The SPL (Samolyet dlya Podvodnikh Lodok – aeroplane for submarine boats) (a.k.a.

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.

The OSGA-101 was of mixed construction with wooden wings and hull but Welded steel tube booms carrying the fabric covered Duralumin tail unit.

The SPL was very similar but included shorter span wings which folded to lie alongside the fuselage, only two seats in the cockpit, and a pivoting engine nacelle which folded rearwards to lie between the tail-booms.

Krzhizhevskii, and were completed by August 1935, but the SPL was rejected due to poor seaworthiness.