B707 vs. KC-135

By: Vortex - 18th September 2001 at 22:33 Permalink - Edited 1st January 1970 at 01:00

RE: B707 vs. KC-135

It's a question of which one came first....if you want big, why not use 747s? check the timeline.

By: RadiO - 18th September 2001 at 23:23 Permalink - Edited 1st January 1970 at 01:00

RE: B707 vs. KC-135

LAST EDITED ON 18-09-01 AT 11:23 PM (GMT)[p]While we're on the subject, is the C-135 series structurally any stronger than the commercial 707? If so, are military 707 variants strengthened in any way?

By: Vortex - 19th September 2001 at 07:54 Permalink - Edited 1st January 1970 at 01:00

RE: B707 vs. KC-135

LAST EDITED ON 19-09-01 AT 07:59 AM (GMT)[p]that's a better question...let's see, without even checking claimed reasons, if the engine are similar (it's interesting to note that 707s have used at least three major families of engines), i would say the military derivatives are actually faster and should have better all round performance due to smaller fuselage size. As to why, maybe the military have made signifcant investiments into the KC135 fuselage design (tooling and tailored for military...forgot the boeing model number) and that besides flight performance superiority, it is also structurally stronger? There was a small book on Boeing transports that explain the differences...it has lots of cutaways...don't have that book with me now.

By: avon1944 - 22nd September 2001 at 06:44 Permalink - Edited 1st January 1970 at 01:00

RE: B707 vs. KC-135

The KC-135 was the contract the USAF wanted as a jet tanker
for SAC. William Boeing used the opportunity to explore the
conversion of the KC-135 to a civilian transport. It worked
and the B-707 was born!

Adrian (aka -avon1944)

By: frankvw - 22nd September 2001 at 08:49 Permalink - Edited 1st January 1970 at 01:00

RE: B707 vs. KC-135

Yes, the KC135 is strenghtened (at least the french ones, for the others, i'd have to check). You can see it on the fuselage, between the wings and the tailplanes. You have "metallic circlings" around the aircraft's body.

Frank

By: premkudva - 7th October 2016 at 12:24 Permalink - Edited 1st January 1970 at 01:00

Coming late

... Wouldn't it make more since to use a 707-320 (the largest variant) as a tanker because it can carry more fuel. Why wasn't the KC-135 made bigger?

Obviously my reply is coming very late. Boeing wanted to make the 707 the same size as the KC-135, so that they could use all the existing jigs. But that would mean the plane would have a 3+2 seating. The airlines wanted 3+3 and thankfully even though it costed them more Boeing bent to the wishes of their future customers.

I am guessing increased width in the fuselage to accommodate the extra row would've made the 707 heavier. So again guessing that between the two a 707 tanker probably wouldn't have carried significantly more fuel than the KC-135.

By: Gerard - 7th October 2016 at 19:42 Permalink - Edited 1st January 1970 at 01:00

awesome! reviving a 15 year old topic. But an interesting one

There are a lot of 707 tankers but how is the fuel capacity compared to the KC-135?

By: Dragonflyer - 7th October 2016 at 20:38 Permalink - Edited 1st January 1970 at 01:00

My dad worked on both programs when I was a kid in Seattle. He wasn't a senior guy at the time, just one of the minions buying parts from sub-contractors, but we talked about it later. The original aircraft wasn't a KC-135 or a 707, it was the 367-80 prototype which was developed to test the concepts of a jet transport for many uses. It's fuselage was the slightly narrower one later used on the KC-135. The Air Force (SAC in particular) was desperate for a jet tanker to keep up with its jet bombers, and didn't care about too many other mods (although they did lengthen the fuselage a little from the -80) and ordered them in 1954. Getting them into operation was a far higher priority. By about late 1955 they were beginning to line the ramp at Renton and had production priority over the civilian 707 effort. The original 707 airline design fluctuated a little due to the width issue, but quickly went to the wider fuselage because, among other things, Douglas proposed the DC-8 with 6-abreast seating which the airlines were happier with (not much extra cost, 30 extra seats to sell!). By this time the tanker was well into production and initial operations and met SAC's needs.

There were some later buys of the bigger, wider cabin version, called C-137s, but only a few for special purposes, not tankers (for instance, the President's "Air Force One" aircraft were VC-137s). One of the factors in the original decision, according to my dad, was that at the time with all the B-47s and B-52s coming on line, tanking capability wasn't any more important than the number of "booms available", so getting the KC-135A into the inventory fast was as, or more, important than a two or three year delay to redesign a bigger, wider, heavier aircraft just to get another 10,000 or 15,000 pounds of fuel offload. Besides, I don't think the newer, more powerful fan engines (TF-33s) were available at the time so the bigger heavier aircraft probably would have not produced more real offload anyway.

By: Gerard - 7th October 2016 at 21:19 Permalink - Edited 1st January 1970 at 01:00

I was thinking of the 707 conversion, like the one done by IAI, for Israel, Colombia, South Africa, Iran, Australia, Spain, Omega and so on

By: swerve - 7th October 2016 at 21:38 Permalink - Edited 1st January 1970 at 01:00

My dad worked on both programs when I was a kid in Seattle. He wasn't a senior guy at the time, just one of the minions buying parts from sub-contractors, but we talked about it later. The original aircraft wasn't a KC-135 or a 707, it was the 367-80 prototype which was developed to test the concepts of a jet transport for many uses. It's fuselage was the slightly narrower one later used on the KC-135. The Air Force (SAC in particular) was desperate for a jet tanker to keep up with its jet bombers, and didn't care about too many other mods (although they did lengthen the fuselage a little from the -80) and ordered them in 1954. Getting them into operation was a far higher priority. By about late 1955 they were beginning to line the ramp at Renton and had production priority over the civilian 707 effort. The original 707 airline design fluctuated a little due to the width issue, but quickly went to the wider fuselage because, among other things, Douglas proposed the DC-8 with 6-abreast seating which the airlines were happier with (not much extra cost, 30 extra seats to sell!). By this time the tanker was well into production and initial operations and met SAC's needs.

Nice post. Ta.

There were some later buys of the bigger, wider cabin version, called C-137s, but only a few for special purposes, not tankers .

Except by Brazil, which bought a few aircraft designated KC-137s.

By: eagle - 8th October 2016 at 00:42 Permalink - Edited 1st January 1970 at 01:00

A tanker is not volume limited but weight limited. A wider fuselage would not help. If it's heavier, fuel load is reduced even.
A wider or generally larger fuselage only increases fuel load if you don't want to install fuel tanks in the cabin space and there's still a weight margin left with full wing and lower fuselage tanks. If this drawing is correct, the 707 fuselage would not have increased the KC-135's fuel load even if the engines could have handled more weight, because the lower fuselage compartment is actually smaller:
[ATTACH=CONFIG]248758[/ATTACH]

By: Gerard - 9th October 2016 at 14:37 Permalink - Edited 1st January 1970 at 01:00

time for some pictures ;)

with boom

Israel 707

Iran

Saudia

without boom

Brazil

Australia

Omega

Spain

By: slipperysam - 10th October 2016 at 23:42 Permalink - Edited 1st January 1970 at 01:00

Some fantastic shots! Truly a beautiful family of airplanes.

Not to mention that the shrieking howl of the 4 JT3? was just awe inspiring to hear.

Also the Omega Air Tanker I believe was a former RAAF B707 tanker.

By: Multirole - 11th October 2016 at 08:17 Permalink - Edited 1st January 1970 at 01:00

I think I remember reading somewhere Iran tried to reengine their 707 tanker by replacing the four turbojets with two turbofans.