DFS 346 The DFS 346 ( " Samolyot 346 " ) was a German rocket - powered swept - wing vehicle subsequently completed and flown ( with indifferent success ) in the Soviet Union after World War II . It was designed by Felix Kracht at the " Deutsche Forschungsanstalt für Segelflug " ( DFS ) , the " German Institute for Sailplane Flight " . The prototype was still unfinished by the end of the war and was taken to the Soviet Union where it was rebuilt , tested and flown . Design . The DFS - 346 was a midwing design of all - metal construction . The front fuselage of the 346 was a rotation body based on the NACA - Profile 0 , 0121 - 0 , 66 - 50 . The middle part was cylindrical and narrowed to the square in the back . Probably for capacity and weight reasons the DFS - 346 was equipped with landing skids , both in the original German design and in the later Soviet prototypes ; this caused trouble several times . The wings had a 45° swept NACA 0 , 012 - 0 , 55 - 1 , 25 profile of 12 % thickness . The continuously varying profile shape caused a stall in certain flight conditions , which caused complete loss of control . This was later corrected by use of fences on the top of the wings . Development . Concept . The DFS 346 was a parallel project to the DFS 228 high - altitude reconnaissance aircraft , designed under the direction of Felix Kracht and his team at DFS . While the DFS 228 was essentially of conventional sailplane design , the DFS 346 had highly - swept wings and a highly streamlined fuselage that its designers hoped would enable it to break the sound barrier . Like its stablemate , it also featured a self - contained escape module for the pilot , a feature originally designed for the DFS 54 prior to the war . The pilot was to fly the machine from a prone position , a feature decided from experience with the first DFS 228 prototype . This was mainly because of the smaller cross - sectional area and easier sealing of the pressurized cabin , but it was also known to help with g - force handling . The 346 design was intended to be air - launched from the back of a large aircraft , the baseline being the Dornier Do 217 . After launch , the pilot would fire the 346 ' s Walter 509B / C engine to accelerate to a proposed speed of Mach 2 . 6 and altitude of 30 , 500 meters ( 100 , 000 ft ) . This engine had two chambers , high and low thrust , and after reaching altitude the speed could be maintained by short bursts of the smaller chamber . In an operational use the plane would then glide over England for a photo - reconnaissance run , descending as it flew but still at a high speed . After the run was complete the engine would be briefly turned on again , to raise the altitude for a long low - speed glide back to a base in Germany or northern France . Prototype construction . Since the aircraft was to be of all - metal construction , the DFS lacked the facilities to build it and construction of the prototype was assigned to Siebel Werke located in Halle , where the first windtunnel models and partially built prototype were captured by the advancing Red Army . Post - War . On 22 October 1946 , the Soviet OKB - 2 ( Design Bureau 2 ) , under the direction of Hans Rössing and Alexandr Bereznyak , was tasked with continuing its development . The captured DFS 346 , now simply called " Samolyot 346 " ( " Samolyot " - " Aircraft " ) to distance it from its German origins , was completed and tested in TsAGI wind tunnel T - 101 . Tests revealed some aerodynamic deficiencies which would result in unrecoverable stalls at certain angles of attack . This phenomenon involved a loss of longitudinal stability of the airframe . After the wind tunnel tests , two wing fence s were installed on a more advanced , longer version of the DFS - 346 , to correct the airstream separation . This solution was used on the majority of the Soviet planes with sweptback wings of the 1950s and 1960s . In the meantime , the escape capsule system was tested from a B - 25J and proved promising . Despite results from studies showing that the plane would not have been able to pass even Mach 1 , it was ordered to proceed with construction and further testing . Operational use . In 1947 , an entirely new 346 prototype was constructed , incorporating refinements suggested by the tests . This was designated 346 - P ( " P " for " planer " - " glider " ) . No provision was made for a powerplant , but ballast was added to simulate the weight of an engine and fuel . This was carried to altitude by a B - 29 Superfortress captured in Vladivostok and successfully flown by Wolfgang Zeise in a series of tests . This led to the construction of three more prototypes , intended to lead to powered flight of the type . First accidents . Newly built 346 - 1 incorporated minor aerodynamic refinements over the 346 - P , and was first flown by Zeise on September 30 , 1948 , with dummy engines installed . The glider was released at an altitude of 9700 m , and the pilot realised that he hardly could maintain control of the aircraft . Consequently , while attempting to land , he descended too fast ( his speed was later estimated at 310 km / h ) . After first touching the ground he bounced up to a height of 3 – 4 m and flew 700 – 800 m . At the second descent , the landing ski collapsed and the fuselage hit the ground hard . The pilot seat structure and safety - belt proved to be very unreliable , because at the end of a rough braking course Zeise was thrown forward and struck the canopy with his head , losing consciousness . Luckily , he wasn ' t seriously injured , and after treatment in hospital he was able to return to flying . Accident investigation research team came to the conclusion that the crash was a result of pilot error , who failed to fully release the landing skid . This accident showed that the aircraft handling was still very unpredictable , as a result , all rocket - powered flights were postponed until pilots were able to effectively control the aircraft in unpowered descent , requiring further glide flights . The damaged 346 - 1 was later repaired and modified to 346 - 2 version . It was successfully flown by test pilot P . Kazmin in 1950 - 1951 winter , but nonetheless these flights also ended " on fuselage " . Furthermore , after the last flight of these series , the airframe again required major repairs . On 10 May in 1951 , Zeise returned to the program , flying final unpowered test flights with the 346 - 2 , and from 6 June , unpowered tests of the 346 - 3 without accidents . Final flights . By the mid - 1951 346 - 3 was completed , and Zeise flew it under power for the first time on 13 August 1951 , using only one of the plane ' s engines . Continuing concerns about the aircraft ' s stability at high speeds had led to a V limit of Mach 0 . 9 being placed during test flights . Zeise flew it again on 2 September and 14 September . On this last flight , however , things went drastically wrong . Separating from the carrier plane at 9 , 300 meters ( 30 , 500 ft ) above Lukovici airfield , the pilot fired the engine and accelerated to a speed of 900 km / h ( 560 mph ) . The rocket engine worked as expected , and 346 - 3 , quickly accelerating , started ascending and soon had flown in very close proximity of its carrier aircraft . Zeise then reported that the plane was not responding to the controls , and was losing altitude . Ground control commanded him to bail out . He used the escape capsule to leave the stricken aircraft at 6 , 500 meters ( 21 , 000 ft ) and landed safely by parachute . With the loss of this aircraft , the 346 program was abandoned .