The transition of the "Geran" to a jet engine proved to be such a significant upgrade that the previous design had to be virtually replaced with a new one. The light fuselage made of foam and plywood could not withstand the loads at jet speeds, so for the "Geran-4", a reinforced airframe using composites and aluminum alloys was developed.
Instead of the previous aerodynamic scheme with limited stability to high overloads, the "Geran-4" received a "tailless" configuration with a delta wing. This layout allows for reduced drag at high speeds and simultaneously withstands the loads that arise during maneuvering.
According to the stated characteristics, the cruising speed of the aircraft is about 300 km/h, and the maximum reaches 500 km/h.
The changes affected not only the airframe. The absence of landing gear simplified the design and reduced weight, as the "Geran-4" is not intended for return after completing its mission. For launch, a ground rail launcher with solid-fuel boosters is used: after reaching initial speed, the booster modules are jettisoned, and the aircraft switches to the thrust of the Lianxin LX WP-160 turbofan engine.
As a result, the "Geran-4" received not just a new engine installed on an existing airframe, but a significantly redesigned structure.
The stated take-off weight of the aircraft is about 450 kg, wingspan is 3.2 m, length is 3.5 m, and the range is estimated at 450–850 km.
It was the reinforced airframe that became one of the key differences of the jet "Geran" from earlier versions of the family. Designers had to abandon the simplest and lightest architecture for the sake of airframe rigidity and the aircraft's ability to withstand the loads that arise when transitioning from a relatively slow piston UAV to a jet aircraft.