Tejas Mk.2: News & Discussions - 25 February 2018

[Kartik]

Very curious to see final airframe of Mk2. IAF officers had suggested that design will incorporate stealth as takeaway from AMCA design, I hope we will see a far better carved out Mk2 than earlier. It should not be the case that only canards are added and we are calling it a drastic design change.

When did IAF officers suggest any stealth to be applied to the Outer Mould Line of the Tejas Mk2?

if at all, the stealth features will be RAM coatings and indium oxide for the canopy. Engine blockers not required since it is buried deep in the fuselage and fully shielded by the Y-shaped bifurcated duct. Maybe flush antennae as well, but that would be a stretch goal and cannot be a primary requirement. Since it will be carrying all its weapons externally, there is only so much that stealth shaping will even achieve.

And so, it will be the case that canards are added, aerodynamics are further refined to reduce drag, fuselage is lengthened and landing gear beefed up and its attachment points moved out towards the wing join area (like on the Gripen E/F). That is how this program's timelines can be met. Not by adding changes to the OML or bays or whatever which would completely derail the project's schedule.

And timelines are the most crucial part of the Tejas Mk2 program. A fully +9G capable fighter with more fuel and payload capability plus OBOGS and air to air refueling will mean that the Tejas Mk2 will go into the Gripen E/F, Mirage-2000I class in terms of range, payload and endurance.

[Indranil]

Kartik. You have got it. In my wishes, I wish ADA considered the EPE, but that would risk the program again.

[Kartik]

Yes, IR, while desirable, it is not feasible in terms of the timelines. Engine integration is no small task and with F-414 EPE itself not ready fully, the engine's development timeline would have to be factored in as well. And so you would then have an interim engine (as the F-404 F2J3 was for the Mk1) and then moving on to the EPE. But the gains would be ~15 kNs in extra thrust versus potential schedule delays.

If I was the IAF customer helping ADA/HAL make the choices, I would be firm on the F-414-INS6 as well. To me, that is the most critical aspect- getting it into service as soon as possible.

With the Jaguar re-engining dying, we may see the oldest Jags starting to retire even earlier as their engines come to the end of their service lives..previously, the new Jags that would have gotten the F-125IN could've been cannibalised and their newer engines put on the older Jags that were not going in for the DARIN-3 upgrade or the engine replacement. Now, it seems that their end is nearing.

[Kartik]

Time to take a good look at the GE-F-100 as well, instead of just sticking with the F-414 class of thrust. That would be more than sufficient for growth in the coming decades. Will give it the scope for extended range conformal tanks and heavy cruise missiles among other options, right from the outset.

Nope, too big. And just adding more thrust won't work. Everything has been sized to fit the F-414 to which we have had access for some years now. If the engine changes, that's it, you have then and there added at least 1 year's worth of work to re-do the structural and electrical design.

Growth can be handled by going with the F-414 EPE or even another variant specific to the IAF. Anyway, with ~12 squadrons to order, there is plenty of business that GE Engines is going to get. So they should be amenable to R&D to get an engine that scales up to ~115-120 kNs wet thrust.

One thing I must say - yoking the LCA to the F-404 and F-414 engines has been a great decision. That engine family's reliability, maintainability and fuel consumption specs have really worked well for the LCA program.

[Nishn]

Good Points Kartik. So F-414 derivatives down the road will have enough growth potential to expand all up weight and thrust requirements as needed for evolving munitions and mission requirements. Not up to speed on EPE ! As of now EPE is still on paper right or has it got into the test bench ?

[Kartik]

Read this article here

Basically it would scale up the GE F-414-400's thrust from ~98 kN to ~117 kN, with some added benefits of reducing Specific Fuel Consumption. But without a firm backer in the US Navy, the engine is still on test benches and is not ready as yet.

However, since its still a F-414 variant, the IAF could, theoretically, ask GE to develop it and then have it replace the F-414-INS6 after the first few batches are flying. Basically, do what we did for the Mk1- it started with the F-404 F2J3 engine and then we went on to the F-414 IN20 engine, whose max thrust is ~85 kN.

