Indian Military Aviation - 21 Sept 2015

Kartik
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Re: Indian Military Aviation - 21 Sept 2015

Postby Kartik » 18 Jun 2016 03:42

indranilroy wrote:
1. It has been some time since I have seen a military trainer with so many control rods sticking outside. These days one sees them only for trim tabs.
Image


So many? Where are you seeing them? I don't see them for the rudder, but only to the trim tabs..something similar is visible on the AT-6 II Texan as well..

2. It looks like they stitched together the canopy from some existing line. This allowed them to get to the flying prototype ASAP. A fantastic decision, if you ask me, but it robs the canopy of a smooth continuous curve. In terms of performance, it will probably not matter much, especially that of a BTT. However, it will be interesting to see if the production models have this.


yes, it does appear to be a little dis-jointed and not a flowing curve indicating that it was probably made in 2 pieces and joined at the frame. Later prototypes may see a one piece canopy with the support frame. But it will make almost no difference to the aerodynamics/drag.

3. I am sure that MLG and NLGs doors will come soon. HAL has stuck to the layout of the wheels placed inside of the MLG strut, same as in the HF-24, Kiran and the IJT. This layout requires shallower wells in the wing to store the retracted struts, but deeper wells in the fuselage for the retracted wheel. It makes sense in an HF-24 with thin wings, but not so much on a HTT-40 with thick wings.
Image


Interesting observation..I did notice the wheels were placed inside but didn't relate it to existing HAL designs. If they used something similar on the Kiran and IJT and found no issue with it causing the wheel well being a little deeper, they most likely won't change anything on HTT-40 either.

This layout also removes the option of the wheel with a hubcap forming the conforming surface (like in the 737s or the Grob G120) and its accompanying weight savings.
Image
Image

But then, the Kirans seem to have done fine with this layout and no covers for the wheel well at all.
Image


On the 737, the hub cap forming the wheel door is only because it is absolutely flush with the rest of the wing. Otherwise, this is a definite drag riser. On the Kiran I was initially surprised that they haven't bothered to put a hinged wheel well cover door to completely close the gap. Negligible weight increase but a definite drag reduction is what I thought, till I found another pic of the Kiran that shows that the wheel well into which the tyre fits upon retraction, is very shallow.
Image

The strut itself is covered by a panel that is attached to it and covers it upon retraction.

We're likely to see some changes on this aspect of the HTT-40.

4. Another adverse effect of this layout is that it decreases the distance between the two MLG wheels which is unfavourable for austere field and cross wind performance.

5. On the other hand, the NLG hinged near the nose increases the distance between the NLG and the MLG wheels which positively affects the performance in the aforementioned criteria. This is also a welcome change in layout from the preliminary design.
Image


MLG wheel base (distance between MLG tires) must have been calculated keeping in mind the inside half placement of the wheels. Not sure if the additional inches of wheel base one would gain by placing the wheels on the outside of the strut would make any major difference to the stability of ground ops and cross wind performance.

Agreed on the wheel track improvement with the placement of the nose gear further forward and retracting backwards into the fuselage.

6. The landing gears are also long providing the aircraft a higher stance useful for austere field performance, ease of maintenance and weapon loading.


Agreed. Definitely to allow for centerline and wing drop tanks and weapons to be loaded.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Kartik » 18 Jun 2016 03:46

indranilroy wrote:HAL seems to have given a dekho to the journalists of its IJT hangar/assembly line. When will it be set up at Kanpur?

Image

Image


Where are those strakes that were mounted just below the canopy, aft of the nose, gone?

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 18 Jun 2016 04:05

They were gone long time back. So were the wing fences. Instead they used vortex generators on the outside of the wing, ahead of the aelirons. they seem to have gone as well.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 18 Jun 2016 04:07

Kartik wrote:
indranilroy wrote:
1. It has been some time since I have seen a military trainer with so many control rods sticking outside. These days one sees them only for trim tabs.
Image


So many? Where are you seeing them? I don't see them for the rudder, but only to the trim tabs..something similar is visible on the AT-6 II Texan as well..


How many trim tabs does the HTT-40 have? 2 on rudder, one each on each elevator?

