overloaduk
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Why Did The Usaf Pick The 742 Over The 743?

Tue Mar 30, 2010 9:31 pm

Well the question is in the title Why Did The USAF Pick The 742 Over The 743?
 
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kc135topboom
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RE: Why Did The Usaf Pick The 742 Over The 743?

Tue Mar 30, 2010 9:35 pm

A B-747-300 configuered the same as the VC-25As would have been heavier, reducing the unrefueled range slightly and there was no need for the SUD.
 
Spacepope
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RE: Why Did The Usaf Pick The 742 Over The 743?

Wed Mar 31, 2010 1:52 am

Or... There was no 743 when the E-4s were ordered.
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kanban
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RE: Why Did The Usaf Pick The 742 Over The 743?

Wed Mar 31, 2010 4:18 am

although the VC-25 was ordered under Reagan's watch, the design work began earlier. At that time the -300 was just entering flight test. one of the requirements was the the airframe and engines had a proven reliability. Yes they could have added the SUD (stretched upper deck) however they didn't. since the wing tools were already being modified for the 747-300 and the was little difference they were used.
 
Flighty
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RE: Why Did The Usaf Pick The 742 Over The 743?

Wed Mar 31, 2010 4:43 am

We will see if the new 748 based AF1 will be a freighter model or the I model. Most likely an I model. They will find a use for the space.
 
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N328KF
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RE: Why Did The Usaf Pick The 742 Over The 743?

Wed Mar 31, 2010 11:15 am

Quoting Flighty (Reply 4):
We will see if the new 748 based AF1 will be a freighter model or the I model. Most likely an I model. They will find a use for the space.

When you're customizing an aircraft to that level, does it really count as either?
When they call the roll in the Senate, the Senators do not know whether to answer 'Present' or 'Not guilty.' -Theodore Roosevelt
 
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kc135topboom
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RE: Why Did The Usaf Pick The 742 Over The 743?

Wed Mar 31, 2010 11:48 am

Quoting kanban (Reply 3):
one of the requirements was the the airframe and engines had a proven reliability.

You do understand the VC-25A is really a hybrid airplane don't you? It incorproates parts of the B-747-200B, B-747-300, and B-747-400 designs, as well as unique features (like left side cargo doors with airstairs, duel APUs, etc.). There are no other B-747s anywhere in the world like then, not even the USAF E-4Bs. The GE CF-6-80 engines are from the B-747-400, which did not fly on any other airplanes at the time, and the B-747-400 had an EIS just a year before the VC-25s did (although the VC-25As actually flew before the -400 did).
 
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kanban
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RE: Why Did The Usaf Pick The 742 Over The 743?

Wed Mar 31, 2010 4:14 pm

Quoting KC135TopBoom (Reply 6):
You do understand the VC-25A is really a hybrid airplane don't you? It incorproates parts of the B-747-200B, B-747-300, and B-747-400 designs,

Yes I understand that, however I also was involved in the building and production of these a/c and there were constraints on anything that was "new" and not sufficiently tested. The Air Force and Secret Service were very cautious. he engines were well tested. They did not want an engine failure or a sudden decompression because a new door or hinge point was weak. Still they birds are becoming more and more difficult to maintain and upgrade in terms of both parts and cost.

Let's leave it at that and welcome the effort to design and build replacements.
 
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kc135topboom
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RE: Why Did The Usaf Pick The 742 Over The 743?

Thu Apr 01, 2010 10:31 pm

Quoting kanban (Reply 7):
Let's leave it at that and welcome the effort to design and build replacements.

good point
 
Flighty
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RE: Why Did The Usaf Pick The 742 Over The 743?

Fri Apr 02, 2010 6:08 pm

Quoting N328KF (Reply 5):
When you're customizing an aircraft to that level, does it really count as either?

Good point. It depends on the level of EMP protection I would guess. If not for that, it could be a standard 748I with antennae on the roof, and maybe some environmental work on the cargo deck.

The crazy thing about "heavy customization" is that it's expensive to develop, spare parts do not exist for custom parts except from the original run, and besides, the "proven airframe" standard loses its meaning as well.

As a lay person, it looks like the 757 C-32 project was cheap and done right. A standard few 748-I with some EMP protection would be great. Lastly, although the VC-25 is a separate type, everybody calls it "the president's 747". It is, obviously, some kind of 747. Which kind... philosophical question.

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