747400sp
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Would A KC-747 Been Better Than A KC-10?

Thu Jun 08, 2006 5:17 am

Hello

I wonder if it would have been better if the KC-747 been built instead of the KC-10?
 
TropicBird
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RE: Would A KC-747 Been Better Than A KC-10?

Thu Jun 08, 2006 9:15 am

Yes it would have been better.
 
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kc135topboom
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RE: Would A KC-747 Been Better Than A KC-10?

Thu Jun 08, 2006 7:09 pm

During the ATCA fly off, the B-747-200F tanker was a far superior airplane to the DC-10-30CF, that was eventually chosen. The USAF tanker version, which would have been called the KC-25A, could off load an additional 100,000lbs of fuel over the KC-10A, and carry almost twice the cargo load. Of course the nose cargo door would have also been a plus, in addition to the side cargo door, on both the KC-10 and KC-25.

But, the KC-25 also cost significantly more to operate than the KC-10. That in the end, was the overall deciding factor for the USAF (plus the California Congressional deligation was pushing hard for the KC-10 contract).

Additionally, buying the KC-25 would have also had a significant impact on the C-17 program. The C-17 program started to run into over budget problems about mid point in, what would have been, the KC-25s production, in the mid 1980s.
 
2H4
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RE: Would A KC-747 Been Better Than A KC-10?

Fri Jun 09, 2006 11:52 am




Quoting KC135TopBoom (Reply 2):
During the ATCA fly off, the B-747-200F tanker was a far superior airplane to the DC-10-30CF

Was it also superior in terms of aerodynamic interference between the "fueler" and the "fuelee"? Sorry for the stupid terms, but I'm not familiar with the proper terminology.

I remember reading that the 135 presents more of an aerodynamic interference issue than the 10...something to do with the bow wave and horizontal stab. How did the 747 platform compare?




2H4


Intentionally Left Blank
 
dc1030guy
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RE: Would A KC-747 Been Better Than A KC-10?

Fri Jun 09, 2006 2:27 pm

Quoting KC135TopBoom (Reply 2):
During the ATCA fly off, the B-747-200F tanker was a far superior airplane to the DC-10-30CF, that was eventually chosen. The USAF tanker version, which would have been called the KC-25A, could off load an additional 100,000lbs of fuel over the KC-10A, and carry almost twice the cargo load. Of course the nose cargo door would have also been a plus, in addition to the side cargo door, on both the KC-10 and KC-25.

By what measure was the 747 a far superior airplane (just offload and cargo)? The 747 had the same boom as the KC-135. The boom envelope on the KC-10 is much larger than the 747/135 design thus making it easier for the receiver aircraft to refuel. The boom is also fly-by-wire design with more advanced features than the Boeing. Also, it has an additional emergency disconnect system to prevent brute force disconnects ... the Boeing does not have. Boeing essentially took a 747 and slapped a 135 boom on it. They dropped the ball.

Almost twice the cargo? The KC-10 can haul 160,000lbs ... the 747-200 can haul 99,000 kg (according to Boeing's website) ... which by my calculator equates to 198,416lbs.

The KC-10 can hold 356,000 lbs of fuel. The KC-747 could hold 456K? Who the hell wants to loiter that long???

Sure, the 747 is a larger plane and thus able to haul more cargo and off load more gas. Bigger isn't always better. I too do think in the end (besides the bailout of McD), the 747's large size and large operating cost is what tipped the scale in favor of the DC-10. It is hard enough to get a KC-10 into many of the locations we fly to ... I can only imagine having to bring in a bigger aircraft.

My two cents ...

Pat
 
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kc135topboom
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RE: Would A KC-747 Been Better Than A KC-10?

Fri Jun 09, 2006 8:09 pm

Quoting 2H4 (Reply 3):
Was it also superior in terms of aerodynamic interference between the "fueler" and the "fuelee"? Sorry for the stupid terms, but I'm not familiar with the proper terminology.

I remember reading that the 135 presents more of an aerodynamic interference issue than the 10...something to do with the bow wave and horizontal stab. How did the 747 platform compare?

Aerodynamic differences between the KC-135 and KC-10 are a lot. The -135's inboard engines tend to keep the receiver close to the centerline. The horizontal stab has little to no effect on both the -10 and -135, as they are adjustable inflight. The -10's centerline engine effects the receiver as he approaches the pre-contact area, but not a lot, then the wing mounted engines have the same centering effect as the -135s engines.

The bow wave comes off the receiver, not the tanker. For a C-5 or E-4 receiver, they tend to push up on the tankers tail, but if the approach slow enough, it can be trimmed out.

