LCA: News & Discussions - October 2016

[Sid]

Rishi Verma, I guess tsarkar is talking from his experience in SCADA or some PLC based system. I have seen it happen in those kind of system although no idea about a FCS.

[Kartik]

But here are some encouraging facts:
1. The complete envelop of the aircraft has been opened. The expansion of envelop to 26+ degrees is beyond what was originally envisioned as the slow speed handling of the aircraft is better than expected. At 24 degrees AoA, the minimum speed of LCA is just over 200 knots. That is why you saw those commentators go oohs-and-aahs when Tejas demonstrated its shortest radius turns. If they go to 26 degrees, the slowest speed is going be below 200 knots. That's turboprop territory.
2. IAF is extremely happy with Tejas's takeoff, landing, subsonic agility and maneuvering capabilities. IAF has complaints about its maintainability which is being addressed in the 1As.
3. IAF has set clear priorities: They want BVR firing (guided by the MMR) and IFR probe first (will be completed next month). Gun-firing is next. It will happen next year. They don't expect anything to go wrong. It worked well on ground. it should be smoother in the air.

extremely happy to read these things you've mentioned! Now for BRF's nanha mujahids to run all over to spread the word.

Regarding the AoA and speed, what is the corner speed of the Tejas? Any idea?

[JayS]

Well, you have to be credible and show HOW your promise will be achieved and they will examine the risks and chances of success with that.

That's true irrespective of what technology one OEM or the other would use to achieve the numbers.

They went with it because the physics support it, they would have seen demonstrator and plus the big name of P&W would have given them the confidence to risk their business on it. Note, here too, the airlines are taking a big risk on a radical technology jump. They too are supporting tech development and indeed in some cases putting their very EXISTENCE in line, even if the support is not directly with cash up front for R&D . But support they do, including inducting early bug ridden versions and supporting it through incremental development in the promise of preferential access and differential pricing later on when everything is fixed.

GE is a far bigger name than PW in Civil engines. And guess what GE is promising better efficiency with two-spool engine in this generation. Which one do you think and airliner would prefer?? GTF with more fuel consumption or Two spool LEAP with lower fuel consumption. In fact there is nothing new in GTF, neither these are first operational GTF engines from PW. No one took notice of GTF until conventional two spool was still giving good enough fuel economy at lower cost of maintenance and better reliability. There is no love for technology, only for money that can be saved. In fact LEAP will outsell GTF very easily, despite GTF being a more futuristic architecture. OTOH if either of the two fall behind on the promised numbers, the respective OEM will end up paying hefty money to the airliners. I would consider an airline supporting certain tech if they buy it despite it giving worse performance than other options, just to give it a chance. Or if they give few billion $$ to fund some engine tech development program for example open rotor. Support for technology though orders is just a by-product, especially when you hardly have any choice - there are only two engine options available typically.

BTW there isn't a radical technological jump here in GTF, only incremental progress.

IAF never seems to induct anything made locallyother than a fully baked product.. equivalent to buying the 100th sample rolling of the assembly line. That is what they do when they go abroad and import fighters . That some of them are half baked and bug ridden and needs significant efforts later on to support bring them upto scratch is a different story.

Airliners also do not buy anything half baked, unless its fully proven and certified. For every delays or short-fall in promised numbers the OEM pays penalties to the airliners. This is no different than IAF demanding FOC and full ASQR specs fulfilment before induction.

[Indranil]

Tsarkar sahab, I know what you are speaking of. But artificial stabilization has to be closed loop. Otherwise, the responses will get out of sync and will induce/increase oscillations rather than mitigate it. That is why I was arguing with people, that the actuator rate cannot be 2Hz for an aircraft which has a mean time to double amplitude of 200 milliseconds.

Even if LCA would have been a stable aircraft, the pilot would not have been able to control it beyond to 24 degrees because cn beta plummets after 25 degrees. They can go to 26-28 degrees because they derive stability through yaw control which is there till about 30 degrees. To the best of my knowledge, the limits have anything to do with the actuator rates.

I've had a conversation once with a rather senior person who was among the first few that worked on composites in ADA on the LCA, and as per that gentleman, the intended fatigue life was much more than 3000 hours. He didn't go into a specific number, perhaps because he must've been aware that they hadn't yet tested it as yet.

It is. You know the technologies used in building the airframe. You, of all people here can put two and two together. They have never been worried about the fatigue life of LCA. Don't expect the fatigue life to be anywhere below 5000-6000 hrs.

I am a big critic of NAL and how it is structured under the dept. of science with next to no funding. But the composites technologies developed at NAL is really top notch. I am very happy to see that the productionization of these techniques is in private hands. My wish list for Mk2 includes a completely co-cured wing manufactured with the Verity process. That will be absolutely fabulous: cost-wise, maintenance-wise, and weight-wise.

IR, LCA FBW is basis for all FVW designs by ADA and parallel orgs, is what I meant. The DFCC on LCA is also the basis for many more programs.

Unfortunately the mistaken belief is still being propagated that analog FBW was easier tban digital. In what sense? It would have taken a huge amount of testing to implement and IAF would be yelling from the rooftop about how LCA was obsolete before induction and non upgradeable. Plus as if Dassault would gave handed us the tech on a platter.

I agree.

[Indranil]

Regarding the AoA and speed, what is the corner speed of the Tejas? Any idea?

Let's wait for ADA to publish it. It's very good.

