LCA: News & Discussions - October 2016

[JayS]

What ADA can do is approach Until /Oierope and get commercially available Electro Hydraulic Actuator instead of the legacy Moog ones they use now and do an easy upgrade and get rid of all the hydraulics etc. Will make life much simpler, liberate space, make internal arrangement less complex and will also reduce weight (by around 300 Kg or so in a LCA sized aircraft) . This can be done for Mk1A , when the are doing internal rearragment and stuff and also putting in the AESA. That way, any maintainability whines about the hydraulics and access concerns will be gone as well. This is an easy low risk way of getting some weight savings, and increasing reliability and also simplifying layout and maintenance.

What's stopping them from using full electric actuators, i.e.: linear motor

I might be wrong. But my guess is its the limit on how much force (or torque) stepper motors (stepper motors for accurate control) could exert - hydraulic must be helping in getting the mechanical advantage from input force to output force. You need them to be reasonably small while supplying few kW of power and many thousands of lbs of force. Second thing is conservatism in Aerospace industry. It takes time to move from something which is well proven to something new. Next step will be total elimination of hydraulic component.

[Rammpal]

What's stopping them from using full electric actuators, i.e.: linear motor

I might be wrong. But my guess is its the limit on how much force (or torque) stepper motors (stepper motors for accurate control) could exert - hydraulic must be helping in getting the mechanical advantage from input force to output force. You need them to be reasonably small while supplying few kW of power and many thousands of lbs of force. Second thing is conservatism in Aerospace industry. It takes time to move from something which is well proven to something new. Next step will be total elimination of hydraulic component.

I love this !
Next, kilo-s of lbs, force, i.e: tonnes equivalent - haven't really seen this, and;
Space, yep, totally agree.
However, all that's required is minor tweaking.
Conservatism - major killer, can't blame 'em.
Same same marine industry, O&G !
Gravy train is always on schedule, and on time - why change !
Major loss that !!
Current linear motor actuators - works of art!
Can only start talking pieze-electric beyond this, vis-a-vis, accuracy !

[Sid]

There is a very informative research paper from NASA from the link shared by Vina on EHA. Read the lessons learned section from this paper.

This technology matured a bit too late in LCA program lifecycle, and adding one more exotic tech (and delays) to it will draw ire from all known unknowns.

http://www.nasa.gov/centers/dryden/pdf/ ... H-2210.pdf

The electro-hydrostatic actuator position feedback tracked well with the position command and the system has flown flawlessly since the addition of the 28 V dc power surge filter to the power control and monitoring electronics unit. The electrohydrostatic actuator did stall twice, as expected, at high hinge moment maneuvers where the external load was greater than the maximum output load. The electro-hydrostatic actuator appears to have more load capability than required by actuator specifications, and has performed as well as the standard actuator throughout the envelope of the F-18 Systems Research Aircraft. General performance of the electro-hydrostatic actuator is good. The fail-safe design and trail-damped mode worked well after three in-flight failures were encountered. Pilots indicate that flying with an electro-hydrostatic actuator on the F-18 Systems Research Aircraft feels the same as if a standard actuator were on board.

[Pratyush]

The tech can always be incorporated in the MK3 is it comes about. Or the AMCA when it is at the prototype stage. Why worry about a design that is 20 years old not having what is the latest & the greatest in the field of aeronautics.

[JayS]

I might be wrong. But my guess is its the limit on how much force (or torque) stepper motors (stepper motors for accurate control) could exert - hydraulic must be helping in getting the mechanical advantage from input force to output force. You need them to be reasonably small while supplying few kW of power and many thousands of lbs of force. Second thing is conservatism in Aerospace industry. It takes time to move from something which is well proven to something new. Next step will be total elimination of hydraulic component.

