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The Sukhoi Su-9, Su-11, & Su-15

v1.0.4 / 01 oct 15 / greg goebel

* Although the Soviet Sukhoi aircraft design bureau of World War II was disbanded in the late 1940s, in the early 1950s the organization made a comeback, producing a series of jet interceptors -- beginning with the Sukhoi "Su-9", which would lead to the improved "Su-11" and, by a roundabout route, the "Su-15", with these aircraft playing a significant role in the air defense of the USSR. This document provides a history and description of the Su-9/11 and Su-15.

Sukhoi Su-15 Flagon


[1] SU-9 ORIGINS
[2] SU-9 / SU-9U
[3] SU-11 / SU-9 & SU-11 IN SERVICE
[4] SU-9-SERIES MODIFICATIONS, SPECIAL VARIANTS, & ONE-OFFS
[5] SU-15 ORIGINS / SU-15 DESCRIBED
[6] SU-15T & SU-15TM / SU-15UM & SU-15UT TRAINERS
[7] SU-15 IN SERVICE / MISCELLANEOUS VARIANTS
[8] COMMENTS, SOURCES, & REVISION HISTORY

[1] SU-9 ORIGINS

* Pavel Osipovich Sukhoi started out his work in aircraft design in the experimental design bureau (OKB in its Russian acronym) run by the prominent Andrei N. Tupolev. After the German invasion of the USSR in the summer of 1941, Sukhoi obtained his own OKB, but none of the aircraft designed by his organization entered large-scale service with the Red Air Force.

After the end of the conflict, the Sukhoi OKB developed a twin-engine jet fighter, the "Su-9", with a broad resemblance to the German Messerschmitt Me-262 fighter, but neither the Su-9 nor its slightly improved derivative, the "Su-11", entered production. The OKB then developed a prototype of a jet twin-engine swept-wing interceptor, the "Su-15", which was notable for being in competition for the title of the ugliest jet combat aircraft ever built. It was lost in a flight accident on 3 June 1949. Given the poor track record of the Sukhoi OKB, the loss of the Su-15 was the straw that broke the camel's back: the organization was disbanded.

Pavel Sukhoi didn't call it quits, however. Following the death of Soviet dictator Josef Stalin in 1953, Sukhoi successfully lobbied to take charge of a revived Sukhoi OKB, which would prove highly successful. Ironically, the new Sukhoi organization would end up producing the Su-9, Su-11, and Su-15 -- but only as entirely different aircraft. The original machines bearing those designations had never entered production, and the Soviets saw no reason not to recycle the designations.

* The first task assigned to the revived Sukhoi OKB was development of a new tactical fighter and a new interceptor, with both machines based on the advanced AL-7F afterburning turbojet, then in development at the engine OKB run by Arkhip Lyulka. Following recommendations from the state Central Aerodynamics & Hydrodynamics Institute (TsAGI in its Russian acronym), the Sukhoi OKB came up with two fighter designs that were very similar except for different wing configurations:

Both machines had a "stovepipe" arrangement, with the inlet in the nose for the AL-7F engine and the exhaust in the rear; swept tail surfaces; a bubble canopy; and tricycle landing gear. The swept wing S-1 configuration provided better low-altitude handling, making the design suitable for the tactical fighter role. Development was authorized, resulting in the "Su-7" family of strike fighters, discussed elsewhere. The delta wing proved a fairly good choice for high-altitude performance, making it better suited to the interceptor mission. The T-1 delta-winged tactical fighter concept was abandoned in 1955, even as the T-3 interceptor effort moved into higher gear.

A static-test T-3 airframe was ready by the end of 1955, with the initial flight of a prototype on 26 May 1956, with test pilot Vladimir N. Makhalin at the controls. A month later, on 24 June 1956, the T-3 prototype went through its paces at the annual Aviation Day airshow at Tushino. Western observers took note of the interceptor, with NATO assigning it the codename of "Fishpot" -- which would become "Fishpot-A" when successors were introduced.

* The T-3 was developed by a design team under Nikolay Polenav and his deputy Aleksandr Vishnevskiy. It featured mid-mounted delta wings, and a swept tail assembly -- a configuration nicknamed the "balalaika", after the famous Russian "banjo" featuring a triangular box. The same configuration was also used for the Mikoyan MiG-21 fighter, which was not surprising, since it was the configuration recommended by TsAGI; it was one of the most straightforward and obvious configurations for a supersonic jet aircraft. At the outset, the T-3 featured a cone in the upper lip of the engine intake for its Almaz-3 air-intercept radar system, though the radar itself wasn't fitted until well into the flight-test program.

Trials showed the T-3 to have excellent performance of up to 2,100 KPH (1,305 MPH), though it was slightly overweight and endurance was under spec. A number of its systems needed work, particularly the AL-7F engine, which was still in development and proving unreliable. A second prototype took to the air in late June 1957. This machine, the "PT-7" -- where the "P" stood for "perekvatchik (interceptor)" and the "T" for "triangular" as before -- featured an uprated AL-7F-1 engine, plus an Almaz-7 radar system, which required a large cone in the top of a raked engine inlet and a small cone in the bottom, giving the machine a distinctly predatory appearance that even the Soviets, not noted for being fussy about aircraft aesthetics, found evil-looking.

