40,000 pounds of trust!

All about the Pratt & Whitney F135 and the (cancelled) General Electric/Rolls-Royce F136
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checksixx

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Unread post06 Oct 2006, 15:09

I was still under the impression they were going to rate it at 40,000lbs. Anyone know?

-Check
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Raptor_One

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Unread post06 Oct 2006, 20:29

A thrust rating is not the same thing as actual thrust output. A thrust rating of the 40,000 lb class probably means anywhere between 40,000 and 50,000 lbs of thrust.
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checksixx

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Unread post06 Oct 2006, 22:35

I'm aware of what it means. I meant operationally. Are they actually goint to rate it at 43,000lbs or are they goint to de-rate it down to 40,000lbs. De-rating aircraft engines is a common occurance. Again...anyone that knows can chime in.

-Check
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Raptor_One

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Unread post07 Oct 2006, 01:09

checksixx wrote:I'm aware of what it means. I meant operationally. Are they actually goint to rate it at 43,000lbs or are they goint to de-rate it down to 40,000lbs. De-rating aircraft engines is a common occurance. Again...anyone that knows can chime in.

-Check


It's very misleading talking about uninstalled, sea level static (SLS) performance of an afterburning turbofan that will go into a supersonic fighter. The performance of the F135 installed in the F-35 is a very different ballgame. It will certainly put out less thrust at SLS conditions when installed in the airframe. A fighter's performance throughout its entire operational envelope is very important, so the impact of making the engine run cooler (via reduction of the fan turbine inlet temperature or FTIT, I believe) has to be evaluated throughout the entire operational envelope. If peak performance of the engine throughout the entire envelope is more than what the USAF deems necessary, then the engine can be "de-tuned" to provide longer life. Perhaps it's possible to selectively "de-tune" the engine in certain parts of the envelope, but not others. So if the engine is providing more than enough thrust at low altitude but just meets requirements at medium and high altitude, there might be the option to run the engine cooler at low altitudes and then ramp up to peak temps above some specified altitude (or static pressure... whatever). I really couldn't say.

I guess what I'm trying to say is that it's not a simple matter. You generally don't see the first iteration of an engine family (i.e. the -100 model) de-tuned. They're usually just up to speed if not slightly behind desired levels. The F100 and F110 engines were sufficiently mature by their -229 and -129 iterations, respectively. With the F110-GE-132, customers can choose whether they want better performance (above -129 levels) or stay with the already impressive -129 performance levels but with increased longevity. By the way, I'm talking about war-time performance here. It's my understanding that some users will de-rate their engine's performance for peace time and then up them to "normal" levels in wartime. I'm also not talking about "war emergency power" or "max power" levels like the F-15/F-16 used to have with the F100-PW-100/200/220. Those were time limited features and only to be used when absolutely necessary. I'm pretty sure those features were removed for the -229 and on both F110-GE-100 and -129. I'm talking about the engine thrust used when going to war on a day in and day out basis.

I'd be surprised if the F-35 (any variant) already has so much excess power with the first operational variant of the F135 that derating its performance is already on the minds of military planners. Also, the fact that significant weight reduction was carried out for the F-35B (and applied to the other variants as well) tends to point to a lack of necessary thrust for vertical and/or short take-off. That's just my impression though.
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sprstdlyscottsmn

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Unread post07 Oct 2006, 01:44

hmmmm
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asiatrails

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Unread post07 Oct 2006, 05:46

The difference between test cell thrust and installed thrust is due to installation effects, the big ones being intake efficiency and bleed loads, a 3.,000 LB difference seems high but is probably accurate just to keep some power in reserve.

As to special ratings for engines, yes they exist, however as Raptor One says you have to pay in reduced service life.

The F135 has already had a turbine EGT increase.
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checksixx

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Unread post07 Oct 2006, 18:03

Raptor One and asiatrails...Good info, thanks. But basically your saying it's anyones guess right now as far as what I posted...right?

-Check
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Unread post07 Oct 2006, 22:18

checksixx wrote:Raptor One and asiatrails...Good info, thanks. But basically your saying it's anyones guess right now as far as what I posted...right?

