The Stal-MAI (also called the RD-MAI) was a long-range experimental aircraft developed by the Moscow Aviation Institute under the supervision of Dmitry Grigorovich and later Pyotr Grushin. It first flew on 19 September 1934.
In December 1931 the government made the decision to build the Tupolev ANT-25 long-range aircraft. At the same time there was a need for an aircraft with a range of . In late 1931, Grigorovich, then the new director of the Moscow Aviation Institute (MAI), organized a group of students to design an aircraft of this type, among them Pyotr Grushin and Mikhail Pashinin. Grigorovich was focused on his cannon fighters and supervision later passed on to Grushin. The aircraft was completed in the mid 1934 and first flown on 19 September 1934. The aircraft was repaired but the project was discontinued.
The Stal-MAI was a low-wing cantilever monoplane with a two-spar trapezoidal wing and a braced empennage. It was powered by a single Mikulin M-34R liquid-cooled V12 engine equipped with a gearbox driving a variable-pitch propeller. The retractable landing gear was operated manually. The two-seat cockpit was enclosed by a single canopy. Except for the fabric-skinned control surfaces, the aircraft was made of steel. The Stal-MAI was among the first aircraft in the world to be constructed mainly out of steel.