INDEX | SITEMAP | GOOGLE | LINKS | UPDATES | BLOG | EMAIL | DONATE | HOME

The Sukhoi Su-25 "Frogfoot"

v1.1.5 / 01 jun 13 / greg goebel / public domain

* While Soviet Union pursued combat aircraft with ever-greater performance during the Cold War, the USSR also obtained a subsonic dedicated close support aircraft, the Sukhoi "Su-25", known to Soviet forces as the "Grach (Rook)" and to NATO as the "Frogfoot". The Su-25 was produced in quantity, saw combat during the Soviet intervention in Afghanistan and remains in service. This document provides a history and description of the Su-25.

Sukhoi Su-25 Frogfoot


[1] SU-25 ORIGINS
[2] SU-25 DEVELOPMENT
[3] SU-25 DESCRIBED / SU-25 IN AFGHANISTAN
[4] SU-25BM TARGET TUG / SU-25UB & OTHER TRAINERS / SU-25K EXPORT VERSION
[5] SECOND GENERATION SU-25T / SU-25TM
[6] SU-25SM, SU-25UBM, & SU-25KM UPGRADES
[7] VARIANT SUMMARY, SOURCES, & REVISION HISTORY

[1] SU-25 ORIGINS

* The Soviets were pioneers in the design of dedicated battlefield close support aircraft, or "Shturmoviks (Storm Birds)" as they called them. They implemented experimental designs before World War II that led up to the heavily armored and armed Ilyushin "Il-2" and its improved derivative, the "Il-10", which were the backbone of Red Army tactical close air support through the war.

Western nations did not develop such specialized aircraft during World War II, preferring to adapt aircraft designed for the air-combat role, such as the Hurricane, Typhoon, Mustang, and Thunderbolt, into the battlefield fighter-bomber role. Ironically, although the Soviet Shturmoviks of World War II had proven very successful, after the war the USSR adopted a similar policy of modifying air-combat fighters into the fighter-bomber role, pressing such aircraft as the MiG-17 into service as "mudfighters".

The USSR didn't completely abandon the concept of dedicated Shturmovik, however. In 1948, an order came down from the Kremlin for the Ilyushin OKB (Experimental Design Bureau) to develop a jet-powered successor to their Il-2 / Il-10. The result was the "Il-40", a brutish-looking twin-turbojet aircraft that had some resemblances to the earlier Ilyushin Shturmoviks, but incorporated many technologies developed for Ilyushin's Il-28 "Beagle" jet bomber.

The initial Il-40 prototype performed its maiden flight on 7 March 1953. It featured a pilot and a rear gunner in an extended and heavily armored cockpit, and small bombbays in the wings. The aircraft had modestly swept flight surfaces, tricycle landing gear, and was powered by twin turbojet engines mounted in nacelles in the wingroots. It was armed with four 23 millimeter cannon that could pivot downward, and was also fitted with a tail turret, apparently with a single 23 millimeter cannon.

Firing the massed cannons in the nose led to troubles with engine gun gas ingestion, and so a second prototype was built with the engine intakes extended to the nose, giving the aircraft the appearance of having "nostrils". The evaluations went well and the type seemed headed for production, with a reconnaissance / spotter and a trainer version also planned. NATO even assigned the Il-40 a highly appropriate codename, "Brawny".

The Il-40 was then canceled on 18 April 1956, on the direct orders of Premier Nikita Krushchev. Krushchev wanted to focus on long-range missiles to defend the USSR so he could draw down conventional forces and reallocate resources to improving the standard of living for Soviet citizens. One of the prototypes and five additional airframes that were under construction were scrapped, as was the production tooling. The USSR officially forgot about jet Shturmoviks for over a decade.

* The Americans helped revive the Soviet jet Shturmovik. The Vietnam War was a wake-up call to the US military, demonstrating that the flashy futuristic technologies developed in the 1950s didn't always do the job in a dirty war fought in the mud and jungle. One of the lessons learned there was that rugged, relatively slow, heavily-armed attack aircraft, such as the Douglas A-1 Skyraider, were much better suited to mudfighting than supersonic fighter-bomber aircraft.

In March 1967, the US Air Force launched their "Attack Experimental (AX)" competition to build a dedicated American jet Shturmovik, with the effort eventually leading to the Fairchild A-10 Warthog. Soviet military officials followed AX program closely. Warsaw Pact exercises in 1967 also helped revive Soviet interest in a jet Shturmovik. The next year, the Ilyushin OKB pulled the plans for the Il-40 out of the files and modernized the design slightly to come up with the "Il-42". The Sukhoi OKB also got into the act, initiating a jet Shturmovik project in March 1968.

