Tupolev ANT-21bis (MI-3D)
|FIGHTER||Virtual Aircraft Museum / USSR / Russia / Tupolev|
Retaining the wings, engines and undercarriage of the ANT-21, the ANT-21bis alias MI-3D (the suffix letter indicating dubler, or, literally, "understudy") mated these elements with an entirely new fuselage, which provided enclosed cockpits for all crew members, and a single fin-and-rudder. Completed in April 1934, the ANT-21bis had provision for the same armament as that of the ANT-21, but the ventral tunnel was omitted, the gun being fired instead through a trap. During initial flight trials some tail oscillation at certain power settings led to the introduction of tailplane bracing struts. State acceptance trials were conducted between July and December 1934, but the results were somewhat academic as there was little official interest in an M-17B-powered aircraft which had, in any case, been largely overtaken by the ANT-29. Consequently, further work on the ANT-21bis was discontinued.