LCA Tejas: News and Discussions

Sanjay · Post by **Sanjay** » 20 Apr 2015 09:31

Thanks a heap Singha. Was ITR of Tejas much worse than F-16 ?

Singha · Post by **Singha** » 20 Apr 2015 09:37

afair the ITR was one of highest in tejas. f16 has one of highest wing loading.

RoyG · Post by **RoyG** » 20 Apr 2015 09:46

Singha wrote:
RoyG wrote:Did the LCA designers incorporate anything from the Mirage 2000 into the design besides maybe the delta type wing? On what parameters does LCA score over Mirage 2000? Someone mentioned once that a canard design was once considered. Why wasn't it ever pursued?
I think complexity and weight. the LCA designers did not have the size and weight budget given to the M2k. they were told to make it small and they did.
another big decision was not to have the moveable shock cones and settled for m1.8 max....lot of eminent a/c like F-solah, rafale and gripen also accepted that.

but air superiority oriented birds like F-15, EF, Su27 family and m2k have shock cones or moveable constricting surfaces in inlet tunnel to ramp it up to mach2+
for some reason even the tornado has it though designed as a all-weather dpsa..and it can do mach2 at high level apart from being very speedy and very slippery at low level.

Hm, that's interesting. I'm wondering if the canard version may be resurrected by Parrikar and perhaps maybe the private sector given a lead role to produce it within a certain time frame. I'm not sure how long it would be relevant given that MkI and II induction is right around the corner. Looks like a beautiful design.

http://i.imgur.com/47D98dc.jpg

Found this excellent documentary on M2k.

https://www.youtube.com/watch?v=-QAWIK_RgV0

Indranil · Post by **Indranil** » 20 Apr 2015 09:49

RoyG wrote:Did the LCA designers incorporate anything from the Mirage 2000 into the design besides maybe the delta type wing? On what parameters does LCA score over Mirage 2000? Someone mentioned once that a canard design was once considered. Why wasn't it ever pursued?

People have done their homework, found out the details, abridged it and presented it. On this very thread, a few pages back. The least you can do is at least search once before asking this?

Indranil · Post by **Indranil** » 20 Apr 2015 09:52

RoyG wrote: Hm, that's interesting. I'm wondering if the canard version may be resurrected by Parrikar and perhaps maybe the private sector given a lead role to produce it within a certain time frame. I'm not sure how long it would be relevant given that MkI and II induction is right around the corner. Looks like a beautiful design.

http://i.imgur.com/47D98dc.jpg

Parrikar, the private sector and you must know more than the people who built, tested and rejected this design over the current configuration!

RoyG · Post by **RoyG** » 20 Apr 2015 09:52

indranilroy wrote:
RoyG wrote:Did the LCA designers incorporate anything from the Mirage 2000 into the design besides maybe the delta type wing? On what parameters does LCA score over Mirage 2000? Someone mentioned once that a canard design was once considered. Why wasn't it ever pursued?
People have done their homework, found out the details, abridged it and presented it. On this very thread, a few pages back. The least you can do is at least search once before asking this?

Thanks.

RoyG · Post by **RoyG** » 20 Apr 2015 09:57

indranilroy wrote:
RoyG wrote: Hm, that's interesting. I'm wondering if the canard version may be resurrected by Parrikar and perhaps maybe the private sector given a lead role to produce it within a certain time frame. I'm not sure how long it would be relevant given that MkI and II induction is right around the corner. Looks like a beautiful design.

http://i.imgur.com/47D98dc.jpg
Parrikar, the private sector and you must know more than the people who built, tested and rejected this design over the current configuration!

Hey if it was rejected based on its performance then why bother.

pragnya · Post by **pragnya** » 20 Apr 2015 10:03

indranilroy wrote:
RoyG wrote:Did the LCA designers incorporate anything from the Mirage 2000 into the design besides maybe the delta type wing? On what parameters does LCA score over Mirage 2000? Someone mentioned once that a canard design was once considered. Why wasn't it ever pursued?
People have done their homework, found out the details, abridged it and presented it. On this very thread, a few pages back. The least you can do is at least search once before asking this?

IR

i had happened to copy to notepad the following post by Merlin who was answering a similar question regards the canards for LCA which may interest you and nilesh. i don't know the date of his post. he gave an extract of a post by another poster called siva mahalingam who explains the reasons. may be if you search for it in Archives you may see it. i quote Merlin's post below

merlin wrote:

Ok, finally found the printout of the post by an old poster with the handle Siva Mahalingam (post is from 6/1/98 in the old BR Forum). I have typed an extract below since my scanner is on the blink. Bear in mind the following disclaimer that the author has also written - "I have been following the development of the LCA since it's inception. The following is my assessment of the LCA in comparison with it's rivals. Most of the information is from articles and analysis in various aircraft publications and news releases. The comparison represents my opinions and is therefore not necessarily all correct, but I hope they will provoke discussion."

Extract:

"(LCA) Uses delta planform rather than close coupled canard arrangement of Gripen, Rafale, Eurofighter and Lavi/F10, or conventional aft tail arrangement of F16 and F22. Delta wing has the disadvantage of loss of control at high angle of attack due to airflow at wing root abruptly changing between straight back over wing to cutting upward and across fuselage. Mirage 2000 and Kfir/Cheetah Mirage III modifications have strakes /small canards in front of wing for this reason. Close coupled canard selected for Gripen, Rafael, Eurofighter, Lavi/F10 and aft tail selected for F22 also for same reason. These either provide alternative control surface unaffected by air flow changes or fixed canards to increase the angle of attach required to change airflow (Kfir) or strakes to induce a vortex which ensures the change will occur gradually and so not lead to loss of control (Mirage 2000). In the LCA the designers have solved the problem by using a reduced (compound) sweep at the wing root and using a wing which is high at the front (and low at the back (by tipping the fuselage forward) and with anhedral in order to avoid excessive roll stability). These features also have the beneficial effect of improving forward and sideways visibility. The effectiveness of the vertical fin is also increased by tipping the fuselage forward due to airflow being deflected onto the fin from the wing when the aircraft tries to go sideways (the F4 Phantom has downward tilted tailplane for same reason). This results in a smaller fin than the other aircraft, which saves weight and reduces lateral radar cross section.

