Sukhoi’sFrogfoot” Su-25, Su-28, Su-39

 

 

The Su-25 has often been assumed to be a Soviet clone of the USAF's AX COIN aircraft, based on the losing Northrop A-9 (rather than the winning A-10), and less agile and less armoured more as a result of Soviet incompetence than by deliberate design. The USAF's Vietnam War-inspired AX requirement was for the close air support of troops in contact and for counterinsurgency, which assumed a degree of air superiority or at least a low level of air and SAM threats. By contrast, the Russian aircraft was designed to meet a slightly later and very different requirement which stressed anti-armour and fighter-bomber capabilities over the modern battlefield. Combat proven in Afghan skies, the Su-25 is considerably more versatile than were its American counterparts, and is a remarkably efficient and cost-effective fighter-bomber.

Its export success has been limited by its lack of air-to-air fighter capability and by its lack of supersonic performance, since prejudice against the very idea of a subsonic combat aircraft remains strong. This can be gauged by the fact that even in the former USSR the aircraft was never procured in large numbers, while arguably less effective fighterbombers (like the early Su-17s and MiG-27s) poured off the production lines in huge numbers. Overseas, sales of the Su-25 were further diminished by the ready availability of cheaper alternatives, many of which are retired and reroled fighters. Those customers willing to overlook the aircraft's lack of speed have found it to be a remarkably potent weapon - perhaps unsuitable for independence day parades, but remarkably useful in its intended role once the bullets start flying. Combat experience pointed the way towards some obvious improvements and refinements, many of which were incorporated during production; more major changes resulted in an extensive redesign to produce a second-generation 'Frogfoot'. This aircraft emerged as the Cold War was ending, and it has proved almost impossible to win orders for the new variant either at home or overseas.

 

Shturntovik origins

During the Great Patriotic War (the approved Soviet term for the struggle against German invaders, which began in 1941) Russia pursued the design, manufacture and tactical use of dedicated ground attack and close support aircraft known generically as Shturmoviks, following the German lead set with aircraft like the Henschel Hs 123 and Hs 129. Britain and America preferred to use aircraft retired or switched from fighter or bomber duties (like the countless  Spitfires, Hurricanes and Thunderbolts), or aircraft which had proved unsuitable for their design role (like the Hawker Typhoon). This Western approach set the pattern for the post-war world, with redundant or second-best jet fighters being hastily armed with bombs and rockets and pressed into service in the ground attack role.

Having successfully built up a family of dedicated ground attack and close support aircraft during the war, the USSR threw away its lead and followed Western practice afterwards. Successive generations of MiG-15s, MiG-17s and MiG-19s were pressed into service as fighter-bombers as soon as they were replaced in the fighter and interceptor roles.

The Ilyushin Design Bureau, previously responsible for the 11-2 and 11-10, attempted to produce a jet-powered Shturmovik in the shape of its 11-40, responding to a 1948 order. The aircraft was a jet Shturmovik, powered by twin AM-9 engines. It had a rear gunner and internal bomb bays in the wings, although it also drew heavily on the OKB's 11-28 twin-jet bomber. The 11-40 featured a quadruple package of NR-23 23-mm cannon, which could be traversed from the horizontal almost down to the vertical. It was also planned to use the new 'Groza' missile system. The prototype made its maiden flight on 7 March 1953 and the type was recommended for production in March 1954, although it had problems with gun gas ingestion. A modified second prototype flew in October 1955 and passed its state acceptance tests in March 1956. This had extended air intakes stretching forward to the nose, which were inevitably nicknamed 'nostrils'. Three sub-variants were planned: the basic cannon-armed Ilyushin I1-40P, the I1-40R (I1-40ARK) reconnaissance and fire correction platform, and the I1-40UT trainer. The project was cancelled soon afterwards on 18 April 1956, apparently at the personal orders of Nikita Krushchev, who felt that it was an unnecessary diversion from the serious business of missile procurement. Records relating to the decision have reportedly disappeared from the official archives (see World Air Power Journal Volume 17 for more information on the 11-40 and Ilyushin's revived 11-102 design).

Five completed airframes at Rostov were destroyed, as well as one of the prototypes and the production tooling. This effectively killed off the concept of a jet Shturmovik until well into the 1960s, when USAF experience in Vietnam seemed to point out the weaknesses and inadequacies of the converted jet fighters used in the ground attack role, and the usefulness of ageing and slow propeller-driven strike aircraft like the Douglas Skyraider.

 

Revival of the concept

The USAF launched its own AX requirement with a request for proposals on 6 March  1967. This step, and those leading to it, were studied with great interest in the USSR. Existing fighter-bombers were studied with particular interest during the Warsaw Pact's major Dniepr '67 exercise: to everyone's surprise, the elderly'MiG-17s and MiG-15s proved more effective than the faster but less agile MiG-21s and Su-7s. During the Six Day War, the devastating effectiveness of 30-mm cannon-equipped Israeli fighters (including obsolete Ouregans and Mysteres) against ground targets (including tanks) provided further food for thought, and prompted Colonel General M. N. Mishuk to call for immediate production of the ancient 11-40. General I. P. Pavlovskii, commander of the Red Army, strongly supported those of his officers who argued for a new ground attack aircraft, and momentum began to build. Deputy commander of the VVS, General Alexander Yefimov, was another powerful supporter, seeing a need for an aircraft like the Il-2s which he had flown during the Great Patriotic War.

While the Ministries of Defence and of the Aviation Industry considered the evidence and requests which were steadily accumulating, Sukhoi took matters into its own hands and in March 1968 began the design of a jet-engined Shturmovik. Ilyushin dusted off its drawings of the old 11-40 and revised it to become the 11-42.

Sukhoi's Shturmovik was designed by a loose group of senior personnel, including Oleg Samolovich, D. N. Gorbachev, Y. V. Ivashetchkin, V. M. Lebedyev and A. Monachev, who based the design on a configuration produced by I. V. Savchenko, commander of the air force air academy. It was known as the SPB project. The aircraft was designed around a pair of 17.2-kN (3,865-lb st) Ivchenko/Lotarev AI-25T engines. It was estimated that these would give the aircraft (which had an MTOW of 8000 kg/17,635 lb) a maximum speed of between 920 and 1,475 kt (500 and 800 km/h; 310 and 500 mph) and a range of 1,390 nm (750 km; 465 miles) with its 2500-kg (5,510-lb) warload, which included an internal cannon. Sukhoi stressed 'closer, lower and quieter' as its key words, rather than the contemporary VVS slogan of 'higher, faster, ‘further'. Programme goals were to design an aircraft with very high battle damage resistance and tolerance, which would be economic and simple to produce, operate and maintain, which would have unmatched performance and agility at very low level, and which could operate fully laden from a semi-prepared 120-m (390-ft) airstrip. Officialdom caught up with the two bureaux in March 1969, when an official LSSh 'Shturmovik' request for proposals was issued by the Ministry of the Aircraft Industry.

The launch of the competition did not represent a complete change of heart, however, since development of the swing-wing Su-17 and ground attack variants of the new MiG-23 continued apace. There was no guarantee that any design produced as a result of the competition would ever enter production, and if an aircraft type were to be manufactured it seemed likely that it would be in only small numbers, for further evaluation of the concept.

 

The jet Shturmovik competitors

Nevertheless, the new requirement was important enough for four experimental design bureaux to work on competing designs. Sukhoi continued with its T8, while llyushin continued with the 11-42. Yakovlev designed a version of its Yak-28 'Brewer' bomber as the Yak-25LSh, and Mikoyan worked on a pair of designs under the provisional designation MiG-27, although neither bore any resemblance to the MiG-27 we know today. The MiG-27Sh was based on the MiG-21 airframe, but with side-mounted intakes and a broad-chord, modestly swept wing like that fitted to the Hawker Hunter and a heavily framed canopy incorporating great slabs of armoured glass. The cockpit was moved forward. The MiG-2711 was more revolutionary, a supersonic Shturmovik with a similar armoured cockpit and canopy and with similar fuselage and intakes, but with the ogival delta wing of the A-144 Analog. The aircraft was powered by a pair of unspecified engines installed side-by side in the rear fuselage, and was intended to carry a warload of up to 3000 kg (6,610 lb). A rewinged MiG-21LSh design was considered, but most of the attention was focused on the MiG-27 derivatives.

The Sukhoi T8 was redesigned under the guidance of bureau chief P. O. Sukhoi before it was formally submitted in response to the LSSh requirement. The most important of the changes suggested by Sukhoi was the addition of a pair of 29.5-kN (6,630-lb) (or 27 kN/6,070 lb, according to some sources) Mikulin RD-9B engines, non-afterburning versions of the MiG-19's turbojet powcrplant.

 

Sukhoi takes the day

These changes were enough to allow the Ministry of the Aviation Industry to select the Sukhoi design as the winner of the competition, much to the annoyance of the llyushin OKB, which felt that their aircraft was superior and that their history and experience made them the natural choice to design a jet Shturmovik. They suspected that their aircraft had been rejected for the wrong reasons, conjecturing that the motive for selecting the T8 could be found in its single-seat configuration, which did not require the training of a new generation of dedicated gunners. To Ilyushin this was an expensive heresy, for they believed that operational experience had shown that a rear gunner was absolutely essential in a slow-moving Shturmovik. They were also amazed that their turbofan-engined aircraft (powered by a pair of non-afterburning derivatives of the MiG-29's RD-33) had been beaten by an aircraft powered by thirsty and oldfashioned turbojets, which necessitated the carriage of a larger explosive and inflammable fuel load, and which the OKB also believed were more prone to battle damage.

The Ilyushin Design Bureau was now officially out of the picture, but it continued work on its aircraft privately, describing it as an aerodynamic research aircraft and later moving the prototype to a Byelorussian airfield to avoid attention. Much later, following criticism of the Su-25 after its initial combat experience in Afghanistan, the Ilyushin aircraft re-entered the 'Frogfoot' story, as will be described.

With the T8 declared as the winner of the design competition, approval was given for further development. Prototype drawings, and production tools and jigs were prepared at Factory No. 153 at Novosibirsk, a plant traditionally associated with Sukhoi aircraft. Production of the first prototype was scheduled to begin in June 1970, but was delayed until August 1971 when air force officers increased the required warload to 4000 kg (6,435 lb), and tried to force an increase in low-level maximum speed to 1200 km/h (745 mph). Sukhoi argued strongly that supersonic speed was unnecessary and would impose unacceptable penalties, but some air force officers, conditioned by their experience with Su-7s and MiG-21s, simply could not conceive that any aircraft could survive without supersonic capability. Sukhoi compromised on Mach 0.82 (having originally favoured Mach 0.7). The aircraft was redesigned to meet the amended requirement (becoming the LVSSh) with larger fuel tanks, bigger overall dimensions and a revised MTOW of 10530 kg (6,540 lb).

