Purpose: To test designer’s experimental wing.

Design Bureau: Aircraft constructed by BOK to design of S S Krichevskii.

Sawa Syemenovich Krichevskii, called ‘a tal­ented designer’ by historian Shavrov, spent the early 1930s trying to create the most effi­cient aeroplane wing. He made many tunnel models, eventually settling on a wing of high aspect ratio constructed in front and rear sec­tions. The rear part was hinged to the front
with a small intervening gap acting as a slot. In flight, the intention was that the pilot would select the optimum angle for the rear portion, Shavrov commenting that ‘this wing could al­ways be flown in a drag-polar envelope’.

Krichevskii secured funding to build a re­search aircraft, called RK (Razreznoye Krylo, slotted wing) and designated BOK-2 by the construction bureau. The BOK-2 was complet­ed in 1935 and flew successfully, but Krichevskii died shortly afterwards. Documen­tation on this aircraft has never been found.

The BOK-2 was an extremely neat can­tilever monoplane, with a single M-l 1 engine rated at 11 Ohp. Shavrov comments that ‘The wing skin was polished to mirror brilliance [suggesting all-metal construction]…it is hard to say if its excellent performance was due to its drag-polar envelope or to its perfect aerodynamic shape’.

Despite its apparently excellent perfor­mance the RK appears to have had no impact on the Soviet aviation ministry.

No data available.