Tejas Mk.1 & Mk.1A News & Discussions: 09 February 2018

[Haridas]

Rakesh,

It is from Line 1, but let us leave out this bit of the detail moving on.

Chetak sir,

You are absolutely right about how trained pilots and stupid pilots make a plane great or bad. There are so many instances from the Vietnam war etc. where the Yankee pilots could not believe what some of the Vietnamese were doing with the Mig-21s. Some flew straight into the hairs and others did things which startled the pilots.

Modern fighters though have a lot of aids. Tejas, like the Eurocanards, takes control over the plane recovers and hands it back to the pilot. Last year they were testing this autorecovery and seeing how slow can the Tejas fly. They found out that they were actually conservative. So they made changes to the flight computer to allow flying at even lower speeds. Both those speeds are much lower than what has been demonstrated in public.

More than one USAF fighters (plane and pilots) were saved by autorecovery feature. Good to know Tejas has it.

[Haridas]

As far as my knowledge goes it is not the maximum speed during a turn that is critical but the bank angle. No matter what the speed of the aircrfat - a bank angle of 60 degrees =2G. 8 G is a bank angle of approximately 83 deg

At any given bank angle - if the speed is increased, the plane will gain height, or if the bank angle is increased the plane will do a higher G turn.



Some information at this link
http://www.cfinotebook.net/notebook/aer ... erformance

one can definitely increase velocity at a given bank angle and not gain height, for exactly the reason you yourself exponded in the first sentence. So a pilot can certainly enter say 60 degree bank at 300kt and accelerate to 400 kt all the while keeping 60 degree bank, he does so by ensuring his AoA is such that the wing keeps giving same lift force. This happens day in day out with all pilots for example while banking on base leg to final approach the bank is kept constant while speed is allowed to bleed.

Otoh for aggressive sustained turn at high banking the a/c will be limited to the corner velocity. Proponents (designers ) of f16 amplified this aspect of close air combat (energy left after initial high ISR).
Jmt

[shiv]

So a pilot can certainly enter say 60 degree bank at 300kt and accelerate to 400 kt all the while keeping 60 degree bank, he does so by ensuring his AoA is such that the wing keeps giving same lift force.

In terms of physics there are two vectors - one "wing lift" causing the plane to turn and the other lateral - holding the altitude. If the plane accelerates it can maintain the same altitude ONLY in one of two ways:
1. Increasing bank angle
or
2. Keeping bank angle constant but using rudder to point he nose down so there is no altitude gain. That said - planes that can gain altitude in an accelerating turn are a powerful asset because they have all that extra energy for turn and climb.

The exact opposite is done (pointing nose up using rudder) in flypasts where the pilot flies at a 90 degree bank angle "knife edge". Here the only thing holding the plane altitude is lift from the fuselage and rudder because wing is banked 90 degrees. In this case the nose must be pointed up to maintain altitude and to offset the lift from the tailfin (behind the enter of mass) which would tend to push the nose down in a 90 degree bank fly-by

[Kartik]

Looking at SP-9 in primer and without its paint, I could see a few panels that are in yellow primer, which were grey earlier, like for example with SP3. See the panel next to the radome, the one behind the cockpit, as well as the panel near the base of the fin. Also the intake panel and the MLG door.

SP3



SP8



and SP9



What are these changes related to? Change in material?

[Neshant]

MK1A is on a tight timeline.
One more major slip up in deadlines due to engine, radar, software, mechanical issues and it could spell the end of the Tejas project and the entry of foreign single engine fighters.
It's not a good time to roll the dice on the Uttam radar.
Leave that for MK2.

The good part is that Uttam will have something to benchmark itself against.
Hopefully it will be better than the Israeli AESA when its ready.

[Haridas]

First, bank angle and "G" are as you outlined in the graph is for at equilibrium flight i.e. no slip. In such flight there is no force generated by rudder (rudder neutral)and the velocity vector is limited to local horizon plane. There is no two ways about it (i.e. it is Brahma satya).

So a pilot can certainly enter say 60 degree bank at 300kt and accelerate to 400 kt all the while keeping 60 degree bank, he does so by ensuring his AoA is such that the wing keeps giving same lift force.

