ADA Tejas (LCA) News and Discussions

[ersakthivel]

most beautiful image of tejas , I suppose.

 

[ersakthivel]

If you do a bit of research on aircraft design for low weight and low drag plan forms, you will find that LCA is the worst design for a light weight fighter. Also the sweep angle of this ac is the main problem for it being over weight. A tailless delta with sweep angle of 53* is probably the worst design that one shud look to put on a carrier.

in Fig. 6 for angle of attack a = 13° and 18° . A fairly goodcomparison is observed. The vortical flow field capturedin calculations is presented in Fig. 7. The particle tracesillustrate the detailed structure of the rolled-up vortices.It is seen that the leading edge vortices are strengthenedas the flow develops progressively away from the leading-edge of the win

To generate large lift inducing vortices the wing of Tejas was designed with a crank or compound delta model, along with the twist in wing root.

You can obsever the the lift inducing vortices generated by this compound delta +wingroot twist+curvarute of the wing resulting in large beneficial lift inducing vortices benefitting Tejas in vertical maneuvers.

These lift inducing vortices delay the onset of stall.

 

[ersakthivel]

That was the reason ADA chose the impressive F-16 XL's cranked delta wing form. F-16 Xl has a crank at the edge of the wing.

The wing and rear horizontal control surfaces were replaced with a cranked-arrow delta wing 120% larger than the original wing. Extensive use of carbon fiber composites allowed the savings of 600 lb (270 kg) of weight but the F-16XL was still 2,800 lb (1300 kg) heavier than the original F-16A.
Less noticeable is that the fuselage was lengthened by 56 in (1.4 m) by the addition of 2 sections at the joints of the main fuselage sub-assemblies. With the new wing design, the tail section had to be canted up 3°, and the ventral fins removed, to prevent them from striking the pavement during takeoff and landing. However, as the F-16XL exhibits greater stability than the native F-16, these changes were not detrimental to the handling of the aircraft.
These changes resulted in a 25% improvement in maximum lift-to-drag ratio in supersonic flight and 11% in subsonic flight, and a plane that reportedly handled much smoother at high speeds and low altitudes. The enlargements increased fuel capacity by 82%. The F-16XL could carry twice the ordnance of the F-16 and deliver it 40% further. The enlarged wing allowed a total of 27 hardpoints:
16 wing stations of capacity 750 lb (340 kg) each
4 semi-recessed AIM-120 AMRAAM stations under fuselage
2 wingtip stations
1 centerline station
2 wing "heavy/wet" stations
2 chin LANTIRN stations

The Revolutionary Evolution of the F-16XL

Two additional capabilities of the F-16XL contribute to survivability. First is improved instantaneous maneuver ability coupled with greatly expanded flight operating limits (with bombs), and second is reduced radar signature resulting from the configuration shaping.


For a decade and a half, many fighter tacticians have stressed the paramount importance of being able to sustain a high turn rate at high Gs. The rationale was that with such a capability, enemy aircraft that cannot equal or better the sustained turn rate at high Gs could not get off a killing shot with guns or missiles.


With developments in missiles that can engage at all aspects, and as a result of having evaluated Israeli successes in combat, the tacticians are now leaning toward the driving need for quick, high-G turns to get a "first-shot, quick-kill" capability before the adversary is able to launch his missiles. This the F-16XL can do. Harry Hillaker says it can attain five Gs in 0.8 seconds, on the way to nine Gs in just a bit more time. That's half the time required for the F-16A, which in turn is less than half the time required for the F-4. The speed loss to achieve five Gs is likewise half that of the F-16A.


All of these apparent miracles seem to violate the laws of aerodynamics by achieving greater range, payload, maneuverability, and survivability. Instead, they are achieved by inspired design, much wind-tunnel testing of shapes, exploitation of advanced technologies, and freedom from the normal contract constraints.


The inspired design mates a "cranked-arrow" wing to a fifty-six inch longer fuselage. The cranked-arrow design retains the advantages of delta wings for high-speed flight, but overcomes all of the disadvantages by having its aft portion less highly swept than the forward section. It thus retains excellent low-speed characteristics and minimizes the trim drag penalties of a tailless delta.


