LCA news and discussion

shiv · Post by **shiv** » 08 Jul 2009 08:28

Rivets and screws hold things down. If one screw is loose the RCS is not increased merely by the loose screw, but by the fact that the thing that is supposed to be held down is now sticking out above the surface of whatever it was supposed to lie flush with.

rajsunder · Post by **rajsunder** » 08 Jul 2009 09:35

p_saggu wrote:The thing about rivets is that we can't use these on the MCA. Stealth is not compatible with so many rivets around. Just look at the smooth skins of the F-35, almost no rivets! Even the other 4th gen western aircraft, boast of much smoother and streamlined outer structures than Russian or other aircraft.
I remember reading about how on the F-117 there was an incidence where one screw was slightly unscrewed, it increased the RCS by several factors.

JSF has rivet's, but i think the top layer of JSF is covered by some radar absorbing covering.

check

http://www.youtube.com/watch?v=1kNszWU7hTw

this is a 2hr program by PBS about JSF program

andy B · Post by **andy B** » 08 Jul 2009 10:00

p_saggu wrote:The thing about rivets is that we can't use these on the MCA. Stealth is not compatible with so many rivets around. Just look at the smooth skins of the F-35, almost no rivets! Even the other 4th gen western aircraft, boast of much smoother and streamlined outer structures than Russian or other aircraft.
I remember reading about how on the F-117 there was an incidence where one screw was slightly unscrewed, it increased the RCS by several factors.

Saggu ji, all "stealth" aircraft have a another layer of "skin on the skin" which fit flush (I know for sure the Raptor has it) and I believe the B-2 and the JSF also have the same concept. This is the main maintainence problem with these platforms in that you not only have to fir the panels properly but also ensure that these tiles fit in flush to ensure the stealth.

The other 4th gen ac would be looking smooth bcoz of the stealth coating

vardhank · Post by **vardhank** » 08 Jul 2009 14:28

Sorry, been off this for a bit.
Two questions:
1) If indeed we need to go for the GE 414 or Ej2000, do you think it will require substantial redesign of the LCA? If that is the case, how many years does that set us back?
2) MCA-related, not LCA. Just came across the wind-tunnel model shown at AI09 - do you think this shape will stay? And more important, why the entirely new wing shape? IIRC, the ADA had said they'd like to stick to the LCA's wing shape, which they understood well.

krishnan · Post by **krishnan** » 08 Jul 2009 15:50

As you people debate about rivets and all LCA completes another 6 flight tests

Gaur · Post by **Gaur** » 08 Jul 2009 16:57

vardhank wrote: 1) If indeed we need to go for the GE 414 or Ej2000, do you think it will require substantial redesign of the LCA? If that is the case, how many years does that set us back?

It is said that Ej2000 will require less time than ge414. Though how much any selected engine would take is anyone's guess. My guess is no sooner than 3 years (though I am no expert), and that is me being optimistic. After the engine is installed, there would need to be substantial flight testing all over again which takes time.

vardhank wrote:
2) MCA-related, not LCA. Just came across the wind-tunnel model shown at AI09 - do you think this shape will stay? And more important, why the entirely new wing shape? IIRC, the ADA had said they'd like to stick to the LCA's wing shape, which they understood well.

Will the shape stay? If past a/c developments are anything to go by, there are always substantial differences between wind tunnel model and final a/c. It is only natural. Why new wing shape? Because it is a stealth a/c not a 4th gen plane. I would suggest you do some research before you ask questions here. There are particular reasons for the unique shapes of stealth a/cs. Please do some basic reading. In the short time that I have been here, one thing I have learned is that spoon feeding is not encouraged here.

PratikDas · Post by **PratikDas** » 08 Jul 2009 20:54

krishnan wrote:As you people debate about rivets and all LCA completes another 6 flight tests

Since no one seems to have a clue what all these flights are for we might as well debate rivets. I suggest we debate tyres next week.

Rahul M · Post by **Rahul M** » 08 Jul 2009 21:04

rakall · Post by **rakall** » 08 Jul 2009 21:13

PratikDas wrote:
krishnan wrote:As you people debate about rivets and all LCA completes another 6 flight tests
Since no one seems to have a clue what all these flights are for we might as well debate rivets. I suggest we debate tyres next week.