The advantage of using a delta are reduction in weight and complexity by doing away with the canards and their actuators, which is important in a very small aircraft. The disadvantage is that in order to achieve the same maneuverability as close coupled canard or aft tail configuration, a delta must be made more unstable and so place greater demands on the fly by wire system. The Gripen designers considered a delta arrangement but rejected it on the grounds that it was too risky. The weight savings and reduced drag from elimination of canards or tailplane should give LCA a good acceleration, rate of climb and rate of turn compared with F16, Rafael, Eurofighter. Lavi/F10 even though its small size means avionics, pilot and missiles will form a greater proportion of its weight."

Karan M · Post by **Karan M** » 20 Apr 2015 10:10

Singha wrote:it is not underpowered in the absolute sense but power is only one factor in the equation - its more draggy fuselage and less lifting surface in real world use cases brings it to the level of m2k (I think) when in reality it should have sharper specs due to larger wing area (less wing loading) , albeit mirage has more powerful engine also.

That restricted fuselage length to fit into MiG-21 basing is the real issue. It'll be interesting to see the performance of the Mk2 - a good improvement, but the NLCA Mk2 should be the real performer.

Indranil · Post by **Indranil** » 20 Apr 2015 10:33

pragnya wrote:
IR

i had happened to copy to notepad the following post by Merlin who was answering a similar question regards the canards for LCA which may interest you and nilesh. i don't know the date of his post. he gave an extract of a post by another poster called siva mahalingam who explains the reasons. may be if you search for it in Archives you may see it. i quote Merlin's post below

merlin wrote:

Ok, finally found the printout of the post by an old poster with the handle Siva Mahalingam (post is from 6/1/98 in the old BR Forum). I have typed an extract below since my scanner is on the blink. Bear in mind the following disclaimer that the author has also written - "I have been following the development of the LCA since it's inception. The following is my assessment of the LCA in comparison with it's rivals. Most of the information is from articles and analysis in various aircraft publications and news releases. The comparison represents my opinions and is therefore not necessarily all correct, but I hope they will provoke discussion."

Extract:

"(LCA) Uses delta planform rather than close coupled canard arrangement of Gripen, Rafale, Eurofighter and Lavi/F10, or conventional aft tail arrangement of F16 and F22. Delta wing has the disadvantage of loss of control at high angle of attack due to airflow at wing root abruptly changing between straight back over wing to cutting upward and across fuselage.

Thank you. I will have to dig more. Baat mein dum hai

. Though Nilesh won't agree with the "anhedral for role instability" part

.

All I can say is that they had done a lot of studies on the flow at the apex of the wing. They built excellent solvers for these and also for studying asymmetric vortices from slender, non-circular, fuselage-like bodies at high AoA. If you combine these, you get what the above poster is speaking of. Unfortunately, everything in the open source is about using these models on classic delta wing shape, standard to papers on deltas. Everything on LCA is part of NAL archives, which is beyond my reach.

Singha · Post by **Singha** » 20 Apr 2015 10:37

note that F-solah is now a family of a/c. by all accounts the earliest block10-block15 which TSPians also got had the best dogfighter pedigree. then it regressed for a while until a "bigmouth" Block40 again matched that. then it has regressed again as the a/c has gained weight via CFTs and enormous variety of weapons and sensors block50, 52, 60....

the block52 of the TSPians certainly will not be as agile as dogfighter as leaner earlier iterations of this hound dog.

Indranil · Post by **Indranil** » 20 Apr 2015 10:46

Singha ji, you missed the best of the lot, block-30. The best dog fighter till date in the eyes of many who have flown many eastern and western fighters

.

deejay · Post by **deejay** » 20 Apr 2015 11:10

pragnya wrote: IR

i had happened to copy to notepad the following post by Merlin who was answering a similar question regards the canards for LCA which may interest you and nilesh. i don't know the date of his post. he gave an extract of a post by another poster called siva mahalingam who explains the reasons. may be if you search for it in Archives you may see it. i quote Merlin's post below

merlin wrote:

Ok, finally found the printout of the post by an old poster with the handle Siva Mahalingam (post is from 6/1/98 in the old BR Forum). I have typed an extract below since my scanner is on the blink. Bear in mind the following disclaimer that the author has also written - "I have been following the development of the LCA since it's inception. The following is my assessment of the LCA in comparison with it's rivals. Most of the information is from articles and analysis in various aircraft publications and news releases. The comparison represents my opinions and is therefore not necessarily all correct, but I hope they will provoke discussion."

Extract:

"(LCA) Uses delta planform rather than close coupled canard arrangement of Gripen, Rafale, Eurofighter and Lavi/F10, or conventional aft tail arrangement of F16 and F22. Delta wing has the disadvantage of loss of control at high angle of attack due to airflow at wing root abruptly changing between straight back over wing to cutting upward and across fuselage. Mirage 2000 and Kfir/Cheetah Mirage III modifications have strakes /small canards in front of wing for this reason. Close coupled canard selected for Gripen, Rafael, Eurofighter, Lavi/F10 and aft tail selected for F22 also for same reason. These either provide alternative control surface unaffected by air flow changes or fixed canards to increase the angle of attach required to change airflow (Kfir) or strakes to induce a vortex which ensures the change will occur gradually and so not lead to loss of control (Mirage 2000). In the LCA the designers have solved the problem by using a reduced (compound) sweep at the wing root and using a wing which is high at the front (and low at the back (by tipping the fuselage forward) and with anhedral in order to avoid excessive roll stability). These features also have the beneficial effect of improving forward and sideways visibility. The effectiveness of the vertical fin is also increased by tipping the fuselage forward due to airflow being deflected onto the fin from the wing when the aircraft tries to go sideways (the F4 Phantom has downward tilted tailplane for same reason). This results in a smaller fin than the other aircraft, which saves weight and reduces lateral radar cross section.