I love this !
Next, kilo-s of lbs, force, i.e: tonnes equivalent - haven't really seen this, and;
Space, yep, totally agree.
However, all that's required is minor tweaking.
Conservatism - major killer, can't blame 'em.
Same same marine industry, O&G !
Gravy train is always on schedule, and on time - why change !
Major loss that !!
Current linear motor actuators - works of art!
Can only start talking pieze-electric beyond this, vis-a-vis, accuracy !

Man, I find it difficult to comprehend what you wanna say.

[JayS]

Its not worth putting efforts to replace all actuators to save few 200-300kg weight for Mk1A at this stage when existing challenges are overwhelming. May be for Mk2 its possible. We should kick off a small project for developing our own EHA for AMCA now itself.

[Rammpal]

I love this !
Next, kilo-s of lbs, force, i.e: tonnes equivalent - haven't really seen this, and;
Space, yep, totally agree.
However, all that's required is minor tweaking.
Conservatism - major killer, can't blame 'em.
Same same marine industry, O&G !
Gravy train is always on schedule, and on time - why change !
Major loss that !!
Current linear motor actuators - works of art!
Can only start talking pieze-electric beyond this, vis-a-vis, accuracy !

Man, I find it difficult to comprehend what you wanna say.

Either that, or I write 3000 slokas!

[Rammpal]

Its not worth putting efforts to replace all actuators to save few 200-300kg weight for Mk1A at this stage when existing challenges are overwhelming. May be for Mk2 its possible. We should kick off a small project for developing our own EHA for AMCA now itself.

All this discussions, and there's nothing on design philosophy
Why?
Shouldn't that be the ultimate guide ??!

[Indranil]

Vina,

There were test flights were the AoA was relaxed to 26. For them to clear the service aircraft to 26, they have to fly past 26 on test articles. They are proceeding with extreme caution here as it is an extremely non-linear regime, as you might imagine. I recently learned that the ram air intake smoothening is not only related to reduction of wave drag. It helps with cnbeta as well.

By the way, did you guys realize that the LCA SP-3 onwards the ram air intake has been modified to the shape shown in the latest MK2 diagrams. I hated the intakes on the LSP-7 to SP-3. It was ugly, and I knew it must be an interim solution as the NACA duct did not work on the original LSP7.

[Kartik]

What specifically is that shape Indranil? The Mk2 diagrams I've seen seem to be nearly the same as the current one.

[Indranil]

When LSP 7 first flew, the original scoop was replaced by a smooth hump, and NACA inlet for ram air intake.


I think the intake did not work well enough.

So they placed a makeshift scoop on the hump. This continued till SP2



The SP3 and NP2 onwards, you can see that they have changed it. I expect it to be retrofitted to SP 1 and 2.



This is the plan of record for the Mk2s as well/

[Mihir]

Its not worth putting efforts to replace all actuators to save few 200-300kg weight for Mk1A at this stage when existing challenges are overwhelming. May be for Mk2 its possible. We should kick off a small project for developing our own EHA for AMCA now itself.

I say it isn't even worth it for the Mk-II. All-electric actuators are a bleeding-edge product that very few aircraft use (the Dassault Falcon does, for example, but it doesn't need to manoeuvre like a fighter). And their form factor, as far a I know, is still larger than that of hydraulic actuators with similar torque requirements. The focus on the Mk-II should be on reducing program risk by carrying over as many systems from the Mk-I as possible, not applying the latest and greatest technologies from scratch and spending another decade sorting out teething troubles.

[Indranil]

Meanwhile, it is encouraging to see that IAF has set down clear priorities for LCA, even before FOC. It seems BVR firing is more important than the gun firing. That is very interesting, considering that LCA has always be portrayed as point-defense fighter.

[JayS]

Its not worth putting efforts to replace all actuators to save few 200-300kg weight for Mk1A at this stage when existing challenges are overwhelming. May be for Mk2 its possible. We should kick off a small project for developing our own EHA for AMCA now itself.

