The 1950 and 1960s were a tremendous period of growth and advancement for commercial / passenger flight. The end of World War 2 in 1945 allowed all-new technologies to be employed in non-military circles and this included turbojet and turboprop engines. Ilyushin, the storied big-plane manufacturer of the Soviet Union, delivered one of its best-known products in this window - the Ilyushin Il-18.
In the mid-1950s, Soviet passenger carrier Aeroflot, founded in 1923, released a new requirement calling for a budget-friendly 75- to 100-seat airliner for its various routes. This work begat the Ilyushin Il-18 which earned itself the NATO codename of "Coot". The aircraft went on to see a considerable service career in both civilian and military industries and did much to further Soviet air travel during the 1960s and 1970s. The airframe also served well beyond its given passenger-hauling role, adopted for maritime patrol, airborne command post and ELINT (ELectronic INTelligence) activities. Production of the ultimately 678 total aircraft spanned from 1957 to 1985 from Moscow Machinery Plant No. 30.
To go along with the new aircraft directive was also development of all-new turboprop engines. This fell to Kuznetsov and Ivchenko while Ilyushin and Antonov would each focus on the airframe. The Ilyushin submission became the four-engined "Il-18"and Antonov pushed its four-engined "An-10". The engine of choice was to eventually become the Kuznetsov NK-4 series.
A prototype of the Ilyushin design was revealed in June of 1957 and testing ensued throughout thate summer with a first-flight recorded on July 4th, 1957. The Il-18 was selected to succeed the aging line of Il-14 aircraft on the Ilyushin production lines and the initial market form became known as the "Il-18A", this offering seating 89. The engines, the NK-4 series, proved so unreliable that a move was made to the competing Ivchenko AI-20 after only twenty aircraft were completed with the original engine fit. The shift in powerplant then produced the "Il-18B" designation and a prototype of this form first flew on September 30th, 1958 and became the first major mark of the series. Then followed the Il-18 "Combi" which combined passenger and cargo functionality into one suitable airframe.
The Il-18D carried more powerful AI-20M engines (4,250 horsepower) and increased seating for up to 122 as well as an extra internal fuel tank for increased ranges. A communications model was born from this mark as well and three were produced to the standard for the Russian government. The Il-18D "Pomor" was a one-off Il-18D model for use in the fisheries industry. The Il-18D "Salon" was the VIP transport version of the Il-18D line.
The Il-18D featured a crew of nine with up to 120 passengers. It sported a length of 35.9 meters with a wingspan of 37.4 meters and height of 10 meters. Empty weight was listed at 35,000 kilograms with a MTOW of 64,000 kg. Maximum speed was 675 kmh and cruising was int eh 625 kmh range. Operational range was 6,500 kilometers and the service ceiling became 11,800 meters.
A pair of Il-18D aircraft served as the basis for the Il-18DORR fisheries industry model. The Il-18E was based on the Il-18I but lacked the increased fuel capacity and, therefore, decreased its operational range. The Il-18E "Salon" was its VIP model. The Il-18Gr was completed as a converted cargo form.
The Il-18I, like the Il-18D, featured the AI-20M turboprop engines of 4,250 horsepower. The Il-18LL became a flying laboratory used to test deicing equipment. The Il-18RT were a pair of Il-18V models outfitted with Telemetry Relay equipment for various trials. The Il-18S was used as a VIP platform and based on the Il-18B product. Il-18A, B- and V-models made up various transport forms under the collective Il-18T designation. The Il-18TD was a military-minded transport proposal which was not adopted by Soviet forces. A one-off Il-18 existed as the Il-18USh based on the Il-18V and used in navigator training but not adopted in useful numbers by the Soviet Air Force.
Il-18V became the major variant fielded by carrier Aeroflot. it was powered by AI-20K series turboprops and could seat up to 100 passengers. Service entry came in 1961. The Il-18V "Salon" was its VIP form.
Il-20M "Coot-A" was the NATO-recognized platform used by the Soviet Air Force for ELINT and reconnaissance sorties. It was also recognized as the Il-18D-36 "Bizon". The Il-20RT was a communications relay platform and the Il-22 "Coot-B" an airborne command post. New mission equipment greeted the Il-22M design. An Anti-Submarine Warfare (ASW) model was the Il-38 "May" based on the Il-18 series. The Il-118 existed only as a proposed, upgraded Il-18 offering to be outfitted with 2 x Lotarev D-236-T propfan engines. as its propulsion scheme.
There proved little groundbreaking design features in the Il-18 which more than likely made it a sound aircraft from the get-go. Its monoplane wing assemblies were straight with clipped tips and each held a pair of engines along their leading edges. The mainplanes, and the tailplanes, were all low-mounted along the tubular fuselage sides. A single vertical tailfin adorned the extreme aft section of the aircraft. The cockpit was held at front, over the nose, in the usual way and a wholly-retractable tricycle undercarriage featured for ground running. Circular windows dotted the sides of the fuselage as did entry/exit and emergency doors.
Operators of the Il-18 line were largely those countries aligned with Moscow during the Cold War (1947-1991). This included Afghanistan, China, Cuba, Czechoslovakia, East Germany, Egypt , Poland, Ukraine and others - its reach was very global and its time in service proving the product to be very reliable and robust, hence its impressive production totals and myriad of operators.
Today (2016), North Korea remains the lone notable operator of the type through its Koryo Airlines brand. NPP MIR (ChK Leninets) of Russia operates just one example.