The advantage of using a delta are reduction in weight and complexity by doing away with the canards and their actuators, which is important in a very small aircraft. The disadvantage is that in order to achieve the same maneuverability as close coupled canard or aft tail configuration, a delta must be made more unstable and so place greater demands on the fly by wire system. The Gripen designers considered a delta arrangement but rejected it on the grounds that it was too risky. The weight savings and reduced drag from elimination of canards or tailplane should give LCA a good acceleration, rate of climb and rate of turn compared with F16, Rafael, Eurofighter. Lavi/F10 even though its small size means avionics, pilot and missiles will form a greater proportion of its weight."

Pragnya ji, Thank You. Fantastic effort. I've missed Merlin's presence.

Karan M · Post by **Karan M** » 20 Apr 2015 11:31

Interesting... a lot of cloak and dagger stuff going on.

Guys read this (of course, can be salacious unattributed gossip with zero guarantor for accuracy):
https://twitter.com/LutyensMasala/statu ... 6634524673
https://twitter.com/LutyensMasala/statu ... 6141926402
https://twitter.com/LutyensMasala/statu ... 8634473472

And this:
https://twitter.com/ajaishukla/status/5 ... 3294352384
Political leanings apparent
https://twitter.com/ajaishukla/status/5 ... 0329550848

JayS · Post by **JayS** » 20 Apr 2015 12:37

indranilroy wrote:Nilesh,

You will enjoy this. Check the references.

By the way, look at the guys who were working on the wing.
The youthful team at ADA is led by Dr T.G.Pai and Dr K.P.Singh and it consists of Biju Uthap, A.K.Ghosh, A.K.Bhattacharya, Dr Santosh Korutu
and others.

Makes me laugh on the internet ninjas who pontificate on how the wing should have been shaped. On how canards would have augmented the plane! Bla bla bla ...

Anand Kumar wrote a paper called "Accurate Development of Leading-Edge Vortex Using an Embedded Conical Grid", where he discusses how to simulate the flow at the leading edge near the apex all the way till 30 degree AoA. Unfortunately, the results for the LCA simulations are not reported in the paper. Instead the experiments depicted are for a planar delta wing with a sweep of 68.2 degrees.

In another paper called "Burst vortex flow-field on a delta wing - A numerical simulation using Euler equations", he studies the vortex breakdown over a wing. Again, the model wing is not the Tejas wing.

One thing is for sure, they knew vortex flow around a delta wing really well.

Between, in 1997, they were planning to have 2 wet pylons per wing.

I knew about this paper for some time now. Couldn't get the papers given in the reference. I have no access to any journals. Didn't notice the wet pylons though.

Among the people you mentioned, AK Ghosh is now PD for AMCA project. I don't know about others much. Names slip out of my mind quickly.

They did develop a lot of Computational tools along with people from NAL/ISRO/IITs. LCA has given a huge impetus to the computational competency development in the country. People tend not to notice such achievements which in time will go on to make their lives better in some way or the other.

About the internet Ninjas: I don't understand why people fight over which plane is better. If you really dig out the reasons why any design team went for the particular aerodynamic configuration, you start appreciating each fighter on its own merits (particularly this canard vs no-canard thing. Canard is no panacea of all problems). Every one of those machines are epitome of human excellence. To bring them to the level of comparison that people do on internet is a grave injustice to not only to those machines but also to the people who have toiled so hard to realize those machines. Its easy to categorically accept or reject something with hand waving but difficult to understand and appreciate hard work.

vasu raya · Post by **vasu raya** » 20 Apr 2015 14:12

Earlier there was some discussion around why even unstable platforms are limited in agility by FBW and its due to the actuators which are rate limited to say 50Hz? so if CFT's are added only relaxing the FBW is needed to still keep the platform agile?

JayS · Post by **JayS** » 20 Apr 2015 14:33

pragnya wrote:
IR

i had happened to copy to notepad the following post by Merlin who was answering a similar question regards the canards for LCA which may interest you and nilesh. i don't know the date of his post. he gave an extract of a post by another poster called siva mahalingam who explains the reasons. may be if you search for it in Archives you may see it. i quote Merlin's post below

merlin wrote:

Ok, finally found the printout of the post by an old poster with the handle Siva Mahalingam (post is from 6/1/98 in the old BR Forum). I have typed an extract below since my scanner is on the blink. Bear in mind the following disclaimer that the author has also written - "I have been following the development of the LCA since it's inception. The following is my assessment of the LCA in comparison with it's rivals. Most of the information is from articles and analysis in various aircraft publications and news releases. The comparison represents my opinions and is therefore not necessarily all correct, but I hope they will provoke discussion."

Extract:

"(LCA) Uses delta planform rather than close coupled canard arrangement of Gripen, Rafale, Eurofighter and Lavi/F10, or conventional aft tail arrangement of F16 and F22. Delta wing has the disadvantage of loss of control at high angle of attack due to airflow at wing root abruptly changing between straight back over wing to cutting upward and across fuselage. Mirage 2000 and Kfir/Cheetah Mirage III modifications have strakes /small canards in front of wing for this reason. Close coupled canard selected for Gripen, Rafael, Eurofighter, Lavi/F10 and aft tail selected for F22 also for same reason. These either provide alternative control surface unaffected by air flow changes or fixed canards to increase the angle of attach required to change airflow (Kfir) or strakes to induce a vortex which ensures the change will occur gradually and so not lead to loss of control (Mirage 2000). In the LCA the designers have solved the problem by using a reduced (compound) sweep at the wing root and using a wing which is high at the front (and low at the back (by tipping the fuselage forward) and with anhedral in order to avoid excessive roll stability). These features also have the beneficial effect of improving forward and sideways visibility. The effectiveness of the vertical fin is also increased by tipping the fuselage forward due to airflow being deflected onto the fin from the wing when the aircraft tries to go sideways (the F4 Phantom has downward tilted tailplane for same reason). This results in a smaller fin than the other aircraft, which saves weight and reduces lateral radar cross section.

