LCA News and Discussions

[Victor]

I wonder what kind of 'nose droop' is being contemplated for the NLCA, the actuating type as in the Backfire bomber and Concorde or the fixed type as in the Su30mki. The former seems unlikely because of the complex actuating mechanism and overlapping fuselage sections that would be required along with the added weight. So more likely it will be the fixed droop. Both will change the aerodynamics during the critical landing approach and will need to be tested. If this is what ADA has in mind then IMO it should be made standard for both NLCA and LCA2, along with the LEVCON. For a short range fighter, the capability of operating on short stretches of highway would be a plus during wartime if frontline runways are bombed and unusable.

[Victor]

4. The limiting factor is the yaw control authority. The rudder gives good control authority till 24(22?) degrees. But it can be artificially stabilized till about 26 degrees (FOC objective).

The rudder/tail being 'hidden' from airflow behind the plane at high AoA is why some fighters like F-18, F-35, MiG-29 have twin and outward canted vertical fins. They can also aid high AoA/pitch by both being turned inwards. ADA must have considered this option too.

[suryag]

Meanwhile ...
Flight test update

From

LCA-Tejas has completed 2235 Test Flights Successfully. (25-June-2013).
(TD1-233,TD2-305,PV1-242,PV2-222,PV3-365,LSP1-74,LSP2-273,PV5-36,LSP3-144,LSP4-86,LSP5-188,LSP7-48,NP1-4,LSP8-15)

to

LCA-Tejas has completed 2242 Test Flights Successfully. (27-June-2013).
(TD1-233,TD2-305,PV1-242,PV2-222,PV3-365,LSP1-74,LSP2-274,PV5-36,LSP3-147,LSP4-87,LSP5-190,LSP7-48,NP1-4,LSP8-15)

Just curious what happened to the trainer bird, why is it grounded for so long without anyone talking about it?

[Sagar G]

Or ask the authors for a copy. The Journals should not mind that - or at least they never used to mind that.

Alternatively the authors can publish the paper in an Indian journal.

Or check with your local/college library, they may (mine does) have access to such journals.

But the thing is that the American society is the copyright holder and not the author(s). I guess ADA will have copies of the same.

[member_26965]

All, thanks for your kind words but please don't waste space and time defending my posts.

Ranji, I think you were prejudiced while reading my posts. I request you to read them again. Also, with all due respect, I don't think you have understand what ADA wrote as well. Please consider reading them as well.

@ranji
If LEVCON helps in carrier landing, won't it be helpful in reducing approach speed for AF version, thus reducing landing distance and/or eliminating need of chute breaking?? It also would help in low-speed maneuverability, theoretically, wouldn't it?? Well ADA must have good reasons not to keep LEVCON for at least LCA MK2 AF version. May be they are not as effective just like canards were not for LCA. I wonder why?? JMT

Of course having LEVCON's on the AF version will lower the approach speed. But is it required? I don't think that the Levcons can obviate the drag chute (the levcons will lower the approach speed by about 5-15 knots).
For reasons why ADA did not go for the levcons even on Mk2 is long.
1. Slower speed handling of AF version is not required.
2. The cranked arrow wing of LCA along with the long twist at the wing join gives it similar characteristics to that of a close coupled canard design (albeit not a movable one). I will leave you to learn about that wing design (Hint 1. Do consider the F-16XLs wing. Hint 2: understand how the twist aids in merging the wing and the tail plane. You will love the research.)
3. The CL of the LCA's wing itself keeps rising till 35 degree AoA.
4. The limiting factor is the yaw control authority. The rudder gives good control authority till 24(22?) degrees. But it can be artificially stabilized till about 26 degrees (FOC objective).
5. Therefore adding levcons won't make the plane much more agile. It will definitely allow better slow speed handling.
6. It is very complex non-linear study of how the levcons along with slats could aid in better control. It has been reported in the paper I cited. I am not privy to more information.

It clearly shows that you are prejudiced and you are wasting the word on me.

I too have replied that the IAF has no such requirement and hence no LEVCONS. Can you point out otherwise? I really don't know the reason for your lengthy explanations for something which has not been asked for. I think you are barking up the wrong tree. With all respects, I am only using phrases.

