Sukhoi Su-9 (1946)

Sukhoi Su-9

Company type	Military aircraft
Industry	Aerospace
Founded	1944
Headquarters	Soviet Union
Products	Jet fighter aircraft

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This entry covers the initial aircraft designated Su-9. For the subsequent supersonic interceptor, see Sukhoi Su-9

Sukhoi Su-11 (1947) redirects here. For the later interceptor model, see Sukhoi Su-11

The Sukhoi Su-9 (Russian: Самолёт K, lit. 'Aircraft K'; known by the USAF/DoD as Type 8) was an early Soviet jet fighter developed shortly after the conclusion of World War II. Initiated in 1944, its design aimed to utilize domestically produced turbojet engines. The aircraft’s configuration drew considerable inspiration from captured German jet fighters and was subsequently adapted to incorporate a Soviet-produced version of a German turbojet engine. Despite this, the Su-9's maximum speed lagged behind competing Soviet designs, leading to the project's cancellation. An evolved variant, designated Su-11 (Samolyot KL), featured alternative engines and a redesigned wing but also failed to enter mass production. Another proposal, the Su-13 (Samolyot KT), intended to equip the airframe with Soviet copies of the Rolls-Royce Derwent turbojet and adapt it for night operations; however, this concept remained unapproved.

Su-9

File:Bundesarchiv Bild 141-2497, Flugzeug Me 262A auf Flugplatz.jpg

The Su-9’s design was likely influenced by the Messerschmitt Me 262

In 1944, the Sukhoi design bureau (OKB) commenced work on a twin-engine fighter powered by two Lyulka TR-1 turbojets, internally referred to as Samolyet or Izdeliye K. While heavily inspired by a captured Messerschmitt Me 262, the Su-9 was not a direct replica of this German aircraft. The airframe featured an oval cross-section fuselage constructed with all-metal stressed skin monocoque techniques, accommodating a single pilot within an armored cockpit area. Protective measures included frontal armor plating, an armored seat back, and a bullet-resistant windshield beneath a bubble canopy. The pilot's ejection seat was modeled after that used in the Heinkel He 162. Fuel capacity totaled approximately 1,350 kilograms (2,980 lb), stored in two bladder tanks positioned before and behind the cockpit.

The low-mounted straight wings incorporated a single spar and exhibited a slight dihedral angle of 4°20'. Split outer flaps served dual functions as air brakes when deployed. Notably, the Su-9 was the first Soviet aircraft equipped with hydraulically powered flight controls. Each wing carried a streamlined nacelle housing an RD-10 engine—a Soviet copy of the Junkers Jumo 004B turbojet. The landing gear followed a tricycle configuration retracting into the fuselage.

Designed with high wing loading to enhance speed and reduce overall size, this approach resulted in increased takeoff and landing velocities. To mitigate this, provisions were made for two JATO bottles (producing 11.27 kN thrust for eight seconds) mounted on either side of the fuselage, effectively halving takeoff distance. Additionally, a braking parachute was installed to shorten landing runs.

Armament was concentrated in the nose section and consisted of one 37 mm Nudelman N-37 autocannon along with two 23 mm Nudelman-Suranov NS-23 autocannons. The N-37 could be swapped for a larger 45 mm Nudelman-Suranov NS-45 cannon if required. Ammunition loads included 100 rounds per NS-23 gun and 40 rounds for the N-37. The fighter could carry two 250 kg FAB-250 high-explosive bombs beneath the forward fuselage; however, installation of these bombs necessitated removal of the N-37 cannon.

Due to delays in readiness of the TR-1 engines by late 1945, Pavel Sukhoi proposed substituting them with Jumo 004 engines, which received approval on December 15th. A full-scale mockup passed inspection on February 16th, 1946, followed by an order from the Council of People's Commissars on February 26th mandating flight tests to commence by November 1st. This schedule slipped because Sukhoi's bureau was occupied with other priorities such as developing a trainer variant of the Tupolev Tu-2 bomber, unfamiliarity with JATO systems, and late delivery of RD-10 engines.

