LCA: News & Discussions - October 2016

JayS · Post by **JayS** » 15 Nov 2016 19:38

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

As I pointed out previously in one post - its Hybrid analogue - digital FCS.

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

Page 3 -

Internal connections arrangement is directly related to system hybrid design - Analogue processing in each channel, comparison and digital active selection, digital gains and analogue input on servo control.

The other reference you quoted also says:

Digital transmission is the only way to handle the
amount of data which must be passed around such an
active flight-control system. This is done by an Electronique
Marcel Dassault/Sagem 2084 digital computer and
a back-up USG Type 284. French engineers use the designation
Digibus for the main data highway network around
which the information travels from one part of the avionics
system to another.

To my untrained mind, Looks like the main number crunching processor is analogue only. The data transmission, selection (selecting input from one of the channels by the way of averaging or majority voting) and gains are digital. The control system for servo motors of the control surfaces are also Analogue. This for only the original Mirage-2000. Perhaps for Dash-five version they went full digital. Not sure, but I doubt that.

Indranil · Post by **Indranil** » 15 Nov 2016 23:26

Something very interesting has come up on Tejas's FB page.

Hot refueling is the process of fueling the aircraft while engine is on run. This has been a mandatory requirement for LCA naval prototypes. This helps in executing the carrier suitability test points in a continuous phase. This process seems simpler in paper. The team has taken enormous effort in modifying the existing system, certifying it and then demonstrating it. The end result has been quite promising and there were occasions where the test points were bulit up satisfactorily to the desired value keeping all test parameters almost constant.

Jai Hind..

#TejasOfficialArchive #Tejas_LCA #NFTC #IADN

Please share the Post only with the Tags and Write Up. Kindly do not Edit or Copy this Photo. Copyright: #ADA

LCA Navy (LSPs) will be capable of hot-refueling as it is required for covering a variety of tests. It is plumbed specially for the same. Tejas won't have hot-refueling capability. IAF doesn't want or need it either.

P.S. Although, this is just primer, why the hell don't they paint all Tejas's in this colour scheme?

Kartik · Post by **Kartik** » 16 Nov 2016 01:37

tsarkar wrote: 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.

Well, I agree that HAL may have just saved the Tejas' future by insisting that the IAF agree on an intermediate Mk1A variant. They wanted no gap in production and the IAF didn't want the Mk1 beyond 40 orders, so something had to slot in between the time the Mk2 entered production and Mk1 orders were finished.

But what Indranil had mentioned earlier was that they were not that keen on the Mk2 variant, whereas ADA wanted to focus on the Mk2 variant. Maybe they're overloaded and they felt that the re-design of sub-systems will be too much for them in addition to the Mk1A work. Anyway, if the Mk2 variant is sanctioned and HAL and IAF are on board supporting it as well, I'm going to be a very very happy person. I just hope they don't increase the scope too much and consequently push the induction into the late 2020s.

Somehow, I just feel that the Tejas Mk2 is the actual perfect Tejas variant. The additional payload, the additional range, the internal EW suite, the aerodynamic refinements. It just sets everything as close to right as can get, with all that ADA and HAL know about the Tejas after all these years of testing.

Indranil · Post by **Indranil** » 16 Nov 2016 02:13

Very much true. The true potential of Tejas will only come to fruition in the Mk2.

Khalsa · Post by **Khalsa** » 16 Nov 2016 04:43

so without pointing me to posts and reposts can someone (out of the gurus) tell if

Mk2 is a go i.e the design and the prototypes phase/ part ?

Also ... will there be a TD or LSP for Mk1A ?

Indranil · Post by **Indranil** » 16 Nov 2016 05:27

Khalsa wrote: Mk2 is a go i.e the design and the prototypes phase/ part ?

Yes.

Khalsa wrote: Also ... will there be a TD or LSP for Mk1A ?

