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P&W confirms stealthy augmentors of F119, F135

flateric

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Sferrin must remember these discussions with insiders at f-16.net...

http://tinyurl.com/3nh2wnu

Screech, the F135 and the JSF Engine War
Posted by Graham Warwick at 3/17/2011 1:33 PM CDT
For those of us who thought screech was the noise made by GE/Rolls and Pratt & Whitney in their war of words over the JSF second engine, here's the background to comments made this week about screech problems with the F-35's F135 engine.

Testifying before the House Armed Services Committee on Tuesday, JSF program executive officer Adm David Venlet said afterburner screech on the F135, which prevents the engine from sustaining full thrust, "caused us to avoid certain portions of the flight envelope." Instead, F-35s have flown to other points in the envelope to keep flight-test going. Kits are being installed to overcome the problem, he said.

So what is screech and what's the fix?

Pratt says screech is a phenomenon caused by pressure pulsations in the afterburner at low altitude and high speed. The problem was discovered during development testing around March 2009, having previously been encountered - and solved - in the F-22's F119 engine, from which the F135 is derived.

Pratt points out that the F119 and F135 are the only production engines with stealthy augmentors. Their design eliminates conventional spray bars and flame holders and integrates multi-zone reheat fuel injection into curved vanes that block the line-of-sight to the turbine.

Building on its experience with the F119, the fix for the F135 includes "minor hardware changes to the fuel system, reduced aerodynamic leakages and upgraded software," says Pratt, adding that the modified engine "now provides full max augmented thrust throughout the flight envelope."

A kit has been developed for flight-test engines, and two have been modified. The production configuration will be validated this year in both the CTOL/CV and STOVL variants of the F135, Pratt says.

I have asked GE/Rolls whether their F136 has a screech-free stealthy augmentor. Watch this space for their answer.

And here it is:

GE/Rolls says the F136 has "no known" screech problem, but acknowledges it is four years behind Pratt in development. An augmented F136 was demonstrated recently to the JPO on its Evendale test stand without experiencing screech, but the engine has not flown yet.

GE/Rolls also points out that afterburner screech was a problem of fighters long before stealth came along...
 

sferrin

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You must have missed this thread:

http://www.f-16.net/f-16_forum_viewtopic-t-15287.html


;D
 

flateric

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oh. damn. rare vizitor there lately
 

sferrin

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flateric said:
oh. damn. rare vizitior there lately
I felt like a person who'd seen a flying saucer but I didn't want to scan the shots in Jay Miller's book and show them. :)
 

flateric

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I have this Jay's book of course. What can I say...some guys follow OPSEC rules
 

sferrin

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flateric said:
I have this Jay's book of course. What can I say...some guys follow OPSEC rules
Except these don't really qualify as they were mentioned in the press and shown in Jay's book years ago. ???
 

SOC

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sferrin said:
Except these don't really qualify as they were mentioned in the press and shown in Jay's book years ago. ???
They sort of qualify. The shots right up the nozzle of the F119, showing the LO fixtures, are some of what the USAF realized after the fact shouldn't have been published.
 

flateric

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sferrin said:
Except these don't really qualify as they were mentioned in the press and shown in Jay's book years ago. ???
I'm talking of previous discussion at f-16.net of blockers existence and some replies.
 

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Pratt points out that the F119 and F135 are the only production engines with stealthy augmentors. Their design eliminates conventional spray bars and flame holders and integrates multi-zone reheat fuel injection into curved vanes that block the line-of-sight to the turbine.

Give an engineer paper, not an aviation week article.

Thank you, Next...
 

flateric

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if Graham Warwick, directly stating that he's citing P&W representative, is not a credible source for you, find Aronstein and Piccirillo F-22 book where augmentor part on F119 cutaway for some reason filled with black

from P&W site
The F119 introduces a number of advanced technologies such as integrally-bladed rotors; burn-resistant, lightweight titanium components; integrated steath features; and a pitch-vectoring exhaust-nozzle system that greatly enhances maneuverability.
 

Spring

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Lack of common sense is funny

Why would you want a 'blocker' that looks exacly like a flameholder, covers exacly the same area and geometry.

And no a PW 'represantive' is not a realiable source, at least for a guy that have been 3 years reading industrial technical manuals....

Is my opinion...He that hath ears to hear, let him hear.
 

flateric

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Spring said:
Why would you want a 'blocker' that looks exacly like a flameholder, covers exacly the same area and geometry.
once more - can you read?
"Their design eliminates conventional spray bars and flame holders and integrates multi-zone reheat fuel injection into curved vanes that block the line-of-sight to the turbine."

radar blocker in F119 is not my idea fixe, it was just an information that appeared long ago and recently got another confirmation

Spring said:
And no a PW 'represantive' is not a realiable source, at least for a guy that have been 3 years reading industrial technical manuals....
so what? that now qualifies as a reason to believe you more than to Warwick?
 

sferrin

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Spring said:
Lack of common sense is funny

Why would you want a 'blocker' that looks exacly like a flameholder, covers exacly the same area and geometry.

And no a PW 'represantive' is not a realiable source, at least for a guy that have been 3 years reading industrial technical manuals....

