LCA: News & Discussions - October 2016

[Indranil]

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%

2500/9500

[nachiket]

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

F-16 is 3200/(8570+3200) = 27.18%

[Kartik]

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.

FTS can be built before flight testing is complete. I've seen the 787 FTS specimen in testing while the flight testing was still ongoing. For the Tejas, they could have gone with any of the later SOPs (Standard of Preparation) for the durability and damage tolerance testing. I doubt any of the primary or major structures have changed from the LSPs to SPs.

Anyway, the waiver was only for the prototypes. Series Production variants will be ~5-6000 hours at least, considering the amount of composites and the reduction in the number of rivets and parts, plus the airframe being limited to 8Gs. Fewer holes drilled, fewer stress risers, less likelihood of fatigue related cracks developing over time.

[nachiket]

BTW, where do I find the actual internal fuel capacity of the Gripen C/D? Saab's website just says >2000kg with no exact value. Wiki doesn't say anything, but mentions combat radius as 800km

Of all the aircraft manufacturers I have a feeling Saab lies about and fudges these values the most.

[Kartik]

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.

FTS can be built before flight testing is complete. I've seen the 787 FTS specimen in testing while the flight testing was still ongoing. For the Tejas, they could have gone with any of the later SOPs (Standard of Preparation) for the durability and damage tolerance testing. I doubt any of the primary or major structures have changed from the LSPs to SPs. Actually, they can pull any of the LSPs that are not used for flight testing anymore and use it as the FTS too. They know how many flight cycles it has already completed. Load spectrum will be based on the typical usage in service- so with that they could scale up or scale down the number of flight cycles the LSP has already undertaken, depending on how most of those flights corresponded to typical in service sortie usage.

Anyway, the waiver was only for the prototypes. Series Production variants will be ~5-6000 hours at least, considering the amount of composites and the reduction in the number of rivets and parts, plus the airframe being limited to 8Gs. Fewer holes drilled, fewer stress risers, less likelihood of fatigue related cracks developing over time.

[Kartik]

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

Just one data point- even in the day of digital FCS, Saab didn't want to again touch that FCS for the most part. Hence, the partitioning of the Flight Control system from the Mission Data Processing, which they trumpet as Modular Avionics Architecture.

Regarding the Gripen E

Although not visible, arguably the biggest change comes under the skin, in the shape of an innovative integrated modular avionics architecture. Of the millions of lines of code in the aircraft’s 40 computers, only around 10 percent are flight-critical, and these functions have been separated from those for mission purposes. This allows updates and changes for operational purposes to be done at lower cost and with time savings. Not only does this provide for the quick insertion of new technology to meet emerging threats and tactical requirements, but it also allows customers to adapt the aircraft to their needs

Lower cost- since it involves less regression testing to check that the flight critical functions are not in anyway changed.

What is clear from the picture that was posted is that the Mirage-2000's FCS has been untouched and the new Mission Computer basically handles the avionics upgrades only. the FCS that is analog, will remain analog. No more money is ever going to be spent on the Mirage-2000 for that purpose. They'd have otherwise needed a lot of work to re-develop the software for it and do the flight testing to validate it all over again. Safety critical, so there would no other way around that.

[Indranil]

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?

If the weight is decreased, the lift required to balance it decreases by the same amount. Lift induced drag will decrease proportionally. This is roughly true. Every change in flight has secondary effects. For example, you will be flying at lower AoA which changes other aspects of drag. There may be secondary effects on the trim drag and so on. But in general, as hakim's friend put it: "weight is lift, lift is (induced)drag".

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

I know the paper from where this is derived. But neither the LCA, nor the F-16 will be flying clean. That's why I did not want to use these numbers. As you have said before, the people designing these aircraft, be it the LCA, F-16, or Gripen are at the top of their game. When internet-smart-pants come across and question only one set of these professionals, it really rubs me the wrong way. I feel like showing them how much water they are standing in using my limited capability. By the way, I was recently reading a study on the X-29A and there they compare X-29A drag features with respect to F-15, F-16 and F-18. You might like it.