The Sukhoi team was led by the bureau's Oleg Samolovich and worked from a general specification developed by I.V. Savchenko, commandant of the VVS (Voyenno Vozdushniye Sily / Red Air Force) air academy. The Sukhoi aircraft was to be powered by twin Ivchenko-Lotarev AI-25T engines with 17.2 kN (1,750 kgp / 3,870 lbf) thrust each, and would have a maximum speed of up to 800 KPH (500 MPH), with a range of 750 kilometers (465 miles). The aircraft would be able to operate off of rough airfields only 120 meters (390 feet) long and carry 2.5 tonnes (5,500 pounds) of weapons, including an internal heavy cannon. It would be very agile and able to absorb substantial battle damage. The design was given the internal Sukhoi designation of "T8".

The Soviet Ministry of the Aircraft Industry formalized the competition in March 1969 by issuing a request for proposals. The initial request specified only the construction of a few prototypes for evaluation and made no commitment to production. In the meantime, the Soviet Union remained focused on the manufacture of more conventional fighter-bomber aircraft, with the MiG OKB working on ground-attack derivatives of their MiG-23 fighter that would emerge as the MiG-27 "Flogger" series, and the Sukhoi OKB working on a "swing-wing" derivative of their Su-7 strike fighter that would emerge as the Su-17 series.

* In response to the request, the Sukhoi T8 design was polished under the direction of bureau chief Pavel Sukhoi before it was submitted to the ministry, the most significant change being the replacement of the twin Ivchenko-Lotarev AI-25T engines with twin Mikulin RD-9B afterburning turbojets, providing 31.8 kN (3,250 kgp / 7,165 lbf) afterburning thrust each.

Interest among the design bureaus in the jet Shturmovik competition ran high. Along with the Ilyushin and Sukhoi proposals, the Yakovlev and MiG OKBs also submitted designs. The Sukhoi T8 was selected as the winner. Ilyushin officials and engineers proved sore losers. They felt they had the better machine and continued work on their Il-42 quietly, avoiding official attention by hiding it under the designation "Il-102" and describing it as a "research aircraft", which was stretching things a bit. The OKB would work on the type in fits and starts over the next few decades, hiding it away in a dark place when they other things to do or needed to conceal it from the authorities.

Ilyushin Il-102

They would finally display it at the Moscow Airshow in 1992, by which time it seemed to be little more than a museum piece, leading to puzzled speculations as to why the Ilyushin OKB had seen fit to show it off.

BACK_TO_TOP

[2] SU-25 DEVELOPMENT

* Although the Sukhoi OKB expected to get full development of their T8 rolling quickly, an obstacle quickly popped up. VVS generals weren't happy with the design as submitted, insisting that the warload be increased to 4,000 kilograms (8,800 pounds) and that the aircraft be capable of Mach 1 at low altitude. VVS flyboys were simply uncomfortable with the idea of a subsonic jet combat aircraft.

Sukhoi engineers could accommodate the request for more warload by scaling up the design, but supersonic performance was out of the question, though they were able increase its top speed. The redesign effort pushed the beginning of prototype construction to August 1971, with work conducted at State Factory 153 in Novosibirsk, well to the east of the Urals. This facility had long worked with the Sukhoi OKB on other aircraft.

Mikhail Simonov was assigned as project manager. Oleg Samolovich was the chief designer from August 1972 to October 1974, when he was moved to work on the "T10" interceptor, which would emerge as the "Su-27 Flanker". Y.V. Ivashetchkin took Samolovich's place.

While design work on the T8 continued, the design team obtained initial information about the Fairchild A-10. The A-10's engines were mounted in pods above the rear of the fuselage, protecting them to an extent from ground-launched heat-seeking missiles and from anti-aircraft fire. The advantages of this configuration were substantial and some members of the Sukhoi design team lobbied to adopt the same configuration for the T8, but such pod-mounted engines created drag and reduced speed, and it was too late to make such a change without derailing the project anyway.

Pavel Sukhoi died in 1973, having lived long enough to see a mockup of the T8. However, although two prototypes were under construction at the time, a formal order for them wasn't issued by the Ministry of the Aircraft Industry until 6 May 1974, with one to be used for static test. The prototypes were built on a shoestring, leveraging off available gear wherever possible.

The static-test article, numbered "T8-0", was delivered on 12 September 1974. The initial flight-test prototype, "T8-1", was delivered to the Zhukovskiy flight test center in December 1974, though due to an engine failure the first flight was delayed to 22 February 1975. The flight was performed by Sukhoi OKB's chief test pilot, General Vladimir Ilyushin, one of the USSR's most prominent test pilots and by an irony son of Sergei Ilyushin, founder of the rival Ilyushin OKB.

* The T8-1 was fitted with a navigation-attack suite from the Su-17M2 and a GSh-23 twin-barreled "teeter-totter" 23 millimeter cannon. The cannon could be depressed for strafing. By this time, continued changes in service requirements for the T8 had resulted in further increases in weight. The twin RD-9 turbojets were replaced by twin Tumanskiy R-95Sh non-afterburning turbojets with 44.13 kN (4,500 kgp / 9,921 lbf) max takeoff thrust each. The R-95Sh was a non-afterburning version of the Tumanskiy R-13F-300 used on the MiG-21. It was far from a state-of-the-art solution and a more modern bypass turbojet engine would have been preferable in terms of fuel economy, but in compensation that R-95Sh had plenty of power, and was very rugged and reliable as well. It was also not fussy about the grade of fuel it used, and could even burn diesel fuel in a pinch.

