LCA News and Discussions, 22-Oct-2013

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Re: LCA News and Discussions, 22-Oct-2013

Postby Raman » 28 Jan 2015 22:57

The current air intake for the APU is grotesque. Certainly, it will go through a review. Does anybody know why they are not using a NACA airduct?


Actually, it is an ingenious solution. The APU intake is closed when the APU is not in operation (i.e., during most of regular flight operations) eliminating spillage drag.

What is that triangular hole and rectangular part painted near the air-brakes.


The triangular hole, as indranilroy pointed out, is a NACA inlet that is pointed the "wrong way", indicating that it is a vent of some sort.

The white rectangular part is a formation light. You can see it in operation here

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Re: LCA News and Discussions, 22-Oct-2013

Postby SaiK » 28 Jan 2015 23:59

I think it is grotesque bulge because the projection is outward rather neatly tucked in (like NACA). I 'd not think an issue to skin them better in the production versions. I think it might add few wind tunnel testing though. BTW, the wrong way wala also can be NACA-ed, and there is nothing stopping them to consider aerodynamics on those areas.

It might be some engineers of my grade doing it! ;)
Last edited by Indranil on 29 Jan 2015 02:42, edited 1 time in total.
Reason: Does not add anything. Please remove.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 29 Jan 2015 02:41

Saik sahab, no guess work as I had warned earlier. Let's keep the volume down and discussion as dense as possible.Please remove the marked posts.

Raman wrote:
The current air intake for the APU is grotesque. Certainly, it will go through a review. Does anybody know why they are not using a NACA airduct?


Actually, it is an ingenious solution. The APU intake is closed when the APU is not in operation (i.e., during most of regular flight operations) eliminating spillage drag.

Did not know that the intake closes. This makes it interesting. So what all does the Tejas APU power?

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Re: LCA News and Discussions, 22-Oct-2013

Postby VinodTK » 29 Jan 2015 03:04

India to hard sell Tejas at air show
India will showcase and hard sell its indigenous Light Combat Aircraft (LCA) Tejas at an air show here in February to prospective buyers from overseas, a top official said Wednesday.

"Tejas will be on flying and static display at the Aero India Show here from Feb 18-22 to solicit foreign buyers, as we have started producing them (fighters) for the Indian Air Force (IAF)," state-run Hindustan Aeronautics Ltd's (HAL) outgoing chairman R.K. Tyagi told reporters here.

The defence behemoth will also display military and civil variants of its Advanced Light Helicopter (ALH) Dhruv at the biennial international event in which producers, buyers, users and other stakeholders from the world over would participate.

The multi-role fighter is part of the first series production for induction into the IAF fleet.

"We have handed over the first aircraft (Mark-1 version) to IAF recently (Jan 17). Prospective buyers will be briefed on the fighter's unique features and abilities in combat role," Tyagi said on the occasion.

Defence Minister Manohar Parrikar also handed over the technical documents of the home grown LCA to Chief of Air Staff Air Chief Marshal Arup Raha here, though the fighter is yet to secure the final operation clearance (FOC) from the military regulator.

As a single engine multi-role supersonic fighter, Tejas will replace the IAF's ageing Russian-made MiG-21 fleet. The former will be inducted in six squadrons after the defence regulator, the Centre for Military Airworthiness & Certification (Cemilac) releases the FOC later this year.

The fourth generation fighter received the initial operational clearance (IOC-2) in December 2013 for evaluation by IAF ace pilots on various parameters.

Weighing 8.5 tonnes, Tejas can carry three tonnes of weapons, including air-to-air missiles, laser guided bombs, guns, conventional/retarded bombs and beyond visual range missiles.

Tejas is also fitted with digital fly-by-wire system, flight control systems and open architecture computer.

Each squadron will have 20 fighters and will be based at Sulur Air Force base near Coimbatore in southern Tamil Nadu.

