T-50's tail 'sting'
The T-50's tail 'sting' houses elements of the KNIRTI/Zhukov L402 Gimalai electronic warfare self-protection suite. The fairing between the engine exhausts also accommodates three 14-round countermeasures dispensers produced by the Vympel Company of Moscow. (Sukhoi) 

On April 27, 2016 the latest example of Russia’s fifth-generation fighter, the Sukhoi Company T-50-6-2, performed its maiden flight. This test aircraft, described by the design bureau as the first of the ‘second stage’ prototypes, marked an important milestone for the programme.

However, in recent months the programme has suffered a number of setbacks, such that the prospects of its long-term success must now be in some doubt. Work to create today’s T-50 began in earnest in the late 1990s under the PAK FA (Future Air Complex of Tactical Aviation) programme. In April 2002, the government selected Sukhoi’s T-50 design for the PAK FA requirement in favour of a rival proposal from Russian Aircraft Corporation MiG. In July 2003 the Russian Ministry of Defence (MoD) awarded Sukhoi a contract for research and development work, including detailed design, construction and testing of a series of T-50 prototypes. The preliminary design of the T-50 received Russian Air Force approval in December 2004. Manufacture of the T-50 is being undertaken by the Komsomolsk-on-Amur Aircraft Plant, which is wholly owned by the Sukhoi Company. A first prototype (T-50-1) recorded the type’s maiden flight on January 29, 2010.

T-50-1
The unpainted first prototype of the PAK FA, the T-50-1, during its first flight from Komsomolsk-on-Amur, home of the aircraft’s production facility. (Sukhoi)

Initial test fleet

While prototype T-50-1 has been used to evaluate flight-handling characteristics, the subsequent T-50-2 (first flown in March 2011) features a strengthened airframe and has been used for test work at high g-loads and angles of attack. T-50-1 and T-50-2 both lack mission systems, but T-50-2 has been used to test essential aircraft systems, including the weapons bay doors and inflight-refuelling probe.

First flown in November 2011, T-50-3 is the first to feature the Tikhomirov NIIP N036 Byelka radar, albeit lacking the planned side antennas, which will be used to widen the radar’s search and tracking angles.T-50-3 also introduced certain sensors from the UOMZ/Yekaterinburg 101KS Atoll optronics suite. Minor airframe changes are also incorporated in T-50-3, including modified wingtips, compared to previous prototypes. Compared to T-50-3, the subsequent T-50-4 (first flown in December 2012) has a revised optronics suite and is likely fitted with the KNIRTI/Zhukov L402 Gimalai electronic warfare (EW) self-protection suite. Further changes to the 101KS Atoll optronics suite were incorporated in T-50-5 (first flown in October 2013). This aircraft lacks the 101KS-U ultraviolet missile approach warning system, but includes two, instead of one, 101KS-O optronics locator turrets, including a new 101KS-O/N sensor located below the forward fuselage.

T-50-4
Vortices stream from the upper surfaces of T-50-4, the fourth PAK FA prototype. This aircraft features a slightly different array of optronics sensors, and has also been used for weapons-carriage trials, including with external ordnance. (Sukhoi)

T-50-6 had been planned as the last of the ‘first stage’ flying prototypes, but was abandoned after T-50-5 suffered an accident in June 2014. Soon after landing at the experimental airfield at Zhukovsky, outside Moscow, smoke was seen emerging from T-50-5’s right engine air intake, followed by a localised fire. The aircraft was returned to Komsomolsk in Russia’s far east, and repaired using parts from the unfinished T-50-6, after which the aircraft was re-designated T-50-5R. “Essentially the PAK FA programme hasn’t seen any real progress in the last five years,” contends Justin Bronk, a research fellow specialising in combat airpower and technology at the Royal United Services Institute (RUSI) in London. “If you look at its closest competitor, the Lockheed Martin F-22A Raptor, the combination of airframe and engine didn’t take too long to develop compared to nearly a decade of systems development and bug fixing for the former.”

