Sukhoi’s “Frogfoot” 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.
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.
Having successfully built up a family of
dedicated ground attack and close support aircraft during the war, the
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
Five completed airframes at
Revival of the concept
The USAF launched its own AX requirement with
a request for proposals on
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
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
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
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
The T8 mock-up was presented to the
authorities at Khodinka, near
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
The T8-0 was delivered for static testing on
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
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'.
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
T8 trials in
The Su-25 has been associated with the Soviet
The fourth Su-25 prototype (T8-4) was left to
complete state acceptance tests at Mary in
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
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
Su-25 into production and for export
The first production Su-25s
rolled off the line at
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
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.
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
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.
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.
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.
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.
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.
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.
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
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.
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
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
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
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
Another long-term Su-25 unit in
While the Su-25 demonstrated great accuracy
and good battle damage tolerance from the very start of its involvement in
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
The 'Frogfoot' becomes the 'rook'
The Su-25 proved extraordinarily successful in
The 'Frogfoot' becomes the 'rook'
The Su-25 proved extraordinarily successful in
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
The Su-25 used a wide variety of weapons
during the long involvement in
Another commonly seen Su-25 weapon which may
have been used in
Twenty-three Su-25s were lost in action in
According to official reports, only one type
enjoyed a lower loss rate in
War in the former republics
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
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
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.
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
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
The end of the Su-25?
An initial production series of eight Su-25Ts
was produced at
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
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 '
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
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