The advantage of using a delta are reduction in weight and complexity by doing away with the canards and their actuators, which is important in a very small aircraft. The disadvantage is that in order to achieve the same maneuverability as close coupled canard or aft tail configuration, a delta must be made more unstable and so place greater demands on the fly by wire system. The Gripen designers considered a delta arrangement but rejected it on the grounds that it was too risky. The weight savings and reduced drag from elimination of canards or tailplane should give LCA a good acceleration, rate of climb and rate of turn compared with F16, Rafael, Eurofighter. Lavi/F10 even though its small size means avionics, pilot and missiles will form a greater proportion of its weight."

I have read this post about 2 years ago. Had found it when I went over each and every post from LCA thread that I had access to. It would be great to read the posts from 1998 on LCA thread. Do the Mods have access to the ancient archives of BRF??

Though compelling, now I do not agree to all the points of the post. Definitely not with the Anhedral part as Indranil already pointed out.

I am yet to convince myself on the lower inboard sweep angle for LCA. I think the lower sweep on inboard part results through need of keeping flow around the fin clean. Lower sweep means farther away the LE vortex from centre line and with more spanwise motion. This flow would then keep the outboard LW vortex to move towards the centreline at high AoA. Its pretty clear in my head but I can't articulate it in words properly.

I don't quite agree with the reasoning that he gives for opting for canards. (I does not makes sense to me completely, may be my inability to understand his words). Canards could increase fin effectiveness by having a high velocity stream through the two primary LE vortices - high Velocity stream around fins means higher dynamic pressure and thus higher effectiveness. But they are not employed for that reason. Closed coupled canards are used for lift augmentations while long-coupled canards are for control purpose.

Also that point about fuselage tipping - I think its incorrect (I also used to think that way but..). There is something called as 'Fuselage camber'. The shape that LCA has is ubiquitous. You will find it on almost all supersonic jets. When you design an aircraft for Supersonic speed you get better performance with cambered fuselage. That's what LCA has. Best example: Look at EAP (predecessor of EF-2000) carefully and observe the fuselage camber. While at it also observe wing LE shape in front view.
http://cdn-www.airliners.net/aviation-p ... 198054.jpg
http://ib1.keep4u.ru/b/2009/01/13/eb/eb ... 52a051.jpg

member_22539 · Post by **member_22539** » 20 Apr 2015 16:28

Seems like someone was listening

Maharashtra CM Devendra Fadnavis to meet Manohar Parrikar to seek aircraft hub in Maharashtra

http://indianexpress.com/article/india/ ... harashtra/

Karan M · Post by **Karan M** » 20 Apr 2015 16:53

Gripen in Maharashtra? Lets see what Parrikar decides. This is not a positive step, if it occurs.

JayS · Post by **JayS** » 20 Apr 2015 16:58

^^ From the above news:

Fadnavis revealed, “During my tour abroad last week I visited the aerospace and defence company SAAB at Linkoping Sweden. It was a great experience as we exchanged knowledge about the advanced technology in making of the combat aircraft.”

Armed with this 'ToT' of advanced technology, I guess Fadnavis could manufacture the jet all by himself.

Karan M · Post by **Karan M** » 20 Apr 2015 17:22

Nilesh, this is the classic camel and the arab story. Come in the tent and kick the arab out of the tent.

http://ajaishukla.blogspot.in/2015/04/f ... india.html

New Delhi’s growing and explicitly expressed interest in light fighters has been noted by Swedish company, Saab, which had offered its highly regarded JAS 39 Gripen E light fighter in response to the tender eventually won by Dassault’s Rafale.

Even as Parrikar talked up the need for a light fighter, Maharashtra’s Bharatiya Janata Party (BJP) chief minister Devendra Fadnavis on Wednesday visited Saab’s facility in Sweden, where the Gripen NG fighter is built. From there he tweeted a photo of himself in the cockpit of a Gripen and a message saying: “It was great to be at the aerospace & defence company SAAB at Linkoping, Sweden. Promised a defence manufacturing policy in Maharashtra soon.”

Top Saab officials tell Business Standard that, even before Fadnavis, the chief ministers of UP and Gujarat --- then Narendra Modi --- had held discussions with Saab.

A top Saab official told Business Standard on condition of anonymity: “If we are approached by the government of India, Saab would be happy to partner the Defence R&D Organisation (DRDO), Hindustan Aeronautics Ltd (HAL) or an Indian private company in not just manufacturing fighters in India, but in developing real capabilities for building a single-engine fighter for the IAF.”

This will be no different than the model to either

a) get us CKD/SKD Gripens in India as cheaper than Rafale and slowly throttle the growth prospects of the LCA

b) if the above fails, try and get repackaged Gripens in the form of a LCA by roping in an unwilling DRDO in, which will be told to toe the line as otherwise the program gets cancelled anyways. There will be others in DRDO, a section, which will be sold on the program as they no longer have to struggle to manage this complex program and get to stick a successful sticker on it, a la Brahmos.

But from the national perspective we cannot afford it, as the LCA is about building an indigenous ecosystem and that has to be finished. Not putting Gripen LRUs (save time saar, use ready made stuff saar) in a new shell and calling it LCA Mk3 or whatever.

Its upto the current Govt to not fall for this stuff. Which is why Parrikar should not have tomtommed "Any other light fighter in India" stuff. If you drop blood in the water, sharks will be attracted.

vina · Post by **vina** » 20 Apr 2015 17:28

Arun Menon wrote:Seems like someone was listening

Maharashtra CM Devendra Fadnavis to meet Manohar Parrikar to seek aircraft hub in Maharashtra

http://indianexpress.com/article/india/ ... harashtra/

Well, last time I looked it up , there was some place called Nashik where HAL makes all the Russian origin jets! Has Maharashtra given away Nashik to Gujarat or MP ?

maitya · Post by **maitya** » 20 Apr 2015 17:34

Karan M · Post by **Karan M** » 20 Apr 2015 18:09

Vina? Me?

