MH-60R - Systems - Engine System Flashcards
(80 cards)
0
Q
In general, what does the HMU provide?
A
Gas generator control
1
Q
Major Components of the Engine Control System
A
Hydro-mechanical Control Unit (HMU) Overspeed/Drain Valve (ODV) DECU/EDECU Engine Driven Alternator Series of Fuel flow control valves
2
Q
In general, what does the DECU/EDECU provide?
A
Trims the HMU to satisfy requirements of the power turbine load and reduces pilot workload.
3
Q
What does the Load Demand Spindle do?
A
Allows the HMU to respond to collective position to automatically control engine speed and provide required power.
4
Q
Components of the Engine Fuel System
A
Engine driven fuel boost pump, fuel filter, HMU, and ODV.
5
Q
Where is the Engine Driven Fuel Boost Pump mounted?
A
Forward side of the AGB
6
Q
What is the Engine Driven Fuel Boost Pump designed to do?
A
- Provide reliable suction feed from the aircraft fuel tank to the engine, minimizing vulnerability and fire hazard in the event of damaged fuel lines.
- Provide discharge pressure to satisfy the minimum inlet pressure requirement of the HMU or high-pressure fuel pump.
7
Q
What does the Engine Fuel Filter do?
A
Provides filtration of solid particulate matter, but does not filter water.
8
Q
When is the Impending Bypass PDI activated? The Impending Bypass warning?
A
9 psi, 18 psi
9
Q
Where is the HMU mounted?
A
Aft center of the RGB
10
Q
What is contained inside of the HMU?
A
High-pressure fuel pump, Ng Governor, metering valve, Linear Variable Displacement Transducer, Torque motor servo, variable geometry vane servo, vapor vent, and a shutoff vent
11
Q
How does fuel travel through the HMU?
A
Enters the HMU from a cored passage, leaves the high-pressure fuel pump and passes though he metering valve and shutoff valve, exits the HMU, and then passes through an external line to the oil/fuel heat exchanger.
12
Q
Why is some fuel tapped off inside of the HMU?
A
To operate various servos to accomplish 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 various signals (T2, P3, Ng) that influence fuel flow and variable geometry servo position.
13
Q
What inputs does the HMU respond to?
A
LDS- directly coordinates Ng speeds to the approximate power required by the rotor system based on collective position.
PAS- sets the desired power setting via the PCLs
Electrical signal from the DECU/EDECU- actuates the torque motor servo in the HMU to precisely trim Ng speed for power turbine control and load sharing.
14
Q
What does the HMU respond to the PCL for?
A
- Fuel shutoff
- Setting engine start fuel flow with automatic acceleration to ground idle.
- Setting permissible Ng up to maximum.
- Fuel priming.
- DECU/EDECU override capability (LOCKOUT)
15
Q
What other signals does the HMU respond to? Why?
A
T2, P3, and Ng.
These inputs aid the HMU in controlling variable stator vanes and anti-ice/start bleed valve position during engine start and normal operation, reducing the chance of compressor stall.
16
Q
What does the torque motor servo do?
A
Based on input from the DECU/EDECU, it trims down Ng by adjusting fuel flow through the metering valve.
17
Q
Linear Variable Displacement Transducer
A
Monitors current torque motor servo position through fuel tapping.
18
Q
Metering Valve
A
Receives fuel from the high-pressure fuel pump and directs metered fuel to the shutoff valve. Single fuel flow setting determine based on numerous inputs that include:
- torque motor servo
- mechanical input
- LDS
- PAS
- Ng governor
Maximum and minimum metering valve stops provide absolute fuel flow limits.
19
Q
What does the Shutoff Valve do?
A
Mechanically linked to PCLs, closes when PCL moved to OFF.
20
Q
What does the Vapor Vent do?
A
Last internal component that fuel passes through in HMU. Acts as a trap for air bubbles or fuel vapors and vents them overboard. Linked to he PCL through the PAS. When engines are being primed, it dumps fuel overboard.