BANGALORE, INDIA -- Hindustan Aeronautics Limited (HAL) has ordered an additional 24 F404-GE-IN20 afterburning engines to power the first operational squadron of Tejas fighter aircraft for the Indian Air Force. Value of the order is in excess of $100 million and follows an initial 2004 purchase of 17 F404-GE-IN20 engines to power a limited series of operational production aircraft and naval prototypes.

Earlier this year, the F404-GE-IN20 was trial-installed in Light Combat Aircraft (LCA) as part of final evaluations toward flight-testing, scheduled for mid-2007. The F404-IN-20 engine has generated more than 19,000 pounds (85 kN) uninstalled thrust and has completed 330 hours of Accelerated Mission testing, which is the equivalent of 1,000 hours of flight operation.

The F404-GE-IN20 succeeds F404-F2J3 development engines used for nearly 600 flights, cumulatively covering eight engines.

Based on the F404-GE-402, the F404-GE-IN20 is the highest rated F404 model and includes a higher-flow fan, increased thrust, a Full Authority Digital Electronic Control (FADEC) system, single-crystal turbine blades and a variety of single-engine features.

[nachiket]

Basically it would scale up the GE F-414-400's thrust from ~98 kN to ~117 kN, with some added benefits of reducing Specific Fuel Consumption. But without a firm backer in the US Navy, the engine is still on test benches and is not ready as yet.

However, since its still a F-414 variant, the IAF could, theoretically, ask GE to develop it and then have it replace the F-414-INS6 after the first few batches are flying. Basically, do what we did for the Mk1- it started with the F-404 F2J3 engine and then we went on to the F-414 IN20 engine, whose max thrust is ~85 kN.

Kartik, the IAF will have to fund the EPE development. EPE is a much bigger change than the IN20 variant of the F404. I don't think that is about to happen. Not a great idea either, considering our own engine development is languishing due to lack of funds and test facilities.

[Nishn]

117kN ...holly shoot! That's in excess of 26,000 lbs power on the upper end.No need for an F-100/110 class engine. And the family has always had an amazing Spec. fuel consumption record. Thanks again for the feedback.

[Rishi_Tri]

Tejas mk2 cross sectional diagrams in HAL jig assembly tenders.

Front section with canards
http://hal-india.co.in/Common/Uploads/T ... I%20FF.pdf

Mid section
http://hal-india.co.in/Common/Uploads/T ... I%20CF.pdf

Rear section
http://hal-india.co.in/Common/Uploads/T ... I%20RF.pdf


My estimate for total length is 14.5m(1.3m more than mk1).

Description of one of the three above was innocuously given as "Request For Information (RFI) for Design, Manufacture, Assembly, Installation and Certification of Centre Fuselage main Assembly Jig in connection with sub-modules by adopting the methodology of jig-less concepts for Fixed Wing Fighter Aircraft" on HAL tender site. You knew where to look Thank you. I am inspired to peep into these HAL / DRDO tender documents.

[Kartik]

So here is what I was able to work out for the empty weight so far. Still many unknowns, but so far it would seem that the Tejas Mk2 empty weight shouldn't be as high as 8000 kgs.

From the RFI Tenders

The centre fuselage assembly consists of approximately 1600 parts, out of which 40% are sheet metal, 30% are machined parts and remaining 30% are made of Carbon Fibre Composites

Center fuselage - 900 kg

The front fuselage assembly consists of approximately 1300 parts, out of which 40% are sheet metal, 30% are machined parts and remaining 30% are made of Carbon Fibre Composites (CFC).

