MU-4 and MU-5 by N.G.Mikhelson, V.V.Nikitin

Two-seat wooden amphibious flying boat, intended as a trainer for Navy pilots (so MU designation). Landing gear had oleo-pneumatic shock absorbers and were retracted backwards. Instructor and pilot were seated in enclosed cockpit.

First MU-4 was built in 1936 by N.G.Mikhelson and passed rigorous factory trials. Light aircraft performed well, all required maneuvers (including aerobatic elements) could be performed easily. It crashed due to faulty throttle mount...

The second prototype was redesigned and presented for trials by V.V.Nikitin. This time trials were flawless, and MU-4 was recomended for production. But this never occurred, because the Sha-2 fulfilled all demands and was already in production.

Similar to MU-4, more powerful MU-5 was already under construction. It was cancelled when TTKh package was revised so radically that only all-new design could fulfill it.