-Check


What I was trying to say is that uninstalled SLS thrust ratings are misleading. Just because an engine has a seemingly high uninstalled thrust at SLS conditions doesn't mean installed performance at, say, Mach 1.2 and 20,000 ft is going to be equally impressive (in a relative sense). The original F100-PW-100 on the F-15A had slightly higher uninstalled SLS thrust relative to the F100-PW-220 on the F-15C. But the -220, aside from having digital electronic engine control, put out more thrust throughout most of the F-15's flight envelope. The F-15C with -220 engines performs better than the F-15A with -100 engines under just about all circumstances if I'm not mistaken. Faster, better acceleration, care-free operation, etc.
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asiatrails

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Unread post08 Oct 2006, 05:07

checksixx wrote:Raptor One and asiatrails...Good info, thanks. But basically your saying it's anyones guess right now as far as what I posted...right?

-Check


Correct, intake dynamics and boat tail drag will show if the propulsion system, of which the engine is a significant part, has the power to push the airframe to meet the target performance points.
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Happy_Gilmore

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Unread post31 Oct 2006, 23:54

Will these engines ever be available for other fightes, say Viper and Eagle?


I was just answering the question that was asked, minus the subsequent and mundane details, I stand by my comment.
I see this engine every day and marvel at it's amazing physical dimensions, it's really a thing of beauty.
I work with a bunch of guys from the X-35 and X-32 programs, I'll be asking questions tomorrow.


Bottom line is who cares if it doesn't fit?



Will these engines ever be available for other fightes, say Viper and Eagle?


This question is what started this whole thread so obviously someone does.
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sferrin

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Unread post01 Nov 2006, 00:45

Happy_Gilmore wrote:
Will these engines ever be available for other fightes, say Viper and Eagle?


I was just answering the question that was asked, minus the subsequent and mundane details, I stand by my comment.
I see this engine every day and marvel at it's amazing physical dimensions, it's really a thing of beauty.


What's amazing about it's dimensions?
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dwightlooi

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Unread post01 Nov 2006, 00:56

sferrin wrote:
What's amazing about it's dimensions?
\

It is practically an F100 sized engine in terms of external dimensions, even though the intake diameter is larger and it makes a lot more thrust.
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Happy_Gilmore

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Unread post01 Nov 2006, 19:03

dwightooi you're dead wrong, not even close my man, when you see this engine (and engine bay) up close and personal let me know, we'll drink beer and talk about it.
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dwightlooi

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Unread post01 Nov 2006, 20:28

Happy_Gilmore wrote:dwightooi you're dead wrong, not even close my man, when you see this engine (and engine bay) up close and personal let me know, we'll drink beer and talk about it.


Really? Let's compare the measurements

F100
Length: 191"
Diameter: 46.5"
Inlet Size: 34.8"

F110
Length: 182~232"
Diameter: 46.5"
Inlet Size: 34.8"

F135
Length: 220"
Diameter: 51"
Inlet Size: 46"


In otherwords, the F135 is within 15% of the F100 length, 9% of its diameter. The F135 is in fact slightly shorter than the longest F110 renditions which are about 232" long. To simplify matters it is reasonable to say that it is an engine that is only about ~10% larger than the classic F100 and F110 engines, and hence in the same size class.

However, it has an intake cross sectional area that is 75% larger. Most of this is due to the fact that the F135 has an intake diameter that is 90% of its overall diameter as opposed to about 75%. It is also a 43,000 lbs engine in its currrent state of development -- 48% and 34% higher thrust than the latest F100s and F110s respectively.
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idesof

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Unread post01 Nov 2006, 22:18

dwightlooi wrote:
Happy_Gilmore wrote:dwightooi you're dead wrong, not even close my man, when you see this engine (and engine bay) up close and personal let me know, we'll drink beer and talk about it.


Really? Let's compare the measurements

F100
Length: 191"
Diameter: 46.5"
Inlet Size: 34.8"

F110
Length: 182~232"
Diameter: 46.5"
Inlet Size: 34.8"

F135
Length: 220"
Diameter: 51"
Inlet Size: 46"


First of all, there is a huge difference between 182" and 232". That's more than four feet of difference in length! What accounts for the variation? Whatever the answer is, they are certainly not interchangable.

Also, it is evident the F135 is a much wider engine than the F100 and F110. At nearly 4.5" wider, there is no way the F135 fits in an engine bay designed for the F100/F110. Moreover, there is a whopping disparity in inlet size.

With the latest F100 and F110 variants developing more than 35,000 lbs. of thrust (sea level static), I hardly think there is a particularly good reason to adapt either the F-16 or F-15 to take the F135, which would be structurally impossible anyway.
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