I say it isn't even worth it for the Mk-II. All-electric actuators are a bleeding-edge product that very few aircraft use (the Dassault Falcon does, for example, but it doesn't need to manoeuvre like a fighter). And their form factor, as far a I know, is still larger than that of hydraulic actuators with similar torque requirements. The focus on the Mk-II should be on reducing program risk by carrying over as many systems from the Mk-I as possible, not applying the latest and greatest technologies from scratch and spending another decade sorting out teething troubles.

Agree 400%. So I said *Maybe*.

[JayS]

Meanwhile, it is encouraging to see that IAF has set down clear priorities for LCA, even before FOC. It seems BVR firing is more important than the gun firing. That is very interesting, considering that LCA has always be portrayed as point-defense fighter.

MY guess is they are very much sure about gun firing certification and thus its being taken lightly. They surely have done some ground testing already.

By BVR you mean Radome issue being sorted out too, right??

[Indranil]

The radome is a done deal. It is working wonderfully. The next awaited update is firing BVRs against live targets. On LCA Navy, it is trapping.

[nachiket]

Meanwhile, it is encouraging to see that IAF has set down clear priorities for LCA, even before FOC. It seems BVR firing is more important than the gun firing. That is very interesting, considering that LCA has always be portrayed as point-defense fighter.

I guess BVR capability is essential for even a point-defense fighter these days. They should have prioritized Derby integration and testing even above integration with Litening pod and testing with other a-to-g ordnance IMHO.

[Kartik]

KH-2014 seen here with two 250 Kg HSLD bombs in the MB stations. As the name suggests, the HSLD (High Speed Low Drag) bombs have sleeker frontal surface area thus has different characteristics compared to conventional MK11 heavier bombs. The separation characteristics of these bombs have been favourable and the accuracy parameters too.

Is there a LGB conversion kit for the HSLD bombs as well?

[naruto]

India Today reports that DAC might approve 83 LCA Mark 1A

http://indiatoday.intoday.in/story/manh ... 03569.html

Deals worth over `75,000 crore are expected to be on the agenda for defence minister Manohar Parrikar-led Defence Acquisition Council including fighter aircraft, combat helicopters and mini-drones for the Army.

During the meeting, the minister, top military brass and senior bureaucrats are also likely to discuss the final version of the policy to decide on blacklisting of firms and individuals indulging in wrongdoings and corruption in defence deals. The biggest item on agenda is expected to be the approval for the procurement of 83 Light Combat Aircraft for the Indian Air Force as part of the government's effort to push Made in India equipment for the armed forces to reduce dependence on imports.

The 83 LCAs, expected to be cleared by the DAC, would be procured from the Hindustan Aeronautics Limited (HAL) and would make for the Mark 1A version of the plane. The project cost is expected to be over `48,000 crore, senior defence ministry sources told Mail Today. The IAF has already placed orders for 20 LCA Mark 1 aircraft which would be more of technology demonstrators but the IAF was more interested in having the LCA Mark 2, which would be a more capable and upgraded version of the indigenous plane in the making for the last over two decades. The HAL would first deliver the Mark 1 aircraft to the IAF and then would produce the Mark 1A in the interim till the time it is ready with the Mark 2 version. The project would give a strong push to the indigenous fighter aircraft industry as this would be the first major bulk production order for the plane.

[Rammpal]

Its not worth putting efforts to replace all actuators to save few 200-300kg weight for Mk1A at this stage when existing challenges are overwhelming. May be for Mk2 its possible. We should kick off a small project for developing our own EHA for AMCA now itself.

I say it isn't even worth it for the Mk-II. All-electric actuators are a bleeding-edge product that very few aircraft use (the Dassault Falcon does, for example, but it doesn't need to manoeuvre like a fighter). And their form factor, as far a I know, is still larger than that of hydraulic actuators with similar torque requirements. The focus on the Mk-II should be on reducing program risk by carrying over as many systems from the Mk-I as possible, not applying the latest and greatest technologies from scratch and spending another decade sorting out teething troubles.

