LCA News and Discussions

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Re: LCA News and Discussions

Postby KrishG » 11 Jun 2010 16:30

Eurojet's offer of TVC for EJ200 (whether for LCA or EF) advertises more than just enhanced agility.

From the first article:
* Thrust vectoring nozzle technology is being offered to the Eurofighter customer nations on the basis that it could significantly lower lifecycle costs by reducing fuel burn by "3-4% on an average mission"
* Extending the life of hot section parts
* In addition, the technology can enhance agility, which could be of particular benefit to the Tejas as it is a delta-winged design that lacks canards.
* The flight-control system can be configured to use the thrust vectoring nozzle as an additional "control surface", boosting damage tolerance and reducing the risk of loss-of-control at low speeds
* Furthermore, take-off distance for an aircraft such as the LCA could be reduced by around 20%, even in "hot and high" conditions.

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Re: LCA News and Discussions

Postby Dileep » 11 Jun 2010 16:44

Austin, maneuverability at stall speed is only one of the benefits of TVC. At any speed, it provides control moments much more than a deflecting surface can. It also helps to gain or bleed energy at a faster rate than possible with the surfaces alone.

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Re: LCA News and Discussions

Postby shiv » 11 Jun 2010 17:35

Austin - I think Prodyut Das' point is not that a lightweight fighter can do without it. He merely says that it will be difficult to control, which basically means that control laws will be that much more difficult to write and develop. In my quote of his article I left out the last line which basically says that this would be an expensive exercise. I guess he implies that time-cost considerations may have made TV a non-starter in small aircraft.

I think the word "inertia" (again used by Das) is important.I am guessing (without inside knowledge) that the heavier aircraft benefits more from TV at comparable low speeds.

Having said that, there is absoluetly no doubt that the Su 30, MiG 29 OVT and F 22 can do things that no other aircraft can do which are directly attributable to TV. Having said that the agility and handling of some sporting/aerobatic aircraft minus TV or FBW are real examples of light aircraft maneuverability without TV.

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Re: LCA News and Discussions

Postby chackojoseph » 11 Jun 2010 17:47

What happens if 2 small fighters dogfight? Will TVC be an advantage then?

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Re: LCA News and Discussions

Postby Venu » 11 Jun 2010 18:01

If what our renowned gurus say - TVC will make a light aircrafts go out of control - is true, pilot will be busy bringing the flight under control and will finally end up losing the fight. To the contrary, if the TVC helped increasing the maneuverability and having under perfect control, then he might win. As simple as that.

I for one think that TVC engines do help, irrespective of its whether its light of heavy, since FCS will be modified if TVC is incorporated. Hence what ever factors that may cause the aircraft to go out of control will be taken care of. So, TVC will be an added advantage.

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Re: LCA News and Discussions

Postby Kanson » 11 Jun 2010 18:03

nukavarapu wrote:X-Posting from Military Aviation Thread.

There is an update about the AURA program in Shiv Aroor's site:

AURA: India's UCAV Programme

With government funds to be spent on the AURA programme, there are seasoned skeptics as well. Former Air Force Chief, S Krishnaswamy, who flew combat missions in the 1965 Indo-Pak war, “Such research is definitely necessary, but the more we venture into unknown areas the greater the risk of time and cost overruns. We should ask ourselves if such a systems fits in with our requirement at this time. There should be safeguards to ensure it doesn’t turn into another joke like the Light Combat Aircraft.”


I fail to understand why the IAF Oldies are so discrediting when it comes to LCA ... :(


Hmm, what i'm going to say may not be palatable...
Manytimes the statement of these Oldies carry more weight because of the position they held rather than the knowledge of the subject. I can quote many examples. Barak deal is well known example where a subordinate's, who was an expert in missile/gunnery, opnion was not considered eventhough he repeatedly put his foot down against the then Naval Chief Arun Prakash recommendation for the JV with Barak missile. DRDO too reluctantly agreed, kind of like 50:50.

In the Services, due to the command structure, these ideas and knowledge are top driven. If there is any official stance that will be either top driven or have the acknowledgement of the brass and bottom to top is a rarity. And if the Chief is against such notion there is no way a junior officier's opinion or recommendation will be heard.

