HAL Tejas | Updates, News & Discussions-[Thread 2]

[sancho]

Don't think it is full load ....... centerline is empty ....

I guess they meant heaviest currently possible load.

i am not sure about the integration of anti ship missiles It not Certified to carry ALCM and Anti Shipping Missions or Never Performed. As far as i know

Those configs doesn't include the fuel tanks needed in every mission, therefor are unrealistic. Anti Ship missiles will be added sooner or later, most likely the Kh 35 for commonality to Mig 29Ks and Mig 29UPGs, but surely no heavy stand of missiles, because LCA would have to remove fuel tanks for that. IAF and IN have better fighters for these heavier roles.

 

[indiatester]

I guess they meant heaviest currently possible load.



Those configs doesn't include the fuel tanks needed in every mission, therefor are unrealistic. Anti Ship missiles will be added sooner or later, most likely the Kh 35 for commonality to Mig 29Ks and Mig 29UPGs, but surely no heavy stand of missiles, because LCA would have to remove fuel tanks for that. IAF and IN have better fighters for these heavier roles.

Without fuel tanks, what is the combat radius of LCA?

 

[sancho]

Without fuel tanks, what is the combat radius of LCA?

Can't tell you that, there are some figures available giving 500Km as combat range, but not in what load config and altitude. We will have to wait till the fighter is in IAF service to get more reliable figures on range.

 

[kurup]

I guess they meant heaviest currently possible load.

Is there any restriction to use the centerline ??

IIRC , they can add a sized down fuel tank .

 

[indiatester]

Can't tell you that, there are some figures available giving 500Km as combat range, but not in what load config and altitude. We will have to wait till the fighter is in IAF service to get more reliable figures on range.

But we know the internal fuel capacity is ~2500 ltrs. Can't we made a rough calculation?
I'd say roughly around 150kms (considering that with external fuel tanks its capacity is ~5000ltrs and combat radius as 300 in this case)
Either I am dumb or the range with internal fuel only seems lame
/me hides behind flame proof table

 

[sancho]

Is there any restriction to use the centerline ??

Payload!

2 x 1200l fuel tanks
1 x LDP
2 x 1000lb LGBs
2 x WVR missiles
=> around 3300Kg

Current payload limitation is 3500Kg.

But we know the internal fuel capacity is ~2500 ltrs. Can't we made a rough calculation?

As I said, the range depends on too many factors, we will have to wait for official and reliable specs to compare.

 

[greatone]

An excellent post by Indranil Roy on bharat rakshak explaining the basics of aeronautics that even a person like me who has studied maths till 10th and physics till 12th can understand.

As one increases the angle of attack of a wing, the lift and the drag increase almost monotonically (simplification) as shown by two parameters called coefficient of lift and coefficient of drag. But only to a limit (called the critical angle of a wing), at which the airflow separates (completely) from the top of the wing and wing stalls, i.e. lift falls drastically and drag increases exponentially. So there is a limit to how much lift one can generate and hence a limit to how fast a plane can turn.

Now when a fighter comes in to turn, it has a lot of initial speed, i.e. kinetic energy. So it can use its maximum lift capability to get into the tightest turn. But remember, drag also increases drastically. None of the fighters have enough thrust to overcome this level of thrust. So its energy bleeds off, i.e. its speeds falls down. This period of the turn is called the instantaneous turn and the turn rate is called instantaneous turn rate. But this can't continue forever (generally lasts a few seconds). If the speed of the aircraft continues to fall, then at some point it will go below its stall speed, i.e. it will fall to the ground like a stone. This can be overcome by losing potential energy of the plane, but in doing so you lose height i.e. become the cannon-fodder of your opponent. So to maintain a horizontal turn, the pilot has to lower the drag, i.e. decrease the lift aka lower his AoA. By how much? Till the point that the drag is balanced by the thrust of the engine. At this point, the rate of turn is decreased to the sustained rate of turn. So, the instantaneous turn rate is determined by the maximum lift generating ability of the aircraft and the propensity to reach this state as soon as possible. On the other hand, the sustained turn-rate is determined by the drag and the thrust.