Sukhoi T-3, T-7

The PT-7 was regarded as the production configuration, and three pre-production prototypes, designated "PT-8", were built by State Factory Number 153 at Novosibirsk in Siberia. They were shipped by rail to the Sukhoi OKB in Moscow for flight test -- but as it turned out, there were second thoughts that the PT-7 configuration was appropriate for production, and only one of these three machines actually flew in its original configuration.

* The PT-7 didn't end up being production configuration because the Kremlin was becoming extremely annoyed at high-altitude reconnaissance overflights of the Soviet Union by Western spy planes -- in particular, by the Lockheed U-2 "Angel" spyplane, which performed its initial overflight of the USSR on 4 July 1956, only weeks before the first flight of the T-3. The word came down in August 1956 to redesign the interceptor to achieve a substantially higher ceiling to catch the intruders. Work began on the redesigned aircraft, the "T-43", in December 1956; the machine was to retain the balalaika configuration and use the AL-7F-1 engine, but it was to be fitted with a liquid-fuel rocket booster to allow it to reach very high altitudes. There was also consideration of "mass injection", using water dumped into the turbojet to provide boost thrust.

The T-43 prototype performed it first flight on 10 October 1957, with well-known test pilot Vladimir S. Ilyushin at the controls. The booster rocket development program did not go well; the T-43 went into trials without it, and in fact the rocket booster effort would be eventually axed. Nothing came of the mass-injection proposal, either -- mass injection could provide hefty thrust, but it could be tricky both to use and maintain. The T-43 did, however, feature a new inlet design, the original concepts not being very well optimized for high-speed flight. The new inlet was circular, with a shock cone in the center that was moved forward or back to optimize airflow at various speeds. The shock cone was also intended to house an air intercept radar.

The T-43 proved everything hoped for it, climbing to 21,500 meters (70,550 feet) on 20 October on AL-7F-1 power alone -- which is likely one of the reasons the booster rocket program was abandoned. Three days later, on 23 October 1957, the T-43 broke Mach 2, being clocked at 2,200 KPH (1,365 MPH). The Kremlin was having some doubts about the importance of manned combat aircraft, the future seen to belong to missiles, but the excellent performance of the T-43 kept the program alive.

Six more T-43 prototypes were flown in various configurations; although one was lost in a crash in July 1959, the pilot being killed, the otherwise successful progress of the test program resulted in approval for production in October 1960, the aircraft receiving the service designation of "Su-9".

In reality, early production had already gone into service a year earlier. The Su-9s didn't fly with the Red Air Force, the Soviets having an entirely separate service for national air defense, the "Protivo Vozdusdushnoi Oborony (PVO / Homeland Air-Defense Organization)", which operated radar networks, surface-to-air missiles (SAMs), and interceptors to protect the USSR from airborne intruders. A formation of Su-9s performed a fly-past at the Tushino airshow on 9 July 1961, where Western observers got their first look at the machine. NATO assigned the type the codename of "Fishpot-B".

BACK_TO_TOP

[2] SU-9 / SU-9U

* The Su-9 was a powerful and sophisticated aircraft, and to no surprise in hindsight its service introduction was not entirely trouble-free. Aircrew were not familiar with flying such a fast machine, and ground crews were not familiar with maintaining such a relatively complicated one; the inevitable teething problems, particularly a range of troubles with the AL-7F-1 engine, didn't help matters any. One unforeseen problem was that the Su-9 was operated on runways that weren't normally used for such a relatively heavy aircraft; the Su-9 had a tendency to tear up the pavement. That led to "foreign object ingestion" and engine damage, until the runways were reinforced and procedures put into place to make sure runway debris was swept off on a regular basis.

At the outset, the Su-9's accident rate proved intolerably high; it wasn't until the mid-1960s, following a list of production changes and improvements, that it came down to reasonable levels. To deal with pilot training issues, the Sukhoi OKB developed a tandem two-seat, dual-control operational conversion trainer version of the Su-9, the "Su-9U" (AKA "U-43"). Initial flight of the prototype, a conversion of a single-seat Su-9 developmental aircraft, was on 25 January 1961, with OKB test pilot Y.K. Kukushev at the controls, with production and service introduction following before the end of the year. It was nicknamed a "sparka", a general term for a dual-control trainer. NATO assigned it the codename of "Maiden".

* As noted, in general configuration of the Su-9 was a single-seat, single-engine aircraft, with a nose intake, delta wings and a swept tail assembly. It was mostly made of aviation aluminum alloys, with some steel parts. It featured a bubble-style canopy and tricycle landing gear.

The Su-9 was originally fitted with the AL-7F-1 engine, which provided 61.2 kN (6,240 kgp / 13,760 lbf) max dry thrust and 90.2 kN (9,200 kgp / 20,280 lbf) afterburning thrust. Production then moved up to the AL-7F-1-100, with the same thrust, but operating lifetime doubled to 100 hours. The engine was later further updated to the AL-7F-1-150 and AL-7F-1-200, again with the same thrust, but engine lifetimes of 150 and 200 hours respectively. Even 200 hours is unimpressive by modern standards, but the short lifetime was seen as an acceptable price for Mach 2 performance.

The movable cone in the engine inlet was controlled by an automatic electrohydraulic system. There were two hydraulically-operated auxiliary inlet doors on each side of the nose, for a total of four doors; they were not included in the prototypes and early production machines. The main engine was started by a gasoline (not jet fuel) powered starter motor. A manually-actuated carbon-dioxide engine fire-extinguisher system was fitted.