Mr. Bronk believes that the T-50 airframe/engine combination has still not been frozen, as evidenced by repeated measures to strengthen the wings. “The fact that they still have to patch the wings, especially for a stealth aircraft, shows that the airframe has real problems.” In effect, argues Mr. Bronk, the T-50 represents a “very heavily modified (Sukhoi Su-27/30/35 Flanker fighter) airframe,” with all the compromises in terms of radar cross-section that this brings.

T-50's tail 'sting'
The T-50’s tail ‘sting’ houses elements of the KNIRTI/Zhukov L402 Gimalai electronic warfare self-protection suite. The fairing between the engine exhausts also accommodates three 14-round countermeasures dispensers produced by the Vympel Company of Moscow. (Sukhoi)

Second Stage

In 2012 the Russian MoD placed orders for the next batch of test aircraft, for the ‘second stage’ of the programme. Although a first such test aircraft was due to fly in autumn 2015, it eventually took to the air in late April 2016. The United Aircraft Corporation, of which the Sukhoi company is a subsidiary, announced that three ‘second stage’ flying prototypes were due to be completed. The first of these to fly is the aforementioned T-50-6-2 (see above). Meanwhile, T-50-6-1 appears to refer to a ‘second stage’ static test airframe that is alternatively designated as T-50-7. Announced plans, which are almost certainly over-optimistic, called for eight pre-series aircraft to follow the prototypes. Reportedly designated T-50S, these aircraft were to be completed between 2016 and 2018. Thereafter, series production would be launched in 2019.

T-50 prototypes
Successive T-50 prototypes received slightly different equipment fits and modifications in terms of structure and aerodynamics, with the aim of finalising the design for the ‘second stage’ of the programme, which aims to field a production-representative airframe. (Sukhoi)

The PAK FA has been designed to meet the requirements of the Russian Air Force (RuAF). A Russian MoD pilot first flew a T-50 at the flight test centre in April 2013. In February 2014, the T-50-2 was first deployed to Akhtubinsk in western Russia, while T-50-3 was delivered to the centre for the first stage of state acceptance trials in December 2014. “Compared to public announcements, the PAK FA programme has suffered delays,” notes Russian aerospace observer Piotr Butowski. In fact, this is to be expected, since the dates promised by Russian officials since the very beginning of the programme have never appeared realistic. After the first flight in 2010, it was stated that state acceptance tests would commence in 2013, and deliveries of production T-50s to military units would begin in 2015. “During tests, the T-50 prototypes suffered structural cracks even flying with the g-load limited to five. For this reason, T-50-1 was under overhaul for over a year between August 2011 and September 2012 after suffering structural damage during a display at Moscow’s International Aviation and Space Salon (MAKS) exhibition in 2011. Thereafter, various strengthening additions appeared on the airframes. The structure of the production aircraft will be considerably improved.” As well as the aforementioned mishap suffered by T-50-5, there have been several incidents in which aircraft have encountered engine problems. In August 2011, T-50-2 suffered an engine compressor stall, leading to an aborted take-off. During a test flight in April 2015 a T-50’s cockpit canopy cracked.

Under published plans, the Russian MoD had hoped to declare initial operational capability and launch full-scale series production of the T-50 by the end of December 2016. The Russian National Armament Programme, which outlines the procurement priorities for the Russian military, called for 60 T-50s to be acquired by 2020. These plans will not be realised, and the Russian MoD has begun to make contingency plans in light of delays to the PAK FA programme, and perhaps broader concerns over its capabilities. In March 2015 the Russian Deputy Minister of Defence Yuri Borisov announced that a reduced number of T-50s, perhaps as few as twelve, might be purchased by 2020.

Vympel K-77M air-to-air missiles
Two tandem weapons bays between the engines are intended to carry up to four medium-range Vympel K-77M air-to-air missiles (AAMs), while two short-range Vympel K-74M2 AAMs can be carried in underwing fairings. (Sukhoi)

The T-50’s chances are hampered by the availability of Sukhoi Su-30SM and Su-35 fighters, the latest iterations of Flanker family. These two lower-cost options, already in operational service with the RuAF, provide an alternative to the T-50, at least in the short to medium term.

