The Shpitalny Sh-37 (Russian: Шпитальный - Ш-37) was the first indigenous Soviet 37 mm (1.5 in) aircraft cannon, designed by Boris Shpitalniy at OKB-15. The gun saw limited production and was installed in few aircraft before being replaced by the competing Nudelman-Suranov NS-37 designed at OKB-16. It was installed on a military-trial basis on two short series of aircraft. Installed to fire through the hollow, gear-driven propeller shaft and fastened to the engine block of the Yak-7-37 it was known as MPSh-37, where "MP" stands for "motornaya pushka", similar to the German Motorkanone term for the same mount type. As installed in the underwing gun pods of the Il-2 it was known as ShFK-37 (Russian: ШФК-37 - Шпитальный фюзеляжно-крыльевая калибра 37 мм), literally "Shpitalny fuselage-wing(-m