The Sukhoi Su-9 (; USAF/DoD designation: Type 8) was an early jet fighter built in the Soviet Union shortly after World War II. The design began in 1944 and was intended to use Soviet-designed turbojet engines. The design was heavily influenced by captured German jet fighters and it was subsequently redesigned to use a Soviet copy of a German turbojet. The Su-9 was slower than competing Soviet aircraft and it was cancelled as a result. A modified version with different engines and a revised wing became the Su-11 (Samolyot KL), but this did not enter production either. The Su-13 (Samolyot KT) was a proposal to re-engine the aircraft with Soviet copies of the Rolls-Royce Derwent turbojet as well as to modify it for night fighting, but neither proposal was accepted. Design and development Su-9 In 1944, the Sukhoi design bureau (OKB) began designing a twin-engined fighter powered by two Lyulka TR-1 turbojets, known internally as the Samolyet or Izdeliye (item or product) K. The ultimate design was very probably influenced by a captured Messerschmitt Me 262, but the Su-9 was not a copy of the German aircraft. The Su-9 had an oval cross-section, all-metal stressed skin monocoque fuselage that housed a single cockpit. The pilot was protected by armor plates to his front, an armored seat back and a bulletproof windscreen for the bubble canopy. He was provided with an ejection seat, copied from that used in the Heinkel He 162. The aircraft carried a total of of fuel in two bladder tanks, one each ahead and behind the pilot. The low-mounted, straight wing had a single-spar and a slight dihedral of 4°20'. The outer flaps were split and could act as air brakes. The Su-9 was the first Soviet aircraft to use hydraulic-powered controls. A Soviet copy of the Junkers Jumo 004B turbojet, known as the RD-10, was hung under each wing in a streamlined nacelle. The aircraft had a tricycle undercarriage that retracted into the fuselage. The Su-9 was designed with a very high wing loading which increased the aircraft's speed and reduced its dimensions. 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. These reduced the take-off distance by nearly 50 percent and a braking parachute was fitted to reduce the landing