Sukhoi Su-9

The Su-9 featured three fuel tanks in the fuselage and fuel tanks in the wings. Initially, total internal fuel capacity was 3,060 liters (807 US gallons), though later production increased it to 3,780 liters (997 US gallons). There were twin "wet" pylons arranged side-by-side on the belly, each capable of carrying an external tank with a fuel capacity of 600 liters (158 US gallons).

The two-spar wings had a leading-edge sweep of 60 degrees, an anhedral droop of 2 degrees, and no angle of incidence. Somewhat unusually for Soviet combat jets, they had no wing fences. They had one-piece Fowler-type flaps with ailerons outboard, both hydraulically actuated. The tailplanes were one-piece all-moving "stabilators", featuring the anti-flutter weight "barbs" often seen on Soviet combat jets. The tailfin featured a conventional rudder assembly; tail flight controls were also hydraulically actuated. There were four hydraulically-operated airbrakes arranged in an "X" pattern around the rear fuselage.

All landing gear assemblies featured single wheels and were hydraulically retracted. The nose gear retracted forward, while the main gear pivoted from the wings towards the fuselage. The nose gear castored, with ground steering by differential use of mainwheel brakes; the brakes were pneumatically actuated. The nose gear gave the aircraft a nose-up attitude on the ground to provide the angle of incidence for takeoff. A ribbon-style brake parachute was stowed under the exhaust.

The Su-9 featured three hydraulic systems: a primary system for the landing gear, intake cone, auxiliary inlet doors, flaps, airbrakes; plus primary and backup systems for the flight control surfaces. There were primary and backup pneumatic systems, being used for brakes and cockpit sealing, with late production using the pneumatic system for emergency landing gear and flap actuation.

Along with the two belly pylons, there were two stores pylons under each wing, the wing pylons being committed to carriage of up to four air-to-air missiles (AAMs). The initial weapon was the RS-2-US AAM (NATO AA-1 Alkali), which was relatively crude "beam rider", riding down a narrow radar beam while the pilot kept the target in the radar crosshairs. Of course, it was only possible to engage one target at a time. Later an infrared heat-seeking version of the same missile was produced, being designated the R-55, and Su-9s then carried two beam-riders and two heat-seekers.

In early Su-9 production, there were provisions for fitting a Nudelman-Rikhter NR-30 30 millimeter cannon in each wingroot, but no Su-9s carried cannons in service. In later production the cannon provisions were eliminated, with fuel tanks inserted in their place. Early production machines had a blast plate on each side of the fuselage where the cannon muzzle was supposed to be; the blast plates were deleted when the cannon provisions were eliminated. There was a gun camera in the right wing.

   SUKHOI SU-9 "FISHPOT-B":
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                8.54 meters         28 feet
   wing area               34 sq_meters        366 sq_feet   
   length (with pitot)     18.056 meters       59 feet 3 inches
   height                  4.82 meters         15 feet 10 inches

   empty weight            7,675 kilograms     16,920 pounds
   normal loaded weight    11,440 kilograms    25,220 pounds
   MTO weight              12,510 kilograms    37,580 pounds

   max speed at altitude   2,230 KPH           1,385 MPH / 1,205 KT
   service ceiling         20,000 meters       65,620 feet
   range with tanks        1,800 kilometers    1,120 MI / 970 NMI
   _____________________   _________________   _______________________

The bubble canopy slid back to open. The cockpit was pressurized and climate-conditioned, with the pilot sitting on a Sukhoi-designed ejection seat. Initial production had the KS-1 ejection seat, with minimum safe ejection speed of 500 KPH (310 MPH), minimum safe ejection altitude of 150 meters (500 feet), and maximum safe ejection speed of 850 KPH (530 MPH). Later production used the KS-2 seat, which increased the maximum safe ejection speed to 1,000 KPH (620 MPH); final Su-9 production used the slightly improved KS-2A seat. Later, all surviving Su-9s were refitted with the KS-3 seat, with a maximum safe ejection speed of 1,100 KPH (680 MPH) and a minimum safe ejection altitude of 30 meters (100 feet).

In addition to the RP-9U radar system in the shock cone, the Su-9's avionics included a gyrocompass, automatic direction finder, navigation beacon system receiver, radar altimeter, VHF communications radios, and Lazur datalink receiver for ground-controlled intercepts (GCI). PVO doctrine tended to keep interceptors under rigid ground control, with the pilot following display indicators to keep on a guidance track. Later production also had a flight data recorder, with older machines refitted with this item.

* The Su-9U two-seat trainer was generally similar to the single-seat Su-9 but had a fuselage stretch of 60 centimeters (2 feet) to accommodate the second cockpit, with the empty weight increased by 630 kilograms. The two cockpits had individual rear-hinged clamshell canopies. The Su-9U was combat-capable, though warload was reduced to two RS-2-US AAMs; both cockpits had displays for the radar, with the aircrew communicating over an intercom. Although Soviet two-seat conversion trainers often had a periscope over the back cockpit that popped up when the landing gear was extended to improve the back-seater's forward view, the Su-9U was not fitted with such a device.

Sukhoi Su-9U

Over 1,000 Su-9s were built at Factory Number 153 in Novosibirsk into 1962. Su-9 production also took place at Moscow Machinery Plant Number 30, which built a total of 162 Su-9s and all 50 Su-9U conversion trainers. No Su-9s were exported.