Although the wing area is more than double that of the standard F-16 (633square feet vs. 300 square feet), the drag is actually reduced.
Although the wing area is more than double that of the standard F-16 (633square feet vs. 300 square feet), the drag is actually reduced.

The skin friction drag that is a function of the increased wetted (skin surface) area is increased, but the other components of drag (wave, interference, and trim) that are a function of the configuration shape and arrangement are lower so that the "clean airplane" drag is slightly lower during level flight, and forty percent lower when bombs and missiles are added.

And although the thrust-to-weight (T/W) ratio is lower due to the increased weight, the excess thrust is greater because the drag is lower – and excess thrust is what counts.

 

[Decklander]

The two basic reasons for the outstanding performance of F-16XL were the large wing area and 3* canted tail which caused the thrustline to go below the C of G of the aircraft there by giving it a nose up thrust vector obviating the need for elevators to compensate for strong nose down pitch moment of the wing in flight at high speeds which is hall mark of such cranked delta planforms. It was for this reason that F-16XL was the first ac in the world to supercruise. This low thrustline also gives outstanding take off performance as it effectively adds to the elevator authority.

 

[ersakthivel]

The two basic reasons for the outstanding performance of F-16XL were the large wing area and 3* canted tail which caused the thrustline to go below the C of G of the aircraft there by giving it a nose up thrust vector obviating the need for elevators to compensate for strong nose down pitch moment of the wing in flight at high speeds which is hall mark of such cranked delta planforms. It was for this reason that F-16XL was the first ac in the world to supercruise. This low thrustline also gives outstanding take off performance as it effectively adds to the elevator authority.

what is the need for relaxed static stability?

In old fighter designs due to the requirements of good tree top flying to avoid the radar and need to drop the bombs closer to the target,since there were no GPS guided long range stand off weapons, wings were small in width and length.

Because of this most of the weight of the fighter is packed in fuselage making fuselage very heavier with engine fuel in clean config flight.Most of them carried heavy machine guns in the nose and some low weight gravity bombs in the wing to drop close to the target.

Earlier versions of supersonic fighters also carried this wing load out to to avoid it's wing area to be subjected to shock waves out side supersonic cone area. And since lift was not enough , the concept of deltas enclosing the larger area within the super sonic shock cone came into effect. That's why deltas have high sweeps in excess of 50 degs.

Because of this fuselage became heavy and as a result of this it's inertia opposed the pilot's desire for quick nose pitching vertical ups and downs.

Only to sort out this problem Relaxed or negative static stability design came into vogue.

This concept essentially means placing the center of gravity behind the center of lift to create a pitch up moment and to avoid the pitch up momentum fighters needed digital FBW which will adjust the control surfaces many times in a second in various combinations in level flight.because the pilot cannot perform the operation of the stick 10 or more times in a second.

What counts for the super agility of the relaxed static stability fighters is whether the center of gravity is behind the center of lift to create a pitch up movement . Not whether the center of gravity is above or below the center of lift.

As long as the nose pitches up the fighter will have tighter vertical turns and tighter horizantal turns on the Knife edge position of the wing i.e the wings at 90 deg angle to the ground level,

 

[Decklander]

what is the need for relaxed static stability?

In old fighter designs due to the requirements of good tree top flying to avoid the radar and need to drop the bombs closer to the target,since there were no GPS guided long range stand off weapons, wings were small in width and length.

Because of this most of the weight of the fighter is packed in fuselage making fuselage very heavier with engine fuel in clean config flight.Most of them carried heavy machine guns in the nose and some low weight gravity bombs in the wing to drop close to the target.

Earlier versions of supersonic fighters also carried this wing load out to to avoid it's wing area to be subjected to shock waves out side supersonic cone area. And since lift was not enough , the concept of deltas enclosing the larger area within the super sonic shock cone came into effect. That's why deltas have high sweeps in excess of 50 degs.

Because of this fuselage became heavy and as a result of this it's inertia opposed the pilot's desire for quick nose pitching vertical ups and downs.

Only to sort out this problem Relaxed or negative static stability design came into vogue.