In terms of physics there are two vectors - one "wing lift" causing the plane to turn and the other lateral - holding the altitude. If the plane accelerates it can maintain the same altitude ONLY in one of two ways:
1. Increasing bank angle

Wrong ; because it would be only true for a mythical manned plane (or hand crafted model planes where one would set elevator tab at fixed position) that always fly at constant AoA, thus factually incorrect for real manned plane that has live flight control.

Take as an example, all planes can fly 2 G (60 degree bank) level (i.e. on horizon plan) turn irrespective if their speed is 200 Kt or 500 Kt. It does that by ensuring only two things:

1. The flight control surface (e.g. aliron, rudder) maintain an aircraft wings banked at 60 degrees and velocity vector is zero degree incline w.r.t local horizon.
2. the wing generate total lift of 2.236 [bcoz Sqrt (2^2 +1^2)=2.236] times the aircraft weight.
A) This it does by setting the AoA of the wing at an angle that genrates the desired lift force (that of course is a function of air speed and wing's coefficient of lift). Thus for example at 200 Kt the desired AoA is 3 degrees, while at 500 Kt it needs to be only 1 degree.

Similatly a UCAV flying at 400 kt and 25 G level turn will be banking at nearly 90 degree.
Even my remote control plane flys similary under my active control on 60 degree bank irrespective of half power or full power (max speed).

I wrote reduimentary aircraft flight simulator that was validated against reference data, so I say the above based on expertise grounded in experience. It also helped to be born in a family where everyone around talks of and live by flying.

The exact opposite is done (pointing nose up using rudder) in flypasts where the pilot flies at a 90 degree bank angle "knife edge". Here the only thing holding the plane altitude is lift from the fuselage and rudder because wing is banked 90 degrees. In this case the nose must be pointed up to maintain altitude and to offset the lift from the tailfin (behind the enter of mass) which would tend to push the nose down in a 90 degree bank fly-by

Look closely at any knife edge maneuver, the rudder is generating negative lift (not positive as you assert above) while fuselage is generating positive lift.

[SiddharthS]

If it is possible to build the one or two Mk1a squadron without the radar and then refitting them with Uttam afterwards, then hey should do it. Kind of similar to the F-35; concurrently developing and inducting the fighter. There maybe fears of Mk1a getting mud thrown at it by the usual suspects, but once the fourty Fighters start getting airborne regularly the noise will subside. Yes they will try their best to undermine the project but the effect of it will not be as substantial as it was in pre 2017.

The scientist will get good experience and expertise by building 83 Uttam radars, and most importantly they will get funds to develop the next iteration of it for Mk2. Building 283 radars and operating them would give immense experience and knowledge to the scientist, which then can be use to develop far more sophisticated version for AMCA. With the AESA radar, Mk1a will be one of the most attractive fighter in the light category not only for the IAF but even for other countries. And indigenous AESA would mean no road blocks in exporting Mk1a to israel-hating islamic countries.

[shaun]

MK1A is on a tight timeline.
One more major slip up in deadlines due to engine, radar, software, mechanical issues and it could spell the end of the Tejas project and the entry of foreign single engine fighters.
It's not a good time to roll the dice on the Uttam radar.
Leave that for MK2.

The good part is that Uttam will have something to benchmark itself against.
Hopefully it will be better than the Israeli AESA when its ready.

Progress as of now(news available upto aero india 2017 in month of february.)

Specifications:
To have around 700 TRMs
150Kms detection range for a 2sqm target
Search upto 100 targets, track 20 and target 6.
Weight of radar unit to be around 110Kgs
To be GaAs based
Three prototypes operational as of now, three more to be added by the end of this year.
Software coding for all modes including A2A, A2G and SAR completed.
Ground tests completed.
Has also been flight tested on a helicopter test bed using a smaller TD
Cooling requirement of 3.6KW.
GaN for next gen successfully inititated
LCA LSP 2 is leased to LRDE for testing UTTAM radar.

[Rakesh]

Surya Saar, I need to update page 1 of this dhaaga. That is why Sorry!

Line 1 as per one of the post by Indranil saar!!
Link

Thank You Saar!

Rakesh,

It is from Line 1, but let us leave out this bit of the detail moving on.

Page 1 of this dhaaga updated. That list looks beautiful, especially the SP list

[ramana]

Shaun, Thanks for the summary. And it's about a year old, being from Feb 2017.

