LCA Tejas: News and Discussions

Karan M · Post by **Karan M** » 30 Sep 2015 22:10

srin wrote:Sirjee, you are counting the chickens before they hatch. I'd love for us to have 400 aircraft, but ...

The reality is the LCA is now at IOC and will accomplish FoC by March 2016. And that is all for Mk1. The assured orders exist for them. HAL is delayed in the IOC aircraft.

Mk-1A with weight savings and new radar etc will take another 2-3 years for IOC. And we'll only get aircraft manufactured from 2020 onwards then. So, even production rate of 1 squadron a year would only appear five years from now.

Then Mk2 may get delayed ...

I wouldn't worry so much _if_ the MK1A gets approved... what it means is a constant stream of LCAs..

indranilroy wrote:Karan, this is not from the new assembly hangar.

Do we have pics of that? Eitherways good to see HALs new lines - Su-30, Hawk and LCA as clean and well laid out.

Upgrade everything to super-light Mk1A standard during MLUs.

The structural changes to Mk1 are so substantial that it would be akin to making a new aircraft. MLU upgrades won't be possible.

What MK1A is promising is ASR level performance. Its a step up from the first MK1P which we heard of, that only spoke of ballast removal + radar replacement + addition of EW, which would basically just save a few kilos at most.

Gyan · Post by **Gyan** » 30 Sep 2015 22:12

ramana wrote:P Bhat. I agree with your comment.

So Kalmadi has consistently sabotaged LCA from the beginning in 1985.

IB needs to look into why? Whose interests is/was he representing all these years?

Mirage 2000 lobby, I guess from the time period

Viv S · Post by **Viv S** » 30 Sep 2015 22:14

Do we have any other sources confirming that the Mk1A will be equipped with the Uttam AESA instead of the EL/M-2052? Unless... the 2052 is feeding into the Uttam program (like the 2032 did the MMR).

Karan M · Post by **Karan M** » 30 Sep 2015 22:24

Not at this time.. the decision will probably be taken by the IAF depending on Uttam maturity and performance..during flight trials. If its lagging, then it can always be used for Mk2. Need of the hour is to get as many LCAs in AF fast, the radar can be processed in parallel.. now we have the AWACS program progressing our A2A effort which can feed into the FCR, so the tech development aspect and long term plan is still being progressed.

SaiK · Post by **SaiK** » 30 Sep 2015 22:28

Not clear on some of these reports (silly/truth?) that talks about Uttam AESA. The one on idrw references weight issues as the cause for Uttam. Give me a break! When they report it is Indian version of 2032, then how is that Indians don't know for the same or similar specs, the weight must be maintained.

Another interesting is 1000kg shaved off the 6500k. How did they do it?

JayS · Post by **JayS** » 30 Sep 2015 22:46

indranilroy wrote: No, they are speaking of the "thing" on the port side of the leftmost plane, at pilot head height.

That thing looks far aft from canopy area to my eyes. Anyway..

indranilroy wrote:Absolutely, There is no way in hell that Mk-1As can get FOC before 2020!!! So why this parallel Mk1A and Mk2?

The problem is that HAL and ADA don't work on this project as one. As you said, HAL and ADA should join forces to bring the Mk2 IOC to 2020. IAF could be asked to increase the Mk1 orders. Don't promise anything, but whatever can be brought forward from the Mk2 design to the Mk1 design can be done after the first batch of 40 Mk1s. Call it Mk1As and call it a day. Upgrade everything to super-light Mk1A standard during MLUs.

I am not so much worried about FOC/certification for MK1A. The things always go quite quicker in second attempt. But my worry is more with HAL's apparent reluctance with going for MK2 quickly. Did they propose these weight reduction changes while MK2 was being discussed 3-4 years ago?? I at least have never heard about these tall claims before. If they had proposed these changes back then and they are already accommodated in MK2 Preliminary design then all is well and my worries are unfounded. But if HAL has come out with these changes only now, that too just with the intention of somehow stretching MK1 production, then ADA will have to revise MK2 preliminary designs as well to consider these changes. That is unacceptable. MK1A should not be at the expense of inordinate MK2 delay. Perhaps a delay of a year on account of MK1A is acceptable to IAF given that they will get better version meanwhile.

