Forum: F-35 Lightning II

Agreed JT, the F119's thrust is still generalized, but everyone should consider a modified F100 made over 37K during a test run; it used a version of the F119's fan section, and some of it's other technologies.... The F100-PW-232 would have been the production version (if it saw production) and was rated at 32K.

The F135 has been quoted in the 43K class, but has demonstrated increased thrust margin during tests. STOVL thrust is always quoted as such, and includes the engine, liftfan, and roll-posts in a total product. It is LOWER than the MAX power of the same PW-600 engine taking off in CTO mode.

I have to say here the T-50 is using old engines modified and modified and re-engineered to provide more power. The F119 was a NEW engine, that was re-engineered into another NEW engine, the F135. Both motors will have future thrust growth capabilities if the aircraft design/weight/operations require it. Look at the F100, started out in 1968 with barely 23K MAX. In it's highest power tests in the early 1990s it reached 37K! If PW can take a late-60s motor and pump an additional 60% thrust through it, imagine what they can do with the 2000s F135 and it's thrust margin!

We won't start in on the longevity of the Russian motors, or the motor issues of Su-30MKI from India that attended Red Flag here in the states....

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TEG

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rkap wrote:

The thrust to weight of the engine is more important than raw thrust.

This is just wrong. Specific thrust is indeed important for aircraft design, but the weight of the plane on the tarmac or the drag of the plane during flight doesn't give a rat's rear end about "specific" thrust, just thrust.

The French have plenty of experience hotrodding their production motors. Snecma always ran them hot. Stunts like rapping out motors past their engineered specs don't win wars, logistics do. I'd feel better to have an enduro motor than a drag racer. Save the hotrods for the stunt drivers.

That_Engine_Guy wrote:

Agreed JT, the F119's thrust is still generalized, but everyone should consider a modified F100 made over 37K during a test run; it used a version of the F119's fan section, and some of it's other technologies.... The F100-PW-232 would have been the production version (if it saw production) and was rated at 32K.

The F135 has been quoted in the 43K class, but has demonstrated increased thrust margin during tests. STOVL thrust is always quoted as such, and includes the engine, liftfan, and roll-posts in a total product. It is LOWER than the MAX power of the same PW-600 engine taking off in CTO mode.

I have to say here the T-50 is using old engines modified and modified and re-engineered to provide more power. The F119 was a NEW engine, that was re-engineered into another NEW engine, the F135. Both motors will have future thrust growth capabilities if the aircraft design/weight/operations require it. Look at the F100, started out in 1968 with barely 23K MAX. In it's highest power tests in the early 1990s it reached 37K! If PW can take a late-60s motor and pump an additional 60% thrust through it, imagine what they can do with the 2000s F135 and it's thrust margin!

We won't start in on the longevity of the Russian motors, or the motor issues of Su-30MKI from India that attended Red Flag here in the states....

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TEG

With that kind of stats, one could reason that an F-4 could have 74k lbs thrust. It was, in a few cases, fitted with the PW1120, which was really a modified and less-powerful F100. Imagine if we had kept the RF-4Cs and given them F100-PW-229s. That would be a recce rocket of Buck Rodgers proportions In Love

southernphantom wrote:

With that kind of stats, one could reason that an F-4 could have 74k lbs thrust. It was, in a few cases, fitted with the PW1120, which was really a modified and less-powerful F100. Imagine if we had kept the RF-4Cs and given them F100-PW-229s. That would be a recce rocket of Buck Rodgers proportions In Love

Brief excursion; doubt a PW1120-?? would have ever developed anything close to 37K, it just wouldn't have had the diameter to handle the airflow. Stock F100s would have never fit the Phantom either, either space or inlet capacity. The Phantom would have been awesome with the PW1120, but it just wasn't to be...

The F414 would be the closest thing to shoe-horn into the Phantom today....

J-79
Diameter-Max - 992 mm (39.06 in)
Length - 5,301 mm (208.69 in)
Weight - 1,749 kg (3,855 lb)

MIL - 52.8 kN (11,870 lb st)
MAX - 79.27 kN (17,820 lb st)

F414
Diameter-Max - 889 mm (35 in)
Length - 3,912 mm (154 in)
Weight - 1,120 kg (2,470 lb)

MIL - 65.64 kN (14,756 lb st)
MAX - 97.86 kN (22,000 lb st)

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TEG

[quote="sprstdlyscottsmn"][quote="rkap"]

Quote:

This is just wrong. Specific thrust is indeed important for aircraft design, but the weight of the plane on the tarmac or the drag of the plane during flight doesn't give a rat's rear end about "specific" thrust, just thrust.

