Fighting Workhorse

Alexander Mladenov looks at the Su-25 Frogfoot in Russian service and the progress of its upgrade programmes

MILITARY

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Plans for upgrading the Su-25UB Frogfoot (seen here) to the enhanced Su-25UBM2 standard have been delayed and the first production-standard machines upgraded to this standard are expected no earlier than 2019.
Andrey Zinchuk

Ugly, sturdy and able to deliver heavy bomb loads, the Sukhoi Su-25 Frogfoot made its maiden flight in February 1975 and was fielded in frontline service in the then Soviet Union in 1980. At the time, it had the distinction of being the first Soviet (and later Russian) mass-produced combat jet purposely designed for the close air support (CAS) role at low level.

It represented a simple, effective and survivable attack workhorse, purposely designed to fly multiple short-range battlefield CAS missions. In the 1980s and 1990s, the Su-25 proved itself as a powerful and cost-effective weapon doing its rather dangerous job in many local conflicts, and it continued to soldier on with most operators well into the new century.

The Frogfoot’s large-scale production run between 1978 and the early 1990s accounted for 582 Su-25s, 50 slightly improved Su- 25BMs and downgraded 182 Su-25Ks for export customers built at the TAM plant in Tbilisi (now in the independent state of Georgia). In addition, no fewer than 140 two-seat Su-25UBs and Su-25UBKs were built at the Ulan-Ude Aviation Plant (U-UAP) in Russia. These were augmented in the 2000s and the early 2010s by eight two-seat Su-25Us (using incomplete Su-25T airframes) and 37 Su-25Ks and Su-25KMs built at TAM.

The combat-proven Frogfoot is set to remain the backbone of the Russian Air and Space Force’s (RuASF’s) attack aviation sub-branch until at least the early 2030s. The robust and dependable type has been a subject of several life-extension and upgrade efforts in Russian service to deal with a multitude of obsolescence issues. The latest Frogfoot upgrade standard for the RuASF, dubbed Su-25SM3, has significantly increased combat potential thanks to the integration of an all-new day/night targeting sensor system and a modern self-protection suite.

The type’s service life has been extended to 4,000 hours and 40 years, and there are plans for this to be further extended to 5,000 flight hours and 50 years. Time between overhauls is 10 to 15 years and 800 to 1,000 flight hours.

Affordable to buy and operate, the Frogfoot still enjoys a worldwide proliferation and is currently in the inventory of 17 export operators. A proportion of them have implemented, or are at least are planning to launch, upgrade programmes of various depths centred mainly on enhancing the aircraft’s navigation and weapons delivery performance.

Su-25SM Upgrade

The Su-25SM (Stroyevoy, Modernizirovannyi – Line Upgrade) is the first upgrade standard adopted by the RuASF. It was conceived in its original guise in the late 1990s and early 2000s as a relatively low-cost venture to bring the rapidly ageing and analogue Frogfoot into the modern digital age by using mostly off-the-shelf components while making the cockpit more ergonomic and simplified.

The SM features the all-new PRnK-25SM Bars navigation/attack suite built around the BTsVM-90 digital computer, borrowed from the Su-25TM specialised anti-tank aircraft, which was built in prototype form only and tested in the late 1990s and early 2000s, but never launched in mass production. In the SM upgrade, most of the analogue components of the Su-25’s original KN- 23-1 navigation/attack suite were replaced by new digital equipment, but the Klen-PS laser rangefinder/target designator remained unchanged.

Navigation precision provided by the new PrNK-25SM suite was said to be within 15m (46ft) using satellite correction and 200m (660ft) without it, an improvement made possible thanks to the integration of the A-737-01 GPS/GLONASS satellite navigation receiver. The high precision in turn allows the Su-25SM to undertake non-visual bombing runs in poor weather and at night at low and medium level against fixed targets with known positions using unguided bombs from level flight.

A new head-up display (HUD), the KAI-1- 01, was also added, providing a field of view double that of the old ASP-17BTs-8 electrooptical sight. Other components added during the upgrade included a multifunction cockpit display (used to display a digital map and flight, navigation and tactical information) while the type’s R-95Sh engines received an anti-surge system to improve resistance to ingestion of powder gases while firing the gun and rockets in salvoes.

