Su-25 Frogfoot [NATO reporting name]
By the early 1980s the single-seater close support Su-25 Frogfoot was supporting Soviet forces in Afghanistan, where it proved to be a difficult target for Afghan antiaircraft guns. Series production of the army’s Su-25 started at the Tbilisi aircraft plant in 1976, with test flights being conducted up to 1980. Smaller than the American Fairchild A-10 Thunderbolt, the Su-25 had lower thrust and was assessed to carry less ordnance than its American counterpart.
Nonetheless, this aircraft was armed with a 30mm multi-barrel cannon beneath the centre fuselage and had ten hardpoints for ordnance. Flexible 23mm cannon could also be carried in SPPU-22 pods under the wings. There were five stations for suspending weapons under each wing. Eight of the stations are interchangeable pylon carriers, which provide for the attachment of various bomb and rocket armament. R-60 air-to-air missiles are mounted on two additional external points under each wing. Maximum speed was believed to be about 880km/h, with a range of 550km.
The Su 25 is successor to the famous Il 2 Shturmovik of World War II. Fast and heavily armed, it is reputedly the most difficult plane in the world to shoot down.
The air war in Vietnam highlighted the need for simple close-support aircraft able to operate from unpaved strips close to the front. Such warplanes would also have to deliver heavy ordnance against targets with great accuracy and be able to survive intense ground fire. The United States parlayed its experience into the Fairchild A-10 Thunderbolt II, a heavily armored twin-engine bomber. The Soviets also watched these developments closely before deciding that they, too, needed similar aircraft and capabilities. During World War II Russia had deployed the redoubtable Il 2 Shturmovik aircraft for identical reasons, so in 1968 the Sukhoi design bureau became tasked with developing an equivalent machine for the jet age. The bureau settled upon a design reminiscent of the Northrop YA-9, which had lost out to the A-10 in competition. The new Su 25 was an all-metal, shoulder-wing monoplane constructed around a heavily armored titanium “tub” that housed both pilot and avionics. Engines were placed in long, reinforced nacelles on either side of the fuselage, and the fuel tanks were filled with reticulated foam for protection against explosions. To assist slow-speed maneuvering, the wingtip pods split open at the ends to form air brakes. Its profile is rather pointed, but a blunt noseplate covers a laser range finder/target designator. The Su 25 is somewhat faster than the A- 10, trusting more in speed to ensure survival than a dependency on agility and heavy armor. It is nonetheless an effective tank destroyer.
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 a 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.
A series of preproduction aircraft was subsequently deployed to Afghanistan, where the planes performed useful service against guerilla forces. Western intelligence had previously identified a Soviet parallel to the Fairchild Republic A-10 Thunderbolt and dubbed it `Ram-J’ until it became better known as the Sukhoi Su-25 `Frogfoot’. A trial deployment is said to have been made as far back as 1980, but the type was most certainly used in the spring offensive. Working in conjunction with the Mi-24, this jet attack aircraft experimented with methods of co-ordinating the two disparate types, and the results will doubtless be noted for potential use in the Western theatre. They flew some 60,000 sorties, losing 23 machines in the process, but the decision was made to enter production in 1980. Since then 330 Su 25s have been built; they have received the NATO designation FROGFOOT.
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 small and robust Frogfoot can now justifiably claim to occupy a prominent position in the generation of combat aircraft that was fielded en masse in the former Soviet Union during the 1980s, and the type still forms the backbone of the Russian Air Force’s attack capabilities, albeit in considerably reduced numbers. The somewhat ugly and often underrated attack aircraft gradually but indisputably emerged in the early 1990s as Russia’s most useful and cost-effective combat jet, as its armed forces rapidly switched from their traditional cold war posture to one of internal policing, faced with growing unrest around the fringes of the former Soviet Union in the 1990s and 2000s.
The faithful Frogfoot is slated to remain in service with most of the operators at least until 2020 and near-terms sales of both new and second-hand aircraft to new operators worldwide cannot be ruled out. There are also a good many little-used Su-25s still available for sale in the former Soviet states and East Europe.
