LCA News and Discussions

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Lalmohan
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Re: LCA News and Discussions

Post by Lalmohan »

at the initiating attitude with airbrake deployment a non FCS aircraft will pitch up/down, however an FCS controlled plane can be designed to maintain the commanded attitude and just lose airspeed. however, its also possible to let the FCS alter attitude to reach the desired airspeed as the target (instead of the attitude as the target)
Indranil
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Re: LCA News and Discussions

Post by Indranil »

^^^ That IMHO is a correct observation. I am pretty sure that the FCS on Tejas tries to mitigate the effect and maintain attitude. But the CEMILAC paper suggests that it is not being able to completely compensate for it or not quickly enough.
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Re: LCA News and Discussions

Post by Kartik »

tsarkar wrote:
Kartik wrote:What was different about their design considerations?
The F-18 has oversized stabilators and flight control surfaces for adequate flight control. Hawk airbrake might create a downward pitch, but the aircraft is designed to be very stable, since it’s a trainer.
And the Tejas has large elevons that can do the job of providing flight control as well. Point being, there is nothing that prevents the Tejas from using control surfaces to compensate for the pitch up moment applied by the airbrake; if the same can be done using elevators, then elevons can do it too.
Kartik wrote:Yeah..we know from reports (from a former IAF senior pilot) that even the F-16 Block 60 and Super Hornet didn't meet the IAF's STR requirements. Does that mean that if these were available for induction in the IAF, that the IAF would decline and reject them altogether? Very unlikely.
They were rejected for failing the technical evaluation, that included these very parameters. Your statement completely contradicts reality.

The F-16 was designed as a A2A fighter, and the bells and whistles added for A2G role ate away flight performance required for the A2A role.
But that doesn't take away the fact that even an F-16 Block 60 and the F/A-18E/F, one level more advanced than even the F-16 Block52 that is the IAF's primary threat, doesn't meet the IAF's specs for performance. But had there not been a Rafale/Typhoon on offer, the IAF would've jumped at the offer of inducting them.
Kartik wrote:It is mature and hasn't proven to be troublesome.
Then why can’t the FCS correct the uncommanded pitch created by the original airbrakes.
Because it requires work to be done on that. Why don't you go and read on the Typhoon's transonic pitch up issue and how it was resolved. It was no easy task. Your implication that had we gone for a mature Mirage-2000 derived FBW on the Tejas, this wouldn't have happened is simply not true. This issue would've had to be tackled by whichever FBW technology was used, be it quadruplex redundant or triplex redundant with analog backup as on the Mirage-2000.
Kartik wrote:but that isn't the reason that the IAF is keeping Tejas Mk1 orders to 40
Agreed, from what I have been told, the IAF considers the pitch effect a nuisance but definitely not a showstopper. It has no effect on the induction plans.
Told by whom? Are you in the know of the IAF's issues with the Tejas? Maybe you could tell us what else is keeping the IAF from ordering more Tejas' to replace the huge numbers of MiG-21s.

As for this issue, yes its not a show stopper, since as long as the pilot can bring the aircraft back to its original state, after any uncommanded motion, the issue is not going to be a show stopper. As put in the US Military Standard for piloted airplanes,
MIL-STD-1797A4 states: “The aircraft shall be…resistant to departure from controlled flight, post-stall gyrations and spins. Adequate warning of approach to departure shall be provided. The aircraft shall exhibit no uncommanded motion which cannot be arrested promptly by simple application of pilot control.”
In every other aspect, the Tejas' flying qualities are very highly rated by the IAF's test pilots who've flown it. When an IAF TP calls it as "comparable to amongst the best in the world in so far as flight controls in concerned", then that does speak volumes for the FBW and the general design of the aircraft. As another TP, Grp Cpt George Thomas said about it"Its handling qualities are such that the pilot workload is low and the pilot can focus on sensors, weapons and combat and as regards basic flying, the aircraft can almost fly itself".

After all, most of these TP guys will be well versed with the Cooper-Harper handling qualities scale on which "excellent" rating 1 means that the handling characteristics are highly desirable and pilot compensation is not a factor for desired performance and "good" rating means that there are negligible deficiencies in the handling characteristics and pilot compensation is not a factor for desired performance.
Kartik wrote:What does the second statement even mean? What is a simpler design process?
Thank you for asking this question. It means assessing all the available means to achieve an end, and choosing the simplest and least riskiest means of achieving that end.

