AMCA News and Discussions

[shiv]

Should be interesting to see how to dogfight a fighter that cant be literally seen

Well many such dogfights took place between the IAF and Pakistan air force in 1971 and 1999. Needless to say the IAF did not manage to shoot down even one unseen PAF fighter.

[manish.rastogi]

how about a LOAL done from a rearward ejection? Must be very stealthy! skunk-works!

i did not get this....please elaborate??

[shiv]

Shiv,

Is this the article that you are refering to.

Yes thanks

[Gaur]

Should be interesting to see how to dogfight a fighter that cant be literally seen

Well many such dogfights took place between the IAF and Pakistan air force in 1971 and 1999. Needless to say the IAF did not manage to shoot down even one unseen PAF fighter.

That was too much.

[Rahul M]

Should be interesting to see how to dogfight a fighter that cant be literally seen

Well many such dogfights took place between the IAF and Pakistan air force in 1971 and 1999. Needless to say the IAF did not manage to shoot down even one unseen PAF fighter.

clearly incompetent !

[Lalmohan]

dang... the paquis managed to steal the romulan cloaking technology?!?!??!

[Lalmohan]

now i know how alam shot down five kaffir hunters in five seconds
atleast four of them were cloaked using sdre vulcan tech, whilst alam had the djinn powered cloak penetrator goggles
i surprised he didn't shoot off his photon torpedo in all the excitement

[Viv S]

How Viv! The airframe has to accommodate the weapons so it will be fatter. That is a given. But that doesn't mean it's weight goes up. You must know enough structural knowledge that it takes much less to strengthen a tube like fuselage than a wings, which is flat and wants to flex much more.

You are right. Thats why said almost no weight addition. The door replaced the skin of the fuselage. If you are smart you can draw the door through strengthening elements. By passing the door edges along those elements, you can split it in half on the inside of the door and the housing of the door, thus adding minimal weight. You are right that the hydraulics will add weight. However, these hydraulics don't move control surfaces and can be much lighter. This is in terms of tens of kilos, not even hundreds.

Now I don't know what the final design will look like, but the effect on the aircraft will lead to a substantial weight gain. It will for example necessitate a wider larger fuselage, the wing area will need to increase correspondingly.

With regard to the structural strength, I'm quite sure its the other round. A tubular structure ought to experience less fatigue than a flat planar body (lower tensile stresses are generated).

for Missile ejection systems, you might like to read about the following. The weight of each AVEL on the F-22 is 50 kgs. link. So lets say we have 6 (most probably not) internal weapons. The weight gain is 300 kgs.

300kg for just missile ejectors is substantial. And this for deploying AMRAAMs only. In case something like the Harpoon/Exocet or a 2000lb HE bomb are to be integrated, for all we know, it could be closer to 500kgs. A weight gain of, say a ton, will have a much larger bearing on an aircraft with an empty weight of 9 tons than it will on one weighing 14 tons.

JSF's role changed from supporting the F-22 to complimenting the F-22. So if you say that F-35 is a minimalistic design, I don't think we will be correct.

The idea is that IAF is looking for a "medium" weight strike platform. The expectations from a medium fighter is as you guessed it is "medium". Payload-wise, range-wise and in some aspects capability wise (say radar size etc.).

The F-35 design was frozen long before the F-22 numbers were cut. In 2001 when the JSF contract was awarded to LM, F-22's prospective numbers still stood at over 300 units. Point is the F-35 was intended to replace the light weight F-16. Its specifications are broadly the same or less than what any air force would look for in the light/medium category.

For F-35 type roles it will have the FGFA. Ofcourse we could have gone for all FGFA, why AMCA? FGFA could do everything the AMCA is supposed to do! But thats not how AFs work and we all know why.

In terms of performance the FGFA will be far in excess of the F-35 (avionics and stealth aside). How it does vis-a-vis the F-22 would be the real question. Why are we going for the AMCA? To develop an indigenous base for advanced technologies, and to deliver a relatively cheap but effective aircraft to the IAF.

Yes but nobody is strapping an engine for the 30T plane in a 20T plane.

Maybe. But, for a 25 ton+ plane, no reason why not.

How do you keep the plane light? Why did the F-35 go 'overweight'? That's why I was asking what aspect is going to be scaled down - to have lighter fighter but with the same range as the F-35?

If you have to design a plane for an objective you can reach it through many ways. Some designers go one way, others go another way. Tiffy's designers went in a different direction than the F-15/Su-27. Yet they cater to the same requirements. Of course if you go bigger, in most cases you can carry more per plane or go further. But keeping your plane lighter you can maintain and send 2 planes to war. albeit that won't take care of the range. This is one of the critical advantage of the Su-30s over the Tiffy.

Question still remains. What sacrifices vis-a-vis the F-35 do see the AMCA making? Range? Payload? Integrated avionics?

F-35 has lot more in avionics than the F-22. For the US, they have a problem on their hands being decades ahead of the rest. They have to research everything out. Others get a lot of it by just analysing their products.

Well AFAIK, it just the EODAS. That still doesn't justify the F-35's development cost rivalling the F-22's.

Anyways, philosophy aside. A lighter plane might not be proportionally cheaper to produce. But it is definitely proportionally cheaper to maintain/store.

Accepted. But in HAL's case, the advantage of an easier development cycle (for a larger aircraft) will probably outweigh the benefit of a lower operational cost.

[Viv S]

viv, the VSTOL version has everything to do with the F35's problems. it is because of the need to maintain significant commonality with that version that the other two versions have been effed up. IOW have not been optimised as much as they could have been.
the F35 is verily not a good standard to judge these things.

That shouldn't the weigh all that much. The F-35B ended up over a ton heavier than the CTOL variant and has a 30% lower payload and range. How does one go about further optimizing the F-35A?

secondly, it is my opinion that a single engine design offers lesser internal volume than an equivalent twin engine design.

