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LCA: News & Discussions - October 2016

The Military Issues & History Forum is a venue to discuss issues relating to the military aspects of the Indian Armed Forces, whether the past, present or future. We request members to kindly stay within the mandate of this forum and keep their exchanges of views, on a civilised level, however vehemently any disagreement may be felt. All feedback regarding forum usage may be sent to the moderators using the Feedback Form or by clicking the Report Post Icon in any objectionable post for proper action. Please note that the views expressed by the Members and Moderators on these discussion boards are that of the individuals only and do not reflect the official policy or view of the Bharat-Rakshak.com Website. Copyright Violation is strictly prohibited and may result in revocation of your posting rights - please read the FAQ for full details. Users must also abide by the Forum Guidelines at all times.
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Re: LCA: News & Discussions - October 2016

Postby Cybaru » 13 Mar 2017 07:55

Chinmay wrote:Cybaru, my response was to Shiv's query. CAS is a mission and has been performed by all aircraft ranging from drones to helicopters to B1 bombers, so no aircraft in production today has been 'designed for' CAS. The era of dedicated CAS aircraft like the A-10 or Su-25 is over.


Sorry my very bad. I didn't read properly. I didn't see "Do" we... :)

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Re: LCA: News & Discussions - October 2016

Postby JTull » 13 Mar 2017 15:20

This thread is not LCA thread anymore

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Re: LCA: News & Discussions - October 2016

Postby ramana » 13 Mar 2017 23:16

Guys, Why are you posting off topic posts here?

GD, Et tu?

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Re: LCA: News & Discussions - October 2016

Postby Kartik » 13 Mar 2017 23:19

SP2 looking good!

Image

From the Tejas LCA FB page

The setting sun lighting up LA-5002 after a practice sortie during the Republic Day fly past preparation phase.

Jai Hind.

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Re: LCA: News & Discussions - October 2016

Postby Kartik » 14 Mar 2017 02:13

Sri Lanka's fighter selection an opportunity for India

Source: Institute for Defence Studies and Analyses; issued March 13, 2017

By Sanjay Badri-Maharaj
In August 2016, the Sri Lankan government made the announcement that it was seeking to procure between eight and 12 combat aircraft to replace its ageing air force assets. While there has been much speculation about Sri Lanka’s choice – with the Sino-Pak JF-17 reportedly being strongly pushed by Pakistan – it is suggested that this selection process can offer India a unique opportunity both to strengthen military ties with Sri Lanka as well as to make a breakthrough into the aviation export market.

The Sri Lanka Air Force (SLAF) is facing the prospect of being without a single combat aircraft, despite operating a force with three dedicated combat aircraft squadrons – No.5 with F-7G, the No. 10 with the Kfir C.2/7, and No. 12 with the MiG-27M. The Sri Lankan government revealed that, by August 2016, only a single Kfir (out of seven survivors) was operational, while none of the F.7Gs and MiG-27Ms were operational.1 Cabinet Spokesman and Parliamentary Reforms and Media Minister Gayantha Karunathilaka expressed the situation in stark terms:

“At the moment, only one Kfir aircraft – the remaining six aircrafts cannot be used. We have seven MIG aircrafts and eight other aircrafts but none of them can be used. The Government will consider all offers and select a suitable one…”2

While the government’s official position is that the fleet requirements have not yet been finalized, it is apparent that the SLAF is seeking multi-role combat aircraft to replace its current fleet.3 Aircraft manufacturers will be courting the SLAF. With the JF-17 being pushed strongly, one may soon witness the Russians and Swedes entering the fray with a variant of either the MiG-29 or the Su-27 and the Gripen, respectively. For its part, India may be in a position to use its unique diplomatic and geographic proximity to offer two products – the Tejas and the Advanced Hawk – as possible contenders to meet the SLAF requirement.

It should be noted that India’s foray into military aviation exports has been plagued by missteps, shortfalls in support and poor communications. The sale of Dhruv helicopters to Ecuador was widely hailed, and rightly so, as a major breakthrough for Indian arms export. However, after a number of crashes (several of which were caused by pilot error), the helicopters were withdrawn from use, citing, among other things, poor spares support from Hindustan Aeronautics Limited (HAL).4

The sale of Chetaks to Suriname was plagued by poor contract management and “financial and administrative obstacles”, which led to the helicopters being ready long before pilots were ready to be trained, leading to a delay in delivery of the helicopters.5 Subsequent supplies of aircraft have been gifts or heavily discounted sales of Chetak and Dhruv helicopters and Dornier Do-228 surveillance aircraft to the Maldives, Mauritius, the Seychelles, Nepal and Bhutan.