From Arjun thread

Talking about the next version of the Tejas, called ‘Mark1-A’, Dr Christopher said: “The design other than the AESA radar and the jammer pod is complete.”

Hindustan Aeronautics Limited is looking to import the AESA radar even as DRDO made a radar that will be tested next month. The IAF is looking at 83 ‘Mark1-A’, with 59 improvements over the existing Tejas.

The Indian Air Force has projected a need for 324 fighter jets over 15 years and has officially indicated that it needs the ‘Tejas Mark 2’ (medium combat aircraft). It will carry a more powerful engine and weigh almost 20 per cent heavier than Tejas.

[shiv]

The exact opposite is done (pointing nose up using rudder) in flypasts where the pilot flies at a 90 degree bank angle "knife edge". Here the only thing holding the plane altitude is lift from the fuselage and rudder because wing is banked 90 degrees. In this case the nose must be pointed up to maintain altitude and to offset the lift from the tailfin (behind the enter of mass) which would tend to push the nose down in a 90 degree bank fly-by

Look closely at any knife edge maneuver, the rudder is generating negative lift (not positive as you assert above) while fuselage is generating positive lift.

That is exactly what I have said. Nowhere have I said positive lift from rudder. I have said that the lift provided by the tailfin (not rudder) must be counteracted by using rudder (to provide negative lift) so the nose is held up. Tailfin is not rudder

Exactly as in this image - which is a true-blue knife edge:

[shiv]

Take as an example, all planes can fly 2 G (60 degree bank) level (i.e. on horizon plan) turn irrespective if their speed is 200 Kt or 500 Kt. It does that by ensuring only two things:

1. The flight control surface (e.g. aliron, rudder) maintain an aircraft wings banked at 60 degrees and velocity vector is zero degree incline w.r.t local horizon.
2. the wing generate total lift of 2.236 [bcoz Sqrt (2^2 +1^2)=2.236] times the aircraft weight.
A) This it does by setting the AoA of the wing at an angle that genrates the desired lift force (that of course is a function of air speed and wing's coefficient of lift). Thus for example at 200 Kt the desired AoA is 3 degrees, while at 500 Kt it needs to be only 1 degree.

This is obviously 100% right.

Please do not forget that my original post was about turning in response to a query about turning, and not about flying level at 60 deg bank angle. Let us stick to turning - which requires banking. I hope you have read the start of the discussion. The question was if higher speed will result in higher turn rate. Here is the post that you responded to:
viewtopic.php?p=2260895#p2260895

Earlier you said:

So a pilot can certainly enter say 60 degree bank at 300kt and accelerate to 400 kt all the while keeping 60 degree bank, he does so by ensuring his AoA is such that the wing keeps giving same lift force.

What you are saying is that if the plane increases speed from 300 kt to 400 kt while maintaining 60 degree bank angle the lift necessary to keep the plane flying level with no ascent or descent requires adjustment of the AoA.

Whether a plane is banking or flying level, any increase in speed from 300 kt to 400 kt will increase lift provided by the wing. At a fixed 60 deg bank angle while turning such an increase in speed would normally tend to cause the plane to gain altitude unless adjusted in the way you have stated. You have stated that the adjustment is made by changing the AoA to generate "the desired lift force". This is Brahm-satya again from you. But the "adjustment" required of the AoA would have to be a decrease in the AoA (while maintaining bank angle 60 degrees). That would make the turn radius at 400 kt bigger than the turn radius at 300 kt.

What would the pilot have to do to keep the turn radius at 300 kt and 400 kt exactly the same while maintaining a 60 degree bank angle and keeping altitude constant without ascent or descent?

[ramana]

Rakesh, If you do a timeline for each assy line, it ccould show interesting facts.

[Haridas]

Look closely at any knife edge maneuver, the rudder is generating negative lift (not positive as you assert above) while fuselage is generating positive lift.