In the design and development stage, HAL produced 15 LCA aircraft, including seven in the limited series production, two technology demonstrators, three prototypes, two trainer prototypes and one naval prototype.

Designed and developed by the state-run Defence Research and Development Organisation (DRDO) and its aeronautical agencies over the last three decades, the LCA project overran estimated budgetary costs and deadlines.

--Indo-Asian News Service fb/ml/bg

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Re: LCA News and Discussions, 22-Oct-2013

Postby NRao » 29 Jan 2015 03:18

Is that supposed to mean that the US in on board with selling the LCA with the GE engine?

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Re: LCA News and Discussions, 22-Oct-2013

Postby Avinandan » 29 Jan 2015 03:50

Thanks for the info and the pains taken to explain Indranil ! :)

By the way, did you get the answer regarding LCA's wing blending similar to Rafale, Gripen ?

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 29 Jan 2015 05:38

Avinandan wrote:Thanks for the info and the pains taken to explain Indranil ! :)

By the way, did you get the answer regarding LCA's wing blending similar to Rafale, Gripen ?

On the bottom? I think it will require too much work to blend it in without increasing the cross sectional area (which Tejas cannot afford to keep the wave drag down). Anyways, unlike the upper part, the bottom part does not affect the lift generation and control. However, a nicely blended bottom side does reduce interference drag. On the Tejas, there is a small amount of smoothening even on the bottom side to avoid acute or right angles.

Image

Image

One can complain that this surface could have been concave, especially at the edges so that the blending could have been perfectly smooth. But I guess it does the job.

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Re: LCA News and Discussions, 22-Oct-2013

Postby member_28722 » 29 Jan 2015 05:48

NRao wrote:Is that supposed to mean that the US in on board with selling the LCA with the GE engine?

How feasible would it be (schedule wise) to fit a different engine of similar capabilities into the Mk1, if US is not ready?
Last edited by Indranil on 29 Jan 2015 05:52, edited 1 time in total.
Reason: This is a utterly silly question. Do a Google search, or a search in this thread. If you still cannot find the answer, ask in the Newbie thread. You are excused for your first mistake. Warnings will follow from the second.

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Re: LCA News and Discussions, 22-Oct-2013

Postby shiv » 29 Jan 2015 06:58

saurabh.mhapsekar wrote:
NRao wrote:Is that supposed to mean that the US in on board with selling the LCA with the GE engine?

How feasible would it be (schedule wise) to fit a different engine of similar capabilities into the Mk1, if US is not ready?

Does "similar capability" mean power, or weight, or size to fit exactly into a slot in the LCA designed for the GE engine. If you can name one engine that has exactly the same size, and similar power and weight I will tell you about the feasibility.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 29 Jan 2015 07:12

I am going to open a can of worms here. Once again, answer only if you can give technical details. Replies with wrong technical details will be roasted and poster will be warned.

Hypothesis 1: LCA does not have an APU

Reasons: Otherwise LCA would not have required a hydrazine powered EPU (emergency power unit) for high AoA testing: Approach to High Angle of Attack Testing of Light Combat Aircraft LCA Tejas.

Return to an old question: What is the dorsal air intake scoop at the tail fin for?

Case 1:
This air is used along with the engine bleed air to cool the afterburner duct. This may be true because this air combines with the bleed air from the engine, then travels through the AB duct and leaves through the gap that I have pointed to before. This will also aid in IR signature suppression. The problem with this theory is that Tejas TDs did not have this scoop, but had two other scoops on each side of the dorsal spine. These scoops have been retained even now and are called "engine bay venting scoops". If air intake through these scoops was not sufficient, they could simply enlarged them. Why add a third bigger one, unless it provides more uniform cooling?
Case 2: The Environment Control System (ECS) in Tejas also used the bleed air from the engine by cooling it through a series of heat exchangers and a Cold Air Unit. The air from the dorsal air intake is used to provide fresh air to this mixture.
Case 3: Both of the above. The air from the 3 scoops mixes with the bleed air of the engine. The ECS sucks in the air it needs and rest is passes through the AB duct.