1. On a traditional Engine based hydraulic system and/or EHA(http://www.woodward.com/PrimaryFlightControls.aspx , for e.g.), why is the working pressure staying at 5000 psi (344 bar/352 K !)max. !!?
That's bloody low !

2. Why is it that Everything has to be driven off the main engine, i.e.: can't we get rid off the AMAGB altogether, and go independent, for the auxiliary systems ?
What are we looking at, vis-a-vis, the above;
a) hydraulics
b) electric power ?

Plenty of other options !

[JayS]

1. On a traditional Engine based hydraulic system and/or EHA(http://www.woodward.com/PrimaryFlightControls.aspx , for e.g.), why is the working pressure staying at 5000 psi (344 bar/352 K !)max. !!?
That's bloody low !

2. Why is it that Everything has to be driven off the main engine, i.e.: can't we get rid off the AMAGB altogether, and go independent, for the auxiliary systems ?
What are we looking at, vis-a-vis, the above;
a) hydraulics
b) electric power ?

Plenty of other options !

How much pressure should be there, if 5000psi is low?? Why??

What will drive that independent system?? What plenty other options we have available??

[JayS]

India Today reports that DAC might approve 83 LCA Mark 1A

http://indiatoday.intoday.in/story/manh ... 03569.html

Deals worth over `75,000 crore are expected to be on the agenda for defence minister Manohar Parrikar-led Defence Acquisition Council including fighter aircraft, combat helicopters and mini-drones for the Army.

During the meeting, the minister, top military brass and senior bureaucrats are also likely to discuss the final version of the policy to decide on blacklisting of firms and individuals indulging in wrongdoings and corruption in defence deals. The biggest item on agenda is expected to be the approval for the procurement of 83 Light Combat Aircraft for the Indian Air Force as part of the government's effort to push Made in India equipment for the armed forces to reduce dependence on imports.

The 83 LCAs, expected to be cleared by the DAC, would be procured from the Hindustan Aeronautics Limited (HAL) and would make for the Mark 1A version of the plane. The project cost is expected to be over `48,000 crore, senior defence ministry sources told Mail Today. The IAF has already placed orders for 20 LCA Mark 1 aircraft which would be more of technology demonstrators but the IAF was more interested in having the LCA Mark 2, which would be a more capable and upgraded version of the indigenous plane in the making for the last over two decades. The HAL would first deliver the Mark 1 aircraft to the IAF and then would produce the Mark 1A in the interim till the time it is ready with the Mark 2 version. The project would give a strong push to the indigenous fighter aircraft industry as this would be the first major bulk production order for the plane.

Excellent news.

Some mix up with numbers. Note that this proves that only 20 were ordered so far, as has been confirmed by Tejas FB page admin as well. But the numbers mentioned here do not add up to 120. Though it gives some hope that MK2 for AF is still alive. Hope is not false hope.

[Rammpal]

How much pressure should be there, if 5000psi is low?? Why??

What will drive that independent system?? What plenty other options we have available??

1. Higher pressure - smaller/compact component/device.
2. Relationship between pressure and stress in also Not linear, i.e.: added benefit, i.e.: thinner cylinder wall.

Upper limit ?
Open.

Let's discuss;
1. Commercially available high pressure systems (hydraulic), (non-aerospace, however - O&G), are available for, at least up to 10 kbar, off-the-shelf, maybe 15 kbar - custom.
2. Can hydraulic system on board LCA tolerate leakage ?
It already does !

1. 'leakage' is a must in any hydraulic or high pressure system(high pressure fuel pump, for example) - lubrication.
2. At such operating pressures, aerospace or otherwise, vis-a-vis, quality, doesn't make much difference, as, mistake = chutney.

Independent system options?
Note: best if we could zero in on mission profile, i.e.: ferry, patrol/recce., combat.

1. Dedicated turbo-shaft.
2. ICE
3. Stored energy.

Objective ?
Leave the main engine the hell alone, let her do her job producing 77 kg/s, (or what have you), of high velocity gas off the nozzle.

