LCA News and Discussions

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Re: LCA News and Discussions

Postby Multatuli » 26 Oct 2010 12:00

Shiv wrote
One of the fundamental points that Das makes is that by joining the technlogical rat race and in trying to "keep up" with the west - India is always going to fall behind as they (the west) set the goal, they set the pace and move the goalposts. I don't think Das is wrong in saying that. This statement should not be misinterpreted to mean that technology should not be developed. That is the strawman that is being thrown up against Das's statements.


India has to "keep up" with the West for the simple reason that western hardware finds it's way to our neighbours. The "swarm tactics" Prof. Das apparently advocates won't work. A simplification: Suppose that Indian, Packee and Chinees armies are only armed with swords and knives. Packees buy 100 M-16 rifles ( or more likely, the US donates them to Packees ). Indian Army Chief, in response to this escalation, asks the GoI to buy 200 AK 47's and a couple of hundred bulletproof vests. GoI's response: don't worry, just add 2000 extra men to the army ( also armed with swords and knives ), that will allow you to overwhelm the packees with your numerical superiority. Will this work and is this ethical toward the India Army ?

I do agree with Shivji that DRDO/HAL/ADA, etc. and the GoI itself should be able to explain their choices without resorting to "Are you questioning me?! Do you know who I am?!". That requires a change in mindset and culture.

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Re: LCA News and Discussions

Postby Kanson » 26 Oct 2010 12:05

shiv wrote:
Kanson wrote:First of all, how come if you don't know or those surrounding you don't know, it indicates serious opacity? Second, it is not as per my timeline. It is well established. And you may check with anyone connected to LCA.
<snip>
You know very well, LCA is not the first a/c with double delta. In previous page, you yourself talked about Avro bomber and its manoeuvrability. If that is so, how come LCA become as you said, "We want to go where no one else has gone".


Great logic. But not answers. You don't know the answer. "I don't know" would have given the same information as you have given here. Opacity from you also.

Are you implying that the LCA is a high altitude bomber like the Vulcan? But Vulcan did not have fly by wire and flew in the 1960s and is out of service. LCA too could have flown like the Vulcan if it was not for this FBW delays no? How come LCA needs fly by wire and Vulcan did not need FBW? We certainly have gone where Vulcan did not even try to go. Can you clarify the opacity?

Of course I agree Vulcan and LCA are similar in their status at this point in time. Both are not in service.


Sir, Not knowing by me or anyone about LCA is not a reason to be cited for the opacity of the Project and to cast doubt on the project veracity and about the integrity of developers which you have consistently done in past several posts.

If you wish, you can contact anyone associated with LCA, even remotely, to have your doubts cleared. And non available of those people over internet is not again reason to be stated as Opacity of the project. If Harry. B can access, why it is impossible to others to gain understanding behind the LCA design. And i dont see why LCA design should be considered so esoteric when there are double delta examples like Saab Viggen , Draken and F-16XL before LCA was even conceived. However it can be described as esoteric in the fashion that when the Delta developers were moving to Canard-delta, LCA stuck with double delta. That has to do with its size and the adapted wing form which find little use for Canard for meeting the stated specification.

Vulcan is one moved away from pure delta. LCA is the one which meant to replace a pure delta fighter. LCA primary role as specified by IAF is a fighter interceptor like MiG-21 with multi-role as secondary option. So LCA is meant to be a modified delta fighter sharing the role as replacement of MiG-21 and meeting the expectations of IAF with speed, turn/roll/climb rates with easy maintenance and things like that.

How come LCA needs fly by wire and Vulcan did not need FBW?
LCA is meant to be a Supersonic highly manoeuverable and agile fighter with multi-role capabilities. So it needs FBW. Vulcan is just a bomber. Its akin to asking does Kaveri engine needs Single Crystal Blade tech? Actually you dont need SCB to get the stated thrust, if that is the only criteria we are looking for. But to meet the specifications like T/W ratio, MTBF etc...SCB tech enables Kaveri to achieve the specification.
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Re: LCA News and Discussions

Postby Kanson » 26 Oct 2010 12:22

Kanson wrote:http://www.flightglobal.com/pdfarchive/view/1991/1991%20-%203003.html
LCA delays push Indian air force toward MiG-21 upgrade

Indian air force considers upgrade of MiG-21 fleet

The Indian air force is considering carrying out an extensive upgrade to part of its fleet of almost 500 Mikoyan MiG-21 Fishbed fighter aircraft in the wake of delays to the indigenous Light Combat Aircraft (LCA) programme.

Areas being considered for modernisation on MiG-21s include avionics, engines and airframe; in the case of the latter, one possibility being studied is wing re-shaping to improve manoeuverability. Avionics upgrades could see the fitting of a Western radar, while options for a new powerplant include the Klimov RD-33, which powers the MiG-29, 48 of which are already in service with the air force, and the Turbo-Union RB.199.