Does anybody know for sure? If not, can somebody ask at AI-15.

Raman sahab, where did you learn about the new Ram intake being controllable? All the above may be bogus, but if either case 1 or 3 is right, there is no question of spillage drag. Actually initially LSP-7 did not have this scoop. It just had a slit in the bump. They must have found out this is not providing enough air and changed back to this scoop as a quick fix till they find a permanent solution. May be unrelated, but I did see a tender to CAD studies to design an optimum intake at fin root for cooling avionics. Let me dig it out.

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Re: LCA News and Discussions, 22-Oct-2013

Postby ramana » 29 Jan 2015 07:13

Saurabh , Short answer: Very difficult as the plane is designed around the engine.
Would require total redesign. Besides LCA is unstable design which means the exact characteristics of the engine and plane are matched.

Reason is the engine is not podded like a transport/passenger plane where you can swap the engines.
Even there L1011 plane in the 1970s was hugely behind schedule when RR did not deliver the engine. LM exited the passenger plane business!

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Re: LCA News and Discussions, 22-Oct-2013

Postby Kashi » 29 Jan 2015 08:22

Recently we were looking for GE or EJ-200 engines for LCA. Of course we know that F-414 was selected, but does it mean that the two engines are similar enough to be aligned into the LCA airframe? Or have their been significant design changes in LCA to accommodate F-414?

I am quite a newbie to these technical matters since I have no expertise or experience in aerospace engineering.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 29 Jan 2015 08:44

^^^ Please take it to the newbie thread.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Prasad » 29 Jan 2015 10:14

Tarmak posted on twitter a few days back that NP2 did hstt. May fly soon i suppose.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Shreeman » 29 Jan 2015 14:13

indranilroy wrote:I am going to open a can of worms here. Once again, answer only if you can give technical details. Replies with wrong technical details will be roasted and poster will be warned.

Hypothesis 1: LCA does not have an APU

Reasons: Otherwise LCA would not have required a hydrazine powered EPU (emergency power unit) for high AoA testing: Approach to High Angle of Attack Testing of Light Combat Aircraft LCA Tejas.

Return to an old question: What is the dorsal air intake scoop at the tail fin for?

Case 1:
This air is used along with the engine bleed air to cool the afterburner duct. This may be true because this air combines with the bleed air from the engine, then travels through the AB duct and leaves through the gap that I have pointed to before. This will also aid in IR signature suppression. The problem with this theory is that Tejas TDs did not have this scoop, but had two other scoops on each side of the dorsal spine. These scoops have been retained even now and are called "engine bay venting scoops". If air intake through these scoops was not sufficient, they could simply enlarged them. Why add a third bigger one, unless it provides more uniform cooling?
Case 2: The Environment Control System (ECS) in Tejas also used the bleed air from the engine by cooling it through a series of heat exchangers and a Cold Air Unit. The air from the dorsal air intake is used to provide fresh air to this mixture.
Case 3: Both of the above. The air from the 3 scoops mixes with the bleed air of the engine. The ECS sucks in the air it needs and rest is passes through the AB duct.

Does anybody know for sure? If not, can somebody ask at AI-15.

Raman sahab, where did you learn about the new Ram intake being controllable? All the above may be bogus, but if either case 1 or 3 is right, there is no question of spillage drag. Actually initially LSP-7 did not have this scoop. It just had a slit in the bump. They must have found out this is not providing enough air and changed back to this scoop as a quick fix till they find a permanent solution. May be unrelated, but I did see a tender to CAD studies to design an optimum intake at fin root for cooling avionics. Let me dig it out.


Let me take a stab. The hypothesis is likely true. The primary evidence in support though should come from indigenization of JFS, secondary from the EPU and the like.

There are countless uses for the tail scoop, but environment management within the craft is the likely reason.

IR suppression is likely not the reason. Given that it has stuck around and been remodeled, I suspect things get hot under certain circumstances only, which may explain the need for a closing mechanism.