This concept essentially means placing the center of gravity behind the center of lift to create a pitch up moment and to avoid the pitch up momentum fighters needed digital FBW which will adjust the control surfaces many times in a second in various combinations in level flight.because the pilot cannot perform the operation of the stick 10 or more times in a second.

What counts for the super agility of the relaxed static stability fighters is whether the center of gravity is behind the center of lift to create a pitch up movement . Not whether the center of gravity is above or below the center of lift.

As long as the nose pitches up the fighter will have tighter vertical turns and tighter horizantal turns on the Knife edge position of the wing i.e the wings at 90 deg angle to the ground level,

I wud suggest that you read some more on RSS and stability as such. Every RSS ac has regimes in which it is positively stable or negatively stable or neutral stability. RSS does not add in any way add to the turn performance of an aircraft which remains dependent on just speed and angle bank only. Please read the turn equation of an aircraft and tell me where do you fing stability a factor? RSS helps by allowing a higher rate of pitch up in longitudinal axis around lateral axis of an ac.
You also need to understand the relationship of C of G with C of P and also how the stability is affected if the C of G is above or below the center of Pressure and also the effect of thrustline on stability of an aircraft.
Just to give you an hint, why do we have pitch down moment when we open thrust or how is the stability of an aircraft affected with low wing or high wing? Why do we resort to anhederal or dihederal?
please read about them.
Lastly, the americans are masters of selling shit at the price of gold. One such shit is this idea of RSS. F-15 is the fighter till date in the world and is a conventional stable non FBW design and also without this so called RSS.
For you RSS may mean Relaxed static stability for its repeatedly sold shit.

 

[ersakthivel]

I wud suggest that you read some more on RSS and stability as such. Every RSS ac has regimes in which it is positively stable or negatively stable or neutral stability. RSS does not add in any way add to the turn performance of an aircraft which remains dependent on just speed and angle bank only. Please read the turn equation of an aircraft and tell me where do you fing stability a factor? RSS helps by allowing a higher rate of pitch up in longitudinal axis around lateral axis of an ac.
You also need to understand the relationship of C of G with C of P and also how the stability is affected if the C of G is above or below the center of Pressure and also the effect of thrustline on stability of an aircraft.
Just to give you an hint, why do we have pitch down moment when we open thrust or how is the stability of an aircraft affected with low wing or high wing? Why do we resort to anhederal or dihederal?
please read about them.
Lastly, the americans are masters of selling shit at the price of gold. One such shit is this idea of RSS. F-15 is the fighter till date in the world and is a conventional stable non FBW design and also without this so called RSS.
For you RSS may mean Relaxed static stability for its repeatedly sold shit.

Generally high wing loading fighters have better sustained turn radius, Is that right ?

The F-15 has an instantaneous [turn rate] of 21 [degrees] and a sustained [turn rate] of about 17 degs at corner speeds of 350 knots degrees. At speeds of 200 knots it has around 21 deg per sec sustained turn rate.

Only at low speeds of below 200 knots F-15 has 21 deg sustained rate.

. Is this right?

It is no world beating performance.

The repeatedly sold shit(as you describe the RSS) F-16 can do much better STR than conventional stable non FBW design and also without this so called RSS F-15?

Do you agree or not? .

http://www.eurofighter.com/capabilities/performance/aerodynamic-characteristics.html

Eurofighter Typhoon has a foreplane/delta configuration which is, by nature, aerodynamically unstable.

The instability of the aircraft is derived from the position of a theoretical "pressure point" on the longitudinal axis of the aircraft. This is calculated from the contribution to lift from each of the aircraft components (the wings, the canards, fuselage etc). If the pressure point is in front of the centre of gravity on the longitudinal axis, the aircraft is aerodynamically unstable and it is impossible for a human to control it.

With the Eurofighter Typhoon, in subsonic flight the pressure point lies in front of the centre of gravity, therefore making the aircraft aerodynamically unstable, and is why Eurofighter Typhoon has such a complex Flight Control System – computers react quicker than a pilot.

