The Martin XB-16, company designation Model 145, was a projected heavy bomber designed in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

during the 1930s.

Design and development

The XB-16 was designed to meet the

United States Army Air Corps The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical ri ...

(USAAC) request for a bomber that could carry of bombs . The XB-16 (Model 145A) was to use four

Allison V-1710 The Allison V-1710 aircraft engine designed and produced by the Allison Engine Company was the only US-developed V-12 liquid-cooled engine to see service during World War II. Versions with a turbocharger gave excellent performance at hig ...

liquid-cooled reciprocating

V-engine A V engine, sometimes called a Vee engine, is a common configuration for internal combustion engines. It consists of two cylinder banks—usually with the same number of cylinders in each bank—connected to a common crankshaft. These cylinder ba ...

s; contemporary American aircraft used air-cooled

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

s. In

1935 Events January * January 7 – Italian premier Benito Mussolini and French Foreign Minister Pierre Laval conclude an agreement, in which each power agrees not to oppose the other's colonial claims. * January 12 – Amelia Earhart bec ...

, Martin revised the XB-16 design as the Model 145B. The wingspan was increased from to , and a set of V-1710 engines added to the trailing edge. This version had a wingspan 20% greater than that of the

B-29 Superfortress The Boeing B-29 Superfortress is an American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United S