Again, since this sort of thing would only show up in actual testing, rapid cooling any other way might have been found to be unsuitable or needlessly complex. This also seems to dovetail with the missing skirt sections. Actual environmental readings may have been off compared to designed/predicted for certain areas.

I conjecture it has to do with engine environment management only. And that it might or might not stick around in 414 based Mk2. Who will ask at AI15?

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Re: LCA News and Discussions, 22-Oct-2013

Postby Thakur_B » 29 Jan 2015 19:08

Indranil, The APU exhaust is visible on the right hand side of the aircraft, just below tail fin. The EPU is necessary to power electronics in case of catastrophic failure where even the fuel supply of even APU is cut off. F-16 also has a hydrazine powered EPU. APUs run for a prolonged period and EPUs only for a few minutes.

The engine bay cooling vents are also present.
Image

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Re: LCA News and Discussions, 22-Oct-2013

Postby Raman » 29 Jan 2015 19:51

indranilroy, I am not privy to any special information. It is just a guess.

I believe that Tejas has an APU, but it is possible that it is only a JFS and not a full blown APU. Conventionally, the APU is usually needed during start-up to provide electrical power for avionics, environmental control and to run the engine starter. Once the engine is on, the systems are run using the engine's power and the APU is switched off.

Note that presence of EPU does not mean that an APU is not present. During emergency, power is required almost immediately. In a single engined airplane there is not enough time to start up the APU, which, after all, is a small jet engine that needs a start-up sequence, time to stabilize, etc. since it is not always running.

As for the scoop, I guess I'm mistaken. I saw the new scoop and thought that it was in an open position vs the closed position on other aircraft and did not realize that it was the new configuration.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 29 Jan 2015 20:29

@Thakur sahab,

You are right about:
1. EPU runs for a few minutes from engine flame-out to engine relight.
2. Cooling vents in your diagram. I called them "engine bay venting scoops".
3. F-16 houses a hydrazine powered EPU, as do many other modern fighters.

You are wrong about:
1. EPU is for running the avionics. It is for running the hydraulic pumps. From the paper:
The hydraulic system is critical to recovery from spin as it powers the controls and ironically will be the first system that will be lost in case of engine flameout. The Emergency pump can supply flow for three min but not at the rate desired for full control activity. Thus it is necessary to provide a backup hydraulic power source, preferably for both main and emergency systems, of approx 60 lpm. The critical period for consideration whilst sizing the back up Emergency power Unit (EPU) pump will be from recovery to relight,when the chute would have been released and the ac flown in frozen gains until relight and recovery of on board hydraulics. While an APU could be used, it would probably not be able operate at the test altitudes. Currently the international standard is to use a hydrazine driven pump. However handling of this fluid has its own safety requirements and the EPU would have to be replenished at the taxy holding point prior to take off and a EPU contents indication should be available at telemetry. The triggering of this pump is also of importance as too early (switching it on before the test point) would deplete EPU fuel unnecessarily, and switching it on too late could lead to damage of the ac hydraulic system and delayed recovery. Linking the EPU to engine RPM or reducing actuator rates with RPM could be one of the options.


@Raman sahab: The JFS can start or relight the engine up to a 6 km altitude. But it itself is started electrically using the onboard battery. The rectangular air intake of the JFS can be seen just aft of the MLG doors. The too NACA inlets aft of them (I guess) is again for cooling the engine bay.
Image

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Re: LCA News and Discussions, 22-Oct-2013

Postby JTull » 29 Jan 2015 20:44

Thakur_B, it could be the Jet Fuel Starter. Just wondering what other functions an APU would be needed for for a light aircraft when it could easily be hooked up to a ground unit. For larger aircraft you may need one.

Anyway, I'm not really qualified to comment too much on this.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Raman » 29 Jan 2015 21:02

That one is probably the exhaust and, the grilled inlet between the MLG doors is probably the inlet, if this F-15 schematic is anything to go by.

