The North American NA-40 was an American prototype

bomber aircraft A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an air ...

developed by

North American Aviation North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the ...

in the late 1930s for evaluation by 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 r ...

. Although unsuccessful, it led directly to the

North American B-25 Mitchell The North American B-25 Mitchell is an American medium bomber that was introduced in 1941 and named in honor of Major General William "Billy" Mitchell, a pioneer of U.S. military aviation. Used by many Allied air forces, the B-25 served in ...

medium bomber.

Design and development

The Air Corps issued a circular (number 38-385) in March 1938 describing the performance they required from the next bombers — a payload of with a range of at more than .Baugher, Joe
"North American NA-40."
''American Military Aircraft: US Bomber Aircraft'', 6 March 2000. Retrieved: 24 May 2015. Several American aircraft companies responded with submissions: Bell Model 9 with two engines, Boeing-Stearman Model X-100 with Pratt & Whitney R-2180 radials, Douglas Model 7B with Pratt & Whitney R-1830 Twin Wasp radials, Martin Model 167F and North American submitted their NA-40 design. The NA-40 had benefited from the

North American XB-21 The North American XB-21 (manufacturer's model designation NA-21) and sometimes referred to by the name "Dragon", was a prototype bomber aircraft developed by North American Aviation in the late 1930s, for evaluation by the United States Army Air ...

(NA-39) of 1936, which was the company's partly successful design for an earlier medium bomber that had been initially accepted and ordered, but then cancelled. However, the company's experience from the XB-21 contributed to the design and development of the NA-40. The single NA-40 built flew first at the end of January 1939. It went through several modifications to correct problems. These improvements included fitting

Wright R-2600 The Wright R-2600 Cyclone 14 (also called Twin Cyclone) is an American radial engine developed by Curtiss-Wright and widely used in aircraft in the 1930s and 1940s. History In 1935, Curtiss-Wright began work on a more powerful version of thei ...

"Twin Cyclone"

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 March 1939, which solved the lack of power. In March 1939, North American delivered the substantially redesigned and improved NA-40 (as NA-40B) to the

for evaluation. It was in competition with other manufacturers' designs produced - the Bell had not been built - Douglas 7B, Stearman XA-21, and the Martin Model 167F but failed to win orders. The aircraft was originally intended to be an attack bomber for export to the United Kingdom and France, both of which had a pressing requirement for such aircraft in the early stages of World War II. Despite the loss of the 7B in an accident injuring a French observer in January, the French had ordered the 7B and a revised version (as the DB-7). Unfortunately, the NA-40B was destroyed in a crash on 11 April 1939 while undergoing testing. Although the crash was not considered due to a fault with the aircraft design, the U.S. Army ordered the DB-7 as the

A-20 Havoc The Douglas A-20 Havoc (company designation DB-7) is an American medium bomber, attack aircraft, night intruder, night fighter, and reconnaissance aircraft of World War II. Designed to meet an Army Air Corps requirement for a bomber, it was o ...

.Parker 2013, pp. 77–79, 83, 88, 92.Borth 1945, pp. 70, 92, 244. The Air Corps issued a specification for a medium bomber in March 1939 that was capable of carrying a payload of over at NAA used the NA-40B design to develop the NA-62, which competed for the medium bomber contract. No YB-25 was available for prototype service tests. In September 1939, the Air Corps ordered the NA-62 into production as the B-25, along with the other new Air Corps medium bomber, the

Martin B-26 Marauder The Martin B-26 Marauder is an American twin-engined medium bomber that saw extensive service during World War II. The B-26 was built at two locations: Baltimore, Maryland, and Omaha, Nebraska, by the Glenn L. Martin Company. First used in t ...

"off the drawing board".

Variants

North American NA-40 prototype NX14221 side

;NA-40 :A twin-engined, five-seat bomber to meet 1938 USAAF requirement for an attack bomber, it was powered by two

Pratt & Whitney R-1830 The Pratt & Whitney R-1830 Twin Wasp is an American air-cooled radial aircraft engine. It displaces and its bore and stroke are both . The design traces its history to 1929 experiments at Pratt & Whitney on twin-row designs. Production be ...

-56C3G radials. Wingspan was 66 ft (20.12 m), and length 48 ft 3 in (14.71 m). First flown on 29 January 1939, it proved to be underpowered and unstable.Dorr ''Wings of Fame'' Volume 3, p. 124."North American"
''Aerofiles'', 2009. Retrieved: 12 December 2011. ;NA-40B :The NA-40B (also known as the NA-40-2) was a modification of the NA-40 prototype with two Wright R-2600-A71-3 radials and numerous minor changes. It first flew in revised form on 1 March 1939, but crashed on 11 April 1940. ;NA-40-3 through NA-40-7 :Proposed export versions, not built.

Specifications (NA-40B)

References

Notes

Bibliography

* Borth, Christy. ''Masters of Mass Production''. Indianapolis, Indiana: Bobbs-Merrill Co., 1945. * Donald, David, ed. ''The Complete Encyclopedia of World Aircraft''. London: Orbis, 1997. . * Dorr, Robert F. "North American B-25 Variant Briefing". ''Wings of Fame'', Volume 3, 1996. London: Aerospace Publishing. . . pp. 118–141. * Jones, Lloyd S. ''U.S. Bombers, B1-B70''. Fallbrook, California: Aero Publishers, 1962. . * Norton, Bill. ''American Bomber Aircraft Development in World War 2.'' Hersham, Surrey, UK: Midland Publishing, 2012. . * Parker, Dana T. ''Building Victory: Aircraft Manufacturing in the Los Angeles Area in World War II''. Cypress, California: Dana Parker Enterprises, 2013. . * Reuter, Claus. ''Development of Aircraft Turrets in the AAF, 1917–1944''. New York: S.R. Research & Publishing, 2000. . * Rusinek, Ed
"A Tale of Two Dragons."
''North American Aviation Retirees Bulletin'', Winter 2005. * Yenne, Bill. ''The American Aircraft Factory in World War II''. St. Paul, Minnesota: Zenith Press, 2006. .

External links

{{North American Aviation aircraft 1930s United States bomber aircraft NA-40 Aircraft first flown in 1939 Mid-wing aircraft Twin piston-engined tractor aircraft