In early 1941, the Soviet Union issued a requirement for a new high-altitude fighter aircraft to counter enemy high-altitude
reconnaissance aircraft such as the
Junkers Ju 86. However, it was not until late 1942 that a contract for two prototypes was placed with the
Mikoyan and Gurevich OKB, which began work on
Samolyot A (Aircraft A).
Samolyot A, designated I-220 by the
People's Commissariat of Aviation Industry (NKAP), was of an entirely new design of primarily
shpon (
wood veneer) construction with a steel-tube truss engine mount and a light-alloy tail. The wing's airfoil was of a CAHI
laminar-flow type, and the wing was fitted with
leading-edge slat and split
flaps. All air inlets were located in the leading edge of the wing near the wing roots. The tail was of a similar design to that of the
I-230 but with a slightly increased
tailplane span. Power was provided by a
Mikulin AM-39 engine, though the first prototype was originally powered by a
Mikulin AM-38F driving a three-bladed AV-5A propeller. The aircraft featured
conventional landing gear with inward-retracting main gear and a retractable tailwheel. Fuel was provided by six
self-sealing tanks made of rubberized fabric with two in the fuselage and four in the wings. The cockpit seated a single pilot under a sliding canopy and was designed to eventually be pressurized, though a pressurization system was never fitted. Armament was to be four
ShVAK autocannons, each with 150 rounds, with two located above the engine and two beside the crankcase. Only the two cannons above the engine were fitted on the first prototype, though the lower gun ports were not faired over. With overflights of Ju 86R reconnaissance aircraft still being a problem in the summer of 1942, work began on an I-220 variant with improved performance in the stratosphere. Designated I-221, or
Samolyot 2A, the aircraft had a redesigned wing with an increased span and a
NACA-234 airfoil. The outer wings and rear fuselage were of all-metal construction. Power was provided by a Mikulin AM-39A turbo-supercharged engine driving a three-bladed propeller. The number of turbo-superchargers fitted to their aircraft is unclear, with some published descriptions of the I-221 stating that there were two TK-2B turbo-superchargers while the MiG OKB design drawing showed only a single TK-2B unit mounted on the right side of the cowling. The I-221 was the first MiG aircraft to feature a pressurized cockpit, which was air conditioned with cooling provided by a heat exchanger housed in an air duct underneath the fuselage. Fuel capacity was increased from that of the I-220, but by how much is unknown. The upper pair of ShVAK cannons were deleted on the I-221, leaving only the two cannons mounted beside the engine with 150 rounds each. The I-222, or
Samolyot 3A, was similar to the I-221, but was powered by a Mikulin AM-39B-1 engine with a single TK-300B turbo-supercharger on the left side of the cowling. The engine originally drove a three-bladed AV-5A propeller, but this was later replaced by a four-bladed AV-9L-26 unit. An
intercooler for the turbo-supercharger was housed in a deep air duct underneath the fuselage near the leading edge of the wing. The outer wings and rear fuselage reverted to wooden construction, with the rear fuselage also being slightly lowered to improve rear visibility. Like the I-221, the I-222's cockpit was pressurized and air conditioned. Unlike the I-221, however, it was fitted with a bulletproof windscreen and bulletproof glass behind the pilot's head, all thick, and 8 or 9 mm armor plates were added to the pressure bulkhead. The sliding canopy was reinforced with a heavy metal frame which reduced visibility, and fuel capacity was reduced by removing the fuselage tanks. Armament was the same as on the I-221, but with ammunition reduced to 80 rounds per gun. The I-224, or
Samolyot 4A, was similar to the I-222, but with several changes including moving the TK-300B turbo-supercharger to the right side and the pressurized cockpit changed to welded aluminum alloy construction instead of wood. The aircraft was powered by a Mikulin AM-39B engine driving a four-bladed AV-9L-22B propeller, and the intercooler air duct was made deeper. Fuel capacity was increased, as was ammunition with 100 rounds per cannon. The final development of
Samolyot A was the I-225, or
Samolyot 5A, which was based on the original I-220, though unlike the previous variants it was not intended for high-altitude fighting. Powered by a
Mikulin AM-42B engine driving a three-bladed AV-5A-22V propeller, and the underside of the cowling was deeper. The wings and pressurized cockpit were of all-metal construction, and the cockpit had improved instruments and controls. The cockpit was also armored with a thick bulletproof windscreen, a rear glass slab of the same thickness, and a seat with armor plating. Originally, only a single I-225 was ordered, though a second prototype was later ordered with a AM-42FB engine. == Operational history ==