By the way the missle-gunnery expert who spoke against AP is not an ordinary officer.

Second fault lies with DRDO, who doesnt know how to market their product with these "Gentlemen" officers. It failed to grasp a fundamental fact of asthetics in selling the products to these officers who give more importance to the squeaky clean suits and shinny boots. Marketing by DRDO is akin to the attempt by the BSNL to put Customer Service Desk with the same old guy who happened to be as callous in answering the calls from customer but with a coat and tie in the face of strict competition from the Private players. Anyway there is now a proposal for a new marketing arm.

Just a general observation.

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Re: LCA News and Discussions

Postby Kanson » 11 Jun 2010 18:03

chackojoseph wrote:What happens if 2 small fighters dogfight? Will TVC be an advantage then?

I was about to ask that question :D you were faster..

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Re: LCA News and Discussions

Postby Kanson » 11 Jun 2010 18:08

Austin wrote:
nukavarapu wrote:I fail to understand why the IAF Oldies are so discrediting when it comes to LCA ... :(


The criticism or praise from Chief ( past or present ) is because they have the best grip and knowledge on the project development and knows exactly where thing stands from customer prespective and Kiccha is old hand.



Ofcourse Kiccha could be xxx yyy or xxyy. So could he call the LCA as "joke".
Is LCA a joke? If it is a joke then we can acknowlege Kiccha has the best grip of knowledge etc etc..

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Re: LCA News and Discussions

Postby Gaur » 11 Jun 2010 18:12

indranilroy wrote:.........Unfortunately his plane is heavier (assuming slightly asymmetric TWR) . At this slow speed, he can barely maintain this turn rate......

I am sorry, but I am unable to understand why a heavier a/c will have more difficulty to "maintain turn rate at slow speed" than a light fighter? Is it because its higher weight will pull it down and it will lose more altitude while while it is in turn? If so then what does "slow speed" has to do with it? When the a/c is in turn, no matter its speed the only vertical forces acting on the a/c will be the lift provided by its fins and body opposing the weight of a/c pulling it down. That will be at any speed. So, as per my limited understanding, the ability to maintain the turn rate should be dependent upon the thrust and aerodynamics of the a/c rather than its weight?
So, basically, please forgive my lack of understanding and educate me on these two issues:
1> Why will higher weight lead to more difficulty to maintain turn rate?
2> Why will this difficulty arise only at lower speeds?

On a different note, here is my 2 paisa about why only heavy fighters employ tvc. As I had posted before, it is because for light fighters, the the advantage of TVC may be eclipsed by the added weight as shown by F-16 MATV program.

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Re: LCA News and Discussions

Postby Kanson » 11 Jun 2010 18:22

shiv wrote:Austin - I think Prodyut Das' point is not that a lightweight fighter can do without it. He merely says that it will be difficult to control, which basically means that control laws will be that much more difficult to write and develop. In my quote of his article I left out the last line which basically says that this would be an expensive exercise. I guess he implies that time-cost considerations may have made TV a non-starter in small aircraft.

I think the word "inertia" (again used by Das) is important.I am guessing (without inside knowledge) that the heavier aircraft benefits more from TV at comparable low speeds.

Having said that, there is absoluetly no doubt that the Su 30, MiG 29 OVT and F 22 can do things that no other aircraft can do which are directly attributable to TV. Having said that the agility and handling of some sporting/aerobatic aircraft minus TV or FBW are real examples of light aircraft maneuverability without TV.


Shiv....he may be right. But i failed to see how the control laws could be much more difficult to write, it just adds another layer. May be he implied to say it takes more time. JMT

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Re: LCA News and Discussions

Postby chackojoseph » 11 Jun 2010 18:24

Gaur wrote:I am sorry, but I am unable to understand why a heavier a/c will have more difficulty to "maintain turn rate at slow speed" than a light fighter? Is it because its higher weight will pull it down and it will lose more altitude while while it is in turn? If so then what does "slow speed" has to do with it? When the a/c is in turn, no matter its speed the only vertical forces acting on the a/c will be the lift provided by its fins and body opposing the weight of a/c pulling it down. That will be at any speed. So, as per my limited understanding, the ability to maintain the turn rate should be dependent upon the thrust and aerodynamics of the a/c rather than its weight?
So, basically, please forgive my lack of understanding and educate me on these two issues:
1> Why will higher weight lead to more difficulty to maintain turn rate?
2> Why will this difficulty arise only at lower speeds?

