The Grigorovich MK-1 (MK - Morskoi Kreiser - sea cruiser) was a large trimotor floatplane, built and tested in Imperial Russia in 1916.
The wings, mounted with flexible bungee joints allowing up to 180 mm (7.1 in) of movement, also carried wing-tip floats for stability on the water.
Two 220 hp (160 kW) Renault 12E V-12 water-cooled engines were mounted in strut-supported nacelles between the upper and lower mainplanes.
A third engine was added to the centre section of the upper mainplane, to address perceived centre-of-gravity problems and increase the power available; initially this was to have been a 150 hp (110 kW) Sunbeam Crusader, later replaced by a 140 hp (100 kW) Hispano-Suiza 8A before flight trials commenced.
[1] Data from The Osprey Encyclopedia of Russian Aircraft 1875–1995,[2] Istorija konstrukcij samoletov v SSSR do 1938 g.[1]General characteristics Armament