WHILE SPECULATION still swirls around Sukhors T-50, there are some near certainties. It will almost certainly cost more, arrive later and initially do less than originally envisaged. These are characteristics it will share with all fourth and fifth-generation combat aircraft projects.
A further eleven development aircraft are due to join the programme between the end of this year and 2015, according to former air force chief General Alexander Zelin, now a defence advisor to the government. The fourth prototype is due for completion before the end of this year, and state testing is pencilled in to begin in 2013. Eight of the total of 14 will be pre-production, rather than prototype, airframes.
Although the notional in-service date service date remains 2016-17, this will possibly slip given Russia's recent track record on combat aircraft development. To what extent the air force is using the Su-35S as a hedge against T-50 delay is unknown, but around 90 of the latest version of the Flanker are due for delivery between now and 2020. Though originally intended for export only, the air force decision to procure this variant also will, assuming no further delay to the Su-35S, provide it with a badly needed multi-role fighter. Exactly how much longer the air force will be able to keep 'classic' Su-27s in service is unclear. It would be reasonable to assume that in the medium term, the air force roadmap for its fighter fleet will consists of the T-50 (Su-XX), Su-35S, Su-27SM, SU-30SM, MiG-29SMT, and MiG-31BM, with the retirement rate of single-role variants of the Flanker and Fulcrum increasing.
Like its US counterpart, if on a far more severe scale, the Russian air force's Soviet-era plan to transition to a fifth-generation combat aircraft fleet have proved economically unsustainable. Even if the original procurement number for the US Advanced Tactical fighter (F-22) tumbled from 750 to the eventual 195 Raptors built, at least the aircraft made it into series production and into front line service.

Requirement's History
Sukhoi's efforts to meet the Russian Air Force's PAK FA (future frontal aviation combat aircraft) requirement are sometimes cast by those who might favour 'mirroring' as the Moscow combat aviation community's retort to the Raptor. When the overall design was declassified it was characterised in some quarters as the 'Raptorski' - Silent Flanker would have been a better tag. The T-50 is the Russian Air Force's (VVS) second .-if not third - attempt to address the fifth-generation fighter conundrum, If the requirement reflects the F-22 as the probable threat driver, it is not the only one, and nor does it mean it is attempting to directly emulate the Raptor. Both the F-35 and the Chinese J-20 will probably have figured in Russian thinking, as well as Europe's fourth-generation fighter stable.
The T-50 design is well over a decade later than that of the F-22. The USAF's formal requirement to replace the F-15 was established toward the end of 1981. The YF-22A was shown for the first time in 1990. Russia also appears to continue to pursue a different approach to platform survivability overall, with less emphasis on minimising all-aspect radar cross section reduction.
Moscow's first riposte to Washington's requirement to succeed the F-15 in the air superiority role has been reduced now to an apron ornament at LII Gromov on the outskirts of Moscow. Mikoyan's lzdeliye 1.44 is parked on the MiG stand at Llf, having flown twice. Its maiden flight was in February 2000, nearly a decade later than intended. Conceived in the early 1980s to meet the MFI (multi-role frontal fighter) requirement, the programme was buried by the collapse of the Berlin Wall. While MiG struggled on with the project throughout the 1990s, there was not enough funding to complete the initial development of the heavy fighter demonstrator, let alone progress to a production-standard aircraft.
Today's Russian Air Force was formed in 1992 out of the remnants of the Soviet Air Force. Mostly it inherited problems, and over the remainder of the decade it was not gifted the wherewithal to rectify fundamentally any of the issues that eroded its capability as a combat force. Russian aviation - military and civil - was nearly stopped dead during the 19905. Col Gen Abrek Ayupov, a former deputy air force commander for procurement, and now an advisor to Sukhoi, suggested this was a "period of stagnation'. Raw figures only hint at the turmoil of the first post-Soviet decade for the air force. While overall aircraft numbers tumbled and first-generation Hankers and Fulcrums began to age, there was nothing even resembling an affordable and coherent procurement effort to successfully introduce new or upgraded types.