[JayS]

How much pressure should be there, if 5000psi is low?? Why??

What will drive that independent system?? What plenty other options we have available??

1. Higher pressure - smaller/compact component/device.
2. Relationship between pressure and stress in also Not linear, i.e.: added benefit, i.e.: thinner cylinder wall.

Upper limit ?
Open.

Let's discuss;
1. Commercially available high pressure systems (hydraulic), (non-aerospace, however - O&G), are available for, at least up to 10 kbar, off-the-shelf, maybe 15 kbar - custom.
2. Can hydraulic system on board LCA tolerate leakage ?
It already does !

1. 'leakage' is a must in any hydraulic or high pressure system(high pressure fuel pump, for example) - lubrication.
2. At such operating pressures, aerospace or otherwise, vis-a-vis, quality, doesn't make much difference, as, mistake = chutney.

Independent system options?
Note: best if we could zero in on mission profile, i.e.: ferry, patrol/recce., combat.

1. Dedicated turbo-shaft.
2. ICE
3. Stored energy.

Objective ?
Leave the main engine the hell alone, let her do her job producing 77 kg/s, (or what have you), of high velocity gas off the nozzle.

How having an independent power system for hydraulics is better than taking power out from Engine?? Why do you want to leave engine alone?? Don't have to worry about "leaving engine alone". These power off-take requirements are already factored in the design of the jet engine. Even if you do not take that power out it will not gonna change much in the thrust - its a tiny amount of power.

And how in the hell, higher power create smaller component or thinner cylinder walls?? Higher the system pressure, bulkier the parts become. There are manufacturing limits which limit the system pressure unless leakage becomes too big a component in relative terms. One has to necessarily reduce tolerances for higher system pressure, making the manufacturing very costly.

[Rammpal]

"...How having an independent power system for hydraulics is better than taking power out from Engine?? Why do you want to leave engine alone?? Don't have to worry about "leaving engine alone". These power off-take requirements are already factored in the design of the jet engine. Even if you do not take that power out it will not gonna change much in the thrust - its a tiny amount of power."

Ferry and recce. mode, fine - walk in the park, agreed.
Combat mode, she gets into labour !

LCA isn't there for ferrying, cruising and 'going for the rounds', is she ?



[/quote]

And how in the hell, higher power create smaller component or thinner cylinder walls?? Higher the system pressure, bulkier the parts become. There are manufacturing limits which limit the system pressure unless leakage becomes too big a component in relative terms. One has to necessarily reduce tolerances for higher system pressure, making the manufacturing very costly.[/quote]


Later, as it's a tad more involved to explain, and my vedic stanza reply style won't help that much either

[Rammpal]

An Aircraft-Mounted Accessories Gearbox (AMAGB) has been designed and developed for Tejas. It is a lightweight, single-input, multi-output gearbox, which takes its input drive from engine through a power take off shaft at a rated speed of 16810 rpm. AMAGB has a high power-to-weight ratio and a self-contained lubrication system. It carries four aircraft accessories on its output pads, viz., two hydraulic pumps (60 kW @ 6000 rpm each), one generator (40 kW @ 7950 rpm), and one starter unit. Together, these cater to a major part of hydraulic and electrical power requirements of the Tejas and hence forms a crucial part of its secondary power system.

Salient Features
Power plant : GE-F404-F2J3/Kaveri
Power transmission : 185 kW (250 hp)
Speed : 16810 rpm
Weight : 34.4 kg
Overall dimension : 720 mm (L) x 450 mm (H) x 120 mm (W)

http://drdo.gov.in/drdo/pub/techfocus/o ... nical.html

[JayS]

Now convert that 250hp to Thrust and tell me how much will you gain??

And you will have to install a 250HP engine to produce that power separately. How much will be the weight of that?? How much space it will take??

[Rammpal]

Now convert that 250hp to Thrust and tell me how much will you gain??

