"APU Practice test" Flashcards
Describe the start/on-speed sequence. (indication, time limits, etc)
- START light (4) goes out at 35 percent RPM.
- ON SPEED light (3) comes on within 35 seconds after START light comes on.
- ON SPEED light (3) comes on at 95 percent RPM and stays on.
- Tachometer (1) indicates 100 ( 2) percent RPM.
- EGT indicator (2) does not exceed 620oC.
What is the normal rpm operating limits?
TACH 100+-2% RPM
At what RPM does the APU overspeed?
110% RPM
What are the limitations of the APU generator?
115+-3V & 400+-20Hz
What is the bleed down limitations?
83-0486< 8.5 seconds. 30 to 15.
83-0486 and > 16 seconds.
What switches need to be actuated to accomplish the bleed down?
APU BA Valve BA SW to open/on. wait till is gets up to at least 35PSI and put sw to CLOSED/OFF.
What are the EGT limitations?
620 degrees celcius
What should you do before applying bleed air to the manifold?
Make sure the props are clear.
What tank supplies fuel to the APU?
2
What is the required fuel capacity? If it is below the required capacity, can the APU still be started? If so, what mustbe done?
2 - 2,000 lbs. if below 2,000 lbs turn boost pump on.
What is the capacity of the oil tank?
4 quarts
What is the capacity of the oil tank and system?
6 quarts
How often should you check the fuel SOV? What indicates a bad SOV?
first APU start of the day. Its bad if fuel steadly flows after the ops chk.
What is the primary purpose of the APU?
supplies BA for starting engines, operation of other BA systems & mechanically drives an AC GEN.
At what PSI does the APU door close?
20PSI
Can you operate the APU with a failed inlet door?
Yes. You need to reposition the door actuator (if running apu on ground). It is not recommended in flight.
What AC bus does the APU GEN power?
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When starting the APU using battery power, what battery voltage is required?
21V
When starting the APU using battery power, when should you turn on the APU GEN?
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Where is the oil tank located (approximate)?
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what is the starter duty cycle?
1 minute on and 4 minutes off
Assuming the APU hasn’t reached 35% RPM, what is the time limit before you must stop the APU?
1 minute
Can the A/C fly without the APU power?
YES.
When using external electrical power, is it required to turn the APU GEN on?
NO. once in flight if the APU is turned on it becomed the emergency generatore and will take over the essential bus.
If you put the APU to stop and it doesn’t stop, what should you do?
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Can you radio tower from the FE position?
YES. (275.8 UHF)
What is the Ground frequency for LRAFB?
275.8 UHF
What bus powers the APU?
isolated DC bus
What percent does the APU door open to on the ground?
35 degrees
What percent does the APU door open in flight?
15 degrees
What is LRAFB ground frequecy? UHF or VHF?
UHF 275.8
Placing the APU cntrl switch to stop is a functional check of what protections component?
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What is the purpose of tying the DC bus for APU operations?
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What does the acronymn stand for?
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How do you shutdown the APU if placing the APU control SW to stop does not work?
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What are the real names for the APU components commonly called “salt and pepper shakers”
ignition circuit relay