If you are talking about engines only then the higher the Specific Thrust the better. Better for the aircraft overall.
The weight saved there can be used for extra fuel or on a smaller airframe or on extra weapons. If not why the hell do they worry so much when the weight of an airframe and systems starts to go over the design weight. e.g. All the work they put in to save a few hundred KG on the F35.
The lighter you can keep an aircraft the better.
Shorter takeoff etc. on and on.

All I was saying is the slightly less thrust of the 117 in many ways is balanced out by the fact it is about 350kg lighter than a F119.

True or false.

For the Engine Guy or anybody with enough understanding to answer.
Below my understand of the Russian Engines for the SU35 and PakFa etc.
Not that complicated if you ignore all the different names they come up with for often what is the same engine more or less.
There ultimate engine is to be a variable bypass engine - what advantages does that have.

In 1985 the Russians started work on the AL-41F variable-bypass ratio turbofan engine for the Mig144 designed to supercruise. It is similar in terms of technology to the not built YF120 and the almost got there F136.
The proposed General Electric YF120 was a variable bypass next generation engine. I understand so was the F136.
In effect a generation ahead of the older fixed bypass technology used on the F119.
It lost out initially to the older fixed bypass technology used in the F119 to avoid risk I understand.
[Maybe that was a good decision or we could still be waiting for an engine for the F35.]
After all they started in 1996 on the F136 and it was no where near ready when called off despite having funding all the way through.

The Russians though never gave up with the development of there variable bypass engine, the AL-41F. A development slowed by about 15 years lack of money in the 1990's and early 2000's.
Having got some money they continued and in 2007 they anounced initial low rate production of the Al-41F and it was considered as an engine for the SU34. That option was not taken up by Sukoi I assume because they did not consider it proven at the time.
The size problems they had must have been solved. [GE and Rolls Royce claimed to have solved that problem on the YF120 also the F136].

As an interim measure the hot end technology of the AL-41F core was migrated into the AL-31 resulting in the much improved AL-31 versions. The 117c or 117s and the 117 for the Pak Fa with improved Digital Control etc. This is sometimes called the AL41F-1 or something just to confuse us even though its core is from the AL31 and only the hot end of the AL41F. They call it a new engine - I suppose that is fair enough - a lot of it is new with new digital control etc.
The performance figures for these engines considering there small size and low weight indicates Russia has now caught up almost with the West in terms of performance. Still behind in engine life but that may simply be a trade off to keep the weight and size down to achieve a Specific thrust of about 10.5 to 1. Its specific thrust and fuel efficiency are excellent but its TBO is still only about 4,000hours.
The F135 is the only Western engine to achieve a specific thrust equal to the 117 but it can't supercruise.
Engine experts may be able to tell us if the F135 could easily be converted to a Supercruise engine? Something beyond my understanding.
It also has been reported in Russia the ultimate engine for the Pak Fa has been tested in one of the Prototypes. So it must be close to proven.
This new engine has to be a version of the long worked on AL-41F. Why they change the names all the time is beyond me. [I read where they now call it the Type30 or something.]
To fit the Pak - Fa all size problems must have been overcome. The early test flights in the early 1990's were conducted on a larger test platform so size did not matter.
The original design specifications called for the AL-41F to fit in the T- 10 series but reports says they found it hard to keep the size down enough. It probably would have been OK in the Mig 144 if they ever decided to build it. It was a big airframe.
The Russians now seem confident this new engine ??? [I bet they don't call it the AL41F - it will get a new name just to confuse.] will be proven and ready by 2015 for the Pak Fa - at the latest 2017.
I assume that will be a big achievement if they do achieve it - the first variable bypass military Supercruise engine .
The question is? is a variable bypass engine better and what advantages does it have.
This new engine they say will be in the 180/190kn.- 40,000/43,000lb range and is designed to fit in the Pak Fa. It must be reasonably small.
I assume if it is small enough to do that its weight will also be about the same as the 117 - about 1400kg.

Is a variabe bypass engine the way to go and what advantages could it have over a fixed bypass engine.

rkap wrote:

For the Engine Guy or anybody with enough understanding to answer.

... As an interim measure the hot end technology of the AL-41F core was migrated into the AL-31 resulting in the much improved AL-31 versions. The 117c or 117s and the 117 for the Pak Fa with improved Digital Control etc.
...
The performance figures for these engines considering there small size and low weight indicates Russia has now caught up almost with the West in terms of performance. Still behind in engine life but that may simply be a trade off to keep the weight and size down to achieve a Specific thrust of about 10.5 to 1. Its specific thrust and fuel efficiency are excellent but its TBO is still only about 4,000hours.
The F135 is the only Western engine to achieve a specific thrust equal to the 117 but it can't supercruise. ...