Series Production variants will be ~5-6000 hours at least, considering the amount of composites and the reduction in the number of rivets and parts, plus the airframe being limited to 8Gs. Fewer holes drilled, fewer stress risers, less likelihood of fatigue related cracks developing over time.

They are talking of cocuring the bottom skin of the wing along with all the structural elements of the wing into one piece. But, here I am arguing with people about how it compares favourably against other 4th gen planes !

BTW, where do I find the actual internal fuel capacity of the Gripen C/D? Saab's website just says >2000kg with no exact value. Wiki doesn't say anything, but mentions combat radius as 800km

Of all the aircraft manufacturers I have a feeling Saab lies about and fudges these values the most.

Their marketing team keeps portraying the Gripen as a light plane which can punch above its weight, i.e. in the domain of the other medium-weight Eurocanards. I don't fault them. They are doing their job well. It is really up to the users to verify them. Unfortunately, the CM of Maharashtra is easy to fool.

[nachiket]

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?

If the weight is decreased, the lift required to balance it decreases by the same amount. Lift induced drag will decrease proportionally. This is roughly true. Every change in flight has secondary effects. For example, you will be flying at lower AoA which changes other aspects of drag. There may be secondary effects on the trim drag and so on. But in general, as hakim's friend put it: "weight is lift, lift is (induced)drag".

Ah, got you. The opposite effect will apply in the case of CFTs on the F-16 then. Not to mention all the fancy new avionics that will make it even heavier.

BTW, where do I find the actual internal fuel capacity of the Gripen C/D? Saab's website just says >2000kg with no exact value. Wiki doesn't say anything, but mentions combat radius as 800km

Of all the aircraft manufacturers I have a feeling Saab lies about and fudges these values the most.

Their marketing team keeps portraying the Gripen as a light plane which can punch above its weight, i.e. in the domain of the other medium-weight Eurocanards. I don't fault them. They are doing their job well. It is really up to the users to verify them. Unfortunately, the CM of Maharashtra is easy to fool.

Not to mention some BRF posters going gaga over the Gripen and deriding the LCA for being short ranged.

[Kartik]

BTW, where do I find the actual internal fuel capacity of the Gripen C/D? Saab's website just says >2000kg with no exact value. Wiki doesn't say anything, but mentions combat radius as 800km

Of all the aircraft manufacturers I have a feeling Saab lies about and fudges these values the most.

2,400 kg internal fuel- source, FlightGlobal.

[nachiket]

BTW, where do I find the actual internal fuel capacity of the Gripen C/D? Saab's website just says >2000kg with no exact value. Wiki doesn't say anything, but mentions combat radius as 800km

Of all the aircraft manufacturers I have a feeling Saab lies about and fudges these values the most.

2,400 kg internal fuel- source, FlightGlobal.

Thanks. Although I wonder where they got the figure from, since Saab itself does not specify it.

[Kartik]

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.

Careful about the words you use- "from the F-16" will be taken to imply that it was lifted from the F-16 and ported onto the LCA. And that will then be taken to imply that it was quite a simple task really. And that is, as you know, since you have AM Rajkumar's book, very very far from the truth.

[Kartik]

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.

Why was it only a PV1 issue? Manufacturing issue or was the inlet design changed post PV1 to overcome it?

[Kartik]

2,400 kg internal fuel- source, FlightGlobal.

Thanks. Although I wonder where they got the figure from, since Saab itself does not specify it.

From a flight test of the Gripen. But this is a straightforward number, not too difficult to find. Saab are masters of PR and attempt subtle deceptions with the things they put out, regularly. Such as the payload or range capabilities that they put out, without mentioning most other parameters.

For instance, even an experienced writer like Craig Hoyle wrote something that was absurd. Wonder how he wrote this, when the current Gripen E's empty weight with the F414 engine (which weighs in at ~1100 kgs), is 8000 kgs! So that tells us the 'airframe' (without the engine) weight is ~6600 kgs and not 3000 kgs. Even given that the original target was ~7200 kgs empty weight, he was way off. Obviously, if one looks deeper into this, Saab will cleverly point out that this is the so-called 'airframe weight', which doesn't include engine and probably not even the landing gear. But to the one's who are not carefully reading this, they'll be like..empty weight is only 3000 kgs?! WOW!!!