MK1A could be a good opportunity only if the project management could use it well. As we have already mentioned here, bringing in some of the changes from MK2 in MK1A will reduce development time on MK2 itself. And of coarse improvements done in MK1A will only further make MK2 better only. But they need to make sure that the time factor is handled carefully, else it will be "Too many cooks.." situation. Go for changes which will not need too much efforts on recalibration of FCS/certification e.g. AESA, weight reduction in LG without changing the internal structural components, some lighter LRUs, reshuffling to remove as much of the ballast as possible without changing CG location by much.

My guess is IAF will need at least 5-6 years to assimilate LCA fully, but after that they need to be given full fledged LCA so that they can integrate it fully in their doctrine with operational readiness. So ADA/HAL has this 5-6 years of window in which they should deliver MK2. This target should not be compromised at all.

Karan M · Post by **Karan M** » 30 Sep 2015 22:49

Most importantly MOD has to tackle this on a warfooting. Single window program office with PMO/MOD monitoring and making sure HAL etc don't slack on the job and IAF is onboard fully.

Indranil · Post by **Indranil** » 30 Sep 2015 23:07

^^^ That is probably the most important thing now.

SaiK · Post by **SaiK** » 30 Sep 2015 23:13

MOD reps should have monthly charchas with HAL honchos.

JayS · Post by **JayS** » 30 Sep 2015 23:16

shiv wrote:LCA cutaway drawing
http://i384.photobucket.com/albums/oo29 ... lcacut.jpg

Unable to see the structures to which the landing gear is attached. But some guesswork is possible. If the landing gear weighs 500 kg normally - it will weigh 2500 kg in a 5 G manoeuvre (or 4000 kg at 8G) The LCA has now flown for a decade with this extra weight and clearly the airframe is able to withstand such stresses. Now if the weight of the landing gear is reduced by 100 kg, that translates to 2000 kg in a 5G manoeuvre - i.e half ton less (or 3200 kg at 8G - almost a ton less). That means that the structure that attaches the wings to the main frame can do with reduced strength and weight because of the reduced weight of the landing gear as G forces on that structure will be smaller.

The question may be one of engineering. What are the actual load and stress bearing structures like - what materials and strength? It is plausible that some of these structures are amenable to weigh reduction relatively easily - but obviously this is just "hopeful guesswork" on my part. No inside knowledge. But if someone from inside the program says it is feasible - there may be something to it.

My opinion. Happy to be corrected:-

MLG is nicely tucked in very compact position during flight. Also its placed very near to the CG of the aircraft. The stresses it induces during manoeuvre will not be so dramatic as with the case of say pylon load (which is trying to rip-off from the wing under G load causing large bending stresses at wing root). Of coarse some strengthening of surrounding structural parts is resulted by heavier MLG, but my guess is the sizing here would be decided by the impact loads at the time of landing rather than manoeuvre loads. Impact loads at the time of landing should be far greater than G loads caused by MLG on the structural components to which it is attached.

If we think about NLCA, the over-design was due to higher sink rate used for design, which means higher impact loads resulting in heavier MLG as well as heavier supporting structural components which need to absorb these higher impact loads ultimately.

The reduction in MLG weight and elsewhere will reduce total weight of a/c giving reduced impact loads on landing. This will allow some optimization of those inner structural components.

Indranil · Post by **Indranil** » 30 Sep 2015 23:17

Karan M wrote:
indranilroy wrote:Karan, this is not from the new assembly hangar.
Do we have pics of that? Eitherways good to see HALs new lines - Su-30, Hawk and LCA as clean and well laid out.

http://tarmak007.blogspot.com/2013/12/f ... -hals.html

Click for higher resolution

chaanakya · Post by **chaanakya** » 30 Sep 2015 23:20

Karan M wrote:Saurav Jha:

There'll be no IOC/ FOC campaign per se for the Mk-1A. The improvements will be made concurrently with the production process.