Singha · Post by **Singha** » 20 Apr 2015 18:18

Its the same game of clever scope creep bros..tanks, arty, fighters.....

geeth · Post by **geeth** » 20 Apr 2015 18:30

I feel it is just to sqeeze the balls of Dassault...GoI will be mad to go after Gripen, anyway you look at it.

RoyG · Post by **RoyG** » 20 Apr 2015 19:56

geeth wrote:I feel it is just to sqeeze the balls of Dassault...GoI will be mad to go after Gripen, anyway you look at it.

It's def possible. Parrikar may be trying to secure more Rafale orders behind the scenes. If this is indeed the case, it will be interesting to see how he strings SAAB along if his true intentions are to go full throttle with the LCA.

brar_w · Post by **brar_w** » 20 Apr 2015 19:59

SAAB has been (apparently) posturing for such a MII effort for a few years (at least months)..Obviously they are quite open that they do not want to compete with the Rafale/MMRCA (which they respect as a process), or the LCA (which they also respect as an indigenous priority). So I guess the message is, screw pitting us against either the bigger Rafale, or the smaller LCA...Simply produce our aircraft as is !

This is likely a bargaining chip being used in the Rafale G2G deal just as the "Su-30MKI can replace rafale" was used by the MOD (my 2 cents).

Sagar G · Post by **Sagar G** » 20 Apr 2015 20:35

Viv S wrote:AM Rajkumar is guilty here of using faulty terminology. You don't just strip a jet engine and 'reverse engineer' the metallurgy that went into creating it. The Chinese have spent decades in their effort, (that too not only with operational engines but domestically license built units), and its only now that they have something to show for it (however modest).

What ridiculous argument is this ??? When did China became gold standard of engineering success ??? The Chinese engine failed endurance test whereas our poorly funded Kaveri passed the same. Saurav jha tweeted about it and the same has been posted in the Kaveri thread. How did that happen ??? By your twisted logic we should have failed as well since China which has invested billions came out lame. So because China couldn't figure out we won't as well !!!

Viv S wrote:All I can suggest is that you spend some time to looking into the various factors involved in the R&D and production of a modern turbofan. Expecting to reverse engineer something like the F414 in 4-5 years, borders on the ludicrous. On second thought, it doesn't border on it, its entirely ludicrous.

So be it let the idea be entirely ludicrous if you don't like the dates add 1 before them and still it would be a positive result w.r.t. securing Tejas and India's interest. The manufacturing of mk.2 will run well into 2030's and GE would still be delivering F414's let them deliver all but we need to study the engine in detail and prepare to kick out USA from the program once all the engine deliveries are done. No need to leak money for decades till Tejas is in service by the way of royalty/maintenance payment to GE.

Viv S wrote:If operational independence is a concern, manufacturing the line-replaceable units domestically is a better investment of time and effort than hoping to reverse engineer the engine by experimentation with a stripped down unit.

So LRU's of a modern engine are less complicated to produce ??? Who is going to provide us with the tech to produce these LRU's ??? How this plan of yours is capable of overcoming a sanction imposed by USA ??? Critical components fall in the LRU category or not ???

Gyan · Post by **Gyan** » 20 Apr 2015 20:37

vivek_ahuja wrote:

Geez. I come back bearing goodies and see that this thread has imploded in the meantime!

Sigh.

Allrighty, then. Let's see if we can focus this thread back to the LCA analysis.

This weekend I finally pulled up my code and uploaded the Mirage-2000C in there to see how it compared with the LCA. I was able to get a decent quality geometry file for the aircraft online and cleaned it up in FlightStream to yield the following:

And I ran it through the solver to get the surface vorticity distribution, which is then integrated for the aerodynamic loads.

I then ran the performance module with the data obtained and saw that I got good comparison with the Dassault flight-data:

Mach 0.8, 30,000 ft ASL
Mirage-2000C carrying center-line drop tank (1,300 L), two external drop tanks (1,700 L each), 4 MICA and 2 Magic missiles

Dassault Range: 2,886 km
FlightStram Range: 2,756 km

So that sounds reasonable. I also compared the simulation data with Polhamus results and they also look reasonable.

I then ran similar numbers for the LCA and the Mirage-2000C at 20,000 ft ASL and got the following (note: aerodynamic coefficients corrected for the LCA reference areas and lengths):

The bottom line is that the LCA has a better engine and fuel efficiency and so it gets close to the Mirage-2000C in range and endurance.

I cannot reconcile how the lift-to-drag ratio for the Mirage-2000C is so much better than that of the LCA. I guess I need to do some more analysis and verification of my algorithms to see if I haven't made a mistake anywhere. But I would bet against it. There is a possibility that my code is overpredicting the Mirage performance and the Dassault guys are simultaneously lying ( ). That's the problem with having just isolated data points to verify against: you can't tell if you are wrong, they are wrong or both are wrong!

The LCA data, on the other hand, is based on the ADA wind-tunnel data, so that isn't expected to be wrong. Unless again, the ADA guys are also lying in their technical papers!

Anyway...

I just thought you guys will like to see what I am up to. Perhaps you all can suggest some validation data sources or thoughts on why the aerodynamic performance of the two aircraft is so different.

I will dig more into this in the coming days.