The delta wing is excellent instantaneous turn-rates, because it generates large amounts of lift and naturally wants to reach higher AoA. This is because the leading edge of delta wings readily creates large vortices which add to the lift (called vortex lift). But obviously, this fast rate of turn also bleeds off the energy very fast. Beyond this point, the drag of the delta wing (at low altitudes) and slow hard turns is more than the classical wings. Therefore for maintaining the same rate of turn, a delta wing plane at low altitudes needs to have a better thrust to weight ratio.

So, we have learnt that various wings have various advantages and disadvantages. But aircraft designers have to take care of the whole flight envelop. So what should they do? They chose a design point, and make the plane excellent at that envelop around that design-point. Next they try to add things to mitigate the disadvantages at the off-design points. For example, most planes with conventional wings use LERXes with sharp edges and high sweep which generate vortices like the leading edge of a delta wing. The F-16 uses the slats and flaps as part of wings to increase its area (decrease wing-loading) etc. For delta wings, there are two primary methods:1) use a close coupled-canard and 2) use variable extended slats. A close-couple canard works by shedding a vortex which combines with the vortex of the leading edge of the delta-wing and energizes it (the exact aerodynamics is really long and winded to explain in a forum post like this). The variably-extended slats like in (Mirage 2000 and LCA) also work in the similar way. Going from the wing-root to the wing-tip, the vortices from the inner slat (at lower AoA) energizes the vortices from the outer slat (at higher AoA). I will not go into the details here because it depends on a lot of parameters like the sweep of the wing, the AoA, the sharpness of the edge etc.

In case of LCA, the wing and lift is not at all the problem. The co-efficient of lift increases monotonically till about 35 degrees of AoA. The same goes for Co-efficient of drag. The L/D ratio is one of best too by virtue of its very low wing loading. This gives it excellent ITR and roll rates. You now know that LCA would most probably be limited to 26 degree AoA, because at this AoA it generates enough lift to give it extremely good turn-rates. There is unconfirmed reports by Sjha, that it might even be taken to 28 degrees. The designers (as Maity sahab pointed out) went for a compound delta wing, where the outer part of the wing (with larger sweep) provides the capability for excellent ITR, whereas the inside of the wing helps with STR (kind of like 2-design points). The kink in the delta (can be imagined as the innermost slat with no extension) generates a vortex which energizes the vortex from the innermost actual slat, very similar to the what a fixed canard would have done. The question is how can we make the STR of LCA better. One way is to increase the thrust (brute-force), and the second way is to make it more efficient, i.e. increase the Lift-to-drag ratio. Designers of LCA Mk2 are going for both. The late Commodore says, the thrust could be increased on Mk1 (because intakes don't let the Mk1 obtained maximum thrust) and that in itself is enough.

Okay now, we come to your question. Why did Viggen have a canard in spite of having a compound a delta like Tejas. I have already answered part of that question, because it did not have independent slats like the Mirage 2000 and Tejas (though it tries to do something similar with a dogtooth). The other part of the answer lies in the plane. Remember, what I told you about the design-point. The design-point of that plane was for STOL performance. For that the plane needs to be able to turn its nose up at low speeds. But then the Viggen's elevons were attached to the end of its wings (aka with a short lever arm). So it needed secondary help (aka the canards which had flaps to provide positive lift). Another part of the answer was the Viggen's airframe itself. The Viggen was a pioneer being one of the first fighter planes to use a turbofan engine. However, given the technology of the engines then, the airframe had become very fat and bulky. If they had gone for a traditional wing, the plane would have become really fat, i.e. too much increased in wave-drag (which affects cruise-speed, range and top-speed). So, Viggen's designers (kind of) broke the wing into two wings. The smaller of the two doubles up as a canard. This kind of canard which shares the burden of generating lift along with the main wing is called a high-loaded canard. Of-course it produces other advantages (and also disadvantages).