Saab reveals full Gripen E design and cost savings

The Gripen’s air intake design has also been enlarged, and new landing gear installed. The latter includes a larger, single nose wheel and main gear which retracts into the wing, freeing fuselage space and enabling a 40% increase in internal fuel capacity. Two additional weapon stations have also been introduced beneath the fuselage.

Maximum take-off weight will be 16.5t, with the type’s empty airframe weight accounting for just 20% of this, at around 3t.

[Marten]

Kartik, you're giving them 10 additional minutes of station time.

Saab does claim E is 3400kg AND also claims the 40% increase from the previous version.
Ergo, internal fuel load for C is 2240kg. I saw 2286 in some other brochure.

[Indranil]

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.

Why was it only a PV1 issue? Manufacturing issue or was the inlet design changed post PV1 to overcome it?

Until PV1, the air intakes were optimized for the Kaveri. PV2 onwards, the intakes are optimized for the 404.

[Indranil]

Kartik, you're giving them 10 additional minutes of station time.

Saab does claim E is 3400kg AND also claims the 40% increase from the previous version.
Ergo, internal fuel load for C is 2240kg. I saw 2286 in some other brochure.

And an empty weight of 8 Tons. So if the internal fuel of 3400 kg is right, then the clean take off weight must be around 12000 kgs. That gives a fuel fraction of about 28% which is respectable.

[putnanja]

Why was it only a PV1 issue? Manufacturing issue or was the inlet design changed post PV1 to overcome it?

Until PV1, the air intakes were optimized for the Kaveri. PV2 onwards, the intakes are optimized for the 404.

Hmm, I remember reading earlier somewhere that even after the additional spring loaded air-intakes that open during take-off times, the inlet was not fully optimized for the airflow required for the engine.

[Indranil]

All intakes are optimized for a design point. At off-design-points the mouth is too small or too big. When it is too small, the engines is starved. And when the it is too big, not all the air that can possibly enter the intake can be used by the engine. This "extra air" is "spilled out" causing a form of drag called spill drag. If the intake is designed to work optimally at zero or very low forward speeds, it will look like that of the Harrier.Otherwise, it will look like what you see on LCA (or any other fighter). Blow in doors are very common design features on such intakes. You can see them of Mirages, Rafales etc. If LCA's engines were really that badly starved at low speeds, you would not have seen these phenomenal take off and landing performance that has been reported.

[JayS]

I know the paper from where this is derived. But neither the LCA, nor the F-16 will be flying clean. That's why I did not want to use these numbers. As you have said before, the people designing these aircraft, be it the LCA, F-16, or Gripen are at the top of their game. When internet-smart-pants come across and question only one set of these professionals, it really rubs me the wrong way. I feel like showing them how much water they are standing in using my limited capability. By the way, I was recently reading a study on the X-29A and there they compare X-29A drag features with respect to F-15, F-16 and F-18. You might like it.

Still the L/D at cruise for two planes give a good benchmark for comparison since the changes in L/D at off-design points will be very similar for both the planes. Physics doesn't change and the variations are marginal. Any competent team in the world working on a fighter will land up in the same range of aerodynamic efficiency if they target to be competitive. Of coarse you know this, but its for others to note.

As kartik said, swedes are masters of deception when it comes to marketing. They claim RM12 to be their own engine, when they have redesigned (not even designed from scratch) exactly 2 modules, co-developed one module with extensive GE help and manufacture less than 10% of the engine on their own. So anything SAAB says, take it with pinch of salt. LCA will be at par with Gripen if not better.

[JayS]

Obviously, if one looks deeper into this, Saab will cleverly point out that this is the so-called 'airframe weight', which doesn't include engine and probably not even the landing gear. But to the one's who are not carefully reading this, they'll be like..empty weight is only 3000 kgs?! WOW!!!

3t is probably weight of bare airframe without any LRU, engine, whatsoever in it. Very clever of them. By this matrix LCA will be 2.5T perhaps.

[JayS]

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.