Like having airbrakes closer to CoG than having it elsewhere and having FCS mitigate any side effects. FWIW, using MLG door is reverting back to simpler design philosophy. Now, I am sure that the designers would have had some valid reason for not doing so in the first time itself, like avionics in the dorsal or fuel tanks in the ventral or wings, however, a simpler approach would have given precedence to placement of airbrakes.
Thank you for at least accepting that there may have been other mitigating factors involved in the selection of the location for the airbrake. I'm not sure though that the airbrakes have precedence of placement over more important things like fuel tanks. Anyhow, on the Tejas Mk2, they have the opportunity to re-lay out some of the avionics and pipes and such a layout change may well be done for the airbrake.
Which BR member will volunteer his son or father or brother or husband to go to fight knowing fully well they cannot outturn the enemy in a sticky situation? I am sure your perspective of “IAF not supporting…” will do an Immelman turn when your own flesh and blood goes to a fight in a Mk1.
This is a stupid statement if there ever was one. The IAF is not going to induct Tejas Mk1s at a state below the FOC level. At which point, most niggling issues would've been licked and the platform itself would be capable of giving a sound whipping to any MiG-21 that it comes across. Yet, there are plenty of fathers, brothers and husbands who fly the MiG-21 today and are ready to go to war in it. The Mk1 will be far safer, far superior to it.
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Re: LCA News and Discussions

Post by srai »

geeth wrote:
Could be, the the avionics is overcompensating for the airbrake induced torgue and causing the a/c to pitch up. Maybe the problem is an overactive FBW rather than a lagging FBW.
...

But tendency to pitch up or down when air brakes are applied is not a problem as such, as long as it is within the design limits. If not, they would redesign the air brake to suit the needs.
Isn't it the same as the F-14 air-brake maneuver Tom Cruise uses in Top Gun to defeat the best :wink:

If I remember correctly, when Maverick applies air-brakes his F-14 pitches up ... which makes the chase aircraft fly past just underneath.
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Re: LCA News and Discussions

Post by srai »

koti wrote:
Singha wrote:imo we should get the python5 for the Rafale , upg M2K and MKIs as well. it will further sharpen the advantages of Rafale in the knife fight regime and counter the aim9x quite nicely.
What is the WVR missile we are planning for Upg Mirage and Rafale. Don't tell its Matra's Magic 2.
...
That would be MICA IR.
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Re: LCA News and Discussions

Post by koti »

MICA IMO is an overkill for a WVR dogfight for its price/range. It is more of a replacement for Super 530.
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Re: LCA News and Discussions

Post by shiv »

koti wrote:MICA IMO is an overkill for a WVR dogfight for its price/range. It is more of a replacement for Super 530.
On this topic - here is an article by Raghu Raman on IDRW originally from Mint
http://idrw.org/?p=8514
India’s quest for the top gun
With announcement of Rafale as the Indian Air Force’s (IAF) next generation fighter, the “dogfight” among six of the world’s leading aircraft seems to have ended. However, those unfamiliar with weaponization strategies might wonder how countries decide upon any weapon system. Is it simply a matter of the best? If so, what is best?

The answer isn’t straightforward. The choice of a weapon system has less to do with specifics of its technical capabilities and more with imperatives of strategic doctrine. To understand this better, let’s start the journey from a lowly assault rifle rather than a sophisticated aerial platform such as a fighter jet.

An assault rifle is the mainstay of infantry, i.e. bulk of the fighting force of any country, and has over 10 design parameters which are often contradictory. For instance, a rifle should be accurate, have long range, be easy to maintain, sturdy enough to survive the rigours of battlefield, have a rapid rate of fire, and easy to handle with one hand for urban combat. In addition, the weapon must be light, have compact ammunition of the same calibre as other weapons so that supply chain logistics are manageable. It must have the capability to be used in different versions, for instance, paratroopers need shorter rifles and infantry support groups need longer ranges. Each of these requirements contradicts many others.

For example, accuracy over long ranges means the barrel will have to be long and the rate of fire cannot be high. This in turn makes the rifle unwieldy and suboptimal in a fierce firefight. If the rifle has to be sturdy with heavy munitions then it can’t be light and soldiers will tire before they enter battle.

Such complications exacerbate as weapon platforms get more complex. For instance, let’s consider the battle tank. The North Atlantic Treaty Organization (Nato) designers were compelled to build heavier tanks because their theatres are limited in space and their tanks had to be heavily armoured to hold ground without ceding position. A lesson reinforced by the German blitzkrieg when France was overrun in a matter of days. Also, Nato countries have comparatively low manpower though they are better skilled and educated. Hence, tanks such as the British Chieftain and French Leclerc were designed upward of 55 tonnes, have high crew comfort and the crew is “dual traded”, i.e. each member of the crew is expected to know more than just his own job, necessitating higher investments in training and retention.

