tsarkar wrote:From my experience, this is exactly what happens, and what I learnt from those associated with the program is that this is the exact reason for the LCA overweight issue. The sentences here aptly sum it up.
The LCA is "overweight" (which I contest if the 6500kg empty weight is correct) only in relation to the original TDs that flew and which probably aimed for an empty weight of 5500kg with the GEF404 engine and the initial weapon spec per the IAF ASR.
When the final weapon and stores specs came in, I dare say that it would have been quite different from what the design specs at the TD stage assumed. People talk of the R-60 to R-73 change because I guessed it, but why do you assume that only the outer most pylon spec changed ?. The middle, inner and center pylons too would have changed as well. No one talks about that! All that will mean a new structural design (just stiffening the wing against bending and torsion wont do), especially if new systems are added in along the fuselage axis, which most probably happened. Given that, the empty weight growth is not unexpected and is probably well within reasonable limits given that the Gripen has similar empty weight with a similar engine.
The only problem is that IAF ASRs are probably so tough that you need more engine power to meet the original T:W ratios of the TD stage design !
I would think when we talk about weight growth, it is important to keep in mind with relation to what ? The TD bird or the actual ones at IOC. The IOC birds are under the skin, very very different aircraft and airframes from the TD. The "conservativeness in margins" or whatever is part of the reason, but not the whole or even the main one, when you see a close to 20% gain. You need to look at other reasons more closely
Maybe at Lockheed Martin, but not at ND(MB) or ND(V) or IAF BRD or DRDO/OFB.
BRD and OFB kind of places which are probably largely replacement/ spare parts kind of manufacturing ops dont matter and are not comparable. You cant be much off,when you either make parts to drawings or reverse engineer a part from known/similar materials. There is really next to no design. But if you are doing an ab-intio design, then it is a different story.
In the real world, its not so simple. For example, consider the component testing and system integration testing time, effort and cost to the iterations.
Those are largely one time efforts. Since you are a Navy guy and are probably more familiar with ships , so I will give you a ship example. For eg, you are a shipyard and you need to design a 60,000 ton Bulker (say) and the owner says he wants a cruise speed of around 15knots, you probably would look at an equivalent design data published from well known series (BSRA,ABS, etc) and choose one with basic data (lenght, breadth, draft, block, prismatic and other coeffs) and estimate steel weight from the midship section of a similar vessel and put in some allowance for weights and do a first cut estimate of displacement , center of gravity, center of buoyancy etc. Now , if you are designing the ship for a particular certification (Lloyds/ABS/DNV/whatever), you will start doing detail design as per that (and you get the size of the scantlings and skin and everything) and you start specifiying machinery per requirements and other systems and you get a pretty decent estimate of weight and other stuff and then iterate once more to see if you need to adjust the initial data you worked with and do the structural design per certification again and you are pretty much done!
The good thing is that the registrar gives "10 commandments" kind of orders for most major things and takes guesswork out from some very fundamental things. In a warship, you need that kind of design database from experience and so is a different ball game! Same with an aircraft like the LCA. The thing is if you notice, all these are not major efforts UNLESS you build a full ship for every iteration! At design stage it is all on paper /computer memory and can be easily fiddled with in few lines drawn or clicks of mouse. It is always a truth that changes are nearly painless in initial design and the later you are in the cycle of the product, the cost and pain of changes shoot up!.
If there is a lesson in this, it is this. The IAF should have put their heart and minds fully into the LCA. But no, it was a step child/******** child that they in all probably wished would have a still birth and couldn't be bothered with and studiously ignored it as far as possible and were probably more interested in buying more M2Ks or SU-30s! They even used it as a parking spot for people kicked upstairs with a clear exit route out of the IAF shown (like that Air Vice Marshal who went to court on some dispute and he was parked there) . Unfortunately, against all odds, the TD program was successful and then you tried to "productionize" it into a service capable fighter and went through and entire design cycle again. If the IAF had not been so sneering and actually gotten hands on and sepcced the TDs close to what the final requirements were (not a big ask you would agree), you probably would have seen these birds in service around 3 to 5 years earlier and definitely would not see half assed comments like a "3 legged Cheetah"!
This statement of yours further supports the first point made here. Had LCA used off the shelf stuff, we would have ended up with a Mirage 2000. It it didnt, and it mostly uses brand new stuff developed from scratch, for developing this brand new stuff, they ended up doing what Kartik described.
Nah, it was designed with a smaller engine and smaller airframe and lower all up weight, and the off the shelf stuff it used were different (engine and other systems). No way it would have ended up as a M2K. It was always going to be a different plane.
Well the world has more three legged cheetahs that you would have imagined hain?
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