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.