On a different note, here is my 2 paisa about why only heavy fighters employ tvc. As I had posted before, it is because for light fighters, the the advantage of TVC may be eclipsed by the added weight as shown by F-16 MATV program.


See, we are still rooted in 1971 mentality where we will expect classic dog fighting. Bigger the aircraft, bigger the arc of turn.

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Re: LCA News and Discussions

Postby negi » 11 Jun 2010 18:26

Kanson wrote:
chackojoseph wrote:What happens if 2 small fighters dogfight? Will TVC be an advantage then?

I was about to ask that question :D you were faster..

Well wouldn't it make more sense if we just compare stats like ITR,STR, service ceiling, climb rate and top speed at various altitudes for the two aircraft instead of worrying about TVC ,canards etc ? :)

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Re: LCA News and Discussions

Postby Kanson » 11 Jun 2010 18:32

^yup, you were taking abt the end, whereas the disuccsion is about the means to the end. As IAF asking more powerful engine, it is one more way of achieving the end.

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Re: LCA News and Discussions

Postby negi » 11 Jun 2010 18:37

chackojoseph wrote:See, we are still rooted in 1971 mentality where we will expect classic dog fighting. Bigger the aircraft, bigger the arc of turn.

For a given 'g' rating and velocity yes heavier AC should have a higher radius of turn.

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Re: LCA News and Discussions

Postby chackojoseph » 11 Jun 2010 18:44

negi wrote:
chackojoseph wrote:See, we are still rooted in 1971 mentality where we will expect classic dog fighting. Bigger the aircraft, bigger the arc of turn.

For a given 'g' rating and velocity yes heavier AC should have a higher radius of turn.


Yes, I should have separated those sentences.

Actually I am waiting for my favorite Bradmin to come say ' take away yuoo woobly to noobie thread and get buzzing there, youuu mothe fuccas, cause dis is LCA thread."

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Re: LCA News and Discussions

Postby Gaur » 11 Jun 2010 18:53

negi wrote:
chackojoseph wrote:See, we are still rooted in 1971 mentality where we will expect classic dog fighting. Bigger the aircraft, bigger the arc of turn.

For a given 'g' rating and velocity yes heavier AC should have a higher radius of turn.

Again, why? I am not saying you are wrong. I am just asking why. This is because as I explained in my previous post, my understanding of this issue is rather different.

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Re: LCA News and Discussions

Postby Gagan » 11 Jun 2010 18:54

Can TVC or a flex nozzle help a fighter take off and land at MTOW from a comparatively shorter runway?

If it can, won't it be a useful thing to have in the middle of a war with aircraft taking off or landing from bombed out runways or roads, where the required runway length might not be there.

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Re: LCA News and Discussions

Postby chackojoseph » 11 Jun 2010 19:01

Gaur wrote:Again, why? I am not saying you are wrong. I am just asking why. This is because as I explained in my previous post, my understanding of this issue is rather different.


Simple. Smaller aircraft having better TWR would be more nimble. LCA is one aircraft made with such an aim in mind "Small and Nimble."

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Re: LCA News and Discussions

Postby chackojoseph » 11 Jun 2010 19:10

Gagan wrote:Can TVC or a flex nozzle help a fighter take off and land at MTOW from a comparatively shorter runway?

If it can, won't it be a useful thing to have in the middle of a war with aircraft taking off or landing from bombed out runways or roads, where the required runway length might not be there.


You mean as a RATO? My understanding is that it TVC bleeds energy and and has certain stall. Gurus could enlighten.