Russia has never been significantly behind the US in "specific thrust." Prior to the F101 I think Russia was even ahead of the US. However, the US could surpass Russia in "specific thrust" by overheating our engines and burning them to pieces faster, just as Russia does. That's one reason why "specific thrust" doesn't matter. What matters is the thrust of the engine vs. the weight of the entire plane. If you add weight to the engine, and it lets you get away with a lighter plane (because you need less accomodations to changing the engine out every few flights), then you come out ahead where it actually matters, despite the heavier engine. The TBO of the 117 is not 4,000 hours. It's 1,000 hours. Its total service life is 4,000 hours, with three complete overhauls during that. And that's if you believe Saturn's claims, which India has found are generaly inflated. I believe the TBO in actual use will be closer to 500 hours.

What made the F135 demonstration of 53,000 lbs. thrust important wasn't that it could make 53,000 lbs. We could probably push it over 60,000 lbs. if we were willing to accept an engine replacement every 1,000 hours. Or push it over 70,000 lbs. if we were willing to scrap it after every flight, like the MiG-25's supposed Mach 3+ capability requires. What's important about the announcement is that the F135 can produce 53,000 lbs. while still having a TBO in excess of 8,000 hours. Part of the low TBO on Saturn engines is that some of their parts have low service lives totally unconnected to the way Saturn burns their engines out faster. So since the engine would need to be overhauled in 1,000 hours just because some of the seals will only last that long no matter how gently the engine is handled, it only makes sense to burn the rest of it out in 1,000 hours too.

Quote:

Engine experts may be able to tell us if the F135 could easily be converted to a Supercruise engine? Something beyond my understanding.

It's actually very simple. There is a belief among some people not in a position to know, that the F119's turbine blades are shaped to accept some degree of supersonic airflow past the compressor face. Can they? I don't know. It's not necessary that it is true, if the intakes of the F-22 are shaped to compress, heat, eject out the shark gills, and slow the incoming air down so the remaining air going into the engine itself is subsonic. But it's interesting if true.

The F135 has a larger diameter than the F119. That means that at the same RPM, the tip of each turbine blade is moving faster on the F135 than on the F119. A compressor can't suck air in faster than Mach 1; all you get is a flat shock wave in front of the turbine and a partial vacuum behind it. So when the blade tips hit Mach 1, you've reached the limit of how much air you can put into the engine (maybe not for the F119; I don't know). Running the engine faster only spreads the shock wave farther down the compressor blades, and no more air goes in. If you combine the speed of the incoming air with the speed of the blade tip, and account for the way compression, and heating of the air raises the speed of sound, there's no way around the fact that the F135's blade tips will hit Mach 1 at a lower aircraft speed than the F119's blade tips. So the answer is: No. The F119 will always be a better supercruise engine than the F135. Or design variable intakes that can slow, compress, and heat the incoming air better, and take the hit in weight, complexity, and maintenance. What matters for supercruise is the whole package, plane and engine.

Quote:

The question is? is a variable bypass engine better and what advantages does it have. ...

Is a variabe bypass engine the way to go and what advantages could it have over a fixed bypass engine.

Engines die because heat from shock compression and burning fuel wears out the parts. Engines undergo Mach stall because their compressor blade tips hit the sound barrier. If you send some of the air around the compressor instead of through it, you can delay Mach stall and/or make due with less shock heating of the air in the intake. With cooler air going into the engine, you can add proportionately more fuel to the air without exceeding the temperature limit of the burner and downstream turbines. And with more cold air going past the burner rather than through it, you can use some of it to cool the hot parts of the engine, allowing you to increase the amount of burning fuel even more. Lastly, when the cold air mixes back into the hot air at the back of the engine, it gets hotter (and the hot air gets cooler). The overall result is a larger amount of air that's less hot; that's more efficient at producing the same thrust. It also has a lower IR signature. That's why airliners have huge turbofans instead of skinny little turbojets; they're far more efficient and powerful. But huge turbofans undergo Mach stall at lower speeds, so fighters can't use them. With variable bypass, you have some turbofan advantages at lower speeds, and then change the bypass ratio to avoid blade tip stalls as the speed increases.

The downside is weight, complexity, and diameter. The bypass air has to have some way to go around the core, and there has to be some mechanism to make the air go in or around as you need it.

GE claimed they could make the F-120 weigh no more than 10 lbs. heavier compared to an ordinary low bypass turbofan engine of similar size. They used a special aerodynamic pressure-based feed system to divert more air massflow to the core as opposed to a complex mechanical sleeve system which constricted the flow to force it through the core. Still, it is indeed true that a variable-bypass engine would be a bit more complex than a simple turbofan engine.

[quote="river_otter"]
Thanks for the detailed reply in language I could understand.
I got the idea anyway about the speed of the turbine blades etc. and the limits that puts on design etc.
You are correct about the 117. I should have said 4000 hour engine life.
I did not think the Indians had the latest engines in there SU30's.
It is only the 117s or 117c they claim the 1000hour TBO for.
No doubt the 117s and the 117 will end up being available for the SU30 in due course.