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 05:07

indranilroy wrote:
5. On the other hand, the NLG hinged near the nose increases the distance between the NLG and the MLG wheels which positively affects the performance in the aforementioned criteria. This is also a welcome change in layout from the preliminary design.
Image

6. The landing gears are also long providing the aircraft a higher stance useful for austere field performance, ease of maintenance and weapon loading.

7. I don't know if it is a facet of the plane just starting its flight testing, but I am a little surprised with the amount of flap deflection on the take off roll.


The nosewheel may have got fried in the exhaust in the old configuration with the new TPE 331 engine. There seem to my eyes to be several deliberate design features to ensure that exhaust gases affect the MLG only minimally if at all. The topic should not have come up at all after one glance of the first flight. But then again all our judgements come from a few images of 2 flights

I wonder if flap deflection is a Bengaluru special - 900 m AMSL and hot days. I grew up being taught that the T in NTP is 20 deg C. I need a jacket at 20 deg C. and Bengaluru is cooler than the rest of India in June with day temperatures of 28-32 deg C

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 18 Jun 2016 05:28

shiv wrote:The nosewheel may have got fried in the exhaust in the old configuration with the TPE 331 engine. There seem to my eyes to be several deliberate design features to ensure that exhaust gases affect the MLG only minimally if at all. The topic should not have come up at all after one glance of the first flight. But then again all our judgements come from a few images of 2 flights

Have to disagree. I am a 100% sure that the nose wheel would have been below the plume.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 05:32

Shorts Tucano - regarding "finish"

Lovely shiny paint but plenty of dents and imperfections

Image

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 05:38

indranilroy wrote:
shiv wrote:The nosewheel may have got fried in the exhaust in the old configuration with the TPE 331 engine. There seem to my eyes to be several deliberate design features to ensure that exhaust gases affect the MLG only minimally if at all. The topic should not have come up at all after one glance of the first flight. But then again all our judgements come from a few images of 2 flights

Have to disagree. I am a 100% sure that the nose wheel would have been below the plume.


You are probably right - and in fact even the gear strut above the wheel would likely have been spared the hottest gases. But it goes to show that there is no limit to speculation about design decisions after one glance or even no glance. I was amazed to see speculation about hot wheels. I would rather hear speculation about whether the HTT 40 is going to spin and recover the way the IAF wants. I have seen no predictions yet - given the large numbers of design comments we have from a photo or two.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 06:00

http://english.mathrubhumi.com/polopoly ... /image.jpg

IJT: No one concerned about chappals and idolatry with communal garlands?

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 18 Jun 2016 06:02

shiv wrote:You are probably right - and in fact even the gear strut above the wheel would likely have been spared the hottest gases. But it goes to show that there is no limit to speculation about design decisions after one glance or even no glance. I was amazed to see speculation about hot wheels. I would rather hear speculation about whether the HTT 40 is going to spin and recover the way the IAF wants. I have seen no predictions yet - given the large numbers of design comments we have from a photo or two.

And that questioning should not be scuttled. If a question is stupid, show that it is stupid, technically. Piskology and non-technical nationalistic defensiveness/mocking does not serve any purpose.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 06:03

indranilroy wrote:And that questioning should not be scuttled. If a question is stupid, show that it is stupid, technically. Piskology and non-technical nationalistic defensiveness serve no good.

Well that is a matter of opinion. and opinions must not be suppressed either.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Manish_Sharma » 18 Jun 2016 06:08

Last edited by Manish_Sharma on 18 Jun 2016 06:22, edited 1 time in total.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Singha » 18 Jun 2016 06:13

My guesses
A2 a1 a3
A3 a2 a1
A1 a3 a2
A1 a3 a2

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 06:15

Dhananjay wrote:Since I can't find the newbie thread so I'm putting the queries here:


As you can see there are 3 images of same aircraft with same engines but 3 different wings number A1 , A2, A3

I have a few questions regarding these different wing orientations:

1. Which wing design plane will take least amount of runway TO TAKE OFF? Which planes will be 2nd and 3rd in that order?

2. Which wing design plane will take least amount of runway WHEN LANDING? Which planes will be 2nd and 3rd in that order?