By the way, that 300 km combat radius is just a guesstimate. They haven't done any dedicated test flights to find out the range with different configs. Unfortunately, we many here don't want to discuss numbers because it questions their fanboyism and brochuritis. But these are the fuel fractions:
LCA: 27%
Gripen C/D: 25%
F-16 C: 25%

SFCs of all the engines are similar. So, I am still waiting for the fanboys to teach me how LCA is significantly short legged than these aircraft?

[vina]

GE is a far bigger name than PW in Civil engines. And guess what GE is promising better efficiency with two-spool engine in this generation.

Historically it was the other way around (until the CFM alliance and Airbus taking off in the mid 80s in a big way).GE was a largely a niche military engine maker (like Snecma) while it was PW that was the godzilla that straddled both the civil and military horizons . Basically most "civlized" improvements in gas turbines (twin spool engines, surge and stall protecting doors /panels etc) are PW inventions. That apart.

Which one do you think and airliner would prefer?? GTF with more fuel consumption or Two spool LEAP with lower fuel consumption. In fact there is nothing new in GTF, neither these are first operational GTF engines from PW. No one took notice of GTF until conventional two spool was still giving good enough fuel economy at lower cost of maintenance and better reliability. There is no love for technology, only for money that can be saved.

Tech choices are made FOR a good reason .. Capability that you get, even for that extra incremental cost. The best architecture that exists TODAY for large capacity GT engines are the Rolls Royce Trent series , three spool designs, that nearly sank RR and put it in bankruptcy when they developed it for the Lockheed Trident. But that architecture is SO good and the tech lead that it gave them made them ultra competitive in larger capacity engines and didnt need big incremental investments to make engines for A330/340/380 and B777 . GE had the financial muscle to develop custom engines, PW dropped out as it couldnt out invest GE in product development.

Now GTF is a long term bet for PW to be competitive with 3 spool designs at a small marginal cost over 2 spools (but with similar performance.. 3 spools optimise each of HP,IP and LP stages.. GTF decouples compresser and fan over a larger speed and hence can optimise the fan and the compressor better).

Longer term as GTF matures, 2 spool wont cut it. GE will be forced to move up. RR with 3 spools will probably be more expensive manufacturing wise for a 737/A320 sized engine, but have he advantage of not having to spend too much on de novo R&D and can downsize an existing engine and could still be competitive.

BTW there isn't a radical technological jump here in GTF, only incremental progress.

That is like me telling the CS & IT Vity boys that basically all that needed to be invented in computing world was done and finished by IBM as of late 70s. Everything else is just a gradual , incremental refinement of that. Sure. If you look at i that way, nothing new has been invented fundamentally since Frank Whittle/ Von Ohain in GTs and everything is only incremental progress.

[vina]

Thanks for the pic tsarkar. What is amazing is the huge spin off that the LCA program has given in terms of avionics. I can see that the M2K has been upgraded with the mission computer and the Mil Std 1553 bus, all developed for the TEJAS program and this has fed back into multiple programs (Mig 27, Jag, and now even the hallowed M2K!) . That ALONE is paisa vasool and if I were the IAF would be incredibly happy.

What the carcass of the Lavi did for the Isreali industry (radar, avionics and weapons) and turned it world class in 20 years hence, I hope the LCA (though I hope it doesnt end up like the Lavi) does for the Indian ecosystem.

That brings up the question. With the Mil Std Bus, have the upgraded M2Ks discarded the French stuff like Damocles pod and Mica and Matra etc and French A2G weapons and standardized on the Rafale Litening LDP, Python V and Paveway & Isreali LGB A2G weapons ?

With that upgrade, you can mate any Mil Std weapon to the M2K and need not go all French for weapons at all!

As Arnab would say "The NATION wants to know!"

[shiv]

Apologies. Couldn't resist. Itch is too strong
https://twitter.com/bennedose/status/796902178384293889

[Indranil]

I forgot one last thing. The contribution of Mao sir to the LCA Navy program is much much much more than a pilot from NFTC. He kind of runs that show. Very ably as well, if I may add. India will be indebted to him.

[ks_sachin]

I forgot one last thing. The contribution of Mao sir to the LCA Navy program is much much much more than a pilot from NFTC. He kind of runs that show. Very ably as well, if I may add. India will be indebted to him.

Infranil who is the bearer of the flag from the IAF side now?


BTW your posts are a pleasure to read..you have your ears close to the ground in CV Raman Nagar.

[tsarkar]

As per Islamic Fundamentalists & Terrorists, everything starts and ends with Islam. So if archaeological evidence exists, like Bamiyan Buddha or Palmyra in Syria, of flourishing pre-Islamic culture, then it is destroyed by them.

Similarly, many BR posters believe that certain capabilities just did not exist before Tejas.

Let us factually explore what capabilities existed before Tejas, so that we dont end up becoming like the fundamentalists.

To add capabilities to the Mirage 2000, HAL has to add its own mission computing system above the standard system.

The Mirage 2000 "standard system" projected images from ALTIS 2 Pod to the cockpit, and on pilot instruction at that image directed ALTIS 2 to lase the target and thereafter drop Matra BGL.

Thereafter when Litening Pod with better resolution came, along with better bombs like Griffin & Paveway that seamlessly integrated with the same "standard system" that did the same function whose effectiveness we all saw at Kargil in 1999

The HAL MC only replaces old Type 2084 computer whose processors are outdated. There are no new performance capabilities added. The old computer could be modified to very successfully handle Litening & Griffin/Paveway as we saw during Kargil.