Quoting Dc1030guy (Reply 4):
By what measure was the 747 a far superior airplane (just offload and cargo)? The 747 had the same boom as the KC-135. The boom envelope on the KC-10 is much larger than the 747/135 design thus making it easier for the receiver aircraft to refuel. The boom is also fly-by-wire design with more advanced features than the Boeing. Also, it has an additional emergency disconnect system to prevent brute force disconnects ... the Boeing does not have. Boeing essentially took a 747 and slapped a 135 boom on it. They dropped the ball.

Almost twice the cargo? The KC-10 can haul 160,000lbs ... the 747-200 can haul 99,000 kg (according to Boeing's website) ... which by my calculator equates to 198,416lbs.

The KC-10 can hold 356,000 lbs of fuel. The KC-747 could hold 456K? Who the hell wants to loiter that long???

Sure, the 747 is a larger plane and thus able to haul more cargo and off load more gas. Bigger isn't always better. I too do think in the end (besides the bailout of McD), the 747's large size and large operating cost is what tipped the scale in favor of the DC-10. It is hard enough to get a KC-10 into many of the locations we fly to ... I can only imagine having to bring in a bigger aircraft.

Don't forget, the KC-25 (like the KC-10 when compared to the DC-10-30CF) is structually different than the B-747-200F. Like the KC-10 holds a lot more fuel than the DC-10-30CF, so would the KC-25 (over a B-747-200F), as both would have had fuel tanks where the lower deck cargo holds would normally be (the body fuel tanks). IIRC, the KC-25 would have held (up to) 460,000lbs of fuel. The cargo capability would have been over 300,000lbs, with a reduced fuel load.

Now, about the KC-10 boom, yes it is much more advanced than what Boeing offered on the KC-25. One of the main reasons it has a larger refueling envelope than the KC-135 boom has, is it is much longer. It also has a different flight control surface, so it is able to reach areas the KC-135 boom cannot. The boom Boeing would build for the KC-25 would have been longer than the -135s, too. It would have been the same lenght as the IIAF KC-747 tankers, but more advanced (not to the degree of the KC-10s boom, though). As to if it would be able to reach the same envelope limits the -10s boom can, I don't really know. Boeing never built a KC-25 prototype boom. You are correct, for the test flights, Boeing used a KC-135 boom. But, that (the KC-135 boom) would not be the production boom.

The version, of the KC-25A, that Boeing was offering had a max gross take off weight of 890,000lbs, and would have had the same GE CF-6-50 engines the KC-10 has. The critical field lenght (IIRC) was around 9,000'.

The KC-10 has a critical feild lenght of some 8,200' and weighs a lot less. It also cost less to operate.

Cost ended up being the deciding factor (remember that the Carter Administration made the selection), not full capability. The USAF really wanted the swing open nose cargo door on the KC-25, something that could never be built into the KC-10.

The KC-25 would have also been able to carry more troops or litters, than the KC-10.

Don't get me wrong. The USAF did not get screwed by buying the KC-10 over the KC-25. The -10 has done very well, but so would the -25, too.
 
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RE: Would A KC-747 Been Better Than A KC-10?

Fri Jun 09, 2006 11:50 pm

For those who haven't seen this, it's a very interesting presentation of the Austrialian Defense Force in thier studies of a tanker/transport study. Particularly the 747F self contained loading/unloading system. (no ground support equipment needed)

http://www.ausairpower.net/APA-2005-02.pdf
I'm not a real aeronautical engineer, I just play one on Airliners.net.
 
TropicBird
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RE: Would A KC-747 Been Better Than A KC-10?

Sat Jun 10, 2006 12:06 am

Today is the deadline for the "Tanker RFI" to the USAF. TopBoom...you have a wealth of knowledge on the KC-25 program. Do you know where there may be some recorded documents of this competition (other than whats in your memory)?
 
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kc135topboom
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RE: Would A KC-747 Been Better Than A KC-10?

Sat Jun 10, 2006 6:49 am

Well, the USAF would no longer be interested in a KC-25A, as the B-747-200F is very old technoligy and no longer in production. But they might be interested in a KC-33A (B-747-400F), or a KC-33B (B-747-400ERF).

There may still be some internet web pages dedicated to the ATCA program. I know you can still find info on the YF-17A, which was just a little earlier program.
 
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kc135topboom
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RE: Would A KC-747 Been Better Than A KC-10?

Sat Jun 10, 2006 7:12 am

Here is a RAAF study of all available tanker aircraft. They did an extensive study before the selection of the A-330MRTT.

http://www.ausairpower.net/TE-AAR-Expand.html
 
TropicBird
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RE: Would A KC-747 Been Better Than A KC-10?

Sat Jun 10, 2006 7:16 am

TopBoom.. can you please give me an idea about what year the KC-10/KC-25 competition started so I can research? Thanks!
 
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kc135topboom
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RE: Would A KC-747 Been Better Than A KC-10?

Sat Jun 10, 2006 7:18 am

The ATCA program began in 1975, and the selection of the KC-10 was in 1979.

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