-Vivek

Great Work Vivek, but slightly disappointing that even with 3 decades difference, LCA cannot beat Mirage 2000 in range performance. It seems from your graph that as a thumb rule LCA Mark-1 with full internal fuel, two sub sonic drop tanks, 3 BVR, 2WVR will have around (25%?) shorter range compared to Mirage 2000 with full internal fuel, two drop tanks, 3 BVR, 2WVR (??) This is even when you have taken equal amount of fuel for both aircrafts. But if you take equal payload (say 1.5 tons) for both aircrafts but maximum internal and external fuel they can carry, then the difference may become even more stark. Mirage range may be greater by 40-50% compared to LCA. (??). I suppose LCA Mark-2 will match Mirage 2000. But then even LCA Mark-2 will continue to remain behind latest versions of F-16s(??).

Sagar G · Post by **Sagar G** » 20 Apr 2015 20:39

Karan M wrote:Rajkumars book has more details on this. It was not reverse engineering the engine, but a more modest though significant effort in fliqht qualifying the engine. The GTRE guys without OEM (GE) assistance, stripped the engine, certified it, and had it flight capable. Usually that requires complete hand holding by the OEM.

I would like to know more about this. Isn't an engine supplied by the OEM already flight qualified ??? They don't test it before dispatching it to their customers ??? I mean it's a very basic thing where any manufacturer puts his product through quality control and tests it before dispatching it to the market (ok ok batch testing in commercial products but this is an aircraft engine !!!) so that it performs as claimed by the manufacturer. What you/retd. AM say seems to me like a customer doing checks for a car he brought to check whether it is drivable !!!

Even if GTRE only did as you say or quote then without having knowledge about the engine in hand, I don't think just anybody would be able to flight qualify an aeroengine. Also I would like to know whether it is a standard procedure to strip down an aeroengine to it's bone to flight qualify it ???

I am totally befuddled by your reply I mean it's like me taking out a car's engine, disassembling it to it's bone, reassembling it back, starting it up and claiming that I reverse engineered it !!! Why Retd. AM use those particular words ??? I don't think that he is a person who doesn't know what reverse engineering is.

I am expecting a big ass reply

Sagar G · Post by **Sagar G** » 20 Apr 2015 20:41

nileshjr wrote:My point - Let's be realistic about technical things at least.

And you are quite right sharing tech. GE will never part with engine core technology. They didn't share any critical tech with Sweden why should they do it with India?? We need our own engine in our own fighters at any cost!! GOI should pump in big bucks and enlarge size of GTRE. Make them the OEM of Jet engines and they then delegate parts to private companies as tier-I companies along with as much competencies they can transfer. GOI should give as much RnD money to those pvt companies as those companies are willing to bring to the table from their own pockets. We need to not only develop an engine but also the eco-system which can produce then like sausages in the time of need.

Also I do not think we are in a position to blatantly reverse engineer technology like China does. We still do not have enough geopolitic and economic leverage that China has today, especially with US and Russia. Both of them are quite dependent on China economically. Also we are much more transparent as a system than China. We will get into a lot of legal/political trouble with reverse engineering. But I am of the opinion that we should do it wherever possible.

If you ask me, we don't need it that much. We are not puting enough money and man-power and expecting do wonders which is not possible. If as a nation we put more money in RnD we could overtake the west in about 2 decades in jet technology.

I agree saar that I am being way too optimistic but the thing is that F414 is stuck with us till 2040, upto the time Tejas is supposed to serve and will most probably touch 2050. So what other options we have other than to reverse engineer that engine with which we would be stuck and USA sanctioning us to suit it's geopolitical game plan is a very real danger (you can't deny this). Are we going to replace F414 midway with the engine we are attempting for AMCA ??? I think I didn't make it clear before so let me say that I am not proposing to cancel the engine order in between but by reverse engineering we should learn everything about the engine in and out so that post the completion of delivery we should be able to maintain/repair/overhaul it on our own without any American support or part supply and thus deny them a cash cow/leverage which they are expecting.

Let's not talk about China's attempt at reverse engineering, they have failed and their indigenous engine didn't pass endurance test in Russia while our's did. So we have already taken a leap forward if what has been reported is true. Also America is suddenly interested in sharing engine tech with us and as past has taught us whenever we are near a breakthrough or achieve the same suddenly foreign unobtanium tech becomes available for us. If I am joining the dots correctly then we have achieved success in creating a knowledge base w.r.t. aero engines and are in a position to attempt making new engines and also understand totally the tech which goes into making one or is on offer. The day's of trying to harass us are over and even if we reverse engineer F414 then only by 2030 or so we would kick them out and by then India is going to be even more secured and most probably a member of UNSC. Geopolitical ramifications isn't a concern anymore.

Overtaking west w.r.t. aero engines is all fine and dandy but what I am asking is what do we do with F414 ??? What do we do when the sanction will strike if we fail to act upon securing this weakness of Tejas ??? Are we going to foolishly wait like before till the sanctions strike to act ??? In short, what is the Plan B for F414 ???

Karan M · Post by **Karan M** » 20 Apr 2015 20:47

Sagar G wrote:
Karan M wrote:Rajkumars book has more details on this. It was not reverse engineering the engine, but a more modest though significant effort in fliqht qualifying the engine. The GTRE guys without OEM (GE) assistance, stripped the engine, certified it, and had it flight capable. Usually that requires complete hand holding by the OEM.
I would like to know more about this. Isn't an engine supplied by the OEM already flight qualified ??? They don't test it before dispatching it to their customers ??? I mean it's a very basic thing where any manufacturer puts his product through quality control and tests it before dispatching it to the market (ok ok batch testing in commercial products but this is an aircraft engine !!!) so that it performs as claimed by the manufacturer. What you/retd. AM say seems to me like a customer doing checks for a car he brought to check whether it is drivable !!!

Even if GTRE only did as you say or quote then without having knowledge about the engine in hand, I don't think just anybody would be able to flight qualify an aeroengine. Also I would like to know whether it is a standard procedure to strip down an aeroengine to it's bone to flight qualify it ???

I am totally befuddled by your reply I mean it's like me taking out a car's engine, disassembling it to it's bone, reassembling it back, starting it up and claiming that I reverse engineered it !!! Why Retd. AM use those particular words ??? I don't think that he is a person who doesn't know what reverse engineering is.