No TD. I don't know what will they call them LSP/SP, but they will roll off the Mk1 assembly line.

hanumadu · Post by **hanumadu** » 16 Nov 2016 09:26

Can HAL do the FBW for mk1A or does ADA has to step in?

JayS · Post by **JayS** » 16 Nov 2016 10:29

hanumadu wrote:Can HAL do the FBW for mk1A or does ADA has to step in?

You mean modification for Flight control system for MK1A?? HAL won't be doing it. ADA would own the whole system design but actually ADE has done the FCS. So they would be doing the modifications.

ks_sachin · Post by **ks_sachin** » 16 Nov 2016 11:30

JayS

Based on the proposed changes for mk1a what are the kind of changes in the FCS do you forsee.

Cheers

JayS · Post by **JayS** » 16 Nov 2016 12:06

I am not an expert on avionics, but my assessment is: - The only two major things that are added over and above the FOC config are - AESA radar and SPJ. This should have minimal effect (some fine tuning for additional radar weight if needed and in weapons load config with SPJ added) of the basic FBW flight control system of the aircraft. I have LCA avionics architecture schematic somewhere. Will post it later. But if you check the M2K systems image by tsarkar saar on last page which is very similar, you can figure out which components will have changes due to addition of new Radar and SPJ integration work, such as mission computer, the part which controls MFD displays, sensor fusion, weapons load system etc. Its a significant itvity work but not necessarily difficult given HAL's experience with SPJ integration and existing work with 2032 which should be quite similar in architecture to 2052.

maitya · Post by **maitya** » 16 Nov 2016 12:43

^^ I don;t think there'll be any need of any FCS changes for the MK1A - it's mostly avionics-only "upgrade" over MK1 (and also some degree of internal systems arrangement for better turn-around time etc).

However, if HAL pulls-off, some serious weight savings in the range of say >500K etc, which I seriously doubt, then there may be some tweaking required . After all, if adding IFR for the MK1-FOC version is not requiring any FCS change etc, then I don't think of any such things will be required for Mk1A.

But I think the gradual opening of the AoA etc is going on (26 already achieved but not implemented on operational versions etc), maybe different weapon/payload configurations etc, which may require some newer versions of FCS being added (but then that's not a wholesale FCS change etc - these are upgrades, which will be there every now and then).

amit · Post by **amit** » 16 Nov 2016 12:48

I'd like to ask some gurus here the veracity of something I remember reading sometime ago, that is when MK2 starts flying it will start in IOC configuration? Meaning that it can move straight towards FOC? Is this correct? If so, based on the learning for MK1 and MK1A the timeline should be shorter for FOC?

Pratyush · Post by **Pratyush** » 16 Nov 2016 13:00

Simplistically the mk1a is a mk2 minus the levcon. So as soon as the airframe is declared airworthy. The same can be put in production no issues.

JayS · Post by **JayS** » 16 Nov 2016 15:56

maitya wrote:^^ I don;t think there'll be any need of any FCS changes for the MK1A - it's mostly avionics-only "upgrade" over MK1 (and also some degree of internal systems arrangement for better turn-around time etc).

However, if HAL pulls-off, some serious weight savings in the range of say >500K etc, which I seriously doubt, then there may be some tweaking required . After all, if adding IFR for the MK1-FOC version is not requiring any FCS change etc, then I don't think of any such things will be required for Mk1A.

But I think the gradual opening of the AoA etc is going on (26 already achieved but not implemented on operational versions etc), maybe different weapon/payload configurations etc, which may require some newer versions of FCS being added (but then that's not a wholesale FCS change etc - these are upgrades, which will be there every now and then).

I think there is some changes needed for IFR in FCS. Vaguely remember to have read somewhere that during IFR the FCS switches to alpha-command from the normal g-command. Though its a small change.