The second flying prototype, the "T8-2", performed its first flight on 26 December 1975 with the less powerful RD-9 engines, though it was quickly refitted with R-95Sh engines in March 1976 to become the "T8-2D". The T8-2 was noticeably different from the T8-1 and much closer to what would become production specification. It featured a taller tail and wider-span wings with a leading-edge "dogtooth", and there were less-visible changes as well:

One of most interesting innovations was the T8-2's airbrake scheme, which would become a trademark of the type. The T8-1 had been built without airbrakes; the T8-2 had been originally fitted with conventional airbrakes mounted on the rear of the engine nacelles, but the T8-2 was then fitted with wingtip airbrakes. These were in the form of a pod on each wingtip that included a retractable landing light in the nose, and whose rear section hinged open vertically to act as an airbrake. In principle, these "crocodile" airbrakes were also to be used to assist in turns, but in practice pilots found using them in this way disorienting and of little practical use.

After rollout of the T8-2, the T8-1 sent back to the factory for a two year rebuild effort to bring it up to current specification, emerging in April 1978 as the "T8-1D". The T8-2 was spotted by a US reconnaissance satellite in 1977. Since the Zhukovskiy test center, like almost everything else military in the USSR, was a state secret, the facility was known to the West as "Ramenskoye" after a nearby town, and so the aircraft was given the provisional NATO codename of "Ram-J".

* Although the trials went well the T8 program was very low priority, with the Sukhoi OKB remaining heavily focused on the Su-24 Fencer bomber and the Su-27. In fact, after construction of the first two flight prototypes, the T8 design team was forced to abandon fabrication of the type at Novosibirsk and search for an alternate manufacturing facility.

After considering license production in Poland, as had been done with the Mil Mi-2 helicopter, they finally found a new home at the underused State Factory 31 in Tbilisi, Georgia, where all following prototypes were produced. First flight of a Tbilisi-built T8 was in September 1979. Prototypes numbered up to "T8-15" were built, with some gaps in the numbering sequence.

In the spring of 1980 two of the prototypes performed a 50-day operational trial in Afghanistan, flying a total of 100 combat missions. Ground force commanders directed these strikes and the aircraft proved to be highly effective, with their maneuverability allowing them to get "up close and personal" with the enemy in rugged ravines and valleys. Journalists accompanying the Afghan Mujahedin guerrillas were able to take some pictures of the T8s, and Western intelligence quickly established they were the same aircraft that had been previously logged as the Ram-J. Soon the type was given a permanent NATO codename: "Frogfoot".

* The T-8 test program suffered two setbacks over the next few months. One prototype broke up during maneuvers on 23 June 1980, killing the pilot, and the veteran T8-1D was lost on a dive in January 1980, the pilot ejecting safely. Despite these problems, the type had its advocates, particularly General Alexander Yefinmov, deputy commander of the VVS and a prominent Ilyushin Shturmovik pilot from the Great Patriotic War. The T-8 was finally approved for series production in March 1981. The first production "Su-25" was delivered to the VVS in Azerbaijan in April 1981. Roughly 582 of this initial production variant would be built in all.

BACK_TO_TOP

[3] SU-25 DESCRIBED / SU-25 IN AFGHANISTAN

* There were few changes between the late-build Su-25 prototypes and the production Su-25s, and the early production aircraft were a good baseline for later variants.

Sukhoi Su-25 Frogfoot

The Su-25 was of conventional configuration, with a mid-mounted wing featuring a modest leading-edge sweep and a slight anhedral droop. The engines were mounted in nacelles under the wing roots. The majority of the aircraft was built with standard aircraft aluminum alloys, though there was substantial use of titanium and steel.

The Su-25 had two fuel tanks in the fuselage and a fuel tank in each wing, providing a total internal fuel capacity of 3,660 liters (966 US gallons). The internal fuel tanks were all self-sealing. There was no provision for inflight refueling. While initial production Su-25s used the R-95 turbojet engine, very late production examples used the improved R-195 turbojet, which provided slightly greater thrust and was specifically designed for combat survivability, with the ability to soak up considerable battle damage and keep on running. Fit of the R-195 required minor changes to the engine nacelles.

There were five stores pylons under each wing for a total of ten, though the outermost stores pylon could only be used to carry an air-to-air missile (AAM) for self defense. The innermost two pylons under each wing were "plumbed", allowing the aircraft to carry four external tanks. The usual fit was only two tanks, each with a capacity of 800 liters (211 US gallons) or 1,150 liters (303 US gallons).