Who knows what might be going on.. After AI09 we were wondering why there was no news of any weapon trials - just the same old "LCA-Tejas finsihed 2more sorties" kind of updates on flight testing news..

And then we come to know in June that weapon trials including heavy stores dropping was finsihed as way back as Feb25-17Mar.. Cunning Yindoos are doing things secretively..

Meanwhile lets openly trash LCA's rivets, tyres, shoddy paint job, tangled wires and what not..

KrishG · Post by **KrishG** » 08 Jul 2009 21:25

PratikDas wrote:
krishnan wrote:As you people debate about rivets and all LCA completes another 6 flight tests
Since no one seems to have a clue what all these flights are for we might as well debate rivets. I suggest we debate tyres next week.

"Coming to think of it, the Tejas logo is of a very unattractive font, 'Tejas' written in Italics. It doesn't seem to reflect modern fashion!! the font should be fiery and nit boring!"
-A detailed analysis of the font of the logo of Tejas

k prasad · Post by **k prasad** » 08 Jul 2009 23:23

KrishG wrote:
PratikDas wrote: Since no one seems to have a clue what all these flights are for we might as well debate rivets. I suggest we debate tyres next week.
"Coming to think of it, the Tejas logo is of a very unattractive font, 'Tejas' written in Italics. It doesn't seem to reflect modern fashion!! the font should be fiery and nit boring!"
-A detailed analysis of the font of the logo of Tejas

And that Tejas logo should be in RF reflective paint, so that even the enemy should be able to read it from his radar and shake in his cockpit.

aditp · Post by **aditp** » 08 Jul 2009 23:54

Italians are in power my boy, italians are in power.

Samay · Post by **Samay** » 09 Jul 2009 00:34

aditp wrote:Italians are in power my boy, italians are in power.

so are the pakis

dorai · Post by **dorai** » 09 Jul 2009 02:42

To be serious for a moment... Tejas does not have composite material where those rivets he is talking about is located. The (forward) centre fuselage has almost no composite and what you see on the front is thin metal sheets bolted over the metal frame like a skin so they need to use several rivet lines to make the "skin" tightly follow the frame. Inside that frame is flight equipment and other components that you obviously will not find in the big composite sections like in the wings. If you're more custom to PC-terms it's like a empty tower case that you insert all what you need then bolt on the cover except for a few panels that need to always be accessable from the outside.

You can see the fin in that same photo. It is almost all composite and it has almost no rivet lines. It's also not unlikely that there will be larger metal sheets and fever rivet lines on production models.

shiv · Post by **shiv** » 09 Jul 2009 06:32

rakall wrote:
Meanwhile lets openly trash LCA's rivets, tyres, shoddy paint job, tangled wires and what not..

It's all those bloody chappal wearing diabetics...

p_saggu · Post by **p_saggu** » 09 Jul 2009 07:41

The tail piece ( N^3's L'verticale fin from the international aviation thread

), and the two delta wings are all composite. Also the numerous flaps, and panels on the fuselage are composite. The rest is mostly metal.

andy B · Post by **andy B** » 09 Jul 2009 07:43

^^^ Ya'allah after reading N^3's and Vina's french discussions on airbus I m gonna make sure I knock meself out with some good ol's scotch onlee the next time I am flying in an airbus...

krishnan · Post by **krishnan** » 09 Jul 2009 11:06

Talking about tyres, are LCA's tyres imported or made in india

k prasad · Post by **k prasad** » 09 Jul 2009 18:52

krishnan wrote:Talking about tyres, are LCA's tyres imported or made in india

Good old MRF onlee sirjee, maintained and repaired by Iyengar's and Sons!!

Drevin · Post by **Drevin** » 09 Jul 2009 19:02

^^^ Ya'allah after reading N^3's and Vina's french discussions on airbus I m gonna make sure I knock meself out with some good ol's scotch onlee the next time I am flying in an airbus...

Also the non-booze analogy of this; its more comfortable going on long-term projects to UK than mainland europe(for those in s/w profession and those who are lucky and whatnot) ....what with the language problems. just a feeling, but I am sure there are exceptions.