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Re: LCA News and Discussions

Postby Gagan » 11 Jun 2010 19:30

I saw a National Geographic / Discovery channel documentary showing how NASA/USAF experimented with TVC on a fighter (I think one of those single engined NASA test Jets) and they successfully demonstrated simulated-mid air, very short landings using TVC and high AoA.
Image
I wonder if this can have a use in real life while taking off and landing.

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Re: LCA News and Discussions

Postby chackojoseph » 11 Jun 2010 19:39

^^^^^ I just commented on the take off. It would require sufficient windspeed to be built up. Even if you manage to deflect it with a TVC, I doubt the take off will sustain. If the engine speed has already been built up , then why use TVC?

Short landings are possible as it would bleed the forward momentum and hence enable to stop with less taxi. But, again, the Aoa if high could lead to stall and possible crash.

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Re: LCA News and Discussions

Postby Viv S » 11 Jun 2010 19:45

Gaur wrote:
negi wrote:For a given 'g' rating and velocity yes heavier AC should have a higher radius of turn.

Again, why? I am not saying you are wrong. I am just asking why. This is because as I explained in my previous post, my understanding of this issue is rather different.


Well the way I see it, a heavier aircraft will have a high moment of inertia and that'll inhibit the angular acceleration while the aircraft turns.

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Re: LCA News and Discussions

Postby Gaur » 11 Jun 2010 20:06

^^
But do not the heavier (and thus larger) a/cs' control surfaces have larger surface area to counter this?
I mean, the high moment of inertial will hinder any movement that changes the direction of flight (which is almost every maneuver that the heavy a/c can hope to make). So does that mean that a heavy a/c will always be less agile than a light a/c?

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Re: LCA News and Discussions

Postby Indranil » 11 Jun 2010 20:35

Gaur wrote:^^
But do not the heavier (and thus larger) a/cs' control surfaces have larger surface area to counter this?
I mean, the high moment of inertial will hinder any movement that changes the direction of flight (which is almost every maneuver that the heavy a/c can hope to make). So does that mean that a heavy a/c will always be less agile than a light a/c?


Gaur, you are right in pointing out that weight alone doesn't mean that a heavier plane will turn slowly. After all it is simple physics. For a heavier plane you need to provide proportionally higher centripetal force. The problem here is that this force is generated through the control surfaces and lift (I am assuming exactly the same TWR for both). So a bigger plane requires much bigger surfaces. Unfortunately, this is an aerodynamic problem. As you increase the AoA, the bigger surface will have a faster rate of drop of lift, and also a faster edge separation.

There are many more factors like a heavier plane is generally a bigger plane and generally bleeds energy faster through higher drag etc etc.

It is a matter of fact that bigger the plane, the bigger is the arc :).

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Re: LCA News and Discussions

Postby Indranil » 11 Jun 2010 20:59

There are other uses of TVC too as pointed out by others, mostly rising of the fact that the engine can now be a control surface. However, I wanted to speak from a maneuverability point of view. Also in the dogfight I just showcased only one case from when the guy from behind might use TVC. There are cases where the guy in front might like to use the TVC to perform moves like the cobra maneuver to make the aggressor shoot past, and then the hunted becomes the hunter!

I did not want to say that TVC on a lighter plane fails to do what it does on a heavier plane. However this is a game of optimizing the pros and cons. For a light fighter the extra gain in weight is a higher percentage of its weight. Hence, most research have shown that fuel efficiency stays almost the same, if not getting worse.

Also in a small plane it is generally much easier to point the nose wherever you want. So the requirement for enhanced nose pointing ability is not felt. Also, with TVC you would have made the fighter heavier with the same wing area, which is quite detrimental to a plane's agility.

That percentage of weight gain is critical.

However for a single delta wing plane like the LCA, the advantages of 2D thrust vectoring, is like adding a horizontal tail plane. This in theory atleast should shorten runway requirements, and (may be) make the plane slightly more agile in the air. That is why I said, we can only speak in general, exact gains and losses have to be simulated and there is no doubt in my mind that the guys at ADA will do it.