21
Q
What does the Variable Geometry Servo do?
A
It’s a piston that changes the pitch angle of the variable geometry vanes to optimize airflow to provide efficient engine operation throughout the entire Ng range, receives a fuel input from the Ng governor. Actuates the engine anti-ice/start bleed valve.
22
Q
What does the High-pressure Fuel Pump do?
A
It’s a gear type pump that receives fuel from the fuel filter and sends it to the metering valve.
23
Q
What does the Ng governor do?
A
It receives a compressor inlet temperature (T2) and compressor discharge pressure (P3) signal, as well as Ng, and schedules fuel flow as necessary to maintain Ng within specified limits. If it sense an Ng overspeed condition, fuel flow to the engine is shutoff.
24
What does the HMU provide(6 things)
1. Rapid engine transient response through collective compensation
2. Automatic fuel scheduling for engine start.
3. Ng overspeed protection.
4. Ng governing.
5. Acceleration limiting.
6. Flameout and compressor stall protection.
25
What are the four main functions of the ODV?
1. Provides main fuel flow to the 12 fuel injectors during engine start and operation.
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 Ng overspeed is energized or if the DECU/EDECU hot start preventer is activated.
26
Describe the Alternator
Powers all essential electrical functions for the engine. Contains separate windings providing AC power to the igniter assembly, DECU, and Ng signal to the vertical instruments.
27
What does the DECU/EDECU do?
Resets the HMU win acceptable engine limits to maintain Np governing while automatically limiting TGT.
28
Where is the DECU/EDECU mounted?
Below the compressor casing. The forward face projects into the collection scroll case of the IPS, where it is cooled by scavenge airflow. Four connectors provide interconnection with other engine control components, airframe systems and diagnostic equipment.
29
What are the control parameters of the DECU/EDECU?
1. Np sensing (governing)
2. Np overspeed and torque sensing (load sharing, cockpit torque indication, and Np overspeed protection)
3. TGT monitoring (temperature limiting circuit)
30
What inputs does the DECU/EDECU receive from the cockpit?
1. ENGINE SPD TRIM switch.
2. CONTGCY PWR switch.
3. ENG OVERSPEED TEST A and B buttons
31
What inputs does the DECU/EDECU receive from the helicopter?
1. Torque from the other DECU/EDECU.
2. Np demand.
3. 400-Hz backup power.
4. HMU(LVDT
32
What signals does the DECU/EDECU send to the cockpit?
1. Torque
2. Np.
3. TGT.
4. Contingency power.
33
What functions does the DECU/EDECU perform?
1. Np governing.
2. Np overspeed protection.
3. TGT limiting.
4. Engine load sharing.
5. Engine speed trim.
6. Contingency power.
7. Np overspeed test.
8. DECU/EDECU Lockout.
9. Cockpit signals.
10. Hot start prevention.
11. Fault diagnostic system.
12. 400-Hz airframe backup power capability.
13. Transient Droop Improvement (TDI).
14. Auto-ignition system.
15. Ng decay relight feature.
34
Explain the Np governing feature of the DECU/EDECU.
DECU/EDECU receives an Np signal from the Np sensor on the left side of the power turbine section. That Np signal is compared to a reference Np to compute a speed error input signal for use in electrical control computation.
35
Explain the Np overspeed protection feature of the DECU/EDECU.
When the DECU/EDECU receives an overspeed indication from the Np sensor located on the right side of the power turbine section, the overspeed system is actuated (120% Np). A signal is then sent from the DECU to the ODV, diverting fuel to the inlet of the HMU, causing engine flameout.
36
Explain the TGT limiting feature of the DECU/EDECU.
Measured TGT is compared to a fixed reference. When the temperature is above the reference, a signal is generated to reduce fuel flow. When the TGT approaches 851C , the DECU/EDECU prevents any further increase in fuel flow to the engine. The IRP limiter will prevent is at 839 +/- 10C. If power demand is increased further, Np/Nr will droop below 100%; Np governing will be sacrificed to protect the engine against overtemperature.
