Sukhoi’s fifth-generation fighter

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Sukhoi’s fifth-generation fighter
Tuesday November 2, 2010 23:23 MSK / Vladimir Karnozov / Russian Aviation

With the maiden flight, on 29 January this year, of the T50-1, a first operable prototype of Sukhoi’s PAKFA (Russian acronym for Future Complex of Frontal Aviation), Russia has become the second nation after US to have flown a fifth-generation fighter.

So far, USAAF has been world’s only air force to operate fifth generation fighters: the F-22A Raptor became operational in 2005.
A lot of hope is put in the new Sukhoi aircraft.

Firstly, it must be the major type in service with the Russian air force’s Frontal Aviation units: the service has a requirement for 250-300 new-generation tactical fighters. Secondly, it must provide a base for creation of a joint Indo-Russian joint product. New Delhi refers to it as the Fifth-Generation Fighter Aircraft (FGFA). The Indian air force is looking for 200-250 such aircraft. Thirdly, it should bolster Russian exports. Although PAKFA itself may not sell in large numbers in the open market, it must support a good image of the Russian aeronautics engineering in the eyes of potential and traditional buyers of Russian equipment. The Indo-Russian FGFA is likely to set standards for PAKFA’s exportable versions. A number of smaller countries tend to buy from Russia what Moscow has previously sold to India, in a hope that this would facilitate spare parts and maintenance issues.
Fifth-Generation Fighter Aircraft

The very designation “Fifth-Generation Fighter Aircraft” (FGFA) was invented by New Delhi, and is used today to point at the PAKFA’s Indian air force version. Moscow and New Delhi have been talking about joining forces on this project for over five years. Anatoly Isaikin, general director with Russia’s state arms vendor, thus summarized the whole story: “Russia has so far received proposals to cooperate on joint development of fifth-generation weapons systems from India only. The Indian initiative was met positively. Now, Russia and India are working together on the Fifth-Generation Fighter Aircraft and the Multirole Transport Aircraft.” In an interview with the Russian media, Raj Kumar Singh, Secretary, defense production, ministry of defense, government of India, presented this view on the subject: “The FGFA is a joint development project in which we will see Indian and Russian designers and engineers working side-by-side from beginning until its completion. The FGFA will be a joint product whose intellectual property rights will be held fully and equally by both parties”.

Although it had been widely known that construction of PAKFA prototypes started sometime ago (in 2007, to be precise), the maiden flight on 29 January 2010 drew close attention of many people round the world. The event was widely featured in the mass media. For many people the pictures shown on TV and published in the magazines brought a big revelation, since the PAKFA had been much featured before, but its actual outward appearance was made public only now.

The first flight originated from the aerodrome of the Komsomolsk-upon-Amur Aircraft Production Association (KnAAPO), where the airplane was assembled, and lasted 47 minutes. Upon landing, Sukhoi test-pilot Sergei Bogdan reported that the airplane handled well and was a pleasure to fly. Congratulating Sukhoi and KnAAPO on this occasion, Russian PM Vladimir Putin said a batch of such aircraft will go to the Russian air force’s Center for Combat Usage and Personnel Retraining in Lipetsk in 2013. He further said that deliveries to the RusAF line units shall commence in 2015.

So far there have been two PAKFA public flight performances, on 17 June and 31 August, both at Ramenskoye aerodrome near Moscow. On the first occasion the airplane with number 51 on its sides was demonstrated to Vladimir Putin. The Russian PM paid a visit to LII, the Flight Test and Research Institute named after Mikhail Gromov. He came in company of a hundred carefully selected Russian journalists. This happened after the airplane changed its base from KnAAPO’s aerodrome to that of LII in Zhukovsky near Moscow (that happened in early April).

