Russian Stealth

In January Russian jet maker Sukhoi started the flight testing of the fifth generation T-50 fighter developed under PAK FA program. The new fighter is intended to replace the Russian Air Force’s Su-27 fighter from 2015. The first prototype made its 47 minutes maiden flight from the airfield of Sukhoi’s KnAAPO facility in Komsomolsk-on-Amur on January 29. Two more flights were conducted on February 12-13.
Sukhoi was officially selected as a lead contractor under PAK FA (Perspectivny Aviatzionny Kompleks Frontovoy Aviatzii or future tactical aviation aircraft system) in 2002, but before that, in the late 1990s the company tested Su-47 demonstrator with forward swept wing that was later used for testing some of T-50’s technologies. As for now Sukhoi has assembled three prototypes at KnAAPO facility. In 2009 the first one, T-50-0, was delivered to Moscow in 2009 and is used for static tests. The second prototype, T-50-KNS, is believed to be used as a complex full-scale stand intended for ground testing. The third, flying, prototype, reportedly dubbed as T-50-1, started taxi trials at the end of December 2009.
Being approximately of the same size as Su-27, T-50 is definitely shaped for stealth with the chined forward fuselage, planform edge alignment, internal weapons bays and small vertical tails. According to Sukhoi, the aircraft will demonstrate unprecedented small radar cross section in radar, optical and infrared range due to composites and innovative technologies applied in the fuselage, aerodynamics of the aircraft and decreased engine signature. The designers doesn’t reveal technical parameters, but the Indian defense ministry officials whom Sukhoi showed T-50 prototype at the end of 2009 were cited by the Indian media saying the aircraft’s radar cross section will be 0.5 square meters compared to 20 square meters of Su-30MKI.
T-50-1 prototype is likely to have a minimal set of equipment required for the initial flight testing, while its major subsystems like avionics suite and engines are being developed simultaneously.
Initially the first PAK FA prototype was intended to have a pair of NPO Saturn 117S engines — a further modification of AL-31F engines uprated to 14.5 ton thrust also installed at the new Su-35 multirole fighters. But the engine designer announced T-50-1 took off with "a completely new powerplants". Ilya Fyodorov, NPO Saturn CEO and a head of PAK FA engine program explained that compared to 117S it has further increased thrust and new digital control system specially adapted for T-50’s performance. "Our new engine is based on 117S to the same extent as Al-31 powerplants were based on their Al-21 predecessors", said Fyodorov. According to media reports the new engine modification dubbed 117M has a thrust of 15 ton.
Earlier Sukhoi and the Air Force announced that 117 engines will be used only during the development trials while the serial fighters will be powered by new engines. Fyodorov explained that NPO Saturn currently researches some new technologies that can be in 2-3 years applied on 117M to develop the engine for serial PAK FA. "In contrast with the Superjet [where we lag behind with our SaM146 engine], within the PAK FA program we keep pace with Sukhoi", said NPO Saturn CEO.
T-50’s avionics is being developed by Ramenskoe Design Bureau. The company’s head Givi Djanjgava earlier explained that the avionics suite for the new fighter includes six-processor computer, visualization tools and flight instrument system. Sukhoi said the new suite will integrate "electronic pilot" functionality, as well as advanced phased-array antenna radar. New on-board equipment will also give T-50 network-centric capabilities.
The X-band AESA radar for T-50 is being developed by Tikhomorov NIIP design bureau. Its antenna first unveiled at Moscow MAKS in August 2009 has 1,500 T/R modules. According to Anatoly Sinany, NIIP chief designer, now the radar’s prototypes conduct bench tests while the first radar for the aircraft is expected to be ready in mid-2010. Besides X-band radar, NIIP also develops an L-band active phased array that will be installed on the T-50’s leading edge-flaps.
The Russian government officials said T-50 will conduct few more flights in Komsomolsk-on-Amur and then will continue test program in Gromov LII flight center in Zhukovsky, near Moscow. The fighter is expected to arrive in Zhukovsky in the beginning of March.
Meanwhile the Russian Air Force has already submitted to Sukhoi their updated proposals for T-50’s requirement specifications. "One of the main features introduced in this aircraft is [artificial] intelligence. This means that the onboard suite can help the pilot to complete the most difficult tasks", explained the Air Force official sited by the Russian media.
The Air Force’s training centre in Lipetzk should receive the pre-production batch in 2013 while the serial deliveries are expected to start from 2015. Although Sukhoi and the designers of major subsystems has a lot of work ahead to complete the aircraft, such delivery deadlines could be possible as the Russian government promises full financial support for the program. Russian vice-premier Sergey Ivanov mentioned that the PAK FA program is a top defense priority and it receives 100% funding annually.
The more distant future includes development of PAK FA’s two-seat version dubbed T-50UB that will also serve as a basis for the Indian Air Force’s FGFA fighter. Russian and India signed a corresponding intergovernmental agreement signed in 2007, while the contract between India’s HAL and Sukhoi will be reportedly inked very soon. India plans to buy 250 new fighters while the Russian military are expected to procure up to 300 aircraft.