The revised design retained the MDR-3's hull, but added a newly designed, full-cantilever wing, a new tail, and a new engine installation featuring two tractor and one pusher unit.
Trials began in March 1934 but the prototype was destroyed during one takeoff.
A second prototype was constructed the following year, and redesignated MTB-1 to reflect a new torpedo-carrying role.
Despite its poor performance in trials, the aircraft was urgently needed to fill a niche in the Soviet Navy, and it was accepted for production before flight testing was complete.
[1] Data from The Osprey Encyclopaedia of Russian Aircraft 1875–1995[1]General characteristics Performance Armament