A single engine would occupy a lower volume but why would it offer the aircraft a lower internal volume?

btw, I don't quite get why you think the F-22 lags behind the su-30 in terms of payload or range by a vast amount. the payload figures are actually quite comparable with the flanker. except for the fact that flankerF-22 has a smaller internal fuel capacity since it has to carry weapons internally as well, unlike the flanker.
the limiter on amount of weapon carried is again volume available, not weight.
simply put, you would run out of space available to put your weapons in before you run out of weight capacity.

Yes, the gap between the two in terms of payload and range(taking the two as a related function rather than considering the MTOW) isn't all that much. But, with an external payload the F-22 will probably fall short of the MKI (I say probably because the max. range is still classified). And yes, the MKI's fuel capacity is the biggest reason (even though the F-22 is a very large aircraft as well). Given that they'll fly in the same configuration (unlike the F-22 and MKI), how viable is an aircraft smaller than the F-35 (with a proportionally smaller fuel capacity) that still equals or exceeds the F-35 in the strike role?

the point that needs to be understood here is that all of those engine changes are happening at least 20+ years after their first flight, they will spend anywhere between 10-15 years of their service life with their original spec engines. and even then the uprated engines offer an improvement of 15-20% at most.
going by this, the AMCA would need its uprated engines in 2037 and beyond. so why should we bother about that right now ?
like any other aircraft it can be re-engined in its MLU if needed ?

Agreed. But, the AMCA will probably get its IOC after 2025. Perhaps even after 2030. The Rafale and EF apart, by then the F-22 and F-35 (and probably the PAK-FA) will be going through a mid-life upgrade as well. Allowing for a larger (or equivalent to the F-35) fighter will lead to a faster and cheaper development cycle, and the aircraft will remain cutting edge in 2030, even while jingos are debating India's sixth generation aircraft program.

[Viv S]

So the important question is what quantity of weapons is the AMCA, a multi-role fighter (form what I have read the IAF wants a full multi-role not a strike or strike oriented ) required to carry. The design that was shown in AI 09( I guess it will be similar in weight and size to the rafale as it is projected to use essentially the same engine) can carry only 6 AAM (4 medium and 2 short ranged) internally in air to air mode. Is that really enough? I am skeptical.

A 14 ton F-35 carries four AAMs internally. Expecting a 9 ton AMCA to carry six is rather optimistic. Hopefully the size of the final design will be 'proportional' to a 6 AAMs.

[Indranil]

It will for example necessitate a wider larger fuselage, the wing area will need to increase correspondingly.

Generally it is in the opposite order, With a wider fuselage you can generate sufficient amount of lift and thus can go for thinner and stubbier wings.

With regard to the structural strength, I'm quite sure its the other round. A tubular structure ought to experience less fatigue than a flat planar body (lower tensile stresses are generated).

I will not say anything here, except asking you to read further.

300kg for just missile ejectors is substantial. And this for deploying AMRAAMs only. In case something like the Harpoon/Exocet or a 2000lb HE bomb are to be integrated, for all we know, it could be closer to 500kgs. A weight gain of, say a ton, will have a much larger bearing on an aircraft with an empty weight of 9 tons than it will on one weighing 14 tons.

Are you just writing this for the sake of writing. I suggest you read more on how missiles and other ammunitions are attached to same pylons. Just a teaser, the pylons have standard housing which every missile and other weapon adapters adhere to.

Point is the F-35 was intended to replace the light weight F-16. Its specifications are broadly the same or less than what any air force would look for in the light/medium category.

That not true. F-35 were supposed to raplace the F-16, F-18 and A-10 and the AV-8B Harrier II in a single plane! To add to that, to keep development, production, and operating costs down, a common design was planned in three variants that share 80 percent of their parts. And they wanted it to be a air superiority second only to F-22 on top of this!
This is what LM claimed.

Lockheed Martin claims the F-35 is intended to have close and long-range air-to-air capability second only to that of the F-22 Raptor. The F-35 is required to be four times more effective than legacy fighters in air-to-air combat, eight times more effective than legacy fighters in air-to-ground combat, and three times more effective than legacy fighters in reconnaissance and suppression of air defenses – while having better range and requiring less logistics support.

Ofcourse it had to look like a toad. If that is what you call a F-16 replacement, I will stop discussing right away!

In terms of performance the FGFA will be far in excess of the F-35 (avionics and stealth aside). How it does vis-a-vis the F-22 would be the real question. Why are we going for the AMCA? To develop an indigenous base for advanced technologies, and to deliver a cheap aircraft to the IAF.

As far as I have read they want a strike aircraft to complement the FGFA. Ofcourse it should be able to defend itself if attacked. It should be multirole to only that extent. I hope they stick to that rather than making it a jack of all trades and master of none.

Maybe. But, for a 25 ton+ plane, no reason why not.

Thats only in your mind. IAF has strictly said that it has to be under 25 T. ADA has said 20T. You are throwing your hat around.

Question still remains. What sacrifices vis-a-vis the F-35 do see the AMCA making? Range? Payload? Integrated avionics?

Payload! Types of armament. All round weight goes down, engine size goes down. Engine size goes down, fuel carried goes down. For a moment if you think that it can be done, you will see the ways. You have started of by thinking F-35 is be-all-end-all.

But in HAL's case, the advantage of an easier development cycle (for a larger aircraft) will probably outweigh the benefit of a lower operational cost.

Job of HAL is not to look for their convenience. Neither will IAF/MOD look for HAL's convenience. Besides, even if it wants to develop a "heavy" plane it has to design and build it. I don't see how development cycle is shortened, unless they use common things from the FGFA design. In that case, why design anything in first place. Adapt FGFA for a strike role. There must be a requirement for a "medium" fighter, which IAF is asking from ADA/HAL.

[Indranil]

Viv,

You would like to read this.

You would be able to make out that it is a very official presentation which has been "Approved for public release, distribution is unlimited".

On Page no. 7, you will find the planes the F-35 was designed to replace.
I am naming them here: F-16, A-10, F/A-18, Harrier, F-111, AMX, Tornado.

