Aircraft that are designed to avoid being detected by radars by reducing the infrared signature, radio-frequency signals and radar signature are called Stealth aircraft. Stealth technology is a combination of technologies that greatly reduces the chances of detecting an object using conventional systems. Germans constituted a program for the development of an aircraft with stealth technology during World War II. These aircraft are not invisible but are extremely tough to be detected on conventional radar.
The roots of stealth technology are believed to be tangled with the German designed Horten Ho 229 aircraft. Germans designed the wings of the aircraft with two thin plywood panels. These panels were glued together with an adhesive that contained charcoal and sawdust mixture. The center pod of the aircraft was made from welded steel tubing and wing spars were built from wood. The aircraft however was never operationalized.
After the war, the aircraft design was tested in US and it was found to be almost invisible to the Britain‘s Chain Home early warning radar. USA set-off towards the development of stealth aircraft. The first purpose built stealth aircraft is the Lockheed F-117 Nighthawk which saw combat during ‘Operation Just Cause’ in Panama.
USA soon realized the strategic importance of these aircraft and soon constituted several projects for the induction of these jets to its inventory. The induction of stealth aircraft by western forces left Russia vulnerable to undetected attacks. To counter this threat, Russia constituted the ‘Prospective Airborne Complex of Frontline Aviation’ or the PAK-FA program. Russia’s leading aerospace technology giant ‘Sukhoi’ was put in-charge of developing a 5th-gen multirole aircraft capable air superiority and ground attack sorties. ‘Stealth technology’ is an extremely demanding field. Russia alone could not conquer the hurdles and roped in India for a joint development program.
Indo-Russian military cooperation over the years has evolved from a simple buyer – seller framework to one involving joint research, development and production of advanced defense technologies and systems. A deal for the co-development of a 5th-gen aircraft was signed between Sukhoi and Hindustan Aeronautics Limited (HAL). The aircraft would have as many as 45 crucial developments over the T-50 aircraft.
The powerhouse for FGFA is the ‘Saturn AL-41F’ turbofan engines. The engine has interim super cruising and thrust vectoring capabilities. AL-41 F is currently under trials and thus the aircraft will initially be powered by ‘Saturn-Lyulka 117S’. The 117S themselves are an upgraded product achieved by clubbing AL-31F and improvising the technologies of AL-41F in the system. It can produce 142 kN and 87 kN of thrust with the afterburners engaged and disengaged respectively. The engine is equipped with circular thrust vectoring nozzles and has incorporated infrared and RCS reduction measures.
The engine is equipped with state-of-the-art FADEC (Full Authority Digital Engine Control) Nerve centre to the FADEC system is the ECU or Engine Control Unit. This controls critical aspects linked with the control and functioning of the engines. The introduction of FADEC ensures the maximum efficiency of the engine. Multiple input variables of flight conditions are received and analyzed by the ECU. The values analyzed by ECU are checked against set parameters. If there are changes in the operating values then it is returned to the required default value for achieving the appropriate flight conditions. FADEC handles most of the critical tasks and significantly reduces the pilot workload.
Also under development is an engine code named ‘Izdeliye 30’ which offers a thrust of about 40000lb and will enable the aircraft to achieve a max speed of about Mach 2 and has a service ceiling of 65000 feet. The aircraft can cruise at speeds up to Mach 1.8 and enjoys an operational range of 4590 kilometers.
Making the one-of-its-kind is advanced and powerful avionics suite. Upgraded Su-35S avionic suite form the core of the avionics package going on-board the T-50. Sh121 Multifunctional Integrated Radio Electronic System (MIRES) and the 101KS Atoll electro-optical system is the primary avionics suite.
Sh121 is equipped with the ‘N036 Byelka radar system’. Developed by Tikhomirov, the radar is an advanced Active Electronically Scanned (AESA) system which is formed from numerous small solid-state transmit/receive modules. The radar aims its beams at various directions from each module and these finally converge at a designated angle. The N036 radar system consists of a main nose-mounted X-band AESA radar.