The Soviets, however, relied on a much lighter and cheaper tank of the T54/55 series, because they could trade “time for space”. The Soviet strategy was to let invaders enter deep into the Russian hinterland—a situation they could afford, primarily because of their strategic depth—and then hit the supply chains through encirclement and, of course, the assistance of “General” Winter. The “Warsaw” doctrine, therefore, catered to Russia’s strengths which are plentiful supply of conscripted manpower, manoeuvring space and the severe weather where sophisticated equipment had more chances of failure. These strategies are consistent with their assault rifles as well. While the West has relied on relatively sophisticated weapons such as the American M16, British FAL and the French Famas, the Soviets developed the cheap but reliable AK47 series.

The key to understanding these strategies is to appreciate that in combat, a weapon is never pitted against another weapon in purely technical terms. It is, instead, a combination of the technical prowess, soldier’s capabilities, terrain and the national doctrine which decides the optimum arraignment of weapon platforms. So, while a sophisticated Heckler and Koch rifle could be an ideal weapon for highly-trained special forces, a much cheaper and rugged AK47 is better suited for mass infantry attacks, though on a purely technical comparison, the Heckler would outgun the AK.

Fighter aircraft are sophisticated weapon platforms and, hence, their inter-linkage is far more complicated. Modern fighters are expected to perform “omniroles”. They have to be highly manoeuvrable for “air-to-air” dogfights, possess heavy lift capability for tactical and strategic bombing, have long radius of action, be capable of operations from land and sea, etc. Their supply chain is even more complicated, especially for India, which has a wide and diverse area of geographical interest. Fighters need air refuelling, naval carriers, multi-weapon capability, an intricate web of radars, airborne warning and control system, sophisticated maintenance, repair and overhaul facilities and indigenous manufacturing to minimize external dependence.

They also need synchronization with other arms such as the army and navy. For, while IAF may pummel the enemy and establish air superiority, it is of little use unless armoured formations can rapidly exploit this hole and pour into enemy territory. And the latter’s ability to do that is contingent on their own modernization programme which depends on the country’s threat perceptions and mitigation strategy over the coming decades.

Viewed from this perspective, it is rarely the technical superiority of any single weapon system that matters. Instead, it is the complex “organization for battle” derived from strategic doctrine which serves as credible deterrence. And deterrence is what it must be—because as any soldier will affirm, war is an ironic game. The only winning move—is not to play.
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Re: LCA News and Discussions

Post by srai »

koti wrote:MICA IMO is an overkill for a WVR dogfight for its price/range. It is more of a replacement for Super 530.
You may want to do some read up on the MICA origins:

MICA background
...
Breaking away from established doctrines, the very high technical standards set by MICA are the result of an innovative operational concept. These evolved from the global understanding of the air-to-air battlespace and the appreciation of the need for a weapon system that would ensure asymmetry to win in aerial combat.

MICA stands for “Missile d’Interception, de Combat et d’Autodéfense”. A clear statement that this single missile system had to cover all facets of the air-to-air battle - BVR (Beyond Visual Range) interception, dogfight and self-defence.

The MICA system comprises 2 versions: MICA (EM) RF with an active radio frequency seeker and MICA IR with a passive dual waveband imaging infrared seeker. Both missiles are fully qualified and in mass production, being currently flown by numerous air forces worldwide.

A “full MICA” configuration on an aircraft such as Rafale gives a very flexible and high BVR fire power for Air Superiority during all kind of missions: combat air patrol, sweep, deep strike, recce, maritime operations. MICA missile in BVR mode introduces a new way of waging air combat by offering multi-target capability at extended ranges with the two interoperable guidance systems to hamper enemy counter measures. All carried (EM) RF or IR MICA missiles are fully BVR, being operable with or without data link target designation updating.

In short range (SR) combat, a MICA configuration on an aircraft offers a full "new generation" capability thanks to the outstanding performance of the missile (extreme agility and manoeuvrability). An additional advantage lies in the possibility of launching MICA with its seeker (namely IR) either locked-on to the target or not, while still featuring all BVR qualities.
...
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Re: LCA News and Discussions

Post by koti »

^ Noted.
I was more under the impression that MICA is a direct replacement for Super 530(~250Kg) and hence a more Medium ranged missile then a short ranged Magic.

What I fail to understand is the range(claimed) of MICA in comparison th that of Python 5 even though both fall under the same weight category.

And is it that IR Missiles are costlier then radar guided missiles? And are IR ones preferred in WVR to the Radar guided ones?
Last edited by koti on 24 Feb 2012 10:12, edited 1 time in total.
geeth
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Re: LCA News and Discussions

Post by geeth »

This is completely wrong. How do elevators and canards work. In fifth generation planes they are inline with the wings, not top or bottom! Also, they are in the front or the aft, aren't they?
You are basically confused about the difference between mechanics and aerodynamics.
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Re: LCA News and Discussions

Post by Singha »

And is it that IR Missiles are costlier then radar guided missiles? And are IR ones preferred in WVR to the Radar guided ones?