That is exactly what I have said. Nowhere have I said positive lift from rudder. I have said that the lift provided by the tailfin (not rudder) must be counteracted by using rudder (to provide negative lift) so the nose is held up. Tailfin is not rudder

Exactly as in this image - which is a true-blue knife edge:

Firstly rudder is the mechanism that sets fins aerodynamic configuration that results in force, the rudder surface has tiny/negligible contribution to the net force. Thus rudder does not conteract tailfin (as you say), it is the controller/driver that forces tailfin to operate in intended way. Tail fin function is often interchangeably callled as rudder or tailfin/vertical stablizer (as I have used in my statements too).

Secondly your as written sentence

Here the only thing holding the plane altitude is lift from the fuselage and rudder because wing is banked 90 degrees.

does indicate to a lay reader that you are referring to lift from both fuselage and tailfin (and not lift from faselahe and pulldown/negative lift from tailfin) which obviously is wrong and my effort to point that out.

BTW the nice pic you posted nicely shows the up_rudder orienting the tailfin to set fuselage in desired nose above horizon attitude to generate body lift.

[Haridas]

Take as an example, all planes can fly 2 G (60 degree bank) level (i.e. on horizon plan) turn irrespective if their speed is 200 Kt or 500 Kt. It does that by ensuring only two things:

1. The flight control surface (e.g. aliron, rudder) maintain an aircraft wings banked at 60 degrees and velocity vector is zero degree incline w.r.t local horizon.
2. the wing generate total lift of 2.236 [bcoz Sqrt (2^2 +1^2)=2.236] times the aircraft weight.
A) This it does by setting the AoA of the wing at an angle that genrates the desired lift force (that of course is a function of air speed and wing's coefficient of lift). Thus for example at 200 Kt the desired AoA is 3 degrees, while at 500 Kt it needs to be only 1 degree.

This is obviously 100% right.

Please do not forget that my original post was about turning in response to a query about turning, and not about flying level at 60 deg bank angle. Let us stick to turning - which requires banking. I hope you have read the start of the discussion. The question was if higher speed will result in higher turn rate. Here is the post that you responded to:
viewtopic.php?p=2260895#p2260895

Sure. However your argument only mentioned bank angle (G's) and stopped there and said nothing about how that relates to angular rate (angular velocity / turn rate) Or turning radius.

[Haridas]

Earlier you said:

So a pilot can certainly enter say 60 degree bank at 300kt and accelerate to 400 kt all the while keeping 60 degree bank, he does so by ensuring his AoA is such that the wing keeps giving same lift force.

What you are saying is that if the plane increases speed from 300 kt to 400 kt while maintaining 60 degree bank angle the lift necessary to keep the plane flying level with no ascent or descent requires adjustment of the AoA.

That's correct.

Whether a plane is banking or flying level, any increase in speed from 300 kt to 400 kt will increase lift provided by the wing. At a fixed 60 deg bank angle while turning such an increase in speed would normally tend to cause the plane to gain altitude unless adjusted in the way you have stated. You have stated that the adjustment is made by changing the AoA to generate "the desired lift force". This is Brahm-satya again from you. But the "adjustment" required of the AoA would have to be a decrease in the AoA (while maintaining bank angle 60 degrees). That would make the turn radius at 400 kt bigger than the turn radius at 300 kt.

Where did I assert that turning rate is determined by bank angle alone?
I guess you have to make that connection as to what else apart from bank angle makes an aircraft turn harder!

What would the pilot have to do to keep the turn radius at 300 kt and 400 kt exactly the same while maintaining a 60 degree bank angle and keeping altitude constant without ascent or descent?

Good question. Trying to answer this will lead to the implicit fallacy in the reasoning.

[JayS]

Looking at SP-9 in primer and without its paint, I could see a few panels that are in yellow primer, which were grey earlier, like for example with SP3. See the panel next to the radome, the one behind the cockpit, as well as the panel near the base of the fin. Also the intake panel and the MLG door.
<snip>

What are these changes related to? Change in material?

I was also wondering why some panels are painted while some others are not at the first flight stage. May be its supplier based..? Do they repaint all of them again..?

[Indranil]

None of them are painted. Some have the primer on and others not. Final painting happens at HAL.

[shiv]

Where did I assert that turning rate is determined by bank angle alone?
I guess you have to make that connection as to what else apart from bank angle makes an aircraft turn harder!

I believe you have misunderstood my post and the original point of the discussion. The original question was whether a given aircraft can turn harder (i.e a tighter, smaller radius turn) when it is flying faster. IMO the answer is no. If your view differs from this please say so.