FTS can be built before flight testing is complete. I've seen the 787 FTS specimen in testing while the flight testing was still ongoing. For the Tejas, they could have gone with any of the later SOPs (Standard of Preparation) for the durability and damage tolerance testing. I doubt any of the primary or major structures have changed from the LSPs to SPs.

Anyway, the waiver was only for the prototypes. Series Production variants will be ~5-6000 hours at least, considering the amount of composites and the reduction in the number of rivets and parts, plus the airframe being limited to 8Gs. Fewer holes drilled, fewer stress risers, less likelihood of fatigue related cracks developing over time.

Thing is for FTS, the specimen has to be as close to the Production SOP as possible (with changes to be recertified somehow later), ideally identical. From CAG report, the LSP itself was finalised in late 2012 and LSP could not achieve the level of commonality with SP that was expected. Even if its logical to assume there would be minimum changes from LSP to SP in the structure, we are not sure if there were any changes expected in any critical areas of the structure or not. As such if HAL had taken decision not to make a FTS, I am sure others were in the loop since there have been regular meetings happening for LCA committee. CAG does not report any protestation from ADA/IAF against HAL's reply. They might have expected some changes post LSP-8 and so kept it pending. Or could have postponed it since its not very critical thing, there were other priorities. This is a gray area. As such its a regular practice to accept parts with life limit in initial development phase if the parts do not meet the requirement or its life cannot be certified to the satisfaction of certifying authority.

Anyway, from chaiwalla news, it looks like the FTS is completed and LCA is fully certified for its design life. But confirmation is awaited.

[JayS]

They are talking of cocuring the bottom skin of the wing along with all the structural elements of the wing into one piece. But, here I am arguing with people about how it compares favourably against other 4th gen planes !

For MK2..?? I had asked the head of the LCA production facility this question of possibility of co-bonded, co-cured structure, he said it will not be coming in LCA.

[Indranil]

Your information is correct. It was discussed as it is well within NAL's reach, but was not prioritized, aka funded.

By the way, when the "order" for 83 LCA was placed, ADA was asked to work on MK2 seriously. Before that, there was significant dilly-dallying.

[Zynda]

^^Where are u getting all these info saar? From ur little birdies who nest around ADA?

[Pratyush]

The mk2 news if correct is a wonderful news. As it shows that the future is a lot more than 120 odd units.

[JayS]

Your information is correct. It was discussed as it is well within NAL's reach, but was not prioritized, aka funded.

By the way, when the "order" for 83 LCA was placed, ADA was asked to work on MK2 seriously. Before that, there was significant dilly-dallying.

Hope they also give adequate funding to expand ADA to accommodate all the additional work with MK1A/MK2/AMCA. After a long time I saw some freshie recruitment in ADA for small number (and in DRDO).

[SaiK]

Not LCA , but read this where LCA and AMCA might focus in the future.

http://aviationweek.com/defense/how-gro ... fbb849082b

[Kartik]

Obviously, if one looks deeper into this, Saab will cleverly point out that this is the so-called 'airframe weight', which doesn't include engine and probably not even the landing gear. But to the one's who are not carefully reading this, they'll be like..empty weight is only 3000 kgs?! WOW!!!

3t is probably weight of bare airframe without any LRU, engine, whatsoever in it. Very clever of them. By this matrix LCA will be 2.5T perhaps.

yes, but it's all about semantics..clever usage of terms, which give an impression to the average reader that it meant that the airplane's empty weight itself is just 3 tons. But it is a meaningless figure since it gives no idea about the actual airplane's empty weight. As for the LCA, I doubt it is any lighter than the Gripen. Their overall empty weight figures are very similar, except for the ballast that the LCA carries. Haven't read anywhere about ballast on the Gripen.

Anyway, as we now know, the actual Empty Weight is 8 tons. And that the MTOW is 16.5 tons and that means that Empty Weight grew by 1.5 tons over the Gripen C/D whereas MTOW increased by 2.5 tons over the Gripen C/D. So an overall gain in fuel/payload of ~1000 kgs (i.e if they've not been clever by not including the weight of the new wingtip jammer and the IRST).

