Lockheed Martin F-35 Lightning II Joint Strike Fighter (JSF)

FighterJock said:
Interesting. I would not like to be the test pilot who flies the Franken-bird for the first time especially if anything goes wrong with the airframe during the test flight.
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Won't be too bad, the forward fuselage only fits one way.

I know of a Cessna that needed a new tail put on it, the mechanics managed to get it one rivet hole off square.
 
so why does the Pentagon want to move on from the engines?
unfortunately the news link is paywalled
 
helmutkohl said:
so why does the Pentagon want to move on from the engines?
unfortunately the news link is paywalled
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So that they can focus on what they have that already works and can invest funds appropriately on more rather than waste them on programs that won’t deliver any new capabilities. If the US Govt truly wanted to enhance the F-35 propulsion system they would be better served by investing that money in spare parts for the F135 rather than diluting capability by continuing the GE program.
 
Yeah, doubles the logistics chain for engines and the gains were marginal over the Engine Core Upgrade, ironically enough because Congress was slow in passing a defence bill work on that program had been slowed as it had been unfunded for two and a half months.

The AETP engine isn't just incompatible with the F-35B, its incompatible with the F-35C as well. Meanwhile the Engine Core Upgrade benefitted both the A and C and offered more cooling but not more power to the B's.
 
WatcherZero said:
Yeah, doubles the logistics chain for engines and the gains were marginal over the Engine Core Upgrade, ironically enough because Congress was slow in passing a defence bill work on that program had been slowed as it had been unfunded for two and a half months.

The AETP engine isn't just incompatible with the F-35B, its incompatible with the F-35C as well. Meanwhile the Engine Core Upgrade benefitted both the A and C and offered more cooling but not more power to the B's.
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F-135 ECU will increase thrust and range by 7% and 50% improvement in cooling
XA100 AETP will increase thrust by 20% and range by 30% and 100% improvement in cooling
 
GTX said:
So that they can focus on what they have that already works and can invest funds appropriately on more rather than waste them on programs that won’t deliver any new capabilities. If the US Govt truly wanted to enhance the F-35 propulsion system they would be better served by investing that money in spare parts for the F135 rather than diluting capability by continuing the GE program.
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X100 AETP not only offer a lot more thrust and range compared to F-135ECU, it also help with skin cooling, I wouldn't say it offer no additional capabilities. There is a good reason why they want it on 6th gen
 
Ronny said:
F-135 ECU will increase thrust and range by 7% and 50% improvement in cooling
XA100 AETP will increase thrust by 20% and range by 30% and 100% improvement in cooling
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Indeed but the PTMS which is a revamp of the APU and an entirely separate project to the ECU also improves cooling by 50% and provides all required ground power for start-up or maintenance diagnostic checks without the need to start the main engine until actual takeoff. So combined they match the cooling performance of a replacement engine while the improvements reduce electrical generation demand on the engine increasing range (through lower electrical conversion requirement) even without a direct improvement to burn efficiency.

(PTMS is also about 1,000 pounds lighter and physically smaller)
 
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Ronny said:
X100 AETP not only offer a lot more thrust and range compared to F-135ECU, it also help with skin cooling, I wouldn't say it offer no additional capabilities. There is a good reason why they want it on 6th gen
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Capability is measured in more than thrust and engine performance. It includes the ability to sustain and support which is arguably more importan. In the case of the F135 one already has 5 - 6 depots globally. introducing a new engine as a replacement would necessitate replacing those and all the investments made (not only in facilities but tooling, training, spares etc). Once you factor that it the picture looks different.
 