The combination of the new HUD, weapons computer and navigation/attack system’s digital components promised significantly increased accuracy when employing unguided ordnance with visual aiming; the overall improvement is advertised as being between two and three times. The Su-25SM’s air-to-air capability was expanded as well, thanks to the integration of the R-73 highly agile short-range air-to-air missile, albeit without helmetmounted cueing.

The newly added ground attack weapons included the 130mm S-13T rockets (fired from five-round B-13 packs) with blastfragmentation and armour-piercing warheads. In addition, the Su-25SM was made capable of launching the Kh-25ML and Kh-29L laser-guided missiles while in horizontal flight (the non-upgraded versions can do this in shallow dive only) and fire two missiles at two different targets in a single firing pass.

The 30mm GSh-30-2 cannon in the VPU- 17A gun mount with 250 rounds with a 3,000 rounds per minute (rpm) rate-of-fire received three new reduced rate-of-fire modes to increase the number of firing passes, with 750rpm, 375rpm and 188rpm, to allow for 20, 40 and 80 seconds of total firing time respectively.

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1 The Su-25’s cockpit (seen here in an export-standard K form), although considered old-fashioned, is described as roomy and ergonomically well-designed, while the upgraded Su-25SM has a much more simplified and ergonomic cockpit. The pilot sits in a full armour bath made from welded titanium plates.
Alexander Mladenov
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2 Currently the RuAF has between 160 and 170 Su-25s in active service or undergoing deep maintenance and upgrade.
Andrey Zinchuk
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3 After the Su-25’s withdrawal from use with the 209th UAB at Borisoglebsk in 2014 the squadron’s aircraft were re-distributed to the front-line attack squadrons flying the type.
Andery Zinchuk

However, the upgrade programme suffered from considerable delays from the very beginning. Eventually, the first Su-25SM prototype undertook its maiden flight on March 5, 2002 and its test and evaluation programme was completed in 2006. The first batch of six upgraded production-standard Su-25SMs were officially handed over to the Russian military on December 28, 2006.

The RuASF received 84 Su-25SMs between 2006 and 2014 (this figure including four prototypes and pattern aircraft, two of which were re-upgraded later to the SM3 standard), which equipped one conversion training/research and seven front-line squadrons. By early 2017, six upgraded Frogfoots were lost. One was shot down and two were written off after heavy damage in the August 2008 war in Southern Ossetia, and three more have been lost in peacetime accidents.

The aircraft wearing the newly assigned airframe identification numbers SM-5 to SM-43 were production upgrades as per the initial standard, known as the SM1, delivered between 2006 and 2010. The slightly improved SM2 standard followed, involving aircraft SM-44 to SM-79, which were taken on strength by the RuASF between 2011 and 2013. In late 2014, the RuAF took delivery of the last five aircraft upgraded to this standard, serials SM-80 to SM-84. Unit price for this batch was RUB 143.5 million.

Despite all the upgrades to the navigation performance and the weapons delivery capabilities, the Su-25SM and its successor Su-25SM3 remain 1970s-vintage airframes, powered by fuel-thirsty 1950s-vintage turbojets and are fully manual aircraft, lacking autopilot and pressurised cockpits.

Su-25SM3: Definitive Upgrade Standard

The Su-35SM3 is the most sophisticated upgrade standard for the Russian Frogfoot fleet, and is slated to be fielded in frontline service in the first half of 2017. It was designed following the bitter lessons learned during the war in Southern Ossetia in August 2008, in which both the Su-25SM and non-upgraded Su-25s proved too vulnerable to infrared-guided man-portable air defence systems when performing lowlevel attack runs with rockets and freefall bombs. The SM3 standard aimed mainly to strengthen the Frogfoot’s self-protection and night-operating capabilities. It comes together with new hardware and software capability to facilitate the use of new highly lethal guided weapons types. It boasts an encrypted datalink (enabled by the new KSS-25 communication suite) for use in CAS scenarios for exchanging targeting information with forward air controllers and other aircraft in the air. The datalink also allows integration of the Su-25SM3 into the RuASF’s overall command-and-control system.