3. Which wing design plane will have longest range? Which planes will be 2nd and 3rd in that order


:rotfl: Nice for armchair experts - but it really needs to go in the general mil questionsthread. If I bite this bait I will reply in that thread

added later - my reply here
viewtopic.php?p=2031263#p2031263
Last edited by shiv on 18 Jun 2016 06:33, edited 1 time in total.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 18 Jun 2016 06:21

Yeah, please post it there.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Manish_Sharma » 18 Jun 2016 06:21


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Re: Indian Military Aviation - 21 Sept 2015

Postby JayS » 18 Jun 2016 13:22

shiv wrote:OK found an image of the old Saras without Scimitar props
http://nal-ir.nal.res.in/715/1/saras3.JPG

I think the engine was changed - recall reading that somewhere


The new props have swept tips. Nice. Saras uses PT6A engines right? PT6A are ideal for pusher config.

shiv wrote: I would rather hear speculation about whether the HTT 40 is going to spin and recover the way the IAF wants. I have seen no predictions yet - given the large numbers of design comments we have from a photo or two.


I have been avoiding replying on this issue since I personally don't get the fuss over it. But how can one just see pics and speculate about spin characteristics, when even the designers of the aircraft can only say anything on it with confidence after doing tests on the actual config at least in Vertical WT if not in the flight tests?? How is this more acceptable to you than debating some visually identifiable issue which can be settled with some concrete technical pointers. If only putting speculations and gut feelings and fighting with non-technical pointers is the aim then sure, discuss anything, who cares. :roll:

indranilroy wrote:
7. I don't know if it is a facet of the plane just starting its flight testing, but I am a little surprised with the amount of flap deflection on the take off roll.


Perhaps the combination of BLR location (as Shiv pointed out) and conservative approach on the initial flights??

Could the change in NLG be related to change in the engine?? TPE-331 has a heavy gearbox on the front side. It might have a forward CG as compared to PT6A.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 18 Jun 2016 14:05

nileshjr wrote: But how can one just see pics and speculate about spin characteristics, when even the designers of the aircraft can only say anything on it with confidence after doing tests on the actual config at least in Vertical WT if not in the flight tests?? How is this more acceptable to you than debating some visually identifiable issue

It should be as easy to tell spin characteristics from a photo as it is to estimate exhaust gas temperatures close to the tyres from a photo.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Aditya G » 18 Jun 2016 18:05

Btw it is good to see a Hindustan designation on this aeroplane. It is a successor to a long series of trainers made by India. This is a legacy worth being proud of:

Image

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Re: Indian Military Aviation - 21 Sept 2015

Postby Kartik » 18 Jun 2016 22:43

shiv wrote:
nileshjr wrote: But how can one just see pics and speculate about spin characteristics, when even the designers of the aircraft can only say anything on it with confidence after doing tests on the actual config at least in Vertical WT if not in the flight tests?? How is this more acceptable to you than debating some visually identifiable issue

It should be as easy to tell spin characteristics from a photo as it is to estimate exhaust gas temperatures close to the tyres from a photo.


I guess it is better to stick to just coming to this forum once in a while and reading the news reports. People making educated guesses about something and having a discussion on that topic is now haram on BRF?

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Re: Indian Military Aviation - 21 Sept 2015

Postby nirav » 18 Jun 2016 23:03

shiv wrote:
nileshjr wrote: But how can one just see pics and speculate about spin characteristics, when even the designers of the aircraft can only say anything on it with confidence after doing tests on the actual config at least in Vertical WT if not in the flight tests?? How is this more acceptable to you than debating some visually identifiable issue

It should be as easy to tell spin characteristics from a photo as it is to estimate exhaust gas temperatures close to the tyres from a photo.


hear hear..

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Re: Indian Military Aviation - 21 Sept 2015

Postby Karan M » 19 Jun 2016 01:38

Usual DDM stuff but first 4 aircraft being handed to AF.
http://www.ndtv.com/india-news/wait-ove ... es-1420020

New Delhi: After a wait of over three decades, the Indian Air Force will finally get its hands on the first squadron of indigenous Tejas next month with the delivery of the fourth Light Combat Aircraft.

However, the first squadron will be made of up of just four Tejas aircraft, in stark contrast to at least 16 aircraft that usually makes up for one squadron globally.