 

The T8 team

Mikhail Simonov was appointed as project manager, with Oleg Samolovich remaining as chief designer on the aircraft from August 1972 until 9 October 1974, when he moved to the T10 (Su-27) and Y. V. Ivashetchkin took over. This was one month before the redesign was complete, in September 1972. Ivashetchkin had been Samolovich's deputy from 25 December 1972. Under Ivashetchkin was Vladimir Babak, who supervised a design team consisting of Yuri Rybishkin (detail airframe design), Alexander Blinov (durability), Pietr Lyrshchikov (combat survivability) and Alexei Ryzhov (engine integration). The production supervisor was Valerii Nikolskii, and the chief of testing was Colonel Stanislav Nazarenko.

At around this time, the Sukhoi designers got their first glimpse of the US Fairchild A-10, and this caused something of a crisis. Several members of the team were keen to follow the US example of mounting the engines in pods above the fuselage, but this was felt to impose an unacceptable drag penalty; anyway, it was already too late for such a fundamental change.

The T8 mock-up was presented to the authorities at Khodinka, near Moscow, but an official order for prototypes was not placed. Two prototypes (T8-1 and T8-2) were in fact already under construction, Sukhoi having authorised the start of work after approving the preliminary design on 6 June 1972. The reason that the prototypes were not officially ordered became clear at a meeting between the OKB and the Minister of the Aviation Industry, P. V. Dementiev, when the aircraft's MTOW was again revised upwards, to 12220 kg (5,540 lb), and warload was increased to 5000 kg (3,110 lb) (although this was later relaxed back to 4000 kg/2,485 lb). A maximum g limit of 6.5 was specified, and the important systems were to be protected against damage by shells of up to 20-mm calibre.

P. O. Sukhoi lived long enough to see the mock-up of the aircraft for which he had fought, but died in 1973 before the prototypes were formally commissioned. The order to complete two T8 prototypes (one, T8-0, to be a static test airframe) was finally issued on 6 May 1974. This order was a tactical-technical requirement, which funded prototype aircraft and a limited flight test programme, but held out no promise of production funding. Sukhoi realized that the aircraft would have to be produced on a shoestring budget, and that existing equipment, avionics and systems would have to be used wherever practical.

The T8-0 was delivered for static testing on 12 September 1974. The T8-1 prototype was completed with a modified version of the nav/attack suite fitted to the Su-17M2 'Fitter' and had a modified version of the SPPU-22 cannon pod mounted internally as the VPU-22 gun station. This contained a GSh-23 twin-barrelled 23-mm cannon with barrels which could be depressed for strafing. It was almost certainly only ever intended as an interim gun for the Su-25, whose concept had stressed the advantages of heavier calibre 30-mm weapons. The aircraft's avionics included the FON-1400 laser rangefmder, DISS-7 Doppler, and KN-23 navigation computer (designed for the MiG-23B series fighter-bombers). The flying prototype was delivered to the LII Gromov Flight Research Centre's Zhukhovskii airfield for testing in early December 1974. The Sukhoi bureau's chief test pilot, General Vladimir Ilyushin, was nominated as the initial project pilot and made the first high-speed taxi runs on 25 December 1975. The first taxi runs with the nosewheel raised off the runway took place on 3 January 1975. On 11 January, two days before the scheduled date for the maiden flight, one of the RD-9 engines (which had actually been scavenged from a redundant MiG-19, according to legend) suffered a turbine bearing failure, and several blades separated, causing major damage. The first flight was finally made on 22 February 1975.

 

Engine shortfalls

These problems with the RD-9 engine represented a particularly bitter pill for Sukhoi to swallow, since it had already been decided that a more powerful engine would be needed to cope with the aircraft's planned increased weight, and since the Minister for Aircraft Production, P. V. Dementiev, had already refused to authorise production of the Su-25 with the 'obsolete' RD-9. This was found in the shape of the Tumanskii R-95Sh, which was essentially the MiG-21's R-13F-300 with its afterburner removed. The new engine was again based on an afterburning turbojet, and not on a more modern, more suitable, and more economical turbofan. For the rest of its life, the Su-25 was handicapped by its primitive powerplant, and from time to time proposals were made that the aircraft should be re-engined with RD-33s (without afterburners). The answer was always the same: the necessary structural changes were too extensive to make re-engining worthwhile.

Although it was undeniably primitive, the R-95Sh was extremely robust and reliable. The powerplant was a twinspool turbojet, with an axial compressor, a three-stage low pressure section and a five-stage high-pressure section. The axial turbine was of two stages. The engine also had a 10-chamber annular combustor, with twin igniters. Auxiliary gearboxes were mounted on the bottom of each engine, driving the DC starter and generator, the AC generator, and the hydraulic, fuel and oil pumps. The R-95Sh was also designed to be able to run using different fuels, although this was only possible for four hours when using non-standard fuels such as vehicle diesel fuel. While the new engine was being developed, the aircraft continued to fly, and continued to experience difficulties. The aileron control system proved to have inadequate power, and eventually (from about 1984) BU-45 hydraulic boosters had to be fitted.

Despite the problems, the aircraft was transferred to Akhtubinsk in June 1975, where it undertook a variety of live weapons firing trials. These were concluded in August, military pilots noting that the aircraft's control forces were unacceptably high (even by Soviet standards, where higher stick forces are accepted as the norm), and that the cockpit was inadequately ventilated. The RD-9 engine had also proved prone to stalling when the cannon or rockets were fired, and was considered to be deficient in thrust.

In its original configuration, the first T8 looked quite different to all subsequent Su-25s. It had a shorter fin, with a small, single-piece rudder, and the wing was of shorter span and lacked the later Su-25's distinctive wingtip airbrake pods. The wings may have been slightly more swept, but this cannot be confirmed. The VPU-22 gun station took the form of a streamlined constant-section tube semi-submerged into the lower forward fuselage, with a fore-and-aft aperture in the front for the depressing gun barrels. The nosewheel was mounted 210 mm (8.3 in) to the left of the centreline.

 

The 'all new' T8D

The problems suffered by the first T8 prompted the eventual decision to entirely rebuild the aircraft with a host of modifications and improvements, completely changing its appearance and capabilities. It was rolled out after a twoyear lay-up on 26 April 1978, just in time to take part in the state acceptance trials which began on 21 July 1978, for which the aircraft flew under the revised designation T8D (D for Dvigyatel, or engine). The second prototype had already joined the flight test programme, making its maiden flight on 26 December 1975. This aircraft was the first with a production-representative titanium cockpit bathtub, the first aircraft having had steel armour of the same weight. The T8-2 was also the first prototype which actually looked like a real Su-25, with long-span wings and a tall tailfin. The long-span wings included longer span (and thus increased area) ailerons, servotabs and a leading-edge dogtooth discontinuity. The aircraft was re-engined with R95Sh engines to become the T8-2D in March 1976 (before the first prototype was re-engined). The new engines had a new thrust line, and the tailplanes were modified in consequence, going from 5° anhedral to 5° dihedral. This was achieved by simply swapping the tailplanes from one side to the other and turning them upside down.

When it emerged from its rebuild, the T8D closely resembled the second aircraft in appearance, with a dihedral tailplane, taller fin, long-span wings and ailerons, and wingtip pods. The wingtip pods first fitted to the T8-2 contained a retractable landing light forward, and had a horizontally split rear section, with upper and lower halves which split apart to act as airbrakes. It was originally intended that the split airbrakes could be operated together to act as speedbrakes, or individually (in conjunction with appropriate rudder input) to generate side force. This capability was found not to be tactically significant, and the physiological effects on pilots were unpleasant. The T8-1 was originally built without airbrakes at all, and before it gained its wingtip pods the T8-2 had petal-type airbrakes mounted on the back of the engine nacelle sides.

 

Ram-J' is revealed

The original VPU-22 gun station had been removed and replaced by an AO-17 30-mm twin-barrelled cannon mounted in the lower port forward fuselage. This necessitated moving the nosewheel again, to a position to the right of the aircraft's centreline. The change of cannon finally fulfilled Soviet air staff demands for a larger calibre gun packing a heavier punch. The T8 was eventually 'spotted' at Zhukhovskii by a Western intelligence satellite during 1977, and the aircraft was allocated the provisional Ramenskoye-series (the nearest town to the then anonymous test and trials airfield) reporting name 'Ram-J'.

 

Avionics improvements

Underneath the skin, even more important changes had been made. The navigation and attack suite of the Su-17M-2 was replaced by the upgraded and enhanced avionics of the Su-17M-3. The Fone laser rangefmder was replaced by a Klen-PS laser ranging unit, while the aircraft also received a KN-23 navigation computer, a DISS-7 Doppler, an RV-5M radar altimeter and an ASP-17BC-8 gunsight. This equipment suite was fitted to the T8-3 and subsequent pre-production aircraft from the start. The net effect of the many equipment changes was to enhance the accuracy of both navigation and weapon aiming. The KN-23 navigation computer, the DISS-7 Doppler, and the ASP-17BC-8 gunsight were retained in the production avionics suite.

So little priority was accorded to the T8 that production of the aircraft had to be moved from Novosibirsk after the construction of only the first two prototypes to make way for more important work on the Su-24 'Fencer' and Su-27 'Flanker'. Even the factories at Smolensk and Irkutsk were busy with Su-24 and Su-27 work, and Sukhoi was forced to look elsewhere. Licence-production in Poland was seriously considered, before the OKB eventually took the project to the under-utilised Factory No. 31 at Tbilisi in Georgia. The T8-3 and T8-4 were built at Tbilisi to the revised configuration, making their maiden flights on 18 June 1979 and during September 1979, respectively.

 

T8 trials in Afghanistan

The Su-25 has been associated with the Soviet intervention in Afghanistan since the start of its career. From 16 April until 5 June 1980 (50 days), the first and third T8 prototypes were sent to Afghanistan to participate in a portion of the state acceptance trials which were to be 'conducted under as near real battlefield conditions as possible'. These trials, undertaken under the codename Romb-1, were not operational trials, although the pilots were warned that they might be asked to undertake missions by local divisional commanders. The two aircraft operated from a semiprepared strip at an Afghan tank base near Shindand. They made 100 combat sorties in Afghanistan, 30 of which counted towards the state acceptance trials. They flew real missions, tasked by ground force commanders, who quickly found the agile T8s especially well-suited for attacking inaccessible targets in ravines and steep valleys. A pair of AV-MF Yak-38s participated in Romb-1 in Afghanistan at much the same time. The Su-25s were seen and photographed by Western journalists accompanying Mujahideen guerrillas, and though taken from very long range the photos were distinct enough to allow Western intelligence officers to see that the aircraft they knew as 'Ram-J' was flying operations. The full ASCC reporting name 'Frogfoot' was allocated soon afterwards.