The Indian Connection

In the same way that Indian MoD orders allowed Sukhoi to develop the multirole Su-30MKI fighter (now in service with the Indian Air Force, which was in turn ‘Russianised’ as the Su-30SM for the RuAF), so India’s willingness to buy the T-50 will have a significant influence on its future prospects. In January 2003, Moscow and New Delhi signed a letter of intent covering the joint development of what India describes as the Fifth-Generation Fighter Aircraft (FGFA). An inter-governmental agreement followed in October 2007. A contract covering the preliminary design of the FGFA was signed in December 2010.

Sukhoi and Hindustan Aeronautics Limited (HAL) are jointly developing the fighter on the basis of the T-50. A number of changes are planned for the Indian Air Force (IAF) version, including the addition of the Tikhomirov NIIP N079 radar, in place of the N036 Byelka radar on the RuAF T-50s, and export versions of countermeasures systems and weapon management system, for example.

Like their Russian counterparts, when it comes to the FGFA, Indian defence officials have provided a mix of unrealistic timescale targets (including launch of production in India in 2018-19) and threats of reduced acquisition totals. In early 2015 the Indian chief of air staff Air Chief Marshal Arup Raha confirmed that the quantity of fighters that India will acquire is still undetermined, and will depend on financial factors.

Angad Singh, a New Delhi-based defence analyst, suggests that the most important factor facing the FGFA is the fact it is a government-to-government programme, meaning its ultimate fate rests with a political decision, and not the IAF. “The IAF has repeatedly signalled a willingness to sacrifice the FGFA if it means they can shore up fighter numbers in the short term. The hugely expensive MMRCA (Medium Multirole Combat Aircraft) programme, and now the government-to-government Dassault Aviation Rafale-F3 fighter acquisition deal have priority at the (IAF) headquarters, and multiple pronouncements by multiple officers have indicated that they are willing to push back or scale down (or both) the FGFA in favour of a more immediate fourth-generation buy.”

Mr. Singh also believes that the IAF is not happy with the current or even promised capabilities of the FGFA. “They would never admit it in public, but the Su-30MKI fleet is a huge headache from a reliability perspective, with the engines a particular concern.”

As its power plant, the T-50 currently employs two Saturn/Rybinsk AL-41F1thrust-vectoring turbofan engines. Despite its new name, as Mr. Singh points out, the AL-41F1 engine is essentially an upgrade of the AL-31F as used in the Su-27/Su-30 fighters, albeit with improvements including a larger-diameter fan, new high- and low-pressure turbines, an upgraded combustion chamber and a new Full-Authority Digital Engine Control (FADEC) system, by which the engine is controlled in an entirely computerised manner. According to Mr. Butowski, AL-41F1 engines will power T-50 fighters “at least until 2020”. After this date, they are expected to be fitted with the Izdeliye-30 turbofan, a completely new design.

For now, the T-50 is powered by a pair of Saturn/RybinskAL-41F (Izdeliye 117) thrust-vectoring turbofans. This engine is an evolution of the 117S that has already been proven on the Su-35S fighter. Around 2020 the all-new Izdeliye 30 engine should be ready for the T-50. (Sukhoi)

Mr. Singh continues, “as an operator of multiple Russian fighter types, the IAF is familiar with Russian technological limitations … There is a lack of confidence that the Izdeliye30 engines will be delivered on time and on spec.” Indian confidence in the T-50 is also eroded by Russian reluctance to share test data and take part in prototype evaluation. “IAF officers are incredibly unhappy that the Russians are not letting them get their hands on even the T-50 prototypes. An Indian delegation was present when T-50-5 caught fire, and reportedly the Russians wouldn’t tell them what had gone wrong and wouldn’t let them near the aircraft once the fire had been put out. That’s the sort of behaviour that upsets prospective customers.”