Since no one seems to have a clue what all these flights are for we might as well debate rivets. I suggest we debate tyres next week.

nice one pratik.

that damn pv5 needs to fly

shiv · Post by **shiv** » 09 Jul 2009 19:24

Drevin wrote: nice one pratik. that damn pv5 needs to fly

Weather in Bangalore
http://www.wunderground.com/global/stations/43295.html

Drevin · Post by **Drevin** » 09 Jul 2009 19:27

shiv wrote:
Drevin wrote: nice one pratik. that damn pv5 needs to fly
Weather in Bangalore
http://www.wunderground.com/global/stations/43295.html

Ah ok. So its ready to fly

Kartik · Post by **Kartik** » 10 Jul 2009 00:58

dorai wrote:To be serious for a moment... Tejas does not have composite material where those rivets he is talking about is located. The (forward) centre fuselage has almost no composite and what you see on the front is thin metal sheets bolted over the metal frame like a skin so they need to use several rivet lines to make the "skin" tightly follow the frame. Inside that frame is flight equipment and other components that you obviously will not find in the big composite sections like in the wings. If you're more custom to PC-terms it's like a empty tower case that you insert all what you need then bolt on the cover except for a few panels that need to always be accessable from the outside.

You can see the fin in that same photo. It is almost all composite and it has almost no rivet lines. It's also not unlikely that there will be larger metal sheets and fever rivet lines on production models.

wrong. those are not "thin metal sheet" or metallic panels, but composite panels, to be more specific, carbon fiber composite panels. they have tape or fabrics that are placed above and below an aramid honeycomb core, and these panels are bolted on to the underlying frames at what is called an "edgeband". whether those panels are access panels or not is immaterial to their being made of composites or metals.

the fin is considerably smoother because its built as a single piece with the main load carrying member, the torsion box being co-cured, and the skin panels are co-bonded to the underlying structural members.
you can read up more on it here.

dorai · Post by **dorai** » 10 Jul 2009 11:02

Kartik so can you post a source for your first paragraph that it is composite where the rivet lines go over since that doesn't really make any sense at all since there's no honeycomb structure underneat. If that had been the case they would also have been fixated with a chemical compound as there is absolutely no reason to use rivets. The access doors at the nose is of composite structure though.

Neela · Post by **Neela** » 10 Jul 2009 12:03

So then, finally a chance to repost my query.

Earlier there was this discussion about the dumb bombs being dropped and how the external parameters, speed etc are used to calculate the release point.
My question : as the bomb drops down, wind speeds could be different at different altitudes. How is this factored in, if at all.

krishnan · Post by **krishnan** » 10 Jul 2009 12:06

AFAIK , a particular bum is dropped from a certain height and certain speed. I could be wrong though and would be glad to be corrected.

geeth · Post by **geeth** » 10 Jul 2009 14:59

>>>My question : as the bomb drops down, wind speeds could be different at different altitudes. How is this factored in, if at all.

The answer to your question is simple - there is no way you can control the dumb bomb after it is released - if the values of the parameters factored in are different from ambient values, the bomb will not hit the bulls eye. The more the difference in values, the more the deviation. That is why these bombs are larger in size. Vice verse, more accurate bombs can be smaller in size for the same collateral damage.

Kakarat · Post by **Kakarat** » 10 Jul 2009 16:47

dorai wrote:Kartik so can you post a source for your first paragraph that it is composite where the rivet lines go over since that doesn't really make any sense at all since there's no honeycomb structure underneat. If that had been the case they would also have been fixated with a chemical compound as there is absolutely no reason to use rivets. The access doors at the nose is of composite structure though.

What Honeycomb structure? screws and rivets are better then chemical compound for fixation when a lot of stresses are involved like in the case of aircraft.

Philip · Post by **Philip** » 10 Jul 2009 17:41

Interesting report in a recent AWST,pic enclosed,is that the Lockheed Skunkworks designed and built the latest ACCT (advanced composite commercial transport) aircraft,a modified Dornier 328 jet,which had a larger redesigned rear fuselage,using extensive composites,which did not need autoclave manufacturing processes.The number of fasteners was dramatically reduced in the thousands by the use of larger structural memebers,etc.The most interesting feat was that the entire time taken for design and first flight took only 18 months! This is a fantastic feat and our ADA should take note.