I am expecting a big ass reply

Abe jaan lega kya?

Basically the initial shipment of engines sent to India were not calibrated for a test flight program. All that was done by GTRE. Thats per my memory. They did so because one of the senior guys managed to have been proactive and get his hands on documentation which helped. For more I will have to find my copy of the book.. gimme some time.

JayS · Post by **JayS** » 20 Apr 2015 22:33

Sagar G wrote: I agree saar that I am being way too optimistic but the thing is that F414 is stuck with us till 2040, upto the time Tejas is supposed to serve and will most probably touch 2050. So what other options we have other than to reverse engineer that engine with which we would be stuck and USA sanctioning us to suit it's geopolitical game plan is a very real danger (you can't deny this). Are we going to replace F414 midway with the engine we are attempting for AMCA ??? I think I didn't make it clear before so let me say that I am not proposing to cancel the engine order in between but by reverse engineering we should learn everything about the engine in and out so that post the completion of delivery we should be able to maintain/repair/overhaul it on our own without any American support or part supply and thus deny them a cash cow/leverage which they are expecting.

Let's not talk about China's attempt at reverse engineering, they have failed and their indigenous engine didn't pass endurance test in Russia while our's did. So we have already taken a leap forward if what has been reported is true. Also America is suddenly interested in sharing engine tech with us and as past has taught us whenever we are near a breakthrough or achieve the same suddenly foreign unobtanium tech becomes available for us. If I am joining the dots correctly then we have achieved success in creating a knowledge base w.r.t. aero engines and are in a position to attempt making new engines and also understand totally the tech which goes into making one or is on offer. The day's of trying to harass us are over and even if we reverse engineer F414 then only by 2030 or so we would kick them out and by then India is going to be even more secured and most probably a member of UNSC. Geopolitical ramifications isn't a concern anymore.

Overtaking west w.r.t. aero engines is all fine and dandy but what I am asking is what do we do with F414 ??? What do we do when the sanction will strike if we fail to act upon securing this weakness of Tejas ??? Are we going to foolishly wait like before till the sanctions strike to act ??? In short, what is the Plan B for F414 ???

Agreed!! But even for this kind of reverse engineering 4-5 years won't be enough. But we should do this nonetheless. We can get into the program through offsets. Take as much manufacturing % as we can and feed it to our budding jet mfg complex. That will give them a good start. Started with license production of F404 Volvo Aero now getting into MRO of F404 and getting contracts for outside-OEM support from other countries. We can also do this. Get into F414 MRO and along with that build up MRO capabilities in private industry for other commercial engines. If you can do it for military you could do it for civil. F414 will perhaps have a large user base. We can compete for MRO of that large number of engines on global level. Currently Indian airliners' engines are sent out of India for MRO, which could be services in India itself. This same industry which honed their skills with F414 will take up support work for Kaveri/Godavari/Ganga/Jamuna and what not. There is no dearth of space for both private and government organisations to grow in this field.

We need to work on multiple fronts to build competencies in Jet engine tech. First thing is to take Kaveri to its conclusion with its flight certification while we start the new 110kN project. Pump in more money, expand GTRE, rope in willing private players for manufacturing and get on with setting up the establishment. A lot of other testing facilities, RnD base (industrial as well as academic) also is to be set up. Indeed we are quite successful in Kaveri project. Its sad that they stopped it. It should be revived. Once the Kaveri design is mature, offload it to private players (with royalty from them for the design which should go into further RnD set-up, apart from that let them make any amount of profit no issues). Let them develop spin-offs from Kaveri, marine version is already there, make industrial versions etc.

If I had my way, I would restart Kaveri project with full support for Flight testing. This with the intention of setting up the competancy for flight testing in India, buy mig-29 and IL-76 test beds, setup ground testing facilities etc. Side-by-side start a enhance Kaveri version design project to match up F414. By the time we are honing our skills for flight testing on Kaveri, we would have a prototype ready for this new version which can then be tested much faster. We could eliminate F414 by the time our jets need replacement.

A lot of wishful thinking, I know. But certainly doable. Only will is necessary, we have all the resources as a nation.

I feel stopping Kaveri is a grave strategic mistake. We could have built flight testing capabilities in near future which would have accelerated future programs a great deal.

srin · Post by **srin** » 20 Apr 2015 22:40

Developing engines without a flying test bed is like developing aircraft without wind tunnels. Huge mistake (I hope they build radio-anechoic chambers for AMCA). Before they revive Kaveri, they should first get the basics in place.

Secondly, though they've terminated Kaveri, I'm not sure if they have terminated the turbine engine development at GTRE - so the real question is, what is GTRE working on ?

JayS · Post by **JayS** » 20 Apr 2015 23:25

indranilroy wrote:Nilesh,

I am being a little lazy. Will you please remind me of your vortex theory that you presented with the following PIV diagram? The shorter the better. The vortex axes of the inward and the outward wing intersect. Do you also suspect that the secondary vortices energize each other and pulls the primary vortices inward and delays vortex breakdown?

It might well be, because look at the reattachment point of the primary vortex. That is close to the wing root!

Those are not PIV images. They are from CFD simulations. These are older Euler code results which are not accurate enough for high AoA flows. Phenomena such as vortex bursting won't be predicted well enough. We have some better results from that LEVCON paper. According to that the inboard shift of vortex starts with the enlargement and busting of the LE vortices, which is not good.

Gist of what I had written:

The vortices produced by canards or LERX, those ones are small but concentrated vortices whereas the one coming from the LE of inboard section of LCA is a huge thing. That LE vortex dominates the whole flow on the wing suction side. The effect is much more profound and the inboard LE vortices are actually the dominant feature. The inboard LE vortex strengthens the outboard LE vortex.