[narmad]

^^Where are u getting all these info saar? From ur little birdies who nest around ADA?

aam khao sir, gutliyon ki chinta mat karo [ enjoy the mango, don't worry where the seed came from ]

[Kartik]

Their marketing team keeps portraying the Gripen as a light plane which can punch above its weight, i.e. in the domain of the other medium-weight Eurocanards. I don't fault them. They are doing their job well. It is really up to the users to verify them. Unfortunately, the CM of Maharashtra is easy to fool.

Not to mention some BRF posters going gaga over the Gripen and deriding the LCA for being short ranged.

The fault lies with our own people. You cannot blame Saab's PR and marketing team for doing its job- which is to market its jet. Our guys are tasked with some other things and the PR aspect has been missed out for most of the LCA's history. They didn't counter the bad press that was being generated with issues that were being reported- mostly half baked info, without much idea of the full picture. They haven't provided much PR material and they only just went to this Bahrain Air Show.

So, when some data is provided to the govt. to answer some parliamentarian's question gives some data on range capabilities, it is the only definitive source of the combat radius of the Tejas. But we don't know what parameters have been used to arrive at that- what configuration, what profile, nothing. Saab's marketing team will sit and and look at creative ways to show this range- by just about leaving out the important info that would help the viewer understand what those incredible range figures really mean. Of course they won't be able to fool any air force that actually evaluates the type, but it does create a certain aura about the jet's capabilities.

[Kartik]

If LCA's engines were really that badly starved at low speeds, you would not have seen these phenomenal take off and landing performance that has been reported.

Speaking of landing performance, delta wing fighters are generally known to have strong 'ground effect' when coming in to land and just about 1 wingspan above the runway; which allows for the pilot to be able to land the jet quite gently, when compared to non-delta wing fighters. Tejas with its huge delta wing will definitely see a strong ground effect, good for the Air Force variant, but more of an issue with the Naval LCA where the fighter should not float over the runway for any distance but rather should be plonked onto the carrier.

[Indranil]

Anyway, as we now know, the actual Empty Weight is 8 tons. And that the MTOW is 16.5 tons and that means that Empty Weight grew by 1.5 tons over the Gripen C/D whereas MTOW increased by 2.5 tons over the Gripen C/D. So an overall gain in fuel/payload of ~1000 kgs (i.e if they've not been clever by not including the weight of the new wingtip jammer and the IRST).

Effectively, we have a plane coming in the 2020s, whose empty weight is ~10% less than an F-16 block 30, but powered by an engine which has ~30% less power.

Meanwhile, the placement of the jammer on the LCA Mk1/Mk1A is very interesting. Apparently, the most likely position are dual pylons on the outboard wing pylons. Surprisingly, the station has enough strength to carry it. The question is the added roll-inertia of the plane. I was wondering if they can be placed within the pylons to avoid any form drag. However, placing it on the centerline pylon is not ideal for the working of the jammer. Another possible position is the top of the fin. Let's see what happens. But, my money is on a modified dual pylon on the outboard pylon.

[Indranil]

Speaking of landing performance, delta wing fighters are generally known to have strong 'ground effect' when coming in to land and just about 1 wingspan above the runway; which allows for the pilot to be able to land the jet quite gently, when compared to non-delta wing fighters. Tejas with its huge delta wing will definitely see a strong ground effect, good for the Air Force variant, but more of an issue with the Naval LCA where the fighter should not float over the runway for any distance but rather should be plonked onto the carrier.

Remember, the discussion that Jay and I were having about the upturned Levcon. It is related to this. They are trying to kill the lift of the wing.

[Kartik]

Any competent team in the world working on a fighter will land up in the same range of aerodynamic efficiency if they target to be competitive. Of coarse you know this, but its for others to note.

Which is exactly how I used to argue with internet trolls who would talk about the LCA having a lot of drag versus Gripen or even JF-17 (lol!); but there can be differences in the aerodynamic efficiency, depending on how experienced the design teams are. For me, what made me realise this was when I read the ADA paper on drag reduction exercises for the LCA. The issue of the area ruling not being good in the region just aft of the cockpit, leading to a drag increase did come up in an ADA paper, and the possible solution of a fuselage plug being added..this was very very late in the design phase and should have been caught in the first few iterations of the design itself. After all, good area ruling is a fundamental design goal.