The fourth Su-25 prototype (T8-4) was left to complete state acceptance tests at Mary in Turkmenistan until March 1981, when production was finally recommended. One of the loudest voices arguing in favour of this step was that of General Alexander Yefimov, deputy commander of the VVS and himself a distinguished former Shturmovik pilot during the Great Patriotic War. While this marked a successful step in the T8's career, the step forward was accompanied by two steps back. The test fleet was already depleted by the planned use of the T8-3 for battle damage resistance tests, in which weapons of increasing calibre and velocity were fired at the airframe, but was due to be further reduced. The fifth T8 prototype (T8-5, which had joined the test programme during early 1980) had already been destroyed on 23 June 1980. It disintegrated at only 7.5 g, killing the test pilot, Y. A. Yegerov, and in January 1981 the Afghan veteran T8-1 disintegrated in a dive from which A. Ivanov ejected safely.

 

T8 trials developments

Additional T8 airframes soon joined the flight test programme. The T8-6 was used for gun-firing trials, while the T8-9 was used for aerodynamic and spinning trials. Rough field and external warload trials were undertaken by T8-10, including trials of backward-firing rocket projectiles from a heavily modified B8M pod (which still appeared to face forward). The T8-11 was the first aircraft with boosted ailerons. It later tested the new W-section four-part airbrakes. The next prototype finished its test-flying life trialling a special radar-absorbent ('stealthy') skin, and reportedly undertook compatibility trials with at least one type of tactical nuclear weapon. This laid the groundwork for the Su-25's later secondary (and little known) nuclear role. Su-25s have been associated with the IAB-500 'shape' that is believed to be the training weapon associated with the RN-61 nuclear bomb carried by various Frontal Aviation fighter-bomber types. With its 'stealthy' coating, the T8-12 had its laser window and gun port covered over, and at the end of these trials was retired to the museum at Khodinka. This was an accidental breach of the security surrounding the new coating (which may have been under test for a more advanced aircraft type, possibly the MiG 1-42) and, when it was noticed, the aircraft was quickly withdrawn and replaced by a less sensitive Su-25. The aircraft is now believed to be in the Central Museum of the Great Patriotic War in Bralev Fonchenkou in Moscow.

The T10-14 and T10-15 were eventually used as R-195 engine testbeds, after extensive service as development mules. The T10-15's career included combat service in Afghanistan. The T8-7, T8-8 and T8-13 designations were not used by flying prototypes, and may have been static test and battle damage airframes, or may have become the Su-25UB and Su-25T prototypes.

 

Su-25 into production and for export

The first production Su-25s rolled off the line at Tbilisi and were delivered to the 200th OShAE at Sital Chai in Azerbaijan during April 1981. Universal export success was destined to elude the Su-25 - only two of Russia's Warsaw Pact allies ever bought the aircraft — but the type was exported (albeit in modest numbers) from quite an early stage in its career. The export version of the little fighterbomber was designated as the Su-25K, and was externally identical to the version delivered to Frontal Aviation Shturmovik regiments. The first Su-25Ks were delivered to Czechoslovakia in April 1984, and the first good quality photos of the Su-25 started to appear in Czech aviation magazines the following year. The deliveries to Czechoslovakia took place early in the Su-25's career, even before the type had reached the Group of Soviet Forces in Germany, and while only one of the 60th OShAP's squadrons was available for combat in Afghanistan. The Su-25Ks delivered to Czechoslovakia and Bulgaria differed little from the aircraft used by Soviet regiments during the same period, although they almost certainly had slightly downgraded defensive avionics equipment and were not compatible with nuclear weapons. Identically designated Su-25Ks delivered to other customers (e.g., North Korea and Iraq) were probably even more downgraded, although they displayed few external differences to the Soviet Su-25s.

 

Shopping for an Su-25

The costs of military aircraft are seldom revealed. Even when one is, it is hardly clear what level of spares support, ammunition, and ground support equipment has been included. Furthermore, prices actually differ according to political circumstances, the customer's 'status' (in relation to the supplier), and the extent to which the deal is being financed by the home government (as aid, as a genuine commercial deal, or in exchange for some commodity). Today, Russian aircraft manufacturers often find themselves supplying their aircraft as part of debt repayment packages. Prices can also differ according to whether the deal involves offsets, or according to the currency in which the customer will be paying. Finally, the exact specification of the aircraft being delivered will have an impact on price, as will the inclusion of any training within the USSR.

For all of these reasons, it is unusual for the price of a military aircraft to be openly released. The price offered to a long-standing customer or a close ally, paying with gold (or $US) and not demanding complex offsets, will be very different to the price offered to a customer paying in palm oil and unlikely to make even those payments on time or in full. Surprisingly, quite detailed prices for the Su-25K emerged during the early 1990s. They gave an indication of the amount of equipment and weaponry supplied in a standard package (to equip a single squadron).

Twelve Su-25Ks, with a set of tools, spares and ground maintenance aids, were quoted at $132 million ($11 million each), plus two Su-25UBKs cost an additional $23.8 million ($11.9 million each) with the same tools, spares and equipment. Each aircraft was supplied with two SPPU-22-01 gun pods, eight BD-3-25 pylons, two PD-62-8 pylons, two APU-68-85E launchers, two APU-60-1MD launchers and three empty B8M rocket pods, while two BD-3-25AKU pylons and their associate two AKU-58E launchers were supplied with each group of four aircraft. These allowed the aircraft to carry the Kh-58 (AS-11 'Kilter') anti-radiation missile. A conversion training course was costed at $1.596 million, and a KTS-18 simulator at $5.35 million. Four spare R-195 engines were priced at $4.72 million ($1.18 million each).

Weapons which could be supplied included 3,360 S-8KM unguided rockets (at $1,607 each), 840 S-13T rockets (at $5,110 each) and 840 S-13OF rockets (at $4,450 each). The larger S-24B (retailing at $5,210 apiece) were supplied in batches of 336, and 84 S-25-OFM-PUs were offered at $14,167 each.

For the built-in 30-mm cannon, 5,000 rounds of OFZ shells were offered at $26,364 per thousand, while similar OFZ shells for underwing 23-mm cannon retailed at 7,460 per thousand and were supplied in batches of 30,000. The 23-mm BZT round (supplied in the same quantity) cost $5,653 per thousand.

Missiles available included the Kh-25ML (168 of which constituted a standard batch, at $103,643 each) and the Kh-29L 84 for $175,241 each). Inert captive acquisition training rounds for both missiles were available in pairs, at $77,734 and $131,433 each, respectively.

Most types of bomb were supplied in quantities of 336, and unit prices included $1,445 for a FAB-250-270 fire bomb, $1,956 for a FAB-250M62, $8,705 for a BETAB-500, 10,195 for a FAB-500SHL, $12,054 for an ODAB-500PM, 13,728 for an RBK-500 AO-2 cluster bomb and $20,538 for a BETAB-500SHP. The RBK-500 PTAB-1 was the most expensive bomb offered, at $21,021 each. Smaller bombs were generally delivered in bigger batches, with the bargain basement $859 OFAB-100-120 coming in batches of 1,344 bombs. A handful of specialist stores were supplied in smaller quantities. A batch of 20 FOTAB-250T photoflashes retailed at $5,060 each, while 100 SAB-250-200 illuminators cost $4,821 each.

 

Technical description

The Su-25K's service life was given as 1,500 flying hours before a major overhaul, and the service interval as 700 hours. They obviously did not expect high utilisation, since the 700-hour interval was also given as a seven- to eight year gap. The first production Su-25 hardly differed from the later prototypes, and a technical description of one would apply just as well to the other. In fact, all Su-25s up until the Su-25T/TM were structurally similar, with much the same systems. Only a handful of changes were made as result of later combat experience in Afghanistan, and they were limited in scope, despite their impact and significance.

The Su-25 was of conventional configuration and construction, apart from the extensive use of armour plate. The aircraft was an all-metal monoplane with a high-set, high aspect-ratio wing which was modestly tapered and slightly swept on the leading edge, but not on the trailing edge. The wing incorporated 2°30' of anhedral. Engines were mounted to the fuselage sides in semi-conformal nacelles. Sixty per cent of the aircraft's structure was of conventional Duralumin construction, with 13.5 per cent titanium alloys, 19 per cent steel, 2 per cent magnesium alloys and 5.5 per cent fibre-glass and other materials. Virtually no use was made of carbon-fibre composites or advanced aluminium lithium alloys.

Electrical power was supplied by a single 28.5-volt DC circuit, and by three 36-volt/400-Hz and one 115-volt/400-Hz AC circuits. The DC circuit consisted of a transformer, voltage regulator, and circuit breakers. Power was generated by a pair of engine-driven GSR-ST-12/400 generators, with two 25 Aph NiCad batteries available as an emergency power source.

 

Fuel system

The Su-25's fuel system delivers fuel to the engines from four pressurised main tanks, and from any external tanks (up to four of which can be carried underwing). The system incorporated DCN-44S-DT supply pumps, ECN-91B centrifugal delivery pumps and SN-6 ejector pumps, together with an NR.-54 regulator, filters, cleaners, and dump valves, and with flow-meters, pressure and contents sensors. The internal tanks are pressurised using bleed air from the compressor's eighth stage. The No. 1 and No. 2 tanks are located in the fuselage, with the No. 2 (rear) tank sub-divided into two and acting as a collector tank. The fuselage tanks contained a total of 2386 litres (525 Imp gal) and had armoured bottoms and sides, beside being self-sealing and lined with reticulated foam. The wing tanks contained a total of 1274 litres (280 Imp gal). The tanks could be filled manually, through gravity filler caps, or using a single pressure-refuelling point in the No. 1 tank. The engines can run using five types of aviation kerosene (PL-4, PL-6, T-l, TS-1 and RT) or in emergency can run for a limited time on diesel.

The Su-25 has independent twin hydraulic systems, each powered by an engine-driven NP-34-1M supply pump andeach using 18 litres (4 Imp gal) of AMG-10 hydraulic fluid, pressurised to between 20 and 23 MPa using nitrogen. The port engine drove the system designated as the primary hydraulic system (PGS), which powered the nosewheel steering unit, the initial chambers of the aileron boosters, the airbrakes, the slats, the flaps and the tailplane, and could be used for emergency undercarriage extension. The starboard engine drove the secondary (VGS) system, which was used for undercarriage extension and retraction, mainwheel braking, and the yaw damper, and for the second chambers of the aileron boosters.

The semi-monocoque fuselage consisted of four sections (nose, forward fuselage, centre section and rear fuselage) and was built up around 35 bulkheads, longerons, auxiliary bulkheads, stringers and a stressed skin. The foremost nose section extended from the first to the fourth bulkhead, to which were attached the twin air data booms with their pitot-static sensors. The nose incorporated a downward-opening forward fairing, whose chiselled front edge included the Klen PS laser rangefmder window, and which swung down to give access to the Klen equipment. The unpressurised navigation and auxiliary avionics bay behind this incorporated four upward-opening access doors.

