Proposed armament was 6 x 23mm Nudelman-Rikhter NR-23 series cannons fitted to the nose section. An additional NR-23 system would be fitted to a tail barbette to protect the aircraft's more vulnerable "six" from interception. Beyond this fixed, standard armament set the aircraft was also being designed with a bomb-carrying capability in mind, this through in-wing bomb bays and underwing rack support. Underwing bombs could be supplanted by either air-to-surface rockets or fuel tanks (the latter improving operational ranges). Much of this armament suite was based on Ilyushin's experience in delivering its classic IL-2: this cannon-and-machine-gun-armed beast was produced in over 36,000 examples from 1941 to 1945 and supported air-to-surface rockets. Its rear was defensed by a machine gun. The IL -2 proved the ultimate "tank-buster" and ground-attack aircraft for the Soviet Air Force of the Second World War.
During January of 1952, Ilyushin finalized the IL-40 and submitted it for possible consideration. Authorities like what it promised and contracted for a single prototype to be built. The completed prototype recorded its first flight on March 7th, 1953 with success. By the end of the month, the cannon armament was fitted and actively tested but it was here that the IL-40 showcased its critical shortcoming - firing of the six guns affected the engines to the point that the systems flamed out due to ingesting the gun's propellant gasses. Thus four AM-23 series cannons were substituted and new gun mounting hardware installed. Firing ports were moved further forward to better deflect the outgoing gasses and keep these form the jet intakes.
This work delayed the program considerably as the aircraft was not transferred for official Soviet Air Force trials until early 1954. Issues with the guns persisted but the aircraft was a good gunnery platform and high-speed performer at its core. To remedy the gun issue even further, a new prototype design was pushed through which relocated the guns to a position under the nose and the engine intake openings were noticeably lengthened forwards, by way of additional ductwork, beyond the original nose of the aircraft. Tumansky had also delivered an improved form of the AM-5F engine, the RD-9V, by this time which promised to increase general performance of the jet aircraft.
Soviet authorities were sold on this revision and funded the second IL-40 prototype which became the "IL-40P". This aircraft saw its own first flight on February 14th, 1955 and ensuing trials revealed the aircraft to be better than its original offering. The Air Force was compelled to order the attack platform in some forty examples. However, before production could really pick up steam (and after five production-quality examples were already completed), the IL-40 project was cancelled by the Air Force in lieu of changing battlefield doctrine and a growing reliance on nuclear weapons to take over the role of dedicated ground attack aircraft.
A total of seven IL-40 related aircraft were produced during the short-lived program. Several other forms, including a torpedo bomber (IL-40T) and artillery spotter (IL-40K), were also planned but came to naught. The IL-40 emerged as a contender in the latter part of the 1960s once more (as the IL-102) but lost out to what became the T-8 from rival Sukhoi. The IL-102 saw its first flight in 1982 and flew 367 total test flights, receiving good reviews from its test pilots. The T-8 evolved to become the Su-25 "Frogfoot", a dedicated Close-Air Support (CAS) platform that still serves the Soviet Air Force today (2015).
The IL-40 was around long enough to earn the NATO nickname of "Brawny".
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