We see that in the AMCA, there have been at least 8 iterations of the first design variant and each iteration has focused on a specific target, one of them being area ruling. Had that been done for the Tejas, we would have seen a longer LCA originally itself. But then, there has been a fetish of sorts to have the smallest possible jet..maybe it was the Gnat effect, because even the MiG-21Bis is 14.5m long, whereas the Tejas Mk1 is just 13.2m.

[Kartik]

Speaking of landing performance, delta wing fighters are generally known to have strong 'ground effect' when coming in to land and just about 1 wingspan above the runway; which allows for the pilot to be able to land the jet quite gently, when compared to non-delta wing fighters. Tejas with its huge delta wing will definitely see a strong ground effect, good for the Air Force variant, but more of an issue with the Naval LCA where the fighter should not float over the runway for any distance but rather should be plonked onto the carrier.

Remember, the discussion that Jay and I were having about the upturned Levcon. It is related to this. They are trying to kill the lift of the wing.

Oh, right right. Makes complete sense !

[Kartik]

Your information is correct. It was discussed as it is well within NAL's reach, but was not prioritized, aka funded.

By the way, when the "order" for 83 LCA was placed, ADA was asked to work on MK2 seriously. Before that, there was significant dilly-dallying.

Wait, wasn't it ADA that was pushing for the Mk2 and HAL which was resisting it, and asking for the Mk1A instead?

Is the Mk2 coming along then? If so, would be a wonderful piece of news! Then, we are very likely to see over 200 Tejas variants in IAF and IN service.

Success! (Borat style! )

[Kartik]

Anyway, as we now know, the actual Empty Weight is 8 tons. And that the MTOW is 16.5 tons and that means that Empty Weight grew by 1.5 tons over the Gripen C/D whereas MTOW increased by 2.5 tons over the Gripen C/D. So an overall gain in fuel/payload of ~1000 kgs (i.e if they've not been clever by not including the weight of the new wingtip jammer and the IRST).

Effectively, we have a plane coming in the 2020s, whose empty weight is ~10% less than an F-16 block 30, but powered by an engine which has ~30% less power.

Meanwhile, the placement of the jammer on the LCA Mk1/Mk1A is very interesting. Apparently, the most likely position are dual pylons on the outboard wing pylons. Surprisingly, the station has enough strength to carry it. The question is the added roll-inertia of the plane. I was wondering if they can be placed within the pylons to avoid any form drag. However, placing it on the centerline pylon is not ideal for the working of the jammer. Another possible position is the top of the fin. Let's see what happens. But, my money is on a modified dual pylon on the outboard pylon.

Ah, very interesting..so a dual pylon, but on both sides or just one? Having a pair instead of just one may work out in that each jammer would be lighter and could be accomodated on the outboard hardpoints along with a Python 5. And you'd get better coverage all around the airplane, with no masking by the airframe for one side.

I wonder if it is meant to be an optional piece of kit, added on when required and removed during other missions or as standard equipment itself, so that all Mk1A outboard pylons will be dual pylons.

Any idea if they're working on a dual mid-board pylon as well to be able to carry 2 Derby/Astra BVR missiles on a single mid-board hardpoint?

[Indranil]

Wait, wasn't it ADA that was pushing for the Mk2 and HAL which was resisting it, and asking for the Mk1A instead?

Is the Mk2 coming along then? If so, would be a wonderful piece of news! Then, we are very likely to see over 200 Tejas variants in IAF and IN service.

Success! (Borat style! )

Yes, HAL is going to focus on Mk1A. ADA on Mk2. I hope HAL does not go into a full design cycle with the Mk1A. AESA, jammer and rearrangement of LRUs for better maintenance is plenty good.

Ah, very interesting..so a dual pylon, but on both sides or just one?

Having a pair instead of just one may work out in that each jammer would be lighter and could be accomodated on the outboard hardpoints along with a Python 5. And you'd get better coverage all around the airplane, with no masking by the airframe for one side.

I don't know. But I would expect it to be on both sides.

Any idea if they're working on a dual mid-board pylon as well to be able to carry 2 Derby/Astra BVR missiles on a single mid-board hardpoint?

