The OKB-1 EF 131 was a single-prototype jet tactical bomber developed in the Soviet Union during the late 1940s. The aircraft was a direct evolution of the German Junkers Ju 287 design, constructed by a team of former Junkers personnel organized into the Soviet experimental design bureau known as OKB-1. Production took place between 1946 and 1947, utilizing components from previous Ju 287 prototypes; specifically, some accounts indicate the wings were sourced from the Ju 287 V2 and the fuselage from the V3.
Technically, the EF 131 is most notable for its radical forward-swept wing layout. This configuration was intended to improve low-speed handling and delay the onset of wing stall, although it introduced significant aeroelastic and structural flexibility challenges. To provide sufficient thrust, the aircraft employed six small turbojet engines—likely Junkers Jumo 004 axial-flow engines—mounted in pairs within nacelles located on and under the wings. While the baseline model used these German-designed engines, subsequent research involving the airframe included tests with Soviet AM-series turbojets and potentially Rolls-Royce Nene engines in later derivative projects like the EF 140.
Flight testing occurred between 1947 and 1948, though precise dates are contested. Some records suggest a first flight around May 23, 1947, while other Eastern European sources cite September 30, 1948, noting that early trials were hindered by fuel-control issues with Soviet engines. Despite these efforts, the EF 131 never entered series production and remained a purely experimental vehicle. It never saw combat or operational service, as it was operated solely by the OKB-1 research team for evaluation purposes.
The legacy of the EF 131 lies in its role as a technological link. It demonstrated how the Soviet Union leveraged interned German expertise to accelerate its own aerospace programs. The data gathered from the EF 131 directly influenced later Soviet research into swept-wing aircraft. No examples of the EF 131 survive today, as the sole prototype was scrapped following the conclusion of its flight program.