On Page 38, there is not a single 2000 pd. Paveway bomb which is carried internally (and I must say for good reason). There is a JDAM for 2000 lb.

Page 39 one realizes one of the critical reasons why the F-35 is so fat. It is almost as fat as it's engine. A single engine was a necessity of the VTOL system. You can see due to the diameter of the engine, no missiles could be packed underneath behind the nose wheel.

This is not the case with AMCA. From livefist.

Also the F-18 has a payload of 8.1 Tons and internal fuel capacity of 8.4 T which is a total of 16.5T.
You can see that it lies somewhere between the "heavy" fighters and the "medium" fighters.

"heavy" fighters - fuel + armament weight
F-22 - 18.3T
F-15 - around 18 T
PakFA - around 18.5 T
Su-30 - around 20.4 T

"medium" fighters (I have left out Mig-35 as it MTOW is near 29T) - fuel + armament weight
EF- around 12 T
Rafale- around 14 T
F-18- around 13 T
F-16- around 10.5 T
Mirage2000- around 9.5T
Gripen NG- around 8 T

So its weight is also MTOW is also between that of a medium fighter and a heavy fighter.

Question is. Are we trying to rival the F-35 or build a "medium" fighter that we need.

If we stick to a medium fighter we can definitely derive one whose MTOW is below 25 T.

In AI 09 ADA specified the design to be between 16-18 T with 4 T of fuel and around 2 T of internal load. It must have gone through revisions. But to make it a 25T + plane and call it "medium" ... hmmm I don't think the guys out there are so naive

[Viv S]

It will for example necessitate a wider larger fuselage, the wing area will need to increase correspondingly.

Generally it is in the opposite order, With a wider fuselage you can generate sufficient amount of lift and thus can go for thinner and stubbier wings.

How much lift can you generate from the fuselage?! How DO you generate lift from the fuselage of F-22/F-35 type aircraft? How much more lift can you generate compared to say the Eurofighter. How can it come anywhere close to substituting the reduced wing area?

With regard to the structural strength, I'm quite sure its the other round. A tubular structure ought to experience less fatigue than a flat planar body (lower tensile stresses are generated).

I will not say anything here, except asking you to read further.

What would suggest I read? I don't see how I can apply anything learnt in SoM. I'm assuming I can treat it as a sheet of metal; simple Mechanics would suggest a bent sheet would experience a lower tensile stress than a taut one, leading to lower fatigue. So ... where am I going wrong? Or should one determine stress in shear (more common for aluminium) instead (though I don't see how the result changes)?

300kg for just missile ejectors is substantial. And this for deploying AMRAAMs only. In case something like the Harpoon/Exocet or a 2000lb HE bomb are to be integrated, for all we know, it could be closer to 500kgs. A weight gain of, say a ton, will have a much larger bearing on an aircraft with an empty weight of 9 tons than it will on one weighing 14 tons.

Are you just writing this for the sake of writing. I suggest you read more on how missiles and other ammunitions are attached to same pylons. Just a teaser, the pylons have standard housing which every missile and other weapon adapters adhere to.

But, then this isn't a pylon we're talking about. The AVEL IIRC has to apply something like 40Gs to eject the missile and as the name suggests its designed for the 150kg AMRAAM not the 500kg JSOW (in F-35's case).

Point is the F-35 was intended to replace the light weight F-16. Its specifications are broadly the same or less than what any air force would look for in the light/medium category.

That not true. F-35 were supposed to raplace the F-16, F-18 and A-10 and the AV-8B Harrier II in a single plane! To add to that, to keep development, production, and operating costs down, a common design was planned in three variants that share 80 percent of their parts.

The F-16, F-18 and Harrier II yes. Its can't really replace the A-10; the squadrons will probably be re-equipped with it and their operational role suitably modified.

And they wanted it to be a air superiority second only to F-22 on top of this!

This is what LM claimed.

Lockheed Martin claims the F-35 is intended to have close and long-range air-to-air capability second only to that of the F-22 Raptor. The F-35 is required to be four times more effective than legacy fighters in air-to-air combat, eight times more effective than legacy fighters in air-to-ground combat, and three times more effective than legacy fighters in reconnaissance and suppression of air defenses – while having better range and requiring less logistics support.

It was/is expected to have a superior air-to-air capability because of the sensor fusion and the inherent stealth. The airframe itself allows only for a maximum of four air to air missiles or two 2000lb JDAMs and two missiles.

Ofcourse it had to look like a toad. If that is what you call a F-16 replacement, I will stop discussing right away!

The looks don't matter. Yes the requirements for a AF F-16, a naval F-18 and a STOVL Harrier II are different. But, the F-35A, F-35B and F-35C ARE different. 80% parts are claimed common, but the fact that the F-35A weighs 13.3 ton empty while the F-35C weighs 15.8 tons tells me, the CTOL variant isn't making allowances for a navalized version. The F-35C's wing area is almost 50% more than the F-35A. Compare that to a 'practically new' Super Hornet which has a 25% larger wing area than the Hornet. If I said the Rafale was intended to replace the Mirage-2000, would you disagree on the basis that the Rafale-M exists. Or that the Gripen would stop being a replacement to the Viggen if the Sea-Gripen materializes.

As far as I have read they want a strike aircraft to complement the FGFA. Ofcourse it should be able to defend itself if attacked. It should be multirole to only that extent. I hope they stick to that rather than making it a jack of all trades and master of none.

As opposed to? I'm assuming it will have an AESA and the weapons bay will accommodate air-to-air weapons. That about brings it at par with the F-35 in terms of operational flexibility. If anything its the air to ground equipment like an internal/dispersed IRST system that will lead to any bloat. Point is its not as simple as making a trade-off between A2A and A2G capabilities. A super-cruising aircraft will be able to lob both missiles and PGMs a greater distance. A larger weapons bay will allow the aircraft to carry more weapons of either kind.

Maybe. But, for a 25 ton+ plane, no reason why not.