No, IR missiles other than MicaIR and one version of Aa10(allegedly) are always smaller and cheaper being for wvr only.
IR missiles being designed for wvr are inherently designed for high manouverability so they likely do better in that regime .... else with active radar and LOAL both radar and IR missiles permit the launch ac to turn away after shooting.

question is -
(1) is MicaIR having a better IIR seeker than python5?
(2) is passive BVR shooting using spectra + micaIR a proven concept?
(3) is MicaIR more manouverable than python5 or less?

we are certainly getting python5 to replace the old R73 stocks for sure....with K74 nowhere in the horizon....

whether or not we get MicaIR on rafale or settle for python5 depends on above questions.

there is no doubt we will get MicaEM (and Astra) and wont bother with amraam.
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Re: LCA News and Discussions

Post by prabhug »

My feeling was IAF wanted a lot of missile types which can be seamlessly mounted on all it aircraft.The missile would be chosen during the mission.This would be the surprise package every indian plane is going to carry.I am waiting for the day where Indian plane would carry two pythons and two r77 and two meteor.Damn it will make all our enemy sh.t in pants.
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Re: LCA News and Discussions

Post by koti »

Singha wrote: question is -
(1) is MicaIR having a better IIR seeker than python5?
(2) is passive BVR shooting using spectra + micaIR a proven concept?
(3) is MicaIR more manouverable than python5 or less?

we are certainly getting python5 to replace the old R73 stocks for sure....with K74 nowhere in the horizon....

whether or not we get MicaIR on rafale or settle for python5 depends on above questions.

there is no doubt we will get MicaEM (and Astra) and wont bother with amraam.
If that is the point, Why do not even need to consider Derby for Tejas, MicaEM should be sufficient and Mirage, Rafa and Tejas can have the commonality.
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Re: LCA News and Discussions

Post by srai »

^^^

The main problem with AAM, especially BVR, is that each uses a proprietary/encrypted channel between an aircraft's Radar and missile's receiver for target lock launch and mid-course guidance. The manufactures are reluctant to share these. As a result, you only see R-77 integrated with only Russian radars; MICA with French radars; Derby with Israeli radars; AMRAAM with American and EF radars. You see this effect with the indigenous Astra, which uses a Russian Agat seeker, is being integrated with Su-30MKI first, then MiG-29 and also the LCA (but could face integration challenges with its hybrid (Israeli/DRDO) MMR radar).
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Re: LCA News and Discussions

Post by koti »

Yes.
We already got the R-73 on Tejas, so we are doing good wrt Russian Encryption integration.
Given the potential orders for arming around 200 Tejas, MBDA might not object for MicaEW.

And I am a little worried about Meteor given this fact but it coming from MBDA may invalidate this problem.
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Re: LCA News and Discussions

Post by Indranil »

geeth wrote:
This is completely wrong. How do elevators and canards work. In fifth generation planes they are inline with the wings, not top or bottom! Also, they are in the front or the aft, aren't they?
You are basically confused about the difference between mechanics and aerodynamics.
:-o Quite frankly, I don't know which laws of physics change between both.
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Re: LCA News and Discussions

Post by Kanson »

tsarkar wrote:
shiv wrote:If you don't know where the CG is…
The flight control computer’s job is to know where the CG is at all times. Otherwise how will it apply corrective inputs via FBW and keep the aircraft flying. If the Flight Computer doesn’t know where the CG is, the aircraft won’t fly in the first place.

From those I spoke to, the FBW is not able to detect and actuate the elevons well in time to correct. FWIW, the services do not consider this as a showstopper, and this is not considered either for IOC or FOC.

This was just an example of the complex FBW development process that could have been avoided using a proven technology for getting the aircraft in the air, and zero base FBW development could have commenced as an enhancement.
Just as FBW development could be complex, Airbrakes and its associated issues could be complex.

Problem can't be solved by just copying FBW developed from other source as airbrakes, its features and associated aerodynamics issues could be different from other examples. Hope you realize this.

http://forums.bharat-rakshak.com/viewto ... 1#p1247551
geeth wrote:What is the problem with the LCA airbrakes..? I really can't comprehend anything from the discussion going on here.

Can someone please elaborate ? TIA
Sir ji FYI.
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Re: LCA News and Discussions

Post by Sid »

well if air breaks causes such noticeable pitch up action then can't we use them as 3rd control surface.