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GTX said:
Capability is measured in more than thrust and engine performance. It includes the ability to sustain and support which is arguably more importan. In the case of the F135 one already has 5 - 6 depots globally. introducing a new engine as a replacement would necessitate replacing those and all the investments made (not only in facilities but tooling, training, spares etc). Once you factor that it the picture looks different.
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To be honest, I find that more in the logistic side rather than capability side.
While the ability to sustain and support of the supply chain is important , there are also disadvantage in having shorter ranged , slower aircraft. There are also certain advantage in having 2 supplier for your engines as they will compete against each other for better product
 
WatcherZero said:
Indeed but the PTMS which is a revamp of the APU and an entirely separate project to the ECU also improves cooling by 50% and provides all required ground power for start-up or maintenance diagnostic checks without the need to start the main engine until actual takeoff. So combined they match the cooling performance of a replacement engine while the improvements reduce electrical generation demand on the engine increasing range (through lower electrical conversion requirement) even without a direct improvement to burn efficiency.

(PTMS is also about 1,000 pounds lighter and physically smaller)
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To be fair, I think PTMS could be adapted for XA100 as well.
Beside, one advantage of 3 stream engine could be lower skin temperature , which is significant advantage for stealth aircraft
 
WatcherZero said:
Indeed but the PTMS which is a revamp of the APU and an entirely separate project to the ECU also improves cooling by 50% and provides all required ground power for start-up or maintenance diagnostic checks without the need to start the main engine until actual takeoff. So combined they match the cooling performance of a replacement engine while the improvements reduce electrical generation demand on the engine increasing range (through lower electrical conversion requirement) even without a direct improvement to burn efficiency.

(PTMS is also about 1,000 pounds lighter and physically smaller)
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i assume you are referring to the Colins Aerospace proposed upgrade (see below article for example) given the PTMS has been part of the F-35 from the start.

https://www.defensedaily.com/collin...ore-than-twice-the-current-cooling/air-force/
 
Ronny said:
To be honest, I find that more in the logistic side rather than capability side.
While the ability to sustain and support of the supply chain is important ,
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the ability to sustain a platform is most definitely part of overall capability. It doesn’t matter if your engine gives you warp speed if it can’t get in the air because of lack of serviceability. Or to put it another way, an Air Force with Fokker Eindeckers will defeat one with F-22s if the former can get in the air while the latter is grounded due to lack of sustainment support.

Ronny said:
there are also disadvantage in having shorter ranged , slower aircraft.
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its not as if the F-35 really suffers on that front. Just check the reports from pilots and exercises. The Air Forces operating are satisfied with its capabilities. One also shouldn’t get so tied up in kinematic performance when you factor in the F-35s overall sensor ( on board and off board), data fusion and LO capabilities and the ability it has to see and not be seen…
Ronny said:
There are also certain advantage in having 2 supplier for your engines as they will compete against each other for better product
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Not if one type doesn’t fit in the platforms…
 
GTX said:
Capability is measured in more than thrust and engine performance. It includes the ability to sustain and support which is arguably more importan. In the case of the F135 one already has 5 - 6 depots globally. introducing a new engine as a replacement would necessitate replacing those and all the investments made (not only in facilities but tooling, training, spares etc). Once you factor that it the picture looks different.
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Once you scale into the hundreds or thousands of units there can be a crossover of logistic simplicity versus logistic capability. It may be more advantageous to have two supply chains despite the complexity it introduces.

Airlines often find this with large fleets, splitting engine or airframe suppliers can be more economical than enforced standardisation.
 
Kiltonge said:
Once you scale into the hundreds or thousands of units there can be a crossover of logistic simplicity versus logistic capability. It may be more advantageous to have two supply chains despite the complexity it introduces.
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JPO seems to disagree:

https://www.airandspaceforces.com/f-35-program-pratt-sole-source-engine-upgrade/
Quote from Lt. Gen. Michael Schmidt, JPO director:

Adding a second source would incur “significant duplication of cost and unacceptable performance risks and schedule delays,”
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Competition in the source of military fighter engines is often a false economy. These are not off the shelf commodities. The government pays for the development and owns most of the intellectual property. If you have competitive engines, you pay for two development programs, two production and supply lines, and two logistics & maintenance programs.

Once the engines are developed, virtually the only competition is production price and support. And you have to pay to keep both engines’ production capability in place, otherwise the loser closes up shop and you are back to a single supplier going forward, exactly the same place you were before competing the two engines with double the cost.