Somebody pointed out that the control should remain same, except for another layer. You are right. But the problem is that the frequency at which the changes have to be made and amplitude of changes would become bigger. Not only is there a physical limit, but you would need a faster processor, more cooling requirements.

P.S. Austin sahab it is not true that other countries didn't toy with the idea of having there planes have TVC. Forget about the Europeans, even the Chinese evaluated TVC for their designs. There are perfect reasons why they opted out of it in the J-11, J-10, and the J-17. The problem for the US and the Russians is that they are global leaders. They have had to find out a lot of new things. The rest of the world has inherited a lot of knowledge from them.

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Re: LCA News and Discussions

Postby Sanku » 11 Jun 2010 21:12

Kanson wrote:
With government funds to be spent on the AURA programme, there are seasoned skeptics as well. Former Air Force Chief, S Krishnaswamy, who flew combat missions in the 1965 Indo-Pak war, “Such research is definitely necessary, but the more we venture into unknown areas the greater the risk of time and cost overruns. We should ask ourselves if such a systems fits in with our requirement at this time. There should be safeguards to ensure it doesn’t turn into another joke like the Light Combat Aircraft.”


Hmm, what i'm going to say may not be palatable...
.


Actually Kanson, you say ACM Krishnaswamy's word carries more weight due to his position than knowledge.

Of course what it tells me that in the world you live in position and knowledge are not linked.

Fortunately for us, that is not really true in IAF and especially for the man in question.

Character assassination only goes that far before the assassins character is bought out.

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Re: LCA News and Discussions

Postby Sanku » 11 Jun 2010 21:16

Kanson wrote:
Austin wrote:
The criticism or praise from Chief ( past or present ) is because they have the best grip and knowledge on the project development and knows exactly where thing stands from customer prespective and Kiccha is old hand.



Ofcourse Kiccha could be xxx yyy or xxyy. So could he call the LCA as "joke".
Is LCA a joke? If it is a joke then we can acknowlege Kiccha has the best grip of knowledge etc etc..


I think Shiv said pretty much the same thing in a more refined manner about trying for the moon in your first high jump and ending up neither here nor there.

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Re: LCA News and Discussions

Postby shiv » 11 Jun 2010 21:18

Again a non expert comment from me. For a given airspeed a heavier fighter will require more energy than a lighter one to cause a change of direction.

Normally "changes of direction" are caused by airflow around the wings and control surfaces. The slower the speed the lower the airflow and there is less energy to be traded for a change of direction. In the absence of TV the only way to maneuver is by acceleration causing more airflow over the control surfaces. But TV can "cheat" this requirement by "toppling" the aircraft into a different position (about its center of mass) without any increase in airspeed. This can be done in a light or a heavy aircraft, but the "energy saved" is a lot more in a heavy aircraft which would have needed to pump in a lot more power to accelerate and then change direction if TV was absent.

For example imagine an aircraft at a dangerously slow speed at high angle of attack. It may be seconds from stalling. Either it needs to go nose down immediately, or energy (afterburner?) needs to be pumped in to accelerate it so it does not stall. If it cannot quickly develop the power to accelerate, and if it also does not have the airspeed (airflow over wings) to go nose down, it will stall. In such a case TV can "topple" the axis of the aircraft into a nose down position so it can dive and gain airspeed.

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Re: LCA News and Discussions

Postby Indranil » 11 Jun 2010 21:27

shiv wrote:Again a non expert comment from me. For a given airspeed a heavier fighter will require more energy than a lighter one to cause a change of direction.

Normally "changes of direction" are caused by airflow around the wings and control surfaces. The slower the speed the lower the airflow and there is less energy to be traded for a change of direction. In the absence of TV the only way to maneuver is by acceleration causing more airflow over the control surfaces. But TV can "cheat" this requirement by "toppling" the aircraft into a different position (about its center of mass) without any increase in airspeed. This can be done in a light or a heavy aircraft, but the "energy saved" is a lot more in a heavy aircraft which would have needed to pump in a lot more power to accelerate and then change direction if TV was absent.