If you know any additional capabilities added, please do illuminate.

Next, this is mission avionics, not flight control which remains a black box for HAL.

The MDPU (Modular Data Processing Unit) in the image is the same flight computer that is in the Rafale. It replaces Sextant Avionique Type 90 air data computer. The reason it was chosen is because it was much faster than what HAL/DARE has. When Mirage 2000 flight envelope very well established and its CLAWS are well mated to the Flight Control Computer, then for what purpose would anyone need to fiddle with it?

Plus as if Dassault would gave handed us the tech on a platter.

They did in 1988.
http://www.thehindu.com/2003/05/05/stor ... 010300.htm
http://www.thehindu.com/thehindu/2003/0 ... 811200.htm

...if only we had accepted Dassault's offer of an analogue system in 1988...

Unfortunately the mistaken belief is still being propagated that analog FBW was easier tban digital. In what sense? It would have taken a huge amount of testing to implement.

No, it would not have required basic testing since it was already proven on Mirage 2000.

On the other hand, Tejas software required testing via Lockheed Martin on an F-16.

When that didn’t happen due to 1998 tests, then we had to test untested software on an untested aircraft. That compounded the testing effort and time required.

IAF would be yelling from the rooftop about how LCA was obsolete before induction and non upgradeable.

The reason I posted the Mirage upgrade detail was precisely to prove how easy it was to upgrade an analogue system to digital.

So Tejas could’ve started with off the shelf Dassault software and then upgraded to a digital system later.

Thanks for the pic tsarkar.

You’re welcome. Hope you agree it wasn’t 1. Impossible to upgrade analogue system and 2. Impossible to add indigenous systems

What is amazing is the huge spin off that the LCA program has given in terms of avionics. I can see that the M2K has been upgraded with the mission computer and the Mil Std 1553 bus, all developed for the TEJAS program and this has fed back into multiple programs (Mig 27, Jag, and now even the hallowed M2K!).

As we all know, MIL-STD-1553 allows plug & play of avionics and weapons.

But are you absolutely sure that MIL-STD-1553 bus was first developed for the Tejas program and then fed into MiG-27, Jag & M2K and not the other way around?

Question to you and everyone -

Which was the first fighter in India to have MIL-STD-1553 bus and from which year?

Which was the first fighter in the world to have MIL-STD-1553 bus and from which year?

The reason I'm asking this question is to dispel the myth that capabilities like plug & play of avionics and weapons or multi-role/omni-role with FCS defined flight regimes on the fly - didn't exist before Tejas.

[JayS]

Historically it was the other way around (until the CFM alliance and Airbus taking off in the mid 80s in a big way).GE was a largely a niche military engine maker (like Snecma) while it was PW that was the godzilla that straddled both the civil and military horizons . Basically most "civlized" improvements in gas turbines (twin spool engines, surge and stall protecting doors /panels etc) are PW inventions. That apart.

Doesn't matter what they were long time in past. They hit the gold with GTF else they were almost out of the civil engine biz. Their last engine was total flop. PW is not as invested in materials as GE has bee. So PW finds its difficult to rip the best out of two spool design. Soon PW coming in composite fan blades. But GE would have moved to CMC by then.

Tech choices are made FOR a good reason .. Capability that you get, even for that extra incremental cost. The best architecture that exists TODAY for large capacity GT engines are the Rolls Royce Trent series , three spool designs, that nearly sank RR and put it in bankruptcy when they developed it for the Lockheed Trident. But that architecture is SO good and the tech lead that it gave them made them ultra competitive in larger capacity engines and didnt need big incremental investments to make engines for A330/340/380 and B777 . GE had the financial muscle to develop custom engines, PW dropped out as it couldnt out invest GE in product development.

Now GTF is a long term bet for PW to be competitive with 3 spool designs at a small marginal cost over 2 spools (but with similar performance.. 3 spools optimise each of HP,IP and LP stages.. GTF decouples compresser and fan over a larger speed and hence can optimise the fan and the compressor better).

Longer term as GTF matures, 2 spool wont cut it. GE will be forced to move up. RR with 3 spools will probably be more expensive manufacturing wise for a 737/A320 sized engine, but have he advantage of not having to spend too much on de novo R&D and can downsize an existing engine and could still be competitive.

If it was all about Tech, everyone should have gone for GTF, all hands down. Fact is LEAP has outsold GTF, because GE promising better fuel economy with LEAP. Both has their share of issues. But I do not see any reason whatsoever to believe those who went for GTF, did so because of some love for technology. This is pure business.

And there is nothing like "BEST" architecture. It all depends on an OEM's capability to make one architecture work better than the other. So they stick to one. RR could not take full juice out of two spool the way GE could so they had to go to 3-spool to be competitive. PW bridged the gap in their competency by going to GTF. All three companies have worked on all these architectures and have picked on that suits best to their abilities.

If you can stick in two gear boxes, even single spool design will work just fine and would be much lighter and whole lot less complicated mechanically.

That is like me telling the CS & IT Vity boys that basically all that needed to be invented in computing world was done and finished by IBM as of late 70s. Everything else is just a gradual , incremental refinement of that. Sure. If you look at i that way, nothing new has been invented fundamentally since Frank Whittle/ Von Ohain in GTs and everything is only incremental progress.

