jgetti

Cancellation or continuation of the GE F-136 'second source' engine for the JSF keeps coming up in the news.

The whole basis of a second source for engines is fueled by two things: First, in the event that one company cannot deliver, another source exists to support the worldwide fleet of JSF's, and second, competition between the two engine sources will keep prices more competitive.

Opponents to the F-136 engine argue that development funds from the Pentagon allotted to GE will take away from money available to buy more JSF's.

What many people don't know is that back in the early days of CALF (Common Affordable Lightweight Fighter) and ASTOVL (which eventually became the JSF program) Lockmart and McDonnell Douglas were in direct competition to develop conventional and STOVL variants of a common airframe utilizing advanced engines concurrently being developed by GE (the present dayF-136) and Pratt & Whitney (the present day F-135).

Lockmart was developing a STOVL variant based off of the F-135 engine which included a vertically mounted lift fan spun by a driveshaft connected directly to the engine.

McDonnell Douglas was developing a STOVL variant based off the F-136 engine, which used diverted airflow from bypass air bled off of the engine to spin a vertical lift fan. McDonnells concept would only work with the GE engine because of the necessity of it's variable bypass ratio, which the Pratt F-135 did not have. McDonnell was far ahead in the design when the Pentagon prohibited use of the GE F136 engine, because they had downselected to the Pratt F-135 as the only engine for the program TO SAVE MONEY.

The McDonnell design wouldn't work with the F-135 engine. The only option for vertical lift at such a late point in the development program was to add a second lift engine which was prohibited by the contract, and hence in the downselect for JSF, McDonnell Douglas was eliminated. This also lead to the demise of McDonnell Douglas, and the eventual sale to Boeing.

Now 10 years later, there's a push to keep funding for the F-136 engine flowing to keep the program alive? WTF!!!! How is it even legal for the Pentagon to do that? Does anyone else see the irony in this??

What also seems ironic is that the engine which put one contractor (McDonnell)out of business due to its elimination is now going to take away aircraft sales from their competitor JSF,CALF,ASTOVL,JAST contractor (Lockmart) due to its reinstatement!

highsea

It was the GAO and Britain that raised all the fuss, not the Pentagon, lol. The F-136 represents a pretty big manufacturing spinoff for RR.

I think it's a good idea to have 2 engines anyway...

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jgetti

And yet the Pentagons acquisition folks couldn't see the benefit themselves, and the subsequent damage it (the elimination and then reinstatement of the F-136 engine) would cause to it's defence contractors?

I would also agree that multiple engine suppliers is both healthy and wise. I think the whole schpeel just goes to show the complete lack of foresight MAJOR need for restructuring in our defence acquisitions.

highsea

A program like the JSF is just so big and there are so many players, that I don't know if you can restructure it into something more coherent.

No matter what you do, you will still piss off someone.

Anon

Personally i'm a fan of GE engines. All the crewdogs i know that've worked Vipers say the GE birds are far more powerful than their P&W equivelants, and supposedly the GE engines are also easier to work on and more reliable.

The_Burning_Kid

Is it just me or are P&W sound always unreliable.... Like the early F-15 engines, F-14 engines, and are usually outclassed by there GE counterparts, yet aren't picked for the job. Maybe I'm being dilllusional or something...

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jgetti

If you're speaking of the F-14 TF-30 PW engines, and their replacement, the GE F110, then your comparing engines built off of technology 10-20 years apart.

The USAF F-15 fleet has had great luck with the F-100-PW family. The GE F-110's seem to be a more sophisticated engine that can perform better, but may be a bit less 'plug-and-play'. Those flying the jets may not even notice a difference, but I'd say the GE equivalent may perform a bit better. The 18 year old who has to maintain the jets though would probably prefer the PW.

As far as the F-22/F-35 engines go, the GE engine development had more risk, as they were developing newer technologies such as the variable bypass ratio. This allows the engines perform better in more situations, but makes them more technically risky and probably more expensive.

The F-136, should they choose to keep it will be an excellent engine, I have no quarrels with that. The Pentagon's lack of foresight as to what implications the termination of a second source engine would have, especially if it were to be revived at a later time, has caused at least one, and probably two defence contractors substantially. Not to mention the fact that it leaves the fleet with the risk of losing it's sole source engine supplier. It cost McDonnell Douglas dearly when they cancelled it, and will now cost Lockmart in aircraft sales if revived.