Might give some TVC equipped planes run for their money (at airshows) :D
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Re: LCA News and Discussions

Post by Badar »

srai wrote:The main problem with AAM, especially BVR, is that each uses a proprietary/encrypted channel between an aircraft's Radar and missile's receiver for target lock launch and mid-course guidance. The manufactures are reluctant to share these. As a result, you only see R-77 integrated with only Russian radars; MICA with French radars; Derby with Israeli radars; AMRAAM with American and EF radars. You see this effect with the indigenous Astra, which uses a Russian Agat seeker, is being integrated with Su-30MKI first, then MiG-29 and also the LCA (but could face integration challenges with its hybrid (Israeli/DRDO) MMR radar).
Why is it not possible to design the weapons in a manner that allows the customer to reflash the comsec gear on missile/radar with their own specific encryption codes?

There is no fundamental reason why this can't be done, is there? I mean other than to lock in weapon-radar-airframe combo by the OEM?
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Re: LCA News and Discussions

Post by Eric Leiderman »

Sid
The reason could be you even though you are bleeding airspeed in both cases (and loosing momentum). TVC gives lift fm the nozzles downthrust, where as with the brakes applied and speed reduced you are not getting sufficient lift from wings etc hence your air speed will have to be a lot higher than a TVC aircraft and that will not be a show stopper at an air show.
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Re: LCA News and Discussions

Post by Sid »

^^ he he, yeah know. that airshow part was pun from my end.

But my point was if current air-breaks works as a control surface, instead of actual breaks, then lets use it as what it is right now ;). Why fix it if it aint broken.
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Re: LCA News and Discussions

Post by srai »

Badar wrote:
srai wrote:The main problem with AAM, especially BVR, is that each uses a proprietary/encrypted channel between an aircraft's Radar and missile's receiver for target lock launch and mid-course guidance. The manufactures are reluctant to share these. As a result, you only see R-77 integrated with only Russian radars; MICA with French radars; Derby with Israeli radars; AMRAAM with American and EF radars. You see this effect with the indigenous Astra, which uses a Russian Agat seeker, is being integrated with Su-30MKI first, then MiG-29 and also the LCA (but could face integration challenges with its hybrid (Israeli/DRDO) MMR radar).
Why is it not possible to design the weapons in a manner that allows the customer to reflash the comsec gear on missile/radar with their own specific encryption codes?

There is no fundamental reason why this can't be done, is there? I mean other than to lock in weapon-radar-airframe combo by the OEM?
AFAIK, the IAF tried to integrate R-77 on Mirage-2000 and vice versa, Super-530D on MiG-29 in the late 90s without success. One way was more difficult apparently ... Western AAM to Russian a/c because of lack of open architecture or something like that.

As I pointed out in my post, it has more to do with the OEM not sharing or not willing to do it. Only when India develops its own (or JV) AAM with its seeker (most likely Astra Mk.2), then we will start seeing fleet-wide AAM commonality.
Last edited by srai on 25 Feb 2012 06:45, edited 1 time in total.
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Re: LCA News and Discussions

Post by SaiK »

one of the best explanations on the planet for dorsal /ventral aspects. scroll down to see the pics.
http://www.flyfishingdevon.co.uk/salmon ... eurotr.htm
/ot. :twisted:

BTW, would reverse thrusters be more useful for nLCA rather than those air breakers?
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Re: LCA News and Discussions

Post by Gurneesh »

I was bored :roll:

Image
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Re: LCA News and Discussions

Post by suryag »

++1 Gurneesh ji, these ADA guys are driving us jingoes mad
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Re: LCA News and Discussions

Post by geeth »

:-o Quite frankly, I don't know which laws of physics change between both.


I shall try to explain briefly, since you must be knowing the basics.

Take the case of a twin engine a/c. Suppose the left engine fails-then the forces are unbalanced and the right engine will create a yaw moment and tend to turn the nose of the a/c to the left. It is a simple example of mechanics i.e., a force with an arm (lever) will create a moment. No aerodynamics involved here.

Now, how do you correct this yaw moment? by deflecting the rudder to the right, a counter yaw moment can be created and make the a/c fly straight. The force produced by the deflection of rudder is aerodynamic force.

Similarly, the air brakes are essentially spoilers (of speed). They use the aerodynamic force created (pressure drag) when a flat plate is placed perpendicular to the flow. If the plate is convex, then coefficient of drag is less and if concave, more (than a flat plate). This is the aerodynamic force created to decelerate the a/c.

If these air brakes are placed above or below the horizontal CG line, then an unintended moment is also produced - if above the CG line a nose-up moment and if below, a nose-down moment. This moment is largely countered by the mass of a/c ahead or behind the CG as the case may be.

Take another case of that of a commercial a/c in flight. At the beginning of the flight, it may be carrying about 100 Tons or more of fuel, but towards the end of the flight, most of it is consumed. But the aerodynamic shape of the a/c remains same for all practical purposes. What happens?