Dileep · Post by **Dileep** » 16 Nov 2016 18:58

MK1A speculations? Wait till AI17 to see for yourself.

tsarkar · Post by **tsarkar** » 16 Nov 2016 19:27

Mk1 IOC - under production
Mk 1 FOC - under development. Production to be completed 2020
Mk 1A - As the name suggests, Standard of Preparation SoP 2018 development expected to be completed 2018. Production 2020-2025/6
Mk 2 - Full time development can start 2018 with production tentatively starting from 2025-26.

Mk1A with 2052, Derby, Python & Litening is more than enough for F-16/J-10/Su-27 copies.

Agree with posters that single engine RFP might be great for Make in India but not offer any transformational capabilities over Tejas or those already in inventory, unless F-35 is offered.

Other Make in India can be the technical winners of MMRCA - Rafale or Eurofighter.

However, given how Apache fuselage Made in India is generating additional Apache orders, the government of the day might push F-16 through

Rishi Verma · Post by **Rishi Verma** » 16 Nov 2016 19:37

Pratyush wrote:Simplistically the mk1a is a mk2 minus the levcon and 414 engine . So as soon as the modification in airframe is declared airworthy. The same can be put in production no issues.

JayS · Post by **JayS** » 16 Nov 2016 20:32

Rishi Verma wrote:
Pratyush wrote:Simplistically the mk1a is a mk2 minus the levcon and 414 engine . So as soon as the modification in airframe is declared airworthy. The same can be put in production no issues.

Plus
- Fuselage plug 0.5m
- slightly taller tail
- internal EW
- additional internal fuel
- improved shape near cockpit/canopy

Also I expect general optimization in Airframe so we should either see a life of 6000-8000hr or lighter airframe for same life. Would be awesome if they could implement co-cured wing structure. That would be ground-breaking.

Sid · Post by **Sid** » 16 Nov 2016 20:50

Dileep wrote:MK1A speculations? Wait till AI17 to see for yourself.

Sir ji, if you can spill out some teeny weeny stuff then it will be a new year gift for everyone here.

hanumadu · Post by **hanumadu** » 16 Nov 2016 21:59

JayS wrote:
hanumadu wrote:Can HAL do the FBW for mk1A or does ADA has to step in?
You mean modification for Flight control system for MK1A?? HAL won't be doing it. ADA would own the whole system design but actually ADE has done the FCS. So they would be doing the modifications.

Yes, Flight Control System. Thanks.

Kartik · Post by **Kartik** » 17 Nov 2016 00:31

Pratyush wrote:Simplistically the mk1a is a mk2 minus the levcon. So as soon as the airframe is declared airworthy. The same can be put in production no issues.

The IAF Tejas Mk2 variant never featured LEVCONs. And so the description is incorrect, especially so since you missed out the most important upgrade- the engine.

Simplistically, the Mk1A is a Mk1 with AESA and SPJ and parts and LRUs moved around to help accessibility and reduce turn around times.

nachiket · Post by **nachiket** » 17 Nov 2016 00:37

Kartik wrote: Simplistically, the Mk1A is a Mk1 with AESA and SPJ and parts and LRUs moved around to help accessibility and reduce turn around times.

And the weight reduction that HAL claims it can carry out.

JTull · Post by **JTull** » 17 Nov 2016 00:44

I'd prefer to see progress on Mk1A. Without that Mk2 is a pipe dream. Despite different agencies leading the efforts, HAL will still be manufacturing most of the Mk2 components. How can ADA do this in isolation without learning from the issues faced in Mk1A or with Mk1 manufacturing.

Marten · Post by **Marten** » 17 Nov 2016 01:03

I don't think ADA and HAL are as separate and exclusive as we think they are. A lot of cross-pollination and collaboration has happened in the past, and am sure if happening now as well. Perhaps someone in the know can confirm? HAL remains the builder and will guide future efforts in making Mk2 production friendly (given that the SOP for Mk2 will already refer the final SOP for Mk1A).