The initial prototype reached completion in mid-October and undertook its maiden flight on November 13th. Test pilots reported favorable handling characteristics but noted excessive control forces at high speed and insufficient directional stability. Enlarging the vertical tail resolved stability issues while hydraulic boosters were added to ease control inputs.

Public unveiling occurred during an aerial demonstration at Moscow’s Tushino Airfield on August 3rd, 1947, followed by commencement of state acceptance trials three days later. Flight testing concluded on May 25th, 1948 after completing 136 sorties. The aircraft achieved a maximum velocity of 885 kilometers per hour (550 mph) at 8,000 meters (26,250 ft) altitude and sustained flight endurance of one hour and forty-four minutes. It exhibited stable handling even with one engine shut down.

Although recommended for production initially, its performance lagged behind contemporaries such as the Mikoyan-Gurevich MiG-9 and Yakovlev Yak-15; consequently, authorities decided against mass manufacturing and terminated development.

Plans for a two-seat trainer variant designated Su-9UT were considered during 1946 but subsequently abandoned. This version would have featured tandem cockpits with separate canopies for instructor and trainee positioned forward and aft respectively. Armament would have been reduced to two Berezin B-20 autocannons (20 mm caliber) each supplied with one hundred rounds while armor protection was eliminated to reduce weight.

Su-11

In 1946, development began on another prototype designed to incorporate the Yakovlev-engineered variant of the afterburning RD-10F engine. Nevertheless, wind tunnel evaluations of the Su-9 conducted in September indicated that drag could be minimized by positioning the engine nacelles within the wing rather than beneath it. Additionally, the wing tips were redesigned to employ an alternative airfoil profile that greatly mitigated Mach tuck effects. These adjustments necessitated a complete redesign of the wing structure; the wing spar was reshaped into an inverted U configuration to house the engines, and slotted flaps replaced the previously used simple flaps. The tailplane was given a 5° dihedral angle to elevate it above the engine exhaust stream.

Prior to completing this prototype, Sukhoi received instructions to install Lyulka TR-1 turbojet engines originally planned for the Su-9. This version was designated Su-11 and referred to as Samolyet KL within the OKB. Each TR-1 engine produced only 12.7 kN (2,865 lbf) of thrust, falling short of the 15 kN (3,300 lbf) target. The aircraft’s maiden flight occurred on 28 May 1947, and it also took part in the Tushino flypast that August. Although capable of reaching a maximum speed of 940 km/h at sea level, flight tests revealed deficiencies in longitudinal stability at higher velocities. Attempts to resolve these issues by modifying wing/nacelle fillets and extending engine nacelles were unsuccessful. Combined with delays in producing reliable TR-1 engines, these challenges ultimately led to cancellation of the program.

Su-13

The Su-13, known as Samolyet KT, represented the final effort to enhance performance beyond the original Su-9 design. This involved reducing wing thickness-to-chord ratio from 11% to 9% and incorporating swept tailplanes. Powerplant upgrades included two Klimov RD-500 engines—unlicensed derivatives of the Rolls-Royce Derwent—each delivering 15.6 kN (3,500 lbf) thrust. Armament was revised to three 37 mm Nudelman N-37 cannons, with provision for underwing drop tanks mounted at the wingtips. A night fighter variant equipped with a Torii radar system was also considered; however, this required substantial structural modifications to accommodate radar installation. Neither version progressed beyond preliminary design stages.

Operators

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• Soviet Air Force

Variants

• Su-9UT – Proposed two-seat trainer variant that was never constructed.
• Su-11 (Samolyet KL) – Su-9 modification featuring redesigned wings and Lyulka TR-1 engines; one prototype completed.
• Su-13 (Samolyet KT) – Su-9 adapted with Klimov RD-500 powerplants; night fighter model proposed but neither built.

Specifications (Su-9)

File:Sukhoi Su-9 (1946) 3-view.svg

Su-9

References

• Gordon, Yefim. Early Soviet Jet Fighters. Hinckley, Leicestershire, UK: Midland, 2002. ISBN 1-85780-139-3.
• Gunston, Bill. The Osprey Encyclopedia of Russian Aircraft 1875–1995. London: Osprey, 1995. ISBN 1-85532-405-9.

External links

• Information on Sukhoi Su-9, −11, and −13 at the Sukhoi Company Museum