The type’s success has been proved by the developments since the early 2000s and especially by the upgrade and life-extension packages on offer, as well as the series of export sales; this eventually refuted the conclusion of some Western aerospace analysts, who maintained in the late 1990s that the first-generation Su-25 is effectively dead in its single-seat form. There is plenty of life remaining for the upgraded and refurbished Su-25SMs, while the greatly improved new-build two-seat derivative – expected to appear by 2015 at the earliest – is slated to continue into the next three decades as RuAF’s principal attack and close air support workhorse.
The basic version of the aircraft was produced at Factory 31, at Tbilisi, in the Soviet Republic of Georgia. Between 1978 and 1989, 582 single-seat Su-25s were produced in Georgia, not including aircraft produced under the Su-25K export program. This variant of the aircraft represents the backbone of the Russian Air Force’s Su-25 fleet, currently the largest in the world. The aircraft experienced a number of accidents in operational service caused by system failures attributed to salvo firing of weapons. In the wake of these incidents, use of its main armament, the 240 mm S-24 rocket, was prohibited. In its place, the FAB-500 500 kg (1,100 lb) general-purpose high-explosive bomb became the primary armament.
The basic Su-25 model was used as the basis for a commercial export variant, known as the Su-25K (Komercheskiy). This model was also built at Factory 31 in Tbilisi, Georgia. The aircraft differed from the Soviet Air Force version in certain minor details concerning internal equipment. A total of 180 Su-25K aircraft were built between 1984 and 1989.
The Su-25UB trainer (Uchebno-Boyevoy) was drawn up in 1977. The first prototype, called “T-8UB-1”, was rolled out in July 1985 and its maiden flight was carried out at the Ulan-Ude factory airfield on 12 August of that year. By the end of 1986, 25 Su-25UBs had been produced at Ulan-Ude before the twin-seater completed its State trials and officially cleared for service with the Soviet Air Force.
It was intended for training and evaluation flights of active-duty pilots, and for training pilot cadets at Soviet Air Force flying schools. The performance did not differ substantially from that of the single-seater. The navigation, attack, sighting devices and weapons-control systems of the two-seater enabled it to be used for both routine training and weapons-training missions.
From 1986 to 1989, in parallel with the construction of the main Su-25UB combat training variant, the Ulan-Ude plant produced the so-called “commercial” Su-25UBK, intended for export to countries that bought the Su-25K, and with similar modifications to that aircraft.
The Su-25UBM is a twin seat variant that can be used as an operational trainer, but also has attack capabilities, and can be used for reconnaissance, target designation and airborne control. Its first flight was on 6 December 2008 and it was certified in December 2010. It will enter operational use with the Russian Air Force later. The variant has a Phazotron NIIR Kopyo radar and Bars-2 equipment on board. Su-25UBM’s range is believed to be 1,300 km (810 mi) and it may have protection against infra-red guided missiles (IRGM), a minimal requirement on today’s battle fields where IRGMs proliferate.
The Su-25UTG (Uchebno-Trenirovochnyy s Gakom) is a variant of the Su-25UB designed to train pilots in takeoff and landing on a land-based simulated carrier deck, with a sloping ski-jump section and arrester wires. The first one flew in September 1988, and approximately 10 were produced. About half remained in Russian service after 1991; they were used on Russia’s sole aircraft carrier, Admiral Kuznetsov. This small number of aircraft were insufficient to meet the training needs of Russia’s carrier air group, so a number of Su-25UBs were converted into Su-25UTGs. These aircraft being distinguished by the alternative designation Su-25UBP (Uchebno-Boyevoy Palubny)—the adjective palubnyy meaning “deck”, indicating that these aircraft have a naval function. Approximately 10 of these aircraft are currently operational in the Russian Navy as part of the 279th Naval Aviation Regiment.
The Su-25BM (Buksirovshchik Misheney) is a target-towing variant of the Su-25 whose development began in 1986. The prototype, designated T-8BM1, successfully flew for the first time on 22 March 1990, at Tbilisi. After completion of the test phase, the aircraft was put into production.
The Su-25BM target-tower was designed to provide towed target facilities for training ground forces and naval personnel in ground-to-air or naval surface-to-air missile systems. It is powered by an R-195 engine and equipped with an RSDN-10 long-range navigation system, an analogue of the Western LORAN system.
