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Post by darrenvox on Dec 21, 2017 5:04:02 GMT
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Post by Tony Madge - HJG on Dec 21, 2017 7:00:32 GMT
Ex N707UM to prototype YE-8B. Went on to Saudi Air Force as 1902, as a E-3 Sentry  |
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Post by aerofoto - HJG Admin on Dec 21, 2017 8:07:55 GMT
Tony's "on to it" .... and there's nothing confusing about it really There was only ever a single B707 temporarily designated as a -700 (N707QT .... built as a -320C during late 1979 .... and the last 320C ever produced by BOEING) .... and which was equipped with CFM-56 turfan engines. It only retained its -700 designation for the duration of its participation in the CFM-56 engine flight testing program from November 1979 .... if that's what's possibly confusing him. Beyond its brief CFM flight testing sojourn it was again re-engined and defaulted back to P&W JT3D fanjet power and its original B707-320C designation .... and was eventually sold to the Government Of Morocco during March 1982. A number of ex-civil B707-300 series aircraft were later acquired for military use and re-engined with CFM power .... and took on military aircraft type designations as Tony hints was the case with this particular aircraft. Mark C AKL/NZ |
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Post by christrott on Dec 21, 2017 10:19:31 GMT
To me what is even more interesting is that when put into "production", none of the E-8 JSTARS received CFMs. Instead, they all retained their original JT3Ds because the USAF had decided it wanted to maintain them as part of the E-3 Sentry logistics pipeline instead of part of the KC-135/E-6 TACAMO pipeline. There was much headscratching on that one.
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Post by darrenvox on Dec 21, 2017 16:29:50 GMT
Or someone had uploaded the photo with wrong aircraft type but no jstars were made with cfm engines... I get that most 707s are now military but not the 700 of the 300 model range Could be a chance it was in the middle of turning into kc-135 with cfm engines but hadn't been changed over because sure they ate kc-135 and such, the base model as you say tony or whoever us that it's based on 707-300/320/320c etc Like this one perhaps  |
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Post by Peter Liddell - HJG Admin on Dec 21, 2017 16:43:54 GMT
Thats a 707/xC-137 not a xC-135 frame though... you can tell the fuselage is too round for a 135. Here's a 135 similar angle, see how the fuselage sides look a bit "flat"? www.scottfieldairpark.org/images2/KC-135Lg.jpgEasy way to tell the 2 apart but far from the only or best way! |
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Post by christrott on Dec 21, 2017 17:15:50 GMT
Darren, both of your pictures are of the same airplane. The E-6/YE-8B was the test platform for what became the E-6 Mercury (TACAMO) and the E-8C JSTARS. The airframe was a former civil 707-320C (don't remember which operator off hand and can't be arsed to look it up right now) which had the CFM-56 proposed for both aircraft installed on it. The specific aircraft in both of your pictures above was completed as a RE-3A for the Royal Saudi Air Force. The RE-3A is a hybrid of the JSTARS idea and the RC-135 Rivet Joint SIGINT system. www.airliners.net/photo/Saudi-Arabia-Air-Force/Boeing-RE-3A-707-300/1724590 |
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Post by darrenvox on Dec 21, 2017 18:15:30 GMT
Ok that confirms it...
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Deleted
Deleted Member
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Post by Deleted on Jan 8, 2018 21:00:55 GMT
Too bad more companies didn’t convert their 707’s into these CFM powered versions... Several did with DC-8-61’s through the -63’s. I remember making a few “fictional” liveries with this idea in mind way back when I got into HJG and flight simming.
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Post by christrott on Jan 8, 2018 22:34:56 GMT
110 of the 262 DC-8 "Super 60" series aircraft were converted, so it's not just "several". It's nearly half.  The reason it was done was simple - there were no major modifications required to do it. The modifications needed to the 707 weren't great, but Boeing was concerned with a re-engine program taking sales away from its nascent 757 - the replacement for the 707. Douglas wasn't concerned with that. They weren't replacing the DC-8, so they wanted to keep them flying as long as possible. |
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Post by aerofoto - HJG Admin on Jan 9, 2018 1:35:27 GMT
I can clearly remember an article within a 1978 issue of FLIGHT INTERNATIONAL magazine .... to the effect of "a version of the B707 modified beyond the 320C" being mooted back then, but, I don't think it was ever a serious proposition given the generation of technology the B707 by this time represented and the fact BOEING, and airline interest, were both rapidly gearing up towards the far more advanced and economic B757-200 and B767-200 .... as Chris implies. I can even just as clearly remember a particular editorial response to this particular article which read something like .... "is that the best BOEING can offer" .... and how the aircraft would need .... "revised air-conditioning as well as revised this, that, and the other thing too" Only 1 civil B707 airframe was ever modified with CFM-56 turbofan engines .... the last B707-320C ever produced .... and which, upon its completion, was only temporarily CFM powered and branded as "B707-700", then used to certify these new engines between 1979 and 1981, but, upon completion of this flight test/certification program it was reverted back to P&W JT3D fanjet engines and was eventually sold to Government Of Morocco during 1982 .... I think I mentioned that earlier within this thread. As Chris implies .... there were a number of technical factors which limited the practical and economic conversion of B707-320B/C airframes to CFM-56 power .... in so far as these being a contender for a major re-engining program (like that which really benefitted the DC-8-61/-62/and -63) is concerned. One of these limiting factors was the B707's ground clearance being much less than that of the DC-8 (the DC-8 was not only designed with superior ground clearance but was also cantered down slightly, at the nose, and which increased ground clearance of these aircraft at the tail as they were stretched .... whereas the B707 design was not so adaptable to this same stretching process). The B707's lack of ground clearance also made the CFM-56 engines very succeptable to nacelle strike during crosswind landings as well FOD damage too (in military use the engines of most CFM-56 powered C-135 TYPE aircraft lack thrust reversers partly for this reason .... although similar ground clearance issues must also apply to the CFM powered B737-300/400/500 aircraft too). Another limiting factor was the wings on the B707 and DC-8 required strengthening and both aircraft also required new engine pylons too ... at "MAJOR" development cost .... but .... to more comfortably resolve the B707's lack of ground clearance would also required longer legs to be developed as well .... at further "MAJOR" cost .... and which is precisely what "civil operators don't want". For these reasons the CFM-56 re-engining program best suited/favored the DC-8 .... and because the DC-8-61 and 63 (some, but, not many 62's were also re-engined) were a much better proposition for freighter conversion due to their larger size and greater volumetric capacity and associated profitability over that of B707 freighters .... despite the B707 being as good as it is/"WAS". Mark C AKL/NZ P.S. I'm tied up with (enjoyable) real world CAA related priorities at the moment .... and may be for most of the remainder of month, so, will appear here "when I can". |
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Post by darrenvox on Jan 9, 2018 3:28:31 GMT
Thanks I think we solved this...but if there is more info or other planes this happened to, please keep posting
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Post by aerofoto - HJG Admin on Jan 9, 2018 11:37:34 GMT
UMMM .... what myself, and Chris too .... I believe, are responding to is in relation to "CGOLD's" commentary rather than further responding the actual thread topic. No problem .... just evidence of the twists'n'turns threads often take as they advance Mark C AKL/NZ |
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Post by darrenvox on Jan 9, 2018 17:37:16 GMT
Interesting isn't it...
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The reason it was done was simple - there were no major modifications required to do it. The modifications needed to the 707 weren't great, but Boeing was concerned with a re-engine program taking sales away from its nascent 757 - the replacement for the 707. Douglas wasn't concerned with that. They weren't replacing the DC-8, so they wanted to keep them flying as long as possible.