Engines/APU Flashcards
Thrust Reference Modes
Takeoff:
- TO
- TO 1
- TO 2
- D-TO
- D-TO 1
- D-TO 2
Climb:
- CLB
- CLB 1
- CLB 2
Continuous:
- CON
- CON 1
- CON 2
Cruise:
- CRZ
- CRZ 1
- CRZ 2
Other:
- GA
- MAN
EGT Start Limit Line
Displayed (Red) prior to and during engine start until engine is stabilized
When is the Inflight start envelope displayed
- respective Fire Switch in
- Fuel Control switch is in CUT OFF
- N2 RPM(N3-RR) is below idle
- Primary and Secondary EICAS displayed
Secondary EICAS engine indications
- N2 RPM
- Fuel flow (FF)
- Oil pressure
- Oil temperature
- Oil quantity
- Vibration
Engine vibration indication sources
N1
N2
BB - source is unknown and average vibration is displayed
When does the Standby Engine Indicator (SEI) in view?
In AUTO:
- AC Power is lost
- EICAS display failed
Selected ON
Engine Start Valve light illuminated (amber)
- start valve not in commanded position
- N2 RPM exceeds 50% and starter valve open
Engine Start Selector positions
GND
- Opens Start Valve
- arms selected ignitors
- selector magnetically held in GND position until 50% N2
AUTO
- closes start valve
- terminates ignition
- selected ignitors operate continuously when slats extended or engine Anti-ice ON
OFF
- no ignition
CON
- selected ignitors operate continuously (no time limit)
FLT
- Both ignitors operate continuously (no time limit) regardless of selector position
EEC Power Switch
NORM - Aircraft power provided to EEC when engine is not running
ALTN - Permanent magnet alternator (PMA) selected to provide power to EEC when engine is running
APU Fault Light
- APU has automatically shutdown
* APU fuel valve disagrees with the commanded position
APU Selector in the OFF position
- Closes APU bleed air valve, if open
- Initiates APU cooling cycle
- Closes the APU fuel valve and inlet door shutting down APU when cooling cycle is complete
- Resets auto shutdown fault logic
Engine description (PW)
- 2 x Pratt and Whitney PW2037
- 37,000 lbs of takeoff thrust
- two-rotor axial flow turbofans of high compression and bypass ratio
- N1 Rotor —> Fan, low pressure compressor, low pressure turbine
- N2 Rotor —> high pressure compressor, high pressure turbine
- N2 Rotor drive accessory gear box
Primary Engine Indications (PW)
- EPR
- N1
- EGT
What determines max EPR value?
- Electric Engine Control (EEC), or
- Thrust management computer (TMC)
*EPR varies with existing ambient conditions
Reduced takeoff trust ratings
TO 1 - approx 91% of takeoff thrust
TO 2 - approx 81% of takeoff thrust
How is Assumed Temperature Takeoff thrust calculated
- Thrust Management Computer (TMC) calculated the reference EPR(N1 - 767)
- temp entered via TMSP or CDU TO Ref page
- limited to 25% reduction of takeoff thrust or selected climb thrust
Reduced Climb Thrust rating
CLB 1 - approx 92% of max climb thrust
CLB 2 - approx 85% of max climb thrust (noise abatement reduced thrust level)
Purpose of EECs
- electronic engine control
- dual channel (primary and secondary)
- set thrust by controlling EPR based on thrust lever position
- powered by respective engine PMA when engine is running
When does EEC switch from Primary to Secondary Control mode?