Thats only in your mind. IAF has strictly said that it has to be under 25 T. ADA has said 20T. You are throwing your hat around.

One could say the GoI/Armed Forces will do what they do, therefore BRF is redundant. The design is very far from being finalized and the crux of this debate is my questioning the viability/efficacy of a stealth fighter with a MTOW of 20 tons. The IAC-1's design grew from a proposed 20,000T to 37,000T to a further 40,000T - I don't think the AMCA's design has been frozen either.

Question still remains. What sacrifices vis-a-vis the F-35 do see the AMCA making? Range? Payload? Integrated avionics?

Payload! Types of armament. All round weight goes down, engine size goes down. Engine size goes down, fuel carried goes down. For a moment if you think that it can be done, you will see the ways. You have started of by thinking F-35 is be-all-end-all.

Here are you referring to the maximum load that can be carried by the aircraft (9 tons for the F-35) or the capacity of the weapons bay (4 AAM // 2 x JDAM + 2 AAM) or both? And just for general idea, what do you think a possible figure for the AMCA's payload will be?

Actually I'm trying to reconcile myself with all the criticism of F-35 which ranged from insufficient performance and to cost and time escalations in development. And that opting for a lighter fighter that further miniaturizes the F-35's avionics while providing equalling or exceeding it in a strike role, is a better option than a larger aircraft with (one would assume) greater room for growth.

But in HAL's case, the advantage of an easier development cycle (for a larger aircraft) will probably outweigh the benefit of a lower operational cost.

Job of HAL is not to look for their convenience. Neither will IAF/MOD look for HAL's convenience. Besides, even if it wants to develop a "heavy" plane it has to design and build it. I don't see how development cycle is shortened, unless they use common things from the FGFA design. In that case, why design anything in first place. Adapt FGFA for a strike role. There must be a requirement for a "medium" fighter, which IAF is asking from ADA/HAL.

I suppose 'easier' wasn't the best term to use. I was talking in terms of feasibility/complexity not convenience. Yes a heavier plane would require design and production but it would be less challenging in terms of not requiring an as densely packed airframe, offer better a better range and payload, a bigger weapons bay (again less complex), longer intakes allowing for an S-bend with lower turbulence, and with a pair of F119s will offer a performance comparable to a re-engined F-22 or PAK-FA. And the downside to this of course, is a higher operating cost.

[shiv]

How much lift can you generate from the fuselage?! How DO you generate lift from the fuselage of F-22/F-35 type aircraft? How much more lift can you generate compared to say the Eurofighter. How can it come anywhere close to substituting the wings?

The following video is a classic example of an object flying horizontally with body lift
http://www.youtube.com/watch?v=4cZt57VUpT0

The amount of life fuselage alone can produce can only be demonstrated by breaking off one wing, as in this video
http://www.youtube.com/watch?v=6iFrw_7dsLk

Body Lift

Some aircraft with wings also employ bodies that generate lift. The Short SC.7 Skyvan produces 30% of the total lift from the fuselage

[Viv S]

The following video is a classic example of an object flying horizontally with body lift
http://www.youtube.com/watch?v=4cZt57VUpT0

The amount of life fuselage alone can produce can only be demonstrated by breaking off one wing, as in this video
http://www.youtube.com/watch?v=6iFrw_7dsLk

Body Lift

Some aircraft with wings also employ bodies that generate lift. The Short SC.7 Skyvan produces 30% of the total lift from the fuselage

Question is two-fold-

i) how much lift will it generate in level flight? At any positive AoA, the lift generated with have a drag penalty.

ii) how much is the additional lift generated with a wider flat bottomed fuselage vis-a-vis a 'normal' fighter like this.

[shiv]

i) how much lift will it generate in level flight? At any positive AoA, the lift generated with have a drag penalty.

ii) how much is the additional lift generated with a wider flat bottomed fuselage vis-a-vis a 'normal' fighter like this.

Great questions for an ignoramus such as myself. However one answer that I have in my mind (right or wrong) is "How much surface does the air see or feel?" If the air sees (or feels) 30% of the undersurface from fuselage alone then 30% of the lift in level flight "in clean condition" could be generated by the fuselage.

From the picture below it appears that at least 30% of the surface area that the air "sees" is fuselage


What happens when you change the AoA is another matter. I don't know.

[abhik]

A 14 ton F-35 carries four AAMs internally. Expecting a 9 ton AMCA to carry six is rather optimistic. Hopefully the size of the final design will be 'proportional' to a 6 AAMs.

the last shown design iteration has 6 AAM capacity.
http://4.bp.blogspot.com/_o_no4M2xEPY/T ... AWAY+3.JPG

[Jeff Wickline]

A very educative discussion for newbies like me.
Wish to submit the following to test my understanding about the AMCA:
1) A twin engine configuration is more suitable for internal stores (missiles)
2) Provision for internal store is much like the hold of a passenger/transport aircraft. This , though makes the fuselage bulkier, does not add more surface area. It increases only depth as far as I can imagine. So not substantial additional lift contribution.
3) In physics classes we were told that the body is an inefficient lift generator. So bulk of the lift is to be generated by the wings. With wing loading constant, this means larger wing area.
4) Addition of the "stores hold" may not contribute much to increased drag because the drag from external stores would be much higher.
Don't know if the above makes sense. Thanks in advance for the patience of the experienced members.

[Rahul M]

viv, the VSTOL version has everything to do with the F35's problems. it is because of the need to maintain significant commonality with that version that the other two versions have been effed up. IOW have not been optimised as much as they could have been.
the F35 is verily not a good standard to judge these things.

That shouldn't the weigh all that much. The F-35B ended up over a ton heavier than the CTOL variant and has a 30% lower payload and range. How does one go about further optimizing the F-35A?

what has the excess weight of B version over A got to do with it ? what I have said is very simple, the B version is very complex and due to the need to maintain commonality with it the A version could not be optimised as much as would have been possible (on a stand alone design of same weight and thrust category)

secondly, it is my opinion that a single engine design offers lesser internal volume than an equivalent twin engine design.

