Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Airbus Air Conditioning During T/O  
User currently offlineVs744 From United Kingdom, joined Aug 2001, 677 posts, RR: 1
Posted (6 years 5 months 1 week 4 days 16 hours ago) and read 4965 times:

I fly a lot on Virgin's A346 and have noticed on the last few flights that they turn the air conditioning off just before take off and it is not until you are well clear of the airfield that it comes back on (the process is very similar to what happens during engine start up). I've also noticed this on an alitalia A321, but not on the A319, 320 etc....

Does anyone know if this has always happened, or whether it was recently introduced and for what reason? I would take a guess at is being something to do with power but not sure whether it always happened or I only recently noticed it.

thanks!

30 replies: All unread, showing first 25:
 
User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 1, posted (6 years 5 months 1 week 4 days 14 hours ago) and read 4935 times:

We have started to this as a regular procedure on our (SAS) A330 and A340 recently. We shut off both AC packs before entering the runway and turn them on again after climb thrust has been set and with a minimum of ten seconds between each pack. We save some fuel and reduce maintenance costs on the engines. On some of our RR Trent engines with more than 2000 cycles, it is not recommended to shut off the packs at runway elevations higher than 600 feet.


"Luck and superstition wins all the time"!
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9378 posts, RR: 52
Reply 2, posted (6 years 5 months 1 week 4 days 12 hours ago) and read 4919 times:

Shutting them off during takeoff can increase performance. It isn't a huge difference, but by decreasing the load on the engine from running the cabin systems, there is more power for takeoff. Each airline has its own set of criteria, but it doesn't have to be done.


If you have never designed an airplane part before, let the real designers do the work!
User currently offlineTom775257 From United Kingdom, joined Dec 2000, 153 posts, RR: 0
Reply 3, posted (6 years 5 months 1 week 4 days 11 hours ago) and read 4899 times:

Or just leave the APU and APU bleed on then you can leave both packs on.

On the A320 series if we take off packs off, our SOPs are 1 pack on at thrust reduction (1500'AAL) and then the second pack on at flaps zero. I've no idea about the A330/340.


Tom.


User currently offlineVS744 From United Kingdom, joined Aug 2001, 677 posts, RR: 1
Reply 4, posted (6 years 5 months 1 week 4 days 8 hours ago) and read 4854 times:

Interesting - I guess that explains some airlines doing it and some not, it must be an efficiency/power thing. i'll stop worrying about it now!

User currently offlineAirbus_A340 From Hong Kong, joined Mar 2000, 1560 posts, RR: 19
Reply 5, posted (6 years 5 months 1 week 4 days 7 hours ago) and read 4843 times:

In Cathay we turn the packs off just before take-off, which fulfills our Before Take-Off Checklist. At thrust reduction PNF selects one pack on at a time, with a slight pause before turning the second one on.


People. They make an airline. www.cathaypacific.com
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8904 posts, RR: 76
Reply 6, posted (6 years 5 months 1 week 4 days 7 hours ago) and read 4827 times:
AIRLINERS.NET CREW
HEAD MODERATOR

The MD11F does switch off all 3 bleed air valves automatically when setting take off thrust... And switches it on again after passing 1500' AGL...
So you have all the air for the engines and dont waste it for the aircondition  Wink

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlineModesto2 From United States of America, joined Jul 2000, 2769 posts, RR: 6
Reply 7, posted (6 years 5 months 1 week 4 days 7 hours ago) and read 4827 times:

At my airline, we run the packs off the APU until after takeoff. The "after takeoff" checklist calls for shutting down the APU and transferring the packs to the engine bleeds. However, our anti-icing systems on the E145 can only be run from engine bleeds, so for icing takeoffs, the packs are turned off so the packs can power the anti-icing system.

User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 8, posted (6 years 5 months 1 week 3 days 23 hours ago) and read 4723 times:

Engine bleed extraction adds to the fuel burn to mantai desired EPR/RPM.
By using Bleed off T/O,this loss of Airflow/Thrust can be saved & utilised during the T/O.In todays world where Airlines are trying to save every smallest $,it makes sense.

Quoting WILCO737 (Reply 6):
The MD11F does switch off all 3 bleed air valves automatically when setting take off thrust... And switches it on again after passing 1500' AGL...

Is this a feature of every MD-11 or only the freighter.

regds
MEL



Think of the brighter side!
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8904 posts, RR: 76
Reply 9, posted (6 years 5 months 1 week 3 days 18 hours ago) and read 4684 times:
AIRLINERS.NET CREW
HEAD MODERATOR

Quoting HAWK21M (Reply 8):
Is this a feature of every MD-11 or only the freighter.

I guess for all MD11s, but I dont know because I only fly freighters...  Wink

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlineCoolGuy From United States of America, joined Jan 2005, 414 posts, RR: 0
Reply 10, posted (6 years 5 months 1 week 3 days 10 hours ago) and read 4609 times:

How much power does an aircraft A/C use? And why would more power to the cabin affect takeoff thrust? It certainly makes sense but how does an engine power the electrical systems onboard?