OMG... what a news. So RM delivers Plan B to IAF . Anyway I always though FOC from IAF sounded more like F**K Off Cutie. Good that it is now out of the way. Next step should be to tie raising all squadrons with production and delivery schedule of LCAs. And for that to happen encourage private industries to set up supply chains for components of LCAs which are to be manufactured and encourage HAL leadership to set their house in order or else....

SaiK · Post by **SaiK** » 30 Sep 2015 23:28

do you want to rewind back 30 years? but I tell you the authors then were at least doing some homework while putting out articles. the quality aam-admi reports have gone down the drains

Karan M · Post by **Karan M** » 01 Oct 2015 00:04

If there is a Mk1A program AND there is a parallel line for the LCA in a private firm.. that'll completely make my day..HAL needs competition.

SaiK · Post by **SaiK** » 01 Oct 2015 01:32

If we take a cue at confidence level, business mindedness it tells the private should seek for this with their capabilities than wait for policies to come out. They have to invest, and not keep quite for magic to happen. It was the private world that invented stuff for the Americans with deep gov regulations. We have to consider some big changes for that.

Vivek K · Post by **Vivek K** » 01 Oct 2015 01:48

Chaanakya, good observation. The RM has helped IAF see the light. This is a good development.

ramana · Post by **ramana** » 01 Oct 2015 01:53

KaranM Even US is unable to keep two fighter production houses in business.

The supply chain has to be cranked up but HAL will have to deliver the fleet.

Indranil · Post by **Indranil** » 01 Oct 2015 02:11

I don't think the two assembly lines is a good idea. There should be one principal integrator which integrates large parts together into a plane. This assembly line should produce 40 planes a year. Delegate part manufacturing to the private industry. Our private industry is already ready for that. Tata, Dynamatic Technology, Mahindra are already Tier I suppliers to quite a few prestigious projects.

SaiK · Post by **SaiK** » 01 Oct 2015 04:10

I kinda disagree, however I agree on concurrent engineering is better controlled from single line management. But multiple assembly lines are perfectly possible depending on the needs. It is a great idea, if we have perfected LRUs, component line assemblies, and critical paths with least break/wait down time for each component in their dependency chain.

srai · Post by **srai** » 01 Oct 2015 04:35

Final assembly can be one at HAL but major components should be divided into workshares between Tier1 suppliers (as indranil suggested). Something akin to this:

With this approach, India will be able to create multiple Tier1 aerospace manufactures/suppliers rather than just one private "HAL-monopoly-like" entity.

Cain Marko · Post by **Cain Marko** » 01 Oct 2015 04:51

Call me skeptical, but my guess is that HAL is unable to meet the FOC deadline for 4 SPs and so is now throwing a new carrot into the fray, the Mk1.A; not a bad idea perse, but it should be required to deliver what it promised and the IAF is waiting for - the mk1 @ FOC std....this in itself is an achievement.

Once these 40 are delivered and production stabilized, don't see why Mk1.A can't come online - circa 2018. In the meanwhile, IAF should (and I believe) will order additional Mk1.As once initial SPs are delivered at FOC std.

Feeling one gets is that both IAF and ADA are wating for/ready with mk1, but HAL is not where it needs to be hence the above. Don't think people will buy it.

uddu · Post by **uddu** » 01 Oct 2015 05:47

The HAL's complaint that they have to sit idle after making the first 40 MK1 variant is addressed by the government by allowing HAL to make MK1A from 2017. Hopefully HAL will be making around 20 aircraft's per year ensuring the production to continue for 7 more years until 2023 for 126 MK1A. Once the MKII is ready by 2022/23 the production rate can be increased and 200 plus aircraft delivered by2030. Add any request from friendly countries and surely it's going to reach 500/600 mark by 2030.