Compounding Indian unease is the RuAF decision to induct only a small batch of series-production T-50s before committing to a full-scale production. Aside from India, however, export prospects for the T-50 are somewhat limited. “The classic market for top-end Russian equipment is the People’s Republic of China (PRC),” Mr. Bronk notes. The PRC, however, has taken a different path to developing its own advanced fighters. “Having stolen so much data, the PRC is in a better position to develop indigenous fifth-generation fighters. In terms of countries to willing to buy fighters from Russia, these tend to need to bolster their air defences quickly, and above all cheaply.” While there have been claims that the T-50’s unit cost will be “comparable to the latest Flanker series, (the Su-35),” Mr. Bronk considers that this is clearly unrealistic. Furthermore, with the Su-35 available and in quantity production, this option represents a very good deal in itself. “For $65 million, very little comes close to the Su-35,” he adds.

While the PRC develops its own comparable fifth-generation fighters, India was hopeful that joining Russia to co-develop the FGFA would provide a head start for its own aerospace industry. “So far, there is little clarity on Indian industrial participation, beyond the fact that HAL is to be the lead integrator for the Indian production effort,” says Mr. Singh. “It’s early to be talking about industrial participation anyway, since everything seems to have gone sideways. The Russians have done most, if not all the development work. If India stumps up the $6 billion the Russians were asking for, they will essentially be paying for instructions on how to build a fighter whose development is all but complete. I think even the Russians have recognised this and revised their ask downwards to around $3.7 billion.”

The FGFA programme is also being run against a backdrop of severe budgetary constraint within the Indian MoD. Current priorities include regeneration of the Indian Navy’s submarine fleet, and mechanisation and modernisation of the Indian Army. “The IAF needs to address a critical fighter shortfall,” Mr. Singh adds. “By virtue of being of being further down the list in chronological terms, the FGFA simply isn’t getting a lot of attention from the IAF, the MoD and the administration at large.”

Even if the T-50 fails to make headway, Russia may yet benefit from its experience in developing a fifth-generation combat aircraft. Mr. Bronk envisages a situation in which Russia may export its expertise gained in the programme to other countries working to develop advanced fighters. Outside of India, these currently include the PRC, the Republic of Korea and Turkey.

Concluding his analysis of the prospects of the FGFA in India, Mr. Singh told Armada, “I personally don’t rate the FGFA’s chances of success highly. It’s expensive, and therefore will give the MoD pause, while the IAF simply does not want it in its current or proposed forms. But in the world of politics and diplomacy, anything can change. If it comes down to giving the Russians a gift after ignoring them in favour of the Americans and Europeans in so many military purchases over the past decade or so, $4 billion might prove to be very good value after all.”

Currently, it is clear that the FGFA programme is at a standstill, and much of the future success of the T-50 hangs on this factor. “Nothing is certain now that the programme schedule is not being adhered to,” says Mr. Singh. “The two countries were supposed to have signed the R and D contract immediately after the conclusion of the preliminary design contract. But when the technical issues and problems with work share emerged in the R and D stage, the contract stalled and has been stalled ever since.”

For Mr. Bronk, the T-50 is limited by the fact that its design represents a “halfway house,” in which compromises are made in terms of a low radar cross section (RCS) in order to maximise manoeuvrability. “With the T-50, Sukhoi is pursuing a weird hybrid in terms of technology doctrine. A lot of sacrifices have been made in terms of very low observable characteristics in order to enhance manoeuvrability. There has been little interest shown in terms of situational awareness (the aircraft’s sensor and communications package) or all-aspect stealth.” On the other hand, while analysts often highlight the T-50’s engine air intakes as a low RCS weak point, this might not be an issue once the planned ‘radar blockers’ are installed. These are air intakes which are designed in such a fashion as to shield the engines’ spinning fan blades from radar detection. However, if its low RCS characteristics are truly compromised, then why should the RuAF, or indeed potential export customers, choose the T-50 over the tried and tested, and cheaper, Su-30 and Su-35?

trio of T-50s
A trio of T-50s reveals details of the aircraft’s internal weapons bays and engine configuration. While early aircraft had intakes with unshielded engines, these have apparently now been fitted with radar blockers to reduce reflections to hostile radars. (Sukhoi)

by Thomas Newdick