It is you who claimed that Slow speeds and better control does not aid to Naval pilots AC landing. You claimed that Nose droop constituted the clear visibility. I am asking you why Slow speeds and better control does not mean better visibility? It is a simple question.

Secondly, you claimed LEVCONS can be used for other purposes, for which I had already mentioned that LEVCON use has been defined by ADA. Can you explain that comment with respect to 'either' what the original question "why IAF mk 2 version does not has Levcon," or even " explain what ADA can use is for on LCA Navy" (remember the above unnecessary cranked edge explanation).

This also shows the herd mentality is some.

[Gurneesh]

I am asking you why Slow speeds and better control does not mean better visibility? It is a simple question.

Secondly, you claimed LEVCONS can be used for other purposes, for which I had already mentioned that LEVCON use has been defined by ADA. Can you explain that comment with respect to 'either' what the original question "why IAF mk 2 version does not has Levcon," or even " explain what ADA can use is for on LCA Navy" (remember the above unnecessary cranked edge explanation).

This also shows the herd mentality is some.

To reduce landing speed, you need to increase the Angle of Attack (which also means poorer visibility). So for a lower speed carrier landing, aircraft will need to increase it's angle of attack. Levcon will aid in increasing the angle of attack by delaying the wing stall and the drooped nose will help maintain visibility at higher angle of attack. You should see the videos of slow and fast flybys done by LCA at aeroindia, the difference in angle of attack will be obvious.

[member_26965]

^^^^^ HAHAHAHAHAHA! This is a gem. On contrary, it helps reduction in AOA without letting the aircraft stall. ... and hence improving visibility.

[Indranil]

It clearly shows that you are prejudiced and you are wasting the word on me.

I too have replied that the IAF has no such requirement and hence no LEVCONS. Can you point out otherwise? I really don't know the reason for your lengthy explanations for something which has not been asked for. I think you are barking up the wrong tree. With all respects, I am only using phrases.

It is you who claimed that Slow speeds and better control does not aid to Naval pilots AC landing. You claimed that Nose droop constituted the clear visibility. I am asking you why Slow speeds and better control does not mean better visibility? It is a simple question.

Secondly, you claimed LEVCONS can be used for other purposes, for which I had already mentioned that LEVCON use has been defined by ADA. Can you explain that comment with respect to 'either' what the original question "why IAF mk 2 version does not has Levcon," or even " explain what ADA can use is for on LCA Navy" (remember the above unnecessary cranked edge explanation).

This also shows the herd mentality is some.

Boss, this is a first for me. Forgive me for being condescending on your pathetic knowledge in aerodynamics. I think you think that you know aerodynamics.

1. I have answered the original questions. People who asked the questions and people who understand aerodynamics, got it. Not you. If you are interested to know, please read them. Don't ask me to repeat simple things.
2. Please don't put words into my mouth. I never said ADA should add LEVCONs to LCA-AF. Read my posts more carefully.
3. I never said that slow speeds and better control does not aid to Naval pilots AC landing. Slow speeds and better control has nothing to do with visibility. Infact it is quite the opposite. For slower speeds you need to pitch up more, the nose comes up in your view. If I raise the bonet of your car and ask you to drive slowly, will it improve your visibility? To avoid this they drooped the nose. I can't put it more simply.
4. Please stop (mis)quoting ADA. The uses of Levcons cannot be defined by ADA. It is defined by physics. They understand this and are studying this. Several papers have been cited to studies by ADA regarding use of LEVCONs which clearly show their advantage (but you are too arrogant or too busy to even check).

P.S. Mods, you can punish me for this post, but I won't retract my post. There is only so much misplaced arrogance that I can handle.

[Indranil]

To reduce landing speed, you need to increase the Angle of Attack (which also means poorer visibility). So for a lower speed carrier landing, aircraft will need to increase it's angle of attack. Levcon will aid in increasing the angle of attack by delaying the wing stall and the drooped nose will help maintain visibility at higher angle of attack. You should see the videos of slow and fast flybys done by LCA at aeroindia, the difference in angle of attack will be obvious.