While in steady level flight, The Dynamic lift will compensate the weight - The CG and CL (centre of lift) are apart in all three X-Y-Z axis. As the fuel gets consumed (and as there is movement inside a/c) the CG constantly shifts (Mechanics). How do you correct it? By adjusting the position of the CL (Aerodynamics).

Position of CL can be adjusted in different ways, depending upon the control surfaces available. One way is by changing the attitude of the a/c (thereby the angle of attack) by deflecting the elevators. Another way is by deflecting the flaps on wings. Ultimately, when the most desired position is arrived, the a/c is supposed to be 'trimmed' - resulting in minimum fuel consumption. For commercial a/c, the most important factor is fuel consumption. Therefore they try to achieve it by deflecting the control surfaces as little as necessary, therby reducing the drag.

Lastly, Canards, elevators, ailerons, flaps and also spoilers (of lift), airbrakes etc are aerodynamic control surfaces and the forces produced by the devices follow the laws of mechanics.
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Re: LCA News and Discussions

Post by Indranil »

Geeth sahab,

Aerodynamics is just the study of flow of a fluid called air. Some kind of flows can generate force. Once you know how to calculate the force it is all mechanics (which is the study of force on a body). For example if you can calculate the magnitude and direction of force, it is back to drawing free-body diagrams. Let me explain with your examples.
geeth wrote: I shall try to explain briefly, since you must be knowing the basics.

Take the case of a twin engine a/c. Suppose the left engine fails-then the forces are unbalanced and the right engine will create a yaw moment and tend to turn the nose of the a/c to the left. It is a simple example of mechanics i.e., a force with an arm (lever) will create a moment. No aerodynamics involved here.

Now, how do you correct this yaw moment? by deflecting the rudder to the right, a counter yaw moment can be created and make the a/c fly straight. The force produced by the deflection of rudder is aerodynamic force.
I would like to know under what category you would put yawing and pitching forces generated by TVC? I still don't see any difference in the effect of aerodynamic force vis-a-vis any other kind of force.
geeth wrote: Similarly, the air brakes are essentially spoilers (of speed). They use the aerodynamic force created (pressure drag) when a flat plate is placed perpendicular to the flow. If the plate is convex, then coefficient of drag is less and if concave, more (than a flat plate). This is the aerodynamic force created to decelerate the a/c.

If these air brakes are placed above or below the horizontal CG line, then an unintended moment is also produced - if above the CG line a nose-up moment and if below, a nose-down moment. This moment is largely countered by the mass of a/c ahead or behind the CG as the case may be.
I don't understand what is the meaning of "This moment is largely countered by the mass of a/c ahead or behind the CG as the case may be."
geeth wrote: Take another case of that of a commercial a/c in flight. At the beginning of the flight, it may be carrying about 100 Tons or more of fuel, but towards the end of the flight, most of it is consumed. But the aerodynamic shape of the a/c remains same for all practical purposes. What happens?

While in steady level flight, The Dynamic lift will compensate the weight - The CG and CL (centre of lift) are apart in all three X-Y-Z axis. As the fuel gets consumed (and as there is movement inside a/c) the CG constantly shifts (Mechanics). How do you correct it? By adjusting the position of the CL (Aerodynamics).

Position of CL can be adjusted in different ways, depending upon the control surfaces available. One way is by changing the attitude of the a/c (thereby the angle of attack) by deflecting the elevators. Another way is by deflecting the flaps on wings. Ultimately, when the most desired position is arrived, the a/c is supposed to be 'trimmed' - resulting in minimum fuel consumption. For commercial a/c, the most important factor is fuel consumption. Therefore they try to achieve it by deflecting the control surfaces as little as necessary, therby reducing the drag.
I did not get your point here. Are you trying to say that shifting of CG is a "mechanical" phenomenon and shifting of "center of lift" is an "aerodynamic" phenomenon? Well first of all, you shouldn't use the example of commercial aircraft for change in CG. The CG doesn't move very much in a commercial aircraft as the fuel tanks are placed near the CG (with the exception of special planes like the Concord which had two fuel tanks at the front and back of the plane). The Centre of pressure is not moved. It's just the magnitude of lift that differs. At the beginning, you have to counter a higher weight of the plane. At the end of the journey, you create lesser lift to counter a lower weight. It is again simple physics. Flaps are used to generate greater lift at low speeds so as to lower the stall speed. They are not used to move the Center of lift!

