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Boeing 747 > Engine and APU > Flashcards

Engine and APU Flashcards

1
Q

EGT display color indications

A

White - normal operating range
Amber - continuous (CON) limit reached
Red - start/TO limit reached

  • indication will remain white for 5 mins when CON limit is reached or exceeded during TO or GA
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2
Q

When is the Secondary Engine Indications displayed?

A
  • when EICAS first receives power

- in flight, with a fuel control switch moved to CUTOFF

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3
Q

What happens when FUEL CONTROL switch is placed in RUN?

A
  • opens spar fuel valve
  • opens engine fuel valve
  • EEC sequences start valve, fuel metering valve, and igniter operation (auto start)
  • energizes igniter(s) (manual start)
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4
Q

What happens when FUEL CONTROL switch is selected CUTOFF?

A
  • closes fuel valves
  • removes igniter power
  • commands respective hydraulic demand pump to operate when Demand Pump selector in AUTO
  • unlocks Engine Fire switch
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5
Q

When do igniters AUTOMATICALLY turn on?

A
  • during start when N2 RPM less than 50%
  • trailing edge flaps out of up position
  • nacelle anti-ice ON
  • engine flameout
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6
Q

What happens when you place APU selector to OFF position?

A
  • closes APU bleed air isolation valve
  • initiates normal shutdown
  • resets auto shutdown fault logic except when shutdown due to APU bleed duct leak
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7
Q

Describe Engine Types

A

4 x GE CF6-80C2-B1F - each produce 56,500 lbs of takeoff thrust

4 x GE CF6-80C2-B5F - each produce 62,100 lbs of takeoff thrust

  • dual axial flow, high compression, high bypass turbofans
  • N1 rotor——> Fan, low pressure compressor, and low pressure turbine
  • N2 rotor——> High pressure compressor and high pressure turbine - drives accessory gearbox
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8
Q

Primary and Secondary Engine Indications

A

Primary:

  • N1
  • EGT

Secondary:

  • N2
  • FF
  • Oil Temp
  • Oil Press
  • Oil Qty
  • Eng vibration
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9
Q

What calculates N1 and fuel flow for the engines?

A

Each engine has its respective Electronic Engine Control (EEC)

Each EEC:

  • uses thrust lever movements to control forward and reverse thrust
  • calculate N1
  • commands fuel metering to adjust actual N1 to calculated N1
  • powered by alternator in accessory gear box
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10
Q

Electronic Engine Control (EEC) modes?

A

Normal:

  • thrust is set by controlling N1 based on thrust lever position
  • adjust N1 based on pressurization and anti-ice bleed requirements
  • continuously computes maximum N1
  • thrust is limited to max computed N1 with thrust lever full forward

Alternate:

  • back up to normal mode
  • automatically or manually selected with EEC mode switch
  • provide equal or greater thrust at selected thrust lever position
  • does not provide thrust limiting and maximum N1
  • Max N1 is reached at thrust lever position less than full forward
  • thrust levers must be adjusted to maintain desired thrust as environmental condition and bleed requirements change
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11
Q

When does EEC command Approach Idle?

A
  • nacelle anti-ice is ON
  • flaps are in landing position
  • Continuous Ignition switch is ON
  • thrust reverser operation

*maintained until 5 mins after touchdown

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12
Q

How does EEC protect again Overspeed?

A
  • monitors N1 and N2 RPMs

- commands fuel metering unit to control fuel flow to rotor speeds from exceeding limits

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13
Q

What is the meaning of the Fuel-On indication on N2?

A
  • displayed when Fuel Control switch is in CUTOFF

- displays the minimum N2 RPM at which the Fuel Control switch should be moved from CUTOFF to RUN during a manual start

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14
Q

Indication provided to help in flight restart

A
  • In Flight Start Envelope is displayed on the Primary EICAS when Fuel Control switch is moved to CUTOFF in flight
  • envelope displays airspeed range to ensure restart at current flight level
  • X-BLD is displayed next to N2 if crossbleed start is needed
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15
Q

Primary source of bleed air for engine start

A

Primary source: APU

Secondary source: ground source and engines

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16
Q

AUTOSTART Sequence

A
  • EEC monitors start and sequences start valve, fuel valve, and igniter operation
  • AUTOSTART switch ON arms the AUTOSTART
  • pulling the START switch out opens ENG BLEED VALVE and arms START VALVE
  • AUTOSTART sequence is started when FUEL CONTROL switch is moved to RUN
    1) EEC opens START VALVE
    2) As N2 rises EEC determines when to open FUEL VALVE and energized igniters
    * one igniter for ground start and two for in-flight start
    3) STARTER CUTOUT at 50% N2
  • EEC monitors EGT and N2 until engine stabilizes at idle
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17
Q