^^^^^ HAHAHAHAHAHA! This is a gem. On contrary, it helps reduction in AOA without letting the aircraft stall. ... and hence improving visibility.

Stop making a fool of yourself.

[Indranil]

I wonder what kind of 'nose droop' is being contemplated for the NLCA, the actuating type as in the Backfire bomber and Concorde or the fixed type as in the Su30mki. The former seems unlikely because of the complex actuating mechanism and overlapping fuselage sections that would be required along with the added weight. So more likely it will be the fixed droop. Both will change the aerodynamics during the critical landing approach and will need to be tested. If this is what ADA has in mind then IMO it should be made standard for both NLCA and LCA2, along with the LEVCON. For a short range fighter, the capability of operating on short stretches of highway would be a plus during wartime if frontline runways are bombed and unusable.

The nose droop is fixed. You can already see it in the trainer and the naval prototype vis-a-vis the AF version.

The rudder/tail being 'hidden' from airflow behind the plane at high AoA is why some fighters like F-18, F-35, MiG-29 have twin and outward canted vertical fins. They can also aid high AoA/pitch by both being turned inwards. ADA must have considered this option too.

That's not the only reason. All these fighters are quite heavy. If you had just one tail, it would have to be really big. All 5th generation planes also need canted tails for stealth.

[member_26965]

Boss, this is a first for me. Forgive me for being condescending on your pathetic knowledge in aerodynamics. I think you think that you know aerodynamics.

1. I have answered the original questions. People who asked the questions and people who understand aerodynamics, got it. Not you. If you are interested to know, please read them. Don't ask me to repeat simple things.
2. Please don't put words into my mouth. I never said ADA should add LEVCONs to LCA-AF. Read my posts more carefully.
3. I never said that slow speeds and better control does not aid to Naval pilots AC landing. Slow speeds and better control has nothing to do with visibility. Infact it is quite the opposite. For slower speeds you need to pitch up more, the nose comes up in your view. If I raise the bonet of your car and ask you to drive slowly, will it improve your visibility? To avoid this they drooped the nose. I can't put it more simply.
4. Please stop (mis)quoting ADA. The uses of Levcons cannot be defined by ADA. It is defined by physics. They understand this and are studying this. Several papers have been cited to studies by ADA regarding use of LEVCONs which clearly show their advantage (but you are too arrogant or too busy to even check).

P.S. Mods, you can punish me for this post, but I won't retract my post. There is only so much misplaced arrogance that I can handle.[/quote]

1) So you are running away from your pathetic response.

LEVCONS on NLCA is for low landing speeds, better control and hence aids visibility while carrier landing. This is defined use and not what Levcon general definition is. LCA AF has not use for it.

The bolded part is wrong. if you have higher AoA your nose obstructs the view more. That's why they had to droop the nose. Also, the defined use can be extended. When you have the hardware, why not use it.

2) Unnecessary diversion. I am referring to only 1. So stop blabbing.

3) I have quoted you already in 1. Don't hide behind words.

4) Please stop the nonsense of your technicalities. ADA has specifically said that it is using LEVCONS for.

Stop making a fool of yourself.

How so? Are you saying that what Gurneesh is correct? Shows what technical knowledge you have.

MoD's need not punish you. Your pathetic mask is dropping. That it self is a punishment for you.

[Indranil]

You win .

[rajanb]

You win .

+1 Agreed. He is an expert of AoA (pun Intended) and BENIS will fete him

[member_26965]

There goes the most effective communicator title. You are just as pathetic as your herd supporters. You are applying LERX definition to LEVCON. Show me the literature on Vortex controllers by ADA.

[jamwal]

This ranji guy is a known troll. Why waste time replying to his inane ramblings !

[member_26965]

You are a troll. You could have come up with literature on Vortex Control by ADA. Instead you choose to troll.

And show me the examples where I trolled. Else you are a liar.

