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Boeing YB-40 Flying Fortress

1943 WORLD WAR 2 X-PLANE

History of the Boeing YB-40 Flying Fortress

Like other classic aircraft of the WWII era (1939-1945), the Boeing B-17 Flying Fortress heavy bomber was the subject of many experiments and modification projects during its service. The YB-40 was developed as one of the former to present the B-17 as a flying "gun car" to protect bomber formations in and out of enemy targets.

The program was not a complete success, but produced some 25 prototypes by the end and influenced several important future changes to the B-17 production line.

Before the advent of long-range escort fighters such as the North American P-51 Mustang and the Republic P-47 Thunderbolt, consideration was given to equipping bombers with additional machine guns, proper magazines and enhanced armor protection to help them act as formation escorts. The aircraft were designed to escort large U.S. bomber formations over enemy airspace, provide point defense for intercepting enemy fighter jets, and return to formation after reducing the war load on enemy targets below.

The B-17 seems like a good place to start, it's a proven player, and it delivers in the quantities needed.

The aircraft was delivered to England in May 1943 (one was lost in a forced landing in Scotland), and from then until July of the same year, it performed combat-level missions for the US Air Force. The results were not entirely impressive, with the fleet gaining only five enemy fighters out of 48 missions. The added weight of the armor plates and mounted weapons meant that once the bombers abandoned their war load, these defenders could not keep up with the main bomber force.

The test program concluded with the last operational flight on July 29, 1943, when two XB-40s attacked the Kiel submarine bunker.

After completing operational service, the stock was returned to the United States and participated in crew training as "TB-40". All were scrapped before the war ended in 1945.

The XB-40 was not completely lost, as it introduced several key features of future B-17 generations - namely the Bendix chin turret (which proved crucial in defending against oncoming XB-40 attacks ahead ) and staggered emplacements. Work on the XB-40 also improved the rear gunner's position, increasing visibility for better tracking and engagement of fast-moving targets.

When finished, the YB-40 has a top speed of 292 mph and a cruising speed of 195 mph. Range is 2,260 miles and service is capped at 29,200 feet. Power comes from four Wright R-1820-65 turbocharged radial-piston air-cooled engines, each producing 1,200 horsepower.