The 1990s offer many a possible nadir for the Russian air force, but perhaps 1998, when not a single combat aircraft was delivered, marked the lowest of low points. Deliveries during the 19805 had numbered several hundred aircraft annually. Throughout the 1990s, however, there remained ambitions to acquire a fifth-generation multi-role fighter, and some work was sustained, if only with a trickle of financial support.
In 2002 Sukhoi's T-50 design was selected in preference to proposals from MiG and Yakovlev to meet the Russian air force requirement for a multi-role fighter to replace the Su-27. A 60-aircraft order is thought to be part of the 2011-2020 state defence plan. Sukhoi's forward-swept wing technology demonstrator, known variously as the 5.37 and Su-47 Berkut, most probably started off as a TsAGI (Central Aero-hydrodynamics Institute) research programme, known in the 1980s as the S.32. In certain key areas - such as the increased use of composite material and the internal weapons carriage (a concession to radar cross section reduction) - the demonstrator has proved
of considerable value, even if it was an unlikely contender to ever fulfil the slot as a successor to the Flanker. Theoretical work into the design of a next-generation fighter was also continuing within the air force's research laboratories, including the 2nd Central Scientific Research Institute and at the State Research Institute of Aviation Systems, more commonly known as GoSNIIAS. The 2nd Central Scientific Research Institute is one of Moscow's centres of expertise on radar-cross section (RCS) measurement and reduction. In the early 2000s it was looking at a range of passive and active low-observable technology applicable to combat aircraft.

Signature Management
The Sukhoi design reflects a fundamental effort to manage the aircraft's radar signature, with a range of characteristics now associated with second-generation low observables. Whether the aircraft will at some point be fielded with active as well as passive signature management remains to be seen. Russia, however, has a long-standing interest in researching the use of discrete plasma fields to shield Radio Frequency (RF) reflectors. A project known as 'Marabou' is believed to have been associated with the abortive 3M-24/Kh-80 Meteorite cruise missile programme. This effort may have looked at using plasma to shield the chin intake, which represented a large radar reflector)
The front and forward side quadrant of the T-50 airframe design is clearly intended to reduce significantly its RCS. The same, however, cannot be said of the rear of the prototype aircraft. The design of the rear section of the fuselage and the engine bays appears to show less concern for radio frequency signature management. It is worth keeping in mind that the T-50 is a prototype and that Sukhoi in the past has not been averse to significant design changes, if deemed necessary. The most obvious is the complete redesign of the T-10 (Su-27 Flanker), where the early stages of the flight test programme revealed serious - in fact fatal - shortcomings. Following a re-design, handling and performance were considerably improved, leading to the first in-service standard aircraft and eventually to the Su-35S. While far from suggesting the T-50 will see such a radical design overhaul, design refinements are not out of the question.
The third T-50 prototype, T-50-3, did indeed show some minor airframe modifications, while the main elements of the aircraft's sensor suite were also beginning to be fitted. A fourth airframe is intended to join the flight test programme by the end of 2012. There is considerable speculation this aircraft will include structural strengthening to remedy shortcomings identified in T-50-1. The first airframe has not been seen taking part in the flight test programme since August 2011.
While the Russian military, and therefore the manufacturer, remains reticent to provide even general design data on the T-50, the design is clearly in a similar class to that of the Flanker. Intriguingly the initial programme to identify a successor to the MiG MEI in the latter part of the 1990s was associated by some reputable commentators with a requirement known as the Light Tactical Aircraft (Logkiy Frontovoy Samolyot). There was considerable debate within the Russian design and requirements community as to where to pitch the emerging replacement - those advocating a heavier platform design won the day. Both the main fighter designers, however, are likely to continue to look at a light-to-medium combat aircraft design. Russian industrialists have in recent years suggested this continued to be an area of interest, though funding and industrial capacity issues could mean this remains as just an ambition.