The Su-25T (Tankovy) is a dedicated antitank version, which has been combat-tested with notable success in Chechnya. The design of the aircraft is similar to the Su-25UB. The variant was converted to one-seater, with the rear seat replaced by additional avionics. It has all-weather and night attack capability. In addition to the full arsenal of weapons of the standard Su-25, the Su-25T can employ the KAB-500Kr TV-guided bomb and the semi-active laser-guided Kh-25ML. Its enlarged nosecone houses the Shkval optical TV and aiming system with the Prichal laser rangefinder and target designator. It can also carry Vikhr laser-guided, tube-launched missiles, which is its main antitank armament. For night operations, the low-light TV Merkuriy pod system can be carried under the fuselage. Three Su-25Ts prototypes were built in 1983–86 and 8 production aircraft were built in 1990. With the introduction of a definitive Russian Air Force Su-25 upgrade programme, in the form of Stroyevoy Modernizirovannyi, the Su-25T programme was officially canceled in 2000.
A second-generation Su-25T, the Su-25TM (also designated Su-39), has been developed with improved navigation and attack systems, and better survivability. While retaining the built-in Shkval of Su-25T, it may carry Kopyo (rus. “Spear”) radar in the container under fuselage, which is used for engaging air targets (with RVV-AE/R-77 missiles) as well as ships (with Kh-31 and Kh-35 antiship missiles). The Russian Air Force has received 8 aircraft as of 2008. Some of the improved avionics systems designed for T and TM variants have been included in the Su-25SM, an interim upgrade of the operational Russian Air Force Su-25, for improved survivability and combat capability. The Su-25TM, as an all-inclusive upgrade programme has been replaced with the “affordable” Su-25SM programme.
The Su-25SM (Stroyevoy Modernizirovannyi) is an “affordable” upgrade programme for the Su-25, conceived by the Russian Air Force in 2000. The programme stems from the attempted Su-25T and Su-25TM upgrades, which were evaluated and labeled as over-sophisticated and expensive. The SM upgrade incorporates avionics enhancements and airframe refurbishment to extend the Frogfoot’s service life by up to 500 flight hours or 5 years.
The Su-25SM’s all-new PRnK-25SM “Bars” navigation/attack suite is built around the BTsVM-90 digital computer system, originally planned for the Su-25TM upgrade programme. Navigation and attack precision provided by the new suite is three times better of the baseline Su-25 and is reported to be within 15 m (49 ft) using satellite correction and 200 m (660 ft) without it.
A new KA1-1-01 Head-Up Display (HUD) was added providing, among other things, double the field of view of the original ASP-17BTs-8 electro-optical sight. Other systems and components incorporated during the upgrade include a Multi-Function Display (MFD), RSBN-85 Short Range Aid to Navigation (SHORAN), ARK-35-1 Automatic Direction Finder (ADF), A-737-01 GPS/GLONASS Receiver, Karat-B-25 Flight Data Recorder (FDR), Berkut-1 Video Recording System (VRS), Banker-2 UHF/VHF communication radio, SO-96 Transponder and a L150 “Pastel” Radar Warning Receiver (RWR).
The R-95Sh engines have been overhauled and modified with an anti-surge system installed. The system is designed to improve the resistance of the engine to ingested powders and gases during gun and rocket salvo firing.
The combination of reconditioned and new equipment, with increased automation and self-test capability has allowed for a reduction of pre- and post-flight maintenance by some 25 to 30%. Overall weight savings are around 300 kg (660 lb).
Su-25SM weapon suite has been expanded with the addition of the Vympel R-73 highly agile air-to-air missile (albeit without helmet mounted cueing and only the traditional longitudinal seeker mode) and the S-13T 130 mm rockets (carried in five-round B-13 pods) with blast-fragmentation and armour-piercing warheads. Further, the Kh-25ML and Kh-29L Weapon Employment Profiles have been significantly improved, permitting some complex missile launch scenarios to be executed, such as: firing two consecutive missiles on two different targets in a single attack pass. The GSh-30-2 autocannon (250-round magazine) has received three new reduced rate-of-fire modes: 750, 375 and 188 rounds per minute. The Su-25SM was also given new BD3-25 under-wing pylons.