Probably you would have liked to give the example of a fighter aircraft whose shift in CG is considerable wrt to the length of the plane. But even here all aerodynamic forces are forces. The acceleration of the plane along any of the three axes is just based on resultant of all forces along that particular axis. Similarly, if the forces create a moment along the CG, the plane will rotate. There is nothing different with aerodynamic forces, thrust, drag, weight etc. They are a force and plane is an object which follows rules of physics.
geeth wrote: Lastly, Canards, elevators, ailerons, flaps and also spoilers (of lift), airbrakes etc are aerodynamic control surfaces and the forces produced by the devices follow the laws of mechanics.
Exactly, so if you want to study the effect of the aerodynamic surfaces on the aircraft, just draw a free body diagram. Aerodynamic force is not be different from any other kind of force!

I rest my case ... as we this is OT for the LCA thread. If you want to continue, please reply in a different thread.
geeth
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Re: LCA News and Discussions

Post by geeth »

If you want to continue, please reply in a different thread.
Not interested. As long as you understand Flight Mechanics and Aerodynamics are two different subjects, there is nothing more to talk.
SaiK
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Re: LCA News and Discussions

Post by SaiK »

what you both have to understand is one can't stand separate to the other. one is required to support the other. :wink:
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Re: LCA News and Discussions

Post by Kersi D »

prabhug wrote:My feeling was IAF wanted a lot of missile types which can be seamlessly mounted on all it aircraft.The missile would be chosen during the mission.This would be the surprise package every indian plane is going to carry.I am waiting for the day where Indian plane would carry two pythons and two r77 and two meteor.Damn it will make all our enemy sh.t in pants.
It will also make IAF logistics team s%$t in their pants !!! I look forward to the day we have TWO AAMs, one a WVR short range IR and another a BVR active radar homing. One MICA with both would be really good

K
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Re: LCA News and Discussions

Post by nash »

Kersi D wrote:
It will also make IAF logistics team s%$t in their pants !!! I look forward to the day we have TWO AAMs, one a WVR short range IR and another a BVR active radar homing. One MICA with both would be really good

K
I would say astra-MkI(50 km at certain altitude) should be made as mica, mean in both version one in IR and another in Radio seeker. Both of them should have dual-mode guidance.so that IR version can be used as BVR. and if needed its IR seeker can help in WVR range. It might overkill at WVR range.but might solve logistic issue.

MkII(>100KM) version should be a long range BVR like meteor or AMRAAM (C-D).
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Re: LCA News and Discussions

Post by Vipul »

Navy's Tejas fighter revs for take-off.

The Indian Navy has signalled strong support to the naval version of the Tejas Light Combat Aircraft (LCA), even before the indigenous fighter makes its first flight next month. In New Delhi, on Wednesday, the defence ministry’s apex Defence Acquisition Council (DAC) sanctioned the building of eight Naval LCA aircraft by Hindustan Aeronautics Limited (HAL).

“The eight fighters will be a mix of single-seat fighters and twin-seat trainers. The money for these has also been allocated,” says a senior Ministry of Defence official who was at the DAC meeting.

The Rs 3,650 crore Naval LCA programme was sanctioned in March 2003. Two prototypes are almost complete, the first a twin-seat trainer and the second a single-seat fighter. The eight fighters sanctioned on Wednesday are “Limited Series Production” or LSP fighters. These will be used for flight-testing, a painstaking process that could last two years or more. Once flight-testing is completed, HAL will establish a full-scale production line.

The Naval LCA is a crucial cog in the navy’s expansion and, therefore, in India’s increasingly visible maritime strategy. It is designed to fly from an aircraft carrier, a floating airfield that can project Indian power across the oceans. India has already bought Russian MiG-29K medium fighters to equip the INS Vikramaditya (formerly the Gorshkov) an aircraft carrier acquired from Russia. But another two (and possibly three) indigenous Vikrant-class aircraft carriers being built at Cochin Shipyard Ltd will field the Naval LCA, along with a medium fighter.

With the first of these, INS Vikrant, at an advanced stage of construction in Kochi, the navy is keen that development of the Naval LCA proceeds alongside. Earlier this month, the normally soft-spoken navy chief, Admiral Nirmal Verma, publicly criticised the Aeronautical Development Agency (ADA oversees the LCA programme) for placing the Naval LCA programme on the back burner, while focusing on the air force version of the Tejas.

The admiral’s words have goaded HAL into action. Business Standard has been told that the Naval LCA will take to the air in March, a landmark event for the navy.

“The Naval LCA will definitely fly in March. We are doing ground runs and starting low-speed taxi trials, in which the fighter rolls on the runway under its own power. Then we will do some high-speed taxi trials, in which the fighter will accelerate to take-off speed; but when its nose lifts off the ground, we will slow down without actually taking off. Only after that will the first flight actually take place,” says PV Deshmukh, HAL’s officiating CMD.

