Engines, APU Flashcards
Engine Start switch (GRD)
GRD:
-opens start valve
- closes engine bleed valve
- for ground starts, arms selected igniter to provide ignition when start lever is moved to idle
- ‘for air starts, arms both igniters to provide ignition when start lever is moved to idle
will release to OFF or AUTO at start valve cutout
Engine Start Switch (OFF)
- ignition is normally off
- igniters activated when engine start lever is IDLE and:
- uncommanded rapid decrease in N2
- N2 between 57% and 50%
- in flight- N2 between idle and 5%
Engine start switch (AUTO)
-ignition normally off
- both igniters activated when start lever IDLE and:
- an uncommanded rapid decrease in N2
- N2 between 57% and 50%
- in flight N2 between idle and 5%
Provides automatic ignition to selected igniter when:
- engine is running AND
- flaps not up below 18000
- engine anti ice ON
Engine Start Switch (CONT)
provides ignition to selected igniters when engine is operating and start lever is IDLE
-in flight-
provides ignition to both igniters when N2 is below idle and engine start lever is in IDLE
ENgine start switch (FLT)
-ignition to both igniters with engine start lever in IDLE
REVERSER lights (amber) when one or more of following
- isolation valve or thrust reverser control valve not in commanded position
- one or more thrust reverse sleeves not in commanded state
- auto restow circuit activated
- failure detected in synchronization shaft circuitry
Engine Control Lights (amber) and when does it operate
Engine control system not dispatchable due to faults in system
OPerates when:
- engine is operating AND
- airplane on ground AND
– below 80 knot on takeoff or 30 seconds after touchdown
Reverse thrust lever is blocked at reverse idle position until related reverser is more than ___% deployed
60%
Engine start lever
IDLE:
- energizes ignition system thru EEC
- electrically opens Spar fuel SOV in wing leading edge
- opens engine mounted fuel SOV via EEC
- CUTOFF:
- closes spar and engine SOV
- de-energizes ignition system
APU MAINT light (blue)
APU mx problem exists but APU may be operated. Light is disarmed with APU switch OFF
APU OVERSPEED light (Amber)
- APU RPM limit has been exceed, resulting in automatic shutdown
- overspeed shutdown protection feature has failed self test during normal APU shutdown
- light disarmed with APU switch OFF
APU FAULT light (amber)
- malfunction exists causing APU automatic shutdown
- disarmed with APU switch off
APU low oil pressure light (Amber)
- normal during start until pressure is normal)
- oil pressure is low causing auto shutdown
- disarmed light when APU switch is OFF
N1 rotor of the engine consists of
a fan, a low pressure compressor and a low pressure turbine
The N2 rotor of the engine consists of
a high pressure compressor and high pressure turbine
What are the primary engine indications?
N1 and EGT
what are the secondary engine indications?
N2, fuel flow, oil pressure, oil temp, oil qty, engine vibrations
when are the secondary engine indications automatically displayed?
- when the displays initially receive power
- in flight when engine start lever is moved to CUTOFF
- in flight when engine N2 RPM is below idle
- secondary engine parameter exceeded
when does the EEC become powered?
when the engine accelerates to a speed greater than 15% N2
When will the ENG FAIL display amber on EGT indicator?
when respective engine is operating at condition below sustainable idle (50% N2) with engine start lever at idle
What does the EEC do?
It uses sensed flight conditions and bleed air demand to calculate N1 thrust ratings. Compares commanded N1 to actual N1 and adjusts fuel flow to achieve it
EECs have two alternate modes what are they?
Soft alternate or Hard alternate
IF the EEC is in soft alternate mode, what will happen?
the ALTN switch will illuminate but the ON indication remains.
-the EEC will use the last valid flight conditions to define engine parameters BUT shortfalls or exceedances can occur.
When will the EEC go to hard alternate mode?
either retarding the thrust lever to idle or manually selecting ALTN with EEC switch
what happens in EEC hard alternate mode?
the EEC reverts to the alternate mode thrust schedule. The thrust will always be equal to or greater than normal mode thrust for the same lever position
is thrust protection provided in alternate mode?
No, max rated thrust is reached at thrust lever position less than full forward
EEC has 3 idle modes. what are they and when are they selected?
ground minimum idle- ground operations
flight minimum idle- flight operations during most phases
approach idle- flaps in landing config or engine anti ice on for either engine
what is the difference between flight min idle and approach idle?
N1 and N2 RPM will be higher in approach idle
If a fault prevents the EEC from receiving flap or Anti-ice signals, when will approach idle schedule begin?
below 15,000 MSL
If a fault prevents the EEC from receiving flap or Anti-ice signals, when will approach idle schedule begin?
below 15,000 MSL
Engine start sequence
- engine start switch uses battery power to close engine bleed air valve and open start valve
- when start valve opens, amber START VALVE open alert is provided
- start rotates N2 compressor and at 25%, move the engine start lever to IDLE to open fuel valves and EEC supplies FUEL and Ignition
- Starter cutout is 56% N2 and power is removed from start switch and the switch goes to OFF and engine bleed air valve returns to selected position and start valve closes
If EEC detects impending hot start by rapid rise in EGT or EGT approaching start limit, what happens to the white box surrounding EGT readout?
the white box flashes white
what will EEC do to ignition and fuel if it detects impending hot start or stall?
it will turn them off automatically
What will the EEC do if EGT exceeds the starting limit?
EGT display turn red and EEC will turn off ignition and shut off fuel to engine
What is a wet start?
when EGT doesn’t rise when start lever is moved to IDLE. if detected, the EEC will turn off ignition and shut off fuel 15 seconds after start lever is moved to idle
What powers each igniter?
LEFT- associated AC transfer bus
RIght- AC standby bus
the reverser light (amber) illuminates when the thrust reverser is commanded to stow and extinguishes 10 seconds later when isolation valve closes. if it illuminates for more than __ seconds, a malfunction has occured
12 seconds
what inhibits motion to the reversers until extension is selected?
electro-mechanical lock and hydraulically operated locking actuator
what is the auto-restow circuit in the reversers?
compares the actual reverser sleeve position and commanded position. in the event of incomplete stowage or uncommanded movement, the auto-restow circuit opens the isolation valve and commands the control valve to stow
fuel to start and operate APU comes from which side of fuel manifold?
Left
what is the APU start sequence when you move the APU switch to START?
- APU inlet door opens
- At proper speed, ignition and fuel will be provided
- When ready to accept bleed air or electric load, the APU GEN OFF BUS light illuminates
What happens if APU doesnt reach proper speed within time limit of starter?
it will terminate start cycle
how long should you operate APU before using it as a bleed air source?
2 minutes to extend service life of APU
An electronic control unit (ECU) monitors and controls APU. It will shutdown APU for:
- overspeed conditions
- Low oil pressure
- high oil temp
- APU fire
- fuel control unit failure
- EGT exceedance
- other faults