The third T-50-3 prototype will be the first to be used for sensor trials. It is fitted with an active electronically scanned array being developed by NIIP, with the overall radar system having multiple apertures. Besides the main (N-036) X-band radar, the intent is to also fit two adjunct X-band antenna (the forward and side looking arrays follow the scheme originally intended for the MR [and F-22]). The MFI was also intended to have a smaller rear-facing array, though presently it does not seem the PAK FA will be fitted with such a system. L-band arrays are also reportedly included on the inner wing section.
Complementing the radar sensors is a distributed electro-optical system. The T-50-2 had the infra-red search and track - in the traditional location - and what is claimed by some to be a turreted Directional Infrared Counter Measures (DIRCM) to the rear of the cockpit. Additional electro-optical sensors, including at least two ultraviolet apertures, are intended as part of the production standard aircraft. The complete electro-optical package may be tested on the T-50-3 airframe.
Along with gaining experience of using composites for airframe structure, the 5.325.37 Berkut provided Sukhoi with its first experience of designing an internal weapons bay. While the internal carriage of weapons has clear advantages in terms of RCS, it also poses a number of challenges. These include environmental and thermal management, weapons packaging, and release and clearance issues. It is probable that Sukhoi and the VVS research established explored the internal carriage and release of weapons using the S.37.

Weapons Inventory
The T-50 configuration has tandem weapons bays in the tunnel between the engines along with what are suggested to be single-weapon housings in fairings behind the outer edge of the movable leading edge. Weapon clearance from the T-50 main bays could result in some interesting test shot footage, though this is unfortunately unlikely to be released in the West.
To complement the aircraft, a range of improved and new air-to-air missiles (ARM) is now in development, or in some cases work has re-started. In the Soviet-era a new combat aircraft often brought parallel development of a new-generation of air-to-air weapons. Some of the systems that may eventually be integrated on the T-50 may have started out their design life aimed at the MFI.
Reflecting the problems suffered by the airframe designers, air-launched guided weapons development in Russia ground to a near halt in the 19905 - work an the weapons suite for the MFI was shelved, while upgrade programmes stalled for existing systems, such as the medium-range radar-guided R-77 (AA-12 Adder), the IR-guided 11-73 (AA-11 Archer) and the follow-on to the long-range 11-33 (AA-9 Amos), the R-37 (AA-X-13). The middle of the last decade began to see an increase in activity. A long-touted upgrade for the 11-77, the Item (lzdeliye) 170-1, was finally given the government go-ahead - or perhaps re-started - in 2003.
At least ten test rounds of this improved variant of the Adder have been manufactured, and test firings finally got under way after several years' delay - apparently due to a lack of a suitable launch platform. The 170-1 (the AA-X-12B?) is now in production for the Russian air force and corresponds to the Russian generic export title RVV-SD. At least in its present form, the 170-1 is not currently intended for the PAK FA.
The best insight so far into the weapons planned for the PAK FA was provided in a 2006 paper authored by Gennady Sokolovsky, former general director of Vympel, and the dominant figure in Russian air-to-air weapons design for a generation. The paper identified a range of programmes, including short, medium, long and ultra-long range AAMs intended for Russian combat aircraft.
Two further developments of the R-77 family may be destined for the PAK FA: Items 180/K-77M and 180PD. Vyrnpel officials confirm they continue to work on further upgrades of the missile beyond the Item 170-1, but are reluctant to discuss it further. Both these variants of the R-77 appear to dispose with the signature lattice rear fins in preference for a cropped conventional cruciform design.
The Sokolovsky paper also talked in general terms about a new medium-range AAM, and this may correspond to the Item 270 designation. This designator was included in a document related to the weapon ejection system for the T-50. The document also includes the Item 810, an extended long-range weapon for the PAK FA.