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4 Frontline attack squadrons equipped with the Su-25 have an active fleet of 12 single-seat plus two to three two-seat aircraft; the attack regiments consist of two squadrons. This example is from the 368th ShAP.
Andrey Zinchuk
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5 This pair of Su-25s – one upgraded and one nonupgraded machine - belong to the 960th ShAP based at Primirsko-Akhtarsk in the Southern Military District.
Andrey Zinchuk

The Su-25SM3 is equipped with the PrNK-25SM-1 navigation/attack suite and the SUO-39M fire control system. In addition to the Kh-25ML, Kh-29L and S-25L/LD laser-guided missiles, the latest Frogfoot derivative can deploy the Kh-29T, Kh-29TD and Kh-29TE TV-guided missile and KAB- 500Kr TV-guided bomb, as well as KAB- 500S GPS-guided bombs. The Kh-58USh anti-radar missile was also integrated, using targeting information derived from the Pastel RHWAS incorporated in the Vitebsk-25 self-protection suite. It retains nuclear bomb delivery capability, represented by two SpAB freefall nuclear bombs.

The cockpit is equipped with the new BI HUD, a MFTsI-0332M multifunction colour display augmented by another smaller display beneath the HUD, a BSKI digital map module and the PPA-S/V-06 satellite navigation system with GPS and GLONASS receiving capability and also featuring differential updating.

SU-25SM3 CHARACTERISTICS

Wingspan: 14.36m (47ft 1in)

Length overall: 15.53m (50ft 4in)

Height overall: 4.80m (15ft 9in)

Wing area: 34.7m2 (362.75ft2)

Max take-off weight: 17,530kg (38,636lb)

Normal take-off weight: 14,530kg (32,034lb)

Internal fuel: 3,000kg (6,614lb)

External fuel: 2,464kg (5,618lb)

Max speed at sea level: 512kts (950km/h)

Max speed clean: 540kts (1,000km/h)

Max attack speed: 372kts (690km/h)

Landing speed: 110kts (205km/h)

Take-off speed: 119kts (220km/h)

Service ceiling: 23,000ft (7,000m)

Rate of climb: 60m/s (197ft/s)

Range (with a 2,000kg bomb load and max internal fuel): 510km (275nm)

Ferry range with four external tanks: 1,900km (1,025nm)

Take-off run: 500m (1,640ft)

Landing roll with brake chute: 700m (2,296ft)

G limit (with 1,000kg bomb load): +6.2g

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1 The RuASF intends to keep its existing fleet of Su-25SMs in active service until the early 2030s as the Frogfoots have a lot of unused life in them and the type is subject to a rolling life extension effort.
Andrey Zinchuk

The SOLT-25 IR/TV/laser targeting and designation system, developed by the Krasnogorsk Mechanical Plant, is one of the main new systems integrated on the Su-25SM and is the backbone of its targeting suite. Installed in the nose, it features the same shape and weight as the old Klen-PS laser rangefinder/target designator. The new system’s TV channel with a 16x zoom, is advertised as capable of operating in target detection and tracking modes at up to 8km (4.6nm), with subsequent tracking of the target selected by the pilot for engagement with laser-guided missiles or TV-guided missiles or bombs.

Enhanced Self-Protection

The Vitebsk-25 integrated self-protection suite, developed by Samara-based NII Ekran, incorporates the L-150-16M Pastel radar warning and homing system, ultraviolet (UV) missile approach warning sensors, UV-26M countermeasure dispensers (which use a mix of 26mm and 50mm chaff and flares) and the L-370-3S dual-pod radar jammer system accommodated on the outermost wing hardpoints, covering the frequency band from 7 to 10GHz.

