The Wittemann-Lewis NBL-1 "Barling Bomber"[1] was an experimental long-range, heavy bomber built for the United States Army Air Service in the early 1920s. Although unsuccessful, it was an early attempt at creating a strategic bomber.

On 22 August 1923, the Barling Bomber made its maiden flight from Wilbur Wright Field in Fairfield, Ohio. At the time, it was comparable in size to the German Riesenflugzeug and Italian Caproni Ca.4 heavy bombers and remains large even by today's standards, however it was severely overbuilt and weighed significantly more than other aircraft at the time of a similar size, to the detriment of its performance.

Although capable of carrying a 5,000 lb (2,300 kg) bomb load, it was soon discovered that the aircraft was seriously underpowered, and performance was disappointing. The overly complex structure of three wings and their accompanying struts and bracing wires created so much drag that the six engines couldn't compensate. Fully loaded, the XNBL-1 had a range of only about 170 mi (270 km) with a top speed of 96 mph (154 km/h). In contrast, the "short-range" Martin NBS-1 had a range of about 450 mi (720 km) and could carry a 2,000 lb (910 kg) payload at the same speed. On a flight from Dayton, Ohio to a scheduled appearance at an airshow in Washington, DC, the Barling Bomber failed to achieve enough height to get over the Appalachian Mountains and had to turn around.[2][3]

A problem with water collecting in the aircraft's wings during rainstorms necessitated the construction of a special hangar at a cost of $700,000. The hangar was constructed in 1925 at the nearby Fairfield Air Depot.[2]
Although the XNBL-1 was not put into production, it had advanced features such as aluminum fuselage components, adjustable[10] multi-wheel undercarriage, separate compartments for crew, a flight engineer, electrical instruments and advanced engine controls. One unusual feature was that the incidence of the tailplane could be adjusted in flight using a lever in the cockpit.[11] The XNBL-1 was the largest aircraft built in the United States until the Boeing XB-15 in 1935.

Although the Barling Bomber was a failure, it introduced the use of large strategic bombers to the US military. Even Gen. "Hap" Arnold, who ordered it destroyed, later stated "if we look at it without bias, certainly [the Barling] had influence on the development of B-17s... and B-29s."