NRao · Post by **NRao** » 10 Jul 2009 17:58

Philip wrote:Interesting report in a recent AWST,pic enclosed,is that the Lockheed Skunkworks designed and built the latest ACCT (advanced composite commercial transport) aircraft,a modified Dornier 328 jet,which had a larger redesigned rear fuselage,using extensive composites,which did not need autoclave manufacturing processes.The number of fasteners was dramatically reduced in the thousands by the use of larger structural memebers,etc.The most interesting feat was that the entire time taken for design and first flight took only 18 months! This is a fantastic feat and our ADA should take note.

Yeah. That takes a LOT of parallel R&D. The idea being that a LOT of ideas will be total waste, and, the few ideas that get through will produce something and fewer will produce something worthwhile. Needs a ton of funds. And, not to mention mentality to do get to such products.

India I an afraid has sunk into importing technologies - with the economy going gung ho they can afford to pay for such things.

Here is the AC:
http://www.af.mil/shared/media/photodb/ ... 4L-108.jpg
http://www.af.mil/shared/media/photodb/ ... 4L-115.jpg
http://www.af.mil/shared/media/photodb/ ... 4U-152.jpg

ajay_hk · Post by **ajay_hk** » 12 Jul 2009 02:10

Tejas may skip operational clearance deadline
Ravi Sharma

Highly placed sources told The Hindu that the software integration of crucial equipment like the Israeli-built multimode radar (MMR) with the aircraft was yet to be completed. The lack of a radar meant that crucial points on the flight envelope were yet to be tested.

The ADA has still not provided HAL with the digital flight control computer and air data computers which have to be integrated into the LCA programme’s Limited Series Production 3 (LSP3) aircraft. The new LSP3, which was scheduled to make its first flight in June 2008, is now expected to do so only in September.

Both the IAF and the ADA have bemoaned the low sortie generation by HAL. Just 11 sorties were undertaken in April, 24 in May and 23 in June. Officials claim that a minimum run rate of 30 sorties a month is required to meet the present IOC deadline. With this in mind, a plan to prepare two aircraft for flying in the forenoon and one in the afternoon was worked out. But this has not fructified.

HAL officials, however, deny that sortie generation is the primary reason behind the delays. “With two aircraft withdrawn from the flight test programme, we have just five aircraft to generate sorties,” said an official.

“And even the available aircraft are not fully fitted to undertake the flights that are required. We have even painted LSP3 in its new colour [grey] and are ready. LSP4 will have its ground run before the end of July and the fuselages for LSP5 and LSP6 are ready. On six occasions in June while the aircraft was prepared and the weather good, there were no pilots.”

Officials said the IAF was aware of the shortage of test pilots at the National Flight Test Centre (the LCA is flown exclusively by these pilots) and was looking to increase their number.

Kartik · Post by **Kartik** » 12 Jul 2009 22:40

dorai wrote:Kartik so can you post a source for your first paragraph that it is composite where the rivet lines go over since that doesn't really make any sense at all since there's no honeycomb structure underneat. If that had been the case they would also have been fixated with a chemical compound as there is absolutely no reason to use rivets. The access doors at the nose is of composite structure though.

Dorai, in most aircraft composite panels, the panel is built with a aramid honeycomb core, but the core drops off well before the rivet line..as in, at the center of the panel, there is a sandwich structure, composed of composite fabric or tape plies, and then the core and then again, the plies. towards the edge, the core actually ramps down to zero thickness, and the entire thickness is composed of what is called "laminate", meaning only plies of composite fabric or tape. it is in this region that the bolts or rivets are used at, meaning that no holes are drilled through a core (which would require a very heavy material, called potting compound to be used)..

a metallic panel of equivalent size is much heavier than a carbon fiber composite panel and would be the first thing designers would replace on an aircraft that has weight issues. it wouldn't make sense to have primary structural components like wing spars made of composites and secondary parts like panels made of metals. some composite panels are also built up as pure laminate panels, with no aramid core at all, especially if there are systems brackets, parts, etc. nearby which would not allow a thick aramid core to be used in that region.