The first production LCA is not now expected to fly until 2005. Two technology demonstrators are being built and are expected to be ready in 1995-6. Indian minister of defence Sharad Pawar has told the Indian parliament in New Delhi that a final decision on the number of prototypes to be built will be taken after the flight trials of the demonstrators. In the meantime, India is still expected to begin some MiG-21 retirements in 1995 as scheduled.

The Indian Chief of Air Staff, Air Chief Marshal N C Sun, says that the air force combat capability would in no way be weak ened following LCA programme delays, but adds that there is a move to upgrade the MiG-21s. Another factor which is likely to be fuelling air force desires to fill the capability gap until the LCA enters service is interest by the Pakistan air force in procuring upgraded F-7 fighters from China (Flight International, 16-22 October). The F-7 is the Chinese copy of the MiG-21.


I just added meat to what i was saying previously. The change in timelines for LCA was communicated to IAF in early 1990s before even the first TD rolled out. So no point to raise the bogey that becoz of problems in LCA project, IAF got stuck with MiG-21.

It is pure IAF decision to persist with MiG-21. If needed, It could have gone with replacement of MiG-21 either by increasing the number of existing a/c or it could have went for a new a/c as replacement for MiG-21 and HAL was producing MiG-21 till 80s. Infact IAF looked for new a/c as replacement.

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Re: LCA News and Discussions

Postby neerajb » 26 Oct 2010 12:24

shiv wrote:That means that Tejas's success hinged around success of FBW (ignoring the engine) - both of which were the weakest links.


But wasn't FBW designed and tested on time and actually it is the engine and radar that holds the Tejas hostage even today. The designers thought (and rightly so) that they could design and implement the FBW within the specified timeframe and they delivered it. It was under testing at Callspan USA circa 1996-98, so how the so called weak link delayed Tejas is beyond my comprehension.

Cheers....

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 13:36

neerajb wrote:
shiv wrote:That means that Tejas's success hinged around success of FBW (ignoring the engine) - both of which were the weakest links.


But wasn't FBW designed and tested on time and actually it is the engine and radar that holds the Tejas hostage even today.


Actually engine radar and FBW have all delayed the Tejas. Engine was the least because F404 was decided. Radar - did not delay the first flight. The actual flight of LCA was delayed mainly by he FBW development and validation. No FBW, no flight. See Vina's earlier note about the F-16. They had a ready made fix if FBW did not work. The Mirage's delta too was already known to fly. FBW with a change of CG only made it better. No such "hack" was available for the Tejas. This is exactly the point that was made by Das.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 13:52

shiv wrote:No FBW, no flight.

Yes. That is a fair point. The airframe rolled out in 1995 or was it 1997, the first flight happened only in 2000 (and that is despite the 1998 sanction, so what happened in those two years was a stupendous achievement) . Knowledgeable folks had commented on the roll out that it was premature because the FBW wasn't ready.

shiv wrote: See Vina's earlier note about the F-16. They had a ready made fix if FBW did not work. The Miarge's delta too was already known to fly. FBW with a change of CG only made it better. No such "hack" was available for the Tejas. This is exactly the point that was made by Das.

The problem is that period from 1965 to 1989 odd was a dark age in India aviation. No project took off the ground, everything was killed by the powers that be the IAF was looking at wholesale imports and no worthwhile research experiments were implemented was done because there was no "need".

Yes. India should have taken an Ajeet airframe and developed an FBW on that in the late 70s/early 80s, just like the Brits did with the Jaguar as a test bed and French with the Mirage III. They could have started with composites as well and made composite wings for the Ajeet and a few structures on an experimental basis.

Another major blunder was not to develop the Gnat into an AJT when we had all the subsystem pieces for that and a proven baseline platform to develop it on. An engine project for that would have laid a great foundation for the Kaveri.

Problem is because of the comatose state until 1989, the LCA /Tejas carried/carries too much of a burden on it's shoulders and the entire industry has had to be redeveloped from scratch and we are having to catch upwith 2 generation of design and technology we simply ignored. There is a larger lesson in that when looking into the "delays" in the LCA. Russian weapon imports were really a kiss of death to indigenous capability and development. I am glad the Soviet Union collapsed. We would have NEVER got out of that rut otherwise.

Whether DRDO succeeds in the near term or not is immaterial. But the long term vision is perfectly valid. We simply have to persist, invest, recover from the inevitable stumbles and continue until we get to the light at the end of the tunnel. There is no other way out.

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 14:18

vina wrote:But the long term vision is perfectly valid. We simply have to persist, invest, recover from the inevitable stumbles and continue until we get to the light at the end of the tunnel. There is no other way out.


