Ch. 2 The Engine

Question 1

What type of Engine do we have?

Answer 1

T700-GE-401C

Front-Drive Turboshaft Engine

Question 2

What are the Sections of the Engine?

Answer 2

Inlet
Compressor
Combustor
Turbine
Exhaust

Question 3

Compressor Section

Answer 3

5 stage axial
1 stage centrifugal
Rotor stator assembly

Question 4

Combustion Section

Answer 4

Flow-through, annular combustion chamber.

2 igniters
12 injectors

Question 5

Gas-Generator turbine

Answer 5

Ng turbine drives the compressor and AGB.

2 stage, air cooled, high performance, axial design.

Question 6

Power Turbine

Answer 6

Np turbine has 2 stages that turn the power turbine drive shaft.

Shaft is coaxial turning inside the Ng driveshaft, extending through the front of the engine where it connects to the high speed shaft to the input mod.

TGT is sensed between Ng and Np turbines

Question 7

Engine Air Flow

Answer 7

30% for combustion

Remainder for:
1. Compressor inlet temp (T2)
2. Compressor discharge pressure (P3)
3. Combustor turbine cooling
4. Engine oil seal pressurization

Question 8

AGB Driven by?

Front Face?

Rear Face?

Answer 8

Driven by a radial drive shaft from the Ng turbine.

Front face provides drive pads for the alternator and engine driven boost pump.

Rear face provides drive pads for engine starter, HMU, IPS blower and ODV

Question 9

LDS Operation

Answer 9

With the PCL in FLY, the HMU responds to collective position through the LDS to automatically control ENG speed and provide required power.

Question 10

ENG Driven Boost Pump

Answer 10

Mounted on the forward side of the AGB

1. Provide reliable suction feed from the fuel tank to the engine,
2. Provide discharge pressure to satisfy the minimum inlet pressure of the HMU

Question 11

Fuel Tapped From the HMU for the following

Answer 11

1. Positioning a 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 signals (T2, P3, Ng) that influence fuel flow.

Question 12

HMU receives cockpit inputs and responds to PCL for?

Answer 12

1. Fuel shut off
2. Setting engine start fuel flow
3. Setting permissible Ng up to maximum
4. Fuel priming
5. EDECU LOCKOUT

Question 13

HMU Provides

(RANNAF)

Answer 13

1. Rapid engine transient response through collective compensation
2. Automatic fuel scheduling for start
3. Ng overspeed protection
4. Ng Governing
5. Acceleration Limiting
6. Flameout and compressor stall prevention

Question 14

ODV 4 Main Functions

Answer 14

1. Provides fuel to 12 injectors
2. Purges the fuel manifold overboard after engine shut down
3. Traps fuel upstream keeping the fuel oil heat exchanger full
4. Returns fuel back to the HMU if the Np overspeed is energized or EDECU hot start prevention

Question 15

Engine Limiting?

Question 16

Windings of the alternator?

Answer 16

Provides AC power to
1. Igniter assembly
2. EDECU
3. Ng signal to the VIDS

Question 17

16 Functions of the EDECU

4N(+A), 4C, 3E (last 4)

Answer 17

1. Ng decay relight feature
2. Np Governing
3. Np Over Speed Protection
4. Np Overspeed Test
5. Auto Ignition
6. TGT Limiting
7. Manual C-PWR
8. Auto C-PWR
9. Dual ENG Auto C-PWR
10. Engine Load Sharing
11. Engine Speed Trim
12. EDECU Lockout
13. Cockpit signals
14. Hot Start Prevention
15. TDI
16. Fault Diagnostics

Question 18

Np Governing

Answer 18

Np sensor located on the left side of the power turbine and provides signal to the EDECU. Actual compared to reference

Question 19

Np Over speed Protection

Answer 19

Actuated at 120% - ODV diverts fuel to the inlet of the HMU, causing flame out

Question 20

TGT Limiting

Answer 20

When TGT approaches 878 ( 866 +/- 10)(MRP), EDECU prevents further fuel flow increase. If more is demanded Np/Nr will droop.