In US alone, both GE and PW has worked on GTF for past 40+yrs, starting right from 1960s. They could have made this engine long time ago. Only thing was the reliability was considered to offset the gain in efficiency. So they didn't pursue it then. The margins are razor thin here. YOu can easily check the research docs from NASA sponsored programs. PW has worked on the gear box for 30yrs. No there is not jump in technology. Its just now the whole thing came in light. It was always one step at a time.

And precisely this thing needs to be leant by us Indians. We tried to jump technology through LCA/Kaveri. Was OK to start with. But even at that time we didn't start our 5th gen tech development side by side. Now we will try to take that kind of jump again. We will always face big delays and troubles, until we stop trying to taking these big leaps every 2 decades or so, and start taking small small continuous step.

Currently GTF is marginally better vis-à-vis contemporary engines. Heck this PW engine family is not even the first operational GTF engine. And soon we will see Open rotor superseding GTF. Already a lot of work is going on on this. Funny enough, one main apprehension in Civil industry against Open Rotor is about those naked blades right next to fuselage. And not really the technology. GTF vs 2/3 spool isn't something like digital vs quantum computers. The later is real radical change. GTF is just an extension of same philosophy which turned a single spool to a two-spool and a two spool to three spool.

[tsarkar]

...FTS...hours...

Karthik, the point of my post was that many poster here believe IAF ASR was unobtainable when in reality the ASR spec of 3000 hours TTL compared favorably to MiG 21 TTL of 2400, Jaguar TTL of 3000 & F-16 TTL of 8000.

Those who speak of IAF being unsupportive of the program should consider that in reality IAF gave a waiver to reduce 3000 hours to 1000 hours.

And the FTS cannot be built unless flight testing is complete so the the final airframe standard can be frozen and built. This was in HAL reply to CAG.

[vina]

The HAL MC only replaces old Type 2084 computer whose processors are outdated. There are no new performance capabilities added. The old computer could be modified to very successfully handle Litening & Griffin/Paveway as we saw during Kargil.

You are fundamentally confused between the mission computer AND the flight control computer. They are two SEPARATE things. Stuff like carefree handling etc are what the flight computer does and that is the FBW part. In Mirage /F16 A/B the FLIGHT COMPUTER is analogue, the others like Tejas is digital.

When Mirage 2000 flight envelope very well established and its CLAWS are well mated to the Flight Control Computer, then for what purpose would anyone need to fiddle with it?

Because you need to implement in a NEW plane called Tejas and you WILL need to fiddle around with it ?

My understanding was that Dassault was willing to share the analogue FCS.

Which is practically useless, since we had to practically reinvent it. We offered to codevelop a digital one with them, which they were doing for the Rafale. They showed us the birdie, and we had to go to the Americans

No, it would not have required basic testing since it was already proven on Mirage 2000.

Duh! We were going to fly it on a brand new plane called the LCA remember ? And we fiddled around with transistor devices and analog gains and not computer code remember ? You would need to test the entire thing again!

On the other hand, Tejas software required testing via Lockheed Martin on an F-16.

What delayed it was that the F16 (digital FBW, and also Gripen which uses the F16 FCS) used the 4th channel which is an ANALOG as the backup. That was the part that became unavailable when the sanctions came. Ideally you would have everything different with two different teams building stuff to different control laws, for redundancy . With the analog channel unavailable, it required a decision , overcoming fear mongering (including the Americans going to George Fernandes and representing what a "danger" it was to fly without it, and George, God bless his soul, threw that fear mongering into the dustbin).

The reason I posted the Mirage upgrade detail was precisely to prove how easy it was to upgrade an analogue system to digital.

Please enlighten. Which part was converted from analog to digital in the Mirage upgrade. Like I posted earlier, the flight control computer (which is the analog part) is UNTOUCHED . What got upgraded is the mission control systems, giving better weapons and sensor capability!

So Tejas could’ve started with off the shelf Dassault software and then upgraded to a digital system later.

Taken a lot of time to reinvent an obsolete wheel with tremendous difficulty and then spend Far less time and effort to move to digital! Thank goodness someone had their thinking caps on when they took the decision to go digital from the start.

You’re welcome. Hope you agree it wasn’t 1. Impossible to upgrade analogue system and 2. Impossible to add indigenous systems

In the picture. PLEASE point out, WHICH analog system got upgraded to Digital . Then we can talk further with actual data and not shadow box.

The reason I'm asking this question is to dispel the myth that capabilities like plug & play of avionics and weapons or multi-role/omni-role with FCS defined flight regimes on the fly - didn't exist before Tejas.

Sure. Point to F16, Jaguar Darin 1 etc as "answer" to your question and say that the avionics and stuff in Darin 1/2 ,LCA and Mig 27 are same-same (ignore new mission computers and stuff from DARE that point into the upgrades) and say M2K same same as current Gripen.. and Rafale. It will sound very credible

[vina]

In US alone, both GE and PW has worked on GTF for past 40+yrs, starting right from 1960s. They could have made this engine long time ago. Only thing was the reliability was considered to offset the gain in efficiency. So they didn't pursue it then. The margins are razor thin here. YOu can easily check the research docs from NASA sponsored programs. PW has worked on the gear box for 30yrs. No there is not jump in technology. Its just now the whole thing came in light. It was always one step at a time.

The Garrett TFE731 has been in existence for 44 years now and more than 11000 engines have been built! It is not a simple matter to scale up the gear box to a full A32/737 and beyond sized engine reliably. Engines are an annuity high margin business.

GTF is just an extension of same philosophy which turned a single spool to a two-spool and a two spool to three spool.