37
Explain the Engine Load Sharing feature of the DECU/EDECU.
Torque signals are compared between the two engines is the respective DECUs/EDECUs. A torque error signal is generated if one engine torque is less than the other. The torque matching system operates by increasing the power on the lower torque engine, while not directly affecting the higher torque engine.
38
Explain the Engine Speed Trim feature of the DECU/EDECU.
An ENGINE SPD TRIM switch, located on the upper console, with positions INCR and DECR, controls the Np of both engines simultaneously. There is no individual engine trim capability. The ENGINE SPD TRIM switch supplies a reference electrical signal to the DECUs/EDECUs for controlling Np as required between 96% and 101% Np.
39
Explain the Contingency Power feature of the DECU/EDECU.
With the CONTGCY PWR switch placed in the ON position, this sends a signal to the DECU/EDECU to allow TGT to increase up to 903C; however the maximum Contingency Range Power (CRP) limiter will prevent further increase in fuel flow to the engine at 891 +/- 10C.
40
Explain the Np overspeed test feature of the DECU/EDECU.
Test mode is activated by the ENG OVERSPEED TEST A and B buttons. When both switches are actuated, the Np overspeed limit is re-referenced to 96% Np. If power turbine speed automatically decreases when either switch is depressed individually, the opposite test switch may be faulty.
41
Explain the DECU/EDECU LOCKOUT feature of the DECU/EDECU.
After being moved momentarily to LOCKOUT, the PCL is used to manually control Ng and Np. As a result, engine power is no longer controlled by the DECU/EDECU; It is set by the PAS and LDS positions only. With the PCL in LOCKOUT, the torque motor servo is disabled, therefore deactivating TGT limiting, Np governing, and load sharing. The Np overspeed system is still retained.
42
Explain the Cockpit signals feature of the DECU/EDECU.
The DECU/EDECU provides Np, TGT, and Torque signals to the Data Concentrator (DTC) for cockpit display.
43
Explain the Hot Start Prevention feature of the DECU/EDECU.
The DECU/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. Hot start prevention can be disabled by pressing and holding the ENG OVSP TEST A or B button for the duration of the start sequence. A self-test of the hot start system is conducted while performing the normal Np overspeed system test.
44
Explain the Fault Diagnostic System feature of the DECU/EDECU.
The DECU incorporates signal validation for selected input signals within the electrical control system. Signals are continuously validated when the engine is operating. If a failure has occurred , the failed component or related circuit will be identified by a preselected fault code. It is possible to have more than one fault code detected and each fault code should be treated as an individual fault. Fault codes are displayed when the following conditions are met:
1. Ng less than 20%.
2. Np less than 35%.
3. Other engine is shut down.
4. Aircraft 400 Hz power is available.
45
Explain the 400 Hz airframe backup power capability feature of the DECU/EDECU.
In the event of alternator failure, the DECU/EDECU functions receive 400 Hz AC power from the aircraft electrical system. A failure of either power supply system by itself will have no impact on the DECUs/EDECUs ability to control the engine.
46
Explain the Transient Droop Improvement (TDI) feature of the DECU/EDECU.
Designed to initiate power turbine acceleration early by using anticipatory signals from the TDI Nr sensor located of the left accessory module and a collective position sensor in the mixing unit. Circuits in the DECU increase fuel flow to the engine via the HMU torque motor servo at low torque settings when collective demand is increased rapidly or in the event of rapid Nr decay.
47
Explain the Auto-ignition system feature of the DECU/EDECU.
When an Np overspeed condition is reached and during the Np overspeed test, the overspeed valve is opened to reroute fuel flow to the HMU inlet. When Np drops below 120%, the auto-ignition system closes the ODV and turns on the igniters for 5 seconds to relight the engine. The system will continue cycling until Np/Nr is controlled.