SaiK · Post by **SaiK** » 01 Oct 2015 05:50

What about international customers? Come Mk2, I am extremely positive of that happening.
So, they have to plan for expansions ahead. A single Modi visit can sign big deals with few countries.

of course, we need to get Mk2 be used by IAF. But, then IAF using any version of LCA is enough to market for Modiji.
With him as salesman, it is a shame not to think about exports

uddu · Post by **uddu** » 01 Oct 2015 05:59

Even MK1A will find customers since it's a good aircraft with AESA radar and other bells and whistles with weight reduction as well. Comes at very reasonable price. So expect orders for that as well. Seems as reported earlier the requirement for the IAF for the MK2 variant is around 300 aircraft. So the initial order of 126 will be 40 MK1+86 MK1A
The first 40 may be later fitted or upgraded to the MK1A variant to the extent possible.
The production will most possibly like
40 MK1 to end by 2017 end and MK1A to start for the remaining 86 aircraft and continue till 2021/22.Based on any foreign order for MK1A, the production can be increased upto 30 per/year. We do have the option of exporting upto 50-60 MK1A's to friendly countries. From 2022/23 onward MK-II can be mass manufactured for IAF and friendly nations and even to meet IAF's own requirements the production has to be tripled from the 20 to 60 aircraft's per year.

Where's the lungi dance icon.
And nearby to this production facility we can produce the HAL AMCA which will have commonality of 30 percent or so with the MKII in terms of Radars and other avionics etc.

shiv · Post by **shiv** » 01 Oct 2015 07:30

nileshjr wrote: MLG is nicely tucked in very compact position during flight. Also its placed very near to the CG of the aircraft. The stresses it induces during manoeuvre will not be so dramatic as with the case of say pylon load (which is trying to rip-off from the wing under G load causing large bending stresses at wing root). Of coarse some strengthening of surrounding structural parts is resulted by heavier MLG, but my guess is the sizing here would be decided by the impact loads at the time of landing rather than manoeuvre loads. Impact loads at the time of landing should be far greater than G loads caused by MLG on the structural components to which it is attached.

What you say is, I am sure, true, but no matter how close to the center of mass a particular item may be it will add to the stress between wing root and fuselage. 1000 kg sitting exactly at the CG translates to 5000 kg exactly at CG in a 5G manoeuvre and that 5000 kg is being held up by lift acting on the center of lift in the wing some meters away causing large stresses.

Anyhow - it does not matter whether the extra weight is because of landing impact or because of something else - there is a domino effect of increasing or decreasing weight so that every kg shaved off landing gear can translate to several extra kg shaved off other structures provided the engineers get their modelling and calculation right.

pragnya · Post by **pragnya** » 01 Oct 2015 08:29

if the buzz is true and if the HAL/ADA can shave off even 500kg weight, taking into account the aerodynamic drag improvement that has been accomplished and would be implemented in due course, LCA 1 would turn out great as Shiv pointed out.

let me speculate - it may well be possible LCA 2 may not happen for the IAF. as is known the IAF did not have a requirement for mark 2 version which was purely IN requirement - a fact emphasised by the late Pervez Khokar and confirmed by Kartik speaking to the navy guys - Sukesh Nagaraj/Mao @aero 2013.

in a way this would be good as it would not affect the timeline as much as a mark 2 would and the IAF gets the numbers in much quicker time.

mark1 & 1A for the IAF and mark 2 for the Navy which is ongoing parallely.

shiv · Post by **shiv** » 01 Oct 2015 08:55

srai wrote:

With this approach, India will be able to create multiple Tier1 aerospace manufactures/suppliers rather than just one private "HAL-monopoly-like" entity.

Ironically HAL itself is two tier 1 suppliers
1. For Western and Indian aircraft
2. for Russian Aircraft

That would exclude Nasik, Koraput and that Russian avionics town - wherever that is, leaving IIRC Bangalore and Bengaluru wonlee.

Yagnasri · Post by **Yagnasri** » 01 Oct 2015 09:06

No gurus answered my mango question - Is it easy to have structural changes in Mk1 and have Ge414 in it or to shave off 1000 kg wight?