And open fan is just an extension of putting a fan stage driven by the LP spool first seen in the RR conway! So what is your point? That there has been only incremental innovation since Whittle and Von Ohain ? I agree with that!

And oh, it looks like that RR too is putting a gear for their fan in their 3 spool design!Rolls Freezes Design of First Ultrafan

[JayS]

^^ I also think that M2K is not converted to Digital. That would require whole new FCS to be written, tested and certified. It still should be very much the same hybrid Analogue-digital (yes some of the parts of the system are digital, as per the paper posted by Tsarkar) architecture it was previously.

From what I remember of history, Dassualt was ready to work with 3 Channel Digital + 1 Analogue channel FCS which they have used on Rafale. The analogue channel is the backup thing if digital goes bonkers. It was retained due to lack of trust on reliability of digital tech. Whereas ADA wanted full 4 quadruplex digital FCS, which US was offering, and with the kind of bonhomie that time was around between Indian PM and POTUS, that must have looked a better deal. Thus Dassualts deal was dropped.

Also tsarkar, the Swing-role thing has more to it than it meets the eye. RAF does not consider their EF2000 as Swing role jets and they will have the capability only in 2020. I don't think Rafale or Gripen would have went gaga over it all the way if it was trivial thing. Swing role (all the things which make it swing role) capacity came to western fighters only in the generation of Rafale/Gripen/F16-1980s version. M2K might have had some of the features before, but it seems only in "Dash 5 it got the capability of Swing-role.

http://www.aviatia.net/greeces-delta-mi ... equipment/

With the introduction of the SEG-52 software state, the ‘Dash Five’ is now capable of performing as a swing-role fighter

Also I think the Swing role capability is controlled by the Mission Computer not the FCS.

[JayS]

And oh, it looks like that RR too is putting a gear for their fan in their 3 spool design!Rolls Freezes Design of First Ultrafan

Lets agree to disagree over the level of change.

And I am not surprised over RR decision, not to go for entirely new core design for GTF. It would have taken them more than a decade to make a new core. Plus the CS2 project has such low funding - there are 4 engine projects in that with cumulative funding of 1.6B euros from EU. Add 1.6B from companies working in it. Too low to design new core for RR. They are all trying to reuse existing stuff to reduce cost and development time.

With this, their architecture becomes same as PW GTF - 2.5 spool, if I may.

But I have to say, the Gear design by PW for GTF is incredible - a 30000hp gear box which is a lifetime part with ZERO maintenance. Which means once it goes in it will never have to be serviced..! That's some engineering. And it took them no less than 30years to get to that.

[tsarkar]

The HAL MC only replaces old Type 2084 computer whose processors are outdated. There are no new performance capabilities added. The old computer could be modified to very successfully handle Litening & Griffin/Paveway as we saw during Kargil.

You are fundamentally confused between the mission computer AND the flight control computer. They are two SEPARATE things. Stuff like carefree handling etc are what the flight computer does and that is the FBW part. In Mirage /F16 A/B the FLIGHT COMPUTER is analogue, the others like Tejas is digital.

I was crystal clear and clearly mentioned that HAL MC replaces old Dassault Type 2084 computer while Dassault MDPU replaced the old Sextant Avionique Type 90 air data computer.

The HAL MC only replaces old Type 2084 computer whose processors are outdated.

The MDPU (Modular Data Processing Unit) in the image is the same flight computer that is in the Rafale. It replaces Sextant Avionique Type 90 air data computer.

Because you need to implement in a NEW plane called Tejas and you WILL need to fiddle around with it ?

Which is practically useless, since we had to practically reinvent it. We offered to codevelop a digital one with them, which they were doing for the Rafale. They showed us the birdie, and we had to go to the Americans

Duh! We were going to fly it on a brand new plane called the LCA remember ? And we fiddled around with transistor devices and analog gains and not computer code remember ? You would need to test the entire thing again!

By your logic that implementing Dassault CLAW in Tejas would've been time consuming, then implementing Tejas CLAW in Lockheed Martin F-16 for testing would've been equally time consuming.

Implementing CLAW in aircraft like Tejas, F-16 or Gripen isnt as time consuming as developing them from a scratch, iteratively testing and refining them.

The reason I posted the Mirage upgrade detail was precisely to prove how easy it was to upgrade an analogue system to digital.

Please enlighten. Which part was converted from analog to digital in the Mirage upgrade. Like I posted earlier, the flight control computer (which is the analog part) is UNTOUCHED . What got upgraded is the mission control systems, giving better weapons and sensor capability!

Can you see the arrows from MDPU to sensors and control?

The reason I'm asking this question is to dispel the myth that capabilities like plug & play of avionics and weapons or multi-role/omni-role with FCS defined flight regimes on the fly - didn't exist before Tejas.

Sure. Point to F16, Jaguar Darin 1 etc as "answer" to your question and say M2K same same as current Gripen.. and Rafale. It will sound very credible

The IAF DARIN 1 program for Jaguar in 1980 lead by BR Member Abhibhushan (Group Captain T K Sen in real life) made the IAF Jaguar the first aircraft in the world to have MIL-STD-1553 databus allowing plug & play of avionics, sensors & weapons. Those interested can read the full story here
https://tkstales.wordpress.com/2010/03/ ... rin-story/

Now since the "dinosaur" IAF implemented "obsolete" MIL-STD-1553 in 1980, even before ADA was established and probably you were born, then kindly give credit to the fact that DARIN work on MIL STD 1553 preceded Tejas in a long way.

