Newbie Corner & Military Miscellaneous

manish.rastogi · Post by **manish.rastogi** » 05 Nov 2010 17:15

Hey everyone....I am Manish I am in 12th class.....I would like to know about the institutes providing aeronautical engineering(designing) in India!!!!

Thanks

Bala Vignesh · Post by **Bala Vignesh** » 05 Nov 2010 17:34

^^^I think this would be OT even for this thread..
Anna university, Chennai,
IIT, Chennai,
Punjab College of Engineering, Chandigarh,
IIT, Kharagpur,
Madras Institute of Technology,
These are some of the top institutes offering Aeronautical Engineering. There are many colleges under Punjab university, Anna University that offer this course.

manish.rastogi · Post by **manish.rastogi** » 05 Nov 2010 18:11

Thank you for the reply sir.....i wasn't much sure about all these!!!

Gurneesh · Post by **Gurneesh** » 06 Nov 2010 03:47

^^^^ For aero you must consider IIT Kanpur.

On a different note,

Mirage 2000 has max takeoff weight of 17000 kg and engine max output with aftbrn is 95.1 kN. Thrust/weight is 5.59 N/kg

LCA has MTW as 13500 and engine output is 78.7 (or 85 ?) kN. Thus thrust/weight is 5.82 (6.29 ?) N/kg.

Clearly LCA has superior thrust to weight ratio even with 404. Then why does IAF term LCA to be underpowered ?

Prasad · Post by **Prasad** » 06 Nov 2010 11:18

I have no knawlidj of aero design. That said, in this picture there is the fuselage, then there is the engine intake which is circular/elliptical shaped. In between there is a region. What is aft that area? As in, air flows into the intakes straight into the engine. what happens to air that flows into this in-between region? Is that structure part of the intakes? TIA!

Bala Vignesh · Post by **Bala Vignesh** » 06 Nov 2010 11:26

^^ Those are the Variable angle intake vanes, i guess.. Gurus please confirm..

Prasad · Post by **Prasad** » 06 Nov 2010 11:30

Never mind. This picture makes it abundantly clear.

Gaur · Post by **Gaur** » 06 Nov 2010 12:56

Bala Vignesh wrote:^^ Those are the Variable angle intake vanes, i guess.. Gurus please confirm..

I do not know what Variable Angle Intake means. Did you mean variable geometry intakes? If so, then this is not the case here. These are just splitter plates. They are used to divert the boundary layer from fuselage away from the intake. This is because the mixing of low energy and sluggish flow with the free stream will cause turbulence.

Marut · Post by **Marut** » 06 Nov 2010 15:03

nachiket wrote:What is the exact difference between a 155mm 39 caliber shell and a 155mm 52 caliber shell? I know that a 155mm shell will be larger than say a 130mm one and to put in very simple terms cause a bigger explosion. Since it carries more propellant, the range would also be greater. But what is the effect of the caliber?

As clarified earlier, the caliber refers to the length of the barrel. So 155/52cal will have 155*52 ~ 8m long gun barrel vs 155/45cal will 155*45 ~ 7m long barrel. The advantages of a longer barrel are longer range, longer/heavier shell=more explosive capacity. Of course this will require a redesign of the shell and the barrel as well to cope with the increased demands. ArmenT put a very good explanation of how this works with bullets. The same applies to any projectile shot through a barrel. Click here

Some more reading material:
http://en.wikipedia.org/wiki/Caliber_%28artillery%29
http://en.wikipedia.org/wiki/Category:A ... ammunition
http://en.wikipedia.org/wiki/Shell_%28projectile%29

This link gives a simplistic writeup of artillery guns - http://www.winterwar.com/Weapons/artyinfo.htm

Bala Vignesh · Post by **Bala Vignesh** » 06 Nov 2010 16:07

Gaur wrote: I do not know what Variable Angle Intake means. Did you mean variable geometry intakes? If so, then this is not the case here. These are just splitter plates. They are used to divert the boundary layer from fuselage away from the intake. This is because the mixing of low energy and sluggish flow with the free stream will cause turbulence.

Thanks gaurji... Guess still have a lot more to learn to live upto the BRFite name.

nachiket · Post by **nachiket** » 07 Nov 2010 01:24

Thanks Marut and Bala.

