APU Flashcards
What kind of APU do we have and describe it?
Sundstrand 2300, single-stage impeller with 2 stage axial-flow turbines
- Independent oil system
- Independent AC Generator
- APU bleeds can run AirCon, Water pressurization, cabin pressurization (primarily on ground)
When does the APU auto shutdown in flight?
- Overspeed
- Underspeed
- Critical Fault
When does the APU auto shutdown on the ground?
- Overspeed
- Underspeed
- Critical fault
- High oil temp
- Low oil pressure
- Fire
- Overheat
- Sensor Failure
What does selecting the OFF position on the APU selector do?
- removes pneumatics only (only electrics for 1 min)
2. Starts 1 min cooldown period
When is electrical and pneumatics available from the APU after APU start?
95% plus 3 seconds
What controls the APU?
Its dedicated dual channel FADEC
What battery is used for APU Start?
BATTs 1 (FADEC & EICAS) and 2 (APU Start Bus)
or
BATTs 1 and DC GPU
What is the fuel source for the APU?
- Right fuel tank
2. X-feed (Low 2)
What fuel pump is used to start the APU?
- If no engines on and AC power is avail then ACMP2
- No AC power then DCMP
- Right Eng ON then right Eng 2 primary ejector pump
Will the APU shutdown automatically if speed and acceleration rate isn’t reached in starting cycle time?
Yes
Can APU shutdown be cancelled?
Yes, moving the APU start switch back to ON before 1 min cooldown period is over
How can the APU be shutdown immediately?
- APU EMER STOP is pressed
2. BATTs are turned OFF during 1 min cooldown
Can the APU be started after a critical fault?
No
Max start EGT for APU Start?
1032˚ C
Max EGT for continuous operation?
717˚ C is start of the Red; amber is permitted 662˚ - 717˚
Max Rotor Speed of the APU?
108%
Max continuous and transient oil temps for the APU?
155˚ C and 163˚ C (up to 15 mins)
What are the electrical numbers associated with the APU AC Generator?
115 VAC, 400 Hz, 3-Phase, 40 KVA
Which fuel pump provides fuel supply to APU during engine start with AC GPU avail, unavail, and after engine start?
AC Avail for start = ACMP2
AC Unavail = DCMP
After Engine #2 Start = primary ejector in right integral tank
Can you restart the APU after receiving a APU Fail EICAS Message?
No; automatic shutdown has occurred;
APU Bleed Priority
- A/C on Ground
- GS below 50 kts for more than 30 secs after touchdown
- Packs off AND A/I not ALL or Single-Engine Taxi
- APU normal, APU bleed & x-bleed buttons pushed in (auto)
What 3 things open or are energized when you move APU Start Knob to ON?
- APU FADEC is energized
- APU EICAS messages are displayed
- APU Fuel SOV opens
What is closed when the APU Emer. Stop Button is pressed?
- Denergizes APU FADEC
- Closed APU Fuel SOV
- Overrides APU Master Switch
How many duplex and simplex fuel injectors are used in the APU Fuel Distribution?
6 Simplex (APU Run) from secondary fuel manifold; 6 Duplex (APU Run and Start) from primary and secondary fue manifolds
How many igniters and exciters for the APU?
1 exciter, 2 gap-type igniter plugs
What powers APU Start Sequence?
Batt 1 FADEC, Batt 2 APU Start Bus which powers Electronic Starter Controller –> Brushless Starter Generator (attached to rotor shaft for APU Start, basically electronic version of Air Turbine Starter)
What provides the EICAS with APU temp information?
2 thermocouples located in the exhaust section of the APU that are dangling in front of outgoing exhaust air