Except for the initial bugs, the Su-9 was generally liked by its pilots. Its performance was outstanding for the time -- Vladimir Ilyushin set a world altitude record in the first T-43 prototype in 1959, and the type also set a number of world speed records. Although it had a long takeoff run and a hot landing speed, neither being particularly desireable features, its handling was very nice once it was in the air. The Su-9 was regarded as a machine that simply liked to fly: there were two cases where pilots panicked and ejected, with the unoccupied aircraft then remaining in the air until they ran out of fuel, and then gliding to a landing in open spaces. One was recovered almost completely undamaged, except for crushed external tanks.

BACK_TO_TOP

[3] SU-11 / SU-9 & SU-11 IN SERVICE

* Early in the T-3 program, there were experiments with different radar fits. One machine was built from scratch to carry a more powerful radar, with the resulting "T-47" prototype performing its first flight on 6 January 1958. It looked much like the Su-9, the main difference being a longer nose with a wider intake and much bigger intake cone to accommodate the new radar. This machine had wingroot cannon and no provision for AAMs; it also had a dogtooth wing. Since the emphasis at the time was increasingly on AAM-armed aircraft, the T-47 effort was shelved after the machine had performed 15 flights.

That didn't mean that work on a T-3 with better radar was given up, with what was supposed to have been the initial production Su-9 converted to a configuration similar to that of the initial T-47 prototype -- with modified nose, big intake cone, dogtooth wings, and a cannon in each wingroot -- but also with the capability of carrying AAMs. This machine was known as the "PT8-4", since it followed the three PT8 pre-production machines mentioned earlier. It performed its initial flight on 21 February 1958.

The PT8-4 wasn't seen as quite what was required either, but it did lead to another, similar prototype, the "T-47-3", converted from the old ugly PT-7 prototype, with the new "Oryol (Eagle / NATO Spin Scan)" radar for the big R-8M (NATO AA-3 Anab) AAM, with substantially more range and hitting power than the RS-2-US / AA-2 Alkali AAM. The T-47-4 could carry one AAM under each wing -- usually one with radar guidance, the other with infrared heatseeking guidance. The T-47-3 had the new longer nose and big intake cone, though it didn't have the cannon and dogtooth wing; the T-47 and PT8-4 were the only T-3-series machines to feature cannon.

The T-47-3 performed its first flight on 25 December 1958. It was strictly an aerodynamic prototype, lacking radar, but the design was seen as promising, and so five more T-47 prototypes were built, all being conversions of other airframes -- trying to get a detailed accounting of prototype T-3 machines is troublesome, because of their tendency to repeatedly pop up in different forms. The type was approved for production as the "Su-11" in late 1961 and went into PVO service in early 1962. However, it ended up in competition with the Yakovlev Yak-28P "Firebar" twin-engine interceptor, and only 108 production Su-11s were completed by the time manufacture ended in 1965. The variant was assigned the NATO codename of "Fishpot-C". Once again, none were exported.

The Su-11 was 60 centimeters (2 feet) longer than the Su-9; its empty weight was about 900 kilograms (1,985 pounds) more, bringing it to 8,562 kilograms (18,875 pounds). The Su-11 featured an AL-7F-2 engine, with the same dry thrust as the AL-7F-1 but about 10% more afterburning thrust. In addition to the long nose, another distinguishing characteristic relative to the Su-9 was a prominent conduit on each side of the upper fuselage. Along with the Oryol radar, there were some improvements in kit, such as a Sirena-2 radar warning receiver, and the KS-3 ejection seat installed as standard. The Su-11 was a more mature aircraft than the initial production Su-9, and so the Su-11's introduction to service was not as painful. However, some sources claim that it was noseheavy, and its handling could be troublesome.

Sukhoi Su-11

* The Su-9 and Su-11 were mainstays of the PVO from the mid-1960s and into the 1970s. They were often scrambled against intruders into Soviet airspace; there are no clear reports of any "kills" against intruders, except for what have been described as "reconnaissance balloons". The story of these balloons is confusing: the Americans conducted two sessions of spy balloon flights over the USSR in the 1950s, with both programs proving dismal failures. Once spy satellites came into operation in the early 1960s, there was no obvious reason to conduct any more balloon reconnaissance flights; however, Russian sources document plenty of encounters with Western balloons after the 1950s, and there's no reason to doubt that PVO interceptors were chasing after some kind of gasbags floating through the skies.

There's the possibility that PVO pilots were simply hunting down stray weather or research balloons -- but there's no ruling out that there were other covert Western balloon programs that have been forgotten, though given the deployment of spy satellites and the futility of the 1950s balloon reconnaissance efforts, what their rationale might have been is unclear. Who knows? It might have been to determine the capabilities of the Soviet air-defense system; maybe the balloons were supposed to be shot down, relaying information on Soviet radar signals before their destruction. In any case, the Su-9 and Su-11 were phased out from the mid-1970s, with some Su-9s converted to radio-controlled targets. A number remain on static display, but none are flying any more.

BACK_TO_TOP

[4] SU-9-SERIES MODIFICATIONS, SPECIAL VARIANTS, & ONE-OFFS

* There were a number of special variants and one-off derivatives of the Su-9 and Su-11. During early development of the aircraft line, there was thought of replacing the AL-7F engine with twin Tumanskiy R11F-300 afterburning turbojets, the R11F being the powerplant of the single-engine Mikoyan MiG-21. Each R11F-300 could provide a maximum of 41.2 kN (4,200 kgp / 9,260 lbf) dry thrust and 60.0 kN (6,120 kgp / 13,490 lbf) in afterburner.

