Engine Componets Flashcards
How is the N2 speed pickup driven and what does it do?
There is a gear around the power turbine shaft that drives an N2 drive gear which spins a shaft that spins a gear located in the accessory gearbox housing knows as a dual speed drive assembly. This assembly encases two sensors with magnetic pickups that read the speed of the gears. These 2 sensors (N2A and N2B) work with FADEC primary and reversionary to prevent catastrophic over speed/power turbine failure.
How many N1 signals are there?
Three:
Two of the speed signals is a function of the HMU-driven alternator. Used by the FADEC system.
N1 A is a magnetic speed sensor you can see looking at the outside of the HMU
N2 B is a function of the HMU driven alternator windings
The other speed signal is generated by the magnetic sensor mounted on the rear of the engine driven oil pump is for the cockpit N1 speed indication. It’s not utilized by the FADEC system.
How does the overspeed solenoid work?
The valve consists of an electrically controlled valve, spring-loaded to the full open position. The solenoid is controlled by the DECU. If a power turbine overspeed is detected an electrical signal is sent to the overspeed solenoid, activating the valve and reducing engine fuel flow. It opens and closes as needed as the trip point is reached. Can reduce fuel enough to bring engine to idle.
The aft mount link “dogbone” us adjustable for what reason?
Each link is adjusted to ensure the proper alignment of the engine drive shaft and combining transmission input adapter.
What does the fuel pressurizing valve do?
When the pressure of fuel drops below 40 psig on shutdown, the pressure valve closes and fuel is rerouted back to the boost pump.
What two input modes does the bleed band use to actuate?
1.) P3 air ports is used in primary mode
2.) Fuel pressure is used in Reversionary mode
Where does the P3 air tap go to?
1 goes to the HMA and Decu
And
1 goes to the bleed band actuator
When does bleed band popping happen and how can you recognize it on the gauges?
Happens when the bleed band isn’t fully opened or closed. Noticed by torque and temp fluctuations.
Which two bearings support the compressor section?
1 and 2
What bearings support the integral shaft?
3 supports the front of the shaft and 4 and 5 (hot) supports the rear
What bearings support the output shaft?
6 and 7 (located before quill shaft)
Which N1 pickup is only used for cockpit instrument?
The mag pick up off the back of the oil pump
How do you get the torque reading in the cockpit/decu?
The torquemeter head provides an electric torque signal that is proportional to the twisting motion of the power shaft. That signal is transmitted through a cable to the junction box. The junction box is mounted on the engine inlet housing. It provides operating power for the torquemeter head and receives signals from the head and sends them to the Ratio Detector Power Supply. The RDPS processes the signal coming from the junction box and sends this signal to cockpit torque indicator and engine digital electronic control unit (DECU).
What is the RDPS and how does it work?
The ratio detector power supply provides a 6 kHz constant current signal to the torquemeter head. It processes the signal coming from the junction box and sends this signal to cockpit torque indicator and engine digital electronic control unit (DECU). The ratio detector power supply is a solid-state inverter that converts dc voltage to ac voltage for use by the engine torque sensor (head assembly).
The engine torque signal processor is an airframe mounted unit consisting of an inverter, a signal conditioner and a power supply
What are the three colors for the wiring harness and what are their meanings?
Blue-reversionary: T1, N2B, HMA, back-up for primary harness
Yellow-Primary: HMA, N2A, start fuel valve, torque junction box
Green-accessory: oil pressure transmitter, oil temp, oil level, engine temp, ignition exciter, N1 speed pick up
How does ignition happen in the engines?
The ignition exciter interfaces with the igniter plugs to ignite the fuel/air mixture during engine start. The exciter box sends voltage to the coil assembly (little box right side of engine) where it is then split and sent to the 4 igniters via the igniter leads.
What is the N1 speed based off of?
Based off of the T1 sensor (T1 effects fuel mixture)
How many quarts of oil in each engine
Tank capacity is 12 quarts
System capacity is 15 quarts
Tom says 14 quarts
How many volts does exciter box send to coil assembly?
Vibrator transformer within the ignition unit converts a 28 volt DC input to 2500 volts.
How does the oil flow programming valve work?
Based off the N1 speed, it splits the oil and sends some to the hot end bearings and some to the cool end bearings. At lower power settings, excess oil is sent back to oil tank. This reduces coking on the bearings.
Provides oil pressure to the engine oil pressure transmitter, via the No. 2 bearing.
What is the snubber’s purpose on the engine oil pressure transmitter?
It reduces surges/pulsations and makes gauge indication more accurate
What does the fuel flow divider do?
At lower fuel demand, fuel is routed via primary fuel. As demand increases, primary and secondary fuel is routed. Excess unused fuel is routed back to engine driven fuel pump. Divider closes during engine shutdown to prevent fuel from entering the combustion chamber.
What does the fuel manifold consist of?
Consists of two halves of 14 fuel nozzles each for a total of 28 nozzles.
Dual fuel passageways are provided within the fuel manifold, a primary and secondary.
Nozzles insert through holes in the combustor section and into the combustion area.
Where is engine oil pressure measured?
It is measured with a pressure transducer at a point downstream of the programming valve, where the flow divides feeding the position 2 and 4/5 bearing sumps.
Where is the engine oil supply temperature measured?
Just before the fuel/oil heat exchanger.
What is the purpose of the HMA?
Provides metered fuel to the engine and controls the engine bleed band actuator for both primary and reversionary control.
How many, what types, and where in the engine?
2 main shift chip bearing sump detectors that are of the electrical gap variety
1 is in accessory gearbox
1 is in the #2,4,5 scavenge
What does the ignition exciter do?
It uses 28 vdc and converts it to 2500 vac
Can both engines overspeed at the same time?
No. Decu logic prevents this.
Is there bleed band modulation is Primary mode?
No. In primary, the bleed band is either fully opened or fully closed.
How many start fuel nozzles are there?
2 per engine
Bleed band popping occurs when?
Normally occurs at N1 settings between 81% to 86%. In reversionary mode.
Max altitude engine is rated for?
25,000 ft. Found in engine intro in theory of Ops
The accessory gearbox contains mounting pads for what?
Engine Driven Fuel Boost Pump.
Oil Pump.
PT Speed Pickup Drive Assembly.
Hydromechanical Metering Assembly (HMA)
Oil Filter Housing.
Scavenge Pump Housing
The accessory gearbox contain a chip detector. True or false?
True
The accessory gearbox has a self-sealing fuzz burn-off/chip detector installed. 4-56 in theory of ops.
What is the ambient temperature range that the engine oil lubrication system can operate in?
-65ºF to 130ºF
Where does the engine oil pump provide oil to (broadly/3 places)?
provides oil flow to the engine bearings, starter drive, and accessory gearbox.
How does the oil flow programming valve work?
At lower engine power settings, the oil pump will provide more oil flow than required by the engine lubrication system. The programming valve will control the oil flow based on engine demand, and bypass excess oil flow back to the engine oil tank.
Easy answer: Reduces oil flow at low power setting (N1).
What is the 3 in P3 stand for?
Location on the engine
The 4/5 bearing has its own scavenge element to help pull oil through bearing quicker. True or false?
True
What N1 is start fuel introduced?
Decu introduces start fuel at 8-12% N1
At what N1 is Secondary fuel introduced?
30-32%
What does the fuel power supply do?
It takes the aircraft’s 3 phase power and turns it into single phase 115 volt AC and sends it to the two fuel flow transmitters.
Where is the temperature measured on the engine transmissions?
The 190 degrees is measured as it leaves the engine transmission.