Jaguar and Mirage 2000 had plug and play of avionics, systems and weapons and dropping US & Israeli bombs at Kargil much before Tejas flew unlike your statement below

What is amazing is the huge spin off that the LCA program has given in terms of avionics. I can see that the M2K has been upgraded with the mission computer and the Mil Std 1553 bus, all developed for the TEJAS program and this has fed back into multiple programs (Mig 27, Jag, and now even the hallowed M2K!).

[vina]

From what I remember of history, Dassualt was ready to work with 3 Channel Digital + 1 Analogue channel FCS which they have used on Rafale. The analogue channel is the backup thing if digital goes bonkers. It was retained due to lack of trust on reliability of digital tech. Whereas ADA wanted full 4 quadruplex digital FCS, which US was offering, and with the kind of bonhomie that time was around between Indian PM and POTUS, that must have looked a better deal. Thus Dassualts deal was dropped.

I have AM Rajkumar's book and wrote what he wrote here. Our folks realised that the analog thing was a duck, that the French were working on the digital one for Rafale and we asked for that. The French showed us the Birdie, and US was willing to give it from the F16 and we went to the US.

The F16 FCS is 3 channel digital , with one channel analog. I don't know about Rafale's and Eurofighter if all the 4 are digital. But the LCA's became an all digital only because of the sanctions. If not, as originally planned it would have had 3 digital and an analog backup channels.

[vina]

The IAF DARIN 1 program for Jaguar in 1980 lead by BR Member Abhibhushan (Group Captain T K Sen in real life) made the IAF Jaguar the first aircraft in the world to have MIL-STD-1553 databus allowing plug & play of avionics, sensors & weapons. Those interested can read the full story here

The F16 first flew in 1974 , introduced into service in 1978. That was the FIRST aircraft to fly with Mil Std 1553 bus.

AM Abhibushan /TK Sen posts here , I know what he did, deeply respect his contribution. The Jaguar Darin 1 was the first one in Indian service with Mil Std bus.

[JayS]

From what I remember of history, Dassualt was ready to work with 3 Channel Digital + 1 Analogue channel FCS which they have used on Rafale. The analogue channel is the backup thing if digital goes bonkers. It was retained due to lack of trust on reliability of digital tech. Whereas ADA wanted full 4 quadruplex digital FCS, which US was offering, and with the kind of bonhomie that time was around between Indian PM and POTUS, that must have looked a better deal. Thus Dassualts deal was dropped.

I have AM Rajkumar's book and wrote what he wrote here. Our folks realised that the analog thing was a duck, that the French were working on the digital one for Rafale and we asked for that. The French showed us the Birdie, and US was willing to give it from the F16 and we went to the US.

The F16 FCS is 3 channel digital , with one channel analog. I don't know about Rafale's and Eurofighter if all the 4 are digital. But the LCA's became an all digital only because of the sanctions. If not, as originally planned it would have had 3 digital and an analog backup channels.

Checked through Dassualts' own doc also, but can't find link now. Here another source.
https://www.flightglobal.com/news/artic ... s--198907/

Dassault's FBW experience dates back to the original Mirage 2000, although in 1963 the company installed a prototype system on a vertical take-off version of the Mirage III, the Balzac, which transitioned to horizontal flight using FBW control of its engine nozzle. The Mirage 2000 is fully FBW-controlled, but uses four analogue computers, while the new Rafale has three digital computers and an analogue back-up

I guess the dual channel Analogue of Rafale is a backup system with limited authority (what Dassualt call as "Ultimate failsafe" or something like that) just line in M2K.

EF2000 is full authority Quad Channel Digital FBW system. This is same as LCA.


As a side note - saw this LCH avionics architecture scheme -

[vina]

I was crystal clear and clearly mentioned that HAL MC replaces old Dassault Type 2084 computer while Dassault MDPU replaced the old Sextant Avionique Type 90 air data computer.

Ok. You showed air data computer and mission computers being being replaced . Ok. But how does that affect the FCS in any way ?

Where are the core FCS /Control laws that have been implemented in analog, ported into digital in the upgrade (like it happened for F16 A/B to C/D)?

By your logic that implementing Dassault CLAW in Tejas would've been time consuming, then implementing Tejas CLAW in Lockheed Martin F-16 for testing would've been equally time consuming.

We were implementing a DIGITAL FCS (aka computer code) on an equivalent computer (running code on a simulator) . We were not doing analog programming (hardwiring transistors and doing circuit design) , which is an order of magnitude more difficult exercise.

Jaguar and Mirage 2000 had plug and play of avionics, systems and weapons and dropping US & Israeli bombs at Kargil much before Tejas flew unlike your statement below

Yes. And the F16 had it since 1974. So what is your point ? That the F16 , Jaguar and Mirage 2000s are "swing role" / "omnirole" / whatever and could swing between A2A and A2G in the same mission seamlessly even in 1974 , like the Gripen and Eurofighter and Rafale and F18 and F16 are able to do today ?

What is amazing is the huge spin off that the LCA program has given in terms of avionics. I can see that the M2K has been upgraded with the mission computer and the Mil Std 1553 bus, all developed for the TEJAS program and this has fed back into multiple programs (Mig 27, Jag, and now even the hallowed M2K!).