Sukhoi T-5

The "T-5", as the prototype was known, was modified from the original T-3 prototype. It performed its initial flight on 18 July 1958, with Vladimir Ilyushin at the controls. The T-5 had the balalaika configuration and the circular inlet with center shock cone, but it also had a distinctively swollen rear fuselage, with the twin R11F-300 engines installed side-by-side. The T-5 proved to have an impressive excess of thrust, being so powerful that an incautious test pilot could have easily flown the machine to destruction. The design suffered from center of gravity shifted well to the rear, ensuring that the aircraft was dangerously unstable. The test program was abandoned in May 1959, though the experience would come in handy later.

The Su-9 was used for a number of trials programs, one of the most interesting being an ejection seat testbed converted from the Su-9U trainer prototype. This machine featured a special ejection seat compartment where the back-seater had originally sat.

* The Sukhoi OKB worked on a number of other interceptor designs in parallel with Su-9 / Su-11 development. The "P-1" grew of studies in the mid-1950s for a two-seat interceptor with a powerful radar, with the project approved for further development in late 1955, leading to the initial flight of the sole prototype on 12 July 1957, with OKB test pilot Nikolay Korovushkin at the controls. The P-1 had some similarities to the T-3 in featuring the balalaika configuration and T-3 landing gear arrangement, but along with the two-seat cockpit -- with separate clamshell canopies for the two crewmen -- it had a solid nose for the powerful Pantera radar, with raked elliptical engine inlets alongside the fuselage. The inlet design wasn't one that inspired much confidence.

Sukhoi P-1

The P-1 also had a wing with a dogtooth and wingtips that were slightly "cranked", with lesser sweep than the rest of the wing. Armament was to be two K-7S AAMs, then in development, and 50 unguided rockets, the unguided rockets fired from ports around the nose that were normally closed off by doors. It was to have been powered by single Lyulka AL-9 engine -- a twin-engine "P-2" was also considered though not approved for development -- but lack of availability meant the P-1 prototype was powered by the AL-7F-1. Since the P-1 was heavier than the Su-9, the P-1 was underpowered. The Soviet military demonstrated no interest in the project and it was abandoned, with the prototype eventually scrapped, though the ideas embodied in the design would also come in handy later. The K-7S AAM did not reach production.

The P-1 not finding any favor, the Sukhoi OKB moved on to the "T-37" design, which could be described as a "Super Su-11" -- a single-seat interceptor very similar to the Su-11, but with a more powerful Tumanskiy R15-300 engine and more sophisticated avionics, including a powerful radar in a long, spindly intake cone. A T-37 prototype was in construction when the program got the axe in the spring of 1959, with the machine then scrapped before it was completed.

Development then went on in turn to another single-seat interceptor, the "T-49", which again had the balalaika configuration, mated to an unusual nose arrangement. It appears that Sukhoi engineers were getting frustrated trying to figure out a way to mount larger radars and still have an effective engine inlet configuration; the T-49 featured a solid nose, but with two large inlets along each side of the nose. A prototype was built and took to the air in January 1960. Its performance was regarded as good, but it was damaged in a ground accident in April 1960; for whatever reasons, it never returned to flight status.

BACK_TO_TOP

[5] SU-15 ORIGINS / SU-15 DESCRIBED

* The reason the T-49 never flew again was because interest had once again moved on, this time to a design effort that would actually lead to a production weapon system. In the early 1960s, the Sukhoi OKB seemed to be falling out of favor, with fighters and interceptors from the Mikoyan and Yakovlev OKBs increasingly preferred by the Red Air Force and PVO. In order to get back on the leading edge, the Sukhoi OKB began work on an advanced supersonic interceptor, with the OKB codename of "T-58".

As it emerged, the T-58 was a single-seat aircraft, retaining the balalaika configuration of the T-3 series, but it had the solid nose implemented in the sole P-1 prototype, allowing it to carry a powerful radar. The side-mounted intakes of the T-58 were of much improved configuration over those of the P-1, featuring a dee configuration with variable inlet ramps. Both single-engine and twin-engine concepts were considered, with the twin-engine configuration given the designation of "T-58D"; the twin-engine configuration was preferred and work on the single-engine configuration was abandoned. The designated powerplant was the Tumanskiy R11F2-300, trialed on the single T-5 prototype.

State approval for full development was granted in early 1962, and the first T-58D prototype performed its initial flight on 30 May 1962, with Vladimir Ilyushin at the controls. There were problems with obtaining a satisfactory radar; failing to find any better solution, an updated Oryol radar, the Oryol-58DM / RP-15, was selected. The trials went well, though an extensive number of changes were required to get the machine up to service spec.

In April 1965, approval was granted for production of the "Su-15", as the T-58D was designated in service -- there would never be an "Su-13", aircraft people have a superstitious streak, nobody wanted to fly an aircraft with that number code. The first preproduction aircraft performed its initial flight in March 1966, with full production ramping up in midsummer and formal introduction to service with the PVO in 1967. The production Su-15 put on a public flight display at the Moscow-Domodedovo Airport airshow on 9 July 1967; NATO assigned the type the codename of "Flagon", which became "Flagon-A" when later variants were introduced.

