Bharat Rakshak

I see from the link that the last zero is a symbol for degrees.. just for a moment thought someone breached absolute zero

By this I think they may get the melting point of whole airframe.

I conclude that Boeing is slightly better than HAL.

Below Aboslute zero?

Dear Kersi D-ji,
Please enlighten HAL on how to manufacture aircraft with your expertise. And how to ramp up production.
And give a brief outline here on how HAL can do better .


Maybe last time around, when you had criticism for HAL ( and an overwhelming urge to misuse and rape the poor smileys ) , you were not given a chance proper.
This time around, we will ignore your fondling of smileys BUT please enlighten us and stupid folks at HAL!
All ears !
Go !

I think it is the article editing issue or they are experimenting the whole gear box in Liquid nitrogen..

.

someone from BRF reads idrw too.
we are not amused !

Contract soon for Derby
Israeli Derby to be Prime BVRAAM for Tejas MK-1

Interesting things in the article


So Astra might be fired from the Rambha by mid 2013(given we have to add minimum 1 year to what DRDO says)




FWIW good part is that R-73 has been successfully integrated, worrisome part is force is not happy with it on tejas and now wants python-5, hope this is not another reason to delay induction. Also curious why wasnt R-77 selected for the BVRAAM

Derby BVRAAM is the natural choice , since without BVR missile integration into Tejas , IAF will not accept them in to forces and will not grant FOC which is scheduled for 2013 .

R-73 was first test fired from Tejas in 2007 , Good five years back ,either they want a new Generation missile like Python-5 or are not happy with the test results achieved with R-73 , if i am not wrong both have similar range .

Just a thought, all the a/c's mentioned here have tails, while LCA is tailless. Tails should help counter any asymmetric moment applied by air brakes.

M2000 has air brakes on the wings i guess.

Gurneeshji,

How does it mater if your elevator (pitch control device) is placed as a separate tail or part of the wing? If you can pitch down, you should be able to compensate for the un-commanded pitch-up due to activation of the airbrakes. This was the expectation from the FBW. However, they found out that they cannot completely mitigate this.

Why, even I would love to know the reasons . But it is certainly not because the elevators are not arranged as part of the tail. One suspected cause could be that the processing is not fast enough.

This is a callout to a poster here named Rajeev Chandramohan ... He is an expert on controls ... Unfortunately, people here scoffed him off even though he was proven right later ... I hope he reads this and provides his take on this.

There is no some issues that surfaced recently as reported.

Due to limitations in turn rates of LCA in this current version which has direct bearing in WVR fights, a more robust missile than R-73 is selected which compensates for the shortcomings in turn rates.

Further, this was already hinted by ADA Chief long back.

While comparing Tejas air brake with F-18 and other planes do you see any difference with Tejas air brake and others?

Feb 22nd in a week feb will end when will jingos be khush ??

I think HAL is toying with us

python5 per wiki is exactly same weight as R73 - 105kg , similar range, about 5 inches longer and much modern missiles .... a good choice imo for entire iaf fleet to replace the r73 once the stocks expire.

unlike r73 it does not use TVC, but has 18 small control surfaces.

Kartik - My point was using a simpler design philosophy of keeping the airbrake closer to CoG.

Discussing the other aircraft is immaterial, because their design considerations were different. Shouldnt using a simpler design process help when we're doing it for the first time?

FWIW, the Super Hornet pylons create drag and reduce range significantly, and I heard they introduced wing fences on the G model.

And the 40 orders are due to non fulfilment of basic parameters like STR & AoA rather than uncommanded pitch.
These 40 orders represent more than 5% of the authorized IAF fighter strength, and IMO significant, given that basic parameters have not been met

Suryag - When DRDO/ADA took up a more complex design path. and rejected Dassault's analog FBW that was deficient to the digital FBW, that is when IAF withdrew because it believed DRDO/ADA was using a more complex means to achieve relatively simple ends. IAF agreed that Dassault FBW was not state of the art, but believed that it was proven, and would have mitigated development risk. Fears were proven true when LM held back the CLAW software code after 1998.

Indranil - your assessment is close, I spoke to a INAS 300 engineer who thinks on similar lines. INAS 300 is slated to replace its Sea Harriers with the Tejas in future.

Lastly, MiG-21 and F-104 Starfighters were supersonic bomber interceptors of the 50's and 60's. IAF purchased them to shoot down Pakistani airfield attackers and escort our strike forces. Before MiG21, both scenarios were the highest cause of IAF losses. Landing speed is high for that family of aircraft with high wing loading and small wings, and pilots know these characteristics.
Landing speed became an issue when IAF started using MiG-21 as a trainer. For rookie pilots, it was not ideal.

