The immediate ancestor: SB-MMN
by Massimo Tessitori
file updated on April 10, 2005                                file name: mmn.html
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In the beginning of 1940, the Archangelskiy construction bureau  in Zavod 22 aircraft factory worked hard on a perfectioning of the Tupolev SB bomber.
Two steps of development were taken in consideration:

Production tests and operational development proceeded with SB No. 18/206, using motors M-103 with TK-2 turbosuperchargers.
Zavod 22 was charged to build 3 SB with M-105 TK-2 engines within September 1940, but they found difficulties, and build only two SB-2-M105TK2 that failed to pass factory tests. One of them was later delivered to NII-VVS (The Scientific Institute of Air Force) for tests.


To improve the aerodynamics of SB, a new prototype was built. 
This was the MMN (modified smaller lifting surface).


It featured:
  • new smaller  outer wing panels of simplified construction, with a 18.00 m span (instead than 20.33 m) and an area of 48.2 sqm  (instead than 56.7 sqm);
  • with two further 205 l tanks in the outer wing panels;
  • a redesigned nose with wider trasparent surfaces and one ShKAS machine gun (instead of two);
  • 2xM-105 engines of 2x1050 hp (instead than 2xM-103 of 2x960 hp);
  • VISh-2E 3-blade propellers with starter dog and modified cowling;
  • dual controls installed on the navigator's cabin;
  • a dorsal MV-3 turret (instead than TUR-9) with one ShKAS 7.62 mm machine gun;
  • a ventral MV-2 turret with a ShKAS  replaced the LU hatch mounting;
  • much enlarged flaps;
  • a lowered vertical tail unit;
  • a landing light in the leading edge of each wing;
  • an emergency undercarriage extension system was installed in the cockpit.
In spite of all these efforts, the improvement in performances over the SB M-103 was neglegible and fully unsatisfactory, while the landing speed increased to 160 km/h. 
The defensive armament was weaker than that of SB.
The prototype was tested in September 1939 by NII VVS.
On the whole, the result was deluding, and the only prototype, called Shchuka (pike) was allocated to Aeroflot.
However, the State Commission recommanded that many of the new characteristics of the SB-MMN should have been introduced in the production of SB bombers.

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