In 1934-1935 Chyetverikov designed and built a light flying boat in two versions: OSGA-101 - deck-based aircraft, and SPL – a folding aircraft for a submarine.
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Unemployedin 1933, Chyetverikov turned to the division for design for gliders and propeller-driven sleighs (OSGA) of NII GVF(Naoochno-Issledovatel'skiy Institoot Grazdahnskovo Vozdooshnovo Flota - scientific test institute for civil air fleet) with the proposal for creation of aircraft for the submarines (SPL and Hydro-1).
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With the departure of Richard, KB MOS was transferred to TsKB (Tsentrahl'noye konstrooktorskoye byuro - central construction bureau) TsAGI (Tsentrahl'nyy Aerodinamicheskiy i Ghidrodinamicheskiy Institoot- central aerodynamics and hydrodynamics institute) in the name of N. Ye.
In 1931 Chyetverikov had given a proposal for a submarine-launched folding flying boat to the head of TsKB (Tsentrahl'noye Konstrooktorskoye byuro - central construction bureau) but nothing was heard for two years until the NII (Naoochno-Issledovatel'skiy Institoot – scientific test institute) placed an order for two prototypes of the SPL.