UPGRADED SU-25UBM

The upgraded Su-25 two-seater, using exactly the same avionics as that integrated on the Su-25SM and designated as the Su-25UBM, has suffered from a notably protracted development and is not yet fielded in service. The first flight of the two-seat prototype was reported in December 2010 and the sole Su-25UBM, wearing the serial 21, is reported to have completed the test and evaluation effort in December 2011. In the spring of 2014, however, it was seen at the 121st ARP in Kubinka in disassembled form, undergoing some unspecified modifications. Later, it was revealed that it was reupgraded to the enhanced Su-25UBM2 standard, featuring mission equipment borrowed from the SM3 single-seat upgrade, including the Vitebsk-25 self-protection suite and the SOLT-25 targeting system.

In this new guise, it was slated to commence a flight-test programme by October 2015, with completion expected by 2017, comprising as many as 150 flights. However, the flight testing and evaluation at the RuASF’s 929th State Flight Test Centre was delayed by seven months and didn’t begin until mid-2016; it is expected to be completed by late 2018 at the earliest. As of March 2017, no information had been released about the progress.

There are no plans to produce new two-seat Su-25s at the U-UAP, contrary to the information released in 2011 and 2012. The Su-25UBM2 upgrade, combined with a structural overhaul and life extension works, will involve an undisclosed number of the existing RuASF Su-25UBs produced in the late 1980s and early 1990s. The first orders for the Su-25UBM2 upgrade are expected to be placed by the Russian MoD in late 2017 at the earliest, with delivery expected at the end of 2018.

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2 A Su-25SM belonging to the 368th ShAP at Budyonnovsk seen during its landing roll with twin-dome parachute deployed.
Andrey Zinchuk
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3 The newly-installed avionics of the Su- 25SM has increased automation and self-test capability, making possible a reduction in the aircraft’s pre- and post-flight servicing of some 25 to 30%.
Alexander Mladenov

Missile approach warning is provided by the Zakhvat electro-optical system. Its UV sensors cover the lower hemisphere, with a front sensor under the nose responsible for head-on-coverage and two rearward/ sideward-looking sensors installed in a V-shaped assembly under the tail. Due to the lack of space, it proved impossible for the Vitebsk-25 to also incorporate directional infrared jammers such as those used by the Ka-52 attack helicopter.

The Vitebsk-25 features two underbelly UV-26M countermeasure dispensers for releasing 28 chaff or flare 50mm cartridges (firing downwards) in addition to 26mm upward-firing dispensers installed on the engine nacelles and next for the tail with a total capacity of 256 rounds. According to the Su-25’s designer general Vladimir Babak, the increased number of flares of two different sizes enables the Vitebsk-25 to counter up to six infrared-guided missiles approaching the aircraft simultaneously. The system offers a variety of flare pumping sequences, selected automatically depending on the arrival direction of the missiles.

The KSS-25 is the new communication system featuring a secure datalink capability, enabling exchange of tactical information with ground command and control facilities and other aircraft.

The first Su-25SM prototype, Su- 25SM3-01, reworked from Su-25SM-04 prototype (c/n 10095) is reported to have begun flight testing in 2011, and later on it was joined by a second example. However, the testing and evaluation effort proved to be a protracted undertaking due to the immature status of the new equipment. This was especially true regarding the SOLT-25. Su-25SM3-01 is being used as the pattern aircraft for the production upgrade.

The Russian Ministry of Defence (MoD) awarded its first order for five Su-25SMs to the 121 ARZ in December 2015, even before the completion of the test effort, following an electronic tender. One of these aircraft (the fourth aircraft in the batch, wearing the new identification number Su-25SM3-06 and serialled Red 50) was observed in post-upgrade test flights at Kubinka airfield in October 2016; the entire batch was to be ready for delivery in December 2016. Unit price was set at RUB 350.2 million, excluding the price of the radar countermeasures pods of the L-370-3S system. It is believed the first Su-25SM3 batch utilised existing Su-25SM airframes from the initial production run in the mid-2000s, which were also required to undergo another overhaul and life extension, making it good for at least ten years of service.