And you will have to install a 250HP engine to produce that power separately. How much will be the weight of that?? How much space it will take??

Performance
Maximum power output: 250 hp (190 kW) for take-off, sea level 59 °F (15 °C)
Overall pressure ratio: 6.2:1
Air mass flow: 3 lb (1 kg)/s
Turbine inlet temperature: 1,805 °F (985 °C)
Specific fuel consumption: 0.77 lb/hp·h (0.468 kg/kW·h) at 90% power cruise rating
Power-to-weight ratio: 1.838 hp/lb (3.022 kW/kg)

https://en.wikipedia.org/wiki/Allison_Model_250

Obviously technology has improved much since then !
The, 1 kg/s makes it easier for us to chat.
70 kg/s for F404 IN20
70 x 250 ?
I'm guessing, and yes, it is simplistic, but that really doesn't matter.
anyway, 70 x 250 = 17500.

i.e.: if F 404 IN20 were to be a giant turboshaft, that's how much shaft power she'd produce..... !

http://www.geaviation.com/engines/docs/ ... Family.pdf

On the other hand, though;

Do you realise that ADA/CVRDE had to go through that much pain to install that big a device to extract a measly 1/70th of power from F 404 IN20 ?
And that, pretty much messed up the frontal area of main engine assembly as well.
i.e.: frontal area of engine assembly would be a lot smaller - Without the AMAGB.

And fitting that into LCA hull isn't child's play either !

An independent 250 hp engine(whichever type) would have location flexibility.
A major plus.

[shiv]

An Aircraft-Mounted Accessories Gearbox (AMAGB) has been designed and developed for Tejas. It is a lightweight, single-input, multi-output gearbox, which takes its input drive from engine through a power take off shaft at a rated speed of 16810 rpm. AMAGB has a high power-to-weight ratio and a self-contained lubrication system. It carries four aircraft accessories on its output pads, viz., two hydraulic pumps (60 kW @ 6000 rpm each), one generator (40 kW @ 7950 rpm), and one starter unit. Together, these cater to a major part of hydraulic and electrical power requirements of the Tejas and hence forms a crucial part of its secondary power system.

Salient Features
Power plant : GE-F404-F2J3/Kaveri
Power transmission : 185 kW (250 hp)
Speed : 16810 rpm
Weight : 34.4 kg
Overall dimension : 720 mm (L) x 450 mm (H) x 120 mm (W)

http://drdo.gov.in/drdo/pub/techfocus/o ... nical.html

https://www.youtube.com/watch?v=rtiPiuQ_Lxc

[Gyan]

To discuss LCA, reading this report is mandatory


http://www.cag.gov.in/sites/default/fil ... pter_7.pdf

[Dileep]

About all electric drives:

Electric drives are way more bulky and heavy compared to hydraulic ones (for slow, linear movements). It is a matter of flux density. This issue is normally solved by making things move faster, and then mechanically (including hydraulic/pneumatic) reducing the speed. Of course, this affects reliability.

In a totally different domain (medical, to be precise) I saw an AA cell sized motor going at 80,000 RPM to generate the amount of torque needed to drive wires into flesh. That is the only way to get the slow, linear force needed from such a tiny and light mover.

Find a material that can carry a lot of flux for the core, and a material that can carry a lot of current for the winding, and you get a strong electric motor.

[JayS]

About all electric drives:

Electric drives are way more bulky and heavy compared to hydraulic ones (for slow, linear movements). It is a matter of flux density. This issue is normally solved by making things move faster, and then mechanically (including hydraulic/pneumatic) reducing the speed. Of course, this affects reliability.

In a totally different domain (medical, to be precise) I saw an AA cell sized motor going at 80,000 RPM to generate the amount of torque needed to drive wires into flesh. That is the only way to get the slow, linear force needed from such a tiny and light mover.

Find a material that can carry a lot of flux for the core, and a material that can carry a lot of current for the winding, and you get a strong electric motor.

