Sikorsky XBLR-3
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Here is a link tro page in what I believe is Czech describing the XBLR-3. http://www.samoloty.ow.pl/str344.htm The source, L. S. Jones "U.S. Bombers B1 - B70", Aero Publishers, Los Angeles, 1962, is long out of print although I recall reading it at the Boston Public Library in the 1990s. Every project described in that book that was not actually constructed was illustrated with a model and I believe the images that you have up for the XB-30 and XB-31 are from Jones' book. The model shown on the site is a later version of the proposal. If I recall correctly, the original XBLR-3 was a twin boom design with both pusher and tractor propellers and bristling with gun stations which made it look like the aircraft illustrated in popular comics and pulp fiction of the time. Sikorsky was apparently not all that committed to building the machine. Experimental military aircraft of the period had to be developed at the contractors expense. Cost-plus contracts were a product of the rearmament programs of the 1940s.