I think the lower sweep inboard section has one more advantage. It keeps flow nice and smooth over the centerline of the a/c and over the vertical tail by shifting the LEV towards outboard section. (Higher the sweep closer the vortices to the center-line). By keeping those vortices away from tail keeps it effective over all the AoA range and saves it from adverse effects such as buffeting due to vortex bursting which is highly unpredictable phenomenon.

The point you are making about Secondary vortices is different. It is for plain delta wing with one LE vortex. Enlargement of secondary vortex will obviously 'push' primary vortex inwards and upwards as it resides above the secondary vortex.

JayS · Post by **JayS** » 20 Apr 2015 23:28

srin wrote:Developing engines without a flying test bed is like developing aircraft without wind tunnels. Huge mistake (I hope they build radio-anechoic chambers for AMCA). Before they revive Kaveri, they should first get the basics in place.

Secondly, though they've terminated Kaveri, I'm not sure if they have terminated the turbine engine development at GTRE - so the real question is, what is GTRE working on ?

new engine project - The 110kN engine for AMCA.

Indranil · Post by **Indranil** » 21 Apr 2015 06:41

nileshjr wrote: Those are not PIV images. They are from CFD simulations. These are older Euler code results which are not accurate enough for high AoA flows. Phenomena such as vortex bursting won't be predicted well enough. We have some better results from that LEVCON paper. According to that the inboard shift of vortex starts with the enlargement and busting of the LE vortices, which is not good.

Don't know. There are quite a few papers by Anand Kumar which shows that their simulations had good fidelity. In one paper, he did match results with the LCA wind tunnel test results. For some tests it was a perfect match. IIRC, the vortex breakdown reaches the TE at 33 degrees and the apex at 52 or 55 degrees. Not just that they got good results even with matching sharp edges and round edges with various radii. Similar results were published people at Jadavpur university. We know that some development did go on there.

nileshjr wrote:
Gist of what I had written:

The vortices produced by canards or LERX, those ones are small but concentrated vortices whereas the one coming from the LE of inboard section of LCA is a huge thing. That LE vortex dominates the whole flow on the wing suction side. The effect is much more profound and the inboard LE vortices are actually the dominant feature. The inboard LE vortex strengthens the outboard LE vortex.

I think the lower sweep inboard section has one more advantage. It keeps flow nice and smooth over the centerline of the a/c and over the vertical tail by shifting the LEV towards outboard section. (Higher the sweep closer the vortices to the center-line). By keeping those vortices away from tail keeps it effective over all the AoA range and saves it from adverse effects such as buffeting due to vortex bursting which is highly unpredictable phenomenon.

So you are saying that because of the lesser sweep of the inboard section, the axis of vortex is more spanwise, taking it away from the fin. But when the primary vortex of the inboard section interacts with the primary vortex of the outboard section, the latter is energized and moves inboard.

vivek_ahuja · Post by **vivek_ahuja** » 21 Apr 2015 06:45

So, the discrepancy with the Mirage-2000C numbers in the previous analysis also leads to other repercussions.

The issue of sustained-turn-rate (STR) was raised earlier on this page. Well, when you account for the aerodynamic characteristics as evaluated from the previous analysis I did, the numbers for the LCA versus the Mirage-2000C in a horizontal sustained turn at empty weight looks like this:

Note: I put in the LCA Mk-2 as a basic analysis by replacing the engine with the newer F414 and left the aerodynamics as they have been reported by the ADA. So that's just a rough estimation of the LCA Mk-2 performance to show what a better engine can provide.

So yeah, unless someone finds me a way to refute the Mirage-2000C's outstanding performance numbers from the simulations, the picture looks "interesting" for the LCA, to say the least.

Anyway, this is an ongoing investigation from my side, but I thought you all needed to appreciate why I am worried about the earlier analysis on range performance for the two aircraft.

Bottom line: Range/Endurance and STR/ITR analysis are not decoupled. The aerodynamics binds both of them together for each aircraft. So an aircraft having very poor range on account of its aerodynamics is also going to have other effects visible in its maneuvering performance.

P.S.: I would like to see this spreadsheet analysis that Singha et. al. are talking about, if anyone has it. Perhaps it will yield some clues as it why my predictions are so much at odds with generally accepted wisdom for the LCA.

-Vivek

Raveen · Post by **Raveen** » 21 Apr 2015 07:07

vivek_ahuja wrote:So, the discrepancy with the Mirage-2000C numbers in the previous analysis also leads to other repercussions.

The issue of sustained-turn-rate (STR) was raised earlier on this page. Well, when you account for the aerodynamic characteristics as evaluated from the previous analysis I did, the numbers for the LCA versus the Mirage-2000C in a horizontal sustained turn at empty weight looks like this:

Note: I put in the LCA Mk-2 as a basic analysis by replacing the engine with the newer F414 and left the aerodynamics as they have been reported by the ADA. So that's just a rough estimation of the LCA Mk-2 performance to show what a better engine can provide.

So yeah, unless someone finds me a way to refute the Mirage-2000C's outstanding performance numbers from the simulations, the picture looks "interesting" for the LCA, to say the least.

Anyway, this is an ongoing investigation from my side, but I thought you all needed to appreciate why I am worried about the earlier analysis on range performance for the two aircraft.

Bottom line: Range/Endurance and STR/ITR analysis are not decoupled. The aerodynamics binds both of them together for each aircraft. So an aircraft having very poor range on account of its aerodynamics is also going to have other effects visible in its maneuvering performance.

P.S.: I would like to see this spreadsheet analysis done years ago on BRF, if anyone has it. Perhaps it will yield some clues as it why my predictions are so much at odds with generally accepted wisdom for the LCA.

-Vivek

I am hoping/I know that the work they are doing to reduce the drag will help with the aero inefficiencies of the LCA design. There are obvious things they missed when it came to drag, and since they are so obvious, I am sure its inexperience with building TFTA fighters...the Mk2 will leverage the lessons learnt with Mk1 and I am sure will show significantly improved characteristics - the quantitative improvement remains to be seen.