View Full Version : A320 T/O - PACKS ON APU but APU then fails
Not my area of expertise - I'm pooped from chasing around the FCOM but a student asked an instructor who turned to me and I can't definitively answer him
Question
If packs are on APU bleed during take-off and APU fails will the engine bleeds automatically kick in. I suspect not but can't be certain and then there is a restriction on using APU bleed during a contaminated t/o that is nagging me and causing me to think I might be wrong.
Can anybody please dear god put me out of my misery.
Mephistopheles
28th Nov 2007, 08:46
I know that on the 330/340 in the case of an APU bleed failing/or an auto shutdown during t/o the packs will go onto to the engine bleeds giving an increase in the EGTs in order to maintain the currnet EPR/N1. I guess the 320 should be the same.
There is no restriction on using APU on a contaminated r/w except if you are going to use the wing anti-ice after lift off. Wing A.I with APU bleed not allowed.
Tail-take-off
28th Nov 2007, 08:55
From FCOM 1.36.20 (pneumatic, controls & indications, overhead panel)
ENG 1 and ENG
2 BLEED pb sw
ON:
Bleed valve opens if :
Upstream pressure is above 8 psi.
APU BLEED pushbutton switch is off or APU bleed valve is closed.
There is no onside wing or pylon leak, and no overpressure or overtemperature has been detected
The ENG FIRE pushbutton has not been popped out.
In your scenario the APU bleed Pb is not off therefore the engine bleed valve will not open.
Hope this helps!
TTO
Swedish Steve
28th Nov 2007, 09:19
Depends how you configure the bleed panel for take off.
If you leave the engine bleed PB in, the APU running, and APU bleed on, then when the APU fails, the APU bleed valve will close and the engine bleeds will open.
But if you switch off the engine bleeds (PB out) then the engine bleed valves will stay closed until you select them on.
spannersatcx
28th Nov 2007, 10:27
In your scenario the APU bleed Pb is not off therefore the engine bleed valve will not open.
Yes but the apu bleed valve will be closed.
APU BLEED pushbutton switch is off or APU bleed valve is closed
Tail-take-off
28th Nov 2007, 12:40
spannersatcx
You are absolutely right - I stand corrected.