When Eurofighter Typhoon crosses into supersonic flight, the pressure point moves behind the centre of gravity, giving a stable aircraft.

The advantages of an intentionally unstable design over that of a stable arrangement include greater agility – particularly at subsonic speeds - reduced drag, and an overall increase in lift (also enhancing STOL performance).

Not so surprisingly the guys at the Eurofighter think very differently about Repeatedly Sold Shit i.e Relaxed static stability(RSS)

 

[ersakthivel]

The repeatedly sold shit RFALE has an instantaneous turn rate of 32 to 35 deg and
a sustained turn rate of 24 deg,

The repeatedly sold shit TYPHOON has an instantaneous turn rate of 30 to 35 deg and
a sustained turn rate of 20-25 deg,

can the conventional stable non FBW design and also without this so called RSS F-15 match them?

Even tejas completed a vertical loop in Aeroindia under 20 seconds within this restricted flight envelope opening of 6Gs and 22 deg AOA,

STR comes to 18 deg per second for the above loop. It will improve with AOA opening to 24-26 deg and 8G limits.

Better than F-15 at corner speeds.

 

[Decklander]

You have not answered any of my questions here. The rate of turn and radius of turn are not at all dependent on RSS. They are dependent on only bank angle and speed. ITR by definition is the rate of turn which an aircraft can maintain without loosing speed. The wingloading as such has no role to play as long as the aircraft is able to generate the lift to maintain best turn rate lift. The higher thrust of engines of F-15 adds to the winglift at high AOA and that is one of the reasons for Raptor,Typhoon and Rafale also. Please check the TWR of these aircraft w.r.t F-15 & F-18 and you will know the reason. In a balanced turn you have to overcome centrifugal force by winglift which is directed towards the centre of the circle. This lift is provided by wings and engines. An ac with low wingloading with high TWR will have very high ITR & STR and Repeatedly Sold Shit has no bearing on that. If someone has told you that RSS gives better maneuoverability than he is just making a fool of you. RSS only provides a higher pitch up rate and nothing else and that too only within a very controlled regime of flight as each RSS ac has negative stability at low speeds, nearly neutral at 0.9M and positive stability in supersonic regimes.
Now can you tell me as to why RSS tailless Delta have lower approach speeds compared to other ac?

 

[ersakthivel]

You have not answered any of my questions here. The rate of turn and radius of turn are not at all dependent on RSS. They are dependent on only bank angle and speed. ITR by definition is the rate of turn which an aircraft can maintain without loosing speed. The wingloading as such has no role to play as long as the aircraft is able to generate the lift to maintain best turn rate lift. The higher thrust of engines of F-15 adds to the winglift at high AOA and that is one of the reasons for Raptor,Typhoon and Rafale also. Please check the TWR of these aircraft w.r.t F-15 & F-18 and you will know the reason. In a balanced turn you have to overcome centrifugal force by winglift which is directed towards the centre of the circle. This lift is provided by wings and engines. An ac with low wingloading with high TWR will have very high ITR & STR and Repeatedly Sold Shit has no bearing on that. If someone has told you that RSS gives better maneuoverability than he is just making a fool of you. RSS only provides a higher pitch up rate and nothing else and that too only within a very controlled regime of flight as each RSS ac has negative stability at low speeds, nearly neutral at 0.9M and positive stability in supersonic regimes.
Now can you tell me as to why RSS tailless Delta have lower approach speeds compared to other ac?

What is the reason for the introduction of fly by wire tech in Mirage-2000?

This according to wiki,

In that summer, at the Farnborough Airshow, this machine displayed not only excellent handling capabilities, but also a full control at 204 km/h and 26 degree angle of attack. This was totally unexpected in a delta-wing fighter, and proved how CCD controls were capable of overcoming the delta wing shortcomings related to poor low-speed control, while retaining the advantages, such as low-drag, low radar cross section, ideal high speed aerodynamics and simplicity, provided by the absence of horizontal tail surfaces.[citation needed] The Mirage 2000 was one of the stars of that airshow and became the direct adversary for the F-16, which shared the CCD control and relaxed stability.

