The development of the Executive Airplane or IS (Russian: Исполкомовскый Самолет “- ИС), designated BOK-3 by BOK (Russian: БОК-3, ИС or ЦКБ-9), began in 1933 at the TsKB of Factory No.39 Menzhinski, which is why it was also known as TsKB-9. The works were transferred to the BOK’s new location at Factory No.35 located in Smolensk.
The conceptual drawings of the original version of the model are preserved, signed by II Tsiebrikov, at that time a recent graduate who was already directing the general types section of the BOK.
The prototype completed in Smolensk in 1936 basically differed from the original concept design in the shape of the cockpit cover. The original angled front led to a more streamlined and modern shape. Other differences were the bracing of the tail planes in the produced model with their transfer to a higher position on the empennage and the absence of a fairing on the landing gear. The rudder and tail skid were also modified.
The BOK-3 was designed as an all-wood cantilever low-wing monoplane. As a remarkable detail, the wingtips were folded to reduce the area during transport or parking in hangars.
The fuselage had a monocoque structure. Both the wing and the tail were made of wood with a textile coating. The ailerons and the empennage featured a fabric-covered duralumin frame. The tailplane sat high on the empennage and was braced by inverted V posts.
The landing gear was of the conventional type with fixed and tail skid.
The BOK-3 was designed to use an M-48 radial engine protected by a Townend ring. This engine was also installed in the U-3 experimental aircraft and only a few units were built.
The BOK-3 was designed for short-distance shuttle service, but other possibilities of use such as pilot training and agricultural tasks were possible. The training version provided for the installation of double flight control and a PV-1 machine gun firing through the propeller shaft, another machine gun in a rear defensive position, a camera for aerial photography and the ability to install supports for a general capacity of 100 kg.
In agricultural versions the BOK-3 could have a chemical spraying system installed.
Only one prototype was built and successfully flown in 1936 but the development of the BOK-3 was abandoned.
Powerplant: 1 x М-48 piston engine
Wingspan: 11.00 m
Length: 7.10 m
Fuel capacity: 190 liters
Endurance: 3 hours
Accommodation: 2
All Aero 