In summary then it is this:
The Russian engines don't have good engine life. Nobody argues about that including the Russians. [getting better].
They generally are light weight. Good specific thrust.
Building there new engine [??? whatever they call] based on the AL41F with variable bypass will have advantages.
From what Russian sources say size was there main problem with the variable bypass AL41F. The same problem GE and Rolls Royce had to solve.
The original AL41F would have fitted something like the Mig144 demonstrator but once they decided to go for a smaller plane of the T-50 size it could not be used in its current form.
Will it be a breakthrough for them if they can produce a variable bypass engine about the size of the 117 with a thrust of somewhere between 170-190kn. [Lets assume it has a reasonable engine life in there terms.]

To have tested one in the Pak Fa as the head ot there Engine Corporation has said it must be of similar size to the 117 - much the same as the AL31F series of engines.

If they can prove it and no insurmountable problems come up no doubt it also will appear sooner or later in the T-10 series in one form or another.
A small lightweight variable bypass engine with that sort of thrust would aslo surely be valuable in a multi-role aircraft. Mixed ground attack and a supercruise fighter and bomb truck. If I havenot read what you wrote wrongly it will definitely help the plane be more versatile in various performance areas. Or did I read something wrongly. It also could be handy when they build there next Bomber etc. The weight saved can etc. can be used in other areas. From what you say if I have not got it wrong it will help it perform well at sea level and at altitude. The weight saving also can be used for more fuel - better range - more payload - shorter takeoff etc. subject to the wing design etc.
It also would I imagine be of great advantage if ever they wanted to build another quick up and into action interceptor like the Mig31 that can operate well at sea level or altitude.
Is this putting too much value on the benefits of a variable bypass engine or not.
If so would the F136 have given any of these benefits to the F35 or is it more or less set because of its wing design etc.

Saturn has several Engines version in the test bench right now, but none of these engines are yet frozen or accepted as the final product.
There are the idl 117, Idz 129, Idz 130 or type 30 engines. All have different compressor design. I.E. numbers of compressor fans stages etc etc.
Afaik there are no AL-41F engine.. it died with the Mig-1.44. However they did put some of the R&D on archive, and started from there when the Pak-Fa program started.

I'm more interesting to see if and when Salut can get their AL-31FM2 engines certified and operational. It should give various VVS jets further performance increase. Like Su-30SM, Su-30M2, Su-34 and Su-27SM.

Given that the Russian engines and fighters still are far cheaper vs Western counterparts give the shorter life and TBO less importance or should i say relevance. Remember that the Su-35S airframe has "only" 6000hour of life..
While there are the Engines Life and TBO to consider, there are also equall or more important factors on any jet fighters. Like Fuel consumption, T/W and T/D(thrust/Drag) ratio. And then the overall design and how much high lift the design create.
All of the latest Russian design has exellente aerodynamic performance, that would imply a very well ballanced design and that their design fit well with VVS requirements and tactical /strategic doctrines.
What types of jets fit best for USAF does not mean it will fit VVS equally good and vice verca.

So while many people often have a field day, pissing on Russian jet engines, they often miss the bigger picture here.

haavarla wrote:

So while many people often have a field day, pissing on Russian jet engines, they often miss the bigger picture here.

What like the SU-30MKI's motors are "very susceptible to FOD"? 1 minute take off spacing? No field level repair for the FOD?

REF: 1:05-2:25

http://www.youtube.com/watch?v=WKEa-R37PeU

Not to mention...

The Hindustan Times wrote:

Dec 16/11: The Hindustan Times reports that perennial problems with Russian spares & reliability have become an urgent issue for the SU-30MKI fleet now:

“Prime Minister Manmohan Singh is expected to red-flag [SU-30] serviceability, product support and pending upgrade… at the annual [Russian] summit meeting…. Top government sources said that Air Headquarters has urgently requested the Prime Minister to raise the issue of engine serviceability with his Russian counterpart after few incidents of engine failures…. the top brass has conveyed to government that “shaft bearing failures” have occurred in some [AL-31FP] engines. “In peacetime, the fighter can land on the other engine but this can be a life and death situation in adverse conditions, said a senior official.”

Doesn't seem like we need to piss on Russian jet engines, they just crap out on their own. Doh

TEG

Wasn't that Colonel's claims debunked by the Indian military personnel though?

Whatever Indian Air Force Pride was crushed by the video - today it is this (as seen above): "...Headquarters has urgently requested the [Indian] Prime Minister to raise the issue of engine serviceability with his Russian counterpart after few incidents of engine failures…."

Oh, alright. Thanks.

Forum: F-35 Lightning II

T-50 and F-35