The Mirage 2000 features a low-set thin delta wing with cambered section, 58 degrees leading-edge sweep and moderately blended root; area-ruled; two small canard wings, fixed, placed just behind the air intakes. The flight controls on the wings are: four elevons (+15/−30°), four slats.

Its neutral point is in front of its center of gravity, giving the fighter relaxed stability to enhance maneuverability. It incorporated negative stability and fly-by-wire controls with four analog computers.[9] An airbrake is fitted above and below each wing in an arrangement very similar to that of the Mirage III. A noticeably taller tailfin allows the pilot to retain control at higher angles of attack, assisted by the small strakes mounted along each air intak

 

[Decklander]

What is the reason for the introduction of fly by wire tech in Mirage-2000?

This according to wiki,

You know that CG moves with weaponload and fuel burnt and we also have a clean ac CG. Similarly the neutral point also has a clean ac value and a loaded value. The CP moves with AOA only.
FBW provides a very rapid and precise positioning of controls as the FBW computer has a memory of its own and at any given time knows what is needed to keep the ac in check.
the negative stability at low speeds and during approach needs the elevons to deflect downwards to provide a pitch down moment and that effectively converts them to full span flaps.

 

[ersakthivel]

You know that CG moves with weaponload and fuel burnt and we also have a clean ac CG. Similarly the neutral point also has a clean ac value and a loaded value. The CP moves with AOA only.
FBW provides a very rapid and precise positioning of controls as the FBW computer has a memory of its own and at any given time knows what is needed to keep the ac in check.
the negative stability at low speeds and during approach needs the elevons to deflect downwards to provide a pitch down moment and that effectively converts them to full span flaps.


The two basic reasons for the outstanding performance of F-16XL were the large wing area and 3* canted tail which caused the thrustline to go below the C of G of the aircraft there by giving it a nose up thrust vector obviating the need for elevators to compensate for strong nose down pitch moment of the wing in flight at high speeds which is hall mark of such cranked delta planforms. It was for this reason that F-16XL was the first ac in the world to supercruise. This low thrustline also gives outstanding take off performance as it effectively adds to the elevator authority.


The rate of turn and radius of turn are not at all dependent on RSS. They are dependent on only bank angle and speed.

To get to the bank angle quickly and retain it continuously in sustained turn The fighters like F-16 and Mirage depend upon the relaxed static stability-RSS.

if they are stable flight profile fighters with positive stability , then because of the CG going in front of the center of lift , they will have to encounter a resistance of nose down momentum of this non-RSS configuration.

The reason that they achieve consistent high bank angle, high AOA and speed on the knife edge is(a combination called high alpha performance), they are Negative or Relaxed Stability fighters. with CG behind the center of the lift providing constant natural nose pitch up momentum allowing the fighter to achieve high bank angles and high speeds simultaneously.

That's why relaxed static stability low wing loading deltas have high ITR and high Alpha performance, easily bettering the STR and ITR of fighters like F-15 in STR and ITR. Because F-15 doesnot have this RSS-Negative static stability and belong to the old school of Positive static stability fighters.

That's why from the advent of Mirage and F-16 every single fighter that is called cutting edge 4.5th gen is a RSS fighter.

Decklander ↑

The point I want to stress is both mirage and F-16 XL had similar thrust lines . Still both of them went for negative static stability RSS for agillity and control at low speeds.

But you are saying if thrust line well below the CG , large wing area and 3* canted tails in F-16 XL are the three reason for the superior performance, and no need for RSS

. But still both of them went for RSS.
WHY?

 

[Decklander]

You can have RSS with thrustline below CG based on your design. Using thrustline as an addition to stab authority has far more advantages than using RSS. The job which the elevons do for a highly swept Delta RSS design is done by the thrustline as the part of thrust adds to lift. Take a case a 3* lower thrustline adds sin3* of total thrust to the elevator authority for pitch moment. This increases with thrust applied and at any stage if the ac is about to go out of control, you can just throttle back. The FBW is not the best solution in terms of reducing weight of FCS for a RSS FBW ac. But use of thrustline is.
When you go to combat, you go in with max thrust and stick back in your stomach.

