North American XB-21 - Testing and Evaluation

Testing and Evaluation

Undertaking its maiden flight on 22 December 1936 at Mines Field, company test flying indicated a number of minor problems. Modifications resolving these resulted in the aircraft being re-designated NA-39, and, accepted by the U.S. 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.

During the course of the fly-off, the gun turrets proved troublesome, their drive motors proving to be underpowered, and issues with wind blast through the gun slots were also encountered. As a result of these problems, the XB-21's nose turret was faired over, while the dorsal turret was removed.

The XB-21 proved to have superior performance over its competitor, but price became the primary factor distinguishing the Bolo and the XB-21. On this account, the modified B-18 was declared the winner of the competition, Douglas quoting a price per aircraft of $64,000 USD, while North American's estimate was $122,000 USD per aircraft, and an order was placed for 177 of the Douglas aircraft, to be designated B-18A.

Despite this, the 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. 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. Operated by North American Aviation, the XB-21 served as a research aircraft until its retirement.

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