Ruscoe
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Why No Double Decker 747?

Sun Dec 08, 2002 10:06 pm

It seems like such an obvious thing to do to increase capacity in the 747 that I figure their must be some pretty good reason why Boeing don't simply stretch the upper deck all the way back.

Does anyone know the reason why?

Ruscoe
 
thadocta
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RE: Why No Double Decker 747?

Sun Dec 08, 2002 10:21 pm

Two words - "unfavourable aerodynamics" - which is another way of saying "loss maker".

Dave
 
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RayChuang
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RE: Why No Double Decker 747?

Sun Dec 08, 2002 11:11 pm

Actually, when Boeing was in the development stage of the 747 they did seriously look at a full double-deck configuration. They dropped it because a full double-deck configuration would have sacrificed too much carrying capacity for the LD-3 containers and also would not have been the right structural configuration for a pure freighter, hence the reason why the original 747 came out with a single deck configuration with a small upper deck for the cockpit and a small lounge/seating area just right behind the cockpit.

In a way, the final 747-100 configuration was essentially a heavily modified version of the Boeing C-5 proposal, but with wings mounted on the bottom of the fuselage and still maintaining the ability to incorporate a fold-up nose on the freighter versions.
 
backfire
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RE: Why No Double Decker 747?

Sun Dec 08, 2002 11:25 pm

There were certainly models built of a twin-deck 747 back in the development days. But you can't simply stretch the present upper deck rearwards and hope that it won't seriously alter the aircraft's economic characteristics. The 747's airframe is designed to accommodate the forward twin-deck only; extending it would, at the very least, add a fair amount of weight to the rear of the aircraft which would then upset the aerodynamics. It might fly, but as Thadocta pointed out, it won't necessarily fly economically even with the additional capacity -- and with airline margins as they are, an uneconomical aircraft won't sell.
 
AvObserver
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RE: Why No Double Decker 747?

Tue Dec 10, 2002 8:44 am

The original 747 project leader, Joseph Sutter, said himself that a full double deck on the 747 would be structurally inefficient due to added weight. Expect the upper deck to be stretched only slightly in any future 747 stretch proposals.
 
flyingbronco05
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RE: Why No Double Decker 747?

Tue Dec 10, 2002 8:51 am

If there are so many negatives, then why is Airbus building the A380?

I personally think the A380 is going to be a flop!
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brons2
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RE: Why No Double Decker 747?

Tue Dec 10, 2002 8:53 am

If you go to Boeing's site and look at the 742's Airport Planning guide, there is a section where it discusses possible future variants of the 747. One of which is a version where the upper deck goes all the way back. Such a variant would have seated 700 passengers, according to the web page.
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Klaus
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Flyingbronco05

Tue Dec 10, 2002 11:33 am

Flyingbronco05: If there are so many negatives, then why is Airbus building the A380?

The A380 differs in many aspects...
- The upper deck is substantially wider.
- The cargo hold makes much better use of the available space.
- There is considerably less "wasted space" than in the 747 (which was designed in different times with much different priorities and matched those very well - but times have changed since then).
- The entire aerodynamic package for the A380 is designed for the full-length twin-dual-aisle-deck configuration - with room for a stretch.


Flyingbronco05: I personally think the A380 is going to be a flop!

With the already existent pre-orders it doesn´t look a lot like that. But we´ll see.

The point is, there´s a huge difference between trying to modify an existent design and starting from scratch. Superficial outward similarities don´t have all that much weight.