Kartik · Post by **Kartik** » 15 Jul 2009 21:02

dorai wrote:Kartik so can you post a source for your first paragraph that it is composite where the rivet lines go over since that doesn't really make any sense at all since there's no honeycomb structure underneat. If that had been the case they would also have been fixated with a chemical compound as there is absolutely no reason to use rivets. The access doors at the nose is of composite structure though.

Dorai, apart from the fact that I have spoken to a very senior person once involved in the LCA program on composites, I went through my archives and found a pdf that had this image..

p_saggu · Post by **p_saggu** » 15 Jul 2009 21:17

Shouldn't this bird then be invisible to radar?

So on the MCA all that is needed is a shape which'll reduce the RCS and a possible RCS reduction coat of paint or layer!

There can be no comparision with an aluminium hulk reflecting radar signals all the way, and this small carbon baby. Way to go ADA!

SanjibGhosh · Post by **SanjibGhosh** » 16 Jul 2009 01:00

Full-fledged IAF fighter base likely in Kayathar

http://www.hindu.com/2009/07/16/stories ... 421800.htm

That, however, will soon change in view of the evolving geopolitical situation and the increasing strategic pertinence of the peninsula. “Sulur, to begin with, is going to be the country’s first Tejas LCA (Light Combat Aircraft) base and will be operational by the end of next year or the beginning of 2011. Despite hiccups pertaining to its engine, the aircraft should be a very potent platform,” the Air Marshal said.

Rahul M · Post by **Rahul M** » 16 Jul 2009 01:15

p_saggu wrote:Shouldn't this bird then be invisible to radar? So on the MCA all that is needed is a shape which'll reduce the RCS and a possible RCS reduction coat of paint or layer!

There can be no comparision with an aluminium hulk reflecting radar signals all the way, and this small carbon baby. Way to go ADA!

I'm not an expert but from what info we do have, composites are radar absorbent/transparent/reflective depending on the frequency (I've seen all 3 phenomena mentioned. EM gurus, is this related to skin depth ? I'm not aware of the exact EM property type of most composite materials). now even for freqn for which it is transparent, the internal instruments will be reflective, that would be an even bigger problem.

then there's the engine inlet. ^^ all this doesn't even mention the munitions and EFTs. you can guess what would happen when those are added.

my take : yes it will have low RCS by virtue of its size and materials but not VLO by any means.

Rahul M · Post by **Rahul M** » 16 Jul 2009 01:16

SanjibGhosh wrote:Full-fledged IAF fighter base likely in Kayathar

http://www.hindu.com/2009/07/16/stories ... 421800.htm
...

from this link :

Air Marshal S. Radhakrishnan, Air Officer Commanding-in-Chief of the Southern Naval Command

Samay · Post by **Samay** » 16 Jul 2009 03:22

p_saggu wrote:Shouldn't this bird then be invisible to radar? So on the MCA all that is needed is a shape which'll reduce the RCS and a possible RCS reduction coat of paint or layer!

There can be no comparision with an aluminium hulk reflecting radar signals all the way, and this small carbon baby. Way to go ADA!

Shape comes first,then the stealth coatings play a role, LCA's shape ,when it was designed in 80's was not for stealth purpose,but they will do so with the MCA,or perhaps with some changes in lcamk2.
ruskies claim to have an ongoing plasma stealth development,which could be used in pakfa.

p_saggu · Post by **p_saggu** » 16 Jul 2009 04:05

Wasn't the entire plasma stealth saga discredited as a bogey?

SSridhar · Post by **SSridhar** » 16 Jul 2009 07:39

Rahul M wrote:
SanjibGhosh wrote:Full-fledged IAF fighter base likely in Kayathar

http://www.hindu.com/2009/07/16/stories ... 421800.htm
...
from this link :
Air Marshal S. Radhakrishnan, Air Officer Commanding-in-Chief of the Southern Naval Command

That's why Gen. Kapoor inaugurated a course on defence journalism recently.