With its wight being reduced can Kaveri be option for LCA. I think not. That boat has long sailed I guess.

kvraghav · Post by **kvraghav** » 01 Oct 2015 09:53

Read in the kannada regional paper. Loosely translated as:
HeadLine: Is govt forcing a underperforming aircraft on IAF?
Due to the force depletion, the govt is forcing the IAF to procure at least 7 squadrons of Mk1 although the IAF wants the Mk2.

srai · Post by **srai** » 01 Oct 2015 10:06

kvraghav wrote:Read in the kannada regional paper. Loosely translated as:
HeadLine: Is govt forcing a underperforming aircraft on IAF?
Due to the force depletion, the govt is forcing the IAF to procure at least 7 squadrons of Mk1 although the IAF wants the Mk2.

... versus what? ... "Is govt forcing the IAF to keep using obsolete aircraft (MiG-21/27)?"

Yagnasri · Post by **Yagnasri** » 01 Oct 2015 10:08

I will not be surprised if there is a Pappu statement on LCA and how evil BJP is forcing IAF to take it after getting bribes from HAL.

member_22539 · Post by **member_22539** » 01 Oct 2015 11:12

^Kannada regional paper eh? Seems like the pimps have groomed presstitutes in regional papers as well.

JayS · Post by **JayS** » 01 Oct 2015 11:22

shiv wrote: What you say is, I am sure, true, but no matter how close to the center of mass a particular item may be it will add to the stress between wing root and fuselage. 1000 kg sitting exactly at the CG translates to 5000 kg exactly at CG in a 5G manoeuvre and that 5000 kg is being held up by lift acting on the center of lift in the wing some meters away causing large stresses.

Anyhow - it does not matter whether the extra weight is because of landing impact or because of something else - there is a domino effect of increasing or decreasing weight so that every kg shaved off landing gear can translate to several extra kg shaved off other structures provided the engineers get their modelling and calculation right.

What i meant is the support structures are already designed for much higher loads than what manoeuvrings loads of MLG would induced on them. Impact load at landing which is far higher than any load MLG could induce at 9G, will be the criteria deciding support structure's design and weight. So reducing MLG weight does not result in any (or perhaps any significant) weight saving in support structures.

I talked to a friend who was leading structural analysis project for MLG and its supporting structures for one of the Airbus Airliners. He corroborated my logic saying for airliners they never even considered manoeuvrings loads on MLG (though civilian jet are designed for 2.5G AFAIK the LG is much much heavier than MLG of fighters which are typically designed for 9G). They would design the MLG and its support structure (its attached to rear spar and False rear spar of the wing using one hinged joint and one ball-and-socket joint) for impact load at landing which is calculated as 4.5*Empty weight of aircraft (impact loads would be about ~2-2.5 times the actual landing weight, you can work out this ballpark figure easily considering the vertical momentum that has to be absorbed by the MLG/Support structures). Considering we can use similar methodology for LCA (albait military jet must be designed for higher sinking rate thus the factor might be higher, but lets keep it aside for brevity), the support structures would be designed for 4.5*6500kgf ~ 30000kgf i.e. 15000kg on each MLG. The MLG for LCA, over-designed as they may be, are still quite light. Even at 12G ultimate limit the forces would be far far less than 15000kg at any rate. If you consider from fatigue design POV they are inconsequential at those levels.

Also please note that there is locking mechanism which holds the landing gears when they are retracted, hence the G loads induced by them are shared by two spars and the locking link, reducing the effective stress on the spar linkages even further.

So unless there is any change in Max allowed Landing weight, there will be no redesign of support structures and even otherwise I do not think there will be reduction by "sevaral kgs on support structures per kg reduction in MLG weight".

There was once a tender regarding LCA landing gear which had few parameters mentioned. Anyone has the document readily available?? I will have to dig out from somewhere if not. Those parameter could help in better estimation of things.