The aircraft had dual redundant hydraulic control systems. The wing had full-span leading edge slats, with a double slotted flap on the inner half of the trailing edge of each wing, and an aileron on the outer half. The rudder was split into two segments for reliability, and there were trim tabs on all flight control surfaces. In production aircraft, each wingtip pod not only housed a landing light but a countermeasures system antenna. The crocodile airbrakes built into the pods were improved after initial production by adding a "petal" on top and bottom, giving the airbrakes four surfaces that opened something like a "W", turned on its side so the top faces forward.

The landing gear system featured heavy shock absorbers and low-pressure tires for rough-field operation. Each gear assembly featured a single tire. The steerable nosewheel was offset to the left, and fitted with a mudguard to keep it from tossing debris into the engine intakes.

The canopy hinged open to the right, and the pilot entered using a flip-down ladder built into the forward fuselage. Once inside, he rode low in the cockpit, protected by the titanium bathtub assembly, which consisted of welded plates ranging from 10 to 24 millimeters thick. The bathtub was proof against multiple hits by 20 millimeter or 23 millimeter cannon shells, though unsurprisingly it made for a cramped cockpit.

The canopy was made of armor glass. The pilot sat on a Severin K-36L ejection seat, similar to the ejection seat used in the Su-27. There was a hefty titanium armor plate just above and behind the ejection seat headrest. Field of view from the cockpit was not the best, a necessary tradeoff for pilot protection, and almost nonexistent to the rear, though a periscope was fitted on top of the canopy to provide some rearward vision. The cockpit control layout was old-fashioned, lacking even a head-up display (HUD). Protection was provided for most of the aircraft systems through redundancy or armor.

The Su-25 featured a comprehensive avionics suite. The most noticeable item was the Klen-PS laser rangefinder, which stared out through a glass porthole in the aircraft's chisel nose. Descriptions of the Klen-PS in the Western aviation press tended to the confusing. It apparently had a "laser spot tracker" capability, allowing the pilot to home in on a target marked by a laser. Stories that it had a laser target designation capability seemed arguable, since it wasn't a turreted system as a Western laser target designator would be, and the cockpit lacked a display and hand controller needed for controlling a turret-mounted designator.

Somewhat surprisingly, it was eventually established that the Klen-PS did have a laser target designation capability. The pilot locked the designator onto a target through his gunsight, and the Klen-PS then used inputs from the aircraft's flight control avionics to stay locked on. This shifted the argument to the actual usefulness of such a limited scheme.

Soviet-Russian sources say it proved effective, though its narrow field of view no doubt made it difficult for an Su-25 pilot to take any serious evasive maneuvers while guiding a weapon into a target. Furthermore, though an Su-25 could launch a laser-guided missile and use the Klen-PS to guide it, dropping a laser-guided bomb (LGB) would be more troublesome since a free-fall munition tends to fall behind the launch aircraft. These considerations suggest that Su-25s often used "buddy designation", with one aircraft standing off a safe distance to illuminate a target while another attacked the target. That would have been perfectly practical, since Su-25s usually flew in pairs anyway.

The nose was fitted with distinctive twin pitot probes decorated with navigation antennas, and hinged up for service access. Avionics systems also included:

The aircraft terminated in a spike at the base of the tailfin containing antennas for the RWR and the instrument landing system. Twin brakechutes were stored in a tail compartment beneath the spike, with four chaff-flare dispensers fitted on top of the brakechute compartment. Each dispenser stored 32 chaff or flare cartridges, for a total of 128.

The aircraft carried 250 rounds for its 30 millimeter cannon. Typical external stores included FAB general-purpose bombs; RBK cluster-bomb canisters; and unguided rockets, such as 32-round 57 millimeter rocket pods, 20-round 80 millimeter rocket pods, five-round 122 millimeter rocket pods, or 240 millimeter rockets carried individually. In principle, a heatseeking AAM such as the R-60M (NATO AA-8 Aphid) could be carried on the outer pylon of each wing, and the aircraft was qualified for "smart" weapons such as LGBs or the Kh-29L (NATO AS-14 Kedge) laser guided missile. In practice, the Su-25 has mostly been photographed carrying simple "dumb" munitions.

A set of pods was designed to allow the aircraft to carry its own maintenance support gear to remote airfields. Apparently a pod was designed to allow the Su-25 to carry a maintenance crewman as well. The Americans built a comparable pod for the Lockheed P-38 Lightning fighter in World War II, and taking a ride in the thing was uncomfortable and frightening. It appears the Soviets recognized this and did not actually field their own man-carrying pod.

