Ilyushin Il-20 (1948)

Ilyushin Il-20

Company type	Experimental ground-attack aircraft
Industry	Aerospace, Military aviation
Founded	1948
Headquarters	Soviet Union
Products	Military aircraft prototype

For the 1970s aircraft sharing the same designation, see Ilyushin Il-18 § Military.

The Ilyushin Il-20 was a Soviet experimental ground-attack plane designed as a heavily armored successor to the Ilyushin Il-10. It incorporated several novel design elements, such as positioning the cockpit atop the engine directly behind the propeller, and featuring wing-mounted autocannon that could be adjusted on the ground to either fire horizontally or depressed by 23° to enable strafing of ground targets while maintaining level flight. Despite these innovations, it was slower than the Il-10, and its M-47 powerplant experienced significant issues during flight evaluations carried out in 1948–49. Consequently, it did not advance to mass production. Test pilots nicknamed this aircraft the Gorbach (Hunchback).

Development

In response to a 1947 directive seeking an improved replacement for the Il-10 with enhanced performance and firepower, Ilyushin proposed a robustly armored, single-engine, all-metal low-wing monoplane powered by the newly developed M-47 engine—also designated MF-45Sh or M-45Sh—a liquid-cooled unit generating approximately 3,000 horsepower (2,200 kW) at takeoff. A distinctive characteristic of this design was placing the pilot’s cockpit directly above the engine, a layout reminiscent of earlier models like the Blackburn Blackburn and Blackburn Cubaroo. Additionally, situating the cockpit immediately behind the four-bladed propeller optimized pilot visibility. The windshield extended down to the propeller hub, granting a downward viewing angle of 37°, allowing pilots to observe targets beneath during medium dive maneuvers.

Continuing Ilyushin’s tradition in ground-attack aircraft design, the Il-20 utilized a load-bearing armored shell safeguarding not only the pilot and rear gunner but also critical components such as the engine, fuel system, lubrication, and cooling mechanisms. Armor thickness ranged from 6 to 15 mm (0.24 to 0.59 in), collectively weighing around 1,840 kg (4,060 lb). The pilot’s canopy incorporated armored glass measuring 100 mm (3.9 in) in thickness for the main windshield and 65 mm (2.6 in) for smaller quarter windows.

A variety of armament configurations were explored for the Il-20. One concept featured two wing-mounted 23 mm (0.91 in) cannons along with two additional fuselage-mounted guns angled downward at 23° for strafing while flying level. This setup carried a standard bomb load of 400 kg (880 lb), which could be increased to 700 kg (1,500 lb) under overload conditions or substituted with four RS-132 rockets. Another proposed armament included one 45 mm (1.8 in) cannon, two 23 mm guns, and six underwing rockets. Most designs positioned the rear gunner in a dorsal turret separated from the cockpit by the main fuel tank; however, one variant placed him in an armored Il-K8 rear turret, necessitating a lengthened fuselage and repositioned wings aft to maintain proper center of gravity.

The fuselage-mounted cannons angled obliquely were deemed too challenging to aim accurately and thus omitted from the prototype; this omission allowed increasing ammunition capacity for four wing-mounted 23 mm Shpital'nyy Sh-3 guns to 900 rounds. An innovative feature permitted these guns to be adjusted on the ground to fire either horizontally or depressed by 23°. The dorsal gunner operated another Sh-3 gun housed within a remotely controlled Il-VU-11 turret capable of rotating 180° horizontally and elevating up to 80°. A cassette containing ten AG-2 aerial grenades was installed as protection against enemy fighters attacking from below. The aircraft’s maximum bomb load reached 1,190 kg (2,620 lb), with four bomb bays integrated into the wing center-section for small ordnance. Alternatively, two 500 kg (1,100 lb) bombs could be mounted on wing racks. Launch rails enabled deployment of four 132 mm (5.2 in) RS-132 rockets.

The prototype was finalized on 27 November 1948 and undertook its maiden flight on 4 December shortly thereafter. Its top speed was approximately 515 km/h (320 mph) at an altitude of 2,800 m (9,200 ft), which was about 36 km/h (22 mph) slower than that of the Il-10 at similar altitude—likely due to increased aerodynamic drag and weight penalties from its enlarged fuselage cross-section caused by placing the cockpit above the engine. The M-47 engine proved problematic, exhibiting severe vibration issues during testing. Additional concerns included dissatisfaction from Air Force officials regarding armament effectiveness and restricted engine accessibility for routine maintenance due to cockpit placement over it. There were also safety apprehensions about how closely positioned cockpit and propeller blades might endanger pilots during bailout or emergency belly landings if propeller blades struck the canopy.

These combined factors, along with advances in jet propulsion technology, led to termination of the Il-20 project on 14 May 1949.

Specifications (Il-20)

Bibliography

• Gordon, Yefim; Komissarov, Dmitriy and Sergey. OKB Ilyushin: A History of the Design Bureau and its Aircraft. Ian Allan, London, 2004. ISBN 1-85780-187-3.
• Gunston, Bill. The Osprey Encyclopedia of Russian Aircraft from 1875 - 1995. Osprey Aerospace, London, 1995. ISBN 1-85532-405-9.
• Nemecek, Vaclav. The History of Soviet Aircraft from 1918. Willow Books, London, 1986. ISBN 0-00-218033-2.

External links

• http://www.ctrl-c.liu.se/misc/RAM/il-20ily.html Archived 2013-10-29 at the Wayback Machine
• http://www.fantastic-plastic.com/IlyushinIl-20Page.htm