Question 21

Engine Load Sharing

Answer 21

Torque matching system operates by increasing the lower engine torque while not directly effecting the higher engine

Question 22

Engine Speed Trim

Answer 22

INCR / DECR switch controls both engine Np at the same time. Provides EDECU with reference Np between 96 -101

Question 23

Manual C-PWR

Answer 23

TGT limit increased to 903 limit (891 +/- 10) (CRP Cont. Range Power)

With the switch flipped you will get #1/#2 C-PWR on advisory

Question 24

Auto C-PWR

Answer 24

TGT limit increased to 903 limit (891 +/- 10) (CRP Cont. Range Power)

Enabled in OEI conditions

When the torque from one engine is below 50% the opposite engine EDECU will automatically reset the TGT limiter

No advisory

Question 25

Np Over Speed Test

Answer 25

A & B buttons simultaneously resets Np overspeed limit to 96%. If Ng decreases when either button is depressed individually, the opposite button is faulty.

Question 25

Dual Engine Auto C-PWR

Answer 25

TGT limit increased to 903 limit (891 +/- 10) (CRP Cont. Range Power) One or more of the following must exist: 1. Np drops below 96% 2. Greater than 3% droop between ref. Np and actual Np 3. Greater than 5% per second Np droop rate exists with Np less than or equal to Np ref. No advisory

Question 26

EDECU LOCKOUT

Answer 26

PCL can manually control Ng and Np. Engine power set by LDS and PAS only Deactivating TGT limiting, Np Governing and load sharing. The Np over speed protection is retained

Question 27

Cockpit signals

Answer 27

Provides Np, TGT and Torq signals to the DTC for cockpit display

Question 28

Hot Start Prevention

Answer 28

Detects a hot start when TGT exceeds 900 with Ng below 60% and Np below 50% and automatically secures fuel flow by tripping ODV. Restored when TGT below 300 or after 25 seconds Can be disabled buy pressing and holding OVERSPEED TEST A or B button for duration of start sequence.

Question 29

TDI

Answer 29

Designed to initiate power turbine acceleration early by using anticipator from the TDI Nr sensor located in the LEFT ACCESSORY MODULE and a collective positioning sensor in the mixing unit.

Question 30

Auto-Ignition

Answer 30

When Np overspeed condition exists (or during overspeed test) the ignition sequence is automatically initiated for 5 seconds to relight the engine.

Question 31

Ng Decay Relight feature

Answer 31

If an engine flames our for any reason and exceeds a specified Ng decel rate, the auto ignition system will turn the igniters on for 5 seconds to attempt to relight the engine. Disabled below 62% Ng

Question 32

Fault Diagnostics

Answer 32

Fault codes are displayed numerically on the ENG torq indicator with a brief description in text below the vids 4 seconds on 2 seconds off can be suppressed and recalled with ENG OVSP test buttons

Question 33

3 Ways to ANTI ICE Engine

Answer 33

1. Vent bleed air into the engine swirl vanes and inlet guide vanes 2. Vent bleed air into the airframe engine inlet by the engine anti ice valve. 3. Continuously pump engine oil through the scroll vanes

Question 34

Malfunctioning Engine Anti-Ice

Answer 34

1. Appearance or disappearance of the ENG ANTI-ICE on advisory when outside the specified range 2. No appearance of ENG ANTI-ICE ON advisory with switch selected on 3. No rise in TGT when ENG ANTI ICE switch selected on

Question 35

Eng Anti-Ice/Start Bleed Valve

Answer 35

5th stage bleed air for anti ice and to prevent compressor instability during starts. Open below 80.5% Ng Closes above 96.5% Ng unless selected on or electrical power is lost

Question 36

ENG Inlet Anti-Ice

Answer 36

1. Less than 4*C the valve is open and advisory appears when temp reaches 93*C 2. Between 4*C and 13*C the valve is controlled by Freon-filled bellows. They begin closing at 4*C and should be completely closed at 13*C 3. Above 13*C the valve is closed and the advisories will extinguish when inlet cowling temp is below 93*C Appearance of INLET ANTI-ICE ON advisory when oat is above 13*C is and indication of a malfunctioning valve.

Question 37

TGT Sensing

Answer 37

The thermocouple harness consists of SEVEN thermocouples for measuring TGT. Joined in parallel and provide an average. Biased -71*C Without ENG OVSP CB the bias will be absent.