The nosewheel bay contained the rearward-retracting nose oleo, which incorporated a twin-chamber hydropneumatic shock absorber (containing nitrogen and AMG-10 hydraulic fluid) with a maximum stroke of 340 mm (13.4 in). The nosewheel was hydraulically steerable through 60°, and was covered by a large mudguard/debris deflector. The nosewheel bay was covered by tandem twin doors, the long, thin rear door closing again after undercarriage extension. The undercarriage doors were linked to the oleo by rods. Retraction and extension was controlled hydraulically, usually by the secondary hydraulic system, but by the primary system in emergency.

 

Armour plated

A key feature in ensuring survivability over the battlefield was the provision of an armoured cockpit to protect the aircraft's most vulnerable component: the pilot. This took up most of the forward fuselage section, back to Bulkhead No. 11, together with the nosewheel bay, the gun bay and the main avionics bay. The cannon bay lay between bulkheads 4 and 7 in the lower left 'corner' of the fuselage and accommodated a single AO-17A twin-barrelled 30-mm cannon (also known as the GSh-30-2, or as the 9A623) with its 250-round ammunition box. This weapon had a rate of fire of 3,000 rpm and a muzzle velocity of 870 m (2,855 ft) per second.

The Sukhoi OKB originally planned a steel-armoured cockpit 'bathtub' that would come up to the pilot's shoulders. It was designed to use two layers of hard and soft steel. Welding such a structure meant losing some of the armoured properties, but using rivets or bolts risked these fasteners becoming secondary projectiles when hit. It was finally decided that the pilot's cockpit 'bathtub' would be of welded titanium plates, each between 10 and 24 mm (0.4 and 0.9 in) thick. This was an expensive but highly efficient solution to the problem, and resulted in the pilot sitting in a box of armour which was reportedly capable of withstanding hits by up to 50 20-mm or 23-mm rounds. The titanium cockpit was not ready for installation in the first prototype, so steel plates machined to be the same weight as the 24-mm titanium sheets were used.

 

Protecting the pilot

The pilot sat as low as possible in the cockpit, and, because this restricted his ability to maintain a good allround lookout, he was provided with a rear-facing periscope set into the top of the canopy, and with rearview mirrors mounted on the windscreen arch. By necessity, the pilot's head projected a certain amount above the cockpit rails where it was vulnerable to ground fire. To protect his head, the pilot looked out through a windscreen of armoured glass, and a massive plate of armour sat above the ejection seat headrest, protecting the pilot from rounds coming from above and behind.

It was not only the pilot that was protected by armour. Virtually all vital systems and components were protected by armour, or duplicated, or both. The main engine oil tank, housed in the starboard nacelle, was protected by armour plate, and the main fuel lines leading from the main fuel tank to the engines were armoured and routed so that they could not spray fuel onto the engines if severed. The fuel tanks themselves were self-sealing and filled with reticulated foam to prevent explosions if breached.

The control surfaces were actuated via titanium control rods each 40 mm (1.5 in) thick, proved against damage by small-calibre (up to 12.7-mm) machine-gun fire. Unlike cables, these could be distorted or nicked and still continue to function. The elevator control rods were duplicated. It has been suggested that pitch controls were better protected than roll and yaw controls so that the pilot would have the maximum chance of being able to pull up to eject if he suffered catastrophic damage while at low level.

 

Cockpit systems

The pilot sat on a Severin K-36L ejection seat. The K-36L was a simplified version of the K-36D or K-36DM used by aircraft like the MiG-29 and Su-27. Surprisingly, the seat was not capable of zero-zero operation; instead, it was cleared for operation at ground level, at speeds of over 55 kt (100 km/h; 65 mph). The seat was able to cope with inverted ejections at heights of 150 m (490 ft) or above, and 90° ejections from heights of 50 m (165 ft) and above. The cockpit also incorporated an air conditioning system, though this was intended more to maintain a degree of overpressure (between 3 and 5 kPa) in the cockpit, to prevent NBC contamination, than to maintain pilot comfort. The air conditioning system also supplied air to the pilot's anti-£ suit and ventilated the windscreen and canopy, while also providing cooling air for the avionics compartments. Air for the system was bled from the eighth (final) compressor stage, and then passed through two heat exchangers and a turbocooler.

The separate oxygen system supplied a mix of air and pure oxygen to the pilot at altitudes in excess of 2000 m (6,560 ft), with pure oxygen above 7000 m (23,000 ft). The oxygen/air mix was produced in a KP-52M mixer unit. The oxygen was drawn from four 5-litre (15-MPa) bottles housed in the nosewheel bay. A BKO-3VZ emergency oxygen system was housed in the ejection seat, primarily for use during an ejection at high altitude, and gave a threeminute supply.

The cockpit was as conventional in layout as the aircraft was conventional in configuration: ergonomically laid out, but with rows of conventional analog instruments, switches and selectors, and without any electronic 'glass' display screens. The overall effect was old-fashioned and cramped, and the layout would have felt familiar to a late-generation MiG-21 pilot, or to pilots accustomed to the MiG-23 or Su-17. The panel was painted in a blue-grey colour slightly less vivid than the near-turquoise once used in Soviet combat. The cockpit incorporated many typically Soviet features, from the painted white vertical line on the lower panel which showed the pilot the stick central position (useful when recovering from a spin or departure) to the rail-mounted throttles and chunky-topped control column.

The throttles were mounted on a pair of parallel rods on the port cockpit wall, below the canopy rail. The port console mounted external stores, weapons selectors and jettison controls, as well as trimmers, drag chute, oxygen and air conditioning controls. The starboard side console and cockpit wall contained navigation system, radio, transponder, lighting and chaff/flare dispenser controls, plus the engine start panel and generator controls.

The rear cockpit of the two-seat Su-25UB was broadly similar to the single-seat or front cockpit. It lacked the gunsight and instead had a control panel for a system which allowed the instructor to simulate emergencies in the front cockpit, or to generate synthetic symbology in the frontseat sight. Full dual controls were fitted.

 

Su-25 avionics

The Su-25 was well equipped, with superb equipment and aids for precise navigation, accurate weapons delivery and self-defence. Even before details of the exact equipment fit became known, Western analysts were able to make some fairly accurate estimates of what types of equipment were fitted from the plethora of antennas, fairings, bumps and protrusions which littered the airframe from nose to tail. The nose culminated in an angular 'chisel', whose sloping face was transparent, behind which was the Klen-PS laser rangefinder. Immediately above the tip of the nose was a pair of parallel instrumentation booms, serving as pitotstatic sources for the instruments and the weapons aiming system. The main (port) PVD-18G-3M probe is always thought to have carried sideslip and AoA sensor vanes, and a cruciform RSBN-6S antenna, whereas the tandem cruciform finlets all seem to have been fixed antennas for the RSBN, and not pivoting vanes. The starboard (secondary) PVD-7 probe is a simple pitot. The RSBN-6 system is used in conjunction with RSBN-2N or RSBN-4N ground beacons for navigation, or with PRMG-4 for instrument landing approaches. This allows approaches down to 60 m (200 ft) above the runway. The DUA-3 AoA vanes were actually mounted low on the forward fuselage sides, roughly in line with the forward edge of the windscreen. A single DUA-3M yaw vane was mounted below the nose, on the centreline, just ahead of the gun muzzle. The nose contours were broadly similar to those of the similarly equipped MiG-23B and MiG-27 fighter-bombers.

Below the 'roots' of the instrumentation booms, well in front of the AoA vanes, were two small spherical antennas serving the SRO RWR, and two broadly rectangular dielectric fairings which covered the SO-69 transponder. Under the nose, just behind the yaw vane, was a small blade antenna which served the SO-69 transponder.

Further aft, the tandem antennas for the DISS-7 Doppler were housed under a flush dielectric panel immediately ahead of the gun bay access door. A similar panel on the fuselage spine covers the ARK-15M radio compass, while a slightly-swept T antenna further forward serves the R-862 radio. The 30-W R-862 VHP/UHF radio is used for routine air-to-air and air-to-ground communications in the 100-149.975 MHz and 220-399.975 MHz ranges. A 10-W R-855 emergency radio (20-59.975 MHz) is housed in the ejection seat survival pack. The wingtip pods mounted dielectric leading edges which covered SPO-15 (L-006LE) Sirena RHAWS antennas, and some later Su-25 variants had a square antenna projecting from the side of the pod. This served the Gardeniya active jammer.

Under the rear fuselage were a short 'towel rail'-type antenna serving the R-828 'Eucalyptus' radio. The 20-W R-828 radio is used for communicating with army units on the ground. Further aft on the rear fuselage was a blade antenna for the MRP-56P radio beacon receiver, and a flush disc-shaped antenna serving the RV-15 (A-031) radio altimeter. Further aft (behind the towel-rail), there was sometimes a tripole antenna below the rear fuselage, similar to that above the nose, this serving the SRZ/SRO IFF system. The sharp spike-like fairing projecting aft above the tailcone housed an RSBN antenna in the tip, with scabbed-on SRZ/SRO antennas on the sides.

The pilot entered the cockpit using a three-rung retractable boarding ladder, which is telescopic and which then folds upwards into a well incorporating two footholds. From the top foothold, the pilot steps across forward to a fold-down step, from which he can reach the cockpit itself. Grab handles are mounted behind the canopy and further aft on the side of the spine. The two-seater was fitted with a simpler entry ladder, which consisted of a simple telescopic pole to which were attached folding footsteps. This freed the pilot from reliance on ground support equipment ladders. Surprisingly, in view of this advantage, many late Su-25UBs seem to have been built without an integral boarding ladder.

 

Internal fuel tankage

The centre fuselage incorporates the wing centre-section and two integral fuel tanks, and runs between bulkheads 11B and 21. The No. 1 fuel tank (between bulkheads 11B and 28) contained 1128 litres (250 Imp gal), and the No. 2 tank (between bulkheads 18 and 21) contained an additional 1250 litres (275 Imp gal). The top of the centre fuselage section contained a duct through which ran the control rods, fuel lines and other hydraulic, air conditioning and wiring runs. In the bottom of the centre fuselage, between bulkheads 12 and 18, were the mainwheel bays. The main oleos, which incorporated 400-mm (16-in) stroke twinchamber hydro-pneumatic shock absorbers, retracted forwards. The mainwheels braked automatically during retraction, and were each covered by tandem doors. The forward doors were hinged outboard, and closed inward again after undercarriage extension.

The engine nacelles and intake ducts were attached to the sides of the centre fuselage. They were constructed from bulkheads, longerons and double skin, and stood 60 mm (2.4 in) from the fuselage sides, leaving a slot for the extraction of boundary layer air. The intake lips were raked forward by 7°, giving slightly better air flow at higher angles of attack.