A single engine would occupy a lower volume but why would it offer the aircraft a lower internal volume?
as I've already explained to indranil, a single large engine allows much less continuous space than two smaller engines generating the same thrust. free space of a few cube feet here and there is not enough to put an weapon in.
try putting a ball of 1 cm radius in a 2cm box and repeat with 2 balls of .5 cm radius. you will hopefully get my point.
for about the same thrust figure a single F135 has a volume 2.5 times that of two EJ-200's !!

btw, I don't quite get why you think the F-22 lags behind the su-30 in terms of payload or range by a vast amount. the payload figures are actually quite comparable with the flanker. except for the fact that flankerF-22 has a smaller internal fuel capacity since it has to carry weapons internally as well, unlike the flanker.
the limiter on amount of weapon carried is again volume available, not weight.
simply put, you would run out of space available to put your weapons in before you run out of weight capacity.

Yes, the gap between the two in terms of payload and range(taking the two as a related function rather than considering the MTOW) isn't all that much. But, with an external payload the F-22 will probably fall short of the MKI (I say probably because the max. range is still classified). And yes, the MKI's fuel capacity is the biggest reason (even though the F-22 is a very large aircraft as well). Given that they'll fly in the same configuration (unlike the F-22 and MKI), how viable is an aircraft smaller than the F-35 (with a proportionally smaller fuel capacity) that still equals or exceeds the F-35 in the strike role?
same configuration as what ? f35 ?
since it will not have to pay the penalties that the f35 design had to, yes it is quite viable.

the point that needs to be understood here is that all of those engine changes are happening at least 20+ years after their first flight, they will spend anywhere between 10-15 years of their service life with their original spec engines. and even then the uprated engines offer an improvement of 15-20% at most.
going by this, the AMCA would need its uprated engines in 2037 and beyond. so why should we bother about that right now ?
like any other aircraft it can be re-engined in its MLU if needed ?

Agreed. But, the AMCA will probably get its IOC after 2025. Perhaps even after 2030. The Rafale and EF apart, by then the F-22 and F-35 (and probably the PAK-FA) will be going through a mid-life upgrade as well. Allowing for a larger (or equivalent to the F-35) fighter will lead to a faster and cheaper development cycle, and the aircraft will remain cutting edge in 2030, even while jingos are debating India's sixth generation aircraft program.
what has MLU schedule of f22 and f35 got to do with AMCA's choice of engines ?
you mean AMCA should be built to its own future MLU configuration just because the f22 gets a MLU at the same time ?
an aircraft is upgraded when its operator air force feels a need for it, not because 'they are having one, so I should have one too'.
an f35 equivalent would be in the same heavy fighter category as the PAKFA but not as good. neither would it serve the purpose IAF wants it for. it will most certainly be more complex and costlier (unlike what you claim) especially because we don't have a chance in hell to be ready with the unobtanium engine that such a design would need. if IAF wanted a PAKFA, they can always order a PAKFA. they don't need a 'me too' F35esque design.
AMCA does NOT aspire to be the equivalent of f35, it aspires to be a medium LO fighter for IAF with good strike characteristics.
one can argue that AMCA type aircraft is what f35 should have aimed for, instead of the overpriced jack of all trades it is now.

[vic]

deleted.

[Rahul M]

self deleted.

[Rahul M]

Maybe. But, for a 25 ton+ plane, no reason why not.

> AMCA is ~ 20 ton last we know and unless there is some official announcement it is not 25+ tons. so kindly don't bring your imagination into the fray

> F-22 is nearer 40 tons than 30 and the f119 generates double the thrust of the kaveri snecma that AMCA is expected to go into service with.
recommending the engines of a 40 ton jet into a 20 ton one, especially when both will have very high TWR with their original configuration, is sheer nonsense. it will be a rocket, not a aircraft. it will certainly have the range of a diwali rocket.

kindly stop, this nonsense has gone on for far too long. people usually backtrack when their fantasies are pointed out but you continue to defend the indefensible.
if you want to present a fantasy fighter please do it in the aircraft design thread and not here.

[Indranil]

How much lift can you generate from the fuselage?! How DO you generate lift from the fuselage of F-22/F-35 type aircraft? How much more lift can you generate compared to say the Eurofighter. How can it come anywhere close to substituting the reduced wing area?

This is good question as lifting body is not very good if the lift is at a positive AoA. There is lift induced drag+aero-induced-drag(due to high aspect ratio)+greatly enhanced RCS. Actually this is used by "slow flyers" that we build as trainers (in aeromodels).
But you will be surprised to know that even in level flight fuselages can generate sufficient lift. This has been used many times in the opposite direction to generate down force for surface transport. Bullet trains, almost all maglev trains, F1 cars, sports cars, Richard Noble's Thrust SSC, etc etc. You see they don't have any (substantial) wings or AoA.
However its use in aeroplanes are not as well advertised. People start thinking straight to Burnelli. Few of the best exponents of fuselage lift generation are Mig-29, Su-27, F-15 and Pak-FA. It is not just the lift produced by a flat body at positive AoA. That happens for even airliners. But in the above examples, there is a gap between the engine nacelles. The air at the top flows above the cockpit and behind it , whereas the air below the fuselage blows straight through the channel between the engine nacelles. This creates considerable lift even in leveled flight. Imagine this "wing". How big is the camber? the height of the fuselage! how big is the chord? the length of the plane! I would not be very surprised if the lift generated by this part is 25-30% of the entire lift generated.
This is not just limited to the twin engined jets. The F-16's forbody is supposed to create substantial lift because of it's bubble canopy.
Many contest the 747's upper bulge has similar consequences. But that is not entirely true and makes for fascinating reading.

What would suggest I read? I don't see how I can apply anything learnt in SoM. I'm assuming I can treat it as a sheet of metal; simple Mechanics would suggest a bent sheet would experience a lower tensile stress than a taut one, leading to lower fatigue. So ... where am I going wrong? Or should one determine stress in shear (more common for aluminium) instead (though I don't see how the result changes)?

