Ch. 2 The Engine Flashcards
What type of Engine do we have?
T700-GE-401C
Front-Drive Turboshaft Engine
What are the Sections of the Engine?
Inlet
Compressor
Combustor
Turbine
Exhaust
Compressor Section
5 stage axial
1 stage centrifugal
Rotor stator assembly
Combustion Section
Flow-through, annular combustion chamber.
2 igniters
12 injectors
Gas-Generator turbine
Ng turbine drives the compressor and AGB.
2 stage, air cooled, high performance, axial design.
Power Turbine
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
Engine Air Flow
30% for combustion
Remainder for:
1. Compressor inlet temp (T2)
2. Compressor discharge pressure (P3)
3. Combustor turbine cooling
4. Engine oil seal pressurization
AGB Driven by?
Front Face?
Rear Face?
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
LDS Operation
With the PCL in FLY, the HMU responds to collective position through the LDS to automatically control ENG speed and provide required power.
ENG Driven Boost Pump
Mounted on the forward side of the AGB
- Provide reliable suction feed from the fuel tank to the engine,
- Provide discharge pressure to satisfy the minimum inlet pressure of the HMU
Fuel Tapped From the HMU for the following
- Positioning a metering valve to ensure proper fuel flow to the engine
- Positioning a servo piston that actuates the variable geometry vane servo and start bleed valve.
- Amplifying signals (T2, P3, Ng) that influence fuel flow.
HMU receives cockpit inputs and responds to PCL for?
- Fuel shut off
- Setting engine start fuel flow
- Setting permissible Ng up to maximum
- Fuel priming
- EDECU LOCKOUT
HMU Provides
(RANNAF)
- Rapid engine transient response through collective compensation
- Automatic fuel scheduling for start
- Ng overspeed protection
- Ng Governing
- Acceleration Limiting
- Flameout and compressor stall prevention
ODV 4 Main Functions
- Provides fuel to 12 injectors
- Purges the fuel manifold overboard after engine shut down
- Traps fuel upstream keeping the fuel oil heat exchanger full
- Returns fuel back to the HMU if the Np overspeed is energized or EDECU hot start prevention
Engine Limiting?
Windings of the alternator?
Provides AC power to
1. Igniter assembly
2. EDECU
3. Ng signal to the VIDS
16 Functions of the EDECU
4N(+A), 4C, 3E (last 4)
- Ng decay relight feature
- Np Governing
- Np Over Speed Protection
- Np Overspeed Test
- Auto Ignition
- TGT Limiting
- Manual C-PWR
- Auto C-PWR
- Dual ENG Auto C-PWR
- Engine Load Sharing
- Engine Speed Trim
- EDECU Lockout
- Cockpit signals
- Hot Start Prevention
- TDI
- Fault Diagnostics
Np Governing
Np sensor located on the left side of the power turbine and provides signal to the EDECU. Actual compared to reference
Np Over speed Protection
Actuated at 120% - ODV diverts fuel to the inlet of the HMU, causing flame out
TGT Limiting
When TGT approaches 878 ( 866 +/- 10)(MRP), EDECU prevents further fuel flow increase. If more is demanded Np/Nr will droop.
Engine Load Sharing
Torque matching system operates by increasing the lower engine torque while not directly effecting the higher engine
Engine Speed Trim
INCR / DECR switch controls both engine Np at the same time. Provides EDECU with reference Np between 96 -101
Manual C-PWR
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
Auto C-PWR
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
Np Over Speed Test
A & B buttons simultaneously resets Np overspeed limit to 96%.
If Ng decreases when either button is depressed individually, the opposite button is faulty.
Dual Engine Auto C-PWR
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
EDECU LOCKOUT
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
Cockpit signals
Provides Np, TGT and Torq signals to the DTC for cockpit display
Hot Start Prevention
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.
TDI
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.
Auto-Ignition
When Np overspeed condition exists (or during overspeed test) the ignition sequence is automatically initiated for 5 seconds to relight the engine.
Ng Decay Relight feature
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
Fault Diagnostics
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
3 Ways to ANTI ICE Engine
- Vent bleed air into the engine swirl vanes and inlet guide vanes
- Vent bleed air into the airframe engine inlet by the engine anti ice valve.
- Continuously pump engine oil through the scroll vanes
Malfunctioning Engine Anti-Ice
- Appearance or disappearance of the ENG ANTI-ICE on advisory when outside the specified range
- No appearance of ENG ANTI-ICE ON advisory with switch selected on
- No rise in TGT when ENG ANTI ICE switch selected on
Eng Anti-Ice/Start Bleed Valve
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
ENG Inlet Anti-Ice
- Less than 4C the valve is open and advisory appears when temp reaches 93C
- Between 4C and 13C the valve is controlled by Freon-filled bellows. They begin closing at 4C and should be completely closed at 13C
- Above 13C the valve is closed and the advisories will extinguish when inlet cowling temp is below 93C
Appearance of INLET ANTI-ICE ON advisory when oat is above 13*C is and indication of a malfunctioning valve.
TGT Sensing
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.