Sukhoi Su-15 (early production)

* The Su-15 didn't look much like the Su-9/11, at least from the side, but it clearly owed a great deal to its predecessors:

Of course, the twin engine configuration was entirely new. The dee-type inlets featured a variable ramp in the bottom -- not on the sides -- and a blow-in door along each inlet, all under the direction of an electrohydraulic control system. There was a titanium firewall between the two engines. Along with the Oryol radar, avionics were generally updated.

   SUKHOI SU-15 "FLAGON-A":
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                8.616 meters        28 feet 3 inches
   wing area               34.56 sq_meters     372 sq_feet   
   length (no pitot)       20.54 meters        67 feet 5 inches
   height                  5.0 meters          16 feet 5 inches

   empty weight            10,220 kilograms    22,530 pounds
   normal loaded weight    16,520 kilograms    36,420 pounds
   MTO weight              17,094 kilograms    37,685 pounds

   max speed at altitude   2,230 KPH           1,385 MPH / 1,205 KT
   service ceiling         18,500 meters       60,695 feet
   range with tanks        1,550 kilometers    960 MI / 835 NMI
   _____________________   _________________   _______________________

The Su-15 led to the Sukhoi OKB obtaining a bit of revenge on the rival Yakovlev design bureau. The SU-15 was a clear step ahead of the Yak-28P and in an attempt to keep with the Sukhoi OKB, the Yakovlev OKB developed a derivative of the Yak-28P, the "Yak-28-64", with a configuration like that of the Su-15 -- with twin engines in the fuselage and intakes on the sides of the fuselage, though the Yak machine had swept wings instead of delta wings. A few trial flights showed the performance of the Yak-28-64 was inferior even to the Yak-28, and the program was swiftly abandoned.

BACK_TO_TOP

[6] SU-15T & SU-15TM / SU-15UM & SU-15UT TRAINERS

* The original production Su-15 was seen from the outset as strictly an interim configuration, with development work underway even before service introduction to get the machine up to a better standard. Later production featured a new "cranked" wing, with wingtips at a shallower sweep of 45 degrees, just outboard of the wing fence. The wing also featured "blown flaps" or "boundary-layer control (BLC)" system, with engine air bleed blown over the flaps to keep them effective at lower speeds; the improvements made takeoffs and landings less "hot" and intimidating. Unfortunately, the engines didn't provide enough bleed air to make the BLC system effective. The improved Su-15 was introduced in 1969; although it didn't receive a new variant code, since it was clearly different from the original Flagon-A, NATO assigned it the codename of "Flagon-D".

Although the Su-15 was supposed to have been fitted from the outset with an improved radar, as mentioned, troubles with radar development programs led to use of Su-11's Oryol radar. It was of course seen as strictly an interim fit; the plan was to update the aircraft with a more satisfactory radar in later production. The selection ending up being the Taifun (Typhoon) radar, a variant of the RP-25 Smerch-A radar developed for the Mikoyan MiG-25 "Foxbat". The first Su-15 with Taifun radar performed its initial flight on 31 January 1969, with Vladimir Krechetov at the controls. The updated aircraft was approved for production as the "Su-15T", with "T" for "Taifun".

The Su-15T featured a number of other enhancements as well, particularly Tumanskiy R13-300 engines, which had been developed for advanced models of the Mikoyan MiG-21. The R13-300 offered better specific fuel consumption and more thrust than the earlier R11F2-300 engines, each providing 40.2 kN (4,100 kgp / 9,040 lbf) max dry thrust and 64.7 kN (6,600 kgp / 14,550 lbf) afterburning thrust. The more powerful engines also permitted effective use of the BLC system -- of course, the Su-15T retained the cranked wing with blown flaps. Other changes included:

Missile armament was to be the new R-98 AAM, an improved version of the original R-8M series. The R-98 looked identical to the R-8M externally and was designated by NATO as the AA-3-A Advanced Anab.

* As it turned out, the initial production Taifun radar was unworkable and only ten Su-15Ts were built. The radar development OKB went back to the drawing board and came up with the workable Taifun-M (NATO codename Twin Scan) radar; after evaluation, aircraft production was resumed, with the machine given the updated designation of "Su-15TM". NATO assigned the variant the codename of "Flagon-E". When the original conical nosecone turned out to generate echoes from the powerful Taifun-M radar, the nosecone was changed to featured curved sides, with NATO codenaming the variant "Flagon-F".

Sukhoi Su-15TM

The Su-15TM was the definitive Flagon variant. In service it was fitted with an extra stores pylon inboard on each wing to carry an R-60 (NATO AA-8 Aphid) heatseeking dogfight AAM. The Su-15TM could also carry a UPK-23-250 cannon pack on each of the belly pylons, each pack containing a single GSh-23 twin-barrel "teeter-totter" cannon and 250 rounds of ammunition. While the Su-15 had been conceived in the days when it was believed that aircraft would stand off and blow adversaries out of the sky from long range with AAMs, combat experience had demonstrated that idea was not entirely realistic, and so the R-60 AAMs and cannon were added to improve dogfight capability. Older Su-15s still in service were retrofitted to carry the cannon pods.