Yet, unlike sales to Ecuador and Suriname, India is geographically proximate to Sri Lanka and, if an Indian choice is made, use can be made of Indian Air Force support facilities. Furthermore, India has had a somewhat low-key but nonetheless important role in equipping the SLAF. In the past, India had provided 24 L-70 guns, 24 battle-field surveillance radars, 11 upgraded Super Fledermaus radars, four Indra- I & II radars and 10 mine-protected vehicles to assist in the defence of SLAF air bases. These proved useful against air attack by the former Liberation Tigers of Tamil Eelam (LTTE)’s air wing consisting of armed microlight aircraft as well as from LTTE infiltrators.6 India is already a major supplier to the Sri Lankan Navy with two 105m Offshore Patrol Vessels under construction at Goa.7

Should the SLAF desire a supersonic multi-role aircraft, India’s Tejas Mk.1, despite its still being in the developmental phase, could be a viable option. The aircraft has already demonstrated significant capabilities in the air-to-air and air-to-ground roles and the limited number of aircraft being sought by the SLAF lends itself to relatively easy accommodation with HAL’s production schedule and capacity. Moreover, as the Indian Air Force will be undertaking training and conversion activities with the type, Sri Lanka could benefit from this process.

On the other hand, if the SLAF is seeking a cost-effective multi-role aircraft with a relatively low operating cost – and is willing to forego the “prestige” of supersonic aircraft – then the BAE-HAL Advanced Hawk has the potential to meet this requirement. The Advanced Hawk has significant combat capabilities with provision for Brimstone air-to-ground missiles and ASRAAM air-to-air missiles.8 As a subsonic aircraft with a dual training role, the operating costs of the Advanced Hawk would inevitably be lower than any supersonic combat aircraft while still offering substantial combat capability.

This combination of capability and cost-effectiveness is an important consideration given the SLAF’s problems with its existing combat assets and the acquisition and operating costs of modern supersonic aircraft.9 In addition, the large fleet of BAE Hawks operated by the Indian Air Force and the strong overhaul and maintenance facilities available in India could make the Advanced Hawk attractive to the SLAF.

If India is desirous of securing this order, it must not treat it as a purely transactional arrangement. The export of Indian combat aircraft would be a major step forward for Indian arms exports and, as such, India should be flexible in respect of prices. India should also not hesitate to offer attractive financing packages and lines of credit at low interest rates to encourage Sri Lanka to “buy Indian” – the lack of such packages reportedly playing a role in the SLAF declining a Pakistani offer of the JF-17.10

From all angles – political, economic, diplomatic and military – India is in a position to meet the SLAF’s potential combat aircraft requirements. It is a rare confluence of circumstances that has the potential to operate in India’s favour if the Indian political, bureaucratic and military-industrial leadership has the will and desire to see a sale of Indian combat aircraft to Sri Lanka become a reality.

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Re: LCA: News & Discussions - October 2016

Postby SaiK » 14 Mar 2017 02:21

^sure.. where is our capability with regards to production engineering optimized to drive at profits. we can't be selling to SL at cost price

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Re: LCA: News & Discussions - October 2016

Postby Marten » 14 Mar 2017 08:33

SaiK wrote:^sure.. where is our capability with regards to production engineering optimized to drive at profits. we can't be selling to SL at cost price

You're talking gobbledygook. What is production engineering if not series production? MIC is never engineered for the simple case of profiteering (war mongering is). What are the strategic goals for the LCA in the context of the SL contest?
--------------------------------------------------------------------
Who will SL be using these planes against?

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Re: LCA: News & Discussions - October 2016

Postby arshyam » 14 Mar 2017 08:37

Better SL gets a dozen JF-17s for us to take a detailed look at. The IAF needs all the LCAs we can make at this point.