Anyway, there are many ways of building a plane to do the same thing. Even within canards there are various ways. The canards that you see EF is a lightly-loaded canard aka a control canard, i.e. it does not produce any lift. The canard on Gripen and Rafale are mostly control canards, but can transition to a loaded canard when required (this is only possible with a FBW). For example, one can see Rafale's canards change roles while taking off from an aircraft carrier. It transitions from a control canard to a highly loaded canard soon after the plane leaves the flight deck. Also there is no silver bullet to building a plane which works exceptionally well across the entire (extremely wide) flight envelop of a modern fighter. Otherwise, all planes would have been the same. For example, three of the best designs from an aerodynamic perspective IMHO are the F-16, Mig-29 and the Rafale. These three have the cleanest airframes which use almost all the possible advantages that can be extracted out of airflows around an airplane. The Rafale is probably the best of the lot because it learned a lot from the other two. It uses the boundary layer over the wing (which the other two don't) and a complex interplay between the canard and the wing-body blend. It places its wing at the exact height where the leading edge can be extended with an extremely sharp LERX by the side of the air intake (not present in the initial prototypes). Anyways, none of these 3 look alike. Therefore, ex. AVM Matheswaran's comments can only be put down as bias. Tejas Mk1's short-comings are not a want of canard. Anybody who knows aerodynamics will tell you that easily, as has been evidenced by numerous studies. Believe it or not!

In fact I would recommend reading LCA thread from page 81 onwards

 

[greatone]

 

[Major Shaitan Singh]

https://twitter.com/x/status/552662744432771073

https://twitter.com/x/status/552663198583623680

 

[RPK]

 

[sancho]

https://twitter.com/x/status/552662744432771073

https://twitter.com/x/status/552663198583623680

Wonder what takes so long? The roll out was planned for November and the NP2 won't add much design changes to the NP1 other than hopefully a hook, so there shouldn't be a big issue to do the first flight.

 

[The enlightened]

An excellent post by Indranil Roy on bharat rakshak explaining the basics of aeronautics that even a person like me who has studied maths till 10th and physics till 12th can understand.

As one increases the angle of attack of a wing, the lift and the drag increase almost monotonically (simplification) as shown by two parameters called coefficient of lift and coefficient of drag. But only to a limit (called the critical angle of a wing), at which the airflow separates (completely) from the top of the wing and wing stalls, i.e. lift falls drastically and drag increases exponentially. So there is a limit to how much lift one can generate and hence a limit to how fast a plane can turn.

Now when a fighter comes in to turn, it has a lot of initial speed, i.e. kinetic energy. So it can use its maximum lift capability to get into the tightest turn. But remember, drag also increases drastically. None of the fighters have enough thrust to overcome this level of thrust. So its energy bleeds off, i.e. its speeds falls down. This period of the turn is called the instantaneous turn and the turn rate is called instantaneous turn rate. But this can't continue forever (generally lasts a few seconds). If the speed of the aircraft continues to fall, then at some point it will go below its stall speed, i.e. it will fall to the ground like a stone. This can be overcome by losing potential energy of the plane, but in doing so you lose height i.e. become the cannon-fodder of your opponent. So to maintain a horizontal turn, the pilot has to lower the drag, i.e. decrease the lift aka lower his AoA. By how much? Till the point that the drag is balanced by the thrust of the engine. At this point, the rate of turn is decreased to the sustained rate of turn. So, the instantaneous turn rate is determined by the maximum lift generating ability of the aircraft and the propensity to reach this state as soon as possible. On the other hand, the sustained turn-rate is determined by the drag and the thrust.

The delta wing is excellent instantaneous turn-rates, because it generates large amounts of lift and naturally wants to reach higher AoA. This is because the leading edge of delta wings readily creates large vortices which add to the lift (called vortex lift). But obviously, this fast rate of turn also bleeds off the energy very fast. Beyond this point, the drag of the delta wing (at low altitudes) and slow hard turns is more than the classical wings. Therefore for maintaining the same rate of turn, a delta wing plane at low altitudes needs to have a better thrust to weight ratio.

