The SK V4, was a single-seat fighter trainer powered by a 240 hp Argus As 10C-3 eight-cylinder inverted-Vee air-cooled engine. Featuring exceptionally clean lines, the SK V4 was a low-wing cantilever monoplane with a tailwheel undercarriage, the wide-track main members of which retracted inwards. Provision was made for the mounting of a single 7,9-mm MG 17 machine gun, an electrically-actuated variable-incidence tailplane was provided, and the structure comprised a one-piece wooden wing built around a single box spar, and a welded steel-tube fuselage with plywood skinning.
.In early 1944  the RLM gave Kauba a go ahead  with a  development of Sk 257 to a single-seat training aircraft for fighter training based on the the SK.V4 .
THe Sk 257 was an aerodynamically clean , low-wing with retractable  landing gear in mixed construction ,  the tail wheel was not retractable. The fuselage consisted of a steel tube construction which was covered with shells made of plywood . The wing was a two-piece all-wood construction with a box beam and split flaps between ailerons and fuselage.
The tail was also an all-wood construction , and the tailplane was electrically adjustable. Only the rudder were fabric covered .
The main wheels  was  drawn electrically inward into the wings . The engine  used later in the series production was an  air-cooled 12 cylinder V-engine   Argus 410 , 485 hp.  Production location  in Trencin, Slovakia was decided . The prototype testing was  done on the air base Biskupice in Poland. While the first prototype with the Argus As 10c  equipped with only 240 hp starting power ,  showed very good performance. The first machines of the zero series also had the Argus As 10c, were poorly finished and so showed large manufacturing defect that it was decided to cancel production for the time being , to remedy the deficiencies . This happened in the autumn of 1944. Until then, five pre-series aircraft were built . At a later restart of production, did not occur . The built prototypes and preproduction machines were eventually scrapped.

• 
• 
• 

•