Image

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 29 Jan 2015 21:10

I think you are right. Explains why the rectangular opening is sooted.

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Re: LCA News and Discussions, 22-Oct-2013

Postby SaiK » 30 Jan 2015 00:42

FYI
http://img7.imageshack.us/img7/4035/escaneo001.jpg

I wish we have a new updated one.

this is a nice view
http://i.imgur.com/V4bIFw6.jpg
Last edited by Indranil on 30 Jan 2015 03:39, edited 1 time in total.
Reason: Does not add anything new. Let's keep the discussion as focussed as possible.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Karan M » 30 Jan 2015 01:08

Mixes up fibreglass as composite (subset as vs complete) but some interesting data

http://www.business-standard.com/articl ... 924_1.html


“The fibreglass (composite) content in the defence industry will alone be Rs 20,000 crore from the total Rs 200,000 crore worth spending in the development of indigenous defence systems in the next 10 years,” said Avinash Chander, chief of Defence Research and Development Organisation (DRDO), today.

In his inaugural address at the international conference on reinforced plastics here, Chander said the DRDO was working on raising the utilisation of fibreglass material components in the next version of light combat aircraft (LCA) Tejas equipped with Mark-II engine, from the “present 65 per cent to up to 80 per cent”.

“The wings for the aircraft are now totally being made out of fibreglass structures. We are going to look at having the entire fuselage made out of them. Once we achieve this, we want the domestic industry to manufacture the secondary (internal) structures in the aircraft,” he said.

......

Noting the use of fibreglass has been an integral part of the country's Agni series of missiles, he said research was happening to make use of them in the manufacture of submarines, unmanned aerial vehicles and light-weight radars.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Karan M » 30 Jan 2015 01:28

http://www.spsmai.com/exclusive/?id=192 ... Tejas-Mk.2

Aero India spotlight on LCA Tejas Mk.2
By SP's Special Correspondent
Photo Credit: SP's Special Correspondent

January 28, 2015: With the first production series LCA Tejas Mk.1 handed over to the IAF, and with more in the pipeline this year for squadron service first in Bengaluru and then Sulur in Tamil Nadu, this year's Aero India will fix the spotlight on the LCA Mk.2. With final operational clearance on the LCA Mk.1 for the Indian Air Force slated for the end of this year, and with the LCA Navy Mk.1 beginning its carrier compatbility trials successfully, [bb]the two Mk.1 programmes are effectively making progress in their final stages of development, clearing space now for attention to the LCA Mk.2, the platform that both the IAF and Indian Navy are looking forward to very keenly. [/b]The proposed platform, powered by the more powerful GE F414 turbofan (a deal that's finalised but yet to be signed), will be the true replacement of the MiG-21. It will be a more capable aircraft in every way, as first revealed at Aero India 2011. This year at the show in Bengaluru, there will be wide interest in the proposed platform. The Indian Air Force, sources say, has been putting custom pressure on the programme team to commit to better capabilities and timelines, and will be looking to see certain specifics announced or pledged at Aero India. Defence Minister Manohar Parrikar, who visited ADA earlier this month, is said to have expressed the need for far greater indigenous content on the LCA, maintaining that the current 60% level would be unacceptable on the LCA Mk.2. He was assured that project management and development sub-systems meant that the indigenous content percentage on the Mk.2 would be significantly higher from the start.

http://www.spsmai.com/exclusive/?id=195 ... oject-plan





HAL draws up priority project plan
By SP's Special Correspondent
Photo Credit: SP's Special Correspondent

