12/31/2007. Built as a Model 450-11-10 B-47B this aircraft was one of two converted to the Model 450-162-48 XB-47D test bed for the Wright YT49-W-1 turboprop engine. Two turboprops replaced the four paired inboard jets. The first XB-47D flew for the first time on August 26, 1955, and the aircraft's performance was comparable to that of a conventional B-47. View also photo 9289.