Well said. And I am sure we will. I would really love to see our people just pick up an existing aircraft - anything - maybe Jag, maybe MiG 21, maybe even Dornier and make it FBW

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Re: LCA News and Discussions

Postby Tanaji » 26 Oct 2010 14:21

shiv wrote:Actually engine radar and FBW have all delayed the Tejas. Engine was the least because F404 was decided. Radar - did not delay the first flight. The actual flight of LCA was delayed mainly by he FBW development and validation. No FBW, no flight. See Vina's earlier note about the F-16. They had a ready made fix if FBW did not work. The Mirage's delta too was already known to fly. FBW with a change of CG only made it better. No such "hack" was available for the Tejas. This is exactly the point that was made by Das.


Saar, from your own post:

What is well known (from Wiki) is that India wanted to develop a "Light Combat Aircraft" while developing 5 critical technologies.

FBW
Composites
Engine
Glass cockpit
Radar


so if the stated principal aim of the project is to develop FBW, why would someone work on a fall back alternative for the principal aim? This is akin to telling BARC, your aim is to build a nooklear bum, and BARC goes and says just in case I cant build a nooklear bum, here is a bum made from diwali gun powder. Yes its an alternative, but thats not what was needed.
You have fall back alternatives for an approach you take towards the end goal, but you dont have a fall back alternative to the end goal itself!

Was there a chance that the IAF would have accepted an aircraft without FBW? No... So Das going to town on lack of alternative to FBW is misplaced.

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 14:32

Tanaji wrote:
What is well known (from Wiki) is that India wanted to develop a "Light Combat Aircraft" while developing 5 critical technologies.

FBW
Composites
Engine
Glass cockpit
Radar


so if the stated principal aim of the project is to develop FBW, why would someone work on a fall back alternative for the principal aim?


The US and France did it. India of course wanted to go where no team has ever gone before I guess, and take more time for a first flight of an aircraft than any team has taken before.

What the LCA a technology demonstrator or a combat aircraft project?

If it was a technology demonstrator - India's operational readiness should never have been held up waiting for technology to come in its own sweet time. If it was a combat aircraft project then something should have been delivered on time.

The LCA was neither here nor there with no agency, developer or user, fully responsible for failures. Each delay was a defeat and defeat is an orphan. Everyone will bask in success of course, but this is the time to look at the mistakes that were made and never repeat them.

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 14:35

I would really love to see our people just pick up an existing aircraft - anything - maybe Jag, maybe MiG 21, maybe even Dornier and make it FBW


Shiv,

I hope you are not confusing the issue with that of an auto-pilot..

One goes for FBW because, he has already decided to make the aircraft unstable or with neutral stability. All aircraft which doesn't have FBW has to have certain amount of stability - or else you can't fly the craft. The degree of stability varies from a/c to a/c. The more stable it is, the more the effort required to handle it.

Now if you try to fit FBW to such a craft, then you need to make it unstable first. For this, you need all the design parameters of it from the designer, who may not part with it. Even if you get hold of it, the effort and changes required may be substantial and not worth it. Making a new plane could turn out to be better - after all, why do you want to pick up some one else's specs and re-do the FBW? It is like picking up a pair of ill-fitting trousers and altering it to suit your size.
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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 14:41

>>>If it was a technology demonstrator - India's operational readiness should never have been held up waiting for technology to come in its own sweet time. If it was a combat aircraft project then something should have been delivered on time.

I think this is where the people in responsible positions should have had a plan-B, in case of the delay in delivery of LCA. But then, plan-B would have been purchase of fighter a/c, which again needs money. Part of the reason for LCA delay is also money (with Manmohan with the able advise of world bank/IMF restricting defence spending). We are back to square 1.

I feel DRDO erred in estimating the time for completion of project due to lack of experience and problems which were not anticipated. Together, it had a cascading effect.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 14:54

geeth wrote:Now if you try to fit FBW to such a craft, then you need to make it unstable first. For this, you need all the design parameters of it from the designer, who may not part with it.


Well, we had the Gnat and the Mig21 which we license produced and modded and came up with the Ajeet and Mig21 variations. We had all the plans. That is why I put Ajeet as an example.

No making it "unstable" might not be very difficult. Something like removing ballast in the nose (many planes have them), or putting ballast in the back, or simple disabling the front fuel tanks might be enough to do the trick possibly.

Even if you get hold of it, the effort and changes required may be substantial and not worth it. Making a new plane could turn out to be better - after all, why do you want to pick up some one else's specs and re-do the FBW? It is like picking up a pair of ill-fitting trousers and altering it to suit your size.

The idea is to have a proven airfram+engine combo to use as a flying test bed for your FBW system, which you then take and implement in a brand new airframe! What we didnt learn by actually doing on a testbed we are learning to do in the real enchilada. A variation of the theme "the more you sweat in peace time , the less you bleed in war" I guess.