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4 This Su-25BM, serialled 73, is the first Frogfoot upgraded with the Gefest i T SVP-24-25 digital navigation/attack system operated by the Lipetsk-based combat training and aircrew conversion centre.
Andrey Zinchuk
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FROGFOOTS IN THE SYRIAN WAR

The Russian air component covertly deployed to Hmeimim/Latakya Air Base in Syria in September 2015 comprised an attack force of ten Su-25SMs and two Su-25UBs belonging to the 960th ShAP based at Primorsko-Akhtarsk in the Southern Military District. These aircraft flew combat missions between October 2015 and mid-March 2016. A total of 3,500 combat sorties were flown in Syria, with each of the Su-25SMs racking up to 300 sorties and 300 flight hours. The two-seat aircraft were much less used, with 60 to 80 hours, mainly spent for refresher training, area familiarisation sorties and weather checks.

The principal use of Su-25SMs in Syria comprised bombing in level flight from 11,500 to 13,500ft (3,500 to 4,100m) altitude. The Frogfoots used 100kg, 250kg and 500kg freefall bombs and the RBK-series of cluster bombs. In most of the sorties munitions were dropped without visual contact with the targets, as the upgraded Frogfoots used the bombing method from level flight where the targeting solution is calculated by the aircraft’s own navigation system when delivering a strike against targets with known positions. The pilot is tasked to fly the aircraft and follow cues to bring it to the calculated bomb drop point. At a later stage, the Su-25SMs began flying bombing missions against targets of opportunity, with an accurate position provided by forward air controllers in the field, who were included in the reconnaissance teams assigned to Russian special operations forces operating in enemy-held territory. These teams often used unmanned air vehicles to pinpoint targets and then perform after-strike battle damage assessment.

Bombing sorties were flown with formations of two, four and even six aircraft. During the days of the most intense combat operations each aircraft flew up to ten sorties, with a turn time before the next sortie of only 15 minutes, including ammunition loading, refuelling and visual inspection for damage and leaks. In general, the upgraded Frogfoot proved very reliable and dependable, with no significant failures reported during the Syrian deployment.

According to an article published in the Russian magazine M-Hobbi in March 2017, the Su-25SMs also flew so-called free-hunting combat sorties in predesignated kill boxes to attack targets of opportunity such as moving armed vehicles or fuel tankers in territories held by anti- Assad or Islamic State militants. In these missions, the upgraded Frogfoots were armed with two 20-round B8-M1 rocket packs for firing 80mm S-8 rockets and four external fuel tanks enabling a mission endurance of up to two hours.

It is difficult to get reliable information beyond the usual propaganda on the real accuracy and therefore effectiveness of the Su-25SM’s strikes using dumb bombs dropped from medium altitude that, by definition, could not be accurate, due to the multitude of factors affecting the bomb’s flightpath during its freefall. The Su-25SM has an advertised 33 to 50ft (10 to 15m) circular error probable, but this claim cannot be confirmed by independent sources. In most of the sorties, according to M-Hobby, the Su-25SMs dropped one bomb against each target. The most commonly used munition in Syria was the OFAB-250-270 250kg (550lb) high-drag free-fall fragmentation/high-explosive bomb.

The navigation bombing capability made the Su-25SM useful day and night, in both clear and bad weather. Its combat effectiveness depended mainly on the quality of the targeting information received prior to take-off or handed over by forward air controllers when loitering in a target area. In January 2017, four Frogfootd, comprising three Su-25SMs and one Su-25UB, were again deployed to Hmeimim/Latakya Air Base, but no information has been released on the nature of the operations.

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A Su-25SM of the 960th ShAP taking off from Hmeimim Air Base in Syria with a weapon payload of four OFAB-250-270 freefall bombs.
Russian MoD

As of March 2017, there was no news on the formal delivery of the first Su-25SM3s to a RuASF frontline unit for so-called experimental operation, apparently due to the delayed completion of the joint state testing effort undertaken by the RuASF’s 929nd Flight Test Institute at Akhtubinsk.

The second order, involving nine more Su- 25SM3s, priced at RUB 3.341billion, translating to unit price of RUB 371 million, was placed by the Russian MoD, again via an electronic tender awarded to the 121 ARZ, in mid-2016, with a delivery deadline set out for November 2017.