Speaking to journalist on 17 June, Putin said a total of about 30 billion Roubles (which exchanges for roughly Euro 1 billion) was already spent on the project. He added that “a similar amount” is to be added to the top of that. Putin further said a series aircraft will cost Moscow 2.5 - 3 times less than Washington paid for a series F-22A Raptor. “Taking account of a better quality - and we will, certainly, try to get that better quality – our product shall give us a serious competitive advantage”, the Russian PM stressed. Over two thousand more flights shall be performed on PAKFA prototypes in frame of the type’s trials aimed at producing “a modern machine having no analogues abroad”, he added.
Vladimir Putin: “Taking account of a better quality - and we will, certainly, try to get that better quality – our product shall give us a serious competitive advantage

High-ranking military leaders accompanying the PM on his visit to LII collaborated further. The Russian MoD considers placing an initial order for “over fifty” PAKFA aircraft as part of the State Weapons Program 2020. This production series shall be preceded by a pre-production batch comprising six to ten deliverable aircraft [for RusAF special establishments].

On the second occasion the airplane conducted a flight demonstration for a delegation of Indian defense ministry and industry officials. The Indians inspected the prototype and received a program update. Many of the guests were members in the subgroup on aviation of the Indo-Russian interstate committee for military-technical cooperation. Performed over Ramenskoye aerodrome, the 10-minute demo flight was made in support of talks over the nations’ proposed bilateral development of a next generation combat jet. The aircraft was flown by Sergei Bogdan. He made everything he could to best demonstrate high performance of the airplane, including low-speed passes and high-angle-of-attack maneuvers. Remarkably, Bogdan performed before the Indians for ten minutes, compared to merely three minutes on the previous occasion.
Super maneuverability

Although it was only 16th flight for the new airplane, it showed an astonishing performance, maneuvering as good as a Su-30. Those lucky few who watched Sergei Bogdan’s performance over Ramenskoye on 31 August, witnessed T50-1’s ability to make “air tricks” which Sukhoi calls “super maneuverability”. According to Sukhoi general director Mikhail Pogosyan, the aircraft attained a 25-degree angle of attack. All this leaves little doubt about the ability of the new Sukhoi design’s to win hearts of the frequent show visitors.

Admittedly, the T50-1 is very far from what the Russian air force wants to see in a production PAKFA. Pogosyan admitted that the first prototype does not carry a whole set of avionics and systems. It does not have a radar suite, for instance. This is because the Side 51 is intended for proving aerodynamics layout, flight controls and engine tests. Second and third operable machines, to be completed by the end of this year, shall come equipped with a comprehensive set of onboard equipment.

Tikhomirov’s NIIP develops a radar suite for the new aircraft. It will include an active electronically scanned array (AESA). At MAKS’2009 air show Tikhomirov’s NIIP exhibited an experimental AESA based on GaAS nanostructures. Reportedly, a functioning radar set will equip a third operable PAKFA prototype. The radar suite will also include a number of additional antennas to operate in L- and X- wavebands. Together, they are meant to provide 360-degree radar coverage.

On an occasion of Vladimir Putin visiting Sukhoi design house in early March, journalists that accompanied him were shown an engineering stand of an advanced fighter cockpit, believed to be that of the PAKFA. It featured a new ejection seat from NPP Zvezda, a rather high central stick (much in Russian style) and a wide-angle HUD. Pilot’s information field is complemented by two large LCDs and a smaller LCD to the right of the HUD’s body.

It should be noted that Russia commenced work on fifth generation fighter technologies well before the PAKFA appeared on the drawing board. The beginning of it can be traced to as early as 1981, when, after some preliminary scientific studies, the Soviet Union launched a special technology development program. When sufficient knowledge was amassed, the Kremlin challenged Mikoyan with building a technology demonstrator. This effort was in frame of a bigger program on creation of the Multirole Fighter Aircraft (MFI), Soviet equivalent to the F-22A Raptor. The design house did build the Article 1.44 technology demonstrator, but the economic troubles in Russia permitted this rather large aircraft to perform only two flights before it was grounded.