[JayS]

Of course having LEVCON's on the AF version will lower the approach speed. But is it required? I don't think that the Levcons can obviate the drag chute (the levcons will lower the approach speed by about 5-15 knots).
For reasons why ADA did not go for the levcons even on Mk2 is long.
1. Slower speed handling of AF version is not required.
2. The cranked arrow wing of LCA along with the long twist at the wing join gives it similar characteristics to that of a close coupled canard design (albeit not a movable one). I will leave you to learn about that wing design (Hint 1. Do consider the F-16XLs wing. Hint 2: understand how the twist aids in merging the wing and the tail plane. You will love the research.)
3. The CL of the LCA's wing itself keeps rising till 35 degree AoA.
4. The limiting factor is the yaw control authority. The rudder gives good control authority till 24(22?) degrees. But it can be artificially stabilized till about 26 degrees (FOC objective).
5. Therefore adding levcons won't make the plane much more agile. It will definitely allow better slow speed handling.
6. It is very complex non-linear study of how the levcons along with slats could aid in better control. It has been reported in the paper I cited. I am not privy to more information.

Thanks for the reply. I was just thinking aloud.
a small correction to 4th point. Radder had control till 30deg which is gonna help them increase AoA to 26deg.
A snippet from high AoA testing document from NFTC, ADA:

However, directional characteristics indicated the proverbial ‘cliff’ with a sudden drop in
Cn , CRM (Coefficient of Rolling Moment) and CYM (Coefficient of Yawing Moment) at
approx 25 AoA as shown at fig-4 and 5. These phenomena require the High AoA trials
to be limited to 24 (as shown in dotted line) until directional stability is bolstered and
augmented by rudder control up to an expected 26. Currently the Tejas is flying to AoA
limits of 20 and 22 never exceed. Fortunately as shown in fig-6, the LCA has
significant rudder authority (CYM-Del R) even up to 30 AoA that will allow artificial
stabilization in yaw at high AoA.

We can rest the case of LEVCON for LCA i think.

I have been digging about F16XL already, haven't got correct literature so far but I'll find it.

BTW, I had posted this in newbie thread:

There is difference between "Cranked Delta Wing" and "Cranked Wing". I am trying to find some technical reference but so far whatever I have recollected, LCA wing can't be called "Cranked Delta Wing". It could be called "Cranked wing" due to wing-root anhedral wing section as compared to outboard part which is almost flat. That's why I specifically mentioned "Compound double Delta".

See this wiki link: http://en.wikipedia.org/wiki/Wing_configuration

What is your opinion on this one??

[JayS]

4. The limiting factor is the yaw control authority. The rudder gives good control authority till 24(22?) degrees. But it can be artificially stabilized till about 26 degrees (FOC objective).

The rudder/tail being 'hidden' from airflow behind the plane at high AoA is why some fighters like F-18, F-35, MiG-29 have twin and outward canted vertical fins. They can also aid high AoA/pitch by both being turned inwards. ADA must have considered this option too.

Not just this, there are lot more reasons for going to twin tail. One as Indranil said, for keeping size in check. Other being, most of those fighters are twin engine. If one is to fail, then the rudder has to compensate for the yaw moment due to single engine operation. This would also need huge rudder if only one tail is there. Then, for delta wing, there are two huge vortices. Two vortices passing from both sides would affect rudder control authority. Also vortex bursting aggreviates the issues. For LCA rudder is effective till 30deg which is good enough.

So many parameters to consider while deciding configurations and then all combinations have to be tested thoroughly. When LCA will be used by IAF, more and more user feedback will come and there might be few niggles here and there. ADA will eventually fine tune the design to removw them. We might see a strake or two, some aerodynamic fences etc on LCA in future.

[member_26965]

Read Here http://www.pprune.org/archive/index.php/t-426301.html

The stronger the wingtip vortices, the greater will be the increase in critical angle and the drag. Any factor that decreases wingtip vortex strength will decrease critical angle and drag.

[Lalmohan]

Perhaps wiser aerodynamicists can enlighten me on which is the dependent variable here?

[member_26965]

Look, the LCA Navy has Vortex Controllers. (LEVCoNs). If ADA wanted a LERX, they would have gone for it. But ADA wants to control Vortex in order to reduce AOA and The drag. Lower AOA is visibility.