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Re: LCA: News & Discussions - October 2016

Postby sarang » 14 Mar 2017 10:37

aye! +1008

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Re: LCA: News & Discussions - October 2016

Postby srai » 14 Mar 2017 17:18

Clean
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Air Show
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Centerline - Drop tank (725ltr)
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Bombs (1000lb, 250/450kg HSLD, Practice) & Drop Tanks (800ltr, 1200ltr) & Litening-III Pod
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LGB - Griffin-3 (1000lb, PB-500), Paveway-2 (1000lb)
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AAM - R-73, Python-5 & Derby
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Last edited by srai on 15 Mar 2017 05:21, edited 1 time in total.

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Re: LCA: News & Discussions - October 2016

Postby ramana » 14 Mar 2017 21:17

srai/Indranil, Those white strips are strain gages?

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Re: LCA: News & Discussions - October 2016

Postby shiv » 14 Mar 2017 22:08

No soap bars on nose?

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Re: LCA: News & Discussions - October 2016

Postby Rakesh » 14 Mar 2017 22:09

Hakeemji, it is still there :)

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Re: LCA: News & Discussions - October 2016

Postby Marten » 14 Mar 2017 22:28

What is the red thingie on the gun station?

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Re: LCA: News & Discussions - October 2016

Postby Kartik » 14 Mar 2017 22:58

Camera to record the in-flight stores separation.

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Re: LCA: News & Discussions - October 2016

Postby JayS » 14 Mar 2017 23:30

ramana wrote:srai/Indranil, Those white strips are strain gages?


Aluminium foil covering irregularities on the aero surface.

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Re: LCA: News & Discussions - October 2016

Postby Reddy » 15 Mar 2017 05:20

JayS wrote:
ramana wrote:srai/Indranil, Those white strips are strain gages?


Aluminium foil covering irregularities on the aero surface.


Some time back someone explained it as some sort of lightning protection thingy. If you look a the LCA without paint you'll see the metal cage clearly.
Image

On painted LCA - the paint is stripping off the shiny metal cage. Probably need to sand up the shiny aluminum for better paint adhesion :)
Image

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Re: LCA: News & Discussions - October 2016

Postby JayS » 15 Mar 2017 10:16

Reddy wrote:
JayS wrote:
Aluminium foil covering irregularities on the aero surface.


Some time back someone explained it as some sort of lightning protection thingy. If you look a the LCA without paint you'll see the metal cage clearly.
Image

On painted LCA - the paint is stripping off the shiny metal cage. Probably need to sand up the shiny aluminum for better paint adhesion :)
Image


They are not part of the aircraft as I understand. They are temporarily put on on the aero surfaces to cover unwanted irregularities. Source of the info is Tejas FB page admin. In above pics the strips are covering bolts/rivets that fixes the composite skin panels to the underlying wing structure elements.

For lightening protection, the composite panels have embeded metal wire mesh or metal wire path for lightening to follow. You wont see them from top.

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Re: LCA: News & Discussions - October 2016

Postby srai » 15 Mar 2017 13:28

Top also has similar "mesh" before paint.
Image

Bottom view similar:
Image

Given that those white strips are always where that "mesh" is, one can conclude that it is not a temp "fix" but seem more of a structural component for conductivity. Paint (or colored strips of sorts) seem to chip off those areas more frequently. So, it seems both JayS and Reddy are correct ;)

https://www.livefistdefence.com/2011/02/aero-india-lca-tejas-aerial-display.html
vijaykumar
February 10, 2011 at 4:59 pm

HI Dear friends, The white patches on LCA is not the paint peeling off. These patches are special strips to have the uniform conductivity of the aircraft. and these strips will be peeling of when the aircraft does low level and high speed sortie.After every such sortie these strips will be replaced. I just want to say as of today LCA has done 1500 plus flights and the aircraft's which are flying in aeroindia have gone through such low level & High speed trails 100's of 100 times as part of flight testing. so just think the performance & Capabilty of LCA . you just rewind and see 5 tejas aircrafts formation flight on inagural day.How the bottom surface of wing looks.it's so clean so before commenting some thing just think. And ofcourse the painting is nothing for HAL/ADA . which was not done due to priority of flight testing.

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Re: LCA: News & Discussions - October 2016

Postby JayS » 15 Mar 2017 20:44

And how exactly would sticking aluminium strips help LCA have uniform conductivity and for what purpose..? Why would an aircraft need something to be put on for uniform conductivity when it is already designed to carry heavy current of lightening. You see those white strips not only on unpainted LCAs but also on the painted LCAs on top of the paint. Why would a fully painted LCA need anything to put on it for adjusting its conductivity..??