Bala Vignesh · Post by **Bala Vignesh** » 08 Nov 2010 23:13

Could someone suggest some books to learn more on the basics of modern aeroengines???

Indranil · Post by **Indranil** » 09 Nov 2010 11:11

Santosh wrote:
indranilroy wrote:^^^ What role do you want to see Tejas Mark III in. How will it be any different from designing MCA?
Why? It will perform the same role as Tejas Mk I&II albeit with 2 engines - air defence and limited ground attack. It will have longer legs and better thrust. Understandably the operational cost will be higher but that is a small price to pay for self sufficiency in such a high tech field. It can be a precursor to AMCA. To me it makes complete sense. If one Kaveri does not do the job, put 2, redesign the structure and move on.

ranjithnath wrote:^^^
If one Kaveri does not do the job, put 2, redesign the structure and move on.
it wont be easy as it sounds.the lca team has to redesign the fuselage and air intakes just to change the engine.putting 2 engines and redesigning the structure will be to create a new fighter.the entire FBW controls have to b rewritten and it would have to go through all the flight testing which would take years.the question is why opt for a twin engined tejas if we already have MRCA,mig 29 which can do the role of a medium twin engined aircraft?and is it wise to spend so much money and manhours into it when we already have inhouse development of AMCA??

Santosh, think a little more. You will see reasons.
Here are some pointers:
1. two engine, much more fuel, where should I keep that.
2. twin engine + much more fuel, how do I generate proportionally more lift.
3. Ranjith has already marked out the intake modification and know what if we have side intakes, you will no longer have the compressor blades covered.

There must be reason that none of the present fighters are twin engined versions of previous plane

.

Frankly your second post was little newbie-like.

What MCA be other than lessons learnt on LCA, with more fire oozing out of the back from desi engines. Tejas Mark II is the evolutionary step to LCA Tejas and the MCA is the next step from Tejas Mark II packed in stealthier body

.

Rahul M · Post by **Rahul M** » 09 Nov 2010 11:30

the origianl J-8 is a 2 engined J-7 though.

andy B · Post by **andy B** » 09 Nov 2010 11:41

Bala Vignesh wrote:Could someone suggest some books to learn more on the basics of modern aeroengines???

Bala saan here is something that Ramana ji posted some time back. I have been periodically going through it for references....very useful reading though not related to aero injuns it is still quite useful in understanding aviation and flight in general onlee

ramana wrote:Andyb for you:

Intro to Aerospace Engg

MIT OCW course.

Indranil · Post by **Indranil** » 09 Nov 2010 11:48

^^^ Thank you for reminding me about the same.

But having said that one should read the shortcomings of the original J-8 leading to quite a different J-8II which was closer to the Su-15 (a twin engined plane) rather than the Mig-21 (and hence the J-7).

But none-the-less, you are right there are precedents of a single engine fighter changed to a double engine one. Another precedent would have been the CAT proposed by HAL.

But alas gone are the days when aerodynamic performance was enough. One has to stay stealth now too!

Bala Vignesh · Post by **Bala Vignesh** » 09 Nov 2010 13:03

Andysaan,
Thanks for the link.

Neela · Post by **Neela** » 09 Nov 2010 16:24

Bala Vignesh wrote:Could someone suggest some books to learn more on the basics of modern aeroengines???

Jet Engines: Fundamentals of Theory, Design and Operation
Author: Klaus Hunecke

I am just starting on it...so cannot give you feedback.

Santosh · Post by **Santosh** » 10 Nov 2010 11:42

indranilroy wrote:Santosh, think a little more. You will see reasons.
Here are some pointers:
1. two engine, much more fuel, where should I keep that.
2. twin engine + much more fuel, how do I generate proportionally more lift.
3. Ranjith has already marked out the intake modification and know what if we have side intakes, you will no longer have the compressor blades covered.

There must be reason that none of the present fighters are twin engined versions of previous plane .

Frankly your second post was little newbie-like.

