NATOPS 2- Powerplant And HMU Flashcards
Five sections of engine
Intake, compressor, combustor, turbine, and exhaust
Compressor stages
Five stage axial and single stage centrifugal, rotor/stater assembly
Combustion section consists of
Flow through, annular combustion chamber, two igniters, 12 fuel injectors and receives fuel from the ODV
what is the Gas generator turbine and what does it drive?
Two stage, air cooled, high-performance axial design
The compressor and accessory gearbox.
Define the Power Turbine
2 stage, coaxial
Shaft connects to the high speed shaft which connects to the input module
TGT is sensed between the two turbines
what is 30% and 70% of Engine airflow used for?
30% used for the combustion process, 70% for:
- compressor inlet temperature (T2) air
- Compressor discharge pressure (P3) air
- Combustor and turbine cooling
- Engine oil seal pressurization
What does the HMU provide?
RANNAF (RANN Away Fast)
- rapid engine transient response through collective compensation
- automatic fuel scheduling for engine start
- NG overspeed protection
- NG governing
- Acceleration limiting
- Flameout and compressor stall prevention
NG overspeed protection:
HMU mechanically limits NG to 110 +- 2 %
Reaches the position corresponding to an overspeed, a spring loaded valve secures fuel flow the engine.
Once the overspeed condition has passed the valve will open and allow normal operation
The DECU trims ________
The HMU to
- satisfy the requirements of the power turbine load and
- reduce pilot workload
PCL positions
OFF- PAS mechanically shuts off fuel at the shut off valve in the HMU
IDLE- the HMU automatically controls start sequence fuel flow
FLY - that’s the maximum level of power that can be supplied
LOCKOUT - Manually controls NP and NG.
- loses TGT limiting, NP governing, load sharing
Collective is to ________ as PCL is to _________
Load demand spindle (LDS)
Power Available spindle (PAS)
Engine-driven fuel boost pump does what:
- Provide reliable suction feed from the aircraft fuel tank to the engine, minimizing fire hazard in the event of damaged fuel lines
- provides discharge pressure to satisfy the min inlet pressure requirement of the HMU or High-pressure fuel pump
Fuel is tapped off in the HMU for what?
1) positions a metering valve to ensure proper fuel flow
2) positions a servo piston actuates variable geometry vane servo and start bleed valve
3) amplifies T2, P3, Ng that influence fuel flow and variable geometry servo position
HMU responds to: 3 things
2 mechanical (LDS, PAS) 1 electrical (DECU) - actuates torque motor servo to trim NG speed
HMU responds to PCL for:
- fuel shutoff
- Setting engine start fuel flow with automatic acceleration to ground idle
- Setting permissible NG up to maximum
- Fuel priming
- DECU override capability (LOCKOUT)
The HMU provides feedback to the DECU via the _________.
Linear variable displacement transducer (LVDT)
Why is the engine power in the FLY position more that what is normally required?
- Fail-safe to high power = in case of the loss of the torque motor electrical current
- Power available with OEI = The operating engine’s gas generator can increase power sufficiently up to its limit to carry the load at the given LDS setting
Overspeed and Drain Valve functions:
PPTR
- provides fuel flow to the 12 fuel injectors
- purges the main fuel manifold to prevent coking of the fuel injectors
- traps fuel upstream so that priming is not required
- Return fuel back to the HMU if np overspend or DECU hot start prevention is activated
IPS is driven by
The AGB
SHP of engines?
Continuous?
Intermediate?
Contingency?
1662
1800 for 30 min
1940 for 2.5 min
Flow of air into Inlet section of engine
Air enters, hits swirl vanes, goes through the IPS and -either blown over board by blower assembly- or - hits the deswirl vanes and into the compressor.
What type of Engine do we have?
T700-GE-401C front-drive turboshaft engine
What is the waterwash manifold an integral part of?
the swirl frame
What does the HMU respond to with the PCL in FLY?
collective position through a Load Demand Spindle (LDS)
The engine fuel system consists of what?
Engine-driven fuel boost pump, fuel filter, HMU, and ODV
Engine fuel filter does not filter what?
water
What routes fuel to the Engine fuel filter?
Where does it go after?
Engine-driven fuel boost pump
routed to the HMU High-pressure fuel pump
What does the HMU contain?
- High-pressure Fuel pump
- NG governor
- Metering Valve
- LVDT
- torque motor servo
- variable geometry vane servo
- vapor vent
- shutoff valve
HMU Mechanical Linkage: The LDS directly coordinates __ speeds to the approximate power required by the rotor system based on collective position
Ng
What 3 inputs does the HMU receive to aid it in controlling variable stator vanes and anti-ice/start bleed valve position?
What does this reduce the chance of?
T2, P3, and Ng
Compressor stall
What trims the metering valve when it is scheduling engine fuel flow commensurate to current power demand?
The Torque motor servo in response to DECU signals
How does the HMU provide Ng Governing?
The HMU receives T2, P3, and Ng inputs from their respective sensors, which are used to schedule fuel for minimum flow, maximum flow, and variable geometry vane control
How does the HMU provide Acceleration Limiting?
The Ng governor ensures that any PCL motion will result in safe engine operation and will not cause engine damage or an inadvertent shutdown.
What are the two types of Engine Limiting?
- TGT Limiting - defined by reaching either IRP or CRP functions within the DECU/(C)EDECU
- HMU-fuel flow limiting - due to the physical dimensions of the fuel lines
- also is designed to protect the compressor section by limiting fuel flow as a function of Ng and ambient temperature
What will happen if you are Engine Limited and increase the collective?
The rotors will droop
What does the Alternator power?
- ignitor assembly
- DECU
- Ng signal to the vertical instruments