Again, trolling with "wrong emphasis" , so let me emphasise the "operative part"
Surely, you don't claim that the mission computer and other avionics stuff that got put into Mig 27 upg, Mig 29 Upg,M2K and the Jag Darin III are not the DARE developed ones for the LCA, but rather what goes in today is what went into Darin I ?
Come on. The computer you are typing this on has in all probability a PCI bus, which is probably 25 year old std and the ethernet and other networking standards the internet and LANS run on today goes back to mid 70s .TCP/IP goes back even further. Sure the bus standard is old,the protocols are the same, but things did get developed for the LCA and that got rolled into other programs!

[Karan M]

What is all this taliban stuff in what should be a straightforward discussion.

Vina, yest. Looks like sarkar sirji is confused about digital vs analog FBW and mixing it with the mission avionics. The HAL MC is there so IAF can add stores profiles and additional mission, ballistics and other computational data directly by itaelf and clear implication is access to MDPU is limited, what talk of FBW transfer. If we had full access to MDPU, we wouldnt have needed the HAL OSAMC. And yes, vina there is a LCA connection in that DARE did a similar approach with the Su30 MKI and the DARE MC also sat along with the Russian MCs on the Su30 and it was derived from the then LCA MC. And this talk of Dassault transferring TOT for FBW doesnt fly, net links apart, SR Valluri then LCA head went on record stating Dassault was not forthcoming with proper details to the Indian team and hence its proposal was not choaen. We would gave to dwvelop the entire FBW from scratch and instead of software mods, each iteration wod literally be custom designed hardware. Huge issues for long term use since we being first time makers would definitely need to constantly upgrade our FBW as we have been doing.

[sudeepj]

Regarding the AoA and speed, what is the corner speed of the Tejas? Any idea?

Let's wait for ADA to publish it. It's very good.

By the way, that 300 km combat radius is just a guesstimate. They haven't done any dedicated test flights to find out the range with different configs. Unfortunately, we many here don't want to discuss numbers because it questions their fanboyism and brochuritis. But these are the fuel fractions:
LCA: 27%
Gripen C/D: 25%
F-16 C: 25%

SFCs of all the engines are similar. So, I am still waiting for the fanboys to teach me how LCA is significantly short legged than these aircraft?

While fuel fraction is the same, how about drag? The LCA has a much bigger wing.. Doesnt that translate into much greater drag? (And much better maneuverability).

[Gyan]

Regarding the AoA and speed, what is the corner speed of the Tejas? Any idea?

Let's wait for ADA to publish it. It's very good.

By the way, that 300 km combat radius is just a guesstimate. They haven't done any dedicated test flights to find out the range with different configs. Unfortunately, we many here don't want to discuss numbers because it questions their fanboyism and brochuritis. But these are the fuel fractions:
LCA: 27%
Gripen C/D: 25%
F-16 C: 25%

SFCs of all the engines are similar. So, I am still waiting for the fanboys to teach me how LCA is significantly short legged than these aircraft?

How are calculating the percentage. I thought LCA was 2500/6500 = 38%

[Marten]

Gyan ji, 6500 would be empty weight. You might want to see it as 2500/(6500+2500).

sudeepj, would it be possible for you to provide a calculation using whatever inputs you wish to share/extrapolate? For instance, the claimed range on internal fuel load (i.e. not ferry range - excluding external tanks) for both?

Dr Vivek Ahuja has already shared his analysis based on the 404 IN20 for reference and there is a belief in some quarters that these parameters of range/on-station time might be better than thought. We'd do better than being rude and asking Indranil to do the math for our doubts. What say?

[Indranil]

Let's wait for ADA to publish it. It's very good.

By the way, that 300 km combat radius is just a guesstimate. They haven't done any dedicated test flights to find out the range with different configs. Unfortunately, we many here don't want to discuss numbers because it questions their fanboyism and brochuritis. But these are the fuel fractions:
LCA: 27%
Gripen C/D: 25%
F-16 C: 25%

SFCs of all the engines are similar. So, I am still waiting for the fanboys to teach me how LCA is significantly short legged than these aircraft?

While fuel fraction is the same, how about drag? The LCA has a much bigger wing.. Doesnt that translate into much greater drag? (And much better maneuverability).

I saw this reasoning of yours on the other thread. This is not factual. Afterall, passenger planes and gliders have huge wings. They seem to cruise very well and are not as maneuverable as fighters with small wings. What do you hear when people talk about changing a civilian plane into a UAV, e.g. Avanti to Hammerhead, Hansa to ___, HTT-40 to ____. The winglets that you see in virtually every aircraft these days is nothing but a weight saving feature to have the same efficiency of a longer wing using a shorter one. Size is only one criterion of the wing, shape is another and so is the cruise speed. I will let you find out how these parameters affect the drag on your own. If you are finding any difficulties, let me know and we can learn together.

LCA with it's low wing loading will take-off, climb and accelerate to cruise speeds with higher fuel efficiency. I don't know the L/D at cruise speeds of either of these planes. But, I will bet you this much. In terms of operational combat radius, LCA and F-16s will be within 10% of each other, if not lower.

[SaiK]

^^^^^ RE: GTF discussion.

would not that be unsuitable for a flat rated low bypass turbofan?

[Cain Marko]

Saars, whenever I've seen tejas fuel fraction bring compared with counterparts like gripen and solah, the pat reply is the same....What about drag? Esp. From the Swedes. As though gripen is Ferrari and lca is a bus. Imvhnonengineero. ..once we get the mk1a going, it'll rip past every single engined fighter around, esp. fast and high, and if it can get those levcons going, in slower regimes too. The wing loading on the bird is exceptional and with a little extra thrust via weightloss, it'll be very sharp and nimble.