I have asked this many times. It looks like a low hanging fruit. But I have never got a definite answer. Certainly, it is not a priority. I think, they don't imagine a scenario where LCA will have to carry 4 BVRs + 2 WVRs.

[JayS]

Any competent team in the world working on a fighter will land up in the same range of aerodynamic efficiency if they target to be competitive. Of coarse you know this, but its for others to note.

Which is exactly how I used to argue with internet trolls who would talk about the LCA having a lot of drag versus Gripen or even JF-17 (lol!); but there can be differences in the aerodynamic efficiency, depending on how experienced the design teams are. For me, what made me realise this was when I read the ADA paper on drag reduction exercises for the LCA. The issue of the area ruling not being good in the region just aft of the cockpit, leading to a drag increase did come up in an ADA paper, and the possible solution of a fuselage plug being added..this was very very late in the design phase and should have been caught in the first few iterations of the design itself. After all, good area ruling is a fundamental design goal.

We see that in the AMCA, there have been at least 8 iterations of the first design variant and each iteration has focused on a specific target, one of them being area ruling. Had that been done for the Tejas, we would have seen a longer LCA originally itself. But then, there has been a fetish of sorts to have the smallest possible jet..maybe it was the Gnat effect, because even the MiG-21Bis is 14.5m long, whereas the Tejas Mk1 is just 13.2m.

A possible explanation is the maturity of computational codes that ADA had in 1980's and early 1990s when LCA's external shape was frozen. Remember all these codes were developed from scratch for LCA. Literally nothing existed before. They might not have seen the improvement in the drag with change in canopy shape for example. The effect is 6% reduction in drag in transonic regime and it is well within the error band of CFD codes. I have previously also surmised that LCA looks to have been optimized for supersonic speed apart from the transonic design point. While doing so they might have had done trade off within the limits of the accuracy of their tools. I have noticed progressive improvement in ADA/NAL codes over the years through their publications. Another factor to consider is the available computational power to do enough iterations. Similar case with the WT experiments. Tools are as much important as the designer. And it takes good long time to build OEM specific tools for any company/organisation.

[tsarkar]

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.

Ah, so you believe Mirage 2000 uses hardwired transistors. Refer below what the Mirage 2000 uses.

And regards to Mission Computer, HAL had partnered with Smiths Industries for the DARIN II Mission Computer, but when DARE MC came along, they used it. So Mission Computer as a concept was not first used in Tejas, it was planned for DARIN II around the same time.

What is clear from the picture that was posted is that the Mirage-2000's FCS has been untouched and the new Mission Computer basically handles the avionics upgrades only. the FCS that is analog, will remain analog. No more money is ever going to be spent on the Mirage-2000 for that purpose. They'd have otherwise needed a lot of work to re-develop the software for it and do the flight testing to validate it all over again. Safety critical, so there would no other way around that.

No, your inference is wrong. Did you see the MDPU (Modular Data Processing Unit) connecting to Sensor & Control? That will replace the Type 2084 flight control computer. See the picture again.



Refer here

https://web.archive.org/web/20071204095 ... ALE_EN.doc

Page 6

The core of the enhanced capabilities of the RAFALE lies in a new Modular Data Processing Unit (MDPU). It is composed of up to 18 flight line-replaceable modules, each with a processing power 50 times higher than that of the 2084 XRI type computer fitted on the early versions of Mirage 2000-5.

The initial versions of Mirage 2000 had 2084 digital computer. the Mirage 2000D had evolved 2084 XR digital computer and Mirage 2000-5 had further evolved 2084 XRI digital computer and Rafale has MDPU

BTW what makes you think that original Mirage 2000 FCS was analogue?

Even the original 2084 computer was digital, the channels were analogue.

Refer here https://www.flightglobal.com/FlightPDFA ... 201696.PDF

26 August 1978…Marcel Dassault Sagem 2084 digital computer and a back-up USG Type 284

Refer here https://www.flightglobal.com/FlightPDFA ... 204245.PDF

17 November 1979…The Mirage 2000 has an EMD Sagem 2084 Central Computer with USG Type 284 stand-by computer and the Digibus Data Highway communicating with all systems and processing virtually all the weapons and flight data...

