Engines Flashcards
The engines have a ____ starter.
Pneumatic
What are the different air sources to start an engine?
1.) APU
2.) Engine Cross-Bleed
3.) Buddy Start
5 engine sections
Inlet (includes IPS mounted fwd of compressor
Compressor (6 stage: 5 axial, 1 centrifugal)
Combustor (12 fuel injectors, 2 spark ignitors)
Turbine (4 axial flow turbine wheels)
Exhaust
The IPS directs airflow into the ___ and provides mounting for the ____.
Compressor; accessory gearbox
What do the first two turbine wheels drive? What signal is given from the first two turbine wheels?
Compressor and AGB ; Ng
What do the second two turbine wheels drive? What signal is given from the second two turbine wheels?
MGB ; Np
How many thermocouples are there? What signal is generated from thermocouples?
7 ; TGT
Np is sensed by two Np sensors in the ___ section of the engine.
Exhaust
What four components actually control the engine?
EDECU, HMU, Engine-driven alternator, and fuel flow control valves
The HMU controls the gas generator by monitoring what factors?
Acceleration limiting
Stall and flameout prevention
Gas generator speed limiting
Rapid response to power demand
Variable geometry actuation
____ trim the HMU to satisfy load requirements to maintain Nr, load sharing, and limit TGT
EDECU
What does PCL stand for?
Power Control Lever
What are the positions of the PCL?
OFF
IDLE
FLY
LOCKOUT
What spindle does the PCL control?
The Power Available Spindle (PAS)
How do you enter LOCKOUT?
Advance PCL to LOCKOUT then back to FLY
What does LOCKOUT override?
EDECU and the control functions of the EDECU:
Auto TGT governing
Auto Nr governing
Loadsharing
What factor is not overridden in LOCKOUT and why?
Overspeed ; overspeed control is an independent function controlled by the overspeed drain valve, not the EDECU
How do you cancel LOCKOUT?
Decrease PCL to IDLE then back to FLY
What controls the Load Demand Spindle (LDS)?
Collective
The engine speed trim switch will increase or decrease what of both engines?
Np
What is the adjustment range of the engine speed trim switch? What is it typically set at?
96%-101% ; typically set at 100%
What trims fuel to maintain set engine Np?
EDECU
What happens if LDS roll pin shears?
LDS cable driven full aft, providing max LDS demand. May produce a Tq split. May be high enough to drive Np/Ng to overspeed limits.
Ng overspeed?
Np overspeed?
Ng overspeed: 110 +/- 2%
Np overspeed: 120 +/- 1% (will reset when Np drops below limit)
What are the 4 functions of the overspeed drain valve?
1.) Provide fuel to manifolds and 12 injectors
2.) Return fuel back to HMU if Np overspeed solenoid energizes
3.) Purge main fuel manifold overboard after shutdown through SOV and drain valve
4.) Shuts off fuel to prevent hot start by hot start preventer
The engine driven alternators three windings independently supply power to what?
1.) EDECU
2.) Ignitor assembly
3.) Ng signal to EICAS
What happens when Ng signal generated by engine driven alternator is lost?
No Ng signal on EICAS
Red X on respective engine display
“No.1/No.2 ENG OUT” w/ Master Warning
What is considered a hot start?
> 900 degrees C w/ Ng below 60% and Np below 50%
What function allows engines to operate at a higher TGT?
Contingency Power
What is lost with Contingency Power?
ECS (bleed air is retained to increase TGT)
What factors cause the EDECU to initiate auto-contingency power?
1.) Np less than 96%
2.) Greater than 3% droop b/w Np speed and Np Ref speed
3.) Greater than 5%/second Np droop rate when actual Np is less than or equal to Np Ref speed
Will there be a notification when the EDECU initiates auto-contingency power?
No
During start, at ___% Ng, the variable guide vanes closes the anti-ice/start bleed valve.
90% Ng
IDLE Ng %
52-65% Ng
FLY Ng %
96-101% Ng
The engines are governed to maintain a Tq match under ___%.
Within 5% Tq of each engine
Prior to a cross-bleed start, the donor engine must be operating at a minimum of ___% Ng
90% Ng
“ENG OUT” and Red X displayed if Ng drops below ___%
Below 55% Ng
There are two Np sensors in the exhaust from. What specifically do the left and right sensors provide?
Left: Np governing and Tach signal to EDECU
Right: Tq computation circuit and Np overspeed protection
