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EMB 145-APU

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What kind of APU do we have?
-Sundstrand t-62 Auxillary Power Unit.
-It is a constant-speed gas turbine engine.
How many Shaft HP does it have?
95
How is APU isolated?
by a titanium firewall.
What is APU for?
for pneumatic and electrical power on ground and in flight.
How is APU controlled?
by a FADEC
What is APU control system powered by?
-ESS DC BUS 2 and the Central DC Bus as the secondary source.
-modifications are switching to HOT BUS 1 to improve APU starting conditions.
Will APU shut down if all generators and batteries are turned off?
yes.
What on the APU supplies electrical power?
The Starter-Generator (SG) 28V 400 Amps
How is SG protected?
by it's own GCU
What network does SG work parallel with?
the right network with DC BUS 2 Generators.
What button controls SG?
the APU GEN button.
When is the SG available to supply electrical power to the system?
at 95% RPM plus 7 seconds.
If it doesn't what message will you get?
EICAS 'APU GEN OFF BUS' caution.
How sources can start APU?
-External power
-Battery 2
-Battery 2 assisted by a main generator.
Why cannot Battery 1 be used for an APU start?
Because it is segregated from the load busses during the start in order to provide stable electrical power to to transient sensitive equipment.
How do we Normal Shutdown?
Press the APU STOP button
What does this do?
It sends stop request signal to FADEC.
What will cause automatic 'abnormal' shutdown of APU in flight?
-Overspeed
-Underspeed
-Loss of speed data
-Failure to start, accelerate, or light
-External short
-FADEC failure or loss of FADEC signal
*A LOSS OF CRITICAL CONTROL INPUTS OR FAILURE TO START.
What will cause automatic 'abnormal' shutdown of APU on ground?
-Overspeed
-Underspeed
-Loss of speed data
-Failure to start, accelerate, or light
-External short
-FADEC failure or loss of FADEC signal
*A LOSS OF CRITICAL CONTROL INPUTS OR FAILURE TO START.
-High Oil Temp
-EGT overtemp
-Loss of EGT
-Low Oil pressure
-Oil pressure switch short
-Fire
*On ground- exceeding operating limits or fire.
What fuel tank normally supplies APU?
the right wing tank.
Can the left wing tank be used?
yes. by opening the crossfeed valve.
When will APU fuel shut-off valve close?
-APU master knob is OFF
-APU FUEL SHUTOFF button is pressed
-APU EXTG Button is pressed
-An APU FIRE aural warning of 10 seconds or more while on the ground.
What will cause an eicas APU OIL HI TEMP caution message?
oil temp exceeds 166 degrees C
How is operation of the APU Bleed Valve (ABV) commanded?
by On/Off switch on overhead panel.
Does engine bleed air OR APU bleed air have priority?
Engine bleed. ABV is ELECTRICALLY closed if engine bleed source is detected.
Can APU bleed air be used for anti-icing?
No. due to its insufficient thermal capacity.
How is APU compartment cooled?
by air drawn in through air inlet on lower right side of the tail cone through the oil cooler by low pressure.
After APU shutdown how is it cooled?
by convection.
How is SG cooled?
by a fan that draws air through a NACA air inlet on the lower left side of the tail cone.
Will APU start with ABV open?
no
If AH-900 AHRS is not initialized what message should we wait for before starting the APU?
AHRS 1 (2) ALN
Why?
to prevent AHRS alignment faults and failures.
How is APU starting cycle initiated?
by moving the APU master Knob to ON.
What does EGT need to read before moving to START?
dashes disappear after 3 seconds and EGT value is shown.
Why is 3 seconds required?
for FADEC to power-up and self test.
When does FADEC de-energize the starter?
above 50% RPM
What happens at 70% RPM?
the FADEC de-energies the ignition exciter.
What is normal operating RPM range?
96-104% RPM
If EGT does not rise during the starting process when will FAFDEC execute a swing start?
The starter is de-energized at 20% and re-energized at 5% RPM
If the EGT does not rise during restart what happens?
APU Fails and automatically shuts down.
During the APU start when is fuel and ignition introduced?
3% on the ground 0% in flight.
What does turning the APU master knob to OFF do?
-De-energizes the FADEC
-Closes APU fuel SOV
-Turns off indications and alarms when RPM is below 10%
-Commands APU to shutdown.
What does turning the APU master knob to ON do?
-Energizes the FADEC
-Commands the APU fuel shut-ogg valve to open
-Enables EICAS indications and alarms
-Allows the APU to keep running after start
How long may APU master knob be held in START position?
Up to 55% RPM
Are APU EICAS indications operational after pressing APU Stop Button?
yes
What happens when pressing APU Fuel Shut-Off button (guarded)?
-Sends a stop request to the FADEC
-Closes the APU fuel shut-off valve
-A lighted bar illuminates inside the button to indicate that is is pressed.
Where is APU Fuel Shut-off valve located?
the wing root.
What does APU EXTG switch when pressed do?
-Sends a stop request to the FADEC
-Closes the APU fuel shut-off valve
-Discharges the APU fire-extinguisher bottle into the compartment.
What are the 3 APU procedures on the EPC?
-APU fire
-APU bleed leak
-APU EGT over temperature.
How long should we wait after every APU start attempt before opening the ABV?
3 minutes
How long can APU be left running unattended?
30 minutes max.
What is APU operation altitutde limit?
37,000 ft
What is APU max start altitude?
30,000 ft
What is max start EGT?
884 degrees C
What is max continuos EGT?
680 degrees C
-may be exceeded up to 717 degrees C for 5 minutes max.
What is max rotor speed?
104% RPM
What is Min start temp?
-54 degrees C
What is minimum battery temp for APU start?
20 degrees C
What are the APU starter cycle limits for the first two cycles?
1 minute OFF
What are the APU starter cycle limits for the 3rd cycle?
30 minutes
How many series attempts are allowed?
2
Is the American Eagle APU Start Policy for normal operations, to wait and start the APU at the gate only?
yes
If batteries are OFF when shutting down the APU, what should we do?
cycle the battery switches to AUTO and monitor to ensure the APU decelerates to 0% before turning BATT 1 &2 back to OFF.
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