10/31/2010. Two Model 450-67-27 B-47Bs (s/n 51-2046, 51-2103) were converted to XB-47D to serve as test beds for the Wright YT-49-W-1 turbo-prop engines. One of these was installed in place of the paired J-47s in each inboard nacelle. The outboard J-47-GE-23 jets were retained. To absorb the equivalent 9,710 shp of the T-49, four extremely wide blades were used on the 15 ft (4.57 m) diameter propellers. No armament was fitted.
Empty weight was 79,800 lb (36,197 kg), and take-off gross weight was 184,428 lb (83,655 kg). Maximum speed was 597 mph (961 kmh) at 13,500 ft (4,115 m), the fastest achieved in level flight by a propeller-driven aircraft, and service ceiling was 33,750 ft (10,287 m). Rate of climb at normal power was 2,910 ft (887 m)/min. The first XB-47D to fly was 51-2013, on August 26, 1955, the second (pictured above), with minor revisions and designated Model 450-162-49, first flew February 15, 1956.