State-run Hindustan Aeronautics Limited, manufacturer of Tejas, will hand over the fourth aircraft to the Air Force on July 1.

The four aircraft will be used for training and familarisation.


Rather than waiting for LAC Mk II, the Indian Air Force had decided to go in with an upgraded version of the existing Tejas with over 40 modifications.

The Indian Air Force currently plans to acquire 120 Tejas aircraft, with 100 of these having major modifications.

The force wants Active Electrically Scanned Array (AESA) Radar, Unified Electronic Warfare (EW) Suite, mid-air refuelling capacity and beyond the vision range missiles.

As per the production plan, six aircraft will be made this year (2015-16) and HAL will subsequently scale it up to eight and 16 aircraft per year.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 19 Jun 2016 05:03

Since the topic refuses to die down, here is one person, popular on BRF - Prof Prodyut Das, speculating about stall and spin of the IJT from images and news reports alone.
http://profprodyutdas.blogspot.in/2014/ ... rials.html
The real problem is human -psychological and cultural. We have great faith in rigourous analysis and so when things go wrong there is shock induced paralysis. Much time, I have seen, is spent in fixing blame rather than fixing the problem! In the “feel” based approach, which is sometimes, treated as a disability with sophistication, however, the Designer is not only acutely conscious of possible failures but also he has subconsciously prepared several “what if “ scenarios so the nettle is grasped firmly and quickly.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 19 Jun 2016 07:32

Karan M wrote:http://www.ndtv.com/india-news/wait-ove ... es-1420020

New Delhi: After a wait of over three decades, the Indian Air Force will finally get its hands on the first squadron of indigenous Tejas next month with the delivery of the fourth Light Combat Aircraft.

However, the first squadron will be made of up of just four Tejas aircraft, in stark contrast to at least 16 aircraft that usually makes up for one squadron globally.

This is the same NDTV that spoke of -200 degrees Celsius temperatures in Siachen in a recent TV linked on here They are good at numbers. NDTV did not exist when the first MiG 21 squadron was formed with 2 aircraft shipped to Mumbai and assembled - or maybe back then the global standard of squadrons allowed for 2 aircraft just like the global standard for Siachen temps is -200 now

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Re: Indian Military Aviation - 21 Sept 2015

Postby Shanu » 19 Jun 2016 08:35

^^ Oh what the poor chaps of Undie TV can do. Their cocktail dinners and foreign tours have stopped since the MMRCA deal was scrapped. And if LCA gets inducted in numbers, what will happen to the retirement savings they were planning to build with the next Indian fighter import. That's a nightmare, I say.

Its not without reason, that this channel always finds something negative to say about the current Government. Let them focus on their Government change agenda, and let us focus on the real developments that is transforming India.

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Re: Indian Military Aviation - 21 Sept 2015

Postby malushahi » 19 Jun 2016 17:21

^^^ sure enough

Rather than waiting for LAC Mk II

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Re: Indian Military Aviation - 21 Sept 2015

Postby JayS » 19 Jun 2016 20:38

HAL webpage has Take off and Landing videos for HTT-40

https://vimeo.com/171073982
https://vimeo.com/171073904

Nice and smooth Landing in crosswind (someone mentions crosswind in the background).

BTW, IR you mentioned somewhere that HTT-40 has reverse thrust right? That's an interesting thing for a small aircraft to have. So perhaps Landing on short semi-prepared strips is considered in design stage itself. Pointer to some particular use other than BT for HTT-40?? Else it doesn't really required to have it since it as a BT it would always be used on AF bases which have good long runways I suppose.

Is addition of thrust reversal mechanism a big deal?? Its an additional feature in prop pitch setting mechanism wherein it allows for pitch beyond 90deg - only single manual setting at higher than 90deg but lower than 180deg is sufficient for thrust reversal, I think. Need to check. But definitely a welcome feature in HTT-40. Great stuff from HAL.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 19 Jun 2016 20:51

I suspect they merely mean reverse thrust by adjusting the prop pitch to reverse the direction of thrust. That is the only mechanism that makes sense in a prop powered aircraft.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Karan M » 19 Jun 2016 22:04

shiv wrote:
Karan M wrote:http://www.ndtv.com/india-news/wait-ove ... es-1420020

New Delhi: After a wait of over three decades, the Indian Air Force will finally get its hands on the first squadron of indigenous Tejas next month with the delivery of the fourth Light Combat Aircraft.

