Flashcards in EMB-120 APU Deck (62):
What occurs when you push the APU STOP button?
• Sends a false 110% rpm overspeed signal to the Electronic Control Unit (ECU).
• This closes the Fuel Control Unit (FCU) SOV and shuts down the APU.
The APU GEN OFF BUS light illuminated means that the APU generator has been disconnected from which bus?
The APU can supply bleed air to which systems?
• Packs (environmental) / Pressurization Vacuum System
• Hydraulic Reservoir pressurization
The APU catches fire while operating in flight. What warning(s) will you receive?
• Fire Bell
• Master Warning
• FIRE APU warning light on MAP
• FIRE light on APU overhead panel
The minimum main battery voltage for APU starts is what?
What does ECU stand for?
Electronic Control Unit
What does FCU stand for?
Fuel Control Unit
Describe the EMB 120 APU
25 SHP gas turbine consisting of a single-stage centrifugal compressor, a reverse flow annular combustor, and single-stage radial turbine.
How is fuel supplied to the APU?
Normally, from the right side of the crossfeed valve.
Left tank may be used with crossfeed valve open.
In regards to starting the APU, when is an electric fuel boost pump used?
APU start (prior to engine start). In flight, with right engine shutdown.
What two fuel conditions must be met to start the APU?
1) Airframe SOV open
2) FCU SOV open
What component controls the fuel flow to the APU?
FCU- Fuel Control Unit
What are the fuel valves that regulate fuel flow to the APU and where are they located?
Airframe fuel shutoff valve- prior to the stainless steel firewall.
FCU shutoff valve- between the fuel control unit and fuel nozzle.
When starting the APU in flight, what position does the fuel boost pump need to be in?
Once started, what provides pressurized fuel to the APU?
Motive flow when the right engine is running or an electric boost pump is required when only the left engine is running.
How much fuel does the APU burn?
130 pound per hour.
Which fuel valve does the APU master switch open and close?
Airframe fuel valve.
What are the recommended and required voltage for starting the APU?
24 volts recommended
22 volts minimum
What busses do you need to start the APU?
Central Bus and DC Bus 2.
What powers the APU start contactor?
DC Bus 2
Can you start the APU in electrical emergency mode?
No, the start relay is on DC Bus 2.
What powers the APU once it has been started?
It uses its own DC generator.
How is the APU starter/generator different from the main gens?
It doesn't become a generator until 95% Nh.
What component governs the APU?
ECU- Electronic Control Unit.
What are the limitations for starting the APU in flight?
Up to 20,000’ between 135 to 200 KIAS.
What are the operational limitations of the APU?
Max Operating Temps:
Max Start EGT:
Up to ISA + 35°C:
≤ 16,000 ft 400A
> 16,000 ft 290A
Greater than ISA + 35°C:
≤ 15,000 ft 400A
> 15,000 ft 280A
Up to 16,000’ ISA + 38˚C
Above 16,000’ ISA + 35˚C
Max start EGT 90% 732°C
-1,000 to 20,000 ft
135 to 200 KIAS
What are the max amps for the APU Gen with ISA + 27 and FL 270?
What are the starter limitations for the APU?
o 1st Attempt: 30 sec ON: 3 min OFF
o 2nd Attempt: 30 sec ON: 3 min OFF
o 3rd Attempt: 30 sec ON: 3 min OFF
o 4th Attempt: 30 sec ON: 30 min OFF
When does the APU automatically shutdown in flight?
o Generator overvoltage
When is the APU start contact engaged?
0% to 50%
What is the max EGT for the APU?
What is the max EGT on start for the APU?
Where is the APU located?
The unit is located in the tail and isolated by a stainless steel firewall.
What does the STOP button do to the APU?
Sends a false electronic 110% rpm overspeed signal to the ECU which will close the FCU SOV and shut down the APU.
Prior to APU start, what do you always need to do?
Arm backup battery and do a fire test.
Upon starting the APU, after the master switch is turned on, what are the light indications?
o APU control panel lights come ON momentarily, then:
o Fuel LOW PRESS light OFF
o Fuel CLOSED light OFF
o APU light on MAP FLASHING
During APU start, when do you shut down the APU?
o When white START CONTACTOR light does not extinguish at 50% rpm
o Any other malfunction
What are the light indications when the APU Master switch is turned to START?
o START CONTACTOR light ON, then release APU Master switch
o At 50% rpm START CONTACTOR light OFF
o At 100% rpm oil LOW PRESS light OFF
After 28.5 V is indicated on the voltammeter and the APU GEN switch is turned ON, what lights extinguish?
o APU GEN OFF BUS light OFF
o APU light on MAP OFF
What does the APU GEN OFF BUS light mean?
APU gen has been disconnected from the central bus.
The APU power shaft connects to a gearbox and powers what components?
o Oil pump
o Starter generator
Can APU and engine bleed air supply the same air conditioning pack?
No, priority is given to the engine.
Where does the APU send its bleed air?
To the left side of the crossbleed valve.
What happens to the APU if you turn the engine bleed ON?
It will close the APU bleed valve.
In regard to the APU, what is important to remember about de-icing?
Do not use the APU for air conditioning immediately after de-icing as you may ingest smoke into the cabin.
What happens when the APU SHUTOFF/EXTINGUISH switch is moved to CLOSE?
o APU generator- trips off line (opens the relay)
o APU bleed SOV- close
o Airframe fuel SOV- close
o FCU fuel SOV- close
How is fire protection provided on the APU?
A halon bottle provides fire protection.
How do you know if the APU Halon bottle is full or empty?
INOP light on the APU fire panel.
What happens to the APU with a fire on the ground?
Automatically shuts down.
What warnings will you receive is the APU catches fire in flight?
o Master warning
o Fire bell
o FIRE light on APU
o FIRE APU light on MAP
What’s the first thing to be done with an APU fire on the ramp?
QRC APU FIRE
What is the indication when the airframe fuel valve is closed on the APU?
White CLOSED light is on.
What is the indication that the FCU valve is closed on the APU?
Why wait 3 minutes to open the APU bleed?
To prevent wear on APU turbine.
Once the APU has been shut down and the APU master switch has been turned off, do not turn the master switch back on for at least:
Once the APU has been shut down and the APU master switch has been turned off, do not turn the master switch back on for at least one minute; otherwise, a stack fire may result.
If the fire TEST button is held for more than _____ seconds with the APU running, the APU will:
If the fire TEST button is held for more than 10 seconds with the APU running, the APU will automatically shutdown.
Power for APU starting comes from:
The APU requires power from the central and DC2 buses for starting, but once started, uses its own generator for internal electrical power.
Talk about APU start sequence:
1. Click APU Master switch- ON. Power to the panel. Airframe fuel valve open.
2. CLICK to initiate start up to 50%. Starter engaged to 50%. FCU fuel valve open at 10%. Ignition applied at 10%.
3. Finish start sequence. Generator on line at 95%. Ignition terminated at 95%.
How many fuel valves are in the APU fuel system?
2: Airframe and FCU
When the master switch is initially positioned to ON, the panel receives power and:
The airframe fuel valve opens.
After a normal APU shut down the _____ & _____ captions remain illuminated for 10 sec.
FUEL SHUTOFF - CLOSED and, APU bleed valve shutoff CLOSED.