Autostart system abort parameters

A

EEC monitors EGT and N2, does not monitor oil pressure or N1 rotation

ECC with abort start for:

  • Hung Start
  • Hot Start
  • no EGT rise
  • malfunction in the Autostart system

“Immediate Action Items”

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18
Q

What happens if EEC detects Hung, Hot, or no rise in EGT

A

No Rise in EGT:

  • fuel and ignition cutoff
  • engine motors for 30 sec
  • fuel and ignition (both igniters) are reapplied
  • 3 attempts are made before autostart is aborted
  • engine will motor for 30 sec before start valve and bleed valve are closed

Hung or Hot before starter cutout

  • fuel is cutoff and fuel schedule readjusted
  • fuel reapplied
  • 3 attempts are made before abort
  • engine will motor for 30 sec before start valve and bleed valve are closed

Hung or Hot after starter cutout

  • autostart sequence aborted immediately
  • engine does not motor
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19
Q

When is auto relight activated?

A
  • EEC activates both igniters when a flameout is detected

- detected with rapid decreases of N2 or N2 drops below idle

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20
Q

Normal and backup power source for the engine igniters

A

Primary power - AC power system

Back up power - Standby power system

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21
Q

Which valves open when FUEL CONTROL switch it selected to RUN?

A
  • spar valve
  • fuel metering valve
  • engine fuel valve

*Engine Fire switch must be in

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22
Q

How are engine thrust reversers actuated?

A
  • with forward thrust levers in closed position an interlock mechanism is released allowing thrust reverse levers to be raised
  • with reverse thrust levers raised to idle detent respective engine bleed air is used to unlock and deploy reversers
  • engine bleed air is also used to stow and lock reversers in case of inadvertent deployment
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23
Q

Which areas are monitored by the engine vibration system?

A
  • Fan (N1)
  • Low Pressure Turbine (LPT)
  • N2
  • Broadband (BB) is used to indicate if source cannot be determined
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24
Q

APU Operation limit

A
  • ground to 20,000’
  • can only be started on the ground
  • Electrical power only avail on the ground
  • Bleed air avail in flight for one pack up to 15,000’
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25
Q

How many APU Generators?

A

2 APU Generators (can supply entire electrical load on the ground)

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26
Q

How long is normal APU Shutdown sequence?

A
  • 60 seconds (for cool down)

- Batt switch should remain on until APU shutdown is complete

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27
Q

APU Start sequence

A

When APU selector is momentarily selected to start:

  • APU Fuel Valve and Inlet Door open simultaneously
  • ignition
  • light-off
  • engine acceleration
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28
Q

When will APU automatically shutdown?

A
  • Limit Exceeded

- Fire Detected

29
Q

What is a constant speed drive (CSD)?

A
  • part of the IDG
  • mechanism that acts as a gearbox and is connected to the generator to maintain a constant generator AC output regardless of engine RPM
30
Q

Fan/Compressor/Turbine Stages

A
  • Single Stage Fan
  • 4 stage LP Compressor
  • 14 stage HP Compressor
  • 5 stage LP turbine
  • 2 stage HP turbine
31
Q

APU Shutdown sequence

A

APU selector to Off:

  • APU Bleed Valve closes
  • APU runs unloaded for 60 sec cooldown
  • after cooldown APU shuts down
  • complete shutdown assured by waiting 2 mins (Maintains fire detection capability)
32
Q

APU start sources and which is normally used

A
  • APU start transformer rectifier (TR) whenever utility bus 4 is powered (Freighter)
  • APU Battery (normally selected)
33
Q

APU components powered by the APU Battery

A
  • inlet door
  • APU controller (primary)
  • DC fuel pump
  • APU fire detection system
34
Q

APU components powered by the main battery

A
  • APU fire extinguisher
  • APU fuel valve
  • APU controller (alternate)
35
Q

What powers the APU Starter during the battery start sequence?

A
  • the APU battery

- all APU components except the starter are powered by the main battery while the APU starter is engaged

36
Q

What happens if the TR should overheat with the start source in TR?

A
  • starting power is transferred to the battery and the start continued on battery power
  • further start attempts on the overheated TR are inhibited
37
Q

How does a TR failure affect APU starting?

