auxiliary power unit Flashcards

1
Q

what kind of APU does the 175 have?

A

Sundstrand APS 2300

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the APU

A

constant speed
single stage impeller with 2 stage axial flow turbine
independent oil system
provides pneumatic and electrical AC power

pneumatic power is used for engine starting and to supply bleed air to the AC packs of the ECS

electrical generator supplies 115 V kVA to the electrical system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what controls the APU?

A

a dedicated FADEC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what battery is used for the APU start?

A

Batt 2 powers the starter
Batt 1 powers the FADEC and EICAS for monitoring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the fuel source for the APU?

A

with only DC power, the DC fuel pump in the right fuel tank.

if AC power is avaliable and engine is not running then provided by AC fuel pump.

engine running - ejector fuel pump provides fuel to the APU from right wing tank

also possible:
left fuel tank thru the crossfeed valve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what fuel pump is used for APU start?

A

batteries ‘ON’ only DC fuel pump in right tank
AC powered airplane ACMP 2
right engine running ejector fuel pump

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

will the APU shut down automatically if speed and acceleration rate isn’t reached in starting cycle time?

A

YES

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does moving the APU start switch to OFF do?

A

initiates normal APU shutdown
1 minute cool down
no pneumatics (electrics only for 1 minute)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Can the APU shut down be cancelled?

A

yes, by moving the start switch back to ON before the 1 minute cool down is over

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how is the APU shut down immediately?

A

APU emergency stop button
no 1 minute cool down period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what will happens if batteries are turned off during the 1 minute cool down period?

A

APU will shut down immediately

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

when does APU shut down automatically occur?

A

on ground:
overspeed
underspeed
fadec critical fault
sensor failure
high oil temp
EGT over temp
low oil pressure
fire
in flight:
overspeed
underspeed
fadec critical fault

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

can the APU be started after critical fault?

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly