Sikorsky XBLR-3
      
The Sikorsky XBLR-3 was a four-engine bomber, designed in 1935-1936, as a competitor to the Boeing BLR-1 (XB-15) and Douglas BLR-2 (XB-19). The original XBLR-3 concept was a twin boom design with both pusher and tractor propellers and many gun stations; it later evolved into a more conventional four-engined bomber design. The XBLR-3 was the last landplane design prepared by Sikorsky before the company committed itself to helicopters.
References
-  Jones, L. S. (1962). U.S. Bombers B1 - B70. Los Angeles: Aero Publishers. 
-  (Polish)
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