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 15:13

Well, we had the Gnat and the Mig21 which we license produced and modded and came up with the Ajeet and Mig21 variations. We had all the plans. That is why I put Ajeet as an example.


If that was the case, then the question remains as to why they had gone all the way to U.S and tested the FBW software on an F-16 testbed. They could very well have got one of the fighters of IAF and done it here itself.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 15:33

geeth wrote:If that was the case, then the question remains as to why they had gone all the way to U.S and tested the FBW software on an F-16 testbed. They could very well have got one of the fighters of IAF and done it here itself.


That Calspan F-16 Vista was a variable stability test bed, that was readily available to us as we were developing the FBW with their help anyway, so why not use it and go and jury rig a brand new test bed, which itself will have to be first validated ?.

The "collaborations" were supposed to fill in capability gaps that we had. The 1998 tests put a huge spanner in the works. That is all.

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 16:04

geeth wrote:
I hope you are not confusing the issue with that of an auto-pilot..

One goes for FBW because, he has already decided to make the aircraft unstable or with neutral stability. All aircraft which doesn't have FBW has to have certain amount of stability - or else you can't fly the craft. The degree of stability varies from a/c to a/c. The more stable it is, the more the effort required to handle it.

Now if you try to fit FBW to such a craft, then you need to make it unstable first. For this, you need all the design parameters of it from the designer, who may not part with it. Even if you get hold of it, the effort and changes required may be substantial and not worth it. Making a new plane could turn out to be better - after all, why do you want to pick up some one else's specs and re-do the FBW? It is like picking up a pair of ill-fitting trousers and altering it to suit your size.


Geeth - take the Airbus A 320 for example. That is not an aircraft that needs artificial stability. The FBW exists for safety, reliability and weight reasons. The software prevents the pilot from making the plane exceed some limits. Artificial stability for maneuverability is only one aspect of FBW. The other aspects are understanding the control laws, understanding what you want and applying that in the software code, wiring up the plane, building software and hardware redundancy, and developing sensors to feed the software and actuators to respond to software generated commands. Experience can be built up in a plane that is known to fly anyway and is known to be flyable without FBW.

And of course - instability that causes say a persistent pitch up or pitch down in a previously stable aircraft should be easy to mimic by various means.

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 16:13

>>>That Calspan F-16 Vista was a variable stability test bed, that was readily available to us as we were developing the FBW with their help anyway, so why not use it and go and jury rig a brand new test bed, which itself will have to be first validated ?.

So, the question of using a Jaguar or Ajeet did not rise.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 16:24

geeth wrote:So, the question of using a Jaguar or Ajeet did not rise.

Not for the LCA. However, if we had run a FBW research program in the late 70s/early 80s, the Ajeet would have been the perfect experimental platform to implement it on!

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 16:34

Geeth - take the Airbus A 320 for example. That is not an aircraft that needs artificial stability. The FBW exists for safety, reliability and weight reasons.


Before the advent of FBW also, Pilots still used to fly large aircrafts, without any change in characteristics of the flying parameters. The FBW in a civilian aircraft and that in a fighter exists for different reasons.

The software prevents the pilot from making the plane exceed some limits. Artificial stability for maneuverability is only one aspect of FBW.


The very purpose of incorporating FBW in a fighter is to manage the Artificial stability regime. Otherwise the pilot can do very well without it, like any other stable aircraft. It (FBW) improves manoeuverability, because you can afford to design the craft to fly in the unstable regime.

The other aspects are understanding the control laws, understanding what you want and applying that in the software code, wiring up the plane, building software and hardware redundancy, and developing sensors to feed the software and actuators to respond to software generated commands.


This whole thing is called the FBW system..

>>>Experience can be built up in a plane that is known to fly anyway and is known to be flyable without FBW.

What purpose it would serve, I don't know..They built Iron Bird-1 & Iron Bird II for testing the software I suppose. Putting it in a flying plane and testing it there, then changing the software to suit the new plane designed is all cumbersome and double risk (you have to risk the pilots life in the existing as well as the newly designed plane) IMO.

>>>And of course - instability that causes say a persistent pitch up or pitch down in a previously stable aircraft should be easy to mimic by various means.

May be..But I thought it would not be that easy. After doing all these things what do you achieve? Do you mean to say we should have had a flying test bed like the U.S has in the F-16? We don't have a large a/c industry yet for that kind of investment and more over, we were struggling with the LCA itself..It would have been double work for the designers - mind you, it is not just a software work. The aircraft engineers would be equl partners in designing the FBW. With limited resources, that would have stretched the design team to its limits IMO.

In any case, they have come out with flying colours - so what they did was the best, isn't it?

