Sundog said:
You can also find more in the book on the YF-17 as well.
However, I stand by my earlier comments as the YF-17 wasn't actually that different from the final Cobra designs, which were completed before the LWF program began. As I said in my previous post, though it would have been more accurate to say the Cobra, rather than the YF-17, partly lead to the creation of the LWF program. Although I'm sure, as most of these things are, it was a combination result of the USAF people, not just Boyd, who thought there should be a LWF, and Northrop actively having that in their mind as well as the Cobra was developed. I'll have to go back and find Lee Begin's interview by Braybrook from Air International to see if there was more information in there.
Though, to that end, I've never seen/read any definitive information on why they went with the twin engined design as opposed to the F-100 powered variant. Also, I haven't seen any definitive info that they used Boyd's work in the development of the YF-17. I'm not saying they didn't, but you always read about the connections between Boyd and Widmer, bot not Begin/Fellers. I'm not saying they not out there, but if you guys have some references I would like to see them. It seems to me that Northrop used high AOA more as a design criterion than Ps.
While the F-X requirement was slimmed down under Boyd's influence from a tubby 60,000lb to 40,000lb, Sprey & Boyd were convinced it was still too large and that their studies showed a design under 25,000lb to be optimal - which they dubbed F-XX or "FX squared". Sprey validated his analysis with Northrop and General Dynamics. Northrop were already well advanced on the design of the P-530 while General Dynamics had worked on single engine and smaller size F-X designs. By late 1968, both companies had validated the F-XX concept. In June 1969, Sprey's paper "F-XX and VF-XX - Feasible High Performance Low Cost Fighter Alternatives" used the Northrop N-700 P-530 variant [perhaps N310 / P700?] and General Dynamics FX-404 designs to substantiate their work. Riccioni's "Falcon Brief" in 1971 used the Boeing 909-618, Northrop N314-2 (another P-530 version), and a General Dynamics 401(?) design [Stevenson gives FW71-274-VG1369 which is a drawing number not a model number] to illustrate his concepts. So Northrop were on board from the very beginning of LWF.
The P-530 started life as N-300, an advanced F-5 design, with twin engines. It was aimed as an F-5 and F-104 replacement. As the design evolved through N-300 versions, P-530, P-530-2, P-530-3, its size increased, these twinengines were single spool, high T/W J97(GE1/J1A1) turbojets (8,000lb), then its development the GE1/J1A2 (10,000lb), then this was replaced by the GE15/J1A5 (initally 13,000lb, then 14,300lb)
twin spool "leaky turbojet", which become the J101. Northrop were convinced they could sell P-530 as an F-104 replacement to various NATO countries including West Germany and the Netherlands.
The LWF program represented a great chance for Northrop to build a demonstrator for their P-530 design. Unfortunately for Northrop, as LWF finalised a consensus was developing around 20,000lb and a single F100 (e.g. General Dynamics, Boeing, LTV). P-530 was larger, 25,000-27,000lb. Northrop still had its eye firmly on the NATO nations and felt P-530's larger size and twin engines were right for this market. Neither Northrop nor General Dynamics had the benefit of hindsight to know they were in fact playing for a huge USAF acquisition as well as foreign sales, so the engine commonality factor was not a big consideration - noone minded buying J85 engines for their F-5s. The J101 engine bypass ratio was also more optimal for an air-air fighter mission and it was simpler and less challenging in terms of pressure ratio than F100. Also Northrop & GE had close relationships from F-5 days and had worked long and hard on matching the airframe, intakes and engines, work that would be lost by switching to F100. The P-610 was Northrop's attempt to leverage the P-530 work into a lighter weight F100 powered design, but its designer Bill Roth died of a heart attack before finalising it, and it was never accorded the same importance as the P-530 derived P-600. It threatened to invalidate the years of work put into the P-530. Apparently P-610 was submitted mostly at the insistence of Sprey & Boyd.
