IL-72 supersonic airliner
The original IL-66 SST project was completely reworked and accordingly allocated a new designation, Ilyushin Il-72. Its design specifications were more realistic – the seating capacity was reduced to 40-60 passengers, the cruising speed target was Mach 2.2. The lower speed made it possible to choose aluminium alloys as the main structural materials. The range was expected to be 4,000-4,500 km (2,486 to 2,797 miles).
On 14th February 1961 these design targets were discussed at the OKB’s Technical council. However, the OKB was unable to proceed with this project, its resources being overtaxed by work on the IL-18’s versions and the IL-38 ASW aircraft and by the construction of the IL-62 prototype. No information is available on the layout and external appearance of the airliner in its revised configuration.
IL-72 medium-haul airliner
In 1964 the Ilyushin OKB initiated design work on projects of airliners intended to supersede the Tu-104, IL-18 and An-10 airliners in due course. One of these projects was the Ilyushin Il-72 airliner. In its basic layout it had much in common with the IL-62 which was under test at that time. The IL-72 featured swept wings, a T-tail and four engines mounted on the rear fuselage.
The design specifications envisaged a 150-seat capacity and a payload of 18 tonnes (39,690 lb), a range of 3,500 km (2,175 miles) and a cruising speed equivalent to Mach 0.82-0.85. The aircraft was intended to operate from 2,000-m (6,560-ft) runways and was provided with appropriate high-lift devices which included triple-slotted Fowler flaps.
Detailed analysis of the adopted layout revealed that the four-engined configuration was not a rational option in this case (as distinct from the bigger IL-62); it entailed excessive maintenance costs reducing the aircraft’s profitability. As a result, the work on this project was discontinued in 1965.