highflyer9790
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Do The Triangular Inlets Under 747 Serve A Purpose?

Thu Jul 07, 2005 10:59 am

Does anyone know whether the triangular shaped inlets on the underbelly of all 747s serve a purpose? In the photo you can clearly see the 3 of them in front of the under carriage and by the leading edge

http://images.airliners.net/open.fil...r=21&prev_id=622768&next_id=573962

apologies if some of earlier posts had already been discussed in detail...

regards
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citationjet
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Do The Triangular Inlets Under 747 Serve A Purpose?

Thu Jul 07, 2005 11:09 am

Based on what I learned from a previous thread, they are ram air intakes for cooling the heat exchangers for the air conditioning packs.

http://www.airliners.net/discussions/tech_ops/read.main/62453/4/
Reply #8.

.
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PhilSquares
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Do The Triangular Inlets Under 747 Serve A Purpose?

Thu Jul 07, 2005 11:30 am

They are the inlets for the air conditioning packs. If you look further aft, to about 3 feet prior to the body gear doors you will see the exit doors, they're louvered and will automatically position, just like the inlet doors.
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VirginFlyer
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RE: Do These Serve A Purpose?

Fri Jul 08, 2005 9:31 am

HighFlyer9790 - Welcome to Airliners.net. A few quick asides for you:

1)You can display an airliners.net picture using the following code:

[photoid:608498], but replaicing '[' and ']' with '<' and '>':


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Photo © Stuart Lawson



2) These sort of technical questions are probably better asked in the Tech/Ops Forum.

3) Please be descriptive with your titles - it helps everyone get an idea of what your thread is about.

Once again, welcome, and I hope you enjoy all this site has to offer!

V/F
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flyinTLow
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 08, 2005 9:59 am

Yes, air inlets for the a/c. And as mentioned before the outlets are about 10 feet behind that (rather brown in that picture). A very good spot to stand about another 10 feet down the fuselage in the winter when it is cold, cause a lot of hot air comes out there. Not too fancy if it's hot on the tarmac already  Smile

Cheers,
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DeltaGuy
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 08, 2005 10:36 am

They're also excellent for drying off your rain gear when it stops raining on the ramp. Those packs do make alot of noise though.

DeltaGuy
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HAWK21M
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 08, 2005 11:42 am

Ram Air Inlets for the Air Conditioning System.

Quoting DeltaGuy (Reply 5):
They're also excellent for drying off your rain gear when it stops raining on the ramp

The Exhaust Louvers are Excellent Dryers. {bigthumbsup

regds
MEL
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Starlionblue
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 08, 2005 12:14 pm

Quoting HighFlyer9790 (Thread starter):
Does anyone know whether the triangular shaped inlets on the underbelly of all 747s serve a purpose?

Totally useless and purely decorative Big grin Sorry your title gave me a laugh but it was a good question.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
ikramerica
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 08, 2005 2:44 pm

Yeah, A and B like to design lots of useless holes into their fuselages. Makes for a greater engineering challenge. And if you don't challenge the engineers, how will they ever learn?
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OzLAME
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 08, 2005 9:29 pm

These inlets are not quite triangular, they are more a sort of teardrop shape that has the bottom cut off. The generic name for inlets of this shape is NACA Duct, after the National Advisory Commitee for Aeronautics (forerunner to NASA) that came up with the shape. The shape means that drag associated with the opening is minimal; these ducts can be very large, as on the 747, or very small, e.g. an inlet on an engine nacelle. They can be found on all sorts of different aircraft; you can see a NACA Duct on the a/c shown below, forward of the door and below the windscreen.

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Photo © Maartenw

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CX Flyboy
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Sat Jul 09, 2005 12:42 am

They serve a purpose? I thought they looked pretty. Is that not a good enough reason these days?
 
Areopagus
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Sat Jul 09, 2005 1:47 am

The NACA duct was used for the engine air inlets for the North American Aviation F-93, a development of the F-86. See, for example, Wikipedia, but note that their overhead view shows a more conventional inlet that was tried after the NACA inlet turned out not to supply enough air for the engine.

(Edited for typo)

[Edited 2005-07-08 18:48:53]
 
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Starlionblue
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Sat Jul 09, 2005 5:51 am

Quoting CX flyboy (Reply 10):
They serve a purpose? I thought they looked pretty. Is that not a good enough reason these days?

Only if the plane has a nice livery and is washed regularly Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
VSIVARIES
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Sat Jul 09, 2005 6:31 am

Air to Air missile hatches - a new system employed by VS. It's meant to be confidential.  shhh  These must have opened by accident.
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MD11Engineer
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Sat Jul 09, 2005 7:49 am

Chemtrail dispensers Big grin

Jan
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aeroweanie
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RE: Do The Triangular Inlets Under 747 Serve A Pur

Tue Jul 12, 2005 1:02 pm

Quoting OzLAME (Reply 9):
These inlets are not quite triangular, they are more a sort of teardrop shape that has the bottom cut off. The generic name for inlets of this shape is NACA Duct, after the National Advisory Commitee for Aeronautics (forerunner to NASA) that came up with the shape.

They are NACA Inlets, not NACA ducts. Ducts carry air from one place to another. Inlets allow air to flow into a body. They are unique inlets in that they are semi-submerged and still have reasonable, though not great, pressure recovery.
 
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HAWK21M
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Wed Jul 13, 2005 8:12 pm


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Photo © Stuart Lawson


Why Three Inlets.Are there Three Packs.Explain the Outboard LH one.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
MD11Engineer
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Wed Jul 13, 2005 10:46 pm

Yes, three packs on the 747

Jan
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HAWK21M
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Wed Jul 13, 2005 11:00 pm

Quoting MD11Engineer (Reply 17):
Yes, three packs on the 747

Interesting.
What are the Reffered to as Left pack,Right Pack & Centre pack.
regds
MEL
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air2gxs
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Wed Jul 13, 2005 11:01 pm

Quoting HAWK21M (Reply 16):
Why Three Inlets.Are there Three Packs.Explain the Outboard LH one.

As far as I know, all pax operators have 3 packs. Some cargo operators have de-activated and removed the #2 pack for weight and cost savings.
 
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NZ1
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 15, 2005 12:10 pm

Quoting HAWK21M (Reply 18):
What are the Reffered to as Left pack,Right Pack & Centre pack

Pack 1, 2 and 3. Not L, C and R.

NZ1
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HAWK21M
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 15, 2005 3:07 pm

Quoting NZ1 (Reply 20):
Pack 1, 2 and 3

Thanks.
And how is the Distribution to the Upper deck on Pax version.How many Zones 3 or more.
regds
MEL
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abhi
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RE: Do The Triangular Inlets Under 747 Serve A Purpose?

Fri Jul 15, 2005 5:02 pm

You can feel the heat from those outlets when you're working the loader in the aft belly. It feels great in the winter but in the summer I tried working the front belly as much as possible.

Funny thing happened to one of the guys one day. He was bringing a stroller from the gate to put in the bulk load and his hat got sucked into the inlet. This happened on the 340 where you can actually see inside the inlet. They're too high on the 747.

Maintenance had to remove the entire panel to get that hat out. They were quick though: delayed the flight only fifteen minutes.

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