APU

Question 1

What kind of APU do we have and describe it?
A
What kind of APU do we have and describe it?

-Sundstrand APS 2300
-Single-stage impeller with 2 stage axial-flow turbine
-Independent oil system
-Independent AC Generator
-APU bleeds can run AirCon, Water pressurization, cabin pressurization (primarily on ground)
–

2
Q
What controls the APU?

What battery is used for APU Start?
A
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
–

3
Q
What is the fuel source for the APU?
A
What is the fuel source for the APU?

1. Right fuel tank
2. ## X-feed (Low 2)

4
Q
What fuel pump is used to start the APU?
A
What fuel pump is used to start the APU?

1. If no engines on and AC power is avail then ACMP2
2. No AC power then DCMP
3. ## Right Eng ON then right Eng 2 primary ejector pump

5
Q
Will the APU shutdown automatically if speed and
acceleration rate isn’t reached in starting cycle time?
A
Will the APU shutdown automatically if speed and
acceleration rate isn’t reached in starting cycle time?

6
Q
How many different ways can fuel be supplied to the APU?
A
How many different ways can fuel be supplied to the APU?
* DC Fuel Pump (tank 2)
* AC Fuel Pump (tank 2)
* Tank 2 ejector pump
* Tank 1 ejector pump via X-Feed
* Tank 1 AC Fuel Pump via X-Feed
–

7
Q
When does the APU auto shutdown in flight?
A
When does the APU auto shutdown in flight?
1. Overspeed
2. Underspeed
3. FADEC Critical Fault
–

8
Q
When does the APU auto shutdown on the ground?
A
When does the APU auto shutdown on the ground?
1. Overspeed
2. Underspeed
3. FADEC Critical fault
4. High oil temp
5. Low oil pressure
6. Fire
7. Overheat
8. Sensor Failure
–

9
Q
What does selecting the OFF position on the APU selector
do?
A
What does selecting the OFF position on the APU selector
do?

1. removes pneumatics only (only electrics for 1 min)
2. ## Starts 1 min cooldown period

10
Q
When is electrical and pneumatics available from the APU
after APU start?
A
When is electrical and pneumatics available from the APU
after APU start?
95% plus 3 seconds
–

11
Q
Can APU shutdown be canceled?
A
Can APU shutdown be canceled?
Yes, moving the APU start switch back to ON before 1 min
cooldown period is over
–

12
Q
How can the APU be shutdown immediately?
Yes
A
How can the APU be shutdown immediately?
Yes
1. APU EMER STOP is pressed
2. BATTs are turned OFF during 1 min cooldown
–

13
Q
What will happen if batteries are turned OFF during the 1-minute cool down period?
A
What will happen if batteries are turned OFF during the 1-minute cool down period?
The APU will shut down immediately
–

14
Q
Can the APU be started after a critical fault?

Max start EGT for APU Start?

Max EGT for continuous operation?

Max Rotor Speed of the APU?

Max continuous and transient oil temps for the APU?
A
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)
–

15
Q
What are the electrical numbers associated with the APU AC
Generator?
A
What are the electrical numbers associated with the APU AC
Generator?
115 VAC, 400 Hz, 3-Phase, 40 KVA
–

16
Q
Which fuel pump provides fuel supply to APU during engine
start with AC GPU avail, unavail, and after engine start?
A
AC Avail for start = ACMP2
AC Unavail = DCMP
After Engine #2 Start = primary ejector in right integral tank
–

17
Q
Can you restart the APU after receiving a APU Fail EICAS
Message?
A
Can you restart the APU after receiving a APU Fail EICAS
Message?
No; automatic shutdown has occurred;
–

18
Q
APU Bleed Priority
A
APU Bleed Priority
1. A/C on Ground
2. GS below 50 kts for more than 30 secs after touchdown
3. Packs off AND A/I not ALL or Single-Engine Taxi
4. APU normal, APU bleed & x-bleed buttons pushed in (auto)
–

19
Q
What 3 things open or are energized when you move APU
Start Knob to ON?
A
What 3 things open or are energized when you move APU
Start Knob to ON?
1. APU FADEC is energized
2. APU EICAS messages are displayed
3. APU Fuel SOV opens
–

20
Q
What is closed when the APU Emer. Stop Button is pressed?
A
What is closed when the APU Emer. Stop Button is pressed?
1. Denergizes APU FADEC
2. Closed APU Fuel SOV
3. Overrides APU Master Switch
–

21
Q
What powers APU Start Sequence?
A
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)
–

22
Q
What provides the EICAS with APU temp information?
A
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