   SUKHOI SU-25 "FROGFOOT" / LATE BUILD:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                14.36 meters        47 feet 1 inch
   wing area               30.1 sq meters      324 sq_feet
   length with probes      15.53 meters        51 feet
   height                  4.8 meters          15 feet 9 inches

   empty weight            9,185 kilograms     20,250 pounds
   loaded weight           17,530 kilograms    38,645 pounds

   max speed, low level    1,000 KPH           620 MPH / 540 KT
   service ceiling         7,000 meters        23,000 feet
   range with tanks        1,950 kilometers    1,215 MI / 1,055 NMI
   _____________________   _________________   _______________________

* As Su-25s were delivered to VVS units, they were quickly thrown into combat in Afghanistan, operating in earnest there by early 1982. The aircraft was rugged, maneuverable, and could carry a heavy warload. Su-25s often worked in partnership with Mil Mi-24 "Hind" helicopter gunships, providing heavy firepower to deal with targets that were more than the gunships could handle.

The Su-25 became known as the "Grach (Rook)", in reference to a type of European bird that any American who wasn't a hard-core bird watcher would simply call a "crow" without thinking twice about it. Nobody is quite sure how it got the name, though possibly it was because pilots felt that was the way the thing flew in comparison to their sleek "falcon" fighters. In any case, it grew to be a name used with respect, with ground forces deeply appreciating the "Grach" as it wheeled overhead, wings outspread protectively, waiting to be assigned targets to destroy. Su-25s would often be decorated with cartoon rooks.

Attacks were made with dumb bombs and unguided rockets, though "Kedge" guided missiles were used to an extent late in the war. The Su-25 was also sometimes fitted with cannon pods containing a twin-barreled GSh-23 23 millimeter cannon, with 260 rounds per pod and the ability to pivot the cannon 30 degrees down from the aircraft centerline. The pod could be mounted backwards to provide covering fire as the Su-25 left the target area, discouraging the Mujahedin habit of popping up out of hiding and firing on the aircraft from the rear. Reports indicate that the cannon pods were often mounted with one firing forward and another firing backward.

A total of 23 Su-25s was lost in air combat in Afghanistan, with a number destroyed on the ground as well. One of the 23 was shot down by a Pakistani F-16 fighter while pursuing Mujahedin fighters across the Pakistani border.

The Grach could generally shrug off cannon fire and the pilot enjoyed a high degree of protection in his titanium bathtub, but when the Mujahedin began to use US-supplied "Stinger" shoulder-launched surface to air missiles (SAMs), losses mounted. The major problem was that the twin engines of the Su-25 were too close together, and when one failed after a Stinger hit, its disintegration or burning would cause the other to fail as well. The solution was to put a "firewall" between the two engines in the form of a slab of metal about 5 millimeters (0.2 inches) thick and 1.5 meters (5 feet) long. A Freon-based fire extinguisher system was installed as well, and an additional four chaff-flare dispensers were scabbed onto the top of the engine nacelles, giving the aircraft a total capacity of 256 cartridges.

* Although the Su-25 performed with distinction in Afghanistan, it could not really change the equations under which the war was conducted, with the USSR operating against a dedicated and tough enemy fighting in very rugged terrain, and with all the political and tactical disadvantages suffered by an occupying power in a country where it was not welcome. Like the Americans in Vietnam, they were forced to concede defeat and gradually withdrew, finally giving up the war completely in early 1989.

By that time, the USSR was on the threshold of collapse. The Su-25 would serve on in the new world order. After the fall of the Soviet Union, the Russian Air Force would retain about 200 to 220 Su-25s, with Belarus acquiring 99, the Ukraine 80, and small numbers ending up in other former Soviet republics. These numbers also include two-seat Su-25UB trainers, discussed below.

The Su-25 would fight again in the border squabbles and internal conflicts that followed the end of the old Soviet regime. In particular, the Frogfoot would see intense combat in Chechnya, flying thousands of sorties with a loss of about nine aircraft due to combat and flight accidents. The Russian Air Force prizes its Su-25s, since they are rugged, relatively economical to operate, and well-suited to the dirty little wars that are the fashion in the early 21st century.

BACK_TO_TOP

[4] SU-25BM TARGET TUG / SU-25UB & OTHER TRAINERS / SU-25K EXPORT VERSION

* The Su-25 was modified to a target-towing configuration as the "Su-25BM", with 50 reportedly produced. The Su-25BM was almost indistinguishable from the standard Su-25, except for the fact that most or all of the Su-25BMs had the uprated R-195 engines. The cockpit of the Su-25BM was fitted with equipment to control a target-towing winch attached to one of the stores pylons, and the type could also carry parachute or rocket targets. The Su-25BM remained fully combat capable.

* Although the Su-25 was a forgiving aircraft with fine handling, a two-seat operational conversion trainer was built, possibly to train rookies in the demanding art of low-altitude close-support combat. The tandem-seat variant was a low priority, with construction finally passed on to Production Plant Number 99 at Ulan-Ude, in Siberia north of the Mongolian border. The initial prototype, the "T8UB-1", finally performed its initial flight on 10 August 1985, with the variant presently going into service as the "Su-25UB". The type was given the NATO codename "Frogfoot-B", the Su-25 itself becoming the "Frogfoot-A". Roughly 130 to 180 Su-25UBs were built in all.