So, we have learnt that various wings have various advantages and disadvantages. But aircraft designers have to take care of the whole flight envelop. So what should they do? They chose a design point, and make the plane excellent at that envelop around that design-point. Next they try to add things to mitigate the disadvantages at the off-design points. For example, most planes with conventional wings use LERXes with sharp edges and high sweep which generate vortices like the leading edge of a delta wing. The F-16 uses the slats and flaps as part of wings to increase its area (decrease wing-loading) etc. For delta wings, there are two primary methods:1) use a close coupled-canard and 2) use variable extended slats. A close-couple canard works by shedding a vortex which combines with the vortex of the leading edge of the delta-wing and energizes it (the exact aerodynamics is really long and winded to explain in a forum post like this). The variably-extended slats like in (Mirage 2000 and LCA) also work in the similar way. Going from the wing-root to the wing-tip, the vortices from the inner slat (at lower AoA) energizes the vortices from the outer slat (at higher AoA). I will not go into the details here because it depends on a lot of parameters like the sweep of the wing, the AoA, the sharpness of the edge etc.

In case of LCA, the wing and lift is not at all the problem. The co-efficient of lift increases monotonically till about 35 degrees of AoA. The same goes for Co-efficient of drag. The L/D ratio is one of best too by virtue of its very low wing loading. This gives it excellent ITR and roll rates. You now know that LCA would most probably be limited to 26 degree AoA, because at this AoA it generates enough lift to give it extremely good turn-rates. There is unconfirmed reports by Sjha, that it might even be taken to 28 degrees. The designers (as Maity sahab pointed out) went for a compound delta wing, where the outer part of the wing (with larger sweep) provides the capability for excellent ITR, whereas the inside of the wing helps with STR (kind of like 2-design points). The kink in the delta (can be imagined as the innermost slat with no extension) generates a vortex which energizes the vortex from the innermost actual slat, very similar to the what a fixed canard would have done. The question is how can we make the STR of LCA better. One way is to increase the thrust (brute-force), and the second way is to make it more efficient, i.e. increase the Lift-to-drag ratio. Designers of LCA Mk2 are going for both. The late Commodore says, the thrust could be increased on Mk1 (because intakes don't let the Mk1 obtained maximum thrust) and that in itself is enough.

Okay now, we come to your question. Why did Viggen have a canard in spite of having a compound a delta like Tejas. I have already answered part of that question, because it did not have independent slats like the Mirage 2000 and Tejas (though it tries to do something similar with a dogtooth). The other part of the answer lies in the plane. Remember, what I told you about the design-point. The design-point of that plane was for STOL performance. For that the plane needs to be able to turn its nose up at low speeds. But then the Viggen's elevons were attached to the end of its wings (aka with a short lever arm). So it needed secondary help (aka the canards which had flaps to provide positive lift). Another part of the answer was the Viggen's airframe itself. The Viggen was a pioneer being one of the first fighter planes to use a turbofan engine. However, given the technology of the engines then, the airframe had become very fat and bulky. If they had gone for a traditional wing, the plane would have become really fat, i.e. too much increased in wave-drag (which affects cruise-speed, range and top-speed). So, Viggen's designers (kind of) broke the wing into two wings. The smaller of the two doubles up as a canard. This kind of canard which shares the burden of generating lift along with the main wing is called a high-loaded canard. Of-course it produces other advantages (and also disadvantages).