In the Great Engine War between the F100 and F110, GE won a 75% share the first year, but then it remained roughly 50-50 the rest of the program. It kept both P&W and GE in the game, and may have saved some acquisition costs, but is doubtful that it saved overall program costs. This is why the competition is usually decided after a technology demonstration and proposal stage, and not after EMD.
 
Kiltonge said:
Once you scale into the hundreds or thousands of units there can be a crossover of logistic simplicity versus logistic capability. It may be more advantageous to have two supply chains despite the complexity it introduces.

Airlines often find this with large fleets, splitting engine or airframe suppliers can be more economical than enforced standardisation.
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Honest question, how often have fighters had multiple production engines?
 
Josh_TN said:
Honest question, how often have fighters had multiple production engines?
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I can only think of 2: F-15E+, and F-16 Block 30+ can take either F100-220/220E/229 or F110-100/129. There have been others where the production engine changed: F-86 got an Orenda engine for later Canadian (maybe Australian also), F-4K got RR Spey. There may be others, but very few have had interchangeable alternative engines.
 
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F119Doctor said:
I can only thing of 2: F-15E+, and F-16 Block 30+ can take either F100-220/220E/229 or F110-100/129. There have been others where the production engine changed: F-86 got an Orenda engine for later Canadian (maybe Australian also), F-4K got RR Spey. There may be others, but very few have had interchangeable alternative engines.
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I kinda assumed it was a short list…the issues of training, parts, and logistics for different engine types on a global scale is problematic. A civilian company can restrict those to specific markets and regions; a military arm cannot afford to rotate an aircraft to region in a surge and have no one able to maintain it, nor can it afford two sets of training or two sets of maintainers. For the U.S., the same aircraft that might find itself in the Mideast or Europe might also be surged to the Pacific at the drop of a hat.
 
GTX said:
the ability to sustain a platform is most definitely part of overall capability. It doesn’t matter if your engine gives you warp speed if it can’t get in the air because of lack of serviceability. Or to put it another way, an Air Force with Fokker Eindeckers will defeat one with F-22s if the former can get in the air while the latter is grounded due to lack of sustainment support.
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The ability to sustain a platform is on logistic side, it is rarely every count as platform capability but rather like the industrial capability of the manufacturer. Beside, when making new fighters, new missiles, new tanks, the new one always have fewer factories, depot..etc. Yet it doesn't stopping us from making new weapons like NGAD, LRASM, HACM..etc.
Beside, they gonna make the 3 stream engines for NGAD anyway, so they will eventually have to make factories, deport for 3 stream engines, may as well doing it now rather than later

GTX said:
its not as if the F-35 really suffers on that front. Just check the reports from pilots and exercises. The Air Forces operating are satisfied with its capabilities. One also shouldn’t get so tied up in kinematic performance when you factor in the F-35s overall sensor ( on board and off board), data fusion and LO capabilities and the ability it has to see and not be seen…
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To be honest though, reading the report, most pilot agreed F-35 close in agility is worse than F-16 and F-22,
For kinematic that valuable for BVR such as super cruising speed, acceleration, altitude then F-35 is worse than Rafale, Eurofighter. Sure F-35 does have advantage in VLO and radar detection range compared to these 4.5 gen fighters. But we have to consider that in future, F-35 will have to face off against things like J-20, Su-57, J-35..etc where F-35 might no longer have the overall sensor advantage. Then the kinematic is important again.
Additional range is important to loiter times and reach for carrier air wing too

GTX said:
Not if one type doesn’t fit in the platforms…
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Apparently, XA100 currently fit inside F-35A and F-35C
GE’s engine is uniquely designed to fit in the F-35A, as well as the F-35C without modifications to the tailhook. The XA100’s improved fuel efficiency provides a significant reduction in carbon emissions and will operate on any U.S. Air Force-approved Sustainable Aviation Fuel.
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https://www.aero-mag.com/ge-xa100-adaptive-cycle-engine-13092022
 