Development of the Su-25UB had been guided by the principle of making as few changes as possible from the single-seat Su-25, and so the aircraft was not lengthened to accommodate the second cockpit, since that would have required substantial airframe modifications. A fuselage fuel tank was removed to make room for the second cockpit. The rear seat was raised, giving the back-seater a good view forward, and so the forward-looking periscope generally fitted to earlier tandem-seat Soviet trainers was not usually fitted.

Each cockpit had its own canopy, which hinged open to the right. The aircraft's spine was raised, and the height and area of the tailfin was increased to compensate aerodynamically for the Su-25UB's "hump-backed" fuselage. The folding boarding ladder was changed to a telescoping tubular boarding ladder with three steps. The Su-25UB was fully combat-capable.

* Sukhoi was happy enough with the Su-25UB to even consider a variant of the type as a dedicated advanced flight trainer for the VVS as well as "DOSAAF", a paramilitary organization that provided flight training for Soviet youngsters in preparation for formal military flight service.

The T8UB-1 was converted to this configuration by eliminating armor and combat gear, with the modified aircraft performing its first flight on 6 August 1985. The aircraft looked much like the Su-25UB externally, though it was not generally fitted with stores pylons. One distinctive difference was that the dogtooth in the leading edge of the wing was smoothed over, giving the wing a slightly odd "kinked" appearance. This aircraft was eventually known as the "Su-25UT" and then the "Su-28", but it was the only one of its kind built; nobody wanted it. Since it weighed about 2 tonnes (4,400 pounds) less than a combat-equipped Su-25 but retained the same engines, it almost certainly had plenty of pep, but it was simply too large and uneconomical to operate in the advanced flight training role.

Sukhoi did, however, build a small number of similar tandem-seat trainers for the Soviet Navy under the designation "Su-25UTG". These aircraft were designed for practicing carrier landings, and had strengthened fuselages plus a "stinger"-type arresting hook. Initial flight of the prototype was in September 1988, with its first landing on the Soviet carrier TBILISI (later the ADMIRAL KUZNETSOV) in November 1989. Ten production aircraft were built, with five each going to the Russian Republic and the Ukraine after the fall of the USSR. The Russian Navy then requested ten more trainers from Sukhoi, to be converted from standard Su-25UBs and given the designation "Su-25UBP". They were to be similar to the Su-25UTG but would also have a retractable inflight refueling probe. It is unclear if any Su-25UBPs were ever actually delivered.

* Export versions of the Su-25 and Su-25UB, featuring slightly simplified avionics and designated "Su-25K" and "Su-25UBK" respectively, were introduced in the early 1980s. Roughly 180 to 185 Su-25Ks were built, and possibly about 20 Su-25UBKs.

The first delivery of an Su-25K was in 1984, to the Czechoslovak Air Force, which obtained 38 in all, including some two-seaters. Su-25Ks were also sold to Angola (12 aircraft), Bulgaria (40), Iraq (73), and North Korea (36). The Czechoslovak Su-25s were partitioned between the Czech Republic and Slovakia after the "Velvet Divorce" in the 1990s. Both nations got rid of their Su-25s, but the actual disposal of these machines remains unclear; it is known that Slovakia sold ten Su-25s to Armenia in 2005 for the princely sum of a million USD, suggesting they probably weren't in the best condition. The Iraqi Su-25Ks saw "service" of a sort during the 1990:1991 Gulf War, if almost exclusively as "targets", picked off by Coalition airstrikes while sitting on the runway or inside hardened shelters.

Batches of used machines, with a few new-build machines mixed in, were later sold off by former Soviet states to other countries beginning in the mid-1990s. The Congo bought ten; Ethiopia bought four (two single-seaters and two two-seaters, more on this deal later); Eritrea bought up to ten; Macedonia bought four (three single-seaters and one two-seater); and Peru bought 18 (10 single-seaters, 8 two-seaters). Peru actually used their Su-25s for drug interdiction, with their Frogfoots occasionally shooting down drug-running aircraft using cannon fire.

BACK_TO_TOP

[5] SECOND GENERATION SU-25T / SU-25TM

* While the Su-25 provided outstanding service in Afghanistan, it generally operated over short ranges and performed attacks on targets designated by ground or air spotters. However, during the Cold War both sides were focused on fighting a general European conflict, in which case the Su-25 would have to range farther and perform its own targeting. Even before the Su-25 went into combat, the Sukhoi OKB was considering an advanced variant with greater fuel capacity; much more sophisticated combat avionics to handle advanced smart weapons in all-weather, day-night operations; and improved survivability.

Work began on the advanced Su-25 in 1981, with first flight of the initial "T8M-1" prototype on 17 August 1984. Two more prototypes, modified from Su-25UBs, and a static test airframe were built at Tbilisi, to be followed by a batch of eight preproduction machines, leading to first flight of the initial production "Su-25T" on 26 July 1990. Twelve more production machines were built. The "T" stood for "Tankovy", emphasizing the variant's anti-armor role. It was later given the designation "Su-34", but the "Su-25T" designation is used here for simplicity.