The ultra-long range interception role was left to the R-33 armed MiG-31 Foxhound in the Soviet era and then Su-27M/MFI developments. These aircraft were also to have an ultra-long range air-to-air missile capability, and the PAK FA continues this trend, it remains possible that prior to the Item 810, the aircraft was equipped with Item 610M. The 610M is probably the local variant of the RVV-BD shown for MAKS 2011.
Russia continues to lag on imaging infrared technology, and exactly which short-range AAM the aircraft will be fielded with remains unclear. Vympel officials now suggest the company is focusing on further development of the 13-73 design, with claims that the K-30 dogfight missile effort, launched in the mid-1980s, has been dropped. The Item 760 development of the R-73 may well be the initial short-range missile for PAK FA.
Development of the aircraft's initial air-to-surface inventory is also underway. The modular Kh-38 design - the intended successor to the Kh-25 (AS-10 Karen) - is now in development. The weapon has folding mid-body and rear fins for internal carriage, with several variants of guidance intended. Along with the E/O version, there are semi-active laser, radar and Global Navigation Satellite System (Glonass)-guided variants of the design. Safe separation trials of form and fit representative missile bodies have reportedly already been carried on the Su-34 long-range strike variant of the Flanker.
The PAK FA has also provided a new lease of life to a rather old missile, the Kh-58 (AS-11 Kilter), in the shape of the Kh-58UShK. This revamped variant of the Kilter has a broadband passive radar seeker and appears intended to provide the aircraft with a long-range anti-radiation missile. The choice of the Kh-58, rather than the rocket/ ramjet-powered Kh-31, may have been driven by the internal bay size. The Kh-31PM, an upgraded version of the Krypton with a broadband passive seeker, has a longer fuselage length because of an additional solid propellant booster and fuselage plug. The Kh-31P is 4.7m (15ft Sin) in length, while the Kh-31PM is 5.3m (17ft 2in). The Kh-58UShK is 4.2m (13ft 0in), A smaller anti-radiation missile, the Kh-36P, may also be intended for the aircraft, although the development status of this programme has not been made public. A variety of precision-guided bombs will also form part of the aircraft's eventual weapons inventory.

(57) Реферат:
Изобретение относится к области авиационного двигателестроения, а именно к конструкции плоских сопел турбореактивных двигателей. Плоское сопло турбореактивного двигателя содержит корпус, дозвуковые створки, шарнирно прикрепленные к корпусу, сверхзвуковые створки, шарнирно соединенные с дозвуковыми, и внешние створки, одним концом шарнирно прикрепленные к корпусу, а другим соединенные со сверхзвуковыми створками. Дозвуковая створка выполнена в виде каркаса, состоящего из двух частей, соединенных каналами для охлаждающего воздуха. На передней части неподвижно установлен экран, снабженный двухпозиционным краном перепуска охлаждающего воздуха, и шарнирно прикрепленная заслонка. Задняя часть снабжена днищем, установленным с возможностью поворота вокруг поперечной оси каркаса, с неподвижно прикрепленным к нему кронштейном. Сверхзвуковая створка снабжена наружным и внутренним теплозащитными экранами. Задняя часть каркаса заведена под наружный экран сверхзвуковой створки, а заслонка со стороны среза сопла соединена силовыми тягами с кронштейном днища, а с другой стороны - тягами с двухпозиционным краном перепуска. Изобретение позволяет снизить инфракрасное излучение на бесфорсажных режимах работы двигателя. 1 з.п. ф-лы, 4 ил.
Изобретение относится к области авиационного двигателестроения, в частности к конструкции плоских сопел турбореактивных двигателей (ТРД).
Известно плоское сопло ТРД, содержащее корпус, к боковым стенкам которого шарнирно прикреплены сбалансированные дозвуковые створки, сверхзвуковые створки, шарнирно соединенные с дозвуковыми, и внешние створки, один конец которых шарнирно подвешен к боковым стенкам корпуса, а другой соединен со сверхзвуковыми створками (см. патент США 3973731 класса 239.265.39, опубл. в 1976 году).