The Russian MoD announced that it intends to procure up to 45 Su-25SM3s until 2020. A proportion of these will be re-upgraded Su- 25SMs and the rest will be standard Su-25s and Su-25BMs.

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1 A Su-25SM from the 368th ShAP demonstrates the Frogfoot’s remarkable combat survivability. This aircraft was hit by a man-portable air defence system during the August 2008 South Ossetia war between Russia and Georgia. The aircraft remained flyable and managed to return to base, but was judged as beyond economical repair.
via Alexander Mladenov
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2 A look at the final assembly hall of the TAM plant in Tbilisi, Georgia. This image dating from the late 2000s shows newly-built single- and two-seat airframes, most likely intended for delivery to Azerbaijan.
TAM via Alexander Mladenov
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3 The first-generation Frogfoot is likely to serve with most of its current operators well beyond 2020, while in Russia it could remain in use until the early 2030s.
Andrey Zinchuk
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4 This is the pattern aircraft for the Su- 25SM3 upgrade, (c/n 10095, re-worked from the Su-25SM-4 prototoype), pictured in the late 2000s with the new radar jamming system of the Vitebsk-25 self-protection in two pods on the outermost wing hardpoints, 250kg freefall bombs and B13 pods for firing 122mm rockets. The missile approach warning sensors were not installed at that time.
Via Alexander Mladenov

SVP-24-25 Upgrade

Meanwhile, at least two other Russian aviation repair plants – 322 ARZ at Vozdvizhenka and YARZ at Yevpatoria – continue to be busy with the overhaul and life extension of non-upgraded Su-25s for the RuASF. As a result, it is expected that by 2020 the attack sub-branch of RuASF Frontal Aviation will operate a fleet of some 100 to 110 Su-25SMs and Su-25SM3s in addition to a few upgraded two-seat Su-25UBM2s and 50 Su-25s and Su-25UBs.

Most, if not all, of these aircraft are slated for upgrade to a different and much cheaper standard for improved navigation and weapons delivery performance. The fleet of life-extended upgraded and non-upgraded Su-25s could be good for at least 10 to 15 years of use and the non-upgraded ones are going to receive the new SVP-24-25 navigation/attack subsystem, developed by the Zhukovsky-based company Gefest i T. This is a derivative of the combatproven system installed on the upgraded Su-24M, Su-33 and Tu-22M3.

The SVP-24-25 package is built around a new SV-24 digital mission computer integrated with a combined GPS/GLONASS satellite navigation receiver, new HUD, new hardware interface units and proprietary software for processing navigation data received from different sources, combined with a highly accurate digital map and terrain elevation model. This system provides precise positional information, reportedly within 100 to 160ft (30 to 50m), regardless of the mission duration. As a result, the SVP-24-25 could drastically improve the accuracy of delivering unguided ordnance. The system is advertised as being able to achieve a hit with a circular error probability of 33 to 50ft (5 to 10m) when delivering unguided bombs in level flight or during three-dimensional manoeuvring, which is useful for avoiding anti-aircraft fire when operating at low level. When attacking a target with a known position that is invisible to the pilot, the run-in can be performed using highly accurate positional data derived from the electronic map alone.

The SVP-24-25 software also facilitates rapid re-targeting in flight with data for newly assigned targets received by a secure datalink from a ground-based commandand- control centre and presented as a set of symbols overlaid on the electronic map shown on a display in the cockpit.

A prototype Su-25BM, upgraded with the SVP-24-25 navigation/attack suite and serialled Red 73, was noticed in flight test at the Lipetsk combat training centre in July 2015. At this time, Gefest i T director general Alexander Panin claimed that the RuASF decision for a fleet-wide introduction of the SVP-24-25 is planned to take place upon completion of the system’s test effort in late 2015. However, it turned out the completion of the testing was delayed until early 2016. The RuASF’s 929nd State Flight Test Centre took over for the so-called special flight testing and evaluation of the upgrade, further delaying its completion. As of March 2017, no announcement has been made for the completion of the flight testing of the SVP- 24-25 upgrade or any other progress of the Gefest i T project.