JayS · Post by **JayS** » 01 Oct 2015 12:11

Yagnasri wrote:No gurus answered my mango question - Is it easy to have structural changes in Mk1 and have Ge414 in it or to shave off 1000 kg wight?

With its wight being reduced can Kaveri be option for LCA. I think not. That boat has long sailed I guess.

Not a guru but still would give a try.

Both are difficult. Re-engine task would involve redesign of deep structural components (higher thrust, possible different weight distribution, higher inlet dia and other factors which I can't think of now), redesign of air-inlet for higher inlet dia and higher mass flow rate (79cm vs 71cm of F404) and re-calibration of FCS due to changed thrust levels and possibly due to some changes in CG due to engine and changed structural components and/or re-shuffling of LRUs for CG variations and many other small small things. Fortunately the length and outer dia for both F404IN20 and F141INS6 are same, so a lot of trouble is eliminated there.

Funfact: Recently got to know that F404 is due to the length=404cm of original version of F404 for the F18 et al. But the newer iterations are 391cm long and so is F414.

About the proposed 1000kg shave off, a lot of people are skeptical as you would have already seen, including me. Lets hope we are just a bunch of whining morons who always suspect what SDRE people could achieve with their SDRE skills and are worrying unnecessarily out of our ignorance and lack of domain knowledge.

And indeed the boat has long sailed, its a big big missed opportunity with hundreds of engines to have produced over entire LCA fleet. We have just made prototypes of Engines, we are yet to industrialize the engine and set-up MRO facilities. There is a lot to be done on these two fronts as well, which is not possible until we actually try to put Kavery in some aircraft. Hopefully there will be some LCA batch in future fitted with Kaveri. The way things go now-a-days with modular concepts used in F404 family, practically only one engine can be used for entire life of the a/c without having to change it ever, only replace spare parts based on diagnostic/prognostic Life Management systems/maintenance plans. That's what is being done for RM12, there is no concept of MTBO, big overhauls etc. So we can very well expect that LCA will never see any engine change (I don't know what kind of contract we have sighed with GE but I am going with the most probable option). Only if we show some foresight and are ready to take the economical toll, we might see re-engine program for part or entire fleet of MK1/MK1A. Would you bet your money on that??

shiv · Post by **shiv** » 01 Oct 2015 14:03

nileshjr wrote:
What i meant is the support structures are already designed for much higher loads than what manoeuvrings loads of MLG would induced on them. Impact load at landing which is far higher than any load MLG could induce at 9G, will be the criteria deciding support structure's design and weight. So reducing MLG weight does not result in any (or perhaps any significant) weight saving in support structures.

I talked to a friend who was leading structural analysis project for MLG and its supporting structures for one of the Airbus Airliners. He corroborated my logic saying for airliners they never even considered manoeuvrings loads on MLG
<snip>
So unless there is any change in Max allowed Landing weight, there will be no redesign of support structures and even otherwise I do not think there will be reduction by "sevaral kgs on support structures per kg reduction in MLG weight".

No no no no. You and I are talking about two completely different things. I am not talking about landing stresses on the landing gear and support structures at all. There may be scope for weight reduction in other areas as a consequence of landing gear weight reduction, which I will explain.

If you ignore fuselage lift and consider the wings as the only (or main) lifting surfaces, those wings are attached to the fuselage by spars while the fuselage itself acts as a deadweight. On the ground the spars support the weight of the wings acting through the spar/s. In flight those same spars support and lift the deadweight of the fuselage. The wings are lifted up (by aerodynamic lift in flight) and that lift is transmitted via the main spar/s to lift the dead weight of the fuselage. Under high G circumstances (in all aircraft) the wings are trying to tear themselves off the fuselage, but they do not tear off because the spar/s are strong enough to remain attached to and support the fuselage at the point that they are attached to the fuselage. The heavier the fuselage, the greater the stress on the fuselage-mainwing spar/s joint in flight and high G stresses are correspondingly greater.

