F-35 Cancelled, then what ?
Armwaving, n. - Arguments with which one disagrees, while being unwilling or unable to advance factual or logical grounds for such disagreement.
Engines - could you elaborate a bit on "pushing the envelope to a high degree in terms of TW"? Because the F135 weighs 6,500-some pounds and puts out 43,000 pounds, which translates to a nonstellar 6.6:1 (the F414/EJ200 are around 10 and the GE F110-GE-132 is about 8).
I've heard it suggested (recently from a source who really ought to know) that there are stealth and thermal management features in there, and the extended jetpipe, but (to paraphrase Elvis) that's still a hunka-hunka-burning-engine.
Engines - could you elaborate a bit on "pushing the envelope to a high degree in terms of TW"? Because the F135 weighs 6,500-some pounds and puts out 43,000 pounds, which translates to a nonstellar 6.6:1 (the F414/EJ200 are around 10 and the GE F110-GE-132 is about 8).
I've heard it suggested (recently from a source who really ought to know) that there are stealth and thermal management features in there, and the extended jetpipe, but (to paraphrase Elvis) that's still a hunka-hunka-burning-engine.
An engine which goes 'Bnag' may be viewed by some as engineering Gold LOL...
Personally I would describe it as being more like engineering Brown and as I posted earlier - any fix is likely to add weight to the engine - not a huge problem for most combat aircraft but for the Turkey 'B' it could well be a wee problem !!
Not sure if that counts as 'Armwaving' but to paraphrase a famous advert - ''there could be trouble ahead'' and one way or the other you can be sure that the taxpayer will pick up the tab as usual !
rgds LR
Personally I would describe it as being more like engineering Brown and as I posted earlier - any fix is likely to add weight to the engine - not a huge problem for most combat aircraft but for the Turkey 'B' it could well be a wee problem !!
Not sure if that counts as 'Armwaving' but to paraphrase a famous advert - ''there could be trouble ahead'' and one way or the other you can be sure that the taxpayer will pick up the tab as usual !
rgds LR
First, a disclaimer - new weapons programs generate critics, regardless of the merit of the program or how well it is executed. I distinctly recall massive criticisms of the M1 Abrams tank - it was too big and expensive, it was a gas hog, it's turbine powertrain was fragile and would never survive in combat, the high tech main gun would never work, tanks were obsolete, etc. Then it went into combat and totally kicked ass - arguably the best tank ever. Turned out the only thing the critics had right was the 'gas hog' part.
So, that the F-35 program has many critics is not meaningful by itself. But, I know quite a bit more about aircraft than I do tanks, and I have friends that worked on the Boeing JSF entry - people that told me what was wrong with the Lockheed JSF entry over 10 years ago. So I can more readily judge the validity of the F-35 critics, and quite frankly many of their complaints about the F-35 ring true to my ears.
EVERY new engine program will push the start of the art - if it doesn't there really isn't much reason to spend billions on the development. Different programs push different aspects - fuel burn or TSFC, weight, thrust to weight, noise, etc. But they all push the limit. Further, military engines tend to accept more risk and push a little harder than commercial engines (it's worth noting both the GEnx and Trent 1000 engines on the 787 and 747-8 have been surprisingly reliable at EIS - something that wasn't the norm on past new commercial engines). But there is another side to that - I've spent over 35 years dealing with engines from "the big three" - Pratt, Rolls, and GE/CFM. All three have various strengths and weaknesses - to the point that if you tell me the problem, I can generally - with close to 90% confidence, say which engine company it is. Example problems:
Compressor Stability
Inclement weather
Fan flutter
.
.
.
.
.
.
.
.
And the answers:
Compressor stability - Pratt
Inclement weather - GE/CFM
Fan Flutter - Rolls
As I noted in my earlier post 5159, tell me the problem is compressor blade rub/case distortion, and my answer would immediately be Pratt - they have a long history of that - and the other two don't. It's not that the F135 was beyond their models - it's that their models for case distortion simply are not as good as the other guys.
Oh, and don't fool yourself, Pratt may pay for the fix in the short term, but long term it's always going to come back to the taxpayer in the form of higher prices for future engines and spares. It always does
So, that the F-35 program has many critics is not meaningful by itself. But, I know quite a bit more about aircraft than I do tanks, and I have friends that worked on the Boeing JSF entry - people that told me what was wrong with the Lockheed JSF entry over 10