The white strips are called "Speed Tape". Its aluminium strips with very strong adhesives. It is used for temporary fix/repair works in aircrafts. Google for it.

And no, there is no paint peeling off from anywhere. Do you really think they would use a paint which would peel off frequently for a high performance machine which costs a cool 300Cr and operates under some of the most trying external conditions..?? At least I don't think so.

BTW the grid like structure you see in above pictures, is the wing structural members' attachment locations on the skin. The skin panels are riveted to the underlying structural components - wing spar and ribs. For example this is the F35 wing structure (easy to find for F35, not so for LCA):
Image

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Re: LCA: News & Discussions - October 2016

Postby prasannasimha » 15 Mar 2017 21:31

They are strain guages during test flights.

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Re: LCA: News & Discussions - October 2016

Postby Indranil » 15 Mar 2017 23:42

Those strips have nothing to do with conductivity.

The skin, ribs and spars of the LCA are all made of composite. However they are not made of the same material. Neither are they of the same thickness. This is because different parts of the wing encounter different bending and stress moments. Take for example, the wing join to the fuselage. Tejas has three stress and two bending joints.

Although these parts are all made of composites, they are not co-cured together. There was a proposal to co-cure the internal structure to the lower surface of the wing, but that did not materialize. Therefore, these structural and skin elements have to be riveted together. However, composites are brittle. Cracks and fractures can originate from the holes and propagate outwards. These cracks and fractures are not easy to detect and repair.

To overcome this problem, they left the joins metallic. This is what you see in the completely unpainted aircraft. Now on the SPs, they put various kinds of gauges and other instrumentation devices on these joins to study and validate the actual parameters against design targets. They have to redo these tests for various load outs and flight envelops. When these gauges are removed, one leaves behind an irregular surface. This is what is patched up with aluminium tape because SDREs can't afford to send the aircraft back to the paint shop very time.

You won't see these in production aircraft.

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Re: LCA: News & Discussions - October 2016

Postby Cybaru » 15 Mar 2017 23:44

^ Okay now it makes sense! Thanks

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Re: LCA: News & Discussions - October 2016

Postby ramana » 16 Mar 2017 00:16

Thanks, Indranil.

Reason I asked if they are strain gages is there is now new thinking that measuring strain during every flight will allow to determine life of the aircraft. Nowadays strain gages come in long strip and give readings from each of the locations. Gets analyzed to get cumulative loading on the structure.

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Re: LCA: News & Discussions - October 2016

Postby JayS » 16 Mar 2017 01:51

ramana wrote:Thanks, Indranil.

Reason I asked if they are strain gages is there is now new thinking that measuring strain during every flight will allow to determine life of the aircraft. Nowadays strain gages come in long strip and give readings from each of the locations. Gets analyzed to get cumulative loading on the structure.


Can't say for aircrafts for sure, but for Mil engines this is there for ages now, the used up life tracking. Of coarse not direct strain measurement but measuring actual flight profile in terms of G loads, speed, ambient conditions, actual thrust levels etc. Its simple but rather successful method to improve utilization of the machine to the fullest. The Saffran marketing guy at AI-2017 was claiming they have been using it since very first engine they made, but I highly doubt that, more like since M-88 they might be doing it. For Kaveri also we have a similar life tracking system (I saw a poster in GTRE stall). Not sure how mature it is, since Kaveri is not in flight so it may not be mature yet.

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Re: LCA: News & Discussions - October 2016

Postby JayS » 16 Mar 2017 02:05

Indranil wrote:Those strips have nothing to do with conductivity.

The skin, ribs and spars of the LCA are all made of composite. However they are not made of the same material. Neither are they of the same thickness. This is because different parts of the wing encounter different bending and stress moments. Take for example, the wing join to the fuselage. Tejas has three stress and two bending joints.

Although these parts are all made of composites, they are not co-cured together. There was a proposal to co-cure the internal structure to the lower surface of the wing, but that did not materialize. Therefore, these structural and skin elements have to be riveted together. However, composites are brittle. Cracks and fractures can originate from the holes and propagate outwards. These cracks and fractures are not easy to detect and repair.