For friendly-or-foe identification and electronic warfare the aircraft has two N036L-1-01 L-band arrays which are placed on the wings. Various computers and processors enhance the system information. The electronic countermeasure system of the aircraft is the L402 “Himalayas” system. The ‘UOMZ 101KS Atoll’ electro-optical system includes the 101KS-V infrared and track system which uses the infrared radiations emitted by objects to detect and track them.
IRST gives all-round situation awareness and can be effectively used for laser aided counter measures against heat seeking missiles. The system involves thermo-graphic cameras and is a passive system. It does not emit radiations like radars and thus helps realize the stealth quotient. The package also includes the 101KS-U ultraviolet warning sensors and 101KS-N navigation and targeting pods.
T-50 features a glass cockpit equipped with a 15 inch multi-functional LCD display. Information from various sensors installed on the aircraft is beamed on a Heads up Display (HUD) unit and this enables the pilot to have seamless concentration on the flight. Even the canopy of the aircraft receives a coating for increased stealth element. Saving the pilot in times of emergencies is the ‘NPP Zvezda K-36 D-5’ ejection seat. The ejection seat ensures safe ejection of the pilot within 2.5 Mach and can be operated up to 66000 feet. With the help of advanced life support systems of the aircraft pilots can perform up to 9-g maneuvers for almost 30 seconds at a go.
The airframe of the aircraft is designed with a planform alignment which enables to greatly reduce the radar cross-section. The protruding edges of the aircraft are designed to a pre-designated angle. Antennas and other protruding devices are recessed back into the aircraft’s main airframe. The aircraft is provided with S-shaped intake duct which is placed in the upper rear center of the aircraft. This enables to reduce the compressed outlet of the engine.
Special Radar Absorbent Material (RAM) is coated to the airframe and this helps in absorbing radar emissions. The first known RAM is Sumpf and Schornsteinfeger. German’s coated the snorkels and periscopes of their submarines with this RAM. Commonly used RAM technology to date is the iron ball paint which contains tiny spheres coated with carbonyl iron or ferrite. World’s first purpose built stealth aircraft F-117A used electrically isolated carbonyl iron balls of specific dimensions suspended in a two-part epoxy paint. Foam absorber, Jaumann absorber, Carbon nano-tube and Split-ring resonator absorber systems and are the other known stealth coatings known and in use till date.
Weapons bay of the aircraft is concealed in the airframe. The aircraft is enabled with two tandem main internal weapon bays. Each one of these is approximately 15 feet in length and 3 feet wide. In-charge of developing armament for the aircraft is Vympel. The main bay is equipped with two ejection launchers called the UVKU-50L system. This system can support missiles of up to 300kg in weight. On the airframe are six hard points and can be used during non-stealth runs. Primary weapon of the aircraft is the 9A1-4071K 30 mm cannon.
The aircraft is expected to carry up to 4-BVR missiles and 2-short range missiles to effectively take care of air-air threats. K-77M and K-74M2 with active radar-homing technology will be the short range missiles. The Izdeliye 810 will be the BVR missiles. Air-to-ground targets can be neutralized by Kh-38M, KA-250, KAB-500 precision guided bombs. The aircraft will also carry Kh-35UE and the Kh-58UShK anti radiation missiles.
The first aircraft of the program took to skies on 29 January 2010. The program has evolved rapidly with five prototypes having taken flight till date. The aircraft has completed external weapons trials. The first FGFA’s are to enter serial production by late-2016. India is expected to get the aircraft for trials by 2018. A single T-50 unit is estimated to be around US $50 million and compared to the American fielded F-22 Raptors these aircraft are extremely cost efficient.
Once inducted the FGFA will be a potent weapon in the arsenals of Russian and Indian forces. FGFA will surely act as a force multiplier. Thanks to its stealth technology, the aircraft can effectively carry out deep penetration bombing runs. This will surely help Indian forces in enjoying an upper hand over the unreliable neighbors.