In summer 1942
Sergey Ilyushin was requested to design a heavy attack aircraft with a bombload of up to . He chose to scale up the single-engined Il-2 to use the new and more powerful Mikulin AM-42 engine, which was essentially a scaled-up version of the Il-2's
Mikulin AM-38 engine. The design was initially designated the Il-AM-42, but it was soon allocated the factory designation Il-8. While the design of the Il-8 was based on that of the Il-2, it was a completely new aircraft. The oil cooler was housed with the coolant radiator in a big airscoop on top of the engine cowling, closer to the cockpit than was the case on the Il-2. The gunner's position was enclosed in the armored shell, unlike that in the Il-2, and was equipped with a
Berezin UBK
machine gun on a VU-8 flexible mount. Otherwise the gun armament was identical to the older aircraft with a pair of
VYa cannon with a total 300 rounds and a pair of
ShKAS machine guns with 1500 rounds in the wings. Optionally two
Nudelman-Suranov NS-37s could be installed instead of the VYa-23 cannon. The rear
fuselage was lengthened by to improve airflow and the
landing gear was lengthened to accommodate the larger
propeller. The landing gear nacelles were modified accordingly. Two prototypes were built of the Il-8. The first had VYa-23 cannon and a wooden rear fuselage. The second had NS-37 cannon installed and a metal rear fuselage. The first flight was on 10 May 1943 and the prototypes were tested both as attack aircraft and as an artillery spotter variant with less range and better radios. Flight tests were reasonably successful with the Il-8 proving to be almost faster at low altitudes than the Il-2. It climbed 15% faster and had nearly twice the range of the older aircraft. Flight testing was prolonged by problems with the AM-42 engines. They were unreliable, smoky and vibration-prone. But the Il-8 proved to be less maneuverable than the Il-2 in both the horizontal and vertical planes. State acceptance trials lasted from 26 February to 30 March 1944 and it was provisionally accepted for production, provided that these issues were fixed. ==Il-8 specifications==