To overcome this problem, they left the joins metallic. This is what you see in the completely unpainted aircraft. Now on the SPs, they put various kinds of gauges and other instrumentation devices on these joins to study and validate the actual parameters against design targets. They have to redo these tests for various load outs and flight envelops. When these gauges are removed, one leaves behind an irregular surface. This is what is patched up with aluminium tape because SDREs can't afford to send the aircraft back to the paint shop very time.

You won't see these in production aircraft.


Interesting. Composites are brittle but their stiffness value is very high and they are suppose to be highly resistant to fatigue and crack growth. Its one of the key advantages of composites over metals. But yes its extremely difficult to detect existing defects.

Hmm. Somehow I cannot digest this metallic joint thing. Why would they join two composite components using metallic joints?? And how exactly..?? Its perfectly fine to rivet composite skin to composite primary structure.

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Re: LCA: News & Discussions - October 2016

Postby ramana » 16 Mar 2017 02:09

To transfer moment between two panels.

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Re: LCA: News & Discussions - October 2016

Postby Zynda » 16 Mar 2017 02:20

JayS, you are correct that composites are more resistant to crack growth compared to metals. Even though it is hard to detect existing defects, they are accounted for during fatigue analysis and compliance is usually shown by testing for no growth of very small damages up until static loads. Hence a good static design of composite joint is not an issue from fatigue POV.

I am confused by metallic-composite joints as well. How is the metal attached to the composite structure? Is it bonded? Usually, bonded joints are avoided in Principle Structural Elements as fastening using rivets/bolts are more beneficial from DT design POV apart from a couple of other concerns. Further, if the metal is fastened to the composite structure, essentially one is shifting the location not eliminating the problems. It is not unusual to use titanium (or steel) patches over Graphite-Epoxy structures for repair purposes. Although same material as parent is preferred, some times metal substitution is allowed.

Interesting approach by the ADA if metallic-composite design is used on primary structures!

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Re: LCA: News & Discussions - October 2016

Postby Indranil » 16 Mar 2017 03:41

There must be a gap in my understanding. Let me find out and revert.

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Re: LCA: News & Discussions - October 2016

Postby srai » 16 Mar 2017 04:12

Image

Image

DRDO Tech Focus - LCA Structure (Oct 2004)


Carbon Fibre Composite Wings

The wings of Tejas have been designed to provide a minimum weight structure and to serve as integral fuel tanks. New materials like carbon fibre composite (CFC) and Al-Li alloy have been used for the wing construction of Tejas. As the wings carry fuel also, the lightning protection for wings has been evolved through detailed studies and experimentation. The wings are easy to maintain.


Salient Features
* Top and bottom interspar skins and intermeDIATe spars made of CFC
* Main wing-fuselage attachment brackets made of conventional and well proven A/ alloy
* Heavily loaded components like pylon support brackets, slat track ribs made of Ti/Al alloy
* Other machined and sheet metal components made from Al-Cu/Al-Li alloys
* Most of the fasteners are Ti screws and stainless steel nuts/anchor nuts


Image
Last edited by srai on 16 Mar 2017 04:39, edited 3 times in total.

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Re: LCA: News & Discussions - October 2016

Postby ramana » 16 Mar 2017 04:15

Thanks. Clarifies a lot. All those composite parts have to be attached.

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Re: LCA: News & Discussions - October 2016

Postby Indranil » 16 Mar 2017 04:50

So I am not that far off. I am missing small pieces. I know that NAL did develop some great technologies for composite aero structures. Their method of cocuring all the structural elements and the bottom skin (which is also of variable thickness) of Saras is a big deal.

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Re: LCA: News & Discussions - October 2016

Postby srai » 16 Mar 2017 05:50

Indranil wrote:So I am not that far off. I am missing small pieces. I know that NAL did develop some great technologies for composite aero structures. Their method of cocuring all the structural elements and the bottom skin (which is also of variable thickness) of Saras is a big deal.


JEC Asia Innovation Awards 2013: Composites wing and empennage - Winner: National Aerospace Laboratory, India
Image

CSIR-NAL has taken up the development of a 14 seater civil aircraft, ‘Saras’. For this aircraft, the entire wing and empennage are being developed using composites. One of the main components of the horizontal tail is the ‘bottom integrated skin’. The entire bottom substructure (5.1m x 1m), which consists of the skin, two spars, elevenribs and eight stringers have been co-cured in one single operation.