Указанное сопло обеспечивает реверсирование и изменение вектора тяги двигателя.
Недостаток указанного сопла состоит в том, что оно на бесфорсажных режимах обладает высоким уровнем инфракрасного излучения (ИК) от деталей форсажной камеры и турбины, имеющих высокую температуру.
Задачей изобретения является снижение ИК-излучения на бесфорсажных режимах работы двигателя.
Указанная задача решается тем, что в известном плоском сопле турбореактивного двигателя, содержащем корпус, дозвуковые створки, шарнирно прикрепленные к корпусу, сверхзвуковые створки, шарнирно соединенные с дозвуковыми, и внешние створки, одним концом шарнирно прикрепленные к корпусу, а другим соединенные со сверхзвуковыми створками, согласно изобретению дозвуковая створка выполнена в виде каркаса, состоящего из двух частей, соединенных каналами для охлаждающего воздуха, причем на передней части неподвижно установлен экран, снабженный двухпозиционным краном перепуска охлаждающего воздуха, и шарнирно прикрепленная заслонка, а задняя часть снабжена днищем, установленным с возможностью поворота вокруг поперечной оси каркаса, с неподвижно прикрепленным к нему кронштейном, сверхзвуковая створка снабжена наружным и внутренним теплозащитными экранами, при этом задняя часть каркаса заведена под наружный экран сверхзвуковой створки, а заслонка со стороны среза сопла соединена силовыми тягами с кронштейном днища, а с другой стороны - тягами с двухпозиционным краном перепуска.
Другой конец каждой внешней створки заведен в направляющую, установленную на сверхзвуковой створке с возможностью поворота вокруг ее поперечной оси.
Такая конструкция обеспечивает на режиме «малой заметности» образование дозвуковыми и сверхзвуковыми створками центрального тела, препятствующего прохождению прямого излучения от разогретых узлов форсажной камеры и турбины через сопло. Видимые на этом режиме поверхности внешних створок охлаждаются вентиляционным воздухом мотогондолы самолета, а наружные поверхности сверхзвуковых створок охлаждаются воздухом из канала охлаждения сопла, вследствие чего уменьшается ИК-излучение от них.
На приведенных чертежах:
на фиг.1 показан продольный разрез плоского сопла на бесфорсажном режиме;
на фиг.2 - положение сопла на режиме «малой заметности»;
на фиг.3 - продольный разрез по кинематическим элементам, обеспечивающим режим «малой заметности»;
на фиг.4 - вид сверху на дозвуковые и сверхзвуковые створки сопла.
Сопло содержит корпус 1 и дозвуковые створки 2. Створки 2 в средней части шарнирно прикреплены к боковым стенкам корпуса. К дозвуковым створкам 2 шарнирно прикреплены сверхзвуковые створки 3. Внешние створки 4 передним концом шарнирно подвешены к боковым стенкам корпуса 1, а задним заведены в направляющие 5, установленные в сверхзвуковых створках 3 с возможностью поворота вокруг осей 6, закрепленных на сверхзвуковых створках 3.
Дозвуковая створка 2 выполнена в виде каркаса 7 с неподвижно закрепленным на его передней части экраном 8 и соединенного с поворотным днищем 9 с помощью оси 10, обеспечивающей возможность поворота днища.
В средней части каркас выполнен в виде каналов 11 для прохода охлаждающего воздуха в заднюю часть каркаса, сопрягаемую со сверхзвуковой створкой 3.