 

[Decklander]

The point I want to stress is both mirage and F-16 XL had similar thrust lines. Still both of them went for negative static stability RSS for agillity and control at low speeds.

But you are saying if thrust line well below the CG , large wing area and 3* canted tails in F-16 XL are the three reason for the superior performance, and no need for RSS

. But still both of them went for RSS.
WHY?

Only ac till date in the world to utilize this thrustline design has been F-16XL. M2K does not have it.

 

[WMD]

Stealth and Tejas

Given its small size anyway, it's "virtually invisible" to adversary fighter; were how a Tejas Test pilot described Tejas RCS signature. Use of carbon fibre gives Tejas natural stealth characteristics and advantage of low operating costs, use of carbon fibre composites (CFC) gives Tejas 45 percent content by weight and 90 per cent of its surface is made of carbon fibres, Carbon fibre doesn't make aircraft stealthily but reflection of radar beams by CFC is much less when compared to metallic components in the aircrafts but CFC with Radar-absorbent material coating and given the smaller size of aircraft gives Tejas low radar signature or stealth characteristics .

Expert believe that RCS of Tejas is three times smaller than a Mirage-2000, but it might be speculation since official RCS figure of Tejas has never been made available in public domain, CFC have other advantages they don't deteriorate with age nor corrode due weather elements, CFC also gives Tejas better operational empty weight giving Tejas better thrust to weight ratio when compared with other aircrafts with similar engines. CFC does have their own disadvantages, there are expensive to make but India has already invested heavily in development of CFC making it among the best in CFC technology in the world.

Sensing an opportunity and possibility of further reduction in radar signature of Tejas, DRDO has put towed with idea of development of Tejas MK-3 with better improvements and lowering its radar signatures, DRDO plans to use up to 70 percent of CFC in Tejas MK-3 up from 45 percent currently used in Tejas MK-1. DRDO also plans to focus on reducing infrared signature of the aircraft by reducing exhaust temperatures from the engine, to make Tejas MK-3 near Stealth aircraft DRDO also plans to improve fuselage and improve engine ducts to achieve low radar signature.

Research work carried out on AMCA will help in development of Tejas MK-3 and MK-3 will also benefit in avionics development which according to DRDO will borrow heavily from AMCA. Two current projects on Stealth front headed by DRDO are development of Stealth aircraft AMCA and development of unmanned combat aircraft Aura, MK3 likely will be testbed for such development and technology developed will benefit all three projects in long term in future.

Stealth and Tejas | idrw.org

 

[Kunal Biswas]

So, Tejas MK3 was not a Hoax after all ..

Sensing an opportunity and possibility of further reduction in radar signature of Tejas, DRDO has put towed with idea of development of Tejas MK-3 with better improvements and lowering its radar signatures, DRDO plans to use up to 70 percent of CFC in Tejas MK-3 up from 45 percent currently used in Tejas MK-1. DRDO also plans to focus on reducing infrared signature of the aircraft by reducing exhaust temperatures from the engine, to make Tejas MK-3 near Stealth aircraft DRDO also plans to improve fuselage and improve engine ducts to achieve low radar signature.

 

[ersakthivel]

Only ac till date in the world to utilize this thrustline design has been F-16XL. M2K does not have it.

1.Explain what do you men by thrust line in your own words and , and how is it's relationship works with center of lift works in subsonic and supersonic flights,

2.And also since the center of gravity of the fighter changes with depletion of fuel depletion of external stores like fuel in drop tanks , inside the fighter and bombs and missiles ejected,Since Cg changes with all those activities , how do you propose to keep the center of lift just above the CG all time.

3. And also explain how this CG change can be counter acted by lower thrust line of F-16 XL without RSS ,while both the center of lift and Center of gravity keeps changing?

4. As you say turn rate is determined by just bank angle and speeds and it has no relation with RSS, I completely accept it.

5.But My point is to achieve this bank angle quickly and keep it up all the time with least force couple based momentum resistance of Cg the figter has no other way other than having RSS.