Is my opinion...He that hath ears to hear, let him hear.
Shhh. Don't listen to them, it's a conspiracy. ::)
 

flateric

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Stephen Morford
Director, Aerodynamics at Pratt & Whitney

Current
  • Director, Aerodynamics at Pratt & Whitney
Past
  • Manager, Acoustics, Inlet & Nacelle Aerodynamics at Pratt & Whitney
    Team Leader, F119 Augmentor at Pratt & Whitney
    Manager, Low Emissions Combustor Technology at Pratt & Whitney
 

overscan

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Team leader on the F119 augmenter? Pah! What would he know about the F119 aug... oh.....

Spring: apologies are in order I think.
 

InvisibleDefender

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These are not the augmentors that you are looking for ... carry on ...
 

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flateric said:
radar blocker in F119 is not my idea fixe, it was just an information that appeared long ago and recently got another confirmation
In PW's statement I read "stealth features" and "stealthy augmentor".
Do you have any actual reason to assume this is a radar blocker?
Why wouldn't this thing rather be an IR signature reduction device?
 

sferrin

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bipa said:
flateric said:
radar blocker in F119 is not my idea fixe, it was just an information that appeared long ago and recently got another confirmation
In PW's statement I read "stealth features" and "stealthy augmentor".
Do you have any actual reason to assume this is a radar blocker?
Why wouldn't this thing rather be an IR signature reduction device?
"block the line-of-sight to the turbine"

The reason you want to block line of sight is so radars don't see it. Same reason you use S-ducts or radar blockers up front to hide the compressor face.
 

bipa

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...but line of sight blocking may also apply to IR radiation... actually even more so for many configurations.
Radar waves are not such easily blocked, unless there is some pretty serious (and simultaneously high temp) RAS in there.
Seems fairly complicated to me: there must have been a huge RCS benefit at stake to go down this road...
Maybe they were deeply concerned about JEM / NCTR...?
(note, though, that I haven't seen the pictures from the Jay Miller book you mentioned earlier)
 

flateric

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bipa said:
Do you have any actual reason to assume this is a radar blocker?
Why wouldn't this thing rather be an IR signature reduction device?
that may be quite correct of course...

meantime, compare official render to something more closer to reality...

 

sferrin

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Very interesting PDF on the F135. 19 pages. Lots of interesting pictures.

http://tx.technion.ac.il/~jetlab/11thSymposium/f135.pdf

One of the slides:
 

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CammNut

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I have looked up the back end of an F119 and you truly cannot see the turbine. Still not sure how much I can say, but it is not simply a blocker because it serves a function, it's just very cleverly designed.
 

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Sounds to me like you're saying they designed the afterburner flame holder to block the view of the turbine.
 

sferrin

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Sundog said:
Sounds to me like you're saying the designed the afterburner flame holder to block the view of the turbine.
It was described in AvWeak as an integral blocker/spray system. There are pictures of it in Jay Miller's F-22 book but they don't point it out as such.
 

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sferrin said:
It was described in AvWeak as an integral blocker/spray system. There are pictures of it in Jay Miller's F-22 book but they don't point it out as such.
Those may be some of the photos that reportedly irritated the USAF after they were published.
 

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sferrin said:
Sundog said:
Sounds to me like you're saying the designed the afterburner flame holder to block the view of the turbine.
It was described in AvWeak as an integral blocker/spray system. There are pictures of it in Jay Miller's F-22 book but they don't point it out as such.
Hmm, spray system? Aerosols, T-50 style?
 

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I don't know why they're so sensitive about it, there's been a photo on the Tinker AFB site for the longest time of them doing maintainance on the blocker during turbine inspection. This is the upstream side of it.

 

sferrin

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flanker said:
sferrin said:
Sundog said:
Sounds to me like you're saying the designed the afterburner flame holder to block the view of the turbine.
It was described in AvWeak as an integral blocker/spray system. There are pictures of it in Jay Miller's F-22 book but they don't point it out as such.
Aerosols, T-50 style?
??? Could you elaborate?
 

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The T-50 will use an aerosol spray system blanketing the exterior of the engine nozzles for IR signature reduction. This is something different though, what we're talking about here on the F-22 is the fuel injection system (with integrated flame holder and rear aspect *radar* blocker functions) for the afterburner, right?
 

sferrin

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Trident said:
The T-50 will use an aerosol spray system blanketing the exterior of the engine nozzles for IR signature reduction. This is something different though, what we're talking about here on the F-22 is the fuel injection system (with integrated flame holder and rear aspect *radar* blocker functions) for the afterburner, right?
Yes, this for radar.
 

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tacitblue1973 said:
I don't know why they're so sensitive about it, there's been a photo on the Tinker AFB site for the longest time of them doing maintainance on the blocker during turbine inspection. This is the upstream side of it.

There's also this:

http://data3.primeportal.net/hangar/weichao_chen2/f-22a_91-4003/images/f-22a_91-4003_03_of_30.jpg

Granted, it's a YF119 and I'm not sure whether the afterburner section is complete, but the "blades" visible appear to have too wide a chord to be actual LPT blades.
 

CammNut

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That is not how it looks in the F119, for sure. At first glance it appears featureless and impenetrable. The maintenance shot does give you an idea of how it looks from the turbine side.
 
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