A
  • does not provide automatic switching to the APU battery
38
Q

APU RUNNING displayed

A

APU N1 above 95%

39
Q

APU auto shut down

A
  • fire detected

- limit exceeded

40
Q

Normal Autostart sequence

A

4, #1, #2, #3

CA: Announce “Start engine ___”
FO: Engine START switch………Pull
FO: FUEL CONTROL switch….RUN
CA and FO: verify increase in oil pressure
CA and FO: verify N1 rotation and oil pressure indication by Idle N2 (62-67%)

41
Q

When to call for the ABORTED ENGINE START checklist

A

GE (Autostart)

  • no N1 rotation by idle N2
  • non normal oil pressure by idle N2

GE (Manual start)

  • EGT increases rapidly to start limit (hot start)
  • N2 does not stabilize at idle (hung start)
  • No rise in EGT after 25 sec
  • No N1 rotation by idle N2
  • non normal oil pressure by idle N2
42
Q

Engine Warm Up requirements

A
  • oil temp above bottom of the temp scale

- 3 mins

43
Q

What happens to the auto-throttles when EEC changes to Alternate mode

A

The autothrottles disconnect, but can be reconnected when all EECs have been changed to alternate mode

44
Q

Features provided by EEC in Normal mode

A
  • Thrust limiting
  • Maintains constant thrust, independent of outside air temperature and pressure
  • Compensates for bleed requirements
  • Overspeed protection
45
Q

What causes APU to shutdown immediately?

A
  • A limit is exceeded
  • A fire is detected
  • Battery switch turned off during APU shutdown sequence
46
Q

BB on Engine Vibration Indicator

A

Source is unknown and average vibration displayed

47
Q

Is the EEC required for engine operation

A

YES

48
Q

When are the Igniters commanded ON

A

For each engine:

  • During engine start
  • NAI On
  • flameout detected

For ALL engines:

  • trailing edge flaps are out of up
  • Continuous Ignition ON
49
Q

What happens when CON IGNITION switch is selected ON

A
  • selected igniters operate continuously

- commands approach idle

50
Q

STBY IGNITION selector NORM

A
  • AC power systems supplies selected igniters

- with AC power loss…standby power supplies continuously power to ALL igniters (GE)

51
Q

X-BLD display next to N2

A
  • crossbow air recommended for in-flight start
  • airspeed lower than required for windmilling start
  • displayed in magenta
52
Q

Which two parameters are not monitored by the Autostart system?

A
  • N1 rotation

- oil pressure

53
Q

At what EGT limit does the EEC abort an inflight start though the Autostart system?

A
  • The EEC allows the EGT to increase past the start limit (750º) to the takeoff limit (960ºC) before cutting off fuel
54
Q

How is the engine cooled?

A
  • oil system cools and lubricates the engine bearing and accessory gear box
  • oil cooled through fuel/heat exchanger
  • Oil Sump —> pump —> Gear Box/bearings —> scavenge pump —> heat exchanger —> filter—> return to sump
  • bypass air
55
Q

How are thrust reversers deployed

A
  • pneumatically actuated by bleed air from respective engine
  • interlock mechanism in thrust levers prevent simultaneous movement
  • raising reverse thrust levers allows bleed air to unlock and extend reversers
  • for inadvertent unlocks or deployments bleed air is applied to stow and lock reversers
56
Q

Can you shut down the APU from outside the airplane?

A

Yes

  • APU Ground Control Panel
  • located in the right body gear wheel well
57
Q

Maximum Thrust Reduction using Assumed Temperature Thrust Reduction Takeoff

A

Max 25% reduction

58
Q

Green Thrust Rating and Green line on Primary EICAS

A

Reference N1 (Ref N1)

59
Q

TO-1 and TO-2 derates for B1F and B5F

A

TO-1 :
B1F - 5% derate
B5F - 10% derate

TO-2:
B1F - 15% derate
B5F - 20% derate

60
Q

What should N2 stabilize at after engine start?

A

62% - 67% N2

61
Q

Oil quantity indication turns Magenta

A
  • low oil quantity

- oil differential reached

62
Q

Min duct pressure for engine start?

A

30 PSI

63
Q

What does EEC use for controlling parameter?

A

N1 in both normal and alternate modes

64
Q

How is each EEC powered?

A

Alternator mounted on engine accessory gear box

65
Q

How does EEC determine N1 in alternate mode?

A
  • EEC uses thrust lever position (set by pilot or autothrottle) as commanded N1 and sets thrust accordingly
66
Q

What is Maximum N1

A
  • Maximum rated thrust available from the engine

- continuously computed by EECs

67
Q

When is does EEC automatically switch to Alternate Mode

A

EEC detects a fault and can no longer control the engine in Normal mode

68
Q

What other system is effected if EEC transfers from Normal to Alternate Mode

A
  • autothrottle disconnects

- can be reconnected after all engines are switched to Alternate Mode

Boeing 747 (21 decks)

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