6.RSS planes have their Cg behind Cl in sub sonic and near trans sonic flight at their corner velocity. That is the reason F-16 has better STR than F-15 irrespective of F-15 being much bigger and having two powerful engines.The F-15 is not an RSS plane means it's center of lift is behind CG in corner velocity, unlike the Eurofighter TYPHOON.

What this means is during cornering at around 300 +knots it's Cg being in front of the Cl produces a downward force couple all the time. That is the reason Why F-15 despite being a much bigger twin engined plane is unable to achieve high STR of F-16 A.Remember both the F-15 and F-16 belong to the same low wing area , high wing loading concept.

It has been embarasingly proved many times in USAF exercise that F-16 is more agile than F-15. But since F-15 is a much bigger load carrying heavier long range interceptor with much high standards of BVRs and RADAR and electronic counter measures it's position as premier fighter was unchallenged. But this doesnot mean that it's non-RSS airframe design is superior to F-16's RSS airframe.

But still F-16 excels with high STR of 23 + degree at corner speeds and F-15 lags behind with poor 15 to 17 deg STR in corner speeds means F-16 is RSS and F-15 is the old conventional stable flight profile with positive static stability meaning the airframe resists the attempts of the pilot to maneuver and tries to stay level, which is not the case with RSS F-16 which goes with the pilot's effort to maneuver , because it is RSS based negative static stability platform.

also there is a small matter called force couple, which get generated by the distance between the CG and CL. Cg tries to pull the plane down with nose down momentum, Cl tries to lift the plane up. IF both are at the same exact place , no force couple arise.

But it is impossible to keep it that way all the time as the fighter maneuvers all the time and changes to super sonic and subsonic flight all the time resulting in changes in CL and with the reduction of fuel and external stores it's Cg too changes place. How do you propose to keep both of them at the same place with thrust line or CL just below the Cg all the time?

In RSS aerodynamic layout this force couple actually benefits the fighter, because the CG which tries to pull down the plane due to gravity is below the Cl which pushes the plane up. A force couple is generated that results in the nose pitch up momentum of the airframe. That is why it is described in all articles that describe the tejas's aerodynamic loadout that it has a tendency to pitch up the nose.

It is this nose pitch up momentum which results in achieving Gs faster and reaching it's higher AOA limit faster. Coupled with the fabulous wing loading of Tejas it results in attaining a high ITR pulling GS faster and getting a firing solution with HMDS enabled high of bore sight WVR missiles in close combat.

Through out the Sustained turn this force couple between the CL which is infront and Cg which is in the back acts on the airframe making it sustain the Bank angle or AOA at it's top limit with no opposition and little effort. But for non RSS fighter the it is exactly the opposite , that is the CL in the back and the CG in the front creates a negative force couple resisting the aerodynamic lift work done by the wings to achieve high ITR and high AOA along with high STR,

This is the reason RAFALE and TYPHOON have both high ITR and STR than the F-15 irrespective of the TWR.



You are welcome to contradict and put your explanations against the points I have made here. As I believe every one learns something from a lively debate conducted with proper decorum,instead of each throwing challenges to other like those in the teenage fast dance movies of the Hollywood genre.

 

[ersakthivel]

EDIT, for the above post no-958.

Errr, there are few words mis typed in my above post the correction is,

1.Explain what do you MEAN by thrust line in your own words and , and how is it's relationship works with center of lift ,which keeps moving places in subsonic and supersonic flights,

2.And also since the center of gravity of the fighter changes with depletion of fuel, depletion of external stores like fuel in drop tanks , inside the fighter and bombs and missiles ejected,Since Cg changes with all those activities , how do you propose to keep the center of lift or thrust line just BELOW the CG all time.

 

[ersakthivel]

Making of Super Tejas (MK-2) | idrw.org

So it proves everything said about the reason behind the development of tejas mk-2,like

The mk-1 alone has exceeded the original ASR, Because the navy wanted a much powerful carrier variant IAF also joined the effort, which is commonsense afterall,

Now people claiming that mk-1 failed to meet the original ASR and that was why mk-2 was developed have a lot on their hands to prove their arguments.

 

[shashi]

Tejas mark 3 with a twin engine delta design and 2 kaveri engines might just do the trick ! Just Wishful Thinking!