It is not strength of metal. It is the characteristics of shape. You should read about jigs and stingers. Anyways, just as an example, an uniform shape like circle has much more weight bearing capacity than an non uniform one. Hence a dome becomes a strongest shape. Archs are best bridges and buildings. And tunnels are thought to be self supporting, even if built underneath a mountain.

Fuselage of a plane is not built in the form of a tube because of just because it has the lowest drag possible. A hollow tube is not very flexible. You can take a sheet of any metal and fles it. But if you wound this up into a tube you will find it much harder to bend or flex.

I am sure you have sat in a plane and seen the wings flex all around. Did your fuselage flex as much?

Anyways here's a cutaway of Gripen. See the strengthening of wings relative to the fuselage.


Heres' the same for F-35

I was trying to find a similar one for Tejas, but couldn't find an image for the same.

Anyways go here and check the sixth CAD image of "WalkThru assembly of structural components of LCA."

And this is how much the wings on the 787 are supposed to flex . It would not be very nice if your fuselage flexed so much.

But, then this isn't a pylon we're talking about. The AVEL IIRC has to apply something like 40Gs to eject the missile and as the name suggests its designed for the 150kg AMRAAM not the 500kg JSOW (in F-35's case).

Yes that is right. But the 40G requirement rises from being able to launch the AMRAAM through the entire flying envelop, so that it can pierce through the boundary layer and to a distance beyond the plane (I have forgotten the distance). For A2G munition one doesn't need that king of acceleration. You might find this discussion interesting.

Even with the F-35 the ASRAAM are going to be on external pylons. We will have to decide what goes internally and what goes externally.

The F-16, F-18 and Harrier II yes. Its can't really replace the A-10; the squadrons will probably be re-equipped with it and their operational role suitably modified.

I pointed you to official declassified documents. It is upto you to believe it or not.

The looks don't matter. Yes the requirements for a AF F-16, a naval F-18 and a STOVL Harrier II are different. But, the F-35A, F-35B and F-35C ARE different. 80% parts are claimed common, but the fact that the F-35A weighs 13.3 ton empty while the F-35C weighs 15.8 tons tells me, the CTOL variant isn't making allowances for a navalized version. The F-35C's wing area is almost 50% more than the F-35A. Compare that to a 'practically new' Super Hornet which has a 25% larger wing area than the Hornet. If I said the Rafale was intended to replace the Mirage-2000, would you disagree on the basis that the Rafale-M exists. Or that the Gripen would stop being a replacement to the Viggen if the Sea-Gripen materializes.

I see your point that there is many a slip between the cup and the lip. But F-35C houses the LiftFan, Engine to fan driveshaft, three-bearing swivel module (TVN), roll posts. all these are heavy machinery. The wing is 50% bigger not just for the added weight but also for providing lower landing speeds on ACs.

As far as I have read they want a strike aircraft to complement the FGFA. Ofcourse it should be able to defend itself if attacked. It should be multirole to only that extent. I hope they stick to that rather than making it a jack of all trades and master of none.

As opposed to? I'm assuming it will have an AESA and the weapons bay will accommodate air-to-air weapons. That about brings it at par with the F-35 in terms of operational flexibility. If anything its the air to ground equipment like an internal/dispersed IRST system that will lead to any bloat. Point is its not as simple as making a trade-off between A2A and A2G capabilities. A super-cruising aircraft will be able to lob both missiles and PGMs a greater distance. A larger weapons bay will allow the aircraft to carry more weapons of either kind.

AESA-so? Are AESA's considerably heavier than other radars. I think not.
I pointed it out to you why going for a single engine design made F-35 thicker. It's height of the fuselage is not much bigger than the diameter of it's engines. With the Kaveri the diameter is 3/5 of the F-135/136!

Thats only in your mind. IAF has strictly said that it has to be under 25 T. ADA has said 20T. You are throwing your hat around.

One could say the GoI/Armed Forces will do what they do, therefore BRF is redundant. The design is very far from being finalized and the crux of this debate is my questioning the viability/efficacy of a stealth fighter with a MTOW of 20 tons. The IAC-1's design grew from a proposed 20,000T to 37,000T to a further 40,000T - I don't think the AMCA's design has been frozen either.

There was a design given by the HAL/ADA which pegged the AMCA at 16-18T. IAF didn't like it. It was not on the basis of its payloads, but things like "semi-stealth" yada yada... IAF said give a fifth gen plane under 25T that is an extra allowance of 25-40%. Do you think it is not achievable. You seem to be suggesting all the guys at ADA/HAL/IAF who designed the preliminary prototype didn't have a proper idea of what we are speaking.

Here are you referring to the maximum load that can be carried by the aircraft (9 tons for the F-35) or the capacity of the weapons bay (4 AAM // 2 x JDAM + 2 AAM) or both? And just for general idea, what do you think a possible figure for the AMCA's payload will be?

AMCA was supposed to carry 2T of weapons internally and 4-5T of internal fuel. We can only expect the wings to carry 5T-7T or ordinance more. So its payload including internal fuel will be btw 11T -14T. (smack where a medium aircraft should have).

Yes a heavier plane would require design and production but it would be less challenging in terms of not requiring an as densely packed airframe, offer better a better range and payload, a bigger weapons bay (again less complex), longer intakes allowing for an S-bend with lower turbulence, and with a pair of F119s will offer a performance comparable to a re-engined F-22 or PAK-FA. And the downside to this of course, is a higher operating cost.

A smaller plane doesn't necessarily mean higher density. I read somewhere that a general rule of thumb for fighter planes is the useful load is around 1/4th of the MTOW. Ofcourse there is the Gripen on one side and the PakFA on the other, but in most cases I have found the same to be true. If you want AMCA to be capable of carrying 6-8 T of capable load, the 25T will do.
But you are right about the air intakes. That is why you see the air intakes of Rafale and EF underneath the cockpit itself. It will be interesting where the AMCA's intakes end up. I think it will not be very different from the CAD drawings we have seen so far.