The sweep on a cranked delta wing like lca is a lot higher than say a solah or fulcrum and definitely, super hornet, so my layman assumption is that it will be less draggy in high subsonic and faster regimes than solah. The other birds though all have lifting body design so might have more lift at lower speed. The gripen will alleviate this issue with canards, and the lca with cranked wing design and if needed, levcons.

[Indranil]

I forgot one last thing. The contribution of Mao sir to the LCA Navy program is much much much more than a pilot from NFTC. He kind of runs that show. Very ably as well, if I may add. India will be indebted to him.

Infranil who is the bearer of the flag from the IAF side now?

You mean within NFTC? Ranga sir is obviously leading the first squadron. One IAF man who did a lot for Tejas and whom people within ADA remember very fondly was Air Commodore Rohit Varma. He was a practical man who fought for Tejas in its most tumultuous times. Unfortunately, IAF denied him promotion twice and he finally called it quits in 2011. It was a big loss. Grp. Capt. Sunnet Krishnan then became the face of IAF. I don't know who it is now, but I can find out.

BTW your posts are a pleasure to read..you have your ears close to the ground in CV Raman Nagar.

Thank you.

Another nugget that might cheer up some people. The inadequate pressure recovery that the late Air Cmde Parvez Khokhar alleged was only an issue in the PV1.

[JayS]

^^^^^ RE: GTF discussion.

would not that be unsuitable for a flat rated low bypass turbofan?

Don't need GTF for low bypass. Whole point of GTF is to increase bypass ratio beyond 10. Currently max is 12 with PW1000G. But GTF has organic capability to go beyond 15. After that Open Rotor will take over.

[nachiket]

Saars, whenever I've seen tejas fuel fraction bring compared with counterparts like gripen and solah, the pat reply is the same....What about drag? Esp. From the Swedes. As though gripen is Ferrari and lca is a bus. Imvhnonengineero. ..once we get the mk1a going, it'll rip past every single engined fighter around, esp. fast and high, and if it can get those levcons going, in slower regimes too.

How will Mk1A address reduction in drag? That was planned in Mk2, by improving the area-ruling. Not that I think the drag issue in Mk1 is so serious that it has much lower range than the Gripen C/D despite better fuel fraction and same engine. That is just a case of Brochure values vs conservative estimates by ADA.

[Gyan]

Gyan ji, 6500 would be empty weight. You might want to see it as 2500/(6500+2500).

sudeepj, would it be possible for you to provide a calculation using whatever inputs you wish to share/extrapolate? For instance, the claimed range on internal fuel load (i.e. not ferry range - excluding external tanks) for both?

Dr Vivek Ahuja has already shared his analysis based on the 404 IN20 for reference and there is a belief in some quarters that these parameters of range/on-station time might be better than thought. We'd do better than being rude and asking Indranil to do the math for our doubts. What say?

Then F-16 would also be 2500/(9500+2500)=20%

[Indranil]

How will Mk1A address reduction in drag?

Will only have lower induced drag. HAL "aerodynamics" guys are also claiming that they can reduce spillage drag.

That was planned in Mk2, by improving the area-ruling. Not that I think the drag issue in Mk1 is so serious that it has much lower range than the Gripen C/D despite better fuel fraction and same engine. That is just a case of Brochure values vs conservative estimates by ADA.

It is the latter. Wave drag is not the major player at cruise speeds. ADA guys don't have a marketing team.

[ramana]

So Indranil the drag business in non issue for the speeds at which the LCA operates?

[Cain Marko]

Natchiket, my mango abdul konawala maikaneek understanding is that weight reduction will help compensate and result in increased pwr and better flight performance plus increased range for the mk1a.

[ramana]

CM , Weight -ve -> Power/unit weight +ve
Therefore flight performance +ve and range +ve for same aerodynamic coefficients.

[JayS]

My estimation of LCA Cd value is 0.0200. Which places it right in the ballpark of the best lot. YF16 had something like ~0.0225 so F16 should be around 0.02 considering some optimization. But this is more like design value. Its quite difficult to guage Cd values for various points in the envelop, but as IR said, it cannot be say more than 10-15% worse than Gripen.

Big wing does not automatically mean more drag. It could very well be that since bigger wing produces more lift, it would need to maintain lower AoA than a small wing aircraft for same amount of lift - thus overall drag could be same or even lesser for larger wing than that of a smaller wing.

[nachiket]

How will Mk1A address reduction in drag?

Will only have lower induced drag. HAL "aerodynamics" guys are also claiming that they can reduce spillage drag.

How will induced drag reduce? The only major change is weight reduction. From my layman understanding that has no effect on induced drag. Or does it?

That was planned in Mk2, by improving the area-ruling. Not that I think the drag issue in Mk1 is so serious that it has much lower range than the Gripen C/D despite better fuel fraction and same engine. That is just a case of Brochure values vs conservative estimates by ADA.

It is the latter. Wave drag is not the major player at cruise speeds. ADA guys don't have a marketing team.

Wonder how much that has hurt the LCA over the years.

[JayS]

LCA with it's low wing loading will take-off, climb and accelerate to cruise speeds with higher fuel efficiency. I don't know the L/D at cruise speeds of either of these planes. But, I will bet you this much. In terms of operational combat radius, LCA and F-16s will be within 10% of each other, if not lower.

L/D_max for LCA = ~9 for cruise conditions at M=0.7