Ilyushin Il - 20 ( 1948 ) The Ilyushin Il - 20 was a Soviet prototype for a heavily armored ground attack aircraft to replace the Ilyushin Il - 10 . It featured a number of innovative concepts including a cockpit mounted on top of the engine , directly behind the propeller , and wing - mounted autocannon that could be adjusted on the ground to fire level or depressed 23° to allow the aircraft to strafe ground targets while remaining in level flight . However it proved to be slower than the Il - 10 and its immature M - 47 engine proved to be problematic during flight tests in 1948 – 49 and it was not placed into production . The test pilots called the aircraft the " Gorbach " ( Hunchback ) . Development . Sergey Ilyushin ' s concept to meet the 1947 requirement for an aircraft that was to be superior to the Il - 10 in performance and firepower was a heavily armored , single - engine , all - metal , low - wing monoplane powered by the newly developed M - 47 — also known as the MF - 45Sh or M - 45Sh — liquid - cooled engine that developed at take - off . But the design ' s most notable feature was the pilot ' s cockpit which was mounted directly above the engine reminiscent of the Blackburn Blackburn and Blackburn Cubaroo . Furthermore the cockpit was situated directly behind the four - bladed propeller to maximize the pilot ' s visibility . The windshield extended down to the propeller hub and provided the pilot with a 37° downward field of view ; in a medium dive he could view targets directly underneath the aircraft . As was traditional with Ilyushin ' s ground attack aircraft the Il - 20 used a load - bearing armored shell to protect the pilot and gunner as well as the engine , fuel , lubrication and cooling systems . The thickness of the armor varied between and weighed a total of . The pilot ' s canopy used armored glass thick for the main windshield and for the quarterlights . A wide variety of armament suites were considered for the Il - 20 . One involved two wing - mounted cannon and two others mounted in the fuselage , fixed downwards at a 23° angle for strafing targets in level flight . This version ' s normal bomb load was only , but could be carried in overload condition or four RS - 132 rockets could be carried instead . Another version used one cannon , two 23 mm guns and six under - wing rockets . Most studies placed the rear gunner in a dorsal turret separated from the cockpit by the main fuel tank , but one study put him in an armored Il - K8 rear turret , but this required a longer fuselage and moving the wings aft to maintain the CG in the right place . The obliquely mounted fuselage cannon were thought to be too difficult to aim and were not included in the prototype ; the weight savings allowed the ammunition for the four 23 mm Shpital ' nyy Sh - 3 wing - mounted guns to be increased to 900 rounds . One additional innovation in the prototype was that they could be adjusted on the ground to fire at a 23° downward angle in addition to the normal level position . The dorsal gunner also fired a Sh - 3 gun , which was mounted in a separate , remotely controlled , Il - VU - 11 turret which could be traversed through 180° and elevated to a maximum of 80° . A cassette of ten AG - 2 aerial grenades was provided to deter any fighters approaching from below . Maximum bomb load was and four bomb bay s were provided in the wing center - section for small bombs . Alternatively two bombs could be carried on wing racks . Launch rails were provided for four RS - 132 rockets . The prototype was completed on 27 November 1948 and its first flight was shortly afterwards on 4 December . The best speed that the Il - 20 could manage was only at an altitude of , slower than the Il - 10 at the same altitude , possibly a consequence of the increased drag and weight penalties inherent in the greater fuselage cross - section and area as a result of the placement of the pilot above the engine . The new M - 47 engine proved to be defective with severe vibration problems . Other problems were that the Air Force wasn ' t satisfied with the armament and that access to the engine for routine maintenance was severely hampered by the placement of the cockpit over the engine . Another concern was the close placement of the cockpit to the propeller ; this was believed to increase the risk to the pilot if he had to bail out or had to make a belly landing in which case the bent propeller blades might hit the canopy . These issues , coupled with emerging jet engine technology , led to the cancellation of the Il - 20 program on 14 May 1949 .