JSF Delayed Again: Pushed Back 13 Months

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Bgile
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Re: JSF Delayed Again: Pushed Back 13 Months

Postby Bgile » Wed Feb 24, 2010 12:46 am

Karl Heidenreich wrote:Bottom line: is the F35 as powerfull an air superiority fighter as the F 22 is? If it is, then nothing is being lost. But if it´s not, then (money aside) then it´s a mistake.

Regards,


The F-22 is a better air superiority fighter than the F-35. The "money aside" is the problem.

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Re: JSF Delayed Again: Pushed Back 13 Months

Postby lwd » Wed Feb 24, 2010 3:03 pm

Kyler wrote: ...I'll give a great example how the stealth & supercruise are not inter-related with one another at all. The Saab JAS 39 Gripen, the first 5th gen fighter to enter production and service. It was designed to be an advance low cost single engine air superority fighter & ground attack aircraft. While the design does incorporate a few stealth features like RAM, it was not designed nor intended on ever being or could be a true stealth aircraft. The current version is the JAS 39C/D, though Saab is developing the NG version, capable of supercruise by the addition of the F414G engine. This ability is by the addition of shear thurst. No stealth feature helps the NG Gripen supercruise.


But of course this doesn't prove that they are not inter related at all. Indeed it was never my contention that stealth helped supercruise, rather the opposite. For instance you mention powerful engines are needed for supercruise. However engine treatmens are one of the trickier parts of stealth. The bigger the engines the bigger the problem. Or take a look at the F-117 it is shaped for stealth obviously. Imagine trying to push that airframe up to supercruise speeds.

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Re: JSF Delayed Again: Pushed Back 13 Months

Postby lwd » Wed Feb 24, 2010 3:05 pm

Bgile wrote:
Karl Heidenreich wrote:Bottom line: is the F35 as powerfull an air superiority fighter as the F 22 is? If it is, then nothing is being lost. But if it´s not, then (money aside) then it´s a mistake.

Regards,


The F-22 is a better air superiority fighter than the F-35. The "money aside" is the problem.

There's also the question of exactly what missions you want the plane to perform. The M-103 was clearly the most powerful US tank of the 50's. That doesn't mean it was the best choice for equipping the US army by any means though.

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Re: JSF Delayed Again: Pushed Back 13 Months

Postby chcrawfish » Thu Feb 25, 2010 12:46 am

F-22: Air Superiority Fighter
F-35: Strike Fighter

Think of it like the F-15 and the F/A-18
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Re: JSF Delayed Again: Pushed Back 13 Months

Postby Legend » Thu Feb 25, 2010 4:28 am

A very good comparison! I think that F-22s are good for homeland defence... perhaps as that impenetrable wall that always has your back... but the F-35 in the long run is definitely the more efficient for the money. While the F-22 is superior in every way to just about anything at high altitude, the F-35 is perfect for low altitude work due to its compatible capabilities and somewhat innovative maneuvering performance for the B version.
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Re: JSF Delayed Again: Pushed Back 13 Months

Postby Kyler » Sat Feb 27, 2010 4:48 pm

lwd wrote:
Kyler wrote: ...I'll give a great example how the stealth & supercruise are not inter-related with one another at all. The Saab JAS 39 Gripen, the first 5th gen fighter to enter production and service. It was designed to be an advance low cost single engine air superority fighter & ground attack aircraft. While the design does incorporate a few stealth features like RAM, it was not designed nor intended on ever being or could be a true stealth aircraft. The current version is the JAS 39C/D, though Saab is developing the NG version, capable of supercruise by the addition of the F414G engine. This ability is by the addition of shear thurst. No stealth feature helps the NG Gripen supercruise.


But of course this doesn't prove that they are not inter related at all. Indeed it was never my contention that stealth helped supercruise, rather the opposite. For instance you mention powerful engines are needed for supercruise. However engine treatmens are one of the trickier parts of stealth. The bigger the engines the bigger the problem. Or take a look at the F-117 it is shaped for stealth obviously. Imagine trying to push that airframe up to supercruise speeds.


lwd,

Stealth technology is a lot more complicated than you are aware of. True, the F-117 would need a massive increase in thrust to supercruise though again stealth and supercruise are not inter-related. The F-117 was the world’s first true stealth aircraft. It uses a mathematical theory using geometric shapes to bounce radar returns away from the receiving antenna to give it stealth. This first generation stealth is very crude and inefficient. The F-117 couldn't even fly without its advance fly by wire technology. In the mid 80's Northrop and USAF developed a new design process for stealth aircraft using curved surfaces to reflect radar. This technique led to Have Blue & the B-2 Bomber. Their aircraft were much more aerodynamically stable and efficient compared to the F-117. This is the current format used in stealth aircraft like the F-22. You are correct that stealth has been adapted to engines, the best example is the Boeing F-32. Boeing designed the engine inlet & engine face to be stealthy while being fully open, a very difficult feat. Though in the F-22 & F-35 the fan blades are not in direct site of radar, so the engine inlet's job to be stealthy not the front fan section of the engine. Supercruise technology is allowing an aircraft (stealthy or non stealthy) to overcome aerodynamic drag to go above Mach 1 without the use of afterburners. If you went out and bought F-105 and slapped a F-22 engine in it, it probably could easily supercruise. Supercruise is in direct relation to the making of better and more efficient turbo fan engines.

If you really want to understand the influence of stealth on the design aspects of aircraft I would recommend you check out the aviation technology author Bill Sweetman. His books are easy to read and very detailed.
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Re: JSF Delayed Again: Pushed Back 13 Months

Postby lwd » Mon Mar 01, 2010 5:31 pm

Kyler wrote: ...Stealth technology is a lot more complicated than you are aware of.

Possibly but your post doesn't tend to support your opinion stated above.
True, the F-117 would need a massive increase in thrust to supercruise though again stealth and supercruise are not inter-related. The F-117 was the world’s first true stealth aircraft. It uses a mathematical theory using geometric shapes to bounce radar returns away from the receiving antenna to give it stealth. This first generation stealth is very crude and inefficient.

"Crude and inefficient"? In what ways?
The F-117 couldn't even fly without its advance fly by wire technology.

My understanding is that that is not unique in modern combat aircraft.

As far as stealth goes I suspect I know a bit more about it than you do. Both from some of my early work in the radar field and some latter work in signature management.
If you went out and bought F-105 and slapped a F-22 engine in it, it probably could easily supercruise.

Or come apart as you pushed it into regimes that the air frame was not designed for. The point I was making is that both supercruise and stealth impose constraints on the airframe and that these constraints are in some cases not complementary.
If you really want to understand the influence of stealth on the design aspects of aircraft I would recommend you check out the aviation technology author Bill Sweetman. His books are easy to read and very detailed.

I may look them up but a lot of the material simplly isn't available from unclasified sources.


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