[ArmenT]

The rudder/tail being 'hidden' from airflow behind the plane at high AoA is why some fighters like F-18, F-35, MiG-29 have twin and outward canted vertical fins. They can also aid high AoA/pitch by both being turned inwards. ADA must have considered this option too.

That's not the only reason. All these fighters are quite heavy. If you had just one tail, it would have to be really big. All 5th generation planes also need canted tails for stealth.

In the case of US Navy planes (F-14, F-18 etc.) the USN also wanted redundancy built into the design (e.g. if one rudder gets damaged, you can still fly somewhat with the other one. Redundancy is also the reason why USN refused to buy single engine aircraft for many decades). The other big reason was because twin tails would be smaller than a single large tail. If you look at the F-111, it is a twin engine fighter with a huge single tail (as is the Tornado). If I remember correctly, the F-14 design was originally planned to be like the F-111 (i.e.) twin engines with huge single tail in the middle -- then someone at Grumman pointed out that the tail would be so tall that it could not fit in the below deck hangars of the existing USN carriers. On the other hand, having two tails increases the complexity of the avionics, but the USN wanted redundancy, so they opted for the more complex design.

LCA, being a smaller aircraft than others, can get away with a single tail, even in the IN version. If they increase its size and add a second engine, then the designers might consider the twin tail arrangement too.

[Indranil]

BTW, I had posted this in newbie thread:

There is difference between "Cranked Delta Wing" and "Cranked Wing". I am trying to find some technical reference but so far whatever I have recollected, LCA wing can't be called "Cranked Delta Wing". It could be called "Cranked wing" due to wing-root anhedral wing section as compared to outboard part which is almost flat. That's why I specifically mentioned "Compound double Delta".

See this wiki link: http://en.wikipedia.org/wiki/Wing_configuration

What is your opinion on this one??

Just my thoughts as I am not sure of the nomenclature myself. There is a good chance that we both learn in the process.

I think the cranked delta wing would be the right description of LCA. And here are my reasons.

1. The anhedral at the wingroot is not maintained along the chord. They wanted to have the leading edge above and in front of the inlet for obvious advantages. But the trailing edge of this kind of a wing is the tailplane. So the twist allows that merge along the chord and the anhedral allows the merge along the span. So I would not call this wing a cranked wing.

2. The crank along the leading edge in the LCA is actually an interesting one. Similar to the Viggen, the sweep actually increases after the crank. In order to increase the air flow above the root, they have the boundary layer spill duct and also a turbulator strip running along the chord at the crank. But still the LCA wing is a delta wing and it is definitely cranked.

I understand why you want to call it a compound delta wing. But I don't understand why you want to call it a "compound double delta" wing.

[Lalmohan]

ranji, help me out here - what is creating the vortex and how does one control it?

[Brando]

Good and simple article on Leading edge vortices and their control : http://www.acsol.net/~nmasters/vortex-lift/delta.html

[member_26965]

ranji, help me out here - what is creating the vortex and how does one control it?

What is creating vortex:
Regular flight: High AOA situations like take off, landing and high AoA maneuvers.
Climatic conditions: Fog, there can be many factors
Artificial: Vortex generators - small vents kind of things by design to generate vortex

Those are general vortex creators. This is not an exhaustive list.

Normally, Vortex controllers can be placed where required, like strake is in mid fuselage, leading edge, nose etc. It is up to designers to take best out of their aircraft.

Leading edge root extensions (LERX) is normally passive way of enabling higher AOA without stalling. Subject to aircraft design objective. They are also movable surfaces.

LEVCON is 'active' LERX controllers. It actually control's the Vortex instead of 'assists.' Normally, all their roles are defined and are not subject to entire spectrum of their capabilities as aircraft may not be able to match the performance. Needless to say, all these surfaces have to assist the performance of aircraft and not that air craft has to perform to their assistance. Particular to LCA navy, ADA has defied its role. I have given a link of a discussion related to how vortex can be controlled and to what effect.

Hope, this is useful as dummy's guide.

[Lalmohan]

yes, good for this dummy. but what about the two really big vortices?