F119Doctor said:
I can only thing of 2: F-15E+, and F-16 Block 30+ can take either F100-220/220E/229 or F110-100/129. There have been others where the production engine changed: F-86 got an Orenda engine for later Canadian (maybe Australian also), F-4K got RR Spey. There may be others, but very few have had interchangeable alternative engines.
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A few thoughts - as distinct from licensed production and additional engineering (Rolls & Pratt with the J48; Armstrong Siddeley and Wright with the J65), second source manufacturing for jet engines was relatively common during the 1950s - some examples in the US being:
GE J35 – Allison and Chevrolet
GE J47 - Packard and Studebaker
P&W J57 – Ford
Wright J65 - Buick
(which makes sense with the B-47 needing six engines and the B-52 needing eight.)

I believe that parts were interchangeable between manufacturers for the particular engine variant, but would have to dive into the specific IPB catalogues to verify - I'll leave that as an exercise for the reader.

Aircraft production numbers declined in the sixties and seventies which allowed OEM production only. The last attempt to second-source an engine was when the Navy split the buy of F404s between GE and Pratt with the F-18 being the intended application (this was in addition to the anticipated production of the A-6F with dry F404s). A production contract for 102 engines worth $174m was awarded to Pratt in FY88. This was another watermark of the Lehman era as SecNav.

I think that the intent was that the Pratt engines be Form/Fit/Function drop-in replacements for the GE-built engines. In the event, this was not to be; for whatever reason (and there was a lot of blamestorming) Pratt parts were not interchangeable with GE parts, nor did the engines perform exactly the same (differing stall margins, etc). In addition, costs were higher and the Pratt program ran late as they struggled to replicate GE processes based on the Navy reprocurement data packages. Eventually, the A-6F was cancelled which relieved the production pressure on GE; the lowered production rates then rendered the second source completely uneconomical (along with Pratt's production difficulties).
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I should note that I am using the term "second source" to mean an engine that is license built by another manufacturer than the OEM and is interchangeable in the target aircraft. The use of a different engine for the same application, I would call an "alternate engine" such as the F135/F136. This is quite common in the airliner field, particularly with Boeing in the 70s and 80s. IIRC, the 747-400 and the 767 were certificated with the choice of three different manufacturers engines.
 
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F119Doctor said:
Competition in the source of military fighter engines is often a false economy. These are not off the shelf commodities. The government pays for the development and owns most of the intellectual property. If you have competitive engines, you pay for two development programs, two production and supply lines, and two logistics & maintenance programs.

Once the engines are developed, virtually the only competition is production price and support. And you have to pay to keep both engines’ production capability in place, otherwise the loser closes up shop and you are back to a single supplier going forward, exactly the same place you were before competing the two engines with double the cost.

In the Great Engine War between the F100 and F110, GE won a 75% share the first year, but then it remained roughly 50-50 the rest of the program. It kept both P&W and GE in the game, and may have saved some acquisition costs, but is doubtful that it saved overall program costs. This is why the competition is usually decided after a technology demonstration and proposal stage, and not after EMD.
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The idea of multiple engine types has usually been used as a hammer to beat on programs people want to kill (because it IS more expensive to fund two different types of engines). The Gripen doesn't even do that and there are multiple engines it could have used, off the shelf, just in Europe alone (EJ200, M88). And they didn't. By FAR the more common situation is one type of engine per aircraft (Typhoon, Rafale, Flankers across the world, etc.). Hell, you frequently have one type of engine powering multiple aircraft. How many aircraft used the J79? J57? F414? F404? With few exceptions it's difficult to take those demanding multiple types of engines for one aircraft seriously. The F-14 would be one of those exceptions because the TF30 was only ever intended as an interim engine.
 