Had they just kept the engine from the beginning, McDonnell may have gotten the JSF contract, and they'd still have a second source engine that wasn't pulling funds away from the aircraft order. And if McDonnell hadn't won, Lockmart wouldn't have lost aircraft orders as separate money would have been allocated to the second source engine already, and again, they'd still have a second source engine.

Anon

The crew dogs on my site that've wrenched both models of Vipers greatly prefer the GE birds.

And bro, the GE motors put out almost 2k lbs thrust more(each).

The difference btw a PW-229 Viper and a GE F110 "Bigmouth" viper is pretty profound as far as pure "Horsepower" from what i've been told.(the GE bird has over 5000 MORE HP than a PW bird)

jgetti

If you're speaking of the F110-132 compared to an F100-PW229 then you're definately right. If you're speaking of the F-110-129 then I might have to disagree on the profound part.

Anon

Keep in mind, i am only parroting what i've been told by actual Viper pilots and crewdog types man.

I dont know i've ever heard any of them specifically use the word 'profound', but they've definitely made it clear to me there is a very real difference between the two.

The GE bird is putting out 31+k lbs of thrust(the latest version of the GE plant put's out 32,500k lbs ea. in the F-15SK according to published figures) vs the -229's 29,400lbs thrust each.

The GE engine is also a good bit lighter IIRC, and it's a whole lot shorter. The turkey feathers are a lot shorter on the GE birds-thats how you can tell them apart from PW birds externally- and i think the core is too...but im not sure about that part.

1 lb of thrust = 2hp.

So if the GE bird is putting out 31k even(ill be conservative) and the PW bird is putting out 29,400...that's a difference of 3200 horsepower.

To me, 3200 horsepower is pretty profound!

gunnut

How is that number derived?

I figure 2 horses can push a lot harder than 1 lb.

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HistoricalDavid

So a Tu-160's engines generate a total of 440,000 horsepower with afterburner? Compare with the million horsepower (approx) of a Nimitz.

Anon

I have no idea where the eggheads came up with that one, i've just seen it stated oh.....hundreds of times in various magazines, websites, etc.

Try google ye doubting thomas.

JGETTI- I just checked, the GE engine is about 350lbs lighter than a PW -229.(i can get you an exact figure if you want).

jgetti

Which F110 are they putting in the Vipers? the -129's or -132's or both?

The F110-129's we're putting in the F-15's are essentially the same length as the Pratt F100-229's. The nozzles appear to be the same length as well. The Pratts we put in F-15's don't have turkey feathers. They got ripped off too often in USAF service early on, so they just requested that they not be put on. That's why they look 'skeleton-ish'.

I know the F110-132's have a composite core housing, same as the F414's, so yea, I could see it being lighter. I don't think the -129's have that. Do you know which engine that weight came from?

outofshdw

You might want to clarify with your sources which engine types they are comparing. You should be aware of the following:

• The F100 has been around much longer than the F110. Most of the US fleet is currently flying on these early-model engines - F100-100 or F110-220. They were never upgraded to the F100-229 standard (too radical of an upgrade).
• The original F110-100 was a big leap over the original F100-100 (27k thrust versus 23k thrust), but it was also developed more than a decade later. If your references were comparing F100-220 powered F-16s to F110 powered F-16s, they should naturally expect to see a big difference in GE's favor.
• The F100-229 was developed to exceed the performance of GE's F110-100 (29k of thrust compared to 27k). This forced GE to develop the F110-129. Head-to-head, the F100-229 and F110-129 are nearly identical in terms of thrust.
• In open competition for foreign sales, the F100-129 has consistently beat-out the F110-129 for customers. GE has by no means had the upper hand here.
• GE's F110-132 is not operated by any USAF aircraft. It is currently flown only by the United Arab Emirates. There are also no plans to upgrade any USAF F110-129's to the -132 standard. Again, its too radical of a change (they'd have to replace almost the whole engine).
• P&W currently has not direct counterpart to the F110-132. This may place them at a disadvantage in future foreign sales.

In short, both engines have gone through a lot of revisions, and there are a lot of different versions still flying around out there. You need to be careful regarding what you are comparing.