 

Rear fuselage assembly

The rear fuselage ran back from bulkhead 21, and incorporated the engine mounts (at auxiliary bulkheads 20 and 27) and the tailplane attachment points. The brake chute compartment and its upwards-hinging cover were mounted on the last bulkhead, No. 35. The compartment contained a pair of cruciform PTK-25 brake chutes, each of 25 nr (270 sq ft) area, which were deployed using springs and small drogue chutes. The three-spar fixed tailfin was attached to three points above the rear fuselage, and incorporated a cooling inlet at the root for the electrical generator. A Tester UZ flight recorder was buried inside the fin structure, which also served as the mounting point for the antenna (below a dielectric fin cap), and for SPO-15 RHAWS and R-862 UHF/VHP radio antennas on the trailing edge. The trailing-edge rudder was divided into upper and lower sections, with the upper section independently controlled through the SBU-8 oscillation damper and an RM-130 hydraulic actuator.

Above the brake chute compartment, behind the fin leading edge, four upward-firing chaff/flare dispensers were recessed into the top of the rear fuselage decking, each containing 32 cartridges. Between the side-by-side pairs of chaff/flare dispensers on each side of the centreline was a slender tubular fairing projecting aft and culminating in a sharp dielectric spike. This housed an antenna for the RSBN TACAN, and had antennas for the SRO IFF system scabbed onto its sides.

The horizontal tailplane had a swept leading edge (slightly more swept than the wing) and a forward-swept trailing edge. It was built around two spars in two halves, and was then joined by a centre-section which ran through the rear fuselage. The tailplanes incorporated some dihedral to keep them clear of the jet wash from the engines, and to keep them out of the turbulent air coming off the wing. The tailplane was hydraulically adjustable to any one of three positions, one used for take-off and landing, one for normal flight, and one for dive attacks. The elevators were joined to the trailing edge of each tailplane by three hinges and were aerodynamically and mass balanced. They could deflect to 14° upward and to 23° downward. An elevator trim tab was fitted to the starboard elevator.

 

Wing design

The wing, like the tailplane, was built in two halves, and each section was constructed around a central box-section spar with ribs, longerons and stringers. The area between the first and 10th ribs on each side was sealed to form an integral 637-litre (140-Imp gal) fuel tank. Control rods (including those for the aileron) and wiring was buried in the leading edge, with slat actuator hinges mounted on load-bearing ribs. The trailing-edge section contained fuel and hydraulic lines, and mounted the flap and aileron hinges and boosters.

Moving control surfaces extended across virtually the entire span of the leading and trailing edge. Two-section double-slotted flaps occupied the inboard part of the trailing edge, with conventional ailerons outboard. The flaps could be extended to 20° for manoeuvring, or to 35° (inboard sections) and to 40° (outboard sections) for take-off or landing. The ailerons deflected to 18° upward or 18° downward. The leading edge of each wing was occupied by an interconnected five-section slat (each section with two hinges). A leading-edge dogtooth discontinuity began at the root rib of the third flap section. The slats could be deployed through 6° for manoeuvring, or to 12° for take-off and landing.

Broad flat pods were attached to the wingtips. They consisted of a dielectric antenna for the SPO-15 RHAWS forward, with a pop-down PRF-4M landing light in the underside (usually with a fixed vertical anti-glare shield inboard), and with the appropriate red or green navigation light on the outboard edge. The trailing edge of each pod was split into upper and lower sections which opened as airbrakes. The wingtip pods also incorporated connectors for the SPU-9 pilot-to-ground crew intercom system.

 

Weapons hardpoints

The wing also served as the mounting point for the Su-25's external warload, which was carried on 10 underwing hardpoints. The four inboard hardpoints under each wing were fitted with universal BD3-25 pylons, and the outboard hardpoint a PD-62-8 pylon. The latter are believed to mount only APU-60-1MD missile launch rails, compatible with the R-60 or R-60M (AA-8 'Aphid') IR-homing dogfight missiles, carried for self-defence. There is no reason why the R-73 (AA-11 'Archer') AAM should not be carried with the appropriate pylon adaptor.

The inboard underwing pylons could be fitted with a range of adaptors, allowing the carriage of a wide variety of stores. The pylons closest to the wingroot, and next but one outboard, were 'plumbed' for the carriage of PTB-800 800-litre (175-Imp gal) or PTB-1150 1150-litre (253-Imp gal) external auxiliary fuel tanks. These outboard 'tankcapable' hardpoints (the middle station of the five under each wing) can also be used for the TL-70 Kometa target winch system on the Su-25BM, and for the carriage of an SPS-141MVG-E ECM pod on aircraft assigned to the anti-radar role. These hardpoints may be the ones used for the carriage of nuclear weapons.

The BD3-25 pylons were stressed for the carnage of a wide variety of stores weighing up to 500 kg (1,100 lb) per pylon, up to the maximum load of 4340 kg (9,570 lb). The eight main pylons were seldom used simultaneously, for the Su-25 normally carries much smaller warloads on only a portion of its available hardpoints, since the carriage of a full load imposes range, performance, agility and take-off penalties.

 

The 'man pod'

Arguably the most unusual stores which can be carried underwing are the pods which constitute the AMK-8 mobile maintenance unit. The Su-25 is optimised for operation from primitive forward airstrips, and can ferry its own vital ground support equipment in underwing pods modelled on the airframe of the PTB-800 external fuel tank. There are four standard types of pod. The K-1E houses electrical power units, with a compressor and tools for maintenance and field repairs. The K-2D contains refuelling equipment (a pump and rubberised cells). The K-3SNO has maintenance tools and intake blanks, chocks, and camouflage netting, while the K4-KPA has diagnostic and checking equipment, and equipment for radio and avionics maintenance. A final, slightly reshaped AMK-8 pod is available (but is understood not to have been deployed at unit level). This is designed to transport a ground crew member, albeit in some discomfort.

The Su-25's orthodox and conventional configuration, systems and construction were accompanied by predictable and benign handling characteristics. Transitioning to the Su-25 was thus not a major step for even fairly inexperienced pilots, since the aircraft enjoyed relatively simple and uncomplicated handling procedures. It was possible to conduct most training solo, with an instructor flying chase, and it was felt that the MiG-15UTI and Aero L-39 would be adequate for instrument training and check rides, although the air force did issue a draft requirement for an Su-25UB as early as 1975. The preliminary design for the two-seat Su-25 was completed in 1977, but the project was not accorded a high priority, since many felt that the MiG-1UTI was adequate for the conversion and continuation training of Su-25 pilots.

 

The two-seat Su-25UB

Even after the decision was made to produce a two-seat trainer, the project was always subject to interruption, delay and the diversion of resources. The first export successes of the Su-25 in 1984 added impetus to the development of the trainer, and the first example of an Su-25 (designated T8UB-1 and coded 'Red 201'), finally made its maiden flight on 10 August 1985. An original Su-25UB prototype had been started in 1981, but the incomplete airframe, and two more, were actually completed as the T8M-1 and T8M-2 prototypes (and as the T8M-0 for static testing) of the advanced Su-25T. This variant of the aircraft is described in detail later. Work on the Su-25UB was delayed, and finally passed to the Production Plant No. 99 at Ulan-Ude, where a second, new T8UB-1 prototype was built, which had that plant's distinctive bear badge on its nose. The same insignia was worn by the second Su-25UB built at Ulan-Ude, 'Red 202', which acted as the second prototype. Further Su-25UBs had a similar bear, slightly smaller, on a tilted rectangular shield. The two-seater retains full combat capability and is said to be universally known as the 'Sparka' in Russian and Soviet air forces service.

In order to reduce development time to a minimum, airframe changes were avoided wherever possible. Instead of lengthening the fuselage to accommodate a second cockpit (which would have involved other airframe modifications simply to compensate), the instructor's cockpit replaced a fuselage fuel tank, with a new pair of heavily framed cockpit canopies fairing into a bulged spine. The second cockpit was raised by 0.44 m (1.44 ft), giving the instructor a 7° sight-line down over the nose. This gave the two-seater a considerable increase in keel area forward, and the tailfin was enlarged to compensate. The horizontal tail was increased in area, and was of revised profile. The Su-25's usual retractable folding ladder was replaced by a simpler telescopic tubular strut supporting three narrow footrests. The Su-25UB's heavily stepped cockpits gave the backseater a better view forward than was obtainable in most Soviet two-seat trainers, and this made provision of the almost-traditional periscope less essential. It was offered as a customer option on the Su-25UBK, the export version of the two-seater, but was seldom requested. The prototypes and early Su-25UBKs did not have the periscope fitted, but many Soviet UBs were so equipped.

Some reports suggest that Sukhoi made plans for a threeseat trainer (with all three cockpits 'in tandem') but the reasons for such an aircraft remain unclear, unless it was expected to serve as a high-speed liaison aircraft. Development was reportedly abandoned soon after it began in 1991. The aircraft was allegedly referred to within the OKB as the Su-25U3.

 

Trainer family

The Su-25UB combat trainer formed the basis of the stillborn Su-25UT (later redesignated Su-28). This aircraft was intended as a dedicated advanced trainer to replace the Aero L-29 and Aero L-39, both with the Soviet air forces and with the paramilitary DOSAAF. It was a simplified, unarmed two-seater, with no combat capability, no gunsight, no laser rangefinder, no RHAWS, no chaff/flare dispensers, and no internal cannon. Weight was reduced by 2000 kg (4,400 lb). Fuel tank linings were removed, and provision was made for just four underwing pylons, for the carriage of external fuel tanks only. The prototype was produced by conversion of the T8U-1, and first flew in its new guise on 6 August 1985. The Su-25UT introduced a revised wing leading-edge planform, with the dogtooth discontinuity between inboard and outboard leading-edge sections replaced by a short length of leading edge of reduced sweep, giving a gentle step in the leading-edge profile. The Su-25UT prototype was painted in a predominantly white colour scheme, with red and blue trim, and initially with DOSAAF tail markings and the code 'Red 07'. The aircraft took part in the 1988 DOSAAF acrobatic championships, and in the hands of Yevgeni Frolov seized a creditable third place. It was later receded with the Paris air show code 'Blue 302' for the 1989 Pans Air Salon, by which time it also wore the revised Su-28 designation on its intakes. Only a single prototype of the Su-25UT was completed, and no orders were forthcoming. Reports that the Su-25UT prototype was subsequently converted to become the Su-25UTG are entirely without foundation, and the aircraft remains in use with the OKB's test fleet at Zhukhovskii.