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 16:34

Of course now that we have the LCA I am sure the LCA itself will remain a platform for testing future developments, but my desire to see other platforms being used is part of a long wishlist I have to see aeronautical sciences being expanded massively in India.

OK - there was a structural failure that ended in a disaster for the Avro AWACS. But clearly that radome was a totally new structure fitted on that plane in India.

In a similar way would it be possible to rig up a HS 748 to carry a test jet engine like the Kaveri? Sorry, Wrong thread. Need to start a new thread..

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 16:36

geeth wrote:In any case, they have come out with flying colours - so what they did was the best, isn't it?


No Geeth. Creditable as the success is, the end does not necessarily justify the means. The project was a success despite many hiccups. We need to study the timelines to see how many of those hiccups were avoidable or could have been bypassed.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 16:44

What purpose it would serve, I don't know..They built Iron Bird-1 & Iron Bird II for testing the software I suppose. Putting it in a flying plane and testing it there, then changing the software to suit the new plane designed is all cumbersome and double risk (you have to risk the pilots life in the existing as well as the newly designed plane) IMO.


Well, the flying test bed is real simulation in-flight. Each of the six degrees of freedom can be varied (basically the PID parameters) , you can test the control laws thoroughly and with the original systems in place for "safety" as a backup and also simulate various situations.

With the iron birds at best ,you can replicate it on the ground, but how it actually behaves in the air will be known only when it flies and any refinement/modification will have to happen during the flight test and not on the test bed that could have happened if the Calspan VISTA had been available as originally planned.


In short with the inflight simulation test bed, you can simulate the behavior of the target platform very closely and find out how the FBW behaves , without flying the target platform.

Looking back, that could be a reason for the "slow" rate of release /development of the FBW and the ultra cautious testing.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 16:46

geeth wrote:.It would have been double work for the designers - mind you, it is not just a software work. The aircraft engineers would be equl partners in designing the FBW. With limited resources, that would have stretched the design team to its limits IMO

Actually more than aircraft engg, it is more control engineers who tend to be Electrical Engineers /Mathematicians and Engg Mech kind of folks.

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 16:49

geeth wrote:The very purpose of incorporating FBW in a fighter is to manage the Artificial stability regime. Otherwise the pilot can do very well without it, like any other stable aircraft. It (FBW) improves manoeuverability, because you can afford to design the craft to fly in the unstable regime.


yes and no.

Definitely "Yes" as you say it if you are developing FBW as a technology for fighters

A qualified "No" if you are developing a replacement fighter for the air force and do not want to be left without any aircraft in case your FBW development program (a previously unknown quantity for India) is delayed.

In fact this is exactly where the Prodyut Das argument came up. He quoted the F-16 example to say how the US makers could easily have remedied the instability by increasing the area of the tailplane and given the US a flying fighter even as testing went on for software. What Das was having a rant about was that if the original designers who had to come up with a generic "Light Combat Aircraft" (not necessarily Tejas in its current form) had developed a conventional design with tailplane and then introduced instability for the purpose of developing FBW, they could have achieved stability a delivered the same plane on time while the FBW work went on. By choosing an unstable tailless delta design the Indian designers tied the program down to a plane that would be unflyable without the FBW (at least according to Das).

The fact that is is a success now is sweet but he asks if this fait accompli where the plane is held hostage to FBW development could have been avoided. Did the designers not foresee failures or delays? Why not?

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 16:51

vina wrote:Looking back, that could be a reason for the "slow" rate of release /development of the FBW and the ultra cautious testing.



Vina I am sure you are 400% correct. This is why AoA testing and spin tests as far as I know have not occurred and we are still looking at some assistance for complete expansion of the envelope. I may be mistaken and am willing to stand corrected.

PS This is not chaiwala info. It is my own guesswork from tidbits of public news.

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 17:35

In short with the in-flight simulation test bed, you can simulate the behavior of the target platform very closely and find out how the FBW behaves , without flying the target platform.


My understanding was that in a flying platform also, you can only verify whether the software codes you have developed is behaving exactly as you want it to be. For eg., if you want to test your FBW software in an F-16, you have to feed the control laws of F-16. Then you will be knowing the behaviour of the F-16 aircraft as per the control laws fed. That way, it cannot simulate the behaviour of target aircraft (LCA). For it to simulate the behaviour of LCA, control laws of LCA will have to be fed in..

The behaviour of LCA would have been known fully only when it started flying (apart from wind tunnel testing). The risk involved here were (1) unpredictability of the FBW software - They had already tested about 90% of the software before the nuclear tests. The software also was not returned. Then the team returned, remade the software and tested it fully on ground to verify the control laws and software.

(2) unpredictability of the aircraft itself - this can be verified only when the craft is flown. If both the aircraft and FBW were totally unknown, then it is double whammy.