Front fuselage - 500 kg

The rear fuselage assembly consists of approximately 900 parts, out of which 30% are sheet metal, 40% are machined parts and remaining 30% are made of Carbon Fibre Composites (CFC)

Rear fuselage- 400 kg

Fuselage structural weight (shell)- 1800 kg
Engine weight - ~1111 kg
Radar weight - ~100 kg
Ejection Seat weight- Martin Baker Mk16 LG- between 75-105 kg (assumed to be 100 kgs to be conservative)
Wings weight- ?
Fin weight- ?
Landing gear weight- ~700 kg (assumed as 4%- supposed to be between 3-5% of MTOW- rule of thumb from this source - http://www.academia.edu/24479559/Landing_Gear_Design)
Electrical weight- ?
Avionics weight-?
Hydraulics weight-?
Flight controls weight-?
Wing fuel tanks weight-?
Saddle tanks weight-? ( is it included in the fuselage weights posted in the tender? I cannot say for sure)
Refueling probe weight- assumed to be 30 kgs

Total comes to ~3,141 kgs

So I went back to a book that I had bought a while back- "Lavi" by David Golan where he actually gave the component weights of the Lavi and gave detailed reasoning on why it was lighter than the F-16 Block 30, despite having a similar MTOW. The only reason I would apply something similar was that the Lavi was also a delta wing and that gave it inherent advantages which the Tejas would also have for its wing design.

From the Lavi weights summary, I was able to find the weights from the book that I've tabulated and posted below

Now I went about doing some guesstimations on what might be the empty weight. Of course, some things are not the same on the Tejas, but in general it would give us an idea where things should probably stand.

Extrapolating the figures to the Tejas gives an astonishing empty weight of ~6203 kgs, which is off by some way, since even the Mk1 doesn't weigh that little.



But even if I'm wrong by 15%, that comes to 7135 kgs empty weight for the Tejas Mk2. Make it 20% and the weight is still 7445 kgs empty and if I'm 25% off, it would be 7754 kgs empty weight.

[Gyan]

Empty shell weight would be different from equipped weight which would include partitions, buffers, actuators, wiring, hydraulics, connectors, fasteners, seals, sensors, batteries, motors, pumps, nuts, bolts, screws, paint etc

[Singha]

all these megapixel engine afterburning thrust comparisons are just not meaningful. bigger engine also means more empty weight and more fuel burn at normal thrusts.

Tejas is not going to be a F15E bomb/missile truck ever. so lets make it a GripenE and end the fight.

[Kartik]

That is included in the rest of the equipment summary. I don't think you've even looked at the list properly. Wiring, actuators, hydraulics, sensors, etc. were there on the Lavi as well. Taking the Lavi figures and doing simple ratios and adding a healthy 20% margin for error or variance in design weight, we still only arrive at 7445 kgs empty.

Anyway, Aero India 2019 will hopefully shed more light on the target empty weight. We can then see how far off my guesstimate was.

[suryag]

Kartik garu, you are awesome.

w.r.t the dates, am still positive we will ahve the first rollout in 2020 and the first flight in that year itself. The jigs sourcing is a good example of concurrent manufacturing practices something that wasnt followed during MK1. The IOC is most likely going to have the same weapons suite as chota bhai(MK1A) and the large points of validation would be towards the flying characteristics(canards, wing changes etc)

[hemant_sai]

Looking at timelines, if we are optimistic to have 01st flight of Mk2 at the end of 2020, I see equal possibility that by end of 2023 we can have IOC and start producing MK2 from APR-2024.
On the other hand Mk1 FOC production is expected to continue till end of 2021. With 8 FOC trainers, it will be end of 2022 or MAR 2023.

If optimism on MK2 is justified, do we see any need to go for MK1A production?
As IOC production of MK2 can start from APR-2024, it is more wise just to continue MK1 FOC production for 01 more year. My proposal is to skip Mk1A and order 60 + 240 = 300 MK2. So total Tejas platform will be (63 Mk1 + 300 Mk2). Please note that 83 Mk1A are adjusted as 60Mk2 and 23 Mk1 FOC.

There can be parallel upgrade program of these 63Mk1 to Mk1A along with Mk2 production or when appropriate. But priority should be given to MK2.

With 300 Mk2 order and 24/year, production would continue for 13 years i.e. APR-2024-APR-2035. This is quite long span, So it should be pre-notified that every 2 years incremental upgrades will be delivered. In other words, whatever improvements will be achieved in 2 years will be freeze to deliver for next 2 years.

I pray for MK2, there won't be unnecessary delays over cost.

[Thakur_B]

With the gun being shifted, it seems we might get a pylon where the gun was supposed to be.