User currently offlineTdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 11, posted (6 years 5 months 1 week 2 days 22 hours ago) and read 4535 times:



Quoting CoolGuy (Reply 10):
How much power does an aircraft A/C use? And why would more power to the cabin affect takeoff thrust? It certainly makes sense but how does an engine power the electrical systems onboard?

A/C is a pretty significant power hog. I'm not sure how it works out on a pneumatic system, but the 787 A/C motors are in the range of tens of kW.

More power to the cabin affects takeoff thrust because it's power you're taking out of the engine. If you have a pneumatic tap, you're taking high pressure air from the engine which isn't available to be used for combustion (and hence provide thrust). If you have an electric system, the generator is driven by a driveshaft from one of the engine spools. Power out the driveshaft is power unavailable to spin the fan.

Tom.


User currently offlinePilotpip From United States of America, joined Sep 2003, 3139 posts, RR: 11
Reply 12, posted (6 years 5 months 1 week 2 days 6 hours ago) and read 4465 times:

We run the packs off the APU on takeoff and up to 10,000feet.

Unless we're taking off in icing conditions. The APU bleeds do not provide sufficient heat for the anti ice. As a result of the penalty of A/I, we turn the packs off on takeoff for icing takeoffs.



DMI
User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 13, posted (6 years 5 months 1 week 1 day 20 hours ago) and read 4393 times:



Quoting Pilotpip (Reply 12):
We run the packs off the APU on takeoff and up to 10,000feet.

What Type are you reffering too.
regds
MEL



Think of the brighter side!
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8904 posts, RR: 76
Reply 14, posted (6 years 5 months 1 week 1 day 17 hours ago) and read 4370 times:
AIRLINERS.NET CREW
HEAD MODERATOR

On the 737 we always had the packs on during take off! Runways were always long enough and the terrain no problem as well! Even with anti- ice on, there was still enough power left for the engines.
I only had to do one take off with PACKS OFF... It was in WAW, only the short runway was open, it was raining, runway pretty short and we were heavy. So we switched the packs off and took off! Anti- Ice wasnt needed...
And as I said on the MD11 ALL take offs are without the engine bleed! The engines have all the air they need  Wink It is an unpressurized take off! The APU is off as well. The outflow valve is fully closed so you don't feel much of the climb... and then the bleed turns back on and you get back your air  Wink

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 15, posted (6 years 5 months 1 week 1 day 15 hours ago) and read 4359 times:



Quoting WILCO737 (Reply 14):
The outflow valve is fully closed

Why "fully closed".Is this a company SOP.
regds
MEL



Think of the brighter side!
User currently offlineZeke From Hong Kong, joined Dec 2006, 8643 posts, RR: 75
Reply 16, posted (6 years 5 months 1 week 1 day 14 hours ago) and read 4351 times:



Quoting Vs744 (Thread starter):
Does anyone know if this has always happened, or whether it was recently introduced and for what reason? I would take a guess at is being something to do with power but not sure whether it always happened or I only recently noticed it.

For take-off, full bleeds can be used or one can consider selecting packs off or APU bleed on to improve take-off performance. Selecting packs off without APU will also improve fuel burn. The normal procedure would then be to select pack 1 on after climb thrust is selected and pack 2 on after flap retraction, some operators just select both back on on thrust reduction. This has the effect of reducing fuel burn by 2 to 3 kg on an A320 increasing to 5 to 10 kg on an A340-500/600 for every takeoff.

With APU bleed the engine fuel burn will be decreased by the same amount. However with APU used from push back with 12 minutes taxi, the additional APU fuel burn is 30kg for an A320 and 60 to 70kg for an A340. In economic terms, the APU fuel and maintenance cost is largely offset due to decreased engine maintenance costs bleeds off (higher FLEX temp).

The main benefit is in the long term maintenance costs, the aircraft will be able to takeoff with a lower thrust setting, thus subjecting the parts to lower temperatures and stresses, which will extend the lift of the engine on the wing, or the number of parts that need to be replaced at overhaul, and lowers the probability of an engine failure.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8904 posts, RR: 76
Reply 17, posted (6 years 5 months 1 week 1 day 13 hours ago) and read 4341 times:
AIRLINERS.NET CREW
HEAD MODERATOR



Quoting HAWK21M (Reply 15):

No, it's Mrs. Douglas feature... The MD11F tried to maintain the pressure and she can only achieve it, when closing the outflow valve... It all happens automatically...

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlinePilotpip From United States of America, joined Sep 2003, 3139 posts, RR: 11
Reply 18, posted (6 years 5 months 1 week 1 day 11 hours ago) and read 4327 times:



Quoting HAWK21M (Reply 13):

What Type are you reffering too.
regds
MEL

MEL,

I'm in the EMB-145. I've seen other companies do it differently though.