What Shiv says (as I understand it) is that first prove the aircraft without FBW as a stable platform ; make the FBW, then redesign the a/c to make it unstable, then fit the FBW and fly again.

What I am trying to say is, that once you make the a/c unstable, you may have to redesign the wing aerofoil wing position, area of the control surfaces required (for eg., you may not need as big a rudder as that required for a stable platform) etc etc...By adjusting the weight here and there, you may be able to make the plane unstable, but that may not be an efficient flying platform, IMO.
Last edited by geeth on 26 Oct 2010 17:39, edited 1 time in total.

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 17:37

>>>Actually more than aircraft engg, it is more control engineers who tend to be Electrical Engineers /Mathematicians and Engg Mech kind of folks.

By aircraft engineers, I didn't mean to say just those dealing with the aerodynamics of the craft

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Re: LCA News and Discussions

Postby geeth » 26 Oct 2010 18:04

A qualified "No" if you are developing a replacement fighter for the air force and do not want to be left without any aircraft in case your FBW development program (a previously unknown quantity for India) is delayed.


I am not commenting on whether we should have designed LCA with or without FBW..What I am saying is, the purpose of FBW system in a fighter plane.

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 18:17

geeth wrote:What Shiv says (as I understand it) is that first prove the aircraft without FBW as a stable platform ; make the FBW, then redesign the a/c to make it unstable, then fit the FBW and fly again.


No Geeth. Make an aircraft unstable by - for example making it tail heavy so that the nose pitches up. This in fact is exactly the sort of instability that the LCA has I think. Then start developing control laws for that unstable aircraft, knowing that the tail heavy condition can very easily be countered by increasing the surface area of the tailplane which will give some lift at the back, correcting the tendency to pitch up. If you need the plane to be stable, build it with the broader tailplane. But for the unstable aircraft, use the narrower tailplane.


geeth wrote:My understanding was that in a flying platform also, you can only verify whether the software codes you have developed is behaving exactly as you want it to be. For eg., if you want to test your FBW software in an F-16, you have to feed the control laws of F-16. Then you will be knowing the behaviour of the F-16 aircraft as per the control laws fed. That way, it cannot simulate the behaviour of target aircraft (LCA). For it to simulate the behaviour of LCA, control laws of LCA will have to be fed in.


As my understanding goes - the flying limits of the F-16 are known and encoded in the F-16 software. Those "limits" may be "Do not fly at X angle of attack at Y airspeed at Z altitude" and hundreds of other such rules. As long as those rules are retained to control the limits of the F-16 so it does not go out of control - any other control laws that you use apart from those particular limits will make he F-16 fly and respond like the particular aircraft whose FBW software you have added to the F-16's code.

AM Rajkumar is on record saying that the LCA software made the F-16 handle better than the original F-16 code. :D

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Re: LCA News and Discussions

Postby Kanson » 26 Oct 2010 18:19

Thinking aloud, I wonder, what we could have gained by developing a separate stable version of LCA for meeting the shortfall in developing FBW system, if the ultimate a/c meant for production is only unstable LCA?

At best the delay of developing FBW can be said as a max of 2 yrs. LCA was supposed to fly in 1997. If there was no sanction it could have done it in 1999. This is from the benefit of hindsight. What we could have done by developing two different LCA for the heck of 2 yr delay where such unexpected delays are normal when developing such complex systems? More time and resources spent for 2 different versions for Zero benefit as finally we are going to field only unstable LCA.

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Re: LCA News and Discussions

Postby Kanson » 26 Oct 2010 18:25

And the time of delay is not in developing FBW software but testing them to satisfaction. - those ~ 2 yrs.

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Re: LCA News and Discussions

Postby shiv » 26 Oct 2010 18:27

geeth wrote:
A qualified "No" if you are developing a replacement fighter for the air force and do not want to be left without any aircraft in case your FBW development program (a previously unknown quantity for India) is delayed.


I am not commenting on whether we should have designed LCA with or without FBW..What I am saying is, the purpose of FBW system in a fighter plane.


Let me say what I understand of the LCA.

Delta wings, for all their advantages, have some drawbacks. Among these drawbacks are

1) Poor handling at ground level and poor take off performance
2) Some weird vortex separation issues at high angle of attack that I do not understand.
3) A tendency for the wing to act as a large sail causing slowing during turns.

These drawbacks can be addressed by a combination of instability in the pitch axis and fly by wire.

If you make the LCA unstable so that it tends to pitch nose up some of these issues are ameliorated. But the plane is unstable and the pilot may lose control.

In the LCA this has been corrected by the use of the cranked double delta with FBW control surfaces at the leading edge. So all in all the LCA is a pretty nifty piece of technology that we can be proud of.

Any errors in this interpretation are mine and I am open to correction.