[JayS]

With the gun being shifted, it seems we might get a pylon where the gun was supposed to be.

Good point.

Another observation is the canopy doesn't have the expected shape change for supersonic drag related optimization.

Presence of canard and elongated fuselage should make that discontinuity in area ruling much smoother now increasing the transonic and supersonic performance significantly. So perhaps its not needed anymore. But I would have liked that rounded canopy anyhow. It looks so much better.

I think LCA is only aircraft in modern times whose trainer version looks way more cooler than single seater version. All other I see are eye sore to me, including Rafale.

[Bala Vignesh]

Jingo bahut khush hua!!
My only pet peeve is that they could have provisioned some space to handle bigger more powerfulengines at a later date, as seen in the case of Jags. Having this facility would give us more options to go with, if and when we plan for an engine upgrade.

[ashishvikas]

Apparently, to recover some of the directional stability lost due to the elongation of the Tejas fuselage and the addition of canards, modifications to the vertical fin are necessary.

https://twitter.com/SJha1618/status/109 ... 67136?s=19

[tsarkar]

So finally we did end up with a close coupled canard to re-energize the airflow over the wing to meet the STR requirement!

This was one major area of design disagreement in the Mk1 between IAF & ADA.

Request Indranil, JayS & Maitya for their analysis.

[SaiK]

The only engine you are allowed to talk about changing here would be Snecmized K9 or K10.

[tsarkar]

With the gun being shifted, it seems we might get a pylon where the gun was supposed to be.

I hope the GSh-23 is replaced with a newer GSh-301 like MiG-29 & Su-30MKI or GIAT30. We've already chosen the 20mm version of GIAT/Nexter for Rudra & LCH.

[brar_w]

However, since its still a F-414 variant, the IAF could, theoretically, ask GE to develop it and then have it replace the F-414-INS6 after the first few batches are flying. Basically, do what we did for the Mk1- it started with the F-404 F2J3 engine and then we went on to the F-414 IN20 engine, whose max thrust is ~85 kN.

I was speaking to a GE representative at a US naval Institute organized event in late 2017 about this and the basic reaction was that it is going to be very tough (from a business case perspective) for either GE alone or GE + foreign partners (Korea, India or Sweden) to fully fund all the enhancements they have on the bench or in the lab. Basically, the cost, range and test infrastructure they need really needs the backing (financial) of the US Navy so they were prepared to wait for it as the business case, in terms of fuel savings and performance enhancements for the very large fleet (and growing) of twin engine fighters with the USN that will form the backbone of its Air Wing for at least 10-15 years, IS STRONG. The next US Defense budget comes out on March 18th an I wouldn't be surprised if there is money towards this in it.

[Lilo]

I wonder if LCA Mark 2 is adopting the design philosophy of F16XL? Whether we can understand LCA MK2 Better by looking at F-16XL?

Some Good open source Research based Articles on (Cranked Delta Wing of) F-16XL (rather than fan boy estimates)

https://www.nasa.gov/sites/default/file ... flight.pdf

http://www.f-16.net/forum/download/file.php?id=18581

For my untrained amateur eyes LCA Mk1 vs Mk2 progression looks most akin to Mirage 2000 vs Mirage 4000 (aka the Super Mirage) but both with a single engine setup.


Do we have an estimate on how much % the wing size increases b/w LCA Mk1 vs Mk2?

[hemant_sai]

The only engine you are allowed to talk about changing here would be Snecmized K9 or K10.

Whatever recent articles I read, they had no mention of Kaveri for any of Tejas variant. It was only mentioned as planned for AMCA. Right now it seems as if suddenly engine program has become classified. No news on it since August 2018, neither IAF or DRDO mentioned it in any context of recent Tejas announcements.
We don't even know if Snecma has taken full responsibility to integrate Kaveri and make it work by end of 2019. Keeping fingers crossed for some announcement in Aero India show.

[JayS]

Been checking the CAD images closely.