DMI
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8904 posts, RR: 76
Reply 19, posted (6 years 5 months 1 week 1 day 11 hours ago) and read 4322 times:
AIRLINERS.NET CREW
HEAD MODERATOR



Quoting Pilotpip (Reply 18):
I'm in the EMB-145

Thank god your are not ON the EMB-145 Big grin must be pretty windy up there  box 

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlinePilotpip From United States of America, joined Sep 2003, 3139 posts, RR: 11
Reply 20, posted (6 years 5 months 1 week 1 day 10 hours ago) and read 4302 times:

You'd think it's windy inside too with all the noise.  Smile

Somebody forgot to tell those crazy Brazilians that when slapping a different wing, a couple fuselage plugs and a pair of turbofans on the Brazillia they may want to consider a redesign of the nose. It may be nice and quiet when it's in the lower 20s at 300kts true but it's pretty loud when it's faster.



DMI
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8904 posts, RR: 76
Reply 21, posted (6 years 5 months 1 week 1 day 10 hours ago) and read 4300 times:
AIRLINERS.NET CREW
HEAD MODERATOR



Quoting Pilotpip (Reply 20):

yeah, everybody is talking about aircraft noise: I make it Big grin Big grin

Because of the noise in the cockpit and not having any noise canceling headsets I use earplugs Big grin Very helpful and quiet  Wink

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlinePilotpip From United States of America, joined Sep 2003, 3139 posts, RR: 11
Reply 22, posted (6 years 5 months 1 week 1 day 4 hours ago) and read 4256 times:

Oh my DC's work just fine. And you gotta love that mean green color.  Smile


DMI
User currently offlineAbnormal From UK - England, joined Aug 2007, 81 posts, RR: 0
Reply 23, posted (6 years 5 months 1 week 22 hours ago) and read 4220 times:



Quoting Zeke (Reply 16):



Quoting Zeke (Reply 16):
This has the effect of reducing fuel burn by 2 to 3 kg on an A320 increasing to 5 to 10 kg on an A340-500/600 for every takeoff.

With APU bleed the engine fuel burn will be decreased by the same amount. However with APU used from push back with 12 minutes taxi, the additional APU fuel burn is 30kg for an A320 and 60 to 70kg for an A340. In economic terms, the APU fuel and maintenance cost is largely offset due to decreased engine maintenance costs bleeds off (higher FLEX temp).

The main benefit is in the long term maintenance costs, the aircraft will be able to takeoff with a lower thrust setting, thus subjecting the parts to lower temperatures and stresses, which will extend the lift of the engine on the wing, or the number of parts that need to be replaced at overhaul, and lowers the probability of an engine failure

Excellent points Zeke. I get about the same numbers. Any issues re passenger comfort?


User currently offlineZeke From Hong Kong, joined Dec 2006, 8643 posts, RR: 75
Reply 24, posted (6 years 5 months 1 week 15 hours ago) and read 4194 times:



Quoting Abnormal (Reply 23):
Any issues re passenger comfort?

I don't think so, we have use said procedure for longer than I can to remember. For the pilots, and regular passengers, it is normal procedure. For new passengers, it is just the way things are done.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
25 Abnormal : Thanks Zeke. Interesting points I think I'm gonna mull over a bit. The hard part will be getting Stds on side I think.
26 Airbus_A340 : Since my post, I've heard that in CX's Airbus Fleet Forum they discussed (that in the not too distant future) we will be doing Packs-ON for FLEX take-
27 Post contains images FLY2HMO : But then when they turn the packs off I love it when you see half the hands in the cabin up in the air trying to adjust the gaspers, then suddenly a
28 Post contains images Wowpeter : Simple, our lovely CX management decided not to install the gaspers in the first place... save weight and maintanence and no pax waving their hands b
29 HAWK21M : so they blanked out the ports of the PSU.Is it. regds MEL
30 Wowpeter : Yup, just a blank white piece of plastic over the passenger service unit! I don't think there's any gaspers install in any CX plane (340, 744, 330...
Top Of Page
Forum Index

Reply To This Topic Airbus Air Conditioning During T/O
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
ATR-72-500 Air Conditioning posted Tue Jun 19 2007 13:34:19 by Radimz
Air Conditioning "packs" posted Tue Jun 6 2006 06:35:32 by AirWillie6475
Air Conditioning X Pressurization posted Mon Feb 9 2004 20:14:25 by S.p.a.s.
How Does The Air-Conditioning System Work? posted Wed Jun 20 2001 04:06:04 by United Airline
B707 Air Conditioning posted Sat Jun 2 2001 11:10:27 by EDR 374
Air Conditioning System In Aircrafts posted Thu May 31 2001 03:51:17 by Jm-airbus320
Air Conditioning posted Mon May 14 2001 19:51:46 by Ngr
Weird Sounds During Taxi On Airbus Widebodies? posted Thu Jun 21 2007 01:29:58 by SW733
DRY Air ... Boeing Vs Airbus posted Thu Feb 19 2004 01:26:25 by Airbear
Noise On Airbus During Pushback posted Mon Aug 14 2000 13:15:50 by TriStar

Sponsor Message:
Printer friendly format