I've always wondered why they picked the P-63 for swept wing testing. I always thought they used the wrong aircraft. I've got a project of using the L-39 wings and attaching them to a Ryan Fireball. I'm putting a R-2800 on the front, stretching the fuselage some, and other things ---
Cool-sounding project
Your concept has powerplant similarities with Grumman's G-57 design study - 1 x R-2800 + 1 x Halford H.1 (later DH
Goblin) turbojet.
The BuAer looked at a number of swept-winged research aircraft proposals. AFAIK, none of them came from Ryan. Grumman submitted two concepts - one a
Wildcat with new swept wing panels; the second a completely new design (the G-77). [1] I'm rather surprised that the BuAer didn't choose the modified
Wildcat - its retractable undercarriage would give the option of relatively high-speed wing testing as well.
That the BuAer didn't accept Grumman's F4F-based proposal suggests that their choice was based on available design staff time and shop floor space. Grumman was, of course, occupied with getting production
Bearcats into service. Had Ryan actually submitted a swept-wing proposal, I suspect they'd have been told to focus on fixing the XFR-1's problems first - like making sure that the wings didn't fall off anymore!
Weirdly, the Bell Model 39 used modified P-63 outer wing components somehow rearranged into that swept form. The
Kingcobra also had the advantage of having a really narrow centre section - maximizing how much swept span you got. By comparison, the FR-1 had a much wider centre section. That wouldn't stop you from applying sweep to the Ryan's outer wing panels but with a reduced swept span. Of course, your whif gets around that if you adopted the entire L-39 wings
The
Kingcobra fuselage break point also proved fortuitous when the L-39's tail moment arm was found wanting. The FR-1 had a similar construction break but any rear fuselage extension would be somewhat complicated by that break being linked to turbojet engine access. Again, with your whif, the R-2800 would balance c/g for any rear fuselage extensions required.
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[1] The low-winged G-77 was to have ground-adjustable wing-sweep angle (kind of like the Messerschmitt P.1101 jet). It would have been powered by a modest 450 hp P&W R-985. I'm not sure about the model number of the swept-wing F4F proposal. Since the full-span flap
Wildcat was the G-53, I'd guess that the swept-wing modified F4F proposal Model number was in the 54-to-57 range.