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Re: LCA News and Discussions

Postby vina » 26 Oct 2010 18:52

geeth wrote:My understanding was that in a flying platform also, you can only verify whether the software codes you have developed is behaving exactly as you want it to be. For eg., if you want to test your FBW software in an F-16, you have to feed the control laws of F-16. Then you will be knowing the behaviour of the F-16 aircraft as per the control laws fed. That way, it cannot simulate the behaviour of target aircraft (LCA). For it to simulate the behaviour of LCA, control laws of LCA will have to be fed in..

No. You can make the test platform simulate the behavior of the target platform. The damping and other parameters in yaw, roll, pitch, etc will be what the LCA platform will be expected to do (got from modeling I suppose) and you can vary the stability of each parameter individually. It can answer questions like.. you expect the damping response in roll to be X, but what happens if it were Y instead, how will the LCA behave. Well, the test bed will give out a Y repsonse if you want it to.

The codes that will fly the aircraft when it is simulating the target platform will be the target platform FBW , with the test bed FBW running as a "safety backup". Yes, it will mimic the target platform.

This is sort of the AJTs of today, which can mimic the behavior of multiple platforms. Something which Airbus does across it's fleet and tries to maintain the same handling and other characteristics across platform so that in theory an A318 pilot can easily fly a A380 with minimal retraining.

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Re: LCA News and Discussions

Postby Austin » 26 Oct 2010 19:22

Marten wrote:With the FGFA deal seemingly tied up, there will be serious disincentive for certain folks within the MoD and IAF to let the AMCA develop


After the Tejas experience and MMRCA saga what the IAF most certainly done is delinked its 5th Gen program/requirement from AMCA and co-opted for FGFA on a risk/fund sharing basis , so they are certain that they will get a 5th gen fighter within a certain time frame.

They may continue with AMCA funding but atleast AMCA will not throttle IAF operational requirement.

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Re: LCA News and Discussions

Postby nrshah » 26 Oct 2010 19:43

Austin wrote:After the Tejas experience and MMRCA saga what the IAF most certainly done is delinked its 5th Gen program/requirement from AMCA and co-opted for FGFA on a risk/fund sharing basis , so they are certain that they will get a 5th gen fighter within a certain time frame.

They may continue with AMCA funding but atleast AMCA will not throttle IAF operational requirement.


If and when this happens, it will be the biggest mistake, no blunder we do, bigger than HF 73 or whatever it was....

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Re: LCA News and Discussions

Postby Austin » 26 Oct 2010 19:55

nrshah wrote:If and when this happens, it will be the biggest mistake, no blunder we do, bigger than HF 73 or whatever it was....


Its no blunder its a calculated risk taken by IAF/GOI based on past experience.

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Re: LCA News and Discussions

Postby Neela » 26 Oct 2010 20:01

vina wrote:
geeth wrote:My understanding was that in a flying platform also, you can only verify whether the software codes you have developed is behaving exactly as you want it to be. For eg., if you want to test your FBW software in an F-16, you have to feed the control laws of F-16. Then you will be knowing the behaviour of the F-16 aircraft as per the control laws fed. That way, it cannot simulate the behaviour of target aircraft (LCA). For it to simulate the behaviour of LCA, control laws of LCA will have to be fed in..

No. You can make the test platform simulate the behavior of the target platform. The damping and other parameters in yaw, roll, pitch, etc will be what the LCA platform will be expected to do (got from modeling I suppose) and you can vary the stability of each parameter individually. It can answer questions like.. you expect the damping response in roll to be X, but what happens if it were Y instead, how will the LCA behave. Well, the test bed will give out a Y repsonse if you want it to.

The codes that will fly the aircraft when it is simulating the target platform will be the target platform FBW , with the test bed FBW running as a "safety backup". Yes, it will mimic the target platform.

This is sort of the AJTs of today, which can mimic the behavior of multiple platforms. Something which Airbus does across it's fleet and tries to maintain the same handling and other characteristics across platform so that in theory an A318 pilot can easily fly a A380 with minimal retraining.


Vina, with the examples that you gave you had also written, "how will the LCA behave". I assume what you meant by that is these data will be fed back into the simulator where various speeds ,AoA, altitudes are set and then see how the aircraft behaves?

I have had this understanding about the test points. Please correct me if I am wrong.
It is virtually impossible in one's lifetime to test all possible altitudes , AoA, airspeed , thrust, load factor etc (the flight envelope) even with a simulator. So they might first set the corner conditions- max and minimum values for each. Each of these are then split into sensible levels. For altitude for example, you need not test for 1000m and 1100m but you might select 1000m and 3000m as test points because at 3000m the change in air density and oxygen levels is more significant. Am I correct in these assumptions? Something similar happens in the semiconductor industry but the test points ( called corner conditions ) are usually <100 with all parameters included.
BUt with aircraft, I see so many parameters and so many things to test ...truly mind-boggling.