- Primary can set thrust using EPR, N1, or N2 control mode
- Secondary can only use N1 or N2 control mode
- automatic switching occurs when primary mode becomes incapable of maintaining control
- automatic switching also occurs when engine shutdown inflight
How can you determine EEC has switched from EPR to N1 control mode
- EPR display blanks
- small thrust increase
N2 Control Mode
- EEC operation in EPR or N1 not possible
- ENG LIM PROT illuminates
- automatic thrust limit protection is not available
- inflight idle speed between both engines may be different
- EGT and rotor speeds must be monitor during reverse thrust operation
L or R ENG STATOR EICAS message
- both channels of EEC are unable to control stator vane actuator
- if engine fails and messages remain displayed engine restart is not possible
Engine Overspeed Protection
- EEC provides N1 and N2 red line Overspeed protection
- If N1 or N2 approaches overspeed, EEC commands reduced fuel flow
- no EGT overtemp protection
Engine Start Sequence (PW)
- ENG START selector to GND:
- opens start valve
- engages air driven starter (connected to N2 rotor)
- closes engine bleed valve
- FUEL CONTROL switch to RUN as N2 accelerated to Maximum motoring speed (less than 1% in 5 sec)
- opens spar and engine fuel valves
- activate selected ignition (normally one ignitors for grnd start and two for inflight starts)
- at approx 50% N2
- ENG START selector moves to AUTO
- starter cuts out and start valve closes
- engine bleed valve opens
Starter Normal Duty Cycle and Re-engagement speed
- 3 attempts of up to 2 mins each followed by cool down to 0% N2
- 15 min cool down after 3 attempts
Re-engagement speed:
0% N2 - recommended
0-20% N2 - normal
Power source for Ignition
Primary - Main AC power
Backup - STBY AC power
How is fuel routed from tank to engine?
- Fuel supplied by pumps located in fuel tanks
Spar Valve (located in main tank) —> 1st stage engine fuel pump (pressure added) —> fuel/oil heat exchanger (preheated) —> fuel filter —> 2nd stage engine fuel pump (pressure added) —> fuel control unit (control by EEC for fuel metering) —> engine fuel valve —> engine
Where are Oil Temp and Oil Pressure measured?
- Oil pressure is measure prior to entering the engine
- Oil temp is measure after leaving the engine
Moving reverse thrust levers to interlock position
- autothrottle disengages
- auto Speedbrakes deploy
What happens when reverser system is activated
- reverser isolation valve opens allowing reverser sleeves to hydraulically move aft
- fan flow blocker doors rotate to direct fan air through stationary cascade guide vanes
- REV display above EPR (amber during transition; green when fully deployed)
APU operating envelope
- electrical power has priority over bleed
- electrical power is avail through entire aircraft envelope
- bleed avail to approx 17,000’
Compressor/Turbine stages PW-2037 (757)
- 1 stage Fan
- 4 stage LP compressor
- 12 stage HP compressor
- 2 stage HP Turbine
- 5 stage LP Turbine
Compressor/Turbine stages RR-RB211 (757)
- 1 stage fan
- 7 stage IP compressor
- 6 stage HP compressor
- 1 stage HP turbine
- 1 stage IP turbine
- 3 stage LP turbine
Compressor/turbine stages CF6-80C2 (767)
- 1 stage fan
- 4 stage LP compressor
- 14 stage HP compressor
- 2 stage HP turbine
- 5 stage LP turbine
APU Control Switch ON
ON (APU operating position) -
- Opens APU fuel valve and inlet door
- Activates AC or DC fuel pump
- Powers the APU controller
- Permits the APU bleed valve to open if the APU Bleed switch is on when APU reaches
operating speed
How many batteries are required for APU start?
2 - APU Battery and Main Battery
– APU battery powers inlet door, starter and start circuitry
– Aircraft battery powers DC fuel pump, fuel valve, and fire detection
What signals that the APU self test has been conducted?
The APU RUN light will illuminate twice during start
Maximum thrust reduction allowed by Thrust Management Computer (TMC)
25% of Takeoff Thrust or Selected Climb Thrust, whichever is the greater thrust value
What lights illuminate during APU Start Sequence
• During APU start sequence, the following lights illuminate: o FAULT (once) as APU fuel valve opens o RUN (twice) as self-tests occur