   SUKHOI SU-15TM "FLAGON-F":
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                9.34 meters         30 feet 7 inches
   wing area               36.6 sq_meters      393 sq_feet   
   length (no pitot)       20.54 meters        67 feet 5 inches
   height                  4.843 meters        15 feet 11 inches

   empty weight            10,874 kilograms    23,970 pounds
   normal loaded weight    17,194 kilograms    37,905 pounds
   MTO weight              17,900 kilograms    39,460 pounds

   max speed at altitude   2,230 KPH           1,385 MPH / 1,205 KT
   service ceiling         18,500 meters       60,695 feet
   range with tanks        1,700 kilometers    1,055 MI / 920 NMI
   _____________________   _________________   _______________________

There were trials of the Su-15TM with ground attack stores such as bombs and unguided rocket packs carried on the belly pylons, with one even modified to carry a tactical nuclear weapon. However, the Su-15TM was generally unsuited to the attack role, and such stores were never carried in operational practice.

* The Flagon was a powerful and complex aircraft, and so, as with the Su-9, the decision was made to build a tandem two-seat conversion trainer variant to ease conversion to the type. The result was the "Su-15UT", which was a baseline Su-15 with a 45 centimeter (18 inch) fuselage stretch and a tandem cockpit arrangement like that of the Su-9U -- though it did have the pop-up periscope. The Su-15UT had no radar or datalink; it was not combat-capable and usually carried dummy missiles. NATO assigned the variant the codename of "Flagon-C".

Sukhoi Su-15UM

After the introduction of the Su-15TM, the decision was made to implement a conversion trainer based on that configuration, resulting in the "Su-15UM". It looked like a late-production Su-15TM with the tandem-seat cockpit arrangement, but it lacked the fuselage stretch of the Su-15UT. Once again, there was no radar, but it could carry R-60 AAMs and the cannon packs, giving it a limited combat capability. NATO assigned it the codename of "Flagon-G". The Su-15TM was the last of the Flagon series built, ending production in 1979. A total of 1,290 Flagons of all types was built, all at the Novosibirsk factory. As with the Su-9/11, all served with the PVO and none were exported.

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[7] SU-15 IN SERVICE / MISCELLANEOUS VARIANTS

* The Su-15 was a significant component of the PVO's interceptor strength from the mid-1970s through the 1980s, and it actually saw a surprising amount of action. There were encounters with the mysterious "reconnaissance balloons"; 1975 was recorded as a particularly active year for balloon intrusions, with 16 spotted and 13 destroyed, 5 of them by Su-15s. It should be noted that Russian sources claim that balloon overflights didn't stop then, with records of balloon shoot-downs as late as 1990.

The Su-15 also took on other intruders. On 20 April 1978, a Korean Air Lines (KAL) Boeing 707-321 on a flight over the polar regions from Paris to Seoul stumbled into Soviet airspace and raised a hornet's nest, with numbers of PVO interceptors scrambled to intercept. The airliner's crew ignored signals from Soviet aircraft flying alongside to follow and land, so an Su-15TM fired on it with an Aphid AAM, blowing off a wingtip and disabling an engine. The aircrew finally managed to land the jetliner on a frozen lake near Archangel, with the crew and passengers arrested and the badly damaged aircraft impounded.

Of the 109 on board, two had been killed and 13 injured, apparently when the damaged engine disintegrated. The survivors were eventually released; the aircraft was a writeoff and not returned. Some Russian sources suggest there was something suspicious about a jetliner straying off course by over a right angle, but Soviet authorities had their hands on the jetliner and made no comment that it was carrying surveillance gear. It seems more likely there was either something very wrong with the 707's navigation gear or the aircrew was grossly incompetent. As the saying goes: do not attribute to malice what could be just as easily attributed to stupidity.

* On 18 July 1981, a Canadair CL-44 air freighter entered Soviet airspace from over the Iranian border; it was registered with an Argentine air freight company and flown by a Swiss crew. An Su-15 intercepted the intruder and flew alongside it, with the Soviet pilot gesturing the crew to follow him to land. The CL-44's crew didn't like that idea, maneuvering in a threatening way and trying to get back across the border. The Soviet pilot was authorized to shoot the freighter down. Since he was very close, he couldn't fire an AAM without backing up and giving the intruder time to fly out of reach; lacking cannon, he simply clipped its tail, with the CL-44 falling to earth on Soviet territory, all the crew being killed. The Soviet pilot, a Captain V.A. Kulyapin, was forced to eject from his own crippled aircraft, receiving a medal for his dedication to his job.

* The most infamous incident took place on the night of 1 September 1983, when a KAL Boeing 747, flight "KE007" from Anchorage to Seoul, flew into Soviet airspace in the Far East. It was intercepted by two Su-15s whose pilots tried to get the jetliner crew to follow them and land, but there was no response. One of the Su-15s fired on it with cannons; again no response. The Su-15s were then ordered to destroy the intruder, and Major Gennadiy Osipovich pumped two Anab AAMs into it, telling ground control tersely: "The target is destroyed." The 747 fell into the Sea of Japan, with all 269 on board killed.

There was furious international outrage over the incident. There are conspiracy theories that claim the aircraft really was on a spy mission, but there's no credible evidence to support the idea. The aircraft was flying with its navigation lights on, which would not have be prudent if it was supposed to be on a secret mission; why the crew ignored the two Su-15s is a mystery that they took to their graves with them. It was very dark, with the Su-15s pilots unable to provide a positive identification of the jetliner type and nationality; possibly the 747's crew was snoozing, and simply didn't notice them.