The lighter you make the fuselage - the less the stress on the fuselage-spar joint and the spars themselves during flight. Any weight reduction of the fuselage - be it main gear or anything else would lead to a corresponding decrease in the stresses on the main spar and spar-fuselage joint. A mainwing spar that is strong enough for a 10 G manoeuvre on a 7,000 kg plane would be over engineered in case the maximum weight of the aircraft for a 10G manoeuvre is only 6,000 kg. The entire mainwing spar and/or its joint with the fuselage can be made a little lighter for a lighter maximum weight in the fuselage.

That "lighter fuselage weight" could be by shaving off some weight from an over engineered landing gear and that leads to the possibility of shaving off even more weight from over engineered wing spars that no longer need to fly with as heavy a weight as they were originally engineered for.

JayS · Post by **JayS** » 01 Oct 2015 14:48

shiv wrote:
No no no no. You and I are talking about two completely different things. I am not talking about landing stresses on the landing gear and support structures at all. There may be scope for weight reduction in other areas as a consequence of landing gear weight reduction, which I will explain.

If you ignore fuselage lift and consider the wings as the only (or main) lifting surfaces, those wings are attached to the fuselage by spars while the fuselage itself acts as a deadweight. On the ground the spars support the weight of the wings acting through the spar/s. In flight those same spars support and lift the deadweight of the fuselage. The wings are lifted up (by aerodynamic lift in flight) and that lift is transmitted via the main spar/s to lift the dead weight of the fuselage. Under high G circumstances (in all aircraft) the wings are trying to tear themselves off the fuselage, but they do not tear off because the spar/s are strong enough to remain attached to and support the fuselage at the point that they are attached to the fuselage. The heavier the fuselage, the greater the stress on the fuselage-mainwing spar/s joint in flight and high G stresses are correspondingly greater.

The lighter you make the fuselage - the less the stress on the fuselage-spar joint and the spars themselves during flight. Any weight reduction of the fuselage - be it main gear or anything else would lead to a corresponding decrease in the stresses on the main spar and spar-fuselage joint. A mainwing spar that is strong enough for a 10 G manoeuvre on a 7,000 kg plane would be over engineered in case the maximum weight of the aircraft for a 10G manoeuvre is only 6,000 kg. The entire mainwing spar and/or its joint with the fuselage can be made a little lighter for a lighter maximum weight in the fuselage.

That "lighter fuselage weight" could be by shaving off some weight from an over engineered landing gear and that leads to the possibility of shaving off even more weight from over engineered wing spars that no longer need to fly with as heavy a weight as they were originally engineered for.

Gotcha...May be I could talk to some of my colleagues who work on wing spars and see what are the possibilities in this direction.

But above is a much bigger effort. Its almost like re-assessment of entire structural design of the aircraft. And it will alter weight distribution, if we consider this resulting in shaving of 500kg material from a lot of places. It will take lot of time. Its upto the program managers will need to take a call whether the time and efforts are worth the gain from such endeavor. I doubt this is on the cards for MK1A as this could easily spiral into too large design change. But then its just my opinion.

One more silly point came to my mind just now. It looks like MK1 will be +8G fighter after all. From my understanding, this is aerodynamics-propulsion related limitation and not the structural limitation and as such the entire structure must be designed for 9G max nominal load from starting. So could downsizing entire structure to 8G result in some more saving?? If anyway it boils down to re-assessment of entire structure, why not include this into it as well?? On the other hand, if the resulting MK1A is expected to fulfill 9G requirement then this particular point is mute.

maitya · Post by **maitya** » 01 Oct 2015 16:18

shiv wrote:
nileshjr wrote:
What i meant is the support structures are already designed for much higher loads than what manoeuvrings loads of MLG would induced on them. Impact load at landing which is far higher than any load MLG could induce at 9G, will be the criteria deciding support structure's design and weight. So reducing MLG weight does not result in any (or perhaps any significant) weight saving in support structures.

