American vs. Russian Nozzle Placement Question...

Take a look at these pictures...
Pay special attention to the exhaust nozzles and how they're arranged.

Russian

MiG 29
Su-27 Flanker
Su-34 Platypus/Fullback
Su-35 Super Flanker

American

F-15C Strike Eagle
F-18 Hornet
F-22A Raptor

On the Russian jets I see wide set engines, but on the American ones I see them nice and tight up together. Is there any reason for this? I'm not saying either's better, but I'm trying to see why both of them stick with one or the other. I can sort of see advantages for each. The wide-set engines give roll TVC much better responsiveness, but the tight engines make the heat sig a bit less spread. Also, I think the tube between the engines on the Sukhoi jets is for a parachute, but if it isn't then an ID would be appreciated.

Can anyone clarify for me why the designs are this way?

[edit on 10/1/2006 by Darkpr0]

I really don't see what your trying to describe, if you look at the nozzles of the F-15 they look the same as the Mig-29's for example, however engine size and aircraft size should also be factored in. Also, if you're going to compare be careful of nozzle pictures from planes which are flying, nozzles fluctuate in size depending on how much thrust you're putting out. So pictures of planes on the ground is the way to go.

And I'm excluding the F-22 for obvious reasons, it's exhaust nozzles work better for 2D TVC and reduce it's overall IR signature, hence their square like look.

How come the F-14 has the sime style as the Russians?

Good question...

What I'm trying to point it is that Russian compared to American planes seem to have wider-set nozzles.

American ones (excluding the F-14 above) have tight-together nozzles, while Russian jets have the wide-set nozzles with something in between. Is there any real tactical value of either?

Darkopr0 you should have made your point clearer I thought you were talking about the actual engine nozzles, instead you were referring to the engine placement. It would have made much more sense to have used the words engine and placement instead of nozzles.

The Russians actually derived their design from the F-14. The space between the engines acts as a sort of lifting surface.

Originally posted by WestPoint23
It would have made much more sense to have used the words engine and placement instead of nozzles.

Fixed

I'm gonna get whacked for the 1-liner.

There is no actual difference as such. As has been pointed out the F-14 has wide spaced engines, on the other hand the MiG 25, MiG 31, Su-15, Su-24 etc have them closely spaced side by side within the fuselage. The point about the space between (as on the F-14/Su-27 etc) providing additional lifting wing surface is correct but I'm not sure that the Russians actually copied the US type. The Russian TSAGI (specialist aerodynamic research bureau like Farnborough or NASA) had been developing this layout since the late 1960's, when the F-14 was being designed.

[edit on 1-10-2006 by waynos]

As waynos said you made a mistake by comparing just 4 planes - Su aircrafts are all variants of one design - if you compared the older gen planes you would realize that both superpowers used both concepts.
I don't know which concept is better but widely spaced engines are better looking IMHO.


[edit on 1-10-2006 by longbow]

Originally posted by Figher Master FIN
How come the F-14 has the sime style as the Russians?

Clearly a proves the point that the F14 is a copy of a Russian type!

Originally posted by WestPoint23
And I'm excluding the F-22 for obvious reasons, it's exhaust nozzles work better for 2D TVC and reduce it's overall IR signature, hence their square like look.

For seemingly the billionth time on this board - THE F22s NOZZLES ARE NOT DESIGNED WITH IR SUPPRESSION IN MIND.



Ok, with that out of the way, onto the thread in general.


Simply put the advantages of wider spaced engines are:

- Better survivability, less chance of one missile taking both out.
- Can use lifting fuselage body between engines, increasing L/D figures for the aircraft.
- Leaves a volume that could be used as a bomb bay - although this option hasn't been taken up by anyone I think.


Disadvantages are:

- Higher moment of inertia in X-axis, meaning slower roll accelerations/responses [not to be confused with roll rates!]
- Unless you do something fancy with the ducts, it tends to limit the nacelle/housing to a straight duct, with everything that infers for radar signatures.


I'm sure someone can think of others...

Originally posted by kilcoo316
For seemingly the billionth time on this board - THE F22s NOZZLES ARE NOT DESIGNED WITH IR SUPPRESSION IN MIND.

Uhh... you're kidding right? For the billionth time... :p

This is for the one line bots who would otherwise be quick on the trigger.

Originally posted by WestPoint23
Uhh... you're kidding right?

Nope, we'd one of the deparment heads of the design team over last year, and he assured us IR supression was not considered in the nozzle design.

Originally posted by kilcoo316
Nope, we'd one of the deparment heads of the design team over last year, and he assured us IR supression was not considered in the nozzle design.

Lucky you, however the nozzles of the Raptor do offer a greater IR reduction then the nozzles of lets say the F-15, whether intentional or not.

Originally posted by WestPoint23
Lucky you, however the nozzles of the Raptor do offer a greater IR reduction then the nozzles of lets say the F-15, whether intentional or not.

Why? Because they are square?


The F-22 may have a lower useful IR signature as it doesn't need to use afterburners to maintain resonable manouverability. It may have a lower IR signature by radar shielding of the afterburner injectors [but I doubt this].

Originally posted by kilcoo316
Why? Because they are square?

Why not? It can't be worse.

Also your forgetting to add the coating and plating of the TVC nozzles to the list of IR reduction features on the F-22 exhaust nozzles.


[edit on 2-10-2006 by WestPoint23]

Originally posted by WestPoint23
Why not? It can't be worse.

Also your forgetting to add the coating and plating of the TVC nozzles to the list of IR reduction features on the F-22 exhaust nozzles.

Uhm, would you please explain why they (square nozzles) would make it better?

Also, why would the TVC nozzles make any difference to the IR signature? The F-15 has an iris nozzle, pretty much the same difference (as far as IR signatures go).


If anything, the IR signature of the F-15 is probably better as the flow can be expanded more with the iris than the 2D F-22 exit duct. If they wanted, they could lower the nozzle pressure ratio [burn less fuel in the afterburner = less heat], but that would result in less thrust - maybe not a route they want to go down.

Uhm, would you please explain why they (square nozzles) would make it better?

Again, it can't be worse, as the F-22 most likely has a lower IR signature then an F-15, even though that includes more than just the exhaust. And from head on I tend to think the F-22's exhaust would better disguise engine heat plume.

[edit on 2-10-2006 by WestPoint23]

Originally posted by WestPoint23
Again, it can't be worse, as the F-22 most likely has a lower IR signature then an F-15,



even though that includes more than just the exhaust. And from head on I tend to think the F-22's exhaust would better disguise engine heat plume.

[edit on 2-10-2006 by WestPoint23]

It has because it does right?



Yeap, the F-22 has lower overall IR emissions from critical areas in the frontal hemisphere than the F-15, by using heat exchangers to draw away the heat build-up at the wing leading edges.


A more efficient combustion design may reduce the amount of unburnt fuel getting into the jet plume [as in, the area outside/behind the nozzle duct], but it certainly isn't a result of a square duct, or the serrated nozzle design (triangle exit thingy in technospeak ).