January 28, 2015: As part of its effort to gear up for a higher-tempo role in defence production, a total of 111 technology projects have been identified by HAL in the areas of design, manufacture, avionics and material to support indigenisation and Prime Minister Narendra Modi's 'Make in India' campaign. The company has drawn up a modernisation and expansion plan for each division and R&D centre of the company to be implemented by 2018. These include the indigenous design & development of a mini UAV (8 kg class) for surveillance and reconnaissance, be part of a special purpose vehicle to design, develop and manufacture a Regional Civil Aircraft in collaboration with National Aeronautical Laboratory (NAL), move forward with the design and development of a 20 KN engine that was launched in 2012-13, to explore the acquisition of new and critical technologies through collaboration, co-development, transfer of technology agreements, formation of joint ventures etc. HAL has chalked out certain crucial projects such as Light Utility Helicopter (LUH), Light Combat Helicopter (LCH), HTT-40, Su-30 MKI, Light Combat Aircraft (LCA), Advanced Light Helicopter (ALH), Medium Multi Role Combat Aircraft (MMRCA) and a few others as its growth pillars moving forward, in addition to new projects. HAL believes that LCA, IJT and HTT-40 need to be its in-house technology drivers to demonstrate that the company is capable of delivering beyond license production of equipment, and helping. One of the major thrust areas for HAL this year onward will be exploiting the export potential of its products. The company will be hiring consultants this year to develop an appropriate marketing strategy for its defence and civil platforms.

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Re: LCA News and Discussions, 22-Oct-2013

Postby SaiK » 30 Jan 2015 06:02

who is more established to develop engines? GTRE or HAL? should not GTRE be focused on developing various types of engines for HAL?
Last edited by Indranil on 30 Jan 2015 06:21, edited 1 time in total.
Reason: User warned for posting questions and/or data that have been discussed many times, despite repeated cautions.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Shreeman » 30 Jan 2015 07:55

indranilroy wrote:I think you are right. Explains why the rectangular opening is sooted.


Indranil,

Actially the image does add something. It correlates the location of the jfs inlet/exhaust with its mounting location. A second APU or any other auxiliary that was never designed in the tail root is more than worthy of an AI15 inquiry. Something unusual must have happened if power to electronics is required in the air minus the engine and another power source was integrated.

I still say the tail root scoop doesnt appear to have anything with power generation given the recent JFS starts in Leh (reported just yesterday).

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Re: LCA News and Discussions, 22-Oct-2013

Postby neerajb » 30 Jan 2015 08:30

IR IMO the dorsal scoop is for jfs. Tejas has 110 kW jfs unit meant to start the engine only. The free power turbine is connected to AMAGB which then powers the HP spool for starting the engine. I don't think that there is enough space for jfs aft of MLG bay and beneath the engine. Moreover the only major physical changes that we have seen in Tejas is the addition of the hump and scoop which points towards jfs integration. JMT.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Shreeman » 30 Jan 2015 09:11

^^^
http://img7.imageshack.us/img7/4035/escaneo001.jpg

this shows the jfs location. the previous posts point to different inlet/exhausts for jfs.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 30 Jan 2015 09:16

Shreeman wrote:^^^
http://img7.imageshack.us/img7/4035/escaneo001.jpg

this shows the jfs location. the previous posts point to different inlet/exhausts for jfs.


JFS intakes and exhaust vents generally stay flush with the body because they are used mostly when the plane is stationary. If one uses scoops, then when the JFS is not working (which is almost always in flight), no air goes into the intake and everything is spilt out. Imagine the spillage drag. It is like flying with a cardboard stuck to the inlet of the scoop.

AFAIK, the JFS is placed just aft of the MLG. The idea that the rectangular hole is an exhaust is also verified by this picture.
Image

Having said that:
1. I do not know since when the JFS became part of the line-up. That will be great information.
2. I have no theory on what purpose is served by the metallic exhausts on both sides of the spine below the fin. Them being metallic suggest that the exhaust is hot.

Shreeman wrote:^^^
http://img7.imageshack.us/img7/4035/escaneo001.jpg

this shows the jfs location. the previous posts point to different inlet/exhausts for jfs.

That diagram is not current. It shows the state of the TDs.