The Rs 10,397 crore air force Tejas project has obtained initial operational clearance (IOC), and will soon join the IAF’s fleet. But the Naval Tejas presents additional design challenges, such as being able to take off from an aircraft carrier’s ski-jump after accelerating for just 200 metres. Even more challenging are repeated carrier deck landings, in which a hook on the aircraft snags on an “arrestor cable” on the deck, forcing the aircraft to a standstill in just 90 metres. These landings, in which the fighter slams into the carrier deck at more than 7 metres per second, are often described as “controlled crashes.”

The navy and ADA will extensively test the Naval LCA on land before venturing onto an aircraft carrier at sea. A Shore-Based Test Facility (SBTF) has been created in Goa, which replicates the dimensions and conditions of a carrier deck, including the arrestor and gear that brings the aircraft to a quick halt; and the optical landing system that allows the pilot to “aim” his fighter at the arrestor wire spread out on the carrier deck. After extensive SBTF testing, the Naval LCA will face the crucial challenge of landing and taking off from an actual aircraft carrier.

The navy’s two prototypes and eight LSP fighters will be powered by General Electric GE F-404 engines. Meanwhile, ADA has selected the more advanced and powerful GE F-414 engine for the LCA Mark II. This engine will also power future Naval LCAs. With 15 per cent more thrust, the GE F-414 will be useful in taking off from an aircraft carrier deck.
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Re: LCA News and Discussions

Post by suryag »

again "next month" comes up
Sid
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Re: LCA News and Discussions

Post by Sid »

suryag wrote:again "next month" comes up
Tomorrow never dies my friend, but their promises do :oops:. Last time Ananth reported flight was just a few weeks off.
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Re: LCA News and Discussions

Post by Nick_S »

Vipul wrote:
“The Naval LCA will definitely fly in March. ......,” says PV Deshmukh, HAL’s officiating CMD.
I will believe it when I see it. Way too many deadlines passed for jingos. :(
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Re: LCA News and Discussions

Post by vic »

Vipul wrote:Navy's Tejas fighter revs for take-off.

The Indian Navy has signalled strong support to the naval version of the Tejas Light Combat Aircraft (LCA), even before the indigenous fighter makes its first flight next month. In New Delhi, on Wednesday, the defence ministry’s apex Defence Acquisition Council (DAC) sanctioned the building of eight Naval LCA aircraft by Hindustan Aeronautics Limited (HAL).

The eight fighters will be a mix of single-seat fighters and twin-seat trainers. The money for these has also been allocated,” says a senior Ministry of Defence official who was at the DAC meeting.

The Rs 3,650 crore Naval LCA programme was sanctioned in March 2003. Two prototypes are almost complete, the first a twin-seat trainer and the second a single-seat fighter. The eight fighters sanctioned on Wednesday are “Limited Series Production” or LSP fighters.

The navy’s two prototypes and eight LSP fighters will be powered by General Electric GE F-404 engines. Meanwhile, ADA has selected the more advanced and powerful GE F-414 engine for the LCA Mark II. This engine will also power future Naval LCAs. With 15 per cent more thrust, the GE F-414 will be useful in taking off from an aircraft carrier deck.

This shows LCA is giving a chance to ADA by ordering a few mark-1 itself. The only thing missing is the time period, as to when they will be delivered. Further I think that for Naval LCA mark-2 they should go with GE 414EPE engine of 120kn rather than 98kn engine of IAF Mark-2 as the timeline available for Naval LCA may be longer.

This brings confirmed LCA orders to :-

IAF Mark1 = 2TD+5PV+8LSP+20+20=55
IAF Mark2=2(?)
Naval Mark1=2+8=10
Naval Mark2=2(?)

Total=69, which is bigger than our Mirage 2000 fleet or Pakistan F-16 fleet
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Re: LCA News and Discussions

Post by merlin »

I can't understand why they want a full battery of flight testing for the newly sanctioned Naval Tejas LSPs. If the future is the Mk 2 powered by a higher thrust 414s and Mk 2 will be different aerodynamically then why not build and test those?
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Re: LCA News and Discussions

Post by Badar »

Kersi D wrote:
prabhug wrote:I am waiting for the day where Indian plane would carry two pythons and two r77 and two meteor.
It will also make IAF logistics team s%$t in their pants !!! I look forward to the day we have TWO AAMs, one a WVR short range IR and another a BVR active radar homing. One MICA with both would be really good
One upping everybody else :D : I look forward to the day when we have a single multi-spectral seeker on all AAMs. ARH/PRH for closing in and an imaging multicolor IR/Optical seeker for the endgame.
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Re: LCA News and Discussions

Post by Lalmohan »

any aircraft programme must have a huge amount of testing - safety is the most critical objective
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Re: LCA News and Discussions

Post by Nick_S »

That doesnt make much sense. Cant see why they would make 8 Mk.1 LSP when they will never land on a carrier. Perhaps its a typo.
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