Having said that, how many MiG-21 have been lost on landing? I dont have the numbers, but they're few in between. So MiG-21 landing speed high was a known factor. FWIW, the aircraft it was supposed to counter - Pakistani F-104 - had higher landing speeds.

Lastly, I am saying this because we needed the LCA yesterday. We need LCA in numbers. We dont fight limited wars like US & Europe, wherein when the game goes tough, they go home. Our wars are existential in nature. Fighters like Rafale/Eurofighters will not be cheap to mass produce. We dont have the luxury of indefinite time or money like JSF.

I have just one input here ... I will just stick to the position of the airbrakes alone and not discuss the design philosophies and goals set for the LCA.

The designers must have tried to place the airbrakes near the CG, but could not find the space for the it. If there would have been space, they would have promptly moved it now. But the fact that they still cannot manage it, shows space constraints.

Also, I like the concept of using MLG door as air brakes. Saves space and weight!

The LCA is designed to be unstable in pitch with a tendency to go nose up - a factor that is compensated by fly by wire. For a plane that is designed to go nose up and be unstable, the CG has to be aft of where you think it should be.

Now how are the aeronautical geniuses of this forum concluding that the "uncommanded pitch up" - 3 words in some article means that the air brake is too far aft of the CG? If you don't know where the CG is how the hell can anyone judge that? To me that is the height of speculation.

A doctor who speculates on with no real facts in his hands would be a quack.

Makes a whole lot of sense. Hopefully this will speed up radar trials and weapons testing.

Shivji,

How many jalebis do you want to bet on the fact the airbrakes are behind the CG?

I have absolutely no doubt that there is a pitch up moment if the airbrakes are applied ... How much it can be (or is) compensated is something we will never know.

tsarkar ji, doors of the main landing gear were used as air-breaks in Gnat as well. And when they say MLG (two at the back), it doesn't mean that the whole wheel will be extended. Only the doors will be opened.

Its a novel idea I say. If the Brits can do it, why can't we?

Also as suggested by other's too, we have inducted far deficient planes in the past. Even when porki Bundar was inducted it could not fire BVR or PGM. Still they ordered 250.

When we ordered 150+ ALH, we didn't started receiving MKIII version right away.

So how do you know what the design considerations were that made the LCA designers place the airbrake further aft of the CG? You just assumed that they didn't have common sense when placing it there..and then when pointed out that its common enough to have the airbrake placed far aft of the CG, you just brush it away with the statement "their design considerations were different". What was different about their design considerations?

What does the second statement even mean? What is a simpler design process?



What has that got to do with the airbrake location on the vanilla Hornet?



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. The F-35 apparently doesn't meet its STR requirements, but is the USAF now insisting that the F-35 purchase be curtailed to a token order?



You're repeating stuff that's been discussed to death before. Whatever that decision did, the FBW is not an issue as of now. It is mature and hasn't proven to be troublesome. it may have added 3 years to the first flight date, but that isn't the reason that the IAF is keeping Tejas Mk1 orders to 40.



Without knowing the numbers, how can you say that they're few and far between?

Logically speaking the CG should be within the footprint of the MLG else the AC will be prone to tipping over to the heavier side while taxiing.

Kartik writes:

"Without knowing the numbers, how can you say that they're few and far between?"

Exactly. Its well known that a lot of the troubles with the MiG 21 are in this phase.



http://www.dnaindia.com/india/report_mi ... ef_1596427

Case in point:
http://www.tribuneindia.com/2011/20111008/nation.htm#1



The claims of CG etc by visual inspection are quite humorous. Next I guess LCA designers will be stoopid because they did not put the correct coat of paint on the aircraft. The correct paint being decided on whatever paint one likes or decides some other aircraft has.

And this:



Well said as before. The ADA/DRDO did not choose the French option because they did not share adequate data and attempted to tell the assembled scientists that their questions were pointless as the decision would be political and they'd win anyhow. That cost them the bid. The Germans actually impressed the Indian team the most with their transparency and technical understanding, but they did not have a working system and hence the US, which fell in between these two comparisons, actually won out. All this is well documented by the ex NAL gent who actually began the LCA program.

Some thing like ...............?

^^^

Hahaha! That looks funny.....but in this case it tipped over due to the thrust from the B1B which was taxiing....

sounds like fbw roll control won't happen on ground!

As far as my amateur information goes, the center of mass ("CG") of an aircraft coincides with the center of lift in a stable aircraft. In an unstable one the center of mass is behind the net center of lift, the aircraft will tend to pitch nose up.

So far so good.

If on a stable stable aircraft if you introduce an air brake dorsally exactly above the center of mass what effect would it have on pitch? According to the theory introduced on this thread, it should not cause pitch up or pitch down, because the brake coincides with the center of mass. is this correct? Not necessarily because the air brake is situated dorsally and there is a force acting dorsal and above the center of mass and no compensating force acting ventrally. So the nose should pitch up.

