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Post by kat on Feb 16, 2014 8:56:40 GMT -5
From the University of Washington's Aeronautical Laboratory in Seattle. www.uwal.org/multimedia/historical.htmObviously not an unbuilt project exactly but perhaps the final development stages between North American's NA-40B and the NA-62. The first (1939) shows a NA-62 model with undercarriage down. The model looks much like the first production B-25s except for the vertical tails. These surfaces have the outline and higher position of the NA-40 tails. Rudder shape is generally like that of the NA-40 but lacks the aerodynamic balance (à la the NA-62). I include shots of the vertical tails of both the NA-62 (L) and NA-40B (R). The second series show different approaches to the horizontal tail surfaces (the vertical tails appear to have the same proportions as those on the u/c down model). On the left (1939), the horizontal surfaces are flat (and the wings are of constant dihedral). In the centre (1940), the horizontal surfaces have dihedral applied. On the right (1940), the horizontal surfaces are dihedraled and the vertical tails are also canted. On the right, note also that dihedral has been eliminated from the outer wing panels (as per the tenth production B-25). BTW: all these wind tunnel models models are identified as "Boeing B-25" Finally comes the "North American Aviation XB-2B [sic] Pressurized Medium Bomber (1940)". Is it me or does this NA-63 have twin tails?
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Post by msapple on Feb 16, 2014 9:18:00 GMT -5
"North American Aviation XB-2B [sic] Pressurized Medium Bomber (1940)" should probably read as the XB-28 which fit the decription and photo - IIRC both single and twin tails were considered before settling on a single fin. Please see: www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2526
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Post by fr33dom on Feb 18, 2014 14:43:43 GMT -5
I was cruising through some material in the Kuter papers at AFHRA today and came across North American's response to Air Corps Circular Proposal 39-640 (11 March 1939 w/3 amendments) dated 5 June 1939. The cognoscenti will recognize that proposal as the genesis of the B-25 Mitchell bomber, but NAA's response, Report NA-639, includes some surprises. North American examined multiple variations of what it called P442 (P for Project?) prior to the contract award. The familiar twin-tailed B-25 only first appeared as model P442-41. Wanna see what came earlier? Here's P442-17:
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