XB-21 | |
---|---|
Role | Medium bomber |
National origin | United States |
Manufacturer | North American Aviation |
First flight | 22 December 1936 |
Primary user | United States Army Air Corps |
Number built | 1 |
Developed into | North American NA-40 |
The North American XB-21 (manufacturer's model designation NA-21) [1] and sometimes referred to by the name "Dragon", [2] was a prototype bomber aircraft developed by North American Aviation in the late 1930s, for evaluation by the United States Army Air Corps. Evaluated against the Douglas B-18 Bolo, it was found to be considerably more expensive than the rival aircraft, and despite the ordering of a small number of evaluation aircraft, only the prototype was ever built.
North American Aviation's first twin-engined military aircraft, [3] the NA-21 prototype was constructed at North American's factory in Inglewood, California, [4] where work on the aircraft began in early 1936. [5] The NA-21 was a mid-wing monoplane of all-metal construction, powered by two Pratt & Whitney R-2180-A Twin Hornet radial engines, [5] which were fitted with turbosuperchargers for increased high-altitude performance. [4]
Flown by a crew of six to eight men, [1] the XB-21 featured a remarkably strong defensive armament for the time, [4] including as many as five .30-calibre M1919 machine guns. [1] These were planned to be fitted in hydraulically powered [6] nose and dorsal turrets, in addition to manually operated weapons installed in waist and ventral positions. [4] Up to 10,000 pounds (4,500 kg) of bombs could be carried in an internal bomb bay, with 2,200 pounds (1,000 kg) of bombs being able to be carried over a range of 1,900 miles (3,100 km). [4]
Undertaking its maiden flight on 22 December 1936 at Mines Field in Los Angeles, test flights indicated a number of minor problems. [7] Modifications resolving these resulted in the aircraft being re-designated NA-39, and, accepted by the US Army Air Corps as the XB-21. The aircraft, which had been assigned the serial number 38-485, was evaluated early the following year in competition against a similar design by Douglas Aircraft, an improved version of the company's successful B-18 Bolo. [1]
During the course of flight testing, the gun turrets proved troublesome, their drive motors proving to be underpowered, and issues with wind blast through the gun slots were also encountered. [6] As a result of these problems, the XB-21's nose turret was faired over, while the dorsal turret was removed. [1]
The XB-21 proved to have superior performance over its competitor, [7] but price became the primary factor distinguishing the Bolo and the XB-21. [5] On this account, the modified B-18 was declared the winner of the competition, Douglas quoting a price per aircraft of US$64,000, while North American's estimate was US$122,000 per aircraft, and an order was placed for 177 of the Douglas aircraft, to be designated B-18A. [5] [1]
Despite this, the US Army Air Corps found the performance of the XB-21 to have been favorable enough to order five pre-production aircraft, to be designated YB-21. [1] However, soon after this contract was awarded, it was cancelled, and none of the YB-21s were ever built, leaving the XB-21 as the sole example of the type ever constructed. [1] Operated by North American Aviation, the XB-21 served as a research aircraft until its retirement. [3]
Although the XB-21 failed to win a production contract, it was the first of a long line of North American Aviation medium bomber aircraft, and provided experience and knowledge that assisted in the development of the North American NA-40, [8] which, developed into the B-25 Mitchell, would become one of the Army's standard medium bombers of World War II. [9]
General characteristics
Performance
Armament
Related development
Aircraft of comparable role, configuration, and era
Related lists
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