Kartik · Post by **Kartik** » 17 Nov 2016 01:21

nachiket wrote:
Kartik wrote: Simplistically, the Mk1A is a Mk1 with AESA and SPJ and parts and LRUs moved around to help accessibility and reduce turn around times.
And the weight reduction that HAL claims it can carry out.

There isn't going to be any weight reduction on the Mk1A.

link

The new LCA-MkI-P variant with the EW Package will also add some 50 kilos of more weight, but then, Mr Raju explained, the capability of the aircraft increases significantly, offsetting the disadvantage of a smaller engine.
The current LCA-MkI version uses 210 kilos with ballast in the nose to stabilize the aircraft. This will be removed, and the AESA and EW suite weighing about 250 kilos will be added. The net weight gain will be of about 50 kilos.

And it is clear that while there is extensive collaboration between ADA, HAL and other DRDO labs, the lack of the production agency being the agency fully in charge is being felt.

For one thing, it is proposing now to take full charge of the LCA development programme to become the single responsible agency. Right now, the design and development of the aircraft, engines, weapons package etc, are with DRDO and its Aeronautical Development Agency (ADA).

Indranil · Post by **Indranil** » 17 Nov 2016 02:05

JayS wrote:
hanumadu wrote:Can HAL do the FBW for mk1A or does ADA has to step in?
You mean modification for Flight control system for MK1A?? HAL won't be doing it. ADA would own the whole system design but actually ADE has done the FCS. So they would be doing the modifications.

Has far as I know, NAL (Chetty et al.) developed the control laws. ADE developed the simulator. IFR is part of FOC, and the first flight is impending shortly. AFAIK the hold up is not with flight controls but instrumentation and obtaining clearance to fly. I agree with Maitya, the changes to flight control system is more likely to be parametric, if the empty weight doesn't change much. I am pretty sure they will keep the CG where it is and the control surfaces are going to stay the same.

vina · Post by **vina** » 17 Nov 2016 10:07

JayS wrote:I think there is some changes needed for IFR in FCS. Vaguely remember to have read somewhere that during IFR the FCS switches to alpha-command from the normal g-command. Though its a small change.

I am not sure if that is a change at all . In fact, most aircraft at slow speeds would shift to alpha demand mode , while the normal mode of the FCS would be the G demand mode (with envelope protection).

In fact, from this web site, (great website on the M2K I should say), the Mirage 2000 switches to the alpha demand mode to g demand mode transition happens at approx 245 kts.

Now for air to air refuelling, you need the planes to be flying level , and straight, and not with Nose in the air and Mushrraf pointing to the ground. So the stall speed too would be quite high , of the order of 400 knots ( at approx 25K to 30K ft) for fast jets with the flaps and stuff in normal cruise position with some 20 knots or so margin over stall speed. The tanker would be cruising quite fast and level.. So I guess you are right . The FCS would probably be need to revert to the alpha mode to make sure that it remains within the the refuelling cruise envelope in terms of speed and angle of attack. I wonder how they do that. Maybe a switch somewhere the pilot pushes which tells the FCS to switch ? Otherwise how will it know whether it is cruising normally or in refuelling mode and to transition to the alpha demand mode.

And from what I can see from the Mirage website I posted, the Tejas will need to be certified to around 29 deg angle of attack for the full 9G limit the structure is capable of to be realised. That 9G is not a priority now, and can come later via software upgrades.

JayS · Post by **JayS** » 17 Nov 2016 11:49

vina wrote:
JayS wrote:I think there is some changes needed for IFR in FCS. Vaguely remember to have read somewhere that during IFR the FCS switches to alpha-command from the normal g-command. Though its a small change.
I am not sure if that is a change at all . In fact, most aircraft at slow speeds would shift to alpha demand mode , while the normal mode of the FCS would be the G demand mode (with envelope protection).

In fact, from this web site, (great website on the M2K I should say), the Mirage 2000 switches to the alpha demand mode to g demand mode transition happens at approx 245 kts.