What would the pilot have to do to keep the turn radius at 300 kt and 400 kt exactly the same while maintaining a 60 degree bank angle and keeping altitude constant without ascent or descent?

Good question. Trying to answer this will lead to the implicit fallacy in the reasoning.

This question came up because you came into the discussion saying that the same bank angle could be held even as an aircraft accelerates. I was unable to understand what connection this has with the original question of speed and turning radius, hence I applied your example to the original question for clarity. If you have an answer to this question please post. Or else maybe someone else can take a shot at it?

[JayS]

Is there a term corner velocity to indicate the speed at maximum sustained horizontal turn rate? Higher the better

This is where non delta large motor planes like f16 are said to excel though canards may help some

Corner velocity is the point in flight envelop, which represents lowest speed at which the fighter can pull highest rated G without damage. The corner point correlates to ITR. STR comes at lower speed, and Gs. At corner speed you turn fastest but bleed energy too. So you cannot hold it beyond a few seconds, lest you will lose altitude rapidly. Also, typically tightest turn (smallest radius) comes at even lower speed and G.

https://goo.gl/images/cv2yyA

This image shows schematic of the turning envelop at a certain altitude. The ITR point in this is same as corner speed. But the image has bad resolution.

Following image is of flight envelop of kfir.
https://goo.gl/images/hTUQTN

unfortunately they do not have sea level plot. Since the image has hard limits, clipping the full envelop, it may be little difficult to see all the things here. Let me try to explain. Beyond the 1000ft radius line there would be a stall curve. The minimum radius turn is the radius line tangent to stall line there. It would be lower than 1000ft in this case. On top side there would be a crown on this stall curve, which is clipped. It would peak at max allowed G limit. A horizontal line just tangent to the peak would mark, at the point of tangency, the max AoA, max G, max ITR and lowest speed at which thisi s possible i.e. Corner velocity.

Also note the Ps lines. The Ps=0 line gives STR at various speeds. The max turning rate on that line is max STR. Anything above that and you bleed energy. Anything below and you have excess thrust available to climb or accelerate.

This is all from Energy Maneuverablility theory and so there is no price for guessing that F16 fares well when seen from this perspective.

PS: First image seen with better resolution here: http://john-golan.blogspot.se/2015/08/a ... nergy.html

[JayS]

Where did I assert that turning rate is determined by bank angle alone?
I guess you have to make that connection as to what else apart from bank angle makes an aircraft turn harder!

I believe you have misunderstood my post and the original point of the discussion. The original question was whether a given aircraft can turn harder (i.e a tighter, smaller radius turn) when it is flying faster. IMO the answer is no. If your view differs from this please say so.

What you said here, is a good general rule to follow for all practical purposes. But if you see some Turning flight envelop charts, depending on initial conditions (speed, AoA and altitude) and type of aircraft, some aircraft may be able to fly tighter with increase in speed. But the part where its possible to turn tighter with higher speed it on lower speed/G side of the envelop and very close to stall line and is typically narrow in terms of speed range.

[Haridas]

JayS: thanks for the links and clarity.

[ramana]

Guys all this aerodynamics is interesting, but what does it have to do with Tejas which is now a production follow up.

[Trikaal]

Uttam radar still has almost 2-3 years for certification if it is to be included in Tejas Mk1A as I don't expect deliveries to start before 2021-22. However, Mk1A deliveries should not be linked with Uttam development. What could be done is equipping 50% of the Mk1A with Uttam as that will give a cushion of another 2-3 years for radar development.

[fanne]

Radar and a family of A-A missiles to go with it. Now that we have the basic Astra, many versions of it should be tried, lomger range, dual/triple mode, long range IR (with mid course correction) etc etc. They can all be first tried in SU30MKI (as we have the radar code to integrate) and then later integrated with Uttam.

[ramana]

^^Trikaal, Dr. Christopher says the UTTAM is ready for trials this year. And that HAL is negotiating with outside suppliers for the radar.

I think this is good move for two reasons:

- If UTTAM is successful no need for the imported radar.
- The prospect of UTTAM coming will drive the price of the import radar so as to secure orders.

Most likely your approach will happen as program protection.

