'Aircraft K'; USAF/DoD designation: Type 8)[1] was an early jet fighter built in the Soviet Union shortly after World War II.

[2] The Su-9 had an oval cross-section, all-metal stressed skin monocoque fuselage that housed a single cockpit.

The aircraft carried a total of 1,350 kilograms (2,980 lb) of fuel in two bladder tanks, one each ahead and behind the pilot.

This consequently increased the take-off and landing speeds so it was equipped with a provision for two JATO bottles (11.27 kN (530 lbf) thrust for 8 seconds) mounted on the sides of the fuselage.

This goal was not met because the OKB was heavily committed to other projects like the trainer version of the Tupolev Tu-2 bomber, inexperience with JATO units, and late delivery of RD-10 engines.

The test pilots found the aircraft easy to fly, but the control forces were very high at speed and it lacked enough directional stability.

Enlarging the vertical stabilizer cured this last problem and hydraulic boosters were fitted for the control system.

[10] The Su-13, (Samolyet KT), was the final attempt to further increase performance of the basic Su-9 design, using wing sections reduced from 11% to 9% thickness/chord ratio and swept tailplanes.

The aircraft was also fitted with a pair of Klimov RD-500 (unlicensed copies of the Rolls-Royce Derwent) engines with 15.6 kN (3,500 lbf) thrust each.

The armament was changed to three 37 mm Nudelman N-37 cannon, while drop tanks could be fitted underneath the wingtips.

[10] Data from Early Soviet Jet Fighters[6]General characteristics Performance Armament