In the new economic realities the Russian air force was looking for less expensive options. That time the Indian air force expressed interest in a next-generation fighter with medium (normal) takeoff weight, at approximately 22 tons. In 2001 Mikoyan and Sukhoi were asked to come up with a new, clean sheet design that would potentially meet new requirements of the Russian and Indian air forces. Sukhoi came first in the competition.

Since then the PAKFA project has come through many evolutions. Critical design review passed in 2004, detailed design won approval in 2006. Sukhoi won respective governmental contracts in 2001, 2003 and 2006. Given several alternatives, the Russian air force opted for a “super maneuverable” fighter powered by a pair of NPO Saturn AL-41F derivatives.

Initially, the AL-41F engine in the class of the 20-tonne thrust was developed for the ill-fated Mikoyan’s MFI/Article 1.44. For the new Sukhoi aircraft, the AL-41F was downsized into dimensions of the AL-31F which powers the Su-27/30 Flanker family. The derivative was referred to as the AL-41F1A and, later, the Item 117. A mix of something new (from AL-41F), something old (AL-31F’s hull and modules), the engine can develop 14,500kgf of thrust at full afterburner or 8,800kgf at military power. It has swivel nozzles for thrust vectoring.

Metal for an operable prototype was cut in 2007. For the first time in Russian practice, prototype of a new fighter was built by a mass production plant (KnAAPO) rather than an experimental aircraft factory of a Moscow-based design house. Final assembly work commenced in early 2009. A total of six airframes are needed to complete testing: two airframes for ground tests and four for flight trials.
Static tests

Static tests started in summer 2009 on the T50-0. Second airframe was something new in Russian practice by its functionality. To reflect this, this device is referred to as the T50-KNS, the suffix stands for Comprehensive Full-Scale Test-Bed. This device comes equipped with two Item 117 engines, KSU-50 comprehensive control system (its responsibility also includes control of the engines which do not have their own control systems), electrics, hydraulic and fuel lines. In short, the T50-KNS is a real thing for everything except that it is not intended for flight tests (its systems are not flight-qualified on the ground of simplicity and costs). This device was used for high speed taxi runs (including lifting the nose wheel off ground) on 23 December 2009, as a part in preparations to PAKFA’s maiden flight.

In January 2010 a Su-27M served as a test bed for flight trials of PAKFA’s engine. The Side 710 had one of its two AL-31F turbofans replaced by an Item 117. In this form the aircraft made several sorties before the Item 117 was rendered mature enough for powering PAK FA on its first flight. The T50-1 commenced ground testing in the fall of 2009. It proceeded with taxi runs on 21 January 2010 and got airborne later that month.
How stealthy the PAKFA is going to be?

As of today, it is the biggest question to its designers. Sukhoi officials claim PAKFA shall have radar signature similar to that of the Raptor. A careful look at the T50-1 raises doubts about it. Does Sukhoi completely rely on the new coatings absorbing electromagnetic waves? Will PAKFA production examples get their air intakes reshaped so as to have S-like air channels for lower exposure of the engines’ fans to outside viewers? With having answers to these questions, it is difficult to estimate combat worthiness of the new Russian fighter. Besides, there is a shortage of trustworthy information available on PAKFA’s weapons.

There is a lot of uncertainty about powerplant. The Russian air force wants a more modern engine than the Item 117, which is seen as a temporary solution only. NPO Saturn and MMPP Salut have been competing for the right to develop a more suitable engine for the PAKFA. The Russian MoD ran tenders between them. It is not clear now whether the ministry will commit funds to development of a better engine or make do with the Item 117 as a cheaper alternative.
What is coming next in development of the Russian fifth generation fighter program?

UAC president Alexey Fedorov promised that two more operable PAKFA prototypes will be flown by the end of this year. The third aircraft shall come with a radar suite. Firing tests may start next year.

Summarizing, we can say that the Russian fifth generation fighter program has come a long way before a combat capable aircraft appears as a result of it. And when does appear, it will likely to bear only feasible resemblance to the T50-1.

 

[jha]

Thats an old but excellent article..