[SaiK]

Has the LCA mk-2 drawings finalized yet?

[JayS]

Read Here http://www.pprune.org/archive/index.php/t-426301.html

The stronger the wingtip vortices, the greater will be the increase in critical angle and the drag. Any factor that decreases wingtip vortex strength will decrease critical angle and drag.

I wonder why you quote this here. Its totally irrelevent from delta wing PoV.

Even in its relevent context (rectangular wings), the inference is totally wrong. Wingtip vortex strength is function of AR and so are other effects you quoted. There is no such relation as strong wingtip vortex causes any change in stalling angle. AR is the independent variable and wingtip vortex strength (thus in turn actual AoA and induced drag) and the stalling AoA are its function.

[Victor]

You can already see it in the trainer and the naval prototype vis-a-vis the AF version

Thanks. My eyes may be playing tricks but they both look like they have the droop though in the 2-seater it looks pronounced. If they have sorted out the aerodynamics with no negative effect, and if the end result is better frontal view, slower approach speed, better control at slow speed and greater lift then all LCAs should benefit from these qualities, not just the NLCA. The only differences can then be arrestor hook and landing gear. LCAs are custom, handmade one-offs now but when it is time to crank them out on a production line, commonality will have a big impact.

[Indranil]

You can already see it in the trainer and the naval prototype vis-a-vis the AF version

Thanks. My eyes may be playing tricks but they both look like they have the droop though in the 2-seater it looks pronounced. If they have sorted out the aerodynamics with no negative effect, and if the end result is better frontal view, slower approach speed, better control at slow speed and greater lift then all LCAs should benefit from these qualities, not just the NLCA. The only differences can then be arrestor hook and landing gear. LCAs are custom, handmade one-offs now but when it is time to crank them out on a production line, commonality will have a big impact.

There is a negative effect of the droop, i.e. increase in drag. The nose droop has nothing to with slower approach speed, better control at slow speed or greater lift. Is there any reason that it would? There is only one reason of the droop, increasing the pilot's visibility at high AoA.

[member_26965]

yes, good for this dummy. but what about the two really big vortices?

Specifically?

nileshjr,

Can you point out a resource instead of giving your half gyan?

and if not here, where it had to be posted? Why is is irrelevant? You should be clear about it.

[Victor]

The nose droop has nothing to with slower approach speed, better control at slow speed or greater lift. Is there any reason that it would?

No it doesn't and I didn't mean to imply that it did. The NLCA has better frontal view (because of droop nose), slower approach speed, better control at slow speed and greater lift (because of levcon) than the LCA and the latter should have these too if they are net-net positives in the interests of commonality.

If there is in fact a meaningfully negative drag effect because of the droop, then it should either be redesigned to be more efficient or the LCA is a very bad candidate for a naval fighter and should be canned. It is already struggling with a weight issue and the NLCA is further burdened with the need for heavier landing gear and an arrestor hook. What little capacity it already has to carry armaments as a 'light' fighter will be further restricted by increased drag, making it practically useless. Better to use what we have learned and apply it to the NLCA2 with the GE414.

[SaiK]

red flag mullah, i found some thing for you:
http://aerostudents.com/files/advancedA ... ummary.pdf

don't ask me questions from it though.

[member_26965]

You are right Victor. Nose droop and loads have led pressure on under carriage and it has made carriage heavy. The frontal portion has hardly any commonality in design, a lot less commonality in avionics, when compared to IAF version. ADA is struggling with the entire package, the LEVCON, the Undercarriage especially.

Misinformers like indranilroy use half baked truth to twist out of situation instead of taking the facts head on. The fact is that Quad digit FCS computer, LEVCON computer, auto throttle, nose droop, arrestor etc are a part of design which brings the aircraft to certain designed parameters helping it to land. Nothing is mutually exclusive. LEVCONS have not yet been tested.

LEVCON's have not just landing function, they have take off functions too, especially ramp take off.

ranji, kindly give it a break with the ref. to other members. put him on ignore if you need.

- Rahul

[Lalmohan]

ranji - two things
dont understand your comment about fog - how does that create vortices?
and the two really big ones... on each wing... what about those?

