Y1B-17 Flying Fortress

The Y1B‑17 Flying Fortress was Boeing’s first prototype of the legendary B‑17 bomber, rolled out in 1935 as the United States Army Air Corps sought a long‑range, high‑altitude strategic aircraft. Design work began in 1934, and the prototype, serial number 37‑123, first flew on 14 July 1935 under the command of test pilot Howard D.“Hap” Arnold. Featuring an all‑metal monocoque fuselage, four Wright R‑1820‑25 radial engines delivering 1,050 hp each, and a tapered wing with a 103‑foot span, the Y1B‑17 demonstrated unprecedented range of 2,000 miles and a service ceiling above 30,000 feet. Its armament was initially modest—a pair of .30‑caliber machine guns—but the prototype’s modular gun‑mount concept paved the way for the later B‑17G version, which carried up to thirteen .50‑caliber guns and a bomb load of 8,000 pounds. The Y1B‑17’s successful trials proved the viability of a heavy, four‑engine bomber and set the standard for American strategic air power during World War II. Its influence extended to post‑war aircraft design, establishing engineering practices for pressurization, defensive fire control, and long‑range navigation that remain foundational in modern aviation. Today, museums around the world preserve the legacy of the Y1B‑17, inspiring new generations of aviators and engineers.

Boeing

Y1B-17 Flying Fortress

Classification

Design & Classification