WingedMigrator
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787 Keel Beam

Tue Jul 17, 2007 2:38 pm

I read in this week's Aviation Week issue that the 787 sports an external (!) keel beam that, for aerodynamic reasons, protrudes out of the belly fairing under the center wing box. Does anyone have a close-up photograph of said appendage, from the roll-out ceremony?
 
flashflyguy
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RE: 787 Keel Beam

Tue Jul 17, 2007 3:25 pm

You might like to have a look at flickr.com - heaps of B787 rollout photos (from all angles) have been uploaded there. Just search for 787.
 
jogales
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RE: 787 Keel Beam

Tue Jul 17, 2007 4:01 pm

I believe this is what they're referring to:

http://www.flickr.com/photos/rverginia/770894458/

Click on "all sizes" for a much bigger view

Josh
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deltadawg
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RE: 787 Keel Beam

Tue Jul 17, 2007 11:05 pm

Quoting WingedMigrator (Thread starter):
I read in this week's Aviation Week issue that the 787 sports an external (!) keel beam that, for aerodynamic reasons,

What is the reasoning? Can anyone explain the details of why it is like that?
GO Dawgs, Sic' em, woof woof woof
 
AirframeAS
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RE: 787 Keel Beam

Tue Jul 17, 2007 11:14 pm

I wonder if IAD787 can provide us with some insight? Im also curious to know this too!
A Safe Flight Begins With Quality Maintenance On The Ground.
 
oldeuropean
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RE: 787 Keel Beam

Tue Jul 17, 2007 11:33 pm

This is definitely not the misteriously disapeared shark fin.  rotfl 

Axel
Wer nichts weiss muss alles glauben
 
WingedMigrator
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RE: 787 Keel Beam

Wed Jul 18, 2007 4:16 am

Quoting Jogales (Reply 2):
Click on "all sizes" for a much bigger view

Thanks, that's exactly what I was looking for. Flickr is a gold mine of 787 photos, much more abundant than a.net or even Flightblogger! For example, I saw lots of shots of airplane #2.

Quoting DeltaDAWG (Reply 3):
What is the reasoning? Can anyone explain the details of why it is like that?

Here is the direct, fair-use quote from the article in AWST:

Quote:
The externally visible keel beam was perhaps the most surprising feature, thought to represent a first for any Boeing commercial jetliner to date. Measuring 340 in., it begins toward the aft end of the Kawasaki-made Section 43 forward fuselage and ends just aft of the front end of the Alenia Section 46 center-rear fuselage. It runs under, not through, the Kawasaki Section 11 center wing box.

In all previous models the keel beam, a strengthening structural member running forward and aft through the bottom of the fuselage, has been hidden within the contours of the fuselage itself. Although clearly visible on the 787, the structure is contained within a fairing only a few inches deep. Boeing says the beam is not a bolted add-on.

The keel beam “is a very deep structure, not externally mounted,” says 787 Chief Project Engineer Tom Cogan. “It happens to protrude by choice. We could have made the fairing bigger for appearance, but by choice we wanted the fairing to be as small as possible and that’s why you see more contouring on the bottom than people are used to.”

Viewed from either end, the beam also displays slight area ruling to reduce transonic drag rise in the belly area flow field between the large engine nacelles. “A lot of study and aerodynamic work went into this aspect of the design and this was the best solution,” adds Cogan.

There's also information about another unusual 787 design detail: those funky ram air scoops for the air packs. Looks like the extra drag from those protruding scoops will have to be weighed in the balance of the cost/benefit of using a 'bleedless' architecture.
 
boeing767mech
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RE: 787 Keel Beam

Wed Jul 18, 2007 5:02 am

I don't know the reason why,but the Convair 880/990's also had a external longeron running down the center line of the aircraft from just ahead of the center section and ended just forward of the aft outflow valve (not to be confused with the speed fairing on the upper crown of the airframe), They also had a smaller one around the tail bumper area.

Just a bit of useless information

David
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AirframeAS
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RE: 787 Keel Beam

Wed Jul 18, 2007 7:05 am

Quoting Oldeuropean (Reply 5):
This is definitely not the misteriously disapeared shark fin.

I fail to see your humor. We are talking about the 787's keel beam, which is on the BOTTOM of the aircraft. The tail has nothing to do with it.
A Safe Flight Begins With Quality Maintenance On The Ground.
 
rwessel
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RE: 787 Keel Beam

Wed Jul 18, 2007 7:49 am

Some bizjets have a strip similar to that running down the "keel" to protect center body fuel tanks and the rest of the hull in case of a wheels up landing.

Although that's usually a removable/replaceable piece, unlike what's Boeing has said here.
 
rverginia
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RE: 787 Keel Beam

Wed Jul 18, 2007 8:27 am

Hi all.
I am glad you are enjoying my photo of the keel beam on Flickr.
 
WingedMigrator
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RE: 787 Keel Beam

Wed Jul 18, 2007 10:19 am

Quoting Rverginia (Reply 10):
I am glad you are enjoying my photo of the keel beam on Flickr.

Lucky dog, you were there!  bouncy 
 
oldeuropean
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RE: 787 Keel Beam

Wed Jul 18, 2007 4:14 pm

Quoting AirframeAS (Reply 8):
I fail to see your humor. We are talking about the 787's keel beam, which is on the BOTTOM of the aircraft. The tail has nothing to do with it.

I know where the keel is. Sorry that I've affronted you by making a joke about your beloved 787. That aircraft must be some kind of a fetish for some folks here.

Axel

[Edited 2007-07-18 09:16:17]
Wer nichts weiss muss alles glauben
 
bill142
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RE: 787 Keel Beam

Wed Jul 18, 2007 8:28 pm

Quoting DeltaDAWG (Reply 3):
What is the reasoning? Can anyone explain the details of why it is like that?

It's a skid rail for when it has to do gear up landings.  wink