[member_26965]

Fog: How it creates I don't Know. Plane landing into fog, does create vortex.

What about the vortex on wings? How different is from the vortex which is created in wings and how different is its control or regulation from normal methods like LERX, Chines etc? If it falls within the definition, you have been already replied in dummy's guide. If not, you can elaborate.

[Indranil]

The nose droop has nothing to with slower approach speed, better control at slow speed or greater lift. Is there any reason that it would?

No it doesn't and I didn't mean to imply that it did. The NLCA has better frontal view (because of droop nose), slower approach speed, better control at slow speed and greater lift (because of levcon) than the LCA and the latter should have these too if they are net-net positives in the interests of commonality.

Victor,
There are two things here.
1. The levcons add one more wing tip which will shed vortices. So, the combined lift to drag ratio is going to be lower than a clean wing.
2. At higher AoA, the levcons delay the flow separation over the wing thus allowing higher AoA (and lift) and lower stall speeds.

AF does not need lower landing speed, why should it pay the price? Nilesh's question was simple. Levcons allow higher AoA. So will it allow higher STR? He is not alone in asking this question. ADA is studying this. And Sukhoi definitely sees virtue in it.

If there is in fact a meaningfully negative drag effect because of the droop, then it should either be redesigned to be more efficient or the LCA is a very bad candidate for a naval fighter and should be canned. It is already struggling with a weight issue and the NLCA is further burdened with the need for heavier landing gear and an arrestor hook. What little capacity it already has to carry armaments as a 'light' fighter will be further restricted by increased drag, making it practically useless. Better to use what we have learned and apply it to the NLCA2 with the GE414.

The droop adds drag by virtue of the higher frontal area. But it is a price that ADA is willing to pay. All naval fighters pay these kind of prices. It is their operational requirement. And all operational NLCAs will be powered by GE414s.

[JayS]

Just my thoughts as I am not sure of the nomenclature myself. There is a good chance that we both learn in the process.

I think the cranked delta wing would be the right description of LCA. And here are my reasons.

1. The anhedral at the wingroot is not maintained along the chord. They wanted to have the leading edge above and in front of the inlet for obvious advantages. But the trailing edge of this kind of a wing is the tailplane. So the twist allows that merge along the chord and the anhedral allows the merge along the span. So I would not call this wing a cranked wing.

2. The crank along the leading edge in the LCA is actually an interesting one. Similar to the Viggen, the sweep actually increases after the crank. In order to increase the air flow above the root, they have the boundary layer spill duct and also a turbulator strip running along the chord at the crank. But still the LCA wing is a delta wing and it is definitely cranked.

I understand why you want to call it a compound delta wing. But I don't understand why you want to call it a "compound double delta" wing.

Hi,
My bad, "compound double delta" was overkill. My brain is rusted i guess, needs some polishing.

Agreed. Only thing from my side, it can't be called "Cranked arrow delta" (because it does not have that characteristic "kink" at TE, which gives the distictive arrow tip shape).

Well as long as we understand the wing completely, sementics doesn't matter much.

Some more doubts:
1. when we say "wing is twisted" (wash in/out), about which axis the wing sections are turned actually?? For ex: if i rotate inboard sections w.r.t. axis passing through TE, I will end up getting twist + anhedral both (like in LCA). This can't be pure twist. Then which axis should it be. I can think of two natural options: About mid points of those sections or the aerodynamics center of thoseperticular sections??

2. B Harry's article says (pg 85):

Two hollow spill ducts, next to leading edge, connect with the intake splitter and act as suction system for boundary layer/vortex control and reducing skin friction drag

I thought they act more like Blowing/Injection system and they blow air coming from intake splitters onto the root section of the wing to energige it and also enhancing LE vortex structure. How can it act as suction system? What am I missing here?

[JayS]

nileshjr,

Can you point out a resource instead of giving your half gyan?

and if not here, where it had to be posted? Why is is irrelevant? You should be clear about it.

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At Thy feet we humbly bow;
Lord, we know not how to go
Till a blessing Thou bestow.
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Thee a gracious God and kind.