The only way this can be avoided is to put the dorsal air brake slightly forward of the center of mass.

But consider the same situation if there are two lateral (side) air brakes at exactly the same level as the center of mass. The brakes are neither above, nor below, but exactly on the left and right. Deploying these air brakes should have absolutely no effect on pitch. They could cause a yaw if they were asymmetrical. In fact, lateral air brakes such as the ones the LCA has should have no effect on pitch whether they are forward or aft of the center of mass.

So what facts are we left with
1. Fact: LCA is stated has having uncommanded pitch up when the air brakes are deployed
2. Fact: the LCA has lateral air brakes, not ventral or dorsal
3. Fact: We have no idea where the center of mass of the LCA is situated.

Under the circumstances it would be impossible to assert that the uncommanded pitch up of the LCA on deploying air brakes is because the air brakes are too far aft.

There is no connection between the known facts and the conclusion.

That is not a fact.

How dare you!!!


You mean this

^^^ you are welcome koti ji



wow.. best pic of LCA. Beautiful.

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.

THe pitch up or down depends on whether the airbrakes are on top or bottom rather than aft or front.

Then there was the problem of uncontrolled pitching problem even during the first taxi trials..they were trying to correct it. This is what my chaiwala classmate told. I am not in touch with any of them for clarification. Those in the loop may be able to clarify.

On the ground the CG is practically over the MG. Reason being you need a stable AC on ground but also you want it to be easy to rotate @ V2.




I am going OT and repeating what has been said on this forum before. center of lift coinciding with CG means neutrally stable aircraft like a metal ball laid over a table. At the moment it is stationary but will start moving if disturbed. Stable aircraft means center of lift behind CG aka nose heavy much like the same metal ball inside a notch on the table. If disturbed, the ball will oscillate with damped amplitude and will come to rest eventually.

Why not have symmetrical air brakes i.e. dorsal/ventral pair much like the F-16 arrangement at the tail or use MLG doors along with those dorsal air brakes?

Cheers....

What is the WVR missile we are planning for Upg Mirage and Rafale. Don't tell its Matra's Magic 2.
Also, can anyone point to the cost of the Python 5?

formatting disaster, self deleted

Any aeronautical engineer, or for that matter any mechanics student who has read Ferdinand L Singer will confirm that the moment arm created by the airbrake not aligned with the CoG causes the pitch up.

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.

Agreed. However, the MLG doors do not just provide aerodynamic housing, but also protect the LG from the elements in flight. The 737 doesn’t have MLG doors, but the LG is designed for this. I was told moisture ingestion and icing of LG moving joints/parts as one of the possible side effects, if the aircraft flew into clouds and extended LG door.

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.

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.

F-35 is worst aeronautical disaster in history and political pork barrel. Should we be going down the same route? What can one expect when Business Men / Managers / Politicians and their coterie run programs rather than engineers and aviators driving development.
Then why can’t the FCS correct the uncommanded pitch created by the original airbrakes.

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.

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.

If you or I were to teach our young ones to drive using a Ferrari or a Shaktiman, I am sure they would not be able to handle the acceleration of the former and the momentum of the latter. Should we then say, “troubles with the Ferrari are in the acceleration phase” and “troubles with the Shaktiman are in the stopping phase” because we’re using them for a purpose they were never intended for?

Flying Officers just start OC flying. How many FLt or Sq Ldr or Wg Cdr crash while landing because they couldnt handle the landing speed, which all supersonic fighters of that era with high wing loading will have?

FWIW, Pakistani F-7 OC training crash rate is the same as India.

Issues with MiG-21 as an OC trainer is meaningless while discussing Tejas as a fighter.

Lastly, the reason I am saying all this is because of the misdirected angst against the user, who are doing all they can to support the program. But a basic performance level has to be met.

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.

Sarkar san,

With all due respect, stop being so melodramatic Can the mig21 outfight the Pakistani F16? We still have more than 150 of those flying around, dont we?

Also, can I turn the question around, and ask - if your son or father or brother or husband needs lifesaving medicine, (or clean drinking water, or a working toilet, or access to a school), would your rather spend the money on a foreign fighter plane, so the IAF pilot has the best of the best plane to fly? Afterall, the life of every citizen is important..

Even an LCA MkII will end up costing less than 35-40 million dollars each, when we are going to pay 80 to 100 million dollars for a Rafale.

Its the job of our soldiers and sailors and airmen to put their lives on the line. For this we are eternally grateful to them. But lets not attach such a great significance to an individual life, that we loose sight of our strategic goals.