, Np/Nr will droop below 100%.

Question 34

Engine Load Sharing

Answer 34

Torque signals are compared between the 2 engines via EDECUs. Torque error signal generated if one signal is less than the other. Increases power on lower engine without directly affecting higher engine torque.

Question 35

Engine Speed Trim

Answer 35

Controls Np of both engines simultaneously. No individual engine trim capability. ENG SPD TRIM switch supplies a reference electrical signal to the EDECUs for controlling Np as required between 96 and 101%

Question 36

Manual C power

Answer 36

Sends signal to EDECU to allow TGT to increase to 903C, however max C range power (CRP) limiter will prevent further increase in fuel flow to the engine at 891 +/- 10C.

Question 37

Auto C power

Answer 37

EDECU provides auto c power, enabled in OEI conditions. When torque from one engine is below 50%, the opposite engine EDECU will automatically reset the TGT limiter form 866 +/- 10C to a max of of 891 +/- 10C.

Question 38

Dual engine Auto C power

Answer 38

Allows the EDECU to bypass the 10 min TGT limit of 866 +/- 10C and limit the aircraft at the C power TGT limit of 891 +/- 10C. For this feature to activate, one or more of the following conditions must exist: 1) Np drops below 96% 2) Greater than 3% droop between reference power turbine speed (Np) and actual Np reference set point. 3) 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

When both switches are activated, the Np overspeed limit is re referenced to 96% Np. If power turbine speed decreases when either switch is pressed individually, the opposite 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. Engine power is no longer controlled by the EDECU; it is set by PAS and LDS positions only. With the PCL in lockout, the TMS is disabled, therefor deactivating TGT limiting, Np governing, and load sharing. The Np overspeed protection system is retained.

Question 41

Cockpit Signals

Answer 41

EDECU provides Np, TGT, and torque signals to the DTC for cockpit display.

Question 42

Hot Start Prevention

Answer 42

EDECU detects a hot start when TGT exceeds 900C 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 300C or after 25 seconds, whichever occurs first. Can be disabled bu pressing ENG OVSP TEST A or B button for the duration of the start sequence. Self test of hot start prevention system is performed while conducting a normal Np overspeed system test.

Question 43

Fault Diagnostic System

Answer 43

EDECU incorporates signal validation for selected input signals whiting the electrical control system. If failure occurs while operating, failed component will be identified by preselected fault code. Treat each code as individual fault. Fault codes will be displayed numerically as a torque value and brief description in text below VIDS on WCA page. Can be suppressed by pressing either one of the ENG OVSP TEST buttons. Suppressed codes are not considered cleared. Codes are cleared once proper corrective action taken and verified that are cleared. Verify by stabilizing TGT above 425C with PCL in IDLE or FLY (as necessitated by OAT) and then performing a normal shutdown.