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Re: LCA News and Discussions

Postby Willy » 26 Oct 2010 20:24

After the Tejas experience and MMRCA saga what the IAF most certainly done is delinked its 5th Gen program/requirement from AMCA and co-opted for FGFA on a risk/fund sharing basis , so they are certain that they will get a 5th gen fighter within a certain time frame.

They may continue with AMCA funding but atleast AMCA will not throttle IAF operational requirement.



The AMCA should not even be attempted without typing up an engine partnership and to a lesser extend a partner for the radar. Go to the Russians this times if u have to but dont let the engine be the achilles heal!!

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Re: LCA News and Discussions

Postby Kanson » 26 Oct 2010 21:10

Austin wrote:After the Tejas experience and MMRCA saga what the IAF most certainly done is delinked its 5th Gen program/requirement from AMCA and co-opted for FGFA on a risk/fund sharing basis , so they are certain that they will get a 5th gen fighter within a certain time frame.

They may continue with AMCA funding but atleast AMCA will not throttle IAF operational requirement.


Is that mean all the 5th gen tech for the FGFA are developed and perfected ? From where these tech for 5th gen going to come?

What is the success of Su-30 MKI saga? It is the spin off from the LCA programme which benefited and transformed the Su-30 into Su-30MKI. AMCA & FGFA complement each other, as per my understanding. One acts as a hedge against the other. JMT

What is the status of 5th gen engine for PAK-FA ?

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Re: LCA News and Discussions

Postby Rahul M » 26 Oct 2010 21:34

shiv wrote:
What is well known (from Wiki) is that India wanted to develop a "Light Combat Aircraft" while developing 5 critical technologies.

FBW
Composites
Engine
Glass cockpit
Radar

The US and France did it. India of course wanted to go where no team has ever gone before I guess, and take more time for a first flight of an aircraft than any team has taken before.

What the LCA a technology demonstrator or a combat aircraft project?

If it was a technology demonstrator - India's operational readiness should never have been held up waiting for technology to come in its own sweet time. If it was a combat aircraft project then something should have been delivered on time.

The LCA was neither here nor there with no agency, developer or user, fully responsible for failures. Each delay was a defeat and defeat is an orphan. Everyone will bask in success of course, but this is the time to look at the mistakes that were made and never repeat them.


shiv ji, till 2001, when the phase 2 was sanctioned, LCA was a tech demonstrator.
LCA as a fighting machine was given the go-ahead and funded only after the first flight took place and demonstrated the 5 target technologies.
I find it a little dishonest on the part of IAF to claim that delays in LCA led their plans go awry. they were after all in the best position to know that LCA the fighter project didn't even exist back then. in fact truth be told few in IAF actually expected the LCA to come as far as it has, most were waiting for it to fail, so to speak. it's a little difficult to digest that IAF long term planning was tied to an aircraft that they had no faith in.
more likely is that IAF goofed up on long term planning with or without LCA but LCA makes a nice hook to hang the blame-hat on.

coming to the discussion of who set the requirements, I think we know it quite well that IAF set the physical requirements (altitude, speed, payload, range and maneuverability requirements) in the form of ASR while the LCA design team in consultation with dassault decided how they would go about achieving those.

as for the F-16 design having alternate routes to FBW, let's not forget that not only was the F-16 a pioneer as far as FBW was concerned (and hence had to account for many things that could go wrong), it was also designed in the mid 70's.
an aircraft designed in late 80's, after witnessing about 2 decades of FBW being successfully used in a plethora of aircrafts, had absolutely no excuse or reason to provision for a non-FBW aircraft. a non-FBW design has no place in today's fighters and if we could not manage it we should have gone out of designing aircrafts altogether.
Das' arguments stem solely from the fact that he believes 3rd gen auto-ricksaws are the ultimate fighters. in that he seems to be in an exalted group of one.

it's like saying a computer designer should make provisions for an analogue design in his machine because that's what the first digital computer designer did. sorry to say, this is bull, juvenile quality bull.

___________________________

about ajeet AJT, if memory serves right HAL did have a ajeet AJT design in easrly 90's but IAF rejected it in favour of foreign AJTs.

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Re: LCA News and Discussions

Postby Austin » 26 Oct 2010 21:54

Kanson it is just a practical choice IAF has made , while AMCA is yet to receive official sanction from GOI , the PAK-FA has reached prototype stage and with both countries investing in it has a better chance to suceed , IAF naturally want to de-risk its fifth gen fighter program from delays or technology over reach.
While it would support AMCA it won't remain a hostage to it.

The 117 engine is good enough to power the first stage of PAK-FA/FGFA


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