На каркасе 7 перед каналами 11 шарнирно установлена заслонка 12, которая соединена силовыми тягами 13 с кронштейном 14, неподвижно установленным на днище 9. С другой стороны заслонка 13 через тяги 15 кинематически соединена с двухпозиционным краном 16 для перепуска охлаждающего воздуха, установленным на каркасе 7 с возможностью поворота вокруг оси 17. В передней части створок 2 шарнирно установлены гидроцилиндры 18, штоки которых соединены с кронштейнами 14.
Во внешних створках 4 выполнены полости 19 для прохода вентиляционного воздуха из мотогондолы. На наружных поверхностях сверхзвуковых створок 3 неподвижно установлены экраны 20, которые передней частью сопрягаются с задней частью каркасов 7, а на их внутренних поверхностях неподвижно закреплены экраны 21.
Устройство работает следующим образом. Перевод сопла в положение «малой заметности» по инфракрасному излучению производится из положения сопла, занимаемого на бесфорсажном режиме работы двигателя (см. фиг.1). При подаче сигнала перевода сопла в режим «малой заметности» гидроцилиндры 18 поворачивают за кронштейны 14 днища 9 вокруг осей 10 до упора друг в друга. Одновременно кронштейны 14 через силовые тяги 13 поворачивают заслонки 12 до упора во внешние створки, перекрывая канал вентиляционного воздуха из мотогондолы и направляя горячие газы в межстворочное пространство. Под давлением газов сверхзвуковые створки 3 поворачиваются к центру сопла до упора друг в друга вокруг шарниров на створках 2, при этом направляющие 5 поворачиваются вокруг осей 6, закрепленных на створках 3. Таким образом образуются два канала с критическим сечением и срезом, разделенных центральным телом.
При повороте заслонки 12 до упора во внешнюю створку она через тяги 15 поворачивает кран 16 вокруг оси 17, в результате чего перекрывается подэкранная щель под створкой 2 и открывается щель во внутреннюю полость каркаса 7. Далее охлаждающий воздух через каналы 11 и заднюю часть каркаса проникает в полость между наружным экраном сверхзвуковой створки 3 и наружной поверхностью створки. Весь вентиляционный воздух из мотогондолы направляется в полости 19 во внешних створках 4.
Такое выполнение конструкции обеспечивает на режиме «малой заметности» образование дозвуковыми и сверхзвуковыми створками центрального тела, препятствующего прохождению излучения от турбины и форсажной камеры через сопло, а также эффективное охлаждение проточной части сопла и, как следствие, значительное уменьшение инфракрасного излучения от хвостовой части двигателя.
Осуществление изобретения позволяет существенно уменьшить инфракрасное излучение двигателя и эффективную площадь рассеивания радиолокационного излучения на режиме «малой заметности».

Формула изобретения
1. Плоское сопло турбореактивного двигателя, содержащее корпус, дозвуковые створки, шарнирно прикрепленные к корпусу, сверхзвуковые створки, шарнирно соединенные с дозвуковыми, и внешние створки, одним концом шарнирно прикрепленные к корпусу, а другим соединенные со сверхзвуковыми створками, отличающееся тем, что дозвуковая створка выполнена в виде каркаса, состоящего из двух частей, соединенных каналами для охлаждающего воздуха, причем на передней части неподвижно установлен экран, снабженный двухпозиционным краном перепуска охлаждающего воздуха, и шарнирно прикрепленная заслонка, а задняя часть снабжена днищем, установленным с возможностью поворота вокруг поперечной оси каркаса, с неподвижно прикрепленным к нему кронштейном, сверхзвуковая створка снабжена наружным и внутренним теплозащитными экранами, при этом задняя часть каркаса заведена под наружный экран сверхзвуковой створки, а заслонка со стороны среза сопла соединена силовыми тягами с кронштейном днища, а с другой стороны - тягами с двухпозиционным краном перепуска.
2. Плоское сопло турбореактивного двигателя по п.1, отличающееся тем, что другой конец каждой внешней створки заведен в направляющую, установленную на сверхзвуковой створке с возможностью поворота вокруг ее поперечной оси.