Anyway, there are many ways of building a plane to do the same thing. Even within canards there are various ways. The canards that you see EF is a lightly-loaded canard aka a control canard, i.e. it does not produce any lift. The canard on Gripen and Rafale are mostly control canards, but can transition to a loaded canard when required (this is only possible with a FBW). For example, one can see Rafale's canards change roles while taking off from an aircraft carrier. It transitions from a control canard to a highly loaded canard soon after the plane leaves the flight deck. Also there is no silver bullet to building a plane which works exceptionally well across the entire (extremely wide) flight envelop of a modern fighter. Otherwise, all planes would have been the same. For example, three of the best designs from an aerodynamic perspective IMHO are the F-16, Mig-29 and the Rafale. These three have the cleanest airframes which use almost all the possible advantages that can be extracted out of airflows around an airplane. The Rafale is probably the best of the lot because it learned a lot from the other two. It uses the boundary layer over the wing (which the other two don't) and a complex interplay between the canard and the wing-body blend. It places its wing at the exact height where the leading edge can be extended with an extremely sharp LERX by the side of the air intake (not present in the initial prototypes). Anyways, none of these 3 look alike. Therefore, ex. AVM Matheswaran's comments can only be put down as bias. Tejas Mk1's short-comings are not a want of canard. Anybody who knows aerodynamics will tell you that easily, as has been evidenced by numerous studies. Believe it or not!

In fact I would recommend reading LCA thread from page 81 onwards

Holy shit. On that site for the 1st time. I have to say that PDF sucks in comparison.

 

[sancho]

Holy shit. On that site for the 1st time. I have to say that PDF sucks in comparison.

Depends on what you want, if you want a wider and less biased perspective on Pakistani and Chinese arms and systems, PDF has no comparison. That with a very good Indian section too, not to mention the huge collection on infos Manticore has provided here:

Design characteristics of canard & non canard fighters

Air Warfare


BR offers good infos on Indian forces and arms though.

 

[Mujraparty]

A Tejas-PV1 light combat aircraft with an advanced electronic warfare suite with in-built jammer flew for the first time here.

It gives the pilot an additional capability of nullifying the effect of detected radar threat by appropriate mode of jamming.

Existing EW systems fitted on various combat aircraft are basic EW equipment known as Radar Warner Receiver to provide warning to the aircraft pilot in case of detection of a radar threat, an official statement said.

After obtaining due flight clearances and certification, the first flight sortie of LCA PV1 with the EW equipment operational, took place here today.

The equipment was noted to be detecting radar signals operating in and around the flight path.

DRDO chief Avinash Chander congratulated the team on the achievement and said "this warfare suite adds an important capability to our LCA".

It is the first fighter aircraft of India fitted with a radar warner and jammer equipment.
Tejas with radar jammer flies maiden sortie | Business Standard News

HYDERABAD, JAN 10:


The fighting power of the Light Combat Aircraft (LCA), Tejas has been sharpened with the aircraft being equipped with an advanced electronic warfare suite (EW suite).

The system was flight tested today in Bengaluru for the first time onboard the Tejas-PV1 combat aircraft, according to an announcement by the Defence Research and Development Organisation (DRDO) official.

The Suite has been developed by Defence Avionics Research Establishment (DARE), a lab specialising in avionics and electronic warfare systems for combat aircrafts.

In addition to the Radar Warner, the EW suite tested today is also equipped with Jammer. It gives the pilot an additional capability of nullifying the effect of detected Radar threat by appropriate mode of jamming. Existing EW systems fitted on various combat aircrafts are basic EW equipment known as Radar Warner Receiver to provide warning to the aircraft pilot in case of detection of a Radar threat.

After obtaining due flight clearances and certification, the first flight sortie of LCA PV1 with the EW equipment operational, took place today. The equipment was noted to be detecting Radar signals operating in and around the flight path.

Avinash Chander, Scientific Advisor to Raksha Mantri, Secretary Department of Def. R&D & DG, DRDO said "This warfare suite adds an important capability to our LCA."

J Manjula, Director DARE said "LCA is the first fighter aircraft of India fitted with a radar warner and jammer equipment. It has capability for both radar warning and jamming using a Unified EW Technology. Over the coming few months, ADA and DARE will be scheduling further sorties to evaluate the system in various signal scenarios".

Tejas with radar jammer flies maiden sortie | Business Standard News

 

[gslv mk3]

With Full Load

3 segment slats ??