The NKAP (
Narodnyy komissariat aviatsionnoy promyshlennosti—People's Ministry of the Aircraft Industry) requested on 7 October 1940 that the OKO (
opytno-konstrooktorskiy otdel—Experimental Design Department) of Factory (
Zavod) No. 1, which would later become the
Mikoyan-Gurevich design bureau (
OKB) begin work on a twin-engined long-range, single-seat escort fighter intended to use the AM-37 engine, then under development by Mikulin. It also requested that specifications, along with a model, be ready to be discussed on 12 November of that year. Three days later Mikoyan and Gurevich were ordered to produce three prototypes to undergo State acceptance trials on 1 August, 1 September and 1 November 1941. After the meeting, the NKAP broadened its roles to include bombing, torpedo attack, reconnaissance and interdiction. The DIS was intended to be armed with a
VYa cannon with 200 rounds in a pod beneath the nose, but the
VVS preferred the Taubin MP-6 cannon. The DIS was to carry two of them with 120 rounds per gun, but they proved to be a failure and the aircraft reverted to the original VYa cannon. Each wing root was to have a synchronized
Berezin UBS machine gun with 300 rounds mounted below a pair of
ShKAS machine guns with 1000 rounds per gun. The gun pod could be removed and bombs up to or a torpedo could be carried instead. The OKO, along with all other aircraft designers, had been directed to use the
Shvetsov ASh-82 radial engine as a backup engine for their products in May 1941, but the evacuation disrupted the production of this version, known internally as the
IT and it was not built until the autumn of 1942. Aside from the engines, it differed from the
T in small respects. Its tailcone was split vertically to use as an
air brake and the armament was revised to consist of two VYa cannon in the undernose pod with 150 rounds each and four Berezin UBK machine guns mounted in the wing roots. It made its first flight on 28 January 1943 and demonstrated a top speed of and a time to 5,000 meters of 6.3 minutes. Flight testing was stopped on 10 February when the floatless carburetors had to be sent to TsIAM (''Tsentrahl'nyy Institoot Aviatsionnovo Motorostroyeniya''—Central Institute of Aviation Motors) for adjustment. There were continuous problems with these and they delayed the entire project until it was cancelled in October 1943. ==Variants==