For example imagine an aircraft at a dangerously slow speed at high angle of attack. It may be seconds from stalling. Either it needs to go nose down immediately, or energy (afterburner?) needs to be pumped in to accelerate it so it does not stall. If it cannot quickly develop the power to accelerate, and if it also does not have the airspeed (airflow over wings) to go nose down, it will stall. In such a case TV can "topple" the axis of the aircraft into a nose down position so it can dive and gain airspeed.


Very nice post Shiv. I was trying to explain the same thing. But you seem to have done it much better!

Somebody posted that TVC might be helpful in evading missiles. Generally missile evasions are high speed maneuvers. Can somebody expalin how TVC could be helpful there!

Also here I would give you an intuition of why TVC wouldn't change the path of a plane. At TWR of 1, the thrust is about 10 times the mass of the plane. What is the momentum at say 650 km/hr? 650 times the mass of the plane. Even if whole of the thrust and not just a component of it is used to change the direction, how much do you expect the change in momentum to be?

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Re: LCA News and Discussions

Postby shiv » 11 Jun 2010 21:34

Thanks indranil roy but credit is due to you for some very lucid posts.

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Re: LCA News and Discussions

Postby Kanson » 11 Jun 2010 21:52

Sanku wrote:Actually Kanson, you say ACM Krishnaswamy's word carries more weight due to his position than knowledge.

Of course what it tells me that in the world you live in position and knowledge are not linked.

Fortunately for us, that is not really true in IAF and especially for the man in question.

Character assassination only goes that far before the assassins character is bought out.

hmm.....you take umbrage if i say you have problem with reading...but talking abt character and assasination, you give me no option rather point your selective reading while trying to create an impression...The question was abt the Oldies...
I fail to understand why the IAF Oldies are so discrediting

and i ended saying..
Just a general observation.

So where comes here the character of Kiccha, assassination etc . Of course, expecting this from the person who write stories is too much i guess. :)

I think Shiv said pretty much the same thing in a more refined manner about trying for the moon in your first high jump and ending up neither here nor there.

I remember writing a long post justifying why it is beneficial to look for moon and in fact we always should aim for moon. And we are *not*nether here nor there in the case of LCA.

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Re: LCA News and Discussions

Postby KrishG » 11 Jun 2010 22:03

Gagan wrote:I saw a National Geographic / Discovery channel documentary showing how NASA/USAF experimented with TVC on a fighter (I think one of those single engined NASA test Jets) and they successfully demonstrated simulated-mid air, very short landings using TVC and high AoA.




Gagan wrote:I wonder if this can have a use in real life while taking off and landing.


According to Eurojet, a TVC nozzle could reduce LCA's take-off distance by 20%.
Furthermore, take-off distance for an aircraft such as the LCA could be reduced by around 20%, even in "hot and high" conditions, he adds.

IMHO the take-off distance would be reduced due to additional force in the upward direction (due to TVC) which would complement the lift generated. The net upward force would be high enough for take-off at a shorter distance than an a/c without TVC which has solely depend on lift generated (sufficient lift would be generated only at a comparatively higher speed ie longer take off distance).

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Re: LCA News and Discussions

Postby Sanku » 11 Jun 2010 22:23

Kanson, please keep making such comments with petty shots against ACM and when that is objected to against fellow posters. We see what the real content is.

Thanks....

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Re: LCA News and Discussions

Postby Vipul » 11 Jun 2010 22:23

Light combat aircraft Tejas undergoes second phase of hot weather trials.

Light combat aircraft (LCA) 'Tejas' which is scheduled to attain Initial Operational Clearance (IOC) by this year-end has undergone the second phase of hot weather trials in the past one week at the AirForce station in Nagpur.

The first phase of hot weather trails were conducted at the same venue in May-Jun 2008. On both occasions, the trials were very well supported by Air Force Station Nagpur.

The objective of the current phase of hot weather trials is to prove that the aircraft is in IOC configuration with the weapon system and sensors integrated.

During the trials, the two Tejas aircraft have undertaken trial sorties especially to check out the aircraft systems such as Digital Flight Control Computer, Avionics Systems, Multi Mode Radar, RWR and the Electrical and Environment Control Systems under extremely high ambient temperature conditions up to 45 degree Celsius.