However, the first squadron will be made of up of just four Tejas aircraft, in stark contrast to at least 16 aircraft that usually makes up for one squadron globally.

This is the same NDTV that spoke of -200 degrees Celsius temperatures in Siachen in a recent TV linked on here They are good at numbers. NDTV did not exist when the first MiG 21 squadron was formed with 2 aircraft shipped to Mumbai and assembled - or maybe back then the global standard of squadrons allowed for 2 aircraft just like the global standard for Siachen temps is -200 now


+100
These guys will just do their usual to gloss over anything indigenous and positive. Of late, I have found myself just ignoring all of the self loathing bile and trying to focus on the data desi "journalists" are hiding behind all their spin.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 19 Jun 2016 22:52

The HTT-40 does have reverse thrust which was showcased to Parikkar as well during the landing.

There are few "levels" of braking for a prop-driven airplane. One is where the propellers are placed at a very fine pitch (propeller is at almost 90 degrees to the airflow). In this case, the propeller windmills acting like a large circular air brake. This was the undoing of Saras PT2. The pilots did not feather the propellers of the unlit engine. They figured it out too late why the plane was slowing down so quickly.

The other case, the propellers can be placed at negative pitch. In this setting, the propeller pushes the air forward, thus attaining thrust reversal. This has to be done manually by overriding mechanical safety gates. This makes sure that this setting is not used accidentally during flight which can have catastrophic effects. On the ground, the pilot can engage this. The mechanism to place the propellers in negative pitch is more simple on the TPEs than the PT6As. But this does not mean that the PT6A powered planes cannot attain revere thrust. That is why the HAL chairman's statement puzzles me.

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Re: Indian Military Aviation - 21 Sept 2015

Postby PratikDas » 19 Jun 2016 23:04

indranilroy wrote:The HTT-40 does have reverse thrust which was showcased to Parikkar as well during the landing.

There are few "levels" of braking for a prop-driven airplane. One is where the propellers are placed at a very fine pitch (propeller is at almost 90 degrees to the airflow). In this case, the propeller windmills acting like a large circular air brake. This was the undoing of Saras PT2. The pilots did not feather the propellers of the unlit engine. They figured it out too late why the plane was slowing down so quickly.

The other case, the propellers can be placed at negative pitch. In this setting, the propeller pushes the air forward, thus attaining thrust reversal. This has to be done manually by overriding mechanical safety gates. This makes sure that this setting is not used accidentally during flight which can have catastrophic effects. On the ground, the pilot can engage this. The mechanism to place the propellers in negative pitch is more simple on the TPEs than the PT6As. But this does not mean that the PT6A powered planes cannot attain revere thrust. That is why the HAL chairman's statement puzzles me.

Great post - learned something here about Saras and propellers. Thanks!

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 20 Jun 2016 04:33

shiv wrote:
nileshjr wrote: But how can one just see pics and speculate about spin characteristics, when even the designers of the aircraft can only say anything on it with confidence after doing tests on the actual config at least in Vertical WT if not in the flight tests?? How is this more acceptable to you than debating some visually identifiable issue

It should be as easy to tell spin characteristics from a photo as it is to estimate exhaust gas temperatures close to the tyres from a photo.

It is not the same and does show your ignorance on the matter. And you have a follower in Nirav.

All the variables of the tyre problem can be found from pictures and literature survey of the engine exhaust, and tyre pressure temperature tolerances. This is not true of the spin characteristics. One cannot find where the CG is, what is the roll inertia, washout of the wings, etc from the picture or literature survey. Additionally, the study of the airflow near separation is highly non-linear and cannot be predicted with enough accuracy with existing human knowledge. It can be analyzed, not predicted. And that is why people still have to use CFD, wind tunnel studies, and still wait for surprises on the real deal.

