Planes

USSR

I-16 Type 24

The I-16 was a Soviet single-engine monoplane fighter designed in the 1930s by the Polikarpov Design Bureau. As early as 1939 few remained unconvinced that the era of the I-16 was ending. Even the installation of the more powerful M-62 and M-63 engines did not allow serial examples to exceed 500 km/h. For some time it was believed that better performance could be achieved with the use of the M-64 engine, rated at 1,200 to 1,300 HP. Designers expected the M-64 (there was also an M-65) to be ready by 1941; however this nine-cylinder radial engine was never adequately completed. Nikolai Polikarpov, the lead designer, attempted to improve the I-16’s aerodynamics by replacing its canvas outer skin with plywood. In the summer of 1939 a prototype with upper wing surfaces covered with 2.5mm thick plywood was tested; at the same time, an I-16 Type 24 with plywood surfaces was submitted for state trials. The latter achieved 489 km/h, which was slightly better than other variants. However the achievement was chalked up to the new M-63 engine.

While the plywood surface was recommended for production, it was in fact never used on serial production aircraft. Further flight testing of the I-16 in 1939 proved that subsequent modifications were not cost-effective. One of the proposed modifications was to address the tuck-under phenomenon in high speed dives which took place when deflecting the elevator to a positive angle of attack. Several fatal crashes led to further research into the issue. As it turned out, the I-16 was highly sensitive to angle of attack changes of the elevator.