Bolkhovitinov S The Bolkhovitinov S ( " Sparka " – twin / joined ( engine ) ) was a high speed bomber aircraft designed and built in the USSR from early in . Other designations used at various times : BBS , BB , LB - S or SSS . Development . The plane was conceived as a fast light bomber and reconnaissance plane . To obtain high speed and good aerodynamics , it was powered by two M - 103 inline engines in tandem in a fuselage nose , driving two contra - rotating coaxial three - blade propellers . The design had quite unusual look , with long fuselage nose and a crew cab moved rearwards , towards double tailfin . Wings had a fighter - like form and their span was rather short . The VVIA under Bolkhovitinov was enlarged to tackle the expected problems in the design of the Bolkhovitnov S . The rear engine was geared to two high - speed shafts which passed either side of the forward engine to drive the rear propeller gearbox , whilst the forward engine and gearbox drove the forward propeller via shaft through the middle of the rear propeller gearbox . The structure of the S was predominantly light alloy stressed skin , the wing having two spars with heavy flush - rivetted upper and lower skins , and the fuselage built up from pre - formed upper , lower and side panels attached to four longerons to give a strong but relatively simple structure to build . A total of 29 electrical actuators drove the Fowler Flaps , undercarriage , ( rotating 90deg to lie flat in the wing ) , exit flap of the large common radiator duct and many other services . The tail unit consisted of twin fins with rudders attached to the tips of the tailplane , variable geared elevators and separate servo and trim tabs on elevators , and rudders . Detail design of the aircraft began in 1937 and construction in July . The first prototype S - 1 was built in 1939 , but it was made in order to evaluate an airframe only and therefore was powered by only one engine M - 103 . It was unarmed and fitted with a fixed skid landing gear . It first flew on January 29 , 1940 , with B . N . Kudrin at the controls . A maximum speed was 400 km / h . The second prototype S - 2 was powered by two engines and was armed with a single machinegun and bombs . Four 100 kg bombs were carried vertically in a bay between pilot and a rear gunner - navigator , under a common canopy . Its state testing started from March 20 , 1940 and lasted until July 1940 . A maximum speed reached was 570 km / h . The plane had good handling , except for take - off and landing , which were difficult due to high wing loading . Its range and speed were also lower , than estimated . As a result , it was decided to improve the plane further . However , the plane was not developed in a favour of next Bolkhovitinov designs . It was first planned to build also an attack plane with 2 Ultra - ShKAS machineguns with a high rate of fire , in a rear part of fuselge , firing downwards and manned by a second crew member . Also an interceptor aircraft was proposed , armed with 37 mm recoilless rifle , firing upwards , at an angle and manned by two crewmen . The plane had no official designation given . It was mostly known as S - " sparka " ( otherwise explained as " spartak " , " skorost " ( speed ) or " Stalin " ) , also known as BBS - " blizhniy bombardovshchik skorostnoi " ( close - range fast bomber ) , BB - " bombardovshchik Bolkhovitinova " , LB - S - " legkiy bombardovshchik sparka " ( light bomber paired ) , SSS - " svyerkhskorostnoi samolet " ( very fast aircraft ) .