Now for air to air refuelling, you need the planes to be flying level , and straight, and not with Nose in the air and Mushrraf pointing to the ground. So the stall speed too would be quite high , of the order of 400 knots ( at approx 25K to 30K ft) for fast jets with the flaps and stuff in normal cruise position with some 20 knots or so margin over stall speed. The tanker would be cruising quite fast and level.. So I guess you are right . The FCS would probably be need to revert to the alpha mode to make sure that it remains within the the refuelling cruise envelope in terms of speed and angle of attack. I wonder how they do that. Maybe a switch somewhere the pilot pushes which tells the FCS to switch ? Otherwise how will it know whether it is cruising normally or in refuelling mode and to transition to the alpha demand mode.

And from what I can see from the Mirage website I posted, the Tejas will need to be certified to around 29 deg angle of attack for the full 9G limit the structure is capable of to be realised. That 9G is not a priority now, and can come later via software upgrades.

I am not sure how the change would be done. I am not even sure if the change is needed in LCA specifically. Its just from what I know, it seems a small change is needed in general. Anyhow, could be asked to some ADA guy in coming AI2017.

What is the relation of 29deg AoA to 9G..?? Do we know LCA can't produce enough lift at 26deg for taking 9G turn..??

JayS · Post by **JayS** » 17 Nov 2016 12:06

Indranil wrote:
JayS wrote:
You mean modification for Flight control system for MK1A?? HAL won't be doing it. ADA would own the whole system design but actually ADE has done the FCS. So they would be doing the modifications.
Has far as I know, NAL (Chetty et al.) developed the control laws. ADE developed the simulator. IFR is part of FOC, and the first flight is impending shortly. AFAIK the hold up is not with flight controls but instrumentation and obtaining clearance to fly. I agree with Maitya, the changes to flight control system is more likely to be parametric, if the empty weight doesn't change much. I am pretty sure they will keep the CG where it is and the control surfaces are going to stay the same.

Control laws (mathematics) developed by NAL, but the flight control system is developed by ADE. ADE has the expertise in developing FCS for all sort of flying stuff and thus they got the Nirbhay as well, since its more like a UAV.

http://www.drdo.gov.in/drdo/labs/ADE/En ... asWork.jsp

Combat Aircraft Systems - TEJAS - Of the four complex state-of-the-art technologies of Tejas, one of them is digital fly-by-wire flight control system (DFBW-FCS). The nation�s first DFBW-FCS was realized by ADE and was on-board of the Tejas technology demonstrator aircraft during the maiden flight on 4th January 2001. The cockpit display suite and design and development of engineering test stations were also carried out by ADE.

JayS · Post by **JayS** » 17 Nov 2016 12:23

Indranil wrote:
JayS wrote:
You mean modification for Flight control system for MK1A?? HAL won't be doing it. ADA would own the whole system design but actually ADE has done the FCS. So they would be doing the modifications.
Has far as I know, NAL (Chetty et al.) developed the control laws. ADE developed the simulator. IFR is part of FOC, and the first flight is impending shortly. AFAIK the hold up is not with flight controls but instrumentation and obtaining clearance to fly. I agree with Maitya, the changes to flight control system is more likely to be parametric, if the empty weight doesn't change much. I am pretty sure they will keep the CG where it is and the control surfaces are going to stay the same.

I know IFR is part of FOC. Actually Maitya brought that point up, that IFR didn't need any changes in FCS. I am not sure if its needed specifically for LCA, but I expect some small changes needed to make handling better during IFR. Small changes, but changes nonetheless. I don't think anyone is saying the hold up for IFR is due to FCS. Actually I said the same thing, that there would be fine tuning of FCS at the most from MK1 to MK1A.

vina · Post by **vina** » 17 Nov 2016 12:41

JayS wrote:What is the relation of 29deg AoA to 9G..??