...Air Data comes from a Crouzet Type 80 digital air data computer

And as this report from 5 October 1985 states, the Mirage 2000 with Digital Computer with Analogue Channels was superior to F-16’s all analogue system.

https://www.flightglobal.com/pdfarchive ... 02757.html

The first fighter designed deliberately to be unstable, and the first production aircraft to have full-time fly-by-wire, is
General Dynamics' F-16A, which first flew in 1976. Computing is analogue and redundancy is quadruplex. Dassault-
Breguet's Mirage 2000, which first flew in 1978, is also unstable and fly-by-wire. Computing is analogue, but with digital gain control and monitoring. Redundancy is quadruplex in the critical pitch (elevon) axis and triplex in the yaw axis. A fifth,
entirely independent battery-driven backup channel is provided, however.

And no disrespect intended to the Tejas program or efforts all around, but let me burst your bubble a bit more - there is not one performance capability in the Tejas that wasn’t there in the Mirage 2000 of 1985.

Let me know one feature or performance capability that Tejas does better than Mirage 2000.

Its because IAF senior officers and people like me have seen the Mirage in action, probably when you and Vina weren’t born, that we know of the Mirage’s capabilities, so don’t jump around like kids when a Tejas press release comes along. Been there, done that, in 1985.

And BS statements like below will need to be called out as BS

Let me also point out a few things more than Arup Raha Harrumphed about recently as "improvements "

Asked for provision of growth for AESA. Asked for higher fuel load and range, asked for airborne refuelling,asked for IR tracker, asked for internal SPJ (they had already done the Bison upgrade by then, they knew that an SPJ was needed), asked for higher thrust engine. IF they had done that at the start of FSED phase, the LCA that would have come out would have the mould line of the proposed MKII right from the beginning and NOT the current Mk1 version! There would have been a fuselage stretch for extra room for equipment and fuel, aero refinements to match that ask and you could have fielded a version with a normal radar like the MK1 but with an airframe that incorporated the stuff you wanted , you have got a right sized airframe and not come and Harrumph and try to derail the program at the last minute saying oh, I want an INTERNAL SPJ! Where the hell were you guys at FSED stage , when the plane is basically getting re-engineered?

What we have are "legacy" fighters that dont have the "control configured vehicle" features of the Tejas. The Jags and Mirages wont have them as wont the SU-30. They were simply not designed that way and our upgrades wont touch their FCS and critical flight controls that would remain a black box. You will have to push mechanical switches after they land to reconfigure them for the next mission.

http://www.icas.org/ICAS_ARCHIVE/ICAS19 ... -4.5.1.pdf

Page 1

1978 Fly by Wire and CCV for unstable aircraft (without mechanical back—up) - Mirage 2000 & Super Mirage 4000

There is a photo on BR of two Mirage 2000 flying at very high AoA in formation with a prop plane, attesting to the high degree of control of its obsolete analogue system flown by dinosaur IAF. I tried finding it, but couldn't - request someone having it to post.

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

You mean within NFTC?

There is a Tejas Program Office in IAF headed by an AVM.

Wait, wasn't it ADA that was pushing for the Mk2 and HAL which was resisting it, and asking for the Mk1A instead?

Actually it was HAL that saved the Tejas.

HAL wasnt resisting Mk2, HAL correctly estimated that the design of Mk2 would never be finalized by 2017 as initially promised by ADA, hence proposed the interim Mk1A.

ADA was forecasting 2017 for the fuselage plug & new engine but based on past experience 2025-26 was a more realistic timeframe. IN wanted an engine change to enable Mk2 carry a useful load from aircraft carriers.

A new design iteration promised 2017 delivered 2025 would've lost IAF & MoD interest.

The interim Mk1A, with most probably Elta jammer that HAL has experience fitting on MiG-21, Sea Harrier, Jaguar & Su-30 and Elta 2052 that would be fitted to DARIN 3 Jaguars filled a production gap from 2020-2025/6 when Mk2 design would be ready.

Now ADA too has sufficient time to work on Mk2.