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aim9xray said:
I should note that I am using the term "second source" to mean an engine that is license built by another manufacturer than the OEM and is interchangeable in the target aircraft. The use of a different engine for the same application, I would call an "alternate engine" such as the F135/F136. This is quite common in the airliner field, particularly with Boeing in the 70s and 80s. IIRC, the 747-400 and the 767 were certificated with the choice of three different manufacturers engines.
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In this case the engines already existed or were company funded. For example, American Airlines didn't demand Boeing fund the development of three different engines for its 747. Commercial and military are very different in the way things are funded. And Rolls can't fund the development of its own engine and then demand customers use it. The F100/F110 worked because the F100 was having problems (thus the incentive to look for a second engine) and the F101 already existed to be made into the F110. If the F101 hadn't existed there would have been no F110. They'd have muddled through until the F100 was good to go. Like the Tomcat and F-111 did with the TF30.
 
aim9xray said:
A few thoughts - as distinct from licensed production and additional engineering (Rolls & Pratt with the J48; Armstrong Siddeley and Wright with the J65), second source manufacturing for jet engines was relatively common during the 1950s - some examples in the US being:
GE J35 – Allison and Chevrolet
GE J47 - Packard and Studebaker
P&W J57 – Ford
Wright J65 - Buick
(which makes sense with the B-47 needing six engines and the B-52 needing eight.)

I believe that parts were interchangeable between manufacturers for the particular engine variant, but would have to dive into the specific IPB catalogues to verify - I'll leave that as an exercise for the reader.
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The J65 is not a good example... the Buick engines had regular and sustained problems... in most applications (B-57, F-84F, FJ-3 Fury) the Buick engines often leaked oil onto the engine casing, the heat then burning the oil and gumming up the inside of the engine bays.

In the B-57 especially, the smoke would circulate into the cockpit air system and fill the cockpit with smoke.

In the FJ-3 Fury the oil supply would sometimes "dump" during the catapult launch, with the engine starting to run rough and then seize - sometimes the aircraft could circle back around for an emergency recovery and sometimes not.

Fortunately for the A-4s and F11F Tigers, they never got any Buick-built ones (most of those went to the USAF except for a small number in the FJ-3s), and so had significantly fewer engine issues.

Before the FJ-4s and F11F entered production Buick was ordered to drop their J65 line, and Wright resumed making all of the J65s needed by both the USAF and USN/USMC.
 
True with the J65 - overall, not rally a great success in the US - of course it had the reputation of being the only jet engine "built around an oil leak"! This was reportedly due to the oil system not having a recovery sump - the oil being vented overboard after use. True? I don't know - but it does explain the stains down the sides of the early A4Ds.
 
NMaude said:
I suppose that once that idiot Erdogan sees the light and gets rid of Turkey's SA-21 Growler batteries Turkey will get its F-35s?
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Its not simple as that. Granted the S-400 gave the Americans the perfect excuse but it was a breaking point rather than a reason.

There are/were a lot of other issues between Turkey and the USA. US-YPG partnership in Syria, non-extradition of the Fetullah Gulen, Brunson crisis, etc... The S-400 gave the US the perfect excuse to take a drastic action against Turkey.

They didn't just stop the delivery of Turkish F-35s, they kicked Turkey out of the whole program. They're now replacing Turkish industrial participation with Germany.

Nowadays both countries are only allies on paper. US even shot down a Turkish drone only a month ago...
 
NMaude said:
I suppose that once that idiot Erdogan sees the light and gets rid of Turkey's SA-21 Growler batteries Turkey will get its F-35s?
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I don’t think the S-400s are ever going away. He would have to admit he made a mistake for that to happen. That is hard for any politician to do, let alone “just the” Tayyip.

ETA: in fact at one point the Greeks were trying to buy the F-35s slated for Turkey, but someone decided that might start a war.
 
F-35 is probably the poster child for bad program management, but never the less a thousand have been made and over a dozen countries have signed contracts. I suspect that is more than S400 exports.

But the products themselves don’t particularly matter in this case or indeed most cases: when it comes to major defense purchases, it is largely about politics.
 
Gripen is more expensive on a per airframe basis than F-35.

I doubt Non-LO aircraft are even currently viable as anything other than stand-off missile carriers at this point (and given that aircraft now entering service will be in service for several decades, non-LO aircraft will be even less viable in the future), would much rather use an LO aircraft which can use cheap easily stockpiled PGMs like JDAM in the face of modern air defences, rather than building up large stocks of cruise missiles.
 
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