The eventual procurement programme is expected to include between 100 and 130 kits, covering 60 to 70 percent of the Russian Air Force active single-seat fleet, as operated in the early 2000s. On 21 February 2012, Air Force spokesman Col. Vladimir Drik said that Russia will continue to upgrade its Su-25 attack aircraft to Su-25SM version, which has a significantly better survivability and combat effectiveness. The Russian Air Force then had over 30 Su-25SMs in service and plans to modernize about 80 Su-25s by 2020, Drik said. By March 2013, over 60 aircraft are to be upgraded. In February 2013, ten new Su-25SMs were delivered to the Air Force southern base, where operational training is being conducted. During the period 2005–2015, more than 80 aircraft were upgraded.
Since early 2014, the Guards Aviation Division Attack Aviation Regiment of the Southern Military District in the Krasnodar region received 16 advanced Su-25SMs. Nine more were delivered in 2018, eight more in early 2019 and three more in early 2020.
Since 2018, the Aerospace Forces [VKS] have been receiving Su-25SM3s, and a total of 25 aircraft have already been delivered as of June 2019. Unlike the baseline Su-25 and its incrementally upgraded variant, the Su-25SM, both of which have a rather outdated Klen-PS laser target designator in the nose, the Su-25SM3 has been upgraded with the new SOLT-25 electro-optics nose module. The SOLT-25 provides 16× zoom and features a laser range finder and target designator, thermal imager, TV channels, and the ability to track moving targets in all weather up to 8 km away. In addition, the Su-25SM3 comes with the Vitebsk-25 protection suite, which integrates a set of Zakhvat forward and rearward facing missile approach warning ultraviolet sensors, the L-150-16M Pastel radar homing and warning system, two UV-26M 50 mm chaff dispensers, and a pair of wing-mounted L-370-3S radar jamming pods. Furthermore, the Su-25SM3 has been upgraded with the new PrNK-25SM-1 Bars targeting-and-navigation system and the KSS-25 communication system with Banker-8-TM-1 antenna.
The Su-25KM (Kommercheskiy Modernizirovannyy), nicknamed “Scorpion”, is an Su-25 upgrade programme announced in early 2001 by the original manufacturer, Tbilisi Aircraft Manufacturing in Georgia, in partnership with Elbit Systems of Israel. The prototype aircraft made its maiden flight on 18 April 2001 at Tbilisi in full Georgian Air Force markings.
The aircraft uses a standard Su-25 airframe, enhanced with advanced avionics including a glass cockpit, digital map generator, helmet-mounted display, computerised weapons system, complete mission pre-plan capability, and fully redundant backup modes. Performance enhancements include a highly accurate navigation system, pinpoint weapon delivery systems, all-weather and day/night performance, NATO compatibility, state-of-the art safety and survivability features, and advanced onboard debriefing capabilities complying with international requirements. It has the ability to use Mark 82 and Mark 83 laser-guided bombs and air-to-air missiles, the short-range Vympel R-73.
The Sukhoi Su-28 (also designated Su-25UT – Uchebno-Trenirovochnyy) is an advanced basic jet trainer, built on the basis of the Su-25UB as a private initiative by the Sukhoi Design Bureau. The Su-28 is a light aircraft designed to replace the Czechoslovak Aero L-39 Albatros. Unlike the basic Su-25UB, it lacks a weapons-control system, built-in cannon, weapons hardpoints, and engine armour.
Su-25R (Razvedchik) – a tactical reconnaissance variant designed in 1978, but never built.
Su-25U3 (Uchebnyy 3-myestny) – also known as the “Russian Troika”, was a three-seat basic trainer aircraft. The project was suspended in 1991 due to lack of funding.
Su-25U (Uchebnyy) – a trainer variant of Su-25s produced in Georgia between 1996 and 1998. Three aircraft were built in total, all for the Georgian Air Force.
Su-25M1/Su-25UBM1 – Su-25 and Su-25UB exemplars slightly modernized by Ukrainian Air Force, at least nine modernized (eight single-seat and one two-seat). Upgrades include a new navigation system, enhanced survivability, more accurate weapon delivery and other minor changes.
Ge-31 is an ongoing Georgian program of Tbilisi Aircraft Manufacturing aiming at producing a renewed version of Su-25 without Russian components and parts.