 

Su-25UTG for the navy

Another derivative of the Su-25UB was the navalised Su-25UTG. This had many of the same modifications as the Su-25UT/Su-28, but was especially strengthened to withstand the stresses of a carrier landing and was fitted with a retractable arrester hook, a revised undercarriage and a carrier landing system. The hook resulted in the new variant's change in designation (the Russian for hook being Gak). Sukhoi had hopes that a carrierborne single-seat Su-25 might be selected as a carrierborne attack aircraft for the Tbilisi (now Kuznetsov) and its sister ships (all later scrapped or cancelled). The T8-4 was tested on the dummy deck at Saki in 1984 at the same time as were the T10-24, T10-25 and the MiG-29KVP. The selection of the multirole MiG-29K for the new carrier air wings led to these hopes being frustrated, although it was clear that the Su-25 could form the basis of a cheap and simple land-based but carrier-capable trainer for teaching carrier landings. It was anticipated that the aircraft would primarily be used for teaching experienced MiG-29 and Su-27 pilots therudiments of carrier landing, mainly using dummy carrier decks like the one at Saki. The majority of actual carrier landing training would be conducted after pilots had converted to their operational type (the Su-27K or MiG-29K), perhaps after a familiarisation flight or two in the Su-25UTG. Since the Su-25UTG would not actually be based aboard carriers, but would instead fly to and from a carrier from its shore base, it was decided that wing folding would not be required.

 

The varied career of the Su-25UTG

The Su-25UTG prototype (designated T8-UTG1 and coded 'Blue 08') made its maiden flight in September 1988. The aircraft was flown onto Tbilisi on 21 November 1989 by Sukhoi project pilot Igor Votintsev and LII pilot Alexander Krutov, landing after the Su-27K and MiG-29K. The Su-25UTG may have been converted from an Su-25UB in the OKB's own workshops. The aircraft certainly wore a Sukhoi logo on its nose, instead of the Ulan-Ude factory bear badge applied to most two-seaters (though, interestingly, never to export Su-25UBKs). The single prototype was followed by a batch of 10 new production Su-25UTGs. Five aircraft (coded 'Red 04', '06', '07', '10' and '11') were sent to Severomorsk, home to the Kuznetsov's air wing and to an AV-MF Su-25 regiment. Five more (coded 'Red 60', '61', '62', '63' and '64') were left behind at Saki where they became part of the Ukrainian forces. 'Red 60' is believed to have been written off in an inadvertent wheels-up landing, while 'Red 07' suffered a fatal accident near Murmansk on 11 November 1992.

Even though only one carrier entered service, the four Su-25UTGs in service with the unit at Severomorsk were considered to be inadequate for the training task which faced them. Accordingly, Sukhoi was asked to produce 10 similar aircraft by conversion of existing Su-25UBs under the designation Su-25UBP. They were to have the same airframe strengthening and naval features as the Su-25UTG, but were also to be fitted with a retractable inflightrefuelling probe. There have been reports that the Su-25UBP programme has been halted, but it is unclear whether this situation is temporary. The Sukhoi OKB has not given up its quest to produce an operational carrierborne Su-25 derivative, and reports suggest that the bureau may still be working on a single-seat, carrier-capable, probe-equipped Su-25TP based on the advanced Su-25T airframe, equipped with Kh-31 and Kh-35 ASMs.

 

The true combat debut

Following the successful combat evaluation of the Su-25 in Afghanistan, it became inevitable that production examples of the type would be used in the conflict when they became available. Twelve of the first Su-25s equipped the 200th Independent Shturmovik Squadron (often erroneously described as a Guards unit, and as being either a regiment, or alternatively a flight) at Shindand. This unit later transferred to Kabul (probably during 1982) and expanded to 24 aircraft (with 80 pilots) to become the 60th OShAP (sometimes described as the 80th OShAP). The regiment's commander was given special dispensation to conscript reinforcement aircraft and aircrew from Su-25 units in neighbouring republics, notably Turkmenistan. The 60th OShAP finally withdrew to Sital Chai in Azerbaijan in 1988.

Another long-term Su-25 unit in Afghanistan was the 378th OShAP, in action from 1984. A third Su-25 regiment served in Afghanistan between October 1986 and November 1987. This was the 368th OShAP, which transferred to Afghanistan from Uzbekistan, and moved to Demmin-Tutow in East Germany following its combat tour, during which it was based at Bagram and Kandahar. The unit may have been one of several which made brief deployments to Afghanistan.

While the Su-25 demonstrated great accuracy and good battle damage tolerance from the very start of its involvement in Afghanistan (especially by comparison with other aircraft in use in the theatre), it was equally clear that there was considerable scope for improvement. The threat posed by Blowpipe, Stinger and Redeye SAMs prompted the installation of four ASO-2V chaff/flare dispensers in the upper surfaces of the rear fuselage, on each side of the fin trailing edge. These usually contain up to 30 PPI-26 IR decoy flares, giving a total of 120 flares.

 

The effect of the Stinger

The advantage of having two engines was fully exploited in the Su-25, in which the powerplants are mounted so close together that damage to one engine could cause collateral damage to the other. This became abundantly clear following the 1984 introduction of the Redeye SAM by the Mujahideen, and by the October 1986 delivery of General Dynamics FIM-82A Stinger SAMs. The introduction of Redeye was followed by the loss of two Su-25s in very quick succession, these aircraft having proved unable to decoy the SAMs away using flares. Flare capacity was increased from 128 to 256, by the addition of four 32-round dispensers scabbed onto the top of the engine nacelles. When the Mujahideen started using Stinger, the effect was even more dramatic. Four Su-25s were destroyed in three days, with two pilots lost. The Stingers tended to detonate close to the engine exhaust nozzles, piercing the rear fuel tanks with shrapnel and causing fires which could burn through control runs, or causing damage to the far engine. In order to prevent damage to one engine from taking out the other, a 5-mm armour plate was added between the two engines (acting as a giant shield and firewall), about 1.5 m (5 ft) long.

A new inert gas (Freon) SSP-2I/UBSh-4-2 fire extinguisher system was provided. This consisted of six UTBG sensors in the engine nacelles, which were connected to cockpit displays. The pilot had four push-buttons to actuate the extinguisher's first and second stages for each section of the engine. The Freon was stored in spherical 4-litre (0.87-Imp gal) bottles, each containing 5.64 kg (12 lb) of gas pressurised at 6.9 to 14.2 MPa.

These modifications proved a great success, dramatically reducing the Su-25's loss rate. No Su-25 equipped with the inter-engine armour was lost to a Stinger, although many were hit. The modifications were quickly incorporated on the production line, and were retrofitted to existing Su-25s.

Additional improvements were added during the period in which Su-25s were fighting in Afghanistan. On aircraft from the 10th production series, for example, the aileron control rod was fully faired in and the aileron trim tab was deleted. Elevator pivots were more effectively faired. Tenth series Su-25s also gained a second external APU/GPU socket. Other features appeared gradually, and cannot yet be pinpointed to a particular production series. The nosewheel was changed, from one which accepted a tubeless KN-21-1 tyre to one which took a tubed K-2106 tyre. The single long fuel tank access panel on the top surface of each wing was replaced by three shorter access panels, side by side. Small fins were added to the inboard faces of the bottom of each wingtip fairing, acting as glare shields when the PRF-4M pop-down landing lights were deployed. At the trailing edge of these pods, the airbrakes themselves were modified. Previously simply splitting 50° up and 50° down to give a shape with the point forwards, they gained auxiliary segments which hinged upwards through another 90° at their trailing edges to give a shape reminiscent of a W turned on its side, with the central point pointing forwards. During production of the ninth production series the cannon muzzle was redesigned, with the ends of the twin barrels covered by a single muzzle shield. Many late production Su-25s had their distinctive SRZ and SRO 'Odd Rod' antennas replaced by simple blade antennas, similar to the SRO antennas fitted to later MiG-29s (which retained the traditional tripole SRZ antennas above their noses). The revised antennas may have combined interrogator and responder functions.

 

The 'Frogfoot' becomes the 'rook'

The Su-25 proved extraordinarily successful in Afghanistan, enjoying greater accuracy and a lower loss rate than the MiG-27s, MiG-21s, MiG-23s and Su-17s used there. The Mujahideen dubbed the Su-25 the 'German product', believing that its prowess and effectiveness marked it out from the other Soviet aircraft operating in-theatre, and indicating that it must have come from elsewhere. Combat experience in Afghanistan also generated a Russian nickname for the aircraft: 'Grach' (Rook). Publicists and official historians credit the nickname to ground troops, who reportedly appreciated the aircraft's close support capability which they likened to the mother rook's habit of covering her young with her wings when faced with danger. Other sources suggest that the 'Grach' nickname was first applied by the pilots of the 200th series Su-25s also gained'a second external APU/GPU socket. Other features appeared gradually, and cannot yet be pinpointed to a particular production series. The nosewheel was changed, from one which accepted a tubeless KN-21-1 tyre to one which took a tubed K-2106 tyre. The single long fuel tank access panel on the top surface of each wing was replaced by three shorter access panels, side by side. Small fins were added to the inboard faces of the bottom of each wingtip fairing, acting as glare shields when the PRF-4M pop-down landing lights were deployed. At the trailing edge of these pods, the airbrakes themselves were modified. Previously simply splitting 50° up and 50° down to give a > shape with the point forwards, they gained auxiliary segments which hinged upwards through another 90° at their trailing edges to give a shape reminiscent of a W turned on its side, with the central point pointing forwards. During production of the ninth production series the cannon muzzle was redesigned, with the ends of the twin barrels covered by a single muzzle shield. Many late production Su-25s had their distinctive SRZ and SRO 'Odd Rod' antennas replaced by simple blade antennas, similar to the SRO antennas fitted to later MiG-29s (which retained the traditional tripole SRZ antennas above their noses). The revised antennas  may have combined interrogator and responder functions.

 

The 'Frogfoot' becomes the 'rook'

The Su-25 proved extraordinarily successful in Afghanistan, enjoying greater accuracy and a lower loss rate than the MiG-27s, MiG-21s, MiG-23s and Su-17s used there. The Mujahideen dubbed the Su-25 the 'German product', believing that its prowess and effectiveness marked it out from the other Soviet aircraft operating in-theatre, and indicating that it must have come from elsewhere. Combat experience in Afghanistan also generated a Russian nickname for the aircraft: 'Grach' (Rook). Publicists and official historians credit the nickname to ground troops, who reportedly appreciated the aircraft's close support capability which they likened to the mother rook's habit of covering her young with her wings when faced with danger. Other sources suggest that the 'Grach' nickname was first applied by the pilots of the 200th OShAE, many of whom were former MiG-21 pilots, who likened the slow and ungainly Su-25 to a rook, by comparison with their fast and graceful Falcons. Whoever invented the name, cartoon rook badges soon started to appear on Su-25s flown in Afghanistan. This rook badge has become a widely accepted insignia for Soviet Su-25s, and was applied to many of the aircraft used in East Germany. There have been unconfirmed suggestions that the badge is worn only by Su-25s that flew in Afghanistan.

 

Bringing back the pilots

The aircraft were often hit by ground fire and SAMs, habitually after they had overflown the target and were egressing. The damaged Su-25s usually limped home (even after a direct Stinger hit), often too badly damaged to fly again but generally saving the precious pilot. The aircraft were even sometimes repairable and were always at least a good source of spare parts. The Su-25 was effectively invulnerable to cannon fire; it took 80 20-mm hits to down an Su-25, compared with only 15 for a MiG-21 or Su-17.