[abhik]

As far as I have read they want a strike aircraft to complement the FGFA. Ofcourse it should be able to defend itself if attacked. It should be multirole to only that extent. I hope they stick to that rather than making it a jack of all trades and master of none.

That is not true, AFAIK the IAF has always asked for a full multi role fighter. I think you are unnecessarily harping upon the the 'Medium' part from the angle of weight rather than capability. Being a stealth fighter in the air-to-air role it would be required to carry a certain number of AAM internally to effectively perform its role. Also in normal operations it would have to do with out external fuel tanks and carry all the fuel it would require ordinarily internally i.e it is expected to carry the same amount of fuel that its analogous non-stealthy aircraft. This is something that is very apparent in all the current stealthy fighter designs(f-22,JSF, PAK-FA). The IAF would have to first give the detailed requirements (expected of a medium sized fighter) w.r.t weapons carried(internally and externally), range, electronics and sensor package (side, rear facing radar? 360 degree IR coverage) amongst others. You cant really turn that around and say start with a design of x weight and accept the capabilities whatever is possible in this weight.
I'm afraid ADA might be doing the same with by selecting what is basically the Rafale's engine and then be tied down to designing a fifth gen stealth aircraft with similar weight etc. as the Rafale.

[Indranil]

i) how much lift will it generate in level flight? At any positive AoA, the lift generated with have a drag penalty.

ii) how much is the additional lift generated with a wider flat bottomed fuselage vis-a-vis a 'normal' fighter like this.

Great questions for an ignoramus such as myself. However one answer that I have in my mind (right or wrong) is "How much surface does the air see or feel?" If the air sees (or feels) 30% of the undersurface from fuselage alone then 30% of the lift in level flight "in clean condition" could be generated by the fuselage.

From the picture below it appears that at least 30% of the surface area that the air "sees" is fuselage
http://www.examiner.com/images/blog/wys ... ighter.JPG

What happens when you change the AoA is another matter. I don't know.

Shivji you are right. Except your 30% area = 30% life is an over simplification. The fuselage is not as "clean" as the aerofoil of the wing and hence is not as effective as the wing in producing lift.

At high AoA it acts just like a wing. Viv is right if you go for high AoA there is high induced drag and lift induced drag. There is flow separation etc etc. But flow separation over the body is way later than the wing, because of the nose. But something else happens much faster, "induced airflow separation".

by the way here are 2 more famous examples

[Indranil]

As far as I have read they want a strike aircraft to complement the FGFA. Ofcourse it should be able to defend itself if attacked. It should be multirole to only that extent. I hope they stick to that rather than making it a jack of all trades and master of none.

That is not true, AFAIK the IAF has always asked for a full multi role fighter. I think you are unnecessarily harping upon the the 'Medium' part from the angle of weight rather than capability. Being a stealth fighter in the air-to-air role it would be required to carry a certain number of AAM internally to effectively perform its role. Also in normal operations it would have to do with out external fuel tanks and carry all the fuel it would require ordinarily internally i.e it is expected to carry the same amount of fuel that its analogous non-stealthy aircraft. This is something that is very apparent in all the current stealthy fighter designs(f-22,JSF, PAK-FA). The IAF would have to first give the detailed requirements (expected of a medium sized fighter) w.r.t weapons carried(internally and externally), range, electronics and sensor package (side, rear facing radar? 360 degree IR coverage) amongst others. You cant really turn that around and say start with a design of x weight and accept the capabilities whatever is possible in this weight.
I'm afraid ADA might be doing the same with by selecting what is basically the Rafale's engine and then be tied down to designing a fifth gen stealth aircraft with similar weight etc. as the Rafale.

Wasn't AMCA's mandate to replace the Jaguars and the Mirage 2000s. I remembered it that way. but after you asked I went and asked Google chacha. And all his first page stories said the same. Then it is supposed to be a strike aircraft, no? Also, I think that you missed it but IAF has provided its ASR quite clearly somewhere in the middle of 2010. Here are some links
Click, click, and click.

Brings me to the question, where did you come up with this multirole roadmap? All modern day strike fighters are also decent A2A platforms. But there is always a primary goal. This was so much so that French and the rest of the consortium parted ways.

And sir the medium doesn't come from me! It is clearly in the IAF ASR! I am only a simple abdul only

[abhik]

Wasn't AMCA's mandate to replace the Jaguars and the s. I remembered it that way. but after you asked I went and asked Google chacha. And all his first page stories said the same. Then it is supposed to be a strike aircraft, no? Also, I think that you missed it but IAF has provided its ASR quite clearly somewhere in the middle of 2010. Here are some links
Click, click, and click.

Brings me to the question, where did you come up with this multirole roadmap? All modern day strike fighters are also decent A2A platforms. But there is always a primary goal. This was so much so that French and the rest of the consortium parted ways.

And sir the medium doesn't come from me! It is clearly in the IAF ASR! I am only a simple abdul only

Again no where dose it say that the IAF wants a strike aircraft(I do remember reading that the IAF wanted a multi role and not a strike aircraft some time ago but cant find it now, anyway). That the AMCA is going to be inducted when the Jaguars and Mirage 2000 are going to be retired should not be construed as it going to be going to be a strike aircraft.
Also I find the the "IAF issues ASR for AMCA" news phony. Such an important mile stone and there is absolutely no coverage in mainstream media or well known defense journalists?

[vic]

This thread has very informative posts. I have a layman enquiry. The strike range of F-16, Mirage, LCA, Gripen was roughly around 700-1000km hi-lo-hi with 2 tons of payload. The New Gripen, LCA Mark-2, Rafale, EF, Latest F-16 should be around 1500km. It is said that F-35 range would be around 2500-3000km due to huge amount of internal fuel apart from possible external carriage. So, I wonder what category of strike range AMCA would fall into? 1500km or 2500km??

[Indranil]

Again no where dose it say that the IAF wants a strike aircraft

Rightly so.