The Su-25T was a single-seat aircraft, but it was based on the tandem-seat Su-25UB and had the same "humpbacked" profile. The space occupied by the rear cockpit in the Su-25UB was filled with fuel tanks and avionics, with the rear canopy replaced by a metal fairing. The Su-25T featured additional armor, and internal spaces near the fuel tanks filled with plastic foam to help staunch leaks. The 30 millimeter cannon was fitted underneath the fuselage, instead of in it, to free up internal space for combat avionics. Cannon ammunition load was 200 rounds.

The most significant feature of the Su-25T was the "SUV-25T Voskhod (Sunrise)" weapons control and navigation system, featuring a digital integrated navigation system and the Krasnogorsk "I-25I Shkval (Squall)" targeting system. The navigation system was very sophisticated, with dual redundant navigation computers; an inertial navigation unit; radar altimeter; doppler ground speed reference system; a short-range RSBN radio navigation system receiver; and a long-range RSDN radio navigation system receiver. The navigation system could automatically fly the aircraft to a target area with very little pilot intervention, even activating targeting systems automatically on the threshold of combat.

The Shkval targeting system was fitted in a lengthened nose with a larger nose panel, replacing the Klen-PS system. The Shkval system included a high-resolution TV camera, with a wide-angle (27 by 36 degree) mode for search and a 23-magnification narrow-angle (0.7 by 1.0 degree) mode for targeting; a laser spot tracker; and a "Prichal (Haven)" laser target designator boresighted to the camera. The Shkval optics assembly was steerable through 70 degrees to either side of the aircraft, and from 15 degrees above the centerline to 80 degrees below. The Shkval system incorporated an automatic target tracking system.

The Shkval system was essentially the same as that used on the Kamov Ka-50 "Hokum" helicopter gunship, and allowed the Su-25T to carry and direct advanced laser-guided weapons, such as the "9M120 Vikhr" anti-tank missile, known as the AT-12 Swinger in the West. The Vikhr could also be used against helicopters and subsonic fixed-wing aircraft. The Vikhr was carried in eight-round launcher packs. A hooded TV display and hand controller mounted in the cockpit allowed the pilot to guide the weapons.

The Su-25T also featured an advanced "Irtysh" countermeasures system, including a Gardeniya RF jammer; an SPO-15 Beryoza RHAWS; an SPO-32 "Pastel (Crayon)" radar warning receiver / electronic support measures (RWR/ESM) system, which not only warned of threats but targeted them for attack; and an L-166S1 Sukogruz infrared jammer, mounted in a fairing at the base of the vertical tailplane, to confound heat-seeking missiles. UV-26 chaff-flare dispensers were fitted into a new fairing at the base of the tailfin, providing a total capacity of 192 cartridges.

Finally, the Su-25T could carry a "Mercuri (Mercury)" low-light-level TV camera pod under the fuselage for night and bad-weather combat. The camera had a wide-angle and a narrow-angle mode, with the wide-angle search image displayed in a new cockpit wide-angle HUD and the narrow-angle targeting image displayed in a panel CRT.

* Although an initial production batch of ten Su-25Ts was ordered from the Tbilisi plant and an export "Su-25TK" was promoted, the fall of the Soviet Union intervened and the type never entered full production, though two Su-25Ts did perform combat service in the Chechnya conflict, backing up older Su-25s when a precision strike capability was required. Of the four Su-25s obtained by Ethiopia, two of these were actually Su-25Ts and the other two were Su-25UBs or Su-25UBKs.

The separation of Georgia from the old Soviet empire and the following chaos there stopped Su-25 production at the Tbilisi plant, though the Sukhoi OKB was able to continue some work at the Ulan-Ude plant, under very difficult conditions. Indeed, the organization has continued to refine the Su-25T, resulting in the "Su-25TM Super Frogfoot" (or "Su-39"), with three built to 1998.

The Su-25TM was externally almost identical to the Su-25T, but was compatible with a range of targeting pods, including the "Khinzal (Dagger)" millimeter-wave imaging radar pod; the "Khod (Motion)" imaging infrared pod; and the Phazotron "Kopyo-25 (Spear-25)" multi-mode radar pod. The Kopyo was a sophisticated radar system, originally developed for MiG-21 upgrades; it had navigation, air-to-ground, and maritime warfare modes, as well as air-to-air modes that allowed the Su-25TM to control "beyond visual range" AAMs, though that would be a somewhat peculiar store for a close-support aircraft.

Sukhoi Su-25UB Frogfoot-B, Su-25TM

Along with stores such as dumb bombs and cluster munitions, laser-guided or TV-guided bombs and missiles, cannon pods, and heat-seeking AAMs, the Su-25TM could carry the "AA-12 Adder" BVR missile and the "AS-20 Kayak" antiship missile. The Su-25TM also included a receiver for the Russian GLONASS and comparable US GPS navigation satellite systems. In addition, the Russians developed towed decoy jammers that could be carried by the Su-25TM.

