In the year 1961 this land called India successfully made an indegeneous fighter aircraft, highly capable in terms of technology, so advanced that no other asian nation except Russia possessed such. The spinoff development from HAL HF-24 Marut gave rise to many new test configurations which ultimately produced greater aerospace expertise in our country. But a huge unsustainable political pressure killed this expertise and India’s aviation sector had to be sacrificed for the sake of diverting money and attention to development of Nuclear Capable Missiles.
Since then, the air of India is waiting for formidable fighters made by Indians, to take flight and secure us. The development of HAL Tejas mk1 is nearing completion and mass production would begin soon, this means our R&D labs would have had to wait until similar development activity for HAL’s AMCA project aren't started, moreover these labs need to run more to achieve more and develop an aerospace industry so strong that it shouldn't ever get destroyed due to political pressure like what happened last time with Marut.
It was imperative that HAL would undertake technically challenging projects that would not just prove a base for future platforms but also increase the knowledge and understandings of aerodynamics. This knowledge vin today's time would pass on in our universities our private aerospace firms and would root in so deep that could never be uprooted. HAL’s Mk2 LCA developments echo the same sense of feeling even though critics can always judge the projects adversely. Actually it shouldn't be called LCA now as it is a medium weight fighter. The cranked delta wing design of HAL Tejas had it's own disadvantages and even though mk1 and mk1A's design is freezed HAL needed breathing time to work on the airframe and spring out better solutions. This is an excellent strategy used by Soviet/Russian Space Agency during their times of high competition. They kept on making iterative improvements over their rocket engines and spacecrafts, as a result even modern rockets of NASA use 80’s era Russian Rocket engine's also their Soyuz Spacecraft is the most successful manned spacecraft. The LCA mk2 gives two particular opportunities to Indians first is to test out and produce 5th generation fighter capabilities like AI based swarm drones control, High end sensor fusion etc. Second opportunity is to test aerodynamic responses on airframe to use that knowledge and make a mature AMCA.
Unusual Canard Location in MK2
Everyone was surprised with this thing. A few years ago when I saw picture on defence discussion blogs about LCA getting canarded, I personally didn't believe it. Because the location of these Canards looked very creepy. Yes creepy, because we are habitual of looking at the Eurocanards like Gripen, Typhoon and Rafale. Also China's J-10. But these unusually placed Canards have their own significance. Back in time when an indegeneous Flight Control System was getting developed for LCA for the first time in India, an FCS for a non-canarded aircraft seemed less complex and that for a canarded aircraft seemed more complex for a first timer. Now that a robustly succesful FCS exists the Canarded Tejas is an iterative development. The Canards are located very closely aft of the cockpit and below the avionics bay cover. They lie in a plane above to that of the main wings. Tejas mk1 is a tailless double delta wing aircraft and the AOA of such aircrafts need to be restricted because these designs experience a ‘pitch up’ during high AOA during flight at transonic speeds. This happens due to vortex breakdown over the wing. Vortex Breakdown is an abrupt change in smooth flow structure that occurs in swirling flows and even today the mechanisms that lead to it are poorly understood.
To avoid vortex breakdown over the wing ADA studied multiple positions of Canards. These studies are revealed in research papers published by ADA over years. After multiple CFD studies the position displayed in recent pictures has been finalised as of now. This current position generates more vortices which continue upto the aft region of the wing this negates the 'pitch up’ during high AOA and allows the designers to set the airframe for a higher AOA. This is a major takeaway of adding Canards on a double delta / cranked delta aircraft.
Apart from aerodynamic considerations mentioned above there was a need for additional avionics on MWF / LCA mk2 which in turn needed more space inside the airframe. To address this requirement airframe was stretched to a length of 14.6m. The positions to be lengthend were carefully chosen, one in the nose (probably to add supportive hardware for IRST device) other behind the cockpit. These lengthening increased the weight in bow portion of fuselage and shifted CG towards the bow. To negate this extra added weight the Canards were designed to generate additional lift. For a highly maneuvreable unstable aircraft the centre of lift must be towards the bow side and centre of gravity toward aft side. This feature of instability exists in mk1 and due to Canards and extra weight in bow portion complementing each other, this feature continues in mk2 as well. Overall the mk2 has a greater lift that mk1 and this contributes to a greater payload carrying capacity. The other advantages of Canards like they act as airbrakes during landing and reduce takeoff distances, act as control surfaces …….blah blah blah……...also come along.
