Powerplant and Related Systems - NATOPS CH 2.1 Flashcards
What is the name of the engines?
T700-GE-401C
What are the five sections of the engine?
Inlet, compressor, combustion, turbine, exhaust
How is inlet cowling air heated?
Fifth stage bleed air flowing into inlet cowling, and heating the exposed inlet surface through small perforations.
What do the swirl vanes do?
Impart rotation to the airflow at the intake.
Why are the swirl vanes hollow?
Anti-icing by fifth stage bleed air
What is the IPS?
Inlet Particle Separator
Particles are thrown outboard after the rotation is imparted to the air, into the collection scroll and then dumped overboard by the blower assembly.
What removes the rotation from the air to provide smooth airflow to the compressor?
Deswirl vanes
What type of compressor do we have?
Five stage axial, single stage centrifugal.
What type of combustion chamber do we have?
Flow through, annular
How many igniters per engine?
2 igniters
How many injectors per engine?
12 injectors
How do the injectors receive fuel?
Via the ODV
What two components does Ng drive?
Compressor and AGB
How many stages is Ng?
Two stage, air cooled, axial design
What does Np drive?
The power turbine drive shaft
Explain the Ng and Np shafts.
They are coaxial, with Np turning inside of Ng.
Explain the connection from Np to the transmission.
Np turbine drive the Np shaft, which extends forward and connects to the high speed shaft, which in turn connects to the input module.
Where is TGT sensed?
In between the gas-generator and the power turbine (Ng and Np).
How much airflow is used for combustion? What is the rest used for?
30%
Inlet temp (T2)
Discharge px (P3)
Combustion and turbine cooling
Engine oil seal pressurization
What provided gas generator control? What controls power turbine load?
HMU provided Ng control. EDECU trims the HMU to satisfy Np load requirements.
What does the engine control quadrant consist of?
PCLs
Fuel selector levers
Engine T handles
Rotor brake interlock
What are the four positions of the PCL?
OFF - IDLE - FLY- LOCKOUT
What is happening with the PCL in the off position?
The Power Available Spindle (PAS) is mechanically shutting off fuel at the shutoff valve in the HMU.
What is lost and what is retained in LOCKOUT?
TGT limiting, load sharing, and Np governing are lost.
Np overspeed protection is retained via a direct link between the EDECU and ODV.
What does the rotor brake interlock do?
A solenoid on the quadrant activates a mechanical locking device to prevent the PCLs from being advanced above IDLE with the rotor brake on.
What is the LDS?
Load demand spindle
This is how the HMU responds to collective position, to automatically control engine speed and provide required power.
This mechanical linkage ensures that the engines still respond to collective position even in LOCKOUT.
How do the engines receive fuel?
Engine-driven fuel boost pumps which provide reliable suction feed and provide discharge pressure to satisfy inlet pressure requirement of the HMU.
Does the engine fuel filter, filter water?
No
Where does fuel go after the engine fuel filter?
Routed to the HMU high pressure fuel pump
What is the HMU?
Hydromechanical Control Unit
What are the three reasons fuel is tapped off from the HMU?
- Position metering valve
- Position servo to the variable geometry vane servo and start bleed valve.
- Amplify T2, P3, Ng signals.
What are the three inputs to the HMU? (2 mechanical, 1 electrical)
- LDS
- PCL
- Electrical signal from EDECU
What does the metering valve do?
Schedules fuel flow commensurate to current power demand and is trimmed by the torque motor servo in response to EDECU signals.
How does the HMU provide feedback to the EDECU?
Via the Linear Variable Displacement Tranducer. Nulls the torque motor servo input, stabilizing it and preventing engine hunting/oscillation.
When does the Ng over speed valve trip?
110 +- 2% Ng
Explain what happens with an Ng overspeed.
Ng servo reached a position corresponding to an overspeed. Spring loaded ball valve ports fuel pressure, causing the minimum pressure valve to secure fuel flow to the engine.
What are the two reasons that when in FLY, actual engine power level is more than required?
- Fail safe to high power - torque motor is energized closed so if it loses current, the valve opens and maximum power is available.
- Power with one engine inop - remaining engine can increase gas generator up to its C PWR limit to carry the load.
What are the 6 functions of the HMU?
Rapid engine transient response through collective compensation
Auto fuel scheduling for start
Ng overspeed protection - 110+-2%
Flameout and compressor stall protection
Acceleration limiting
Ng governing
What are the four functions of the Overspeed Drain Valve?
Traps fuel upstream, keeping fuel/oil heat exchanger full so priming isn’t required
Returns fuel back to HMU inlet in the event of an Np overspeed or hot start
Injectors - provided fuel to 12 injectors
Purges fuel overboard after shutdown to prevent coking of injectors
What defines TGT limiting?
Reaching either MRP or CRP functions within the EDECU.
What defines HMU fuel flow limiting?
Ng, TGT, torque will be below NATOPS limit
- The max fuel flow provided is limited by the physical size of the fuel lines within the HMU and ODV. Occurs under certain combinations of PA and temperature.
- EPR limiting - HMU is designed to protect the compressor section by limiting fuel flow as a function of Ng and ambient temperature.
What happens if you increase collective when TGT or fuel flow limited?
Rotor will droop below 100% without a rise in TGT or Ng
How is torque limited defined?
Only defined by NATOPS Ch. 4 torque limits
What defines Ng limited?
NATOPS Ch. 4 Ng limits.
Will you droop if Ng is at limit and collective is increased?
No, Nr will remain at 100%, Ng will increase along with TGT and torque.
What specifically causes you to droop in regards to TGT limiting?
EDECU MRP or CRP functions (TGT reaching 866+-10 or 891+-10)
All essential engine electrical functions are powered by the ___________.
Alternator
What three things does the alternator specifically provide?
- Ac power to igniter assembly
- Ac power to EDECU
- Ng signal to vertical instruments
Dual engine Auto Contingency Power
TGT within 11C of the MRP limiter setting, plus one of the following conditions:
1. Np drop below 96%
2. Greater than 3% droop between actual and reference Np set point
3. Greater than 5% per second Np droop rate exists with Np less than of equal to reference set point
