Boeing XB-38 Flying Fortress

The XB-38 Flying Fortress was a single conversion of a production B-17E Flying Fortress, built to test whether the Allison V-1710 V-type engine could replace the standard Wright R-1820 radial engine during early World War II. Vega, a Lockheed subsidiary, fitted a B-17 with liquid-cooled Allison V-1710-89 V-12 engines as an alternative in case the air-cooled radials became scarce. The modifications took less than a year and the XB-38 first flew on 19 May 1943. It had a higher top speed but a lower ceiling, was grounded after a few flights by exhaust leaks from the engine manifolds, and on its ninth flight, on 16 June 1943, the inboard starboard engine caught fire and the crew bailed out. The aircraft was destroyed and the project cancelled, partly because the V-1710 was in demand for fighters.