Colonel Alexander Rutskoi, later briefly President of the Russian Federation, flew as an Su-25 pilot in Afghanistan while serving on the staff of the Commander of the 40th Air Army, and became the war's most highly decorated pilot. Some reports suggest that the T8-15 ('Blue 15') was one of the aircraft flown by Rutskoi in Afghanistan, and one which was severely damaged while being flown by him on two separate occasions, once by ground fire and once by two AIM-9s fired by a Pakistani F-16. Rutskoi wras unluckier in April 1986 when he was downed by a SAM, ejecting inverted at only 100 m (330 ft) altitude. He was forced to eject again during his second tour of duty in Afghanistan, on 4 August 1988, when he was once more engaged by a Pakistani F-16. Hit by an AIM-9, Rutskoi was forced to eject from his crippled aircraft ('Red 03') and was captured, being released after two weeks. The remains of his aircraft were put on display at Kamra. Some reports suggest that Rutskoi commanded a unit (perhaps an element of the 378th OShAP) which conducted sustained night operations before being disbanded and split up between other units in-theatre.

 

Afghanistan weapons

The Su-25 used a wide variety of weapons during the long involvement in Afghanistan. In order to maximize performance and agility, the Su-25s were seldom fully laden, often carrying weapons on only two or four underwing pylons. A common loadout was two or four S-24 240-mm unguided rockets, or a similar number of shapedcharge S-25 OFMs. Underwing fuel tanks were sometimes carried, either on the innermost hardpoints or on the third pylons out from the root. Various 250-kg or 500-kg (550-lb or 1,100-lb) bombs were also used in Afghanistan, and unguided small calibre rockets were carried in UB-32-57 (32 unguided 57-mm rockets per pod) or B8M (20 unguided 80-mm rockets per pod) pods. Towards the end of the Soviet involvement in Afghanistan, Su-25s started to be seen carrying guided weapons, including the S-25L laser-guided, tube-launched 250-mm rocket, the Kh-25ML and the Kh-29L laser-guided ASMs. According to the OKB, 139 laser-guided missiles were launched by Su-25s in Afghanistan, and 137 of them scored direct hits.

Another commonly seen Su-25 weapon which may have been used in Afghanistan is the SPPU-22-01 cannon pod. The Su-25 can carry up to four of these pods, usually on its innermost pylons. Each pod contains a single twin-barrelled 23-mm NR-23 cannon, with 260 rounds of ammunition, and with barrels which can be depressed through 30° up, allowing the aircraft to strafe a target simply by overflying it in level flight. This is especially effective against line targets (e.g., vehicles on a road). The pod may be mounted backwards, with the barrels elevated through 23° up, allowing the aircraft to fire backwards after overflying the target. It is common practice to pair a forward-firing and rearwardfiring pod. Each pod had a rate of fire between 3,000 and 4,000 rounds per minute.

 

Afghanistan combat report

Twenty-three Su-25s were lost in action in Afghanistan; more were destroyed on the ground, including eight at Kabul in a single rocket attack on 23 June 1988. The aircraft shot down represented about 10 per cent of Soviet fixed-wing losses in Afghanistan, with a reported loss rate of one per 2,800 flying hours. The type made 60,000 operational sorties. Interestingly, the cockpit armour of the Su-25 proved particularly successful, and no Su-25 pilot was killed by projectiles or shrapnel. Several Su-25 pilots received the Soviet Union's highest honour, the Hero of the Soviet Union. Lieutenant Colonel Pietr V. Ruban was given a posthumous award, and a second was awarded to a Captain Dyakov. Other well known Hero of the Soviet Union awards were made to Captain Vladislav Gontcharienko, who flew 415 combat missions, and to Senior Lieutenant Konstantin G. Paliukov, who destroyed two Stingers launched against his formation leader, using gunfire and unguided rockets, during a December 1986 mission. He was killed on 21 January 1987, ejecting after being hit by another Stinger. He held off the Mujahideen for an hour before killing himself (and several of his tormentors) with a hand grenade.

According to official reports, only one type enjoyed a lower loss rate in Afghanistan than the Su-25, and that was the obsolete 11-28. Their tail gunners tended to discourage Mujahideen gunners from popping out of cover to fire as the ancient bombers egressed, and were also able to call out rear hemisphere threat warnings. Encouraged by this, Ilyushin again promoted its aircraft (as the 11-102) as an Su-25 replacement, but the aircraft was again rejected and the air force preferred to concentrate on Sukhoi's own extensively modified Su-25 derivative, the Su-25T.

 

War in the former republics

Afghanistan was not the only war from which the designers of the Su-25 could draw lessons based on real combat experience. Azeri forces used Su-25s in their war against Armenia during 1992, while from late 1992 the Georgians used Su-25s against Abkhazian forces fighting for independence, who were themselves supported by Russian forces, which included Su-25s. Among the earliest incidents of this brief but bloody conflict (which lasted until the end of 1993) was an engagement on 27 October 1992, involving two Georgian Su-25s and two Russian Su-25s which were escorting Mi-8s delivering humanitarian relief. None of the aircraft were shot down. Six Georgian Su-25s (then virtually the entire Georgian Su-25 fleet) were shot down later in the war, together with a Russian Su-25 and one of the Su-25s handed over by Russia for operation by Abkhazian forces. Following the secession of Abkhazia, the last Georgian Su-25 was shot down on 5 November while conducting operations against rebel Zviadist forces who supported former President Zviad Gamsakhurdia. Georgian Su-25s wore standard Russian camouflage and red star markings, and this may have been the origin of the Russian tricolour tailfin badges applied to some Russian Su-25s.

While development of the extensively redesigned Su-25T progressed slowly, Sukhoi introduced some final improvements to the baseline single-seat Su-25 and two-seat Su-25UB. The most important of these was the adoption of the R-195 engine, a derivative of the R-95 which offered increased thrust and a lower IR signature. The powerplant had been intended primarily for the heavyweight Su-25T, but its availability came as a blessing to Sukhoi, which saw it as a welcome means of improving Su-25 and Su-25UBK performance, even though only a relatively small number of aircraft remained to be built. The new engine was first flown in the T8M-1 prototype, while the T8-14 and T8-15 were re-engined to enable the engine trials to be completed more swiftly.

The T8-15 (c/n 10192, already used for combat trials in Afghanistan, and badly damaged while being flown by Alexander Rutskoi) was used to make the Su-25 's Western public debut at the 1989 Paris Air Salon at Le Bourget. Some sources suggest that the aircraft was again re-engined with its original R-95s to preserve secrecy, but this seems unlikely. It is more probable that the Sukhoi OKB merely failed to remark on the change of engine.

The installation of the new engine necessitated some changes to the engine nacelles and to the rear fuselage. Auxiliary intakes were added below the rear part of the nacelle, and additional auxiliary intakes were added above the nacelle. The small intake at the base of the tailfin was removed. A tubular pipe projected from the centre of the jet pipe of the R-195, mixing cool bypass air into the middle of the jet efflux to reduce the engine's IR signature. The R-195 had a designated service life of 1,500 flying hours or seven years, with a 500-hour TBO. Following its participation in the Paris Air Salon, the T8-15 was used for a variety of trials, including some maximum weight weapons tests. It was finally retired to the Central Air and Space Museum at Khodinka airfield on Leningradsky Prospekt in Moscow.

 

The Su-25BM target tug

There is some confusion regarding the designation of the R-195-powered single-seat Su-25s. Some have suggested that the only single-seaters powered by the new engine were the batch of 50 Su-25BM (Bukshir Mishenyei) dual-role fighter-bomber/target tugs. Others suggest that more Su-25s were built or retrofitted with the R-195 engine, and only a proportion of these should be referred to as Su-25BMs. Confusingly, some authorities have even suggested that certain Su-25BMs were powered by the R-95 engine. The reengined aircraft does retain the same ASCC 'Frogfoot-A' reporting name.

Work on the Su-25 target tug began in 1986, and the OKB looked at the possibility of producing either a singleseat or two-seat version. As far as is known, a decision was made to concentrate on producing a target-towing derivative of the R-195-powered single-seater, under the designation Su-25BM. This was always intended to be a 'convertible' which could be reconfigured for full combat duties at squadron level. When operating in the target-towing role, the aircraft carried a TL-70 winch unit with a Kometa towed target below the port wing, and an inert FAB-250 or FAB-500 bomb below the starboard wing to counter the asymmetry in weight and drag. The TL-70 winch could wind out 2300-3000 m (7,545-9,845 ft) depending on the type of target. A new TL-70 target control unit panel replaced the gunsight and gunsight control panel, and an unidentified fairing, with a long, shallow knife-blade antenna, was carried on the centreline. This may have served the Planyer-M system, which could detect target miss-distances and display them in the cockpit, and simultaneously transmit them to a suitably equipped ground station. As an alternative to towed targets, the Su-25BM could carry four rocket-powered free-flying PM-6 targets, or four M-6 parachute targets.

As far as can be ascertained, the R-195-engined Su-25BM has attachment points for the Vyuga datalink pod, used in conjunction with the Kh-58U/E (AS-11) anti-radiation missile. This latent capability may have been the reason for the reported transfer of Su-25BM target tugs from the 16th Air Army's target facilities unit at Damgarten to the 368th OShAP at Demmin-Tutow. Certainly, the 368th OShAP did include 12 R-195-engined aircraft, but it cannot be confirmed that they were the ex-Damgarten target tugs, nor that they were designated as Su-25BMs. Su-25BM target tugs probably equipped a number of squadron-sized specialised target-towing units, but were doubtless also attached to other units in ones and twos. The Su-25BMK designation is theoretically applied to export versions of the Su-25BM, but, as far as is known, none have been delivered to any overseas customer, and the R-195 engine was once rumoured not to have been cleared for export.

 

Su-25T: the second generation

The main application of the R-195 engine was for the advanced 'Frogfoot' in all of its T8M forms - the Su-25T, Su-25TM, Su-34 and Su-39. These designations covered similar sub-variants of an advanced single-seat attack aircraft, based on the airframe of the two-seat Su-25UB, but with the former instructor's cockpit space occupied by advanced avionics and some restored internal fuel tankage in new No. 3 and 4 fuel tanks. Total internal fuel capacity increased to 3840 kg (8,466 lb) from the Su-25UB's 2725 kg (6,008 lb) and the original single-seater's 3000 kg (6,614 lb). The T8M retained the profile of the Su-25UB, but with metal skinning replacing the rear cockpit canopy. This gave the aircraft a distinctively humped appearance.