The Russian Navy considered a version of the Su-25TM modified for carrier operation and designated the "Su-25TP". However, neither the Su-25TM nor the Su-25TP entered production.

BACK_TO_TOP

[6] SU-25SM, SU-25UBM, & SU-25KM UPGRADES

* The Su-25 is a durable aircraft, and with fair numbers of them built it is no surprise that programs are underway to keep them up to date. In 1998, the Russian Air Force began a program to upgrade their Su-25s to the improved single-seat "Su-25SM" and twin-seat "Su-25UBM" specifications. This upgrade is intended to keep the current aircraft effective at a reasonably modest cost. It is not intended to bring first generation Su-25s up to Su-25TM standards.

The upgrade involves a service-life extension program (SLEP) to increase airframe life and reduce operational costs, installation of a modernized cockpit, and fit of the "Pantera (Panther)" navigation-attack system, featuring a new digital processor; new digital subsystems; a GLONASS-GPS receiver; and a Kopyo-25SM radar mounted in a pod. Early concepts envisioned a nose-mounted radar, but that proved too expensive. The Klen-PS targeting system and the R-95Sh engines are retained; the engines are old-fashioned, but they are very sturdy and reliable.

Other items proposed for the upgrade include a new "Omul (Salmon)" countermeasures pod to provide jamming and emitter location capabilities; a dual-stores rack; and improved camouflage and measures to reduce the aircraft's radar cross section, though attempting to make a Frogfoot carrying any serious amount of external stores "stealthy" would seem to be a lost cause.

The upgrade will allow the Su-25 to carry the most up-to-date Russian guided weapons and improve the aircraft's survivability. Two Su-25s were rebuilt to the Su-25SM standard and went into flight testing in 2002, with initial deliveries of the first batch of upgrades in late 2006. The Russian Air Force plans to upgrade about 80 machines initially, and hopes to eventually obtain funding to upgrade their entire Su-25 fleet.

* In September 2000, Elbit of Israel and Tbilisi Aerospace Manufacturing (TAM) of Georgia began an effort to fit the Su-25K with modern avionics, including a "glass cockpit" and a modernized "weapons delivery & navigation system (WDNS)". The first updated example of the "Su-25KM Scorpion" performed its initial flight on 18 April 2001 from TAM's Tbilisi airfield, with Georgia's President, Eduard Shevardnadze, observing. The aircraft was flown by TAM's chief test pilot, Yehuda Shafir.

The new avionics system was built around a dual-redundant MIL-STD 1553B databus and the Elbit "Modular Multi-Role Computer (MMRC)". The new cockpit layout included two 15 by 20 centimeter (6 by 8 inch) multifunction color displays (MFCDs), a modern HUD, and "hands on throttle and stick (HOTAS)" controls, providing a much cleaner solution than the patchwork improvisations in the cockpit of the Su-25T and Su-25TM. Two new radios, one UHF and one VHF, were also included.

The WDNS included a GPS-INS navigation system with an Elbit moving-map display, a VOR-ILS landing system, and a stores management system. The existing Su-25 radar altimeter, fuel gauges, and Klen-PS laser rangefinder were retained and integrated into the system. The Scorpion was compatible with a wide range of modern Russian and Western smart munitions.

* At last notice, nobody had bought off on the Scorpion. The only export upgrade program reported to date was a modest upgrade of up to eight Peruvian Su-25UB two-seaters and a handful of Belorussian Su-25UBs to a "Suppression of Enemy Air Defenses (SEAD)" configuration, making it what might be popularly known as a "Wild Weasel". This upgrade included a pod carrying the Pastel RWR/ESM system, a rear-cockpit display to provide emitter data and targeting, and compatibility with the "KH-58 (AS-11 Kilter)" anti-radar missile. A few Czech Su-25s were modified for NATO interoperability, but the Czech Republic then decided to phase out their Su-25s and nothing more was done.

BACK_TO_TOP

[7] VARIANT SUMMARY, SOURCES, & REVISION HISTORY

* Su-25 single-seat variants include:

Su-25 two-seat variants include:


Sukhoi Su-25 Frogfoot

* Sources include:

* Revision history:

   v1.0   / 01 oct 01 
   v1.1.0 / 01 oct 03 / Review & polish.
   v1.1.1 / 01 oct 05 / Review & polish.
   v1.1.2 / 01 sep 07 / Review & polish.
   v1.1.3 / 01 aug 09 / Review & polish.
   v1.1.4 / 01 jul 11 / Review & polish.
   v1.1.5 / 01 jun 13 / Review & polish.
BACK_TO_TOP
INDEX | SITEMAP | GOOGLE | LINKS | UPDATES | BLOG | EMAIL | DONATE | HOME