48
Explain the Ng decay rate relight feature of the DECU/EDECU.
Also included in the auto-ignition system. If an engine flames out for any reason and exceeds a specified Ng deceleration rate, the auto-ignition system will turn on the igniters for 5 seconds in an attempt to relight the engine. Relight feature is disabled below 62% Ng.
49
What extra connector does the EDECU have and what does it do?
A fifth connector (E-4) to provide airframe identification to the EDECU, when required.
50
Explain the enhanced TGT limiting feature of the EDECU.
The EDECU incorporates an MRP limiter that limits TGT to 866 +/- 10C.
51
Explain the enhanced manual Contingency Power feature of the EDECU.
TGT limit in both engines is increased to 891 +/- 10C.
52
Explain the enhanced Auto-Contingency Power feature of the EDECU.
When torque from one engine is below 50%, the opposite engine EDECU will automatically reset the TGT limiter from 866 +/- 10C to 891 +/- 10C.
53
What torque values indicates the presence of a CEDECU? Which types? When?
Torque code is displayed 30 seconds after airframe power is applied. 35 +/- 2.9% indicates a CEDECU with Navy software, 15 +/- 2.9% indicates a CEDECU with Army software. 0% indicates the presence of a DECU or EDECU.
54
What are the functions of the DECU?
1. 400 Hz airframe power
2. Np governing
3. Np overspeed protection
4. Np overspeed test
5. Ng decay relight
6. Contingency power
7. Hot start prevention
8. Engine load sharing
9. Fault diagnostic system
10. TGT limiting
11. Auto-ignition system
12. Cockpit signals
13. Transient droop improvement
14. Engine speed trim
15. DECU lockout
55
The five sections of the engine
Inlet, compressor, combustor, turbine, and exhaust.
56
What does the compressor section consist of?
Five stage axial and one stage centrifugal compressor
57
What does the combustion section consist of?
consists of a flow-through, annular combustion chamber, two igniters, and 12 fuel injectors that receive fuel via the Overspeed and Drain Valve (ODV), supplying atomized fuel for combustion.
58
Describe the gas generator turbine
The Ng turbine drives the compressor and Accessory Gearbox (AGB). It is a two-stage, air-cooled, high-performance axial design.
59
Describe the power turbine
The Np turbine has two stages that turn the power turbine drive shaft. The shaft is coaxial, turning inside the gas-generator turbine drive shaft. It extends through the front of the engine where it connects to the high speed shaft, which in turn connects to the input module. The power turbine is comprised of the power turbine rotors, power turbine drive shaft, power turbine case, and exhaust frame. Turbine Gas Temperature (TGT) is sensed between the gas-generator and power turbine.
60
How is the airflow inside the engine used?
30% is used for combustion. The remainder is used for:
1. Compressor inlet temperature (T2)
2. Compressor discharge pressure (P3)
3. Combustor and turbine cooling.
4. Engine oil seal pressurization.
61
What is the thermal lockout of the engine oil pressure PDI?
38 degrees C
62
When does starter dropout occur?
Between 52% and 65% Ng.
63
Wha is the Ng requirement for the receiving and donor engine for a crossbleed start?
A minimum of 24% Ng shall be obtained on the receiving engine prior to advancing the PCL to fly. This requires an Ng of 90% to 94% on the donor engine.
64
What are the three ways to anti-ice the engine?
1. Vent bleed air into the engine swirl vanes and engine Inlet Guide Vanes (IGVs) by the engine anti-ice/start bleed valve.
2. Vent bleed air into the airframe engine inlet by the engine inlet anti-ice valve.
3. Continuously pump engine oil through the scroll vanes.
65
When does the gnome anti-ice/start bleed valve open/close?
The valve remains open below approximately 90 percent Ng to prevent compressor instability during starts. Above approximately 90 percent Ng, the anti-ice/start bleed valve closes, unless anti-ice is selected on, or the aircraft experiences a loss of electrical power.