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Re: LCA News and Discussions, 22-Oct-2013

Postby neerajb » 30 Jan 2015 09:19

Thanks. Makes sense, since accessory gearbox in GE 404 is mounted at the bottom, so the JFS is colocated with that.

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Re: LCA News and Discussions, 22-Oct-2013

Postby neerajb » 30 Jan 2015 09:25

indranilroy wrote:Having said that:
1. I do not know since when the JFS became part of the line-up. That will be great information.


It just clicked me that AM Rajkumar in his book 'The Tejas story' mentioned that after the initial smoke issues with JFS, he instructed the team to make it euro 3/4 compliant. He was associated with Tejas from 1993 to 2001. So it means that JSF was there from the very begining i.e. first flight.

Cheers....

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Re: LCA News and Discussions, 22-Oct-2013

Postby Shreeman » 30 Jan 2015 09:45

Check 1/27-1/28reports on JFS restarts in Leh. Its in there.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 30 Jan 2015 09:48

What is?

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Re: LCA News and Discussions, 22-Oct-2013

Postby Raman » 30 Jan 2015 10:21

indranilroy wrote:Having said that:
1. I do not know since when the JFS became part of the line-up. That will be great information.

Those two ducts have been at those locations since TD1.
Image
It is possible that JFS has been included since the beginning(?)

2. I have no theory on what purpose is served by the metallic exhausts on both sides of the spine below the fin. Them being metallic suggest that the exhaust is hot.

Those are afterburner venting ducts, as per the cutaway.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 30 Jan 2015 10:26

I am speaking of the vents marked as APU exhaust in this pic.

Image

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Re: LCA News and Discussions, 22-Oct-2013

Postby tsarkar » 30 Jan 2015 10:51

Indranil,

Jet Fuel Starter was there from day 1, only it was earlier called Gas Turbine Starter Unit.

Check page 13 here http://tejas.gov.in/IOC-Brochure.pdf

Never heard of APU on Tejas.

Added later - More details here http://www.hal-india.com/Aero%20Engine/M__146
Last edited by tsarkar on 30 Jan 2015 10:56, edited 1 time in total.

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Re: LCA News and Discussions, 22-Oct-2013

Postby Indranil » 30 Jan 2015 10:53

That's what I am saying. There is no APU. So what is that dorsal scoop for?

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Re: LCA News and Discussions, 22-Oct-2013

Postby Yogi_G » 30 Jan 2015 11:09

Is that a dorsal scoop a la F-16 Vista modification to bring in additional maneuvarability? The Americans had to scramble to get their fighters as nimble as the mig-29 and the sukhois and needed a series of modifications (physical and fly by wire) to be able to execute such maneuvers as the Pugachev.
Last edited by Indranil on 30 Jan 2015 11:56, edited 1 time in total.
Reason: This thread is on a tight lease. As I said earlier, if you speculate too wildly without knowledge, you will earn a warning. Well, now you have. If you wan't to speculate, take it to the newbie thread.

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Re: LCA News and Discussions, 22-Oct-2013

Postby tsarkar » 30 Jan 2015 11:19

My understanding was it was for engine bay cooling. That part of the fuselage was composite that didn't dissipate heat like a metal fuselage would.

http://en.wikipedia.org/wiki/File:LCA_Composites.jpg

So the scoop was added. TD don't have the scoop. I speculate part of the skirting was removed to allow the cooling air to exit.

Disclaimer - Jotting down whatever I could remember from someone associated with the program.

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Re: LCA News and Discussions, 22-Oct-2013

Postby neerajb » 30 Jan 2015 12:00

I don't think Tejas needs an APU when it has JSF. They can very well make the JFS run the generator via AMAGB and a clutch mechanism. Engine bay cooling could be one reason but isn't it protected by a firewall anyway? Check this image posted by Indranil, it shows the innards of that hump. Looks like it's there to cool some electronics. Possibly EW related stuff.

http://3.bp.blogspot.com/_zUe7sq7m3h0/S ... +tank1.JPG


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