Even after this, if people want to discuss aerodynamics of the HTT-40 based on pictures, they are most welcome! This is what separates BRF from the rest. The quality of knowledge and discussion. I myself had lengthy discussions with Prof. Das on the IJT. As long as the discussion sticks to physical realities, its fine. For example, I find HTT-40 to be bit stocky. For a BTT, it would be fine. However, for a heavier light attack platform, I am not sure if the tail surfaces, especially the elevator has a long enough lever. I would love somebody to prove me wrong.

I joined BRF only because the level of technical discussions. I would like to keep it that way, instead of indulging in piskology and pseudo-SDREness.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 20 Jun 2016 04:37

Kartik wrote:I guess it is better to stick to just coming to this forum once in a while and reading the news reports. People making educated guesses about something and having a discussion on that topic is now haram on BRF?

It is all of our collective responsibility to keep the technical discussions at BRF as high as we can. You asked a legitimate technical question, and a good discussion followed. Forget being wrong, it is welcome. At the same time, jingoism will always be there a BRF. We have to learn to balance all aspects.

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 20 Jun 2016 05:39

indranilroy wrote: It can be analyzed, not predicted. And that is why people still have to use CFD, wind tunnel studies, and still wait for surprises on the real deal.

The need for simulation and subsequent actual temperature data is true of exhaust gas temperatures close to the tyres as well. They must be measured and different configurations of exhaust flow analysed based on what heating effect it may have on different parts of the airframe. How is it possible to dogmatically state that problems will occur from the exhaust placement without access to the simulations and the data on the HTT 40? Please refer back to the original post that started this discussion.

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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 20 Jun 2016 06:52

I don't know what makes you feel that the studies you mention are typical! Most of the studies that I know are reactionary, like the case that Kartik presents.

Quite frankly, like Nilesh, I don't understand what your fuss is about? And what is wrong in asking, "I have had a similar experience before, does anybody else think that this could be a problem"? What else is a discussion forum for? Or is asking questions against an SDRE design not SDRE enough?

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Re: Indian Military Aviation - 21 Sept 2015

Postby shiv » 20 Jun 2016 07:46

indranilroy wrote:I don't know what makes you feel that the studies you mention are typical! Most of the studies that I know are reactionary, like the case that Kartik presents.

I am not sure I understand your question. But I will explain what what I understand of it.

After I read the original comment I searched for information I could find about tyre burst from overheating caused by engine exhaust gases. I was unable to find even one reference to a tyre burst caused by overheating from exhaust gases. Not even in aircraft like the Shorts Tucano that has a similar underfuselage exhaust layout. I found plenty of studies where tyre temperatures were measured under various conditions. I found studies where engine exhaust gas temperatures were measured, including a pdf (that both you and I found independently) about engine exhaust temperatures at various distances from the exhaust. Clearly these temperature studies are typical.

Here is the question I asked earlier "What would make anyone feel that the HTT 40 tyre might burst from overheating after taking one look at the first images from the first flight?" If the studies you mention are not typical what technical explanation and analysis was offered? I saw no analysis to justify the suggestion of tyre overheating from exhaust gases. Then what was the reason for the comment? That is all I asked. The piskology word was mentioned by someone else, including yourself. not by me.


indranilroy wrote:Quite frankly, like Nilesh, I don't understand what your fuss is about? And what is wrong in asking, "I have had a similar experience before, does anybody else think that this could be a problem"? What else is a discussion forum for? Or is asking questions against an SDRE design not SDRE enough?


With deep respect and apologies in advance if I cause you hurt, may I ask you what was the "similar experience" you refer to? You have yourself stated that such studies are atypical and that they will be done after something occurs. If it has not yet occurred what is the "similar experience" that some one had? I also want data and analysis.

I am repeating an earlier question here: "What design experience might have caused a person to say that tyres may burst from engine exhaust overheating?" If it is speculation why not say so and say that there is no data of tyre bursts or tyre temperatures to be analysed? The high standards of analysis that we all want cannot be done. Speculation can be from ignorance too. I don't understand why the original comment was made. Sorry if you think this is a fuss. Or that it is wrong to ask if a comment was made out of ignorance?

Indranil
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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 20 Jun 2016 10:15

shiv wrote:
indranilroy wrote:I don't know what makes you feel that the studies you mention are typical! Most of the studies that I know are reactionary, like the case that Kartik presents.

I am not sure I understand your question. But I will explain what what I understand of it.