True. Even the current advent of powerful enough Stepper motors is because of rare earth metal Magnets which are more powerful than conventional ones. But even they are not enough to take it all the way to "All electrical". So EHA are current state of the art. May be advent of room-temperature Superconductors will help in future.

[Dileep]

BTW, Dassault Falcon doesn't have All electric actuators. They just have a roadmap to try. AFAIK, there aren't any production aircraft that have all electric actuators. "More Electric" is what people do.

[Rammpal]

https://www.youtube.com/watch?v=rtiPiuQ_Lxc

Gurudev, that's precisely my point !

Do you see how big the area of that piece is, versus its thickness - structural rigidity challenge.
It'd have input dynamics as well, even during normal operation alone, i.e.: engine modulation.
LCA hull flex, brought about by + and - g forces.

Imagine all that during combat !

Crazy a.s amount of work has gone into designing that stuff.
Objective ?
For a sum total of 250 hp to drive pumps and dynamo ???!

[shiv]

To discuss LCA, reading this report is mandatory


http://www.cag.gov.in/sites/default/fil ... pter_7.pdf

No HAL boss has ever had to be accountable for the delays listed in the pdf. Once you are in a government job your progress is by age alone, not by productivity. In a private company people would have been fired, or the company would have gone bankrupt

[arvin]

Imagine all that during combat !

Crazy a.s amount of work has gone into designing that stuff.
Objective ?
For a sum total of 250 hp to drive pumps and dynamo ???!

Will not that thing consume feul to run and bring down the combat radius? Sacrificing combat radius for hydraulic power. The way it is generating power is the same way the primary engine F404 is doing. So you are duplicating the process and that means the second engine would also require all all additional engine support accessories like feul pump etc. I feel there is no alternative for a gear box.

[JayS]

Gurudev, that's precisely my point !

Do you see how big the area of that piece is, versus its thickness - structural rigidity challenge.
It'd have input dynamics as well, even during normal operation alone, i.e.: engine modulation.
LCA hull flex, brought about by + and - g forces.

Imagine all that during combat !

Crazy a.s amount of work has gone into designing that stuff.
Objective ?
For a sum total of 250 hp to drive pumps and dynamo ???!

So you want to remove this gear box and put a heavier, and bigger engine, with far more reliability and vibration issues of its own in its stead for sum total of 500N thrust increase, which BTW will be negated by the additional weight. On top of it, make provision for an air inlet and exit increasing drag on the airframe?? And the only place to bury this big engine is deep inside the fuselage, can you imagine how much trouble it would be to inspect and service that engine??

We are talking of a light fighter aircraft, not a jumbo jet here.

[Vivek K]

Dr. Shiv, you've apparently not worked in large corporates where you have to "screw up to move up".

[shiv]

Dr. Shiv, you've apparently not worked in large corporates where you have to "screw up to move up".

No. But do those corporates also screw up and still receive endless govt funding? I wouldnt know and would be happy to hear some names/examples.

[Rammpal]

So you want to remove this gear box and put a heavier, and bigger engine, with far more reliability and vibration issues of its own in its stead for sum total of 500N thrust increase, which BTW will be negated by the additional weight. On top of it, make provision for an air inlet and exit increasing drag on the airframe?? And the only place to bury this big engine is deep inside the fuselage, can you imagine how much trouble it would be to inspect and service that engine??

We are talking of a light fighter aircraft, not a jumbo jet here.

'bigger engine ' ?
Bigger than what ?

reliability and vibration issues ?
Really ?
How do you know ?
Have you seen my proposal already, vis-a-vis, detailed design, for you to conclude in that fashion ?
As for the rest of the 'concern' list, don't you think I would have 'spent time' on that already
Seriously now.

".... jumbo..."

Interesting!!
Elsewhere, I presented a fighter jet design with 2 engines, and MTOW of 10 tonnes, and I was laughed at;
Apparently, 2 engines = MTOW , no less than 500 tonnes.

What can I say.