I talked to a friend who was leading structural analysis project for MLG and its supporting structures for one of the Airbus Airliners. He corroborated my logic saying for airliners they never even considered manoeuvrings loads on MLG
<snip>
So unless there is any change in Max allowed Landing weight, there will be no redesign of support structures and even otherwise I do not think there will be reduction by "sevaral kgs on support structures per kg reduction in MLG weight".

No no no no. You and I are talking about two completely different things. I am not talking about landing stresses on the landing gear and support structures at all. There may be scope for weight reduction in other areas as a consequence of landing gear weight reduction, which I will explain.

If you ignore fuselage lift and consider the wings as the only (or main) lifting surfaces, those wings are attached to the fuselage by spars while the fuselage itself acts as a deadweight. On the ground the spars support the weight of the wings acting through the spar/s. In flight those same spars support and lift the deadweight of the fuselage. The wings are lifted up (by aerodynamic lift in flight) and that lift is transmitted via the main spar/s to lift the dead weight of the fuselage. Under high G circumstances (in all aircraft) the wings are trying to tear themselves off the fuselage, but they do not tear off because the spar/s are strong enough to remain attached to and support the fuselage at the point that they are attached to the fuselage. The heavier the fuselage, the greater the stress on the fuselage-mainwing spar/s joint in flight and high G stresses are correspondingly greater.

The lighter you make the fuselage - the less the stress on the fuselage-spar joint and the spars themselves during flight. Any weight reduction of the fuselage - be it main gear or anything else would lead to a corresponding decrease in the stresses on the main spar and spar-fuselage joint. A main wing spar that is strong enough for a 10 G manoeuvre on a 7,000 kg plane would be over engineered in case the maximum weight of the aircraft for a 10G manoeuvre is only 6,000 kg. The entire mainwing spar and/or its joint with the fuselage can be made a little lighter for a lighter maximum weight in the fuselage.

That "lighter fuselage weight" could be by shaving off some weight from an over engineered landing gear and that leads to the possibility of shaving off even more weight from over engineered wing spars that no longer need to fly with as heavy a weight as they were originally engineered for.

Aha!! Spars, Fuselage, Wing-sections ityadi ityadi is it? Time to bring out the hand-created collage of my unfinished anal-ysis of LCA structure etc, a few months back.
(the 80% complete write-up will not see daylight, as this one of those started-but-never-completed-writeups that gets accumulated in the hdd (periodidcally, until the next hdd crash

).

Anyway here it's ... I-beams and what not of Yell-Cee-Aaa's wing-boxes etc.

Anyway, pls carry on ... nileshjr, you are spot on, all these talk of 1K weight-loss looks to be hog-wash leading IAF on another garden-path (believe me I'll be the happiest person if I get proven wrong, and forced to eat my words above).

It's not very difficult to do an estimate of the LG weight (there are various approximate stats tool available for it - stuff like landing gear length etc - similar to the Wing weight estimation done in the above-never-bought-online write-up mentioned above).

shiv · Post by **shiv** » 01 Oct 2015 16:34

nileshjr wrote: But above is a much bigger effort. Its almost like re-assessment of entire structural design of the aircraft.

It does sound like more hot air than what is achievable with moderate effort. As Maitya says - if they can do it all of us will be thrilled

A Deshmukh · Post by **A Deshmukh** » 01 Oct 2015 17:16

15% weight reduction requires significant redesign efforts including flight laws and re-certification.
HAL cannot do it alone.

Austin · Post by **Austin** » 01 Oct 2015 17:31

Saurav Jha ‏@SJha1618 Sep 30

Uttam AESA is expected to be ready for airborne testing soon. Ground based testing has delivered encouraging results.

There'll be no IOC/ FOC campaign per se for the Mk-1A. The improvements will be made concurrently with the production process.

To attain that 400 figure a parallel line in the private sector is a must. This is being resisted by you know who.

IAF requirement for LCAs of different configurations is 400. This is the number people are talking about now.

All stakeholders are onboard with the Mk-1A configuration. Broad improvements: Uttam AESA, maintainability improvements, MAWS, DFCC Mk-2 etc