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Huge Tube Inside 747's Belly?  
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 8
Posted (11 years 6 months 1 day 2 hours ago) and read 6302 times:

Hi guys.

The photographer of this photo asks ........

"There is a huge tube in there, anybody know what it's for?"

I'd like to know the answer too.

Actually, there are 2 metal tubes that can be seen inside this KLM 747-206's belly. One's close to the wing root and the other huge one is deep inside under the middle of the cargo hold floor.

What are these tubes used for?

For the fun of it, I'll take a guess. They're both used for the 747's Environmental Control System. The smaller tube supplies hot bleed air from engines #3 and #4 to the Air Conditioning Pack's Heat Exchangers and Air Cycle Machines (these 3 A/C packs are located near the main landing gear bays). The air then flows from the A/C packs (at cabin air temperature) via the huge tube in the belly and is then transported via ducts to all the overhead air vents in the passenger cabin, cockpit, & cargo hold, where it's used to pressurize the aircraft and control air temperature.

That's just a guess ....am I close?  Laugh out loud

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Photo © Tim de Groot - AirTeamImages

Chris  Smile

"Just a minute while I re-invent myself"
7 replies: All unread, jump to last
User currently offlineMiamiair From , joined Dec 1969, posts, RR:
Reply 1, posted (11 years 6 months 1 day ago) and read 6236 times:

Let's not forget that the bleed air from the APU has to make its way forward from the tail also...

[Edited 2004-11-26 22:30:58]

User currently offlineQantasA332 From Australia, joined Dec 2003, 1500 posts, RR: 22
Reply 2, posted (11 years 6 months 1 day ago) and read 6218 times:

The larger tube which is further into the aircraft is most likely an air conditioning pack or part of that general sub-system. As for the small pipe, I'm pretty sure it's an engine bleed-air duct...


User currently offline242 From United States of America, joined Oct 2000, 498 posts, RR: 0
Reply 3, posted (11 years 6 months 23 hours ago) and read 6201 times:

The smaller tube is bleed air, the tubing starts out silver/grey when new and turns a bluish color with heat.

The larger tube is likely a pack heat exchanger air inlet duct.

User currently offline747NUT From Australia, joined Sep 2004, 78 posts, RR: 0
Reply 4, posted (11 years 6 months 17 hours ago) and read 6097 times:

The smaller of the two tubes is the pneumatic ducting that comes from the #3 & 4 engines (there is also one on the opposite wing for the # 1 & 2 )
The larger duct is the ram air cooling for the airconditioning heat exchangers, you can't see the intake on that photo but you can see it on this one.

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Photo © Benjamin Freer

Regards Mike

If it's not broken, don't fix it !
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 8
Reply 5, posted (11 years 6 months 16 hours ago) and read 6076 times:

Hi guys.

OK, so those tubes do provide engine bleed air for the 747's pneumatic system and the environmental control system..... I was close enough! Big grin Thank You, Thank You, no applause please .... just throw money!!!  Laugh out loud

It's kinda neat to see inside the guts of a 747's belly.

Chris  Smile

"Just a minute while I re-invent myself"
User currently offlineAviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 36
Reply 6, posted (11 years 6 months 3 hours ago) and read 5937 times:

Especially for you made another image today to clear up this issue.

The big one is the ram air intake and the smaller one which Tim referred too is the bleed air supply.

The truth lives in one’s mind, it doesn’t really exist
User currently offlineEfohdee From United States of America, joined Oct 2004, 214 posts, RR: 0
Reply 7, posted (11 years 5 months 4 weeks 1 day 1 hour ago) and read 5766 times:

Large intestines!!!
 Smile/happy/getting dizzy

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