Work on a 'super Frogfoot' began in 1981, just as the results of the combat evaluation of the original T8 prototypes were being evaluated, and as recommendations were being made that this original aircraft should be put into production. The new variant would be a heavier aircraft, with even better resistance to ground fire and battle damage, and with more advanced sensors and systems optimized for the night and all-weather attack roles. Vladimir Babak was given leadership of the project, which was accorded a high priority.

 

T8M changes

Such was the importance attached to the new T8M that the partially complete T8U prototype airframes (and a T8U static test airframe) were taken over to form the basis of the new version. Work on these airframes began in 1983. Internal volume was exploited wherever possible, allowing the increased internal fuel already referred to, and making it possible to find space for many new avionics systems. These included a new Voskhod navigation system, with twin digital navigation computers. Armour was increased and improved, with the avionics bay, fuel feed tank and fuel pipes all gaining extra protection. Fuselage compartments adjacent to the fuel tanks were filled with a porous elastic filler, intended to prevent impulse splashing of the fuel if hit by a bullet or shrapnel fragment. The OKB estimated that survivability had been enhanced by a factor of between four and six.

In order to provide extra internal volume, the original cannon bay was deleted, and it was decided to carry the gun externally, below the belly. At first it was hoped that the T8M (soon given the air force designation Su-25T) would be armed with a new 45-mm cannon, with depressing barrels for ground strafing. In the event, the Su-25T used the same AO-17A (GSh-30-2, 9A623) 30-mm cannon as the basic Su-25, but carried below the fuselage as the NPPU-8M, offset to starboard by 270 mm (10.5 in). This necessitated moving the nosewheel another 220 mm (8.6 in) to port.

 

Improved sensor system

The nosecone was lengthened slightly, and tapered less sharply in plan view. The nose window was enlarged to allow it to serve the Krasnogorsk OMZ 1-251 Shkval (squall) optical-TV system, which combined high-resolution television, a Prichal laser rangefinder and target designator, and a Vikhr laser guidance system. The Shkval could present a wide-angle (36° x 27°) picture for target search, or a 23-times magnified (1° x 0.7°) picture for tracking. The sight-line could be steered through 70° horizontally, and from 15° above the centreline to 80° below. A moving armoured target could be tracked to an accuracy of 0.6 m (2 ft) at ranges of up to 8 km (5 miles). The laser designator illuminated a 5 x 5-m (16.4 x 16.4-ft) box, and transmitted steering commands directly to the laser sensors mounted at the rear of the 9M120 Vikhr laser-guided tube-launched missiles. The system was essentially the same as that fitted to the Ka-50 'Hokum', and made the Su-25T fully compatible with a wide range of laser-/TV-guided bombs and missiles.

For night and all-weather missions, the Su-25T could carry a Mercury LLTV pod under the fuselage. The image from this conventional TV camera could be electronically enhanced, and offered an 18.2° x 13.7° field of view for search and a 7.3° x 5.5° field of view for tracking. This allowed a tracking range of 3 km (1.9 miles) for a tanksized target. Narrow FoV pictures were displayed on a CRT display, while wide FoV imagery was displayed on the new wide-angle HUD. Surprisingly, this was one of the few new features within the cockpit, since, unlike second generation versions of the MiG-29 and Su-27, the Su-25T's cockpit was not subjected to a major redesign or modernisation. A new IT-23 hooded display screen for the 1-251Shkval was added to the top part of the right-hand side of the panel, but there were no CRT or LCD display screens.

The Su-25T was given a much improved Irtysh ECM and defensive avionics system, with a Gardeniya active ECM jammer, an SPO-15 Beryoza RHAWS, and SPO-32 Pastel RWR. RHAWS coverage is through a full 360° In azimuth, and 30° in elevation, going from 1.2-18 GHz. The system can be used for cueing Kh-58 ARMs. From the third prototype an L-166S1 Sukogruz IR jammer (based on a powerful 6-kW Cesium lamp) was installed in a cylindrical fairing at the base of the tailfin, alongside the UV-26 chaff/flare dispensers flush-mounted in the rear fuselage. They contained a total of 192 PPI-26 IRCM or PPR-26 chaff cartridges.

The airframe of the T8M was otherwise almost unchanged, although it gained BU-45A hydraulic boosters (as used by the MiG-21) for the elevator controls. The T8M-1 prototype made its maiden flight at Zhukhovskii on 17 August 1984, in the hands of A. N. Isakov. This aircraft (apparently coded 'Red 02') had a glazed rear canopy painted onto the spine. Subsequent aircraft did not hide the fact that they merely had metal skinning which followed the same contours as the twoseater's cockpit. Two more prototypes joined the test programme in 1985 and 1986, although A. Gontcharov was forced to eject from the T8M-2 during trials. Two more non-flying airframes were used for static (damage to airframe) and fatigue tests.

 

Su-25TK for export

The new variant was offered for export under the designation Su-25TK (with the T8M-3 serving as prototype/demonstrator, after slight changes to the avionics), until an entirely new designation was applied by the OKB. The Su-25TK was redesignated Su-34 in an effort to attract funding, and to give the impression that it was a new design. The designation was not recognised by the air force, and was eventually reassigned to the production version of the Su-27IB, although again it remained unrecognised by the air force. One of the Su-25Ts made its debut as the export Su-25TK demonstrator at Dubai in 1991. The aircraft was fitted with a BA-58 Vyuga datalink pod under the fuselage, for compatibility with the Kh-58 (AS-11 'Kilter'). The streamlined fairing at the base of the rudder was clearly empty on this aircraft, lacking the IR jammer in its trailing edge, and instead having flush-fitting twin chaff/flare dispensers let into the sides.

 

The end of the Su-25?

An initial production series of eight Su-25Ts was produced at Tbilisi, the first flying in July 1990. By then, work was already well advanced on the further improved T8TM, or Su-25TM, which combined radar and imaging infra-red sensors to maximise night/all-weather capability. Unfortunately, once Georgia gained its independence it was decided that all further Su-25 production would have to be undertaken at Ulan-Ude. This effectively brought production to a complete halt for months, or perhaps even years. The step was essential, however, since production of the baseline Su-25 in war-torn Georgia ground to a halt almost immediately, and has not recommenced. Any nation wishing to buy a new single-seat Su-25 or Su-25K would probably have to persuade the factory at Ulan-Ude to tool up for production of the type. This would be by no means straightforward, since the plant has hitherto built only Su-25 variants based on the hump-backed two-seat airframe. It is probably safe to say that the first-generation Su-25 is effectively dead in its single-seat form.

The Su-25TM differs very little from the Su-25T/TK in external appearance. Its principal advantage lies in its ability to carry new pods under the fuselage centreline. The first of these was the Kinzhal (Dagger) 8-mm MMW (Millimetre Wave) radar pod, and the second was the Khod (Motion) FLIR or IIR pod, which used virtually the same pod airframe. The Leninets Kinzhal pod was dropped after development problems, mainly because it had been sourced from the Ukraine, and the OKB understandably wanted all equipment to come from a single republic, after the difficulties it had experienced having a production plant in Georgia. Leninets is based in St Petersburg, and estimated that it would take at least two years to build a new version using Russian-supplied components. Babak himself estimated that four years would be required, including the writing of new software.

 

Kopyo-25 radar for the Su-25TM

The aircraft can also carry a centreline Kopyo-25 radar pod. The Phazotron Kopyo radar is a close relation to the same company's Zhuk, but with a somewhat smaller antenna. It has same air-to-ground radar modes but is usually thought of as an air-to-air radar, and was developed primarily for use in MiG-21 upgrades. Of four test sets produced, one was used for ground and airborne rig testing, two were provided to Mikoyan for the MiG-21-93, and one was podded for trials with the Su-25TM. To the Su-25TM, the Kopyo pod brought a degree of terrainavoidance capability, as well as various types of Doppler beam sharpening, radar mapping, target designation and missile guidance function.

The Kopyo-25-equipped Su-25TM is described as being compatible with the BVR-capable R-27 (AA-10 'Alamo') and R-77 (AA-12 'Adder') air-to-air missiles. Such a capability did not come anywhere close to transforming the sluggish and slow Su-25TM into a fighter, but it did introduce some useful versatility, and a healthy self-defence proficiency. More importantly, the new radar allows the Su-25TM to carry weapons like the Kh-31A (AS-17 'Krypton') and Kh-35 (AS-X-20 'Kayak').

The first Su-25T prototype (T8M-1) served as the Su-25TM prototype, redesignated as the T8TM-1. It was followed by two more prototypes (T8TM-2 and T8TM-3, 'Blue 09' and 'Blue 10'), which may have been converted from Su-25Ts (perhaps T8M-9 and T8M-10), or which may have been newly built. The second Su-25TM made the type's public debut at the massive display mounted for CIS leaders at Minsk Maschulische in February 1992. The Su-25TM is designated Su-39 internally, by the OKB, but this designation remains entirely unofficial.

Development of a navalised version of the Su-25TM (known as the Su-25TP) — which combined features of the Su-25TM with the specific naval features of the Su-25UTG - may have been halted, suspended or abandoned. No prototype has yet been flown. During 1995 and 1996, the Sukhoi OKB appeared to have lost some of its political influence, and other aerospace organisations, including the MiG/MAPO/Kamov grouping, seemed to be winning back some of the influence they had lost. The fulfilment of Russian air forces' requirements became more open to competition, and Sukhoi could no longer expect orders for all of its products. In this new environment, the Su-25TM has failed to win a production order, and its future must be open to question. An offer of licence-production in Poland failed to generate an order from the Polish air force, and only the UAE and Bulgaria have seriously looked at the type. Bulgaria and Slovakia would reportedly be interested in acquiring a handful of Su-25TMs to act as pathfinders for their respective air forces' existing fleet of baseline Su-25s. Negotiations began in late 1993 and 1995 for the lease of small numbers of Su-25TMs to both nations.

 

An uncertain future

The Sukhoi Su-25 has proved the validity of its original concept, but has also demonstrated a need for more effective night-attack sensors and systems, and for improved armour and self-protection systems. Unfortunately for Sukhoi, just as these were finally developed for the advanced Su-25T and Su-25TM, the end of the Cold War resulted in a massive decrease in defence spending. The Su-25TM is probably still too revolutionary to be a core programme, and to attract a share of much more scarce funding. Money is far more likely to be allocated to advanced versions of the MiG-29 and Su-27, which have been designed to be compatible with advanced precision-guided air-to-surface weapons, and which offer greater versatility. In a time of economic cutbacks, such multi-role aircraft are almost certainly more likely to prosper than less flexible single-role aircraft, even if the latter are superior. The future of the Su-25 and its advanced derivatives will depend on their ability to attract export orders. Unfortunately, overseas customers have so far proved to be no more far-sighted than the superpowers in being able to order such a specialised attack aircraft, and such a superficially unimpressive performer. America has allowed the A-10 to wither and die, and Russia looks set to do exactly the same with the Sukhoi Su-25.

 

 Jon Lake