66
Hat is indicative of a malfunctioning engine anti-ice/start bleed valve?
1. Illumination of the ENG ANTI-ICE ON advisory light with above 90 percent Ng or above 94 percent Ng if OAT is 15 °C or greater.
2. No illumination of the ENG ANTI-ICE ON advisory light when Ng drops below approximately 88 percent Ng. (Ng may vary on a sliding scale depending on OAT.)
3. No illumination of the ENG ANTI-ICE ON advisory light when the ENG ANTI-ICE switch is selected ON.
4. No rise in TGT when ENG ANTI-ICE switch is selected ON.
67
How does the inlet anti-ice valve operate?
1. Less than 4 °C, the valve is open and the INLET ANTI-ICE ON advisories appear when inlet temperature reaches 93 °C.
2. Between 4 and 13 °C, the valve is controlled by a temperature-compensating Freon-filled bellows. The bellows begins closing the valve when the OAT reaches 4 °C and should be completely closed by 13 °C.
3. Above 13 °C, the valve is closed and the INLET ANTI-ICE ON advisories will extinguish when inlet cowling temperature drops below 93 °C.
68
When does the inlet anti-ice advisory appear?
When bleed air heats the engine inlet to approximately 93 °C
69
How is Np and Torque sensed for each engine?
Two Np sensors are located on the top of the exhaust frame. The power turbine shaft is equipped with two pairs of teeth, which induce electrical pulses in the Np sensors. These teeth permit measurement of the torsion or twist of the shaft, which is proportional to output torque, by producing a pulse of electrical current each time a shaft or reference tooth passes. The sensors are identical and interchangeable, but serve different functions. The left sensor provides an Np signal to the DECU (used by the Np governing circuitry) and the cockpit vertical instrument. The right sensor feeds the torque computation circuit and the Np overspeed protection system. The electrical signal, which is conditioned in the DECU, provides a dc voltage proportional to torque for cockpit indication and use by various engine subsystems.
70
How is Ng sensed for each engine?
The alternator supplies an Ng signal to the vertical instruments in the cockpit.
71
How is TGT sensed for each engine?
The thermocouple harness consists of seven thermocouples for measuring TGT. The thermocouples are joined in parallel and provide an average output that is provided to the DECU. The TGT signal is biased -71 °C by the DECU then relayed to the TGT vertical instruments from the DECU.
72
What is the capacity of the engine oil tanks?
7.3 U.S. quarts
73
What is the note concerning use of oil in ambient conditions below -25 C?
When starting in ambient temperatures of -25 °C or below, lubricating oil MIL-PRF-7808 must be used. It is not advisable to mix MIL-PRF-23699 oil with MIL·PRF-7808 oil.
74
How long should you wait after shutdown to check the engine oil level?
20 minutes
75
How much should TGT increase when ENG ANTI-ICE is selected on?
30-100 C
76
How long should it take the INLET ANTI-ICE ON advisory to appear?
90 seconds
77
Caution about engines being cooled prior to shutdown
Engines should be cooled for 2 minutes at an Ng of 90 percent or less before moving PCL to OFF. If an engine is shut down without being cooled, it should not be restarted for 4 hours unless restart is performed within 5 minutes.
78
What do you do if engine starter advisory does not extinguish between 52-65% Ng?
Perform ENGINE STARTER advisory emergency procedure
79
When will ECS automatically shutdown?
The ECS will automatically shut down under the following conditions:
1. Engine contingency power is selected by either collective CONTGCY PWR switch.
2. No. 1 or No. 2 starter is engaged.
3. An ECS heating duct overtemperature exists.
When the AIR SOURCE ECS/START switch is placed to ENG, the ECS will also shut down when:
1. A TGT of 851 °C is reached.
2. Either ENG ANTI-ICE switch is placed ON.
3. The DE-ICE MASTER switch is placed to ON and ice is detected.
4. An ECS underpressure situation exists.
