Forum: F-22A Raptor

You can get information about variable bypass engines, with discussion on the YF120, here:

http://www2.foi.se/rapp/foir1563.pdf

Laughing

F-16.net Sponsor

Recall a series of jets that came out with a pink primer. Pilots were not too happy with that. Also regarding motors, we went through a problem with getting the A/B to light for a while that eventually got fixed after a lot of expensive investigation, but otherwise engine worked great!

Kryptid wrote:

Sorry for the necro, but I thought it might be better to revive this thread rather than to make a new one.

1) I've seen a photograph of the F-22 from the rear aspect and I noticed that the turbines were visible.

In fact you don't see the F119 turbine, but its radar blocker. not unlike those used on F/A-18E/F. Googling 'radar blocker' will give you idea how it works. Jay Miller's F-22 book has some F119 nudity photos that allows to see some details.

Kryptid wrote:

2) I read on some website that the Russians had experimented with flat nozzles of their own, but that the nozzle resulted in a thrust reduction of about 15% when compared to an axisymmetric nozzle (IIRC). Does the F119 suffer from similar thrust-reduction problems?

Yes, it does.

Kryptid wrote:

Or did the Russians simply design their nozzles "wrong"? From the photograph I saw, the nacelle (on an Su-27, I think) was greatly extended beyond the airframe in order for the flat nozzle to be integrated. It seems like that would have added to weight and reduce efficiency.

It was tested on T-10-26 (LL-UV(PS)) in course of 20 test flights in 1990. Nozzle was designed by Lul'ka NPO and Motor NPO, has shown great IR emission reduction and - a bunch of exhaust trench load problems and 14-17% lost in thrust. Loads problem could be solved using C-C high-temp materials that were not readily available at the moment when USSR collapsed. Giant nozzle size compared to a/c was caused by the reason it was a test article studied for much bigger MFI fighter. Last rumors say it was considered as basis for T-54 or T-60S exhaust system, but I doubt that bomber really needs TVC.

flateric wrote:

In fact you don't see the F119 turbine, but its radar blocker. not unlike those used on F/A-18E/F. Googling 'radar blocker' will give you idea how it works. Jay Miller's F-22 book has some F119 nudity photos that allows to see some details.

I certainly don't know the facts but there was a LONG and heated argument on this forum awhile ago regarding whether the -22 uses radar blockers at its rear. The consensus view seemed to be that it does not and that the white radial structure that is commonly seen is simply part of the afterburner. The discussion goes back and forth for awhile but seems to clear up around page 5.

http://www.f-16.net/f-16_forum_viewtopi ... ocker.html

It's the flame-holder you see in the exhaust.

Now does it have any 'stealth treatments' Shrug

who knows... nobody is going there...

TEG

Kryptid wrote:

Sorry for the necro, but I thought it might be better to revive this thread rather than to make a new one.

1) I've seen a photograph of the F-22 from the rear aspect and I noticed that the turbines were visible. We know that the engine faces are hidden by s-ducts because they would otherwise represent good radar reflectors. It seems like this should be true of turbines as well. However, hiding the turbines using s-ducting behind the engines would be impractical due to the added weight, heating problems, and thrust reduction. Did the turbines represent a problem for engineers when considering rear-aspect RCS? I do suppose that the nozzles could help cover them somewhat, but I don't think they can hide them completely. As far as I know, the hot gases exiting the engine might act as a radar absorber/deflector in itself.

The rear aspect is not too important and the penalties to be paid would likely outweight the benefits I guess most probabey weight, cost, complexity and performance, but I'm certain TEG could elaborate further on that.

Quote:

2) I read on some website that the Russians had experimented with flat nozzles of their own, but that the nozzle resulted in a thrust reduction of about 15% when compared to an axisymmetric nozzle (IIRC). Does the F119 suffer from similar thrust-reduction problems? Or did the Russians simply design their nozzles "wrong"? From the photograph I saw, the nacelle (on an Su-27, I think) was greatly extended beyond the airframe in order for the flat nozzle to be integrated. It seems like that would have added to weight and reduce efficiency.

This flat nozzle was actually the first one the russians tested back then (I think it was 1989). Might be that the original nozzle was in fact retained and the vectoring box just built around it, that would explain its size and performance degration. But don't know for sure about this.

That_Engine_Guy wrote:

It's the flame-holder you see in the exhaust.

Now does it have any 'stealth treatments' Shrug

who knows... nobody is going there...

TEG

The Tiffy and Raffy also have similar "holders." I've counted 16 "rays" (or whatever you call 'em) on each holder on the F-22, 15 on the Tiffy, and 9 on the Rafale.

I'd post pics, but I don't want any black copters hovering over my house......... again. Confused

well, after reading an old 'radar blockers' topic I think I could be wrong with F-22 rear radar blocker idea (aren't exhaust plume good radar target itself judging from SR-71A experience?), so what the sense to hide turbine that produces a tail of unburned fuel particles visible on radar?)

do they exist or not, are these flameholders we see and optical effects playing tricks with our eyes - we will learn one day, but definitely not tomorrow

Like I said, they're just flameholders...

TEG

Forum: F-22A Raptor

Some F-22 questions, ya'll!