SPB, D, D-3 by N.N.Polikarpov

fter 1936- 1939 flight tests of VIT-1 and VIT-2 multi-purpose aircraft, N.N.Polikarpov bureau came up with high speed dive bomber SPB. Despite similar in appearance to its predecessors, this aircraft had all new design with old-fashion wielded tube frames (etc.) were replaced by more recent technologies. The maiden flight (B.N.Kudrin) took place on February 18, 1940. Except two experimental aircraft, small series of three SPB were harried into production before tests were finished (Factory 22).

SPB during flight tests
From article in the Air Force Herald magazine.

Tests were not easy. Numerous modifications were introduced to fix shortcomings in stability, engine cooling system and frame strength. On April 27, 1940 second production aircraft fell into flat spin and crushed, killing test pilot N.P.Golovin and two crewmembers. On July 20 another (first one) production aircraft crushed, killing crew lead by test pilot M.A.Lipkin.

SPB goes to the Wind Tunnel
From article in the Air Force Herald magazine.

Despite hard working task force failed to reveal cause of the last crash flight tests were suspended. According to [6] Vol.2 p.23 it was flatter (pilot pushed aircraft to higher dive speeds too fast, plus the weight compensation of ailerons was not installed). On third aircraft one of tail fins was broken, but B.N.Kudrin managed to land it safely. He refused to continue the tests...

It was planned to return to flights after tests in the T-101 TsAGI full-size wind tunnel and detailed expertise of frame strength. Tunnel tests were completed at the end of 1940, but time was lost.

The PB-100 (future Pe-2) was ready for production, and the story of SPB was over.

Floatplane version (expected speed 435km/h) with reversible propellers was also cancelled.