Technical data
Type	MI-3 ANT-21	MI-3D ANT-21bis
Function	fighter
Year	1933	1934
Crew	3
Engines	2*680hp M-17B	2*830hp M-34N
Wing Span	19.11m	20.76m
Length	12.31m 10.85m?	11.57m
Wing Area	52.10m²	59.20m²
Empty Weight	3412kg	4058kg
Flight Weight	5088kg	5955kg
Maximum Weight	5436kg	5608kg
Wing Load (kg/m²)	97.6	92.2
Speed (0m)	351km/h	285km/h
Speed (5000m)	?	350km/h
Ceiling	7885m	8300m
Range	1120km	?
Armament
Guns	1g20mm 3mg7.62mm

ANT-21bis, A.N.Tupolev

16k b/w MI-3 from History of aircraft construction in the USSR Vol.2 p.9

Twin-engined multi-seat fighter, development of the R-6/ANT-7 reconnaissater. Project started on January 1932 (by some sources - January to March 1931).

The MI-3 was an all-metal monoplane with retractable undercarriage, of stressed-skin construction with partial flush riveting. The engines were copies of the BMW VI.

Only one MI-3 was built. During test flights problems with tailfins resulted in collapse of rudders upper parts. Pilot I.F.Kozlov managed to land the aircraft, cutting away landing gear. Repairs and redesign program began on March 1 1932.

16k b/w MI-3D from History of aircraft construction in the USSR, Vol.2 p.9

Serious design revision produced the MI-3D (D stays for Dublior, the 'spare second one') with a single tailfin. Tail section was 'borrowed' as a whole from DIP-1, machineguns were replaced by 20mm 'Aerlikon'.

The ANT-29 was then already the preferred aircraft, and the ANT-21bis (MI-3D) did not enter production. According to [6](Vol.2 p.10) the preferred aircraft was the SB with better flight performance.

Aircraft is interesting as a transitional design. In the second prototype (MI-3D/ANT-21bis) open cockpits and turrets were replaced by enclosed. Corrugated skin was replaced by smooth one, general aerodynamics was improved.

Predecessors	Modifications
ANT-7 R-6	ANT-29 DIP

References

'History of aircraft construction in the USSR', Vol.2 p.10

More Links...

MI-3, ANT-21
ANT-21, Tupolev
MI-3, Tupolev
MI-3 Page from Emmanuel Gustin Catalog;