T-50 completes early flight and bench tests

 - July 17, 2010, 9:14 AM

Sukhoi has completed its preliminary flight and bench trials program for the T-50 PAK-FA fighter. Three airframes were built for the initial campaign, comprising one static aircraft (T-50-0), one flying prototype (T-50-1) and an avionics testbed (T-50-2). A display flight by T-50-1 on June 17 in front of Russian Prime Minister Vladimir Putin marked the 16th time the aircraft had flown.

Russia has a stated requirement for up to 420 PAK-FA aircraft, which may become the Su-50 in service. This number would equip 10 air regiments, each with 36 frontline aircraft and six reserves. However, it is likely that this total will not be reached. India, meanwhile, has a requirement for 250 of what it calls the Fifth Generation Fighter Aircraft (FGFA).

India has yet to join the T-50 program, but it has stated that it intends to do so and Hindustan Aeronautics Ltd. (HAL) will likely be given development work in the navigation, mission computer and other systems. FGFA is envisioned as a two-seater, but reports suggest that India could acquire single-seat T-50s pending development of the full FGFA configuration.

The T-50-1 was completed in the KnAAPO works at Dzemgi airfield near Komsomolsk-na-Amur. The first taxi tests were performed last December and high-speed tests were conducted in late January in preparation for the first flight. The maiden 47-minute sortie was flown on January 29 with Sergey Bogdan at the controls.

The aircraft flew again in early February to compete initial basic airworthiness and systems tests before being disassembled for transport to Moscow. On April 8 an Antonov An-124 Ruslan carried it to the Gromov Flight Research Institute at Zhukovsky, together with flight support equipment. The aircraft flew again from its new home on April 29.

Further T-50s will be constructed to support the flight test program, which Putin announced would encompass more than 2,000 flights. Initial production is scheduled to begin at KnAAPO in 2015, with limited service-entry to take place that year as well.

T-50 Technology
Sukhoi’s T-50 embodies a high degree of new technology and is intended to provide a “fifth-generation” capability in an aircraft that is considerably cheaper to produce than the Lockheed Martin F-22, its closest rival. Low observability in the forward hemisphere is a key driver in the T-50 design, which, in planform at least, resembles that of the F-22. The forward areas feature faceting (smooth, polished surfaces) and the design incorporates advanced radar-absorbent materials and coatings. The intake trunks are of serpentine shape, but whether they completely shield the engine compressor face and whether they incorporate some form of radar blocker has been the subject of considerable debate.

The engines themselves are the NPO Saturn 117, derived from the 117S intended for the Su-35BM. The first of these engines flew in the left-hand bay of the T-10M-10 (an Su-35 testbed) on January 21 this year, shortly before the T-50’s first flight. The engines incorporate 16-degree all-axis thrust vectoring, which combined with the relaxed stability and fly-by-wire controls confers outstanding maneuverability on the T-50. It is widely accepted that the T-50 will not match the Lockheed Martin F-22 fighter in terms of all-aspect stealthiness, but it is expected to be more agile. NPO Saturn and MMPP Salyut are working together on a definitive engine for the T-50, in the 16- to 16.5-metric-ton thrust class (that is, up to 36,375 pounds thrust).

An innovative feature of the T-50 is its SH121 radar complex from NIIP Tikhomirov. This comprises the N050 main array in the nose, with more than 1,500 transmit/receive modules, plus two side-facing X-band arrays in the lower forward fuselage sides. Conformal L-band arrays are mounted in the leading-edge root extensions. T-50-1 does not have radar fitted, but it does have a dummy infrared search-and-track turret installed. In service this is expected to be a development of the OLS-35 developed for the Su-35BM.

In terms of avionics, the T-50 represents a major advance for a Russian fighter and it has been designed to take full advantage of datalink and sensor-fusion technology. In the cockpit the pilot has two very large multifunction displays mounted side-by-side, with an upfront controller for a wide-angle head-up display. Control is by a center stick that incorporates advanced HOTAS controls. The pilot will have a helmet-mounted sighting system, perhaps based on the ZSh-10.

In its air-to-air role, the T-50 will have a wide range of weapons available, from internal 30-mm cannon to 400-km missiles. The aircraft’s huge internal bays can accommodate up to eight of the current Vympel R-77 active-radar missiles, but there are several developments under way to provide the PAK-FA with even more capable weapons.

Vympel is working on the Izdeliye 180/K-77M, a derivative of the R-77 with a double-pulse engine, new seeker and traditional tailfins in place of the R-77’s “chip-slicer” lattice fins. The Izdeliye 180PB/K-77ME is an air-breathing ramjet version similar in concept to the Meteor, but it appears that the solid-propellant version–roughly equivalent to the AIM-120D AMRAAM–offers greater potential in a shorter time.

The PAK-FA is also expected to carry a class of weapon unique to Russia–
a very long range air-to-air missile (VLRAAM), with a range of around 400 kilometers. Two designs are in development for the T-50 application: Vympel’s Izdeliye 810 and Novator’s Izdeliye 172/K-100. The T-50 will also carry short-range weapons.

A range of air-to-ground weapons is also intended for the T-50, including a new generation of anti-radiation missiles such as the Kh-36 and Kh-58Ush, and a variety of laser- and EO-guided bombs and missiles. Many of them can be carried internally, but the T-50 also has four underwing hardpoints for the attachment of external pylons for operations when stealth is not an overriding factor. The “tunnel” between the engine trunks also provides the space to carry extremely large weapons, such as long-range anti-ship missiles.