MiG-15 bis / SYe / U. [Hying Laboratory!

From 1947 to 1952 intensive research on wing profiles and aerodynam­ic design for supersonic speeds was carried out at TsAGI, LII, and other science centers. The top speed of the production MiG-15 was limited to Mach 0.92—above that, the aircraft’s transverse stability deteriorated. Two LII engineers, I. M. Pashkovskiy and D. I. Mazurskiy, proposed to relieve the ailerons and to increase the rudder area. To test their ideas, two SYe prototypes were built using MiG-15 bis SD airframes at factory no. 1 in Kuybyshev.

The rudder of the SYe was taller and thus larger than that of the SD; the fin had to be modified accordingly. V. P. Yatsenko engineered these changes and took charge of the prototypes. (Yatsenko had acquired some fame as the designer of the 1-28 fighter in 1938. He joined the MiG ОКБ in July 1941.) The fin was enlarged along all of its chords and made taller in order to position the upper hinge fitting of the rudder. The original drawings did not impel the builders to con­struct an entirely new tail fin but only to match it with the new rudder dimensions—hence the break of the fin’s leading edge (see the side drawing of the SYe).

To reduce the wing divergence at high speed that resulted in a wing dropping, strengthening panels were installed on the upper sur­face near the wing roots, above the wheel wells. Moreover, the span of the ailerons was increased. Thus the wing area increased—since the wing tips, instead of being rounded, were now angular at the trailing edge—but the wing span remained unchanged. At first there were no aileron servo-controls, but the enlarged rudder and the much improved wing stiffness allowed the aircraft to fly at higher speeds while still han­dling well.

The MiG-15 bis SYe was flight-tested at the LII by D. M. Tyuteryev. On 21 September 1949 he reached Mach 0.985 at 12,000 m (39,360 feet) by climbing to the aircraft’s service ceiling and then going into a shallow dive at maximum engine thrust. The first BU-1 hydraulic servo-controls appeared at the end of 1948, and the SYe pro­totype was fitted with one. On 18 October 1949 Tyuteryev broke the sound barrier in the SYe.

The test flights of the SYe contributed a great deal to the research work on supersonic speed then under way in the USSR. They also had a hand in the achievement of I. T. Ivashchenko, who in February 1950 reached Mach 1.03 on a production MiG-17.