The trial team consisted of IAF flight test crew from the National Flight Test Centre (NFTC) and Scientists/Engineers from Aeronautical Development Agency (ADA), Hindustan Aeronautics Limited (HAL), Bangalore, ADE, NAL, CEMILAC and DGAQA, defence release said.

During the test flights, data, video and audio from the test aircraft were transmitted in real time through the fibre optic connectivity provided by the Air Force AFNET to NFTC Bangalore, for closer monitoring and detailed analysis.

This facility has proven to be very effective in optimising overall flight test effort, while enhancing flight test safety, it said.

The trial team was able to achieve all the objectives during the week long hectic trials.

The LCA is progressing steadily towards achieving IOC by end of December 2010 and subsequent entry into service under the able guidance of P S Subramanyam Director, ADA and the optimal flight test planning under the leadership of Air Commodore Rohit Varma VM, Project Director (Flight Test) of NFTC, the release from defence PRO in Nagpur added.

Shalav
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Re: LCA News and Discussions

Postby Shalav » 11 Jun 2010 22:24

Gagan wrote:Image


Gagan,

The nozzle would be flexed at a down angle for both landing and t/o.

See any video of a sea harrier short t/o - the nozzles are down angled, TVC will provide a similar effect.

Landing distance is reduced because the down angle of the TVC nozzle takes at least some weight off the airfoils, which leads to a slower landing velocity (as lift required to keep the aircraft aloft is reduced) and hence shorter landing distance.

Same goes for t/o. A down angled TVC will take some weight off the wings leading to a lower V(r) which translates to a shorter t/o distance.

shiv
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Re: LCA News and Discussions

Postby shiv » 11 Jun 2010 22:41

KrishG wrote:


The Su 30 MKI does both the "helicopter" maneuver and the "post stall loop" in every single Su 30 display including all the videos I have put of the MKI on YouTube. Both are done at low altitude (visible from the ground)

The yanks used to claim that these maneuvers are useless in combat :roll:

Off topic
Last edited by shiv on 11 Jun 2010 22:47, edited 1 time in total.

shiv
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Re: LCA News and Discussions

Postby shiv » 11 Jun 2010 22:44

Shalav wrote:Gagan,

The nozzle would be flexed at a down angle for both landing and t/o.

See any video of a sea harrier short t/o - the nozzles are down angled, TVC will provide a similar effect.


No shalav. Not in this case. Gagan's picture is correct. The nozzle here is well behind the center of mass. The "up" nozzle tends to cause a nose pitch up leading to a high angle of attack causing high lift at low speed. In the Harrier the nozzles are at the center of mass.

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Re: LCA News and Discussions

Postby Gagan » 11 Jun 2010 22:48

Now here if we take the example of the F-35, not only does it have a TVC nozzle at the end, it also has a lift fan in the middle-front so that it can do a very STO.
The F-35 design is a more refined concept of what we are discussing here.

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Re: LCA News and Discussions

Postby Austin » 11 Jun 2010 22:50

Thanks Dileep , Shiv for the reply

indranilroy wrote:P.S. Austin sahab it is not true that other countries didn't toy with the idea of having there planes have TVC. Forget about the Europeans, even the Chinese evaluated TVC for their designs. There are perfect reasons why they opted out of it in the J-11, J-10, and the J-17. The problem for the US and the Russians is that they are global leaders. They have had to find out a lot of new things. The rest of the world has inherited a lot of knowledge from them.


Evaluated in which sense , did they actually build a prototype , mastered the TVC/FCS system or they did some theoretical evaluation ?

I think every one including the Europeans understand that multi-axis TVC does bring in advantage but right now no one is ready to spead the extra mulllah build a prototype and flight test it.

Although weight is a factor but from what I have read even for AL-31FP engine with 2D TVC the additional weight added was ~ 200 kg .

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Re: LCA News and Discussions

Postby Gaur » 11 Jun 2010 22:53

^^
200kg? Does that include strengthening of structure around engine and ballast added to counter cg disbalance? Or it just the weight of the TVC nozzle?


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