Early Mk1A s will have the import radar with option to buy further while the UTTAM completes development and is ready for production. The contract for the radar will give us an insight on how successful the UTTAM is going to be.

[Rakesh]

https://twitter.com/SJha1618/status/977835287123505152 ---> Let me qualify this. This is what some of them want. But even I don't think, it'll happen given that the AESA hasn't made it to a test vehicle. Development work remains.

https://twitter.com/SJha1618/status/977808756594610176 ---> Based on my discussions with people in the 'Tejas community' it seems increasingly likely that MK-1A production may begin with the 21st HAL series production unit itself.

[Trikaal]

Forgive me for saying but 'being ready for trials' in India usually means a testing period of atleast 2-3 years. Which is fair, since a lot of tests need to happen and we test our products quite extensively. Incase Uttam fails even 1 of these tests, it would mean a delay of another couple of years.

Uttam is a very good development towards our self reliance, no doubt. But I don't want Tejas to be delayed anymore because of radar. I have a similar opinion on the uprating program for Kaveri engine.

HAL and GOI are very obviously dragging their feet on radar orders to give ample opportunity to Uttam to mature. This has been the attitude since we were denied EL-2052 radar by the USA.

[ramana]

I was going to do a summary with the link. Its quite late now.
Please do the honors. Here is the link.


http://quarryhs.co.uk/modern_fighter_gu ... veness.htm

Thank you, Ramana. Let me take a look at it. But would love to see your views as well.

There is only one gun station in the Tejas.
Keeping that in view the GSh 23 is best option based on total destructive power against aircraft.
The 30mm has less overall power and is handicapped by slow rate of fire. And potential recoil forces.
It might be better for ground attack but then bombs and missiles that Tejas carry are much more effective.
Table 2B excerpt:

GSh has gun power of 1728 vs 1470 for 30mm

[Cybaru]

https://twitter.com/SJha1618/status/977808756594610176 ---> Based on my discussions with people in the 'Tejas community' it seems increasingly likely that MK-1A production may begin with the 21st HAL series production unit itself.

Won't this require reasonable amount of testing? I guess perhaps a lot depends on what is being changed. I hope they test it thoroughly and they do add a 150-300 kgs of more fuel as well!

[SaiK]

I'm reading it as Uttam design is done, and the previous version of INDIGENOUS radar will be tested next month.

[kit]

Apparently, the UTTAM is a scaleable beam radar similar to the NORTHROP GRUMMAN SABR meaning it can be modified and upgraded (more TRMs increased range) to fit different platforms .. hugely significant for Indian military

[JayS]

Apparently, the UTTAM is a scaleable beam radar similar to the NORTHROP GRUMMAN SABR meaning it can be modified and upgraded (more TRMs increased range) to fit different platforms .. hugely significant for Indian military

Isn't any AESA radar scalable by its very nature..???

[Singha]

within the limits of its back end processor, power supply budget and cooling system - yes .... some growth margin will be there to accomodate more txrx modules.

[brar_w]

Scalable architectures can be applied to all those things as well just like it is to the antenna and as is the case in some radars being developed for other applications.

[Zynda]

My impression was that our FCR tracking alogs especially in A-G mode were lacking and thus the struggle. Hardware wise it seems like were OK.

[ragupta]

zeenews has a show on Tejas, it is currently on. The recording was done a day before sp-9 flight, they show the building of sp10 in the same hanger.
the empty weight mentioned is 6.5t and weapon 3.5t. 10 month to build one plane from start to handover.
12000 total parts to assemble.

[ragupta]

They showed the cockpit, mentioned it to be the most advanced among all the fighters that IAF flies today. the m2k was the basis and inspiration for LCA, that had analog controls, Tejas is completely digital.

[Rakesh]

Thank you for this ragupta. Kudos to the French (Dassault) for the M2K design. They built a beautiful plane, which we made even better in almost every respect.

[ramana]

zeenews has a show on Tejas, it is currently on. The recording was done a day before sp-9 flight, they show the building of sp10 in the same hanger.
the empty weight mentioned is 6.5t and weapon 3.5t. 10 month to build one plane from start to handover.
12000 total parts to assemble.

ragupta, thanks for this awesome update.

This is good info. We can then lay out a schedule for the following SP11 thru SP 20 and then the next tranche.