Ilyushin Il-18 (1946)

Ilyushin Il-18

Company type	Aircraft prototype
Industry	Aviation
Founded	1946
Founder	Ilyushin design bureau
Defunct	1948
Fate	Project discontinued
Headquarters	Soviet Union
Products	Four-engine airliner prototype

For the 1957 airliner, see Ilyushin Il-18.

Overview

The Ilyushin Il-18 (NATO reporting name: Clam) was a four-engine airliner developed in the Soviet Union by the Ilyushin design bureau shortly after the conclusion of World War II. Although the aircraft demonstrated solid performance, its Shvetsov ASh-73TK radial piston engines proved unreliable for commercial aviation and were prioritized for use in the Tupolev Tu-4 bomber. Consequently, the project was discontinued in 1948.

Development

The Il-18 originated from Aeroflot’s requirement for a high-altitude, long-distance airliner capable of servicing extensive domestic and international routes. Designed as a cantilever low-wing monoplane, it was initially intended to be powered by four Charomskii ACh-32 diesel engines—the same powerplants employed in the Ilyushin Il-12—and featured tricycle landing gear. To enhance aerodynamic efficiency and boost maximum speed, the wing incorporated an exceptionally high aspect ratio of 12. The aircraft was engineered to operate from runways shorter than 1000 meters, including unpaved strips, with oversized main wheels to accommodate rough terrain. The fuselage was pressurized with a circular cross-section, providing space beneath the cabin floor for cargo and baggage compartments. Various interior configurations were considered, ranging from seating for 66 passengers to arrangements offering 27 sleeping berths; however, no final layout was settled upon before cancellation.

Prior to its maiden flight, the originally planned diesel engines were replaced with 2400 hp Shvetsov ASh-73TK radial piston engines due to their entry into production and greater availability. These engines drove four-bladed AV-16NM-95 variable-pitch propellers. The aircraft incorporated electro-thermal deicing boots on the leading edges of the wings and tail surfaces, powered by four engine-driven electric generators. Additionally, a bleed-air deicing system was installed for cockpit windows and propeller blades.

The Il-18 conducted its first flight on 18 August 1946 configured for sixty passengers, despite not yet being equipped with turbo-superchargers on its engines. To expedite testing, Sergey Ilyushin authorized flight trials without these components; however, this proved ineffective as turbo-superchargers were delayed, postponing completion of manufacturer flight tests until 30 July 1947. Significant issues included limited engine overhaul intervals—initially only 25 hours—and an engine failure during flight on 25 June 1947. Flight handling was stable, and the passenger cabin offered significantly greater comfort compared to contemporaries such as the Lisunov Li-2, C-47 Skytrain, or Il-12. The power margin allowed continued cruising even with one or two engines out. Nevertheless, due to engine scarcity—since they were allocated primarily for the Tupolev Tu-4—and insufficient reliability for cost-effective operation, the Il-18 program was terminated.

The prototype was showcased at the 1947 Tushino air show leading a formation of Il-12 aircraft. Subsequently, it was equipped with a towing hook and used in flight tests for the heavy Ilyushin Il-32 glider, being one of the few aircraft with adequate power for such tasks. The prototype remained operational into the early 1950s; however, its final disposition remains undocumented.

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