Pack valves close (reopen after 30s if no start) LP Fuel opens Start valve opens Ignition @ N2 16% (immediately in flight) HP valves @ N2 22% (15% in flight) (20% neo) N2 50% (63% neo) Start valve closes Ignition stops (on ground) (55% neo) Pack valves reopen after 30s

Engines Flashcards by Robin Cross

What is on the accessory gearbox?

Oil feed pump
Main engine fuel pump (combustion chamber)
Hydraulic pumps
Generators
FADEC alternator
Pneumatic starter

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What does the FADEC control?

What two parameter protections are there?

Fuel flow
Accel / decel schedules
Variable bleed valve and stator vanes
Turbine clearance
Idle
- Modulated (bleed/ambient) - flight (clean) or ground
- Approach idle- allows rapid accel
- Reverse Idle- slightly higher than normal idle
Fuel circulation (IDG)
N1 / 2 overspeed
EGT during start

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What does the Hydromechanical Unit do?

What meters fuel to the nozzles?
What gives fuel flow feedback to FADEC?

How is the pressure drop kept constant across the FMV?

FF
Fuel hydraulic signals to actuators
Stops overspeeding

Fuel Metering Valve FRV
FMV resolver

Via bypass valve (directs fuel to FRV)

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What does FADEC control to manage N1?

FADEC control parameters to achieve what?

Controls FF
* allows N2 to vary*
Ensures FF reading is proportional to FMV position

limit accel/decel
avoid engine stall / flameout
limit max N1/N2
Maintain air bleed requirement

computes N2 correction according to bleed

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What can limit N2 independently from FADEC?

Overspeed Governor
Opens the Fuel Bypass Valve to limit N2 ico: malfunction

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Fuel Hydraulic Signals control
LPTCC valves
HPTCC valves
RACC system (MTC neo)
VSVs
VBVs

What do the VSVs and VBVs do?

LP Turbine Clearance Control
HP Turbine Clearance Control
Rotor Active Clearance Control
Modulated Turbince Cooling

Variable Stator Vanes
* Maintain optimum compressor efficiency
* Adequate stall margin
* Fully closed at start
* Fully open at high thrust

Vbv Variable Bleed Valves
* Upstream of HP compressor
* Setting depends on inlet temp and N2
* Full open for start
* Full closed for high thrust

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IDG cooling- FADEC /FRV controls flow

What target IDG temp?
What happens if hot oil but only low thrust / airflow?

If it gets hotter?
Hotter still?

When does the FRV close?

Mixes hot fuel with cold to maintain below 100ºC
At low thrust, and hot oil, cooling fuel returned to tank (300kg/h)
Increasing temp: ECU increases min N2
Further increasing: FADEC increases FF to tank (to 600 kg/h)
engine shut down
TO / CLB
Wing tank level under 300kg
Surge tank overflow
- Except on ground
Gravity feed
Wing tank temp over 52.5ºC (max JetA1 54ºC)
- Except on ground

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Five components and lay out of the oil system?

Components
* Tank
* Lub/scavenge pumps
* Fuel/oil heat exchanger
* Filters, chip detectors,
* pressure relief + bypass valve

Layout
* Engine > Scavenge > Filter > Heater > Exchanger > Tank
* Tank > Pump > Filter (bypass) > Sensors > Bearing+gearbox

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Cooling system, all controlled by FADEC via the HMU - what are the 3 systems and their functions?

RACC Rotor Active Clearance Control (compressors)
* FADEC via HMU
* Controls clearance between HP compressor rotors and stator case
* 5th stage compressor bleed
* Highest clearance when RACC valve closed

HPTCC system (turbines)
* FADEC via HMU
* Modulates HP compressor bleed flow
* Optimises HP turbine performance
* Reduces EGT

LPTCC
* FADEC via HMU
* Modulates fan bleed airflow (cooling)

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How many SECs required to send a reverse signal to engine?

One or both gear compressed to activate?

Just the one

Both gear compressed

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Reverser protection: when will auto restow engage?

When will idle protection engage?

Auto Restow
* If one door unstowed when reverse not selected
* Ground only, unless TO (N1 > 70%)

** Idle Protection**
* Idle thrust selected if reverse not selected and
* 4 doors unstowed
* 1 door unstowed/unknown with hydraulic pressure detected

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What supplies igniter A when in EMER ELEC?

Igniter A supplied by STAT INV BUS when operative

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On the first autostart, only one igniter is used (both for next start after a failure)

When does the igniter engage / disengage?

Above what elevation will both igniters engage on the ground?

Under which three circumstances will automatic continuous ignition engage?

N2 16% until 50%

Above 10,000 ft
Both igniters whenever in the air

EIU failure
Flame out
Ignition delay in start

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What faults can FADEC detect during a start?

Abort Sequence?

Hot start (insufficient air flow to cool combustion chamber)
Hung start (light but no accel)
Stall
Failed light
Low start air pressure
Starter time exceeded
Thrust lever not at idle

Abort Sequence

Closes HP valve and start valve
Turns off ignition
Dry crank

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Start sequence?

Pack valves close (reopen after 30s if no start)
LP Fuel opens
Start valve opens
Ignition @ N2 16% (immediately in flight)
HP valves @ N2 22% (15% in flight) (20% neo)
N2 50% (63% neo)
- Start valve closes
- Ignition stops (on ground) (55% neo)
- Pack valves reopen after 30s

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What decides if windmilling is fast enough for a start, or assistance required?

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FADEC

Manual Start Sequence?

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