(I do remember reading that the IAF wanted a multi role and not a strike aircraft some time ago but cant find it now, anyway).

I will be glad to know better.

That the AMCA is going to be inducted when the Jaguars and Mirage 2000 are going to be retired should not be construed as it going to be going to be a strike aircraft.

Till now I have read that they would replace the Jaguars and Mirage 2000s. Also we would have no dedicated strike aircraft in the inventory!

Also I find the the "IAF issues ASR for AMCA" news phony. Such an important mile stone and there is absolutely no coverage in mainstream media or well known defense journalists?

There is nothing wrong in holding on to your view. In fact it rings on me as well. But somehow I have found Aviation week and guys like Vinayak Shetty don't throw crap around. But here's what Vinayak Shetty wrote in support of the multi-role capability of the AMCA. link

AMCA project has per IAF ASR (Air staff requirement) has to be Fully stealth aircraft and also should be a multirole aircraft able to play role of both Air superiority fighter and also be able to carry precision air strikes ,very similar role which Tejas MK2 might have to carry out when inducted into Air force .

Things are fluid, so ideas are flying .

[Rahul M]

>> (I do remember reading that the IAF wanted a multi role and not a strike aircraft some time ago but cant find it now, anyway).

shiv aroor's article.

[SaiK]

http://livefist.blogspot.com/2010/06/st ... edium.html
?

[Rahul M]

As per official documentation by the IAF, it wants the MCA to be a twin-pilot configured multirole stealth aircraft capable of "close air support, all weather interception, air defence suppression, long-range strike, electronic attack, limited command & control and reconnaisance" -- that's the profile from an official IAF wishlist to the ADA last year. That might roll right off the air force's tongue, like off a brochure, but they're deadly serious. Putting all speculation to rest when it officially began dialogue about the MCA in 2008, the IAF said it was not willing to look at a strike aircraft with other capabilities. It wants a fully multirole (preferably, swingrole) aircraft for the job.

http://livefist.blogspot.com/2010/01/in ... craft.html

[Willy]

Wasn't AMCA's mandate to replace the Jaguars and the Mirage 2000s. I remembered it that way. but after you asked I went and asked Google chacha. And all his first page stories said the same. Then it is supposed to be a strike aircraft, no? Also, I think that you missed it but IAF has provided its ASR quite clearly somewhere in the middle of 2010. Here are some links
Click, click, and click.

Brings me to the question, where did you come up with this multirole roadmap? All modern day strike fighters are also decent A2A platforms. But there is always a primary goal. This was so much so that French and the rest of the consortium parted ways.

And sir the medium doesn't come from me! It is clearly in the IAF ASR! I am only a simple abdul only

Well it was posted on BR itself I think that the ADA wanted to develop a strike aircraft but that the IAF had put its foot down and insisted that the AMCA be designed as a multirole aircraft from the begining.

[Indranil]

I think Abhik is right ... I did read around this a bit since he pointed it out today morning.

There is more evidence than not that IAF actually wants a multirole fighter!

Viv's question is actually interesting but in a slightly different way. What all will we choose/will be able to finally integrate within the internal bays?

[NRao]

Nov 10, 2010 :: Top 5 Fighter Planes Under development

1) JSF
2) PAK-FA
3) AMCA
4) J-XX
5) JASDF, ATD-X

[kmc_chacko]

Nov 10, 2010 :: Top 5 Fighter Planes Under development

1) JSF
2) PAK-FA
3) AMCA
4) J-XX
5) JASDF, ATD-X

1) JSF - flight test is already underway
2) PAK-FA - flight test is already underway
3) AMCA - only on drawing board expected TD by 2015-18
4) J-XX - nobody knows
5) JASDF, ATD-X - only planned expected TD by 2014

[Singha]

if history is any indication, JASDF will become costly and behind schedule. Japan will ask for US parts and help. US will sabotage it or make it too costly. ultimately Japan will buy JSF with some japanese avionics (like FGFA) !!

I have more hope that Korea will get its 4.5th gen new fighter done than Japan with its 5th gen.

[Philip]

Singha,the problem that the Japs have realised is that the US is not willing to share with them 5th-gen tech.They wanted the F-22-rejeted by the US and a watered down frightfully expensive JSF will not do,which is why they are going (attempting ) to leapfrog 5th-gen tech of the JSF and design and build their own 6th-gen twin-engined fighter.Their tech-demo fighter is expected to come out in 2014+,which will incorporate some of the tech. required and during flight testing,the other exotic tech will be incorporated incrementally.I guess that they want to validate the airframe and flight characteristics first before infilling the key 6th-gen bells and whistles.The aircraft is not intended to supercruise in its first avatar.One key requirement says AWST is to design and build a slimmer engine,which will incorporate radar blockers,allowing for enough space for an internal weapons bay.

This sounds a mature method of building an indigenous fighter and the AMCA could perhaps learn from this approach.First job,finding a proven engine,build the airframe around it with enough space to incorporate a newer more pwoerful engine with better features,test it and then introduce the latest tech features being developed during flight testing,which will shorten the timeframe required for inducting the aircraft.Even in the auto industry,we see newer models of cars being equipped with proven engines before later avatars arrive with newer engines.The key to success is the choice of engine.Here I would rather go in for a proven foreign engine ,rather than place all our bets upon a home grown product.The LCA is the best example ,where after 30 yrs. of development,we are buying large amounts of GE engines for the same!

[merlin]

The LCA is the best example ,where after 30 yrs. of development,we are buying large amounts of GE engines for the same!

You parrot you

[Singha]

well mitsubishi probably has the expertise to build a fighter engine (pulling in help from MTU and other EU vendors who'd be glad to provide any consultancy or materials necessary). honda also makes small aero engines iirc. unlike these seasoned players, India is not similarly well endowed in engines of any kind, let alone bleeding edge aero engines...

hopefully the GoJ is smart and will avoid any US vendor on this project - may take a while longer to reinvent wheel or find other sources but 400% chances of better success