- Air intakes start before the wing now. Starting of the inlet doesnt look like its moved. So it must be wing which is pushed back.
- Looks like there is a strake ahead of the wing. Basically wing moved back by some distance it seems. Is this the plug ADA has been talking about..? So there is a strake from original wing starting point blending in the LE of moved wing.
- I dont see the air intake BL spillway over the wing anymore.
- Is there some elongation of the nose ahead of the point where the windshield starts..?
- looks like rear fuselage us slightly modified.
- considering the engine nozzle, the total length should be 14.5m.

I cant wait to see MK2 model in coming Aero India. I hope all the details would be clear then.

[fanne]

When LCAMK2 is made, will it's wing be of the same shape and size (or they also correspondingly increase?) as LCAMK1?

[Mollick.R]

The only engine you are allowed to talk about changing here would be Snecmized K9 or K10.

Yes exactly.

Pardon this nanha abdul, but i think without a domestic Jet engine K9 or K10 or whatever one calls it we will be held hostage by an unreliable country like US.

With bunch of our would be frontline A/Cs flying on GE engines they will hold us by our b@lls for sure. Murrika will start throwing tantrums and ask India to sing in their tune on every geopolitical issue.

[Mollick.R]

It's high time that PMO, MOD, IAF comes on a single page and declare domestic jet engine a national stratetic project like IGMDP and allocate fund and other resources without any hold.

Else it will be totally unwise for our strategic planners to put all eggs on US basket and have sanction prone 320+ frontline ACs.

Just my take.

[Indranil]

So finally we did end up with a close coupled canard to re-energize the airflow over the wing to meet the STR requirement!

This was one major area of design disagreement in the Mk1 between IAF & ADA.

Request Indranil, JayS

I have asked JayS to help me with the article. Please stand by. Will answer to the best of my ability. Mk2 is going to be a looker and a keeper.

[Kartik]

Been checking the CAD images closely.

- Air intakes start before the wing now. Starting of the inlet doesnt look like its moved. So it must be wing which is pushed back.
- Looks like there is a strake ahead of the wing. Basically wing moved back by some distance it seems. Is this the plug ADA has been talking about..? So there is a strake from original wing starting point blending in the LE of moved wing.
- I dont see the air intake BL spillway over the wing anymore.
- Is there some elongation of the nose ahead of the point where the windshield starts..?
- looks like rear fuselage us slightly modified.
- considering the engine nozzle, the total length should be 14.5m.

I cant wait to see MK2 model in coming Aero India. I hope all the details would be clear then.

Yes, the air intakes as well as the wing stub now start right where the canopy ends. Rather than the wing being pushed back, the forward fuselage has been elongated. That has created some space to mount the hinge for the canard, plus created some more room for avionics to be placed behind the cockpit.

Regarding the spillway, it was between the fuselage and the intakes earlier..so without seeing the wing plan, we may not be able to decipher if the boundary layer spillway is gone or not..But then again, the canards will be spilling their tip vortices and energize the wing boundary layer as well as the wingtip vortices..so perhaps the need for the BL spillway is negated and hence eliminated?

Regarding the radome, you're right. There is definitely a small plug inserted in there just aft of the radome attachment points.



And yes, length would be ~14.5m considering engine nozzle, but without taking into account the pitot probe length.

[gaurav.p]

1. Air intakes start before the wing now. Starting of the inlet doesnt look like its moved. So it must be wing which is pushed back.
2. Looks like there is a strake ahead of the wing. Basically wing moved back by some distance it seems. Is this the plug ADA has been talking about..? So there is a strake from original wing starting point blending in the LE of moved wing.
3. I dont see the air intake BL spillway over the wing anymore.
4. Is there some elongation of the nose ahead of the point where the windshield starts..?
5. looks like rear fuselage us slightly modified.
6. considering the engine nozzle, the total length should be 14.5m.

1. Indeed saar, the wing has been pushed back.
4. Yes, the nose seems to be elongated to me as well. Shown in green. Also interesting to note is that the shape of canopy has changed. The joint connected with the avionics cover isn't straight as in mk1. maybe more space for LRUs
5. Also in the rear fuselage, the trail edges end till the end of the fuselage. But in mk1 it isn't the case.
7. There is also something called longerons in the center fuselage. I guess, it is added in order to tackle the vortex of canards.
8. Can someone explain this image? Also the yellow thing in the image, below the stub wing?