9G --> wings support 9 times weight of the plane. Bank angle has to be to 83.6 deg.. In that condition, the alpha has to increase to generate that lift.
Look at the Coeff of lift characteristics of low aspect ratio wings (like Deltas) at high angle of attack. here

Do we know LCA can't produce enough lift at 26deg for taking 9G turn..??

I would guess yes. As a good engineering practice, always look at analogs for data / design starting point. It cant be very different. If M2K does it at 29deg, the LCA cant be more than fraction of a percentage different and definitely cant be radically different like a 10% difference.

JTull · Post by **JTull** » 17 Nov 2016 15:06

Demolishing Some LCA Tejas Falsehoods

ShauryaT · Post by **ShauryaT** » 17 Nov 2016 15:19

JayS wrote:
Rishi Verma wrote:
Plus
- Fuselage plug 0.5m
- slightly taller tail
- internal EW
- additional internal fuel
- improved shape near cockpit/canopy

Also I expect general optimization in Airframe so we should either see a life of 6000-8000hr or lighter airframe for same life. Would be awesome if they could implement co-cured wing structure. That would be ground-breaking.

I think the big opportunistic capability to provide with Mk II is supercruise on the 414 engine. Some others to look for are TFR type capabilities to enable this aircraft for strike. Its our platform and we should evolve it aggressively. Its improved T:W ratios apart from improvements in aero dynamics should allow for more payload in certain configurations, with some frame strengthening.

JayS · Post by **JayS** » 17 Nov 2016 15:52

JTull wrote:Demolishing Some LCA Tejas Falsehoods

Excellent article. Should be shared as much as possible, so more and more people would read it and understand the situation.

tsarkar · Post by **tsarkar** » 17 Nov 2016 16:26

The state of readiness & timeliness of the F-35 http://aviationweek.com/site-files/avia ... 35memo.pdf

brar_w · Post by **brar_w** » 17 Nov 2016 17:04

tsarkar wrote:The state of readiness & timeliness of the F-35 http://aviationweek.com/site-files/avia ... 35memo.pdf

viewtopic.php?f=3&t=5098&p=2076072#p2076072

Vashishtha · Post by **Vashishtha** » 17 Nov 2016 20:38

Is the pic of LCA Navy in camo on brf fb page real or photoshopped?

JTull · Post by **JTull** » 17 Nov 2016 21:01

ShauryaT wrote:I think the big opportunistic capability to provide with Mk II is supercruise on the 414 engine. Some others to look for are TFR type capabilities to enable this aircraft for strike. Its our platform and we should evolve it aggressively. Its improved T:W ratios apart from improvements in aero dynamics should allow for more payload in certain configurations, with some frame strengthening.

Undertaking aero optimisation on MK2 for supercruise would be a good step before AMCA. Otherwise we may again have too ambitious a goal of achieving all key 5th Gen techs in a single step.

disha · Post by **disha** » 18 Nov 2016 01:45

JTull wrote:Demolishing Some LCA Tejas Falsehoods

Excellent article., particularly the words describing the calculations on jet turbine - simply bravo!

Indranil · Post by **Indranil** » 18 Nov 2016 03:02

ShauryaT wrote:I think the big opportunistic capability to provide with Mk II is supercruise on the 414 engine.

JTull wrote:Undertaking aero optimisation on MK2 for supercruise would be a good step before AMCA.

Mk2 is not supposed to supercruise.

Vashishtha wrote:Is the pic of LCA Navy in camo on brf fb page real or photoshopped?

It is definitely real. It is not a camo. Actually, it is in primer. Not painted yet.

JayS, thanks for the clarification on the ADE/NAL contribution.

Vina, they can attain 9G at 26 degrees (and even lower). They would enter the turn faster. The 8G limit is not due to AoA. Thanks for the info on the Mirage though. Learnt something new from that article.

Mk1A picture will get much clearer at AI17. I am also waiting for more information on the combat hawk.