All the spars, ribs and stringers were laid to the net shape on the CFRP contoured tools. Later, these were transformed on to the already stacked skin using the ‘specially developed locating media’ to meet the stringent dimensional requirements. This was then vacuum bagged and cured in an autoclave at 175°C and 7bar pressure. Carbon/epoxy prepreg was used as the basic raw material to realise the structure. The entire co-cured structure has been developed using innovating tooling technology consisting of ‘hybridised silicone rubber tooling and CFRP tools’.

Image

Compared to an equivalent box in aluminium, the weight savings wereabout 25%. The integral construction not only reduced the number of individual parts but also eliminated 2,500 fasteners and lead to a cleaner aerodynamic surface. This technology has resulted in the reduction in manufacturing time and cost. The design of ply development includes the entire sub-structure consisting of bottom skin, front spar, rear spar, ribs and stringers which could be developed in one single shot.

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Re: LCA: News & Discussions - October 2016

Postby JayS » 16 Mar 2017 15:14

srai wrote:
Image

DRDO Tech Focus - LCA Structure (Oct 2004)


Carbon Fibre Composite Wings

The wings of Tejas have been designed to provide a minimum weight structure and to serve as integral fuel tanks. New materials like carbon fibre composite (CFC) and Al-Li alloy have been used for the wing construction of Tejas. As the wings carry fuel also, the lightning protection for wings has been evolved through detailed studies and experimentation. The wings are easy to maintain.


Salient Features
* Top and bottom interspar skins and intermeDIATe spars made of CFC
* Main wing-fuselage attachment brackets made of conventional and well proven A/ alloy
* Heavily loaded components like pylon support brackets, slat track ribs made of Ti/Al alloy
* Other machined and sheet metal components made from Al-Cu/Al-Li alloys
* Most of the fasteners are Ti screws and stainless steel nuts/anchor nuts


Image


Thanks for posting that. It clearly shows which parts are made of what material. This still does not clarify on whether the composite skin panels are directly riveted to the wing structural elements or through some metallic component.

In the picture above (with all the ladies in it) I see no metal at the joints. Panels look to be directly fitted to the spars/ribs/stringers.

BTW from the LG, it looks like its NLCA.

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Re: LCA: News & Discussions - October 2016

Postby srai » 16 Mar 2017 15:53

^^^

Zoom into the "wing skins" in the top-middle on the right side of the picture below. Looks like yellow CFC has some sort of blackish support braces, which should allow it to be bolted straight on to the metallic frame.

Image

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Re: LCA: News & Discussions - October 2016

Postby JayS » 16 Mar 2017 17:06

srai wrote:^^^

Zoom into the "wing skins" in the top-middle on the right side of the picture below. Looks like yellow CFC has some sort of blackish support braces, which should allow it to be bolted straight on to the metallic frame.

Image


Call me blind, but I can't see anything there which shows there are metallic joints. If you are hinting towards metallic brackets (say L bracket) which hold some of the spars and wing skin together, then there might be such brackets at some locations which is not unthinkable. But we will not see those from outside. I can't imagine having those at all the locations or even at majority of joint locations. I'd imagine most of the skin panels are simply riveted to the spars.

Looks like the ribs are metallic and are at the locations of pylons (typical).

Even if we assume there are metal joints everywhere, we should see none of them from outside. The composite wing skin panels should be the only things seen from outside. Painted or unpainted, we should not be seeing any metal (apart from the all metal components e.g. LE slats).

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Re: LCA: News & Discussions - October 2016

Postby prasannasimha » 16 Mar 2017 18:03

They are test strain guages. I had asked someone and they confirmed.(Those white looking stickers)They will not be seen in any series production models but only in test models to confirm various operating parameters.

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Re: LCA: News & Discussions - October 2016

Postby Zynda » 16 Mar 2017 18:11

The white strips on PV aircrafts are strain gauges. Regarding wing construction, I asked some one and they verified that there are no metallic joints (not fasteners...they were (are?) titanium ones) on skin to ribs & skin to spars. The wing root to fuselage joint is indeed metallic.


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Re: LCA: News & Discussions - October 2016

Postby Zynda » 16 Mar 2017 19:19

Srai, thanks for the video. But the fuselage of Tejas is metallic not composite. Like IR mentioned yesterdin, Tejas team wanted to co-cure as many structures as possible in the composite wing but they dropped the idea and went ahead with rivetted connections.


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