[Kartik]

1. Indeed saar, the wing has been pushed back.
4. Yes, the nose seems to be elongated to me as well. Shown in green. Also interesting to note is that the shape of canopy has changed. The joint connected with the avionics cover isn't straight as in mk1. maybe more space for LRUs
5. Also in the rear fuselage, the trail edges end till the end of the fuselage. But in mk1 it isn't the case.
7. There is also something called longerons in the center fuselage. I guess, it is added in order to tackle the vortex of canards.
8. Can someone explain this image? Also the yellow thing in the image, below the stub wing?

The stub wing, where the wing joins with the forward fuselage now joins just at the end of the canopy whereas on Mk1 the stub wing was almost 0.4m ahead of the canopy end. All in all, a slightly longer forward fuselage.

Longerons are structural elements. They have nothing to do with the canard vortices.

Canopy shape has definitely been refined, based on the studies that were done to improve area ruling. It isn't as pronounced as it was in the studies, but a more refined shape for sure.

[gaurav.p]

The stub wing, where the wing joins with the forward fuselage now joins just at the end of the canopy whereas on Mk1 the stub wing was almost 0.4m ahead of the canopy end. All in all, a slightly longer forward fuselage.

The front fuselage looks longer due to elongation at the nose. Will it be incorrect to say that the wings have been shifted back?

Longerons are structural elements. They have nothing to do with the canard vortices.

such a raw mango I am

[Kartik]

I would just say that the wing join is now happening further aft of where it was on the Mk1. The lengthening of the forward fuselage makes it appear that the wings are shifted aft but if you see the rear fuselage, the wing doesn't end further aft, which would be the case if the wing was pushed back. AFAIK, the wing size has not been changed.

[Kartik]

IR, could you please check if the Avionics cover is basically a continuation of the perspex canopy or an opaque fairing, like what's present on the NP-2 prototype?

[Indranil]

Don't see a need for the perspex canopy Kartik. It was obviously easy to go for such a canopy for NP2, because it is a one off. You know why they would do so.

[Indranil]

Been checking the CAD images closely.

- Air intakes start before the wing now. Starting of the inlet doesnt look like its moved. So it must be wing which is pushed back.
- Looks like there is a strake ahead of the wing. Basically wing moved back by some distance it seems. Is this the plug ADA has been talking about..? So there is a strake from original wing starting point blending in the LE of moved wing.
- I dont see the air intake BL spillway over the wing anymore.
- Is there some elongation of the nose ahead of the point where the windshield starts..?
- looks like rear fuselage us slightly modified.
- considering the engine nozzle, the total length should be 14.5m.

I cant wait to see MK2 model in coming Aero India. I hope all the details would be clear then.

Yes, the air intakes as well as the wing stub now start right where the canopy ends. Rather than the wing being pushed back, the forward fuselage has been elongated. That has created some space to mount the hinge for the canard, plus created some more room for avionics to be placed behind the cockpit.

Regarding the spillway, it was between the fuselage and the intakes earlier..so without seeing the wing plan, we may not be able to decipher if the boundary layer spillway is gone or not..But then again, the canards will be spilling their tip vortices and energize the wing boundary layer as well as the wingtip vortices..so perhaps the need for the BL spillway is negated and hence eliminated?

Regarding the radome, you're right. There is definitely a small plug inserted in there just aft of the radome attachment points.



And yes, length would be ~14.5m considering engine nozzle, but without taking into account the pitot probe length.

There is a plug in the nose, and also behind the canopy. the wing appears to start at the same place, but it doesn't. More details in the article. The spillway exists in Mk2 as well.

[Kartik]

So the Avionics cover is basically composite skin?

Another question that arose, is there going to be a Tejas Mk2 twin seater? Or will the Tejas Mk1 trainers support conversion onto the Mk2 fleet as well along with simulators?

[Indranil]

Going for a composite skin is cheaper.

Don't know the answer to the trainers question.