In 1949-1950. at OKB-240 design works were carried out to further enhance IL-28. Greater speed and range setting was supposed to achieve in the IL-28S new swept wing with a sweep angle of the line-fourths of the chords of 35 °. We considered two options - powered by the VK-1 and VK-5. The calculations showed that in the first embodiment will not exceed the maximum speed 950 km / h at an altitude of 5000 meters, and range will be 2700 km, a ceiling - 13,000 m, and the run-825 meters.
In the second version of the VK-5 engines, bomb load of 1,000 kg (maximum 2000 kg) and the fuel capacity of 7,000 kg take-off weight of IL-28S increased to 23,930 kg. If this is the maximum speed at an altitude of 5000 meters was estimated at 1,000 km / h, range 2,700 km with 1,000 kg of bombs and the ceiling above the target - 13500m. Takeoff run 750 meters was obtained. However, analysis of the design studies showed that IL-28S with a swept wing has no advantages over the conventional IL-28, while the installation of a swept wing is associated with significant alterations of the IL-28 and the increasing complexity of production. In this regard, the work on IL-28S have been stopped.
Two years later, the idea of a swept-wing tried to revive the project with the IL-28M engines AM-11 (later P11-300) swept wing 35 °, the maximum speed of 1050 km / h, ceiling 15 km, the run-600m.
Nikolay Yakubovich - Ilyushin Aircraft
"The flying Laboratory for the M-701 engine test. The aircraft was also used to test different configurations of brake-parachute containers. The engine under test had a special separate intake."