Boeing's B-17 has been likened to a flying work of industrial art and there is no doubt that it remains a symbol of American ingenuity and the bravery of those who fought in WWII. Still, sometimes something thought of as visually close to perfection can be improved upon, and the XB-38 variant of the Flying Fortress did just that.

The XB-38 was a cooperative project between Boeing and Lockheed's 'Vega' subsidiary. The concept saw the ninth B-17E ever built converted for testing purposes, with its radial engines removed and inline engines installed in their place. Extra fuel was also added to the XB-38 and its three bladed propellers that were capable of full feathering. What resulted was a sleeker looking B-17 that had a slightly higher top speed and range.

Beyond potential performance improvements, the project was aimed at proving a fallback configuration for the B-17 should the become scarce as production continued to accelerate as the war progressed. The Allison 1710 inline water-cooled V-12s were also used in the P-39, P-40 and P-38, but were not in the same demand category as the Wright R-1820 Cyclone series which were used on so many essential combat aircraft of the time period.

The XB-38 first flew on May 19, 1943 and the bomber was almost immediately stricken with leaking exhaust manifold joints. The issue was fixed and the aircraft resumed test flights without a problem. Then, on June 16, 1943, only the aircraft's ninth flight, a fire erupted on the XB-38's number three engine. The test crew ran through every checklist available to extinguish the fire, but nothing worked. They decided to bail out of the fuel-laden bomber before the fire could spread to its main fuel tanks. The XB-38 was a total loss, and the project was cancelled as another set of V-1710 engines were needed for more pressing test projects.

Although the XB-38 was a failure, it did prove that the inline engine design worked for the B-17 without adverse aerodynamic or performance issues. It also gave us one of the most beautiful flying machines of its day and what many see as the most visually elegant bomber design of the entire war.