* Despite its heavy use, the Su-15 was generally regarded as a "second-string" aircraft in PVO service, generally because its Taifun radar lacked "look-down shoot-down" capability -- it couldn't find or engage targets flying low in ground clutter. The Mikoyan MiG-23P had such a capability and was seen as the preferred asset, and of course once the much improved Sukhoi Su-27 entered service it outclassed the Su-15 in almost every respect. After the fall of the USSR, the Su-15 was quickly phased out of service, partly to comply with arms limitation treaties, though Ukraine kept theirs in service up to 1996.

No Su-15s are flying any more, but there are a number on static display. In 1995, there was a scandal in Russia in which a number of military officers were accused of trying to sell old Su-15s to Western museums as displays; the plot was a bust, with the principals arrested.

* Su-15s were used for a number of avionics, engine, and weapons trials. Three Su-15s were used for trials of the "UPAZ" universal inflight refueling tanker pack in the early 1970s, with two modified to carry the UPAZ pack and the other modified with a fixed inflight refueling (IFR) probe. One of the tanker aircraft was lost in an accident, but otherwise the trials went well. However, although the UPAZ pack entered the military inventory, no Su-15s carried it operationally, and no operational Su-15s were fitted with the probe. One Su-15 was fitted with a "sidestick controller" for trials in the early 1980s, with this aircraft also retaining the traditional stick control; it was lost in an accident.

Sukhoi T-58VD

A particularly interesting trials machine was a "short take-off & landing (STOL)" demonstrator based on the Su-15 and designated "T-58VD", where "VD" stood for "vertikalniye dvigateli (vertical engines)". It was modified to carry three Kolesov RD-36-35 "liftjets", mounted 10 degrees forward of the vertical in the center fuselage where the fuel tanks normally were. The liftjets were stubby turbojets that could each provide 23.1 kN (2,350 kgp / 5,180 lbf) thrust for a short period of time to help get the aircraft off the ground. The T-58VD looked much like a late-production Su-15, with the cranked wing and conical radome, but it had two covers on the back that hinged upward from the rear to allow airflow into the liftjets, and a set of louvers on the belly for the liftjet exhaust.

Since the T-58VD only had wing tanks, it didn't have much endurance, but it was strictly a demonstrator. Initial flight was on 6 June 1966, with Yevgeniy Soloviev at the controls. Soloviev flew the machine at the Moscow-Domodedovo airshow on 9 July 1967, with Western observers taking note of the variant and NATO assigning it the codename of "Flagon-B", though only one was ever built. The liftjet scheme more or less worked as desired, but carrying around three auxiliary engines was too much overhead, and nothing resembling the T-58VD ever entered operational service.

* There were concepts for further improved variants of the Flagon beyond the Su-15TM. An Su-15TM was refitted with the Gavrilov R25-300 turbojets with 40.2 kN (4,100 kgp / 9,400 lbf) max dry thrust and 67.2 kN (6,850 kgp / 15,650 lbf) afterburning thrust as a prototype for an "Su-15bis" -- "bis" being Latin / French for "encore" or, effectively, "plus". It performed its initial flight on 3 July 1972, with Vladimir Ilyushin at the controls. Performance was enhanced and the variant was approved for production, but the same engine was used on advanced MiG-21 variants, and there didn't end up being enough engines to go around to permit construction of the Su-15bis.

In 1969, the Sukhoi OKB investigated options for a new battlefield close-support "mudfighter" aircraft, one option being a derivative of the Su-15 designated the "T-58Sh" -- where "Sh" stood for "shturmovik (storm bird)", a general Soviet name for a close-support aircraft. The T-58Sh looked like an Su-15 mated to a MiG-27 front fuselage, with broad wings featuring moderate sweep, eight stores pylons, heavy armor, and a built-in Gatling cannon. An all-new design was selected instead, resulting in the Su-25 "Frogfoot" mudfighter.

Sukhoi Su-19M

There were other schemes for derivatives, for example the "Su-19M" of the mid-1970s, which was basically an Su-15TM with improved engines and an "ogival" wing, featuring a leading-edge sweep that smoothly varied from steep at the wingroot, moderate in midwing, and steep at the wingtips. There were three stores pylons under each wing, allowing carriage of six AAMs, and a built-in cannon on the belly. Nobody was buying; the Su-27 was the way of the future, there was no reason to have interest in a warmed-over design with roots going back to the early 1950s.

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[8] COMMENTS, SOURCES, & REVISION HISTORY

* The following table sorts out the somewhat confusing pattern of matchings between NATO codenames and Soviet Su-9/11/15 variant designations:

   ____________________________________________________________________

   Fishpot-A:   T-3 prototype.
   Fishpot-B:   Su-9.
   Fishpot-C:   Su-11.

   Maiden:      Su-9U conversion trainer.

   Flagon-A:    Su-15, early production with pure delta wing.
   Flagon-B:    T-58VD STOL demonstrator.
   Flagon-C:    Su-15UT trainer.
   Flagon-D:    Su-15, late production with cranked wing.
   Flagon-E:    Su-15TM, early production with conical radome.
   Flagon-F:    Su-15TM, late production with curved radome.
   Flagon-G:    Su-15UM trainer.
   ____________________________________________________________________

* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

* Sources include:

* Revision history:

   v1.0.0 / 01 feb 08 
   v1.0.1 / 01 jan 10 / Review & polish.
   v1.0.2 / 01 dec 11 / Review & polish.
   v1.0.3 / 01 nov 13 / Review & polish.
   v1.0.4 / 01 oct 15 / Review & polish.
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