Naval Tejas mk2 'Tailed Delta’
This is another unusual looking aircraft. Instead of Canards the Naval designers chose to go with 'Stabilators’. The word Stabilator is a portmanteau between Stabiliser and elevator. Instead of Canards the Naval Tejas has vortex flaps which are said to be primarily intended for reducing approach speeds during a carrier landing.
Stabilators in modern avaition terminologies are also called 'all moving tail' Although stabilator existed on historic biplanes, modern supersonic fighters find their application in providing a greater degree of pitch control. Usually used on non-delta supersonic fighters the stabilators were design solution to avoid Mach Tuck. The Mach tuck is an aerodynamic effect whereby the nose of an aircraft tends to pitch downward as the airflow around the wing reaches supersonic speeds.
This happens because while approaching supersonic speed a fixed stabilator with aerodynamic shape that generates lift, moves through the air, the air flowing over the top surface accelerates to a higher local speed than the air flowing over the bottom surface. When the aircraft speed reaches its critical Mach number the accelerated airflow locally reaches the speed of sound and creates a small shock wave, even though the aircraft is still travelling below the speed of sound. The region in front of the shock wave generates high lift. As the aircraft itself flies faster, the shock wave over the wing gets stronger and moves rearwards, creating high lift further back along the wing. This rearward movement of lift causes the aircraft to tuck or pitch nose-down.
As a design correction the stabiliser is made movable so that it can move as control surface to negate any pitch down effect anytime when required.
Tejas being a delta wing Aircraft experiences Mach Tuck due to either a rearward movement of the centre of pressure of the wing and a decrease in wing downwash velocity at the tailplane both of which cause a nose down pitching moment. In all modern fighter aircrafts including Tejas, movement of stabilators aren't directly linked to Pilot's control stick but the Fly By Wire system has more authority over it. Mach Tuck is experienced only on particular delta wing designs as some other designers might choose to adjust thickness of the aerofoil, the sweep angle of the wing to negate this problem.
In Future HAL's AMCA would also feature stabilators or a more advanced control surface called tailerons. Tailerons are basically stabilators that can move differentially to perform the roll maneuvre. HAL's experiments on stabilators would make them learn more and provide knowledge for better controlability on AMCA design.
Overlapping Timelines with AMCA
Armchair experts, Facebook based bloggers, Pessimistic Indians who aspire to go to Amrika criticise every R&D effort also our dear lobbyists. All these would be very quick in undermining the R&D efforts taken by HAL and complain that LCA is a 30+ year old design, So much time has been wasted, we should focus on AMCA completely this and that. These people who can barely identify terminologies of aerodynamics, judge the development activity based on public views produced by foreign and shitty Indian media. Neither in the past people took care to admire the painstaking efforts taken by HAL to convince the IAF and MoD about the relevance of HF-24 MARUT, neither today such people would be bothering to praise innovative solutions offered by HAL. The Design and Development activity of any fighter aircraft spans through many decades refining out the best ‘ versions’ take for example F-16 evolving to F-21. Gripen, Chengdu J-10 or MiG-29 evolving into MiG-35. This long journey does not end with designing and proving just the first version of aircraft.
The Aerospace industry needs a huge overhaul for production of any Aircraft. This stage involves finding 1000s of vendors and making them technologically competent and feeding them with constant orders to keeping them financially sustained. As well as constantly help them upgrade their manufacturing capabilities so that when they have to manufacture a next generation platform the transition could be smooth. Their is a huge drama involved in almost every Indian Defence indegenisaton program, constant shifting of goal posts due to delays and further delays due to designers adjusting for a shifted goalpost. Upon that a beurecratic drama realted to funding, negative news in market spread by rival aerospace firms and all.
Making a 5th generation fighter is no joke even Japan, China and Russia are pulling up their avaition industries to their furthest extents to build 5G fighters. India's avaition industry needs to stay afloat until AMCA comes up and IAF needs a fallback to prevent them from pressuring on team AMCA to meet deadlines. The mk2 Tejas platforms would use high end sensor fusion, next generation weapons, AESA radars and AI based Swarm drones controlling and all these would straightaway taken in AMCA.
People are fantasizing 6th generation fighters and saying India’s experimentation with 4th Generation Tejas would produce a White Elephant and current models are just intended to please the public. And that mk2 Tejas won't bring any significant Capability to IAF. Such people live far away from reality. I wish the work of Fullaftetburner website helps the emancipation of avaition enthusiasts especially Indians.
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