After I read the original comment I searched for information I could find about tyre burst from overheating caused by engine exhaust gases. I was unable to find even one reference to a tyre burst caused by overheating from exhaust gases. Not even in aircraft like the Shorts Tucano that has a similar underfuselage exhaust layout. I found plenty of studies where tyre temperatures were measured under various conditions. I found studies where engine exhaust gas temperatures were measured, including a pdf (that both you and I found independently) about engine exhaust temperatures at various distances from the exhaust. Clearly these temperature studies are typical.

The studies that you reported had nothing to do with impingement of hot gases on the tyre. When Kartik first wrote about this, I think I was the first one who said that this is a non-issue and posted about the Short Tucano, the Grand Caravan, Kestrel 350 etc. I would be very happy, if you could show me one study on the impingement of exhaust gases aircraft wheels. It should be easy if it were typical.

shiv wrote:Here is the question I asked earlier "What would make anyone feel that the HTT 40 tyre might burst from overheating after taking one look at the first images from the first flight?" If the studies you mention are not typical what technical explanation and analysis was offered? I saw no analysis to justify the suggestion of tyre overheating from exhaust gases. Then what was the reason for the comment? That is all I asked. The piskology word was mentioned by someone else, including yourself. not by me.
indranilroy wrote:Quite frankly, like Nilesh, I don't understand what your fuss is about? And what is wrong in asking, "I have had a similar experience before, does anybody else think that this could be a problem"? What else is a discussion forum for? Or is asking questions against an SDRE design not SDRE enough?


With deep respect and apologies in advance if I cause you hurt, may I ask you what was the "similar experience" you refer to? You have yourself stated that such studies are atypical and that they will be done after something occurs. If it has not yet occurred what is the "similar experience" that some one had? I also want data and analysis.

I am repeating an earlier question here: "What design experience might have caused a person to say that tyres may burst from engine exhaust overheating?" If it is speculation why not say so and say that there is no data of tyre bursts or tyre temperatures to be analysed? The high standards of analysis that we all want cannot be done. Speculation can be from ignorance too. I don't understand why the original comment was made. Sorry if you think this is a fuss. Or that it is wrong to ask if a comment was made out of ignorance?

A post from much earlier:
Kartik wrote:
indranilroy wrote:The placement of the exhaust has nothing to do with the airplane designers, but everything to do with the design of the engine fitted into the plane. When the mockup was shown in AeroIndia11, they had planned to go with a PT6A which has the exhaust on the sides. However, during the course of the final design, they chose the TPE331-12B engine which has its exhaust at the bottom. I leave it to interested members to learn why the TPE331-12 series,14 series etc. have the exhaust at the bottom.

And no, the exhaust warming up the tyres is a non-issue. I have never come across this.


well, I've come up against an issue with ECS pack causing overheating of panels, which was only noticed during a very late phase of the design. led to a heck of a lot of rework. So, these things can happen. But seeing the Shorts Tucano as per your last post did make it appear that this particular exhaust placement may probably be a non-issue. Which would be good, since any re-design would lead to added time to the schedule.

Shiv saab, tyres can burst due to excessive heat. But maybe the wash from the propeller diffuses the heat, so it may not be an issue at all in service.

Anyways, I have said what I needed to say. I will see myself out of this discussion.

ramana
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Re: Indian Military Aviation - 21 Sept 2015

Postby ramana » 20 Jun 2016 21:23

Folks don't get so serious. Know when its humor and when its not.

Thanks,

ramana

PS: Old timers are wary of Indian designs being run down and hence the quick repartee.

Indranil
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Re: Indian Military Aviation - 21 Sept 2015

Postby Indranil » 20 Jun 2016 21:48

1. We can put the tyre overheating problem to rest.
2. Smoothening the canopy would help the aesthetics greatly.
3. The play for the control rod on the elevator is too large for a trim tab. It is for the elevator itself.

Image

nirav
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Re: Indian Military Aviation - 21 Sept 2015

Postby nirav » 20 Jun 2016 22:44

indranilroy wrote:1. We can put the tyre overheating problem to rest.



Overheating "problem" !?

There is NO overheating problem on the HTT 40.

It was there only in the mind of someone with a keen eye.


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