Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

A320 exhaust smell in cabin area

Tech Log The very best in practical technical discussion on the web

A320 exhaust smell in cabin area

Old 20th Jun 2015, 03:58
  #1 (permalink)  
Thread Starter
 
Join Date: Jun 2015
Location: ksa
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Smile A320 exhaust smell in cabin area

Hi guys ,


I have question & I hope to found answer

during engine start , there are exhaust smell coming in aft of the cabin area
with engine start only ,
what is this ? and this is normal ?


Thanks
alawax is offline  
Old 20th Jun 2015, 08:27
  #2 (permalink)  
 
Join Date: Jul 2007
Location: uk
Posts: 778
Received 0 Likes on 0 Posts
Sounds like re-ingestion of engine exhaust fumes via the APU inlet if starting in a strong tailwind. Can happen if Packs are supplied by APU for a long period after engine start.
Meikleour is offline  
Old 20th Jun 2015, 08:51
  #3 (permalink)  
 
Join Date: Mar 2012
Location: Having a margarita on the beach
Posts: 2,430
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by alawax
Hi guys ,


I have question & I hope to found answer

during engine start , there are exhaust smell coming in aft of the cabin area
with engine start only ,
what is this ? and this is normal ?


Thanks
APU exhaust ingestion with tail or crosswinds. A few years back there was an OEB instructing to start the upwind engine first to avoid excessive engine exhaust gas ingestion from the APU with old ECB standard.
sonicbum is offline  
Old 20th Jun 2015, 09:05
  #4 (permalink)  
SW1
 
Join Date: Apr 2008
Location: Victoria
Posts: 468
Likes: 0
Received 0 Likes on 0 Posts
When pushing back and having a direct tailwind from behind the engines can cause that smell as previously mentioned.

Ive found setting the extract push button to override- closing the avionics inlet and extract valves- once the smell is first perceived eliminates this problem. In the cockpit at least. Not sure if it elimintes the smell from the cabin.

After second engine start. PF does normal flow and sets the override push button back to normal. Inform the other guy as well before you do this so neither of you forget!
SW1 is offline  
Old 20th Jun 2015, 09:24
  #5 (permalink)  
 
Join Date: Nov 2006
Location: Tropics
Posts: 360
Likes: 0
Received 0 Likes on 0 Posts
If I understand the replies correctly, due to the tailwind the APU ingests its own exhaust gas and hence the smell. But why does it only happen during engine start? Surely sitting at the gate with the tailwind and the APU bleed being the source of air for the packs, we should be smelling it consistently?

What am I missing here?
dream747 is offline  
Old 20th Jun 2015, 19:45
  #6 (permalink)  
 
Join Date: Jan 2011
Location: Seattle
Posts: 719
Likes: 0
Received 3 Likes on 2 Posts
What am I missing here?
Possibly the exhaust velocity. Once the engines (or APU) are up and running, the exhaust velocity is sufficient to push the vapors far beyond the aircraft in all but severe tail/crosswinds.
EEngr is offline  
Old 23rd Jun 2015, 12:21
  #7 (permalink)  
 
Join Date: Nov 1999
Location: UK
Posts: 2,525
Received 127 Likes on 81 Posts
The smell is caused by the APU ingesting the engine's exhaust gases, not its own.

Hence why this only happens during main engine start and with certain winds from behind - if you'll pardon the expression !!

After the engines are started, the aircon packs are fed from the engine bleeds instead - which are "clean" - and the APU is shut down, so the problem goes away.
Uplinker is offline  
Old 24th Jun 2015, 01:28
  #8 (permalink)  
Thread Starter
 
Join Date: Jun 2015
Location: ksa
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Thanks guys ,


as your replay , it's APU ingesting the engine's exhaust gases .
but , it's coming ONLY with Engine start within few seconds everything back to normal .
no strong tailwind & crosswinds


this happens it's come always with Engine start only
alawax is offline  
Old 25th Jun 2015, 07:07
  #9 (permalink)  
 
Join Date: Jan 2014
Location: N5109.2W10.5
Posts: 720
Likes: 0
Received 0 Likes on 0 Posts
Hi alawax,

I agree with SW1's diagnosis in post #4.

During the first automatic engine start attempt, only 1 igniter is supplied, but fuel is being supplied to every combustor. It takes some time for the flame to propagate around to all the combustors. During that time, the fuel that has not been ignited, is exhausted into the atmosphere as vaporised fuel and is very smelly.

As you push back into the smelly air, the Avionics Ventilation system Blower fan sucks the air in and blows it around the avionics equipment bay. Hence you get to smell it first.

see FCOM DSC-21-30-20 Avionics Ventilation, Normal Operation, Open-Circuit Configuration.
Goldenrivett is offline  
Old 25th Jun 2015, 14:09
  #10 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 4,569
Likes: 0
Received 1 Like on 1 Post
It takes some time for the flame to propagate around to all the combustors
about the time that a whoom sound makes under spin-spark and spray
lomapaseo is offline  
Old 25th Jun 2015, 20:39
  #11 (permalink)  
Thread Starter
 
Join Date: Jun 2015
Location: ksa
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
I will try next flight thankx
alawax is offline  
Old 26th Jun 2015, 08:26
  #12 (permalink)  
 
Join Date: Jan 2014
Location: N5109.2W10.5
Posts: 720
Likes: 0
Received 0 Likes on 0 Posts
Hi lomapaseo
whoom sound
Ok. More accurately, the unburned fuel due to poor air flow at very low engine RPM.

see Page 4: http://www.air.flyingway.com/books/e...aintenance.pdf

"When an engine is started.....gases in the exhaust that smell bad and can cause injury or irritation to your eyes and lungs."
Goldenrivett is offline  
Old 26th Jun 2015, 09:02
  #13 (permalink)  
 
Join Date: May 2006
Location: FL510
Posts: 910
Received 0 Likes on 0 Posts
I think it's not ingested via the APU, the packs are off during engine start anyway. I think it's the avionic venting which is dragging in the fumes.
safelife is offline  
Old 27th Jun 2015, 19:18
  #14 (permalink)  
 
Join Date: Apr 1999
Location: Manchester, UK
Posts: 1,958
Likes: 0
Received 0 Likes on 0 Posts
Sorry guys, need to back up a little. Why would THE APU ingesting exhaust gases, whether it's own or the engine's, cause odour/contamination of cabin air??
ShotOne is offline  
Old 21st Jul 2015, 15:14
  #15 (permalink)  
Beau_Peep
 
Join Date: Apr 2007
Location: India
Posts: 228
Likes: 0
Received 0 Likes on 0 Posts
It doesn't happen all the time.

Here is the what FCOM, NORMAL PROCEDURE, SOP - SECURING THE AIRCRAFT says:

"wait until the APU flap is fully closed (about 2 min after the APU AVAIL light goes out), before switching off the batteries. Switching the batteries off before the APU flap is closed may cause smoke in the cabin during the next flight"
IFLY_INDIGO is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.