What MCA be other than lessons learnt on LCA, with more fire oozing out of the back from desi engines. Tejas Mark II is the evolutionary step to LCA Tejas and the MCA is the next step from Tejas Mark II packed in stealthier body .

indranilroy, I understand that twin engine aircraft will need more fuel than single engine aircraft. The aircraft has to be redesigned to account for the increased weight. It may not look anything like Tejas. No one is denying that. All I am saying is there has to be a way to put together all that we have achieved till now into a workable, competent aircraft in the Mig 29 type medium class. This should have been done 4-5 years back when people first started realizing that Kaveri would not be good enough for LCA. We would be half way there by now and there would be no MMRCA or Snecma-core-for-Kaveri type tamasha. After all RD-33 that powers Mig-29 is not a whole lot better than the current Kaveri. No reason why a Mig-29 class cannot be together around twin Kaveris. Are you understanding what I am saying?

Indranil · Post by **Indranil** » 10 Nov 2010 12:59

I do understand.

But my question to you is plain and simple. How is AMCA any different from a Mig-type fighter using lessons learnt for LCA. It is being developed in this era and hence stealth and bla bla have been put in.

It is not like we have finished our lessons from LCA long time back. We still seem to be learning "design" lessons as tests are flying. you must have heard that we still have to optimize the airframe, open up envelop. These are all critical tasks. I think now we are at a position to start building a 2 engine craft which is the AMCA.

10 years back when the MMRCA was visualized, I don't think we were at a stage where we could have realistically designed a good fighter.

I believe we are going down the right path. We have to field a almost complete plane (read IOC/FOC) to know well enough to design a "good" twin engine plane.

You can say that why not try a Mig-35 like plane which doesn't have VLO and the likes. My answer to that is that if the EF/Rafale/Mig-35/F-18 were in the design phase today or would have started 5 years back, VLO would have been part of that design. That's where state of art is.

So we are on the right curve IMHO

Santosh · Post by **Santosh** » 11 Nov 2010 10:07

Okay. Looks like guvermand is also in agreement with you. More power to LCA .. and guvermand

Dmurphy · Post by **Dmurphy** » 12 Nov 2010 12:48

CNN: Ilyas Kashmiri: Most dangerous man on Earth?

Ten years ago, Indian troops carried out a raid into Pakistani Kashmir.

shiv · Post by **shiv** » 13 Nov 2010 19:31

Talking about LCA, elevons, stall and spin tests reminded me of my boyhood days and playing with planes. While I have resolved to buy material to start making models again - here is a time-pass video I have created entitled "Aerodynamics for dummies - a "crash" course"

http://www.youtube.com/watch?v=b3xdC6VnCHc

Lalmohan · Post by **Lalmohan** » 15 Nov 2010 18:18

Dmurphy wrote:CNN: Ilyas Kashmiri: Most dangerous man on Earth?
Ten years ago, Indian troops carried out a raid into Pakistani Kashmir.

when lazy journalists interview pakistani military sources, they only get horsecr@p stories to quote
that entire 'story' is a madrassah legend

from news paper reports that we have seen on BRF over the years, the paks raided a border post and beheaded a dead indian jawan

the following week, the IA undertook the retailiatory raid on pak posts where the responsible troops came from and took punitive action

Bala Vignesh · Post by **Bala Vignesh** » 15 Nov 2010 22:35

shiv wrote:Talking about LCA, elevons, stall and spin tests reminded me of my boyhood days and playing with planes. While I have resolved to buy material to start making models again - here is a time-pass video I have created entitled "Aerodynamics for dummies - a "crash" course"
http://www.youtube.com/watch?v=b3xdC6VnCHc

Sir, simply brilliant.. So simple yet highly informative..

Indranil · Post by **Indranil** » 15 Nov 2010 23:39

^^^ Reminds me of my childhood days, I used to play around so much with the "bluntness of the nose", the height of the fuselage, the angle of attack of the plane of the wing, the dihedral angle, weight distribution, wing folded up or down. I did not understand all the aerodynamics then. Just blind experiments. I used to stay on the sixth floor and fly them from my balcony to see how far they went or wast they flew.

Indranil · Post by **Indranil** » 15 Nov 2010 23:44

I have a newbie question.

Why is the radar antennae shaped like a plate. In modern day AESA, why not shape it like the inside of the nose cone. It will give a lot more area to put more modules or make the nose thinner.

I can see a problem with the fact that very few of the modules will be directed in the direction of the nose of the aircraft. However we can go for a hemispherical design or a flattened hemispherical design. This would help us get more are for the modules or help us make the nose thinner with the same number of modules.

Why is such geometry not adopted for the antenna?

SaiK · Post by **SaiK** » 16 Nov 2010 00:43

Dileep has already answered this question I guess, if you can either trace him down or review the archives.

He is the person for you.

From an ergonomics point of view, imho it is an unnecessary complication of the spherical design.

Dileep can explain to you on attenuation, interferences etc.

Indranil · Post by **Indranil** » 16 Nov 2010 00:50

Thank you ... will dig trough the archives.

JimmyJ · Post by **JimmyJ** » 16 Nov 2010 07:15

AWACS are generally mentioned by degree to denote there coverage, like 360 degree for our phalcon. But what about the height?

Could a high flying aircraft intrude undetected and surprise the AWACS?

KiranM · Post by **KiranM** » 16 Nov 2010 22:33

Marut wrote:
nachiket wrote:What is the exact difference between a 155mm 39 caliber shell and a 155mm 52 caliber shell? I know that a 155mm shell will be larger than say a 130mm one and to put in very simple terms cause a bigger explosion. Since it carries more propellant, the range would also be greater. But what is the effect of the caliber?
As clarified earlier, the caliber refers to the length of the barrel. So 155/52cal will have 155*52 ~ 8m long gun barrel vs 155/45cal will 155*45 ~ 7m long barrel. The advantages of a longer barrel are longer range, longer/heavier shell=more explosive capacity. Of course this will require a redesign of the shell and the barrel as well to cope with the increased demands. ArmenT put a very good explanation of how this works with bullets. The same applies to any projectile shot through a barrel. Click here

Some more reading material:
http://en.wikipedia.org/wiki/Caliber_%28artillery%29
http://en.wikipedia.org/wiki/Category:A ... ammunition
http://en.wikipedia.org/wiki/Shell_%28projectile%29

This link gives a simplistic writeup of artillery guns - http://www.winterwar.com/Weapons/artyinfo.htm

Would it not be the length of a groove etched inside the barrel? 52 refers to the distance between 'lands' or consecutive notches of a groove.

Regards,
Kiran

shiv · Post by **shiv** » 17 Nov 2010 08:23

JimmyJ wrote:AWACS are generally mentioned by degree to denote there coverage, like 360 degree for our phalcon. But what about the height?

Could a high flying aircraft intrude undetected and surprise the AWACS?

Any ground based radar can see high flying objects from far far away. It is getting the low flying ones that need an AWACS. Up was never a problem. Down is.

shiv · Post by **shiv** » 17 Nov 2010 08:29

indranilroy wrote:I have a newbie question.

Why is the radar antennae shaped like a plate. In modern day AESA, why not shape it like the inside of the nose cone. It will give a lot more area to put more modules or make the nose thinner.

I can see a problem with the fact that very few of the modules will be directed in the direction of the nose of the aircraft. However we can go for a hemispherical design or a flattened hemispherical design. This would help us get more are for the modules or help us make the nose thinner with the same number of modules.

Why is such geometry not adopted for the antenna?

Indranil I had the thought too so thanks for voicing the question. I am even less knowledgeable than you say you are. The alternative could be to have a radar with 5 plates. One square plate facing forward giving - say 60 deg coverage in front and 4 plates forming 4 sides of a box to stare up, down and to the sides.

Why is this not done? The idea is so simple I am sure anyone would have thought of it so there must be technical reasons. Could it be processing power? The other thing is to have rearward facing radar at the back and sideways in the fuselage/wings.

Indranil · Post by **Indranil** » 17 Nov 2010 08:35

^^^ As per Saik sir's tip, I am still digging.

Paging Dileep sahab ... kripya is agyan balak aur dactur sahib ko rastaan dikhayein.

andy B · Post by **andy B** » 17 Nov 2010 08:40

shiv wrote:
JimmyJ wrote:AWACS are generally mentioned by degree to denote there coverage, like 360 degree for our phalcon. But what about the height?

Could a high flying aircraft intrude undetected and surprise the AWACS?
Any ground based radar can see high flying objects from far far away. It is getting the low flying ones that need an AWACS. Up was never a problem. Down is.

to add a bit more to what the doctor said....jimmy j the reason is that the awacs radar's FOV is quite wide thus it can see quite far up and down i guess the onlee way that an awacs radar will not be able to see something is if the missle targetting the awacs gets launched beyond the awacs detection range and then climbs waaay up beyond the stratosphere and then dives directly down on the awacs...theoretically ofcourse

koti · Post by **koti** » 17 Nov 2010 13:35

shiv wrote:
indranilroy wrote:I have a newbie question.

Why is the radar antennae shaped like a plate. In modern day AESA, why not shape it like the inside of the nose cone. It will give a lot more area to put more modules or make the nose thinner.

I can see a problem with the fact that very few of the modules will be directed in the direction of the nose of the aircraft. However we can go for a hemispherical design or a flattened hemispherical design. This would help us get more are for the modules or help us make the nose thinner with the same number of modules.

Why is such geometry not adopted for the antenna?
Indranil I had the thought too so thanks for voicing the question. I am even less knowledgeable than you say you are. The alternative could be to have a radar with 5 plates. One square plate facing forward giving - say 60 deg coverage in front and 4 plates forming 4 sides of a box to stare up, down and to the sides.

Why is this not done? The idea is so simple I am sure anyone would have thought of it so there must be technical reasons. Could it be processing power? The other thing is to have rearward facing radar at the back and sideways in the fuselage/wings.

I guess it is well recognized and applied.
Typhoon was supposed to have two side facing radars.
Even T-50 will be having 5 radars in total.

In all these, it seems the surface area of the frontal plate is of more importance.

Indranil · Post by **Indranil** » 17 Nov 2010 13:38

^^^ I think you didn't get the question. We were not speaking of the radars around the plane for 360 degree FOV.

We were speaking of just the shape of the antenna in the nose cone.

koti · Post by **koti** » 17 Nov 2010 13:51

^^I did.
I wanted to say that the requirement to opt for a 5 plated radar is being implemented by placing the plates at different locations on the plane rather then including everything in the radome.
This could be to accommodate larger plates then it is possible in a radome alone radar..

Indranil · Post by **Indranil** » 17 Nov 2010 14:04

^^^ But for whatever I fit in the radome, I need not make it flat right. I can make it in a shape conformal to the lateral surface of the inside of the nose cone to give me more area for more modules or more powerful modules. Why isn't the space inside the nose utilized in this way

Marut · Post by **Marut** » 17 Nov 2010 15:09

KiranM wrote:
Marut wrote: As clarified earlier, the caliber refers to the length of the barrel. So 155/52cal will have 155*52 ~ 8m long gun barrel vs 155/45cal will 155*45 ~ 7m long barrel. The advantages of a longer barrel are longer range, longer/heavier shell=more explosive capacity. Of course this will require a redesign of the shell and the barrel as well to cope with the increased demands. ArmenT put a very good explanation of how this works with bullets. The same applies to any projectile shot through a barrel. Click here

Some more reading material:
http://en.wikipedia.org/wiki/Caliber_%28artillery%29
http://en.wikipedia.org/wiki/Category:A ... ammunition
http://en.wikipedia.org/wiki/Shell_%28projectile%29

This link gives a simplistic writeup of artillery guns - http://www.winterwar.com/Weapons/artyinfo.htm
Would it not be the length of a groove etched inside the barrel? 52 refers to the distance between 'lands' or consecutive notches of a groove.

Regards,
Kiran

The grooves you are talking about are the rifling inside the gun barrels for providing some spin to the shell/projectile. This is done to conserve angular momentum thus enhancing range and accuracy. The rifling is in the order of 1 in 20 twist inside the barrel. It is nearly the same for pistols, rifles, arty/naval guns, tank guns, etc. It is not used as an identifier in gun nomenclature.

The gun barrel length expressed as function of its bore size comes from history. In the past, the cannons/naval guns came in different sizes and shapes with different ways to refer to them confusing most folks wanting to compare two guns. To standardize the nomenclature, the guns were named after their bore and barrel length. The barrel length was expressed as the number of cannon balls of the given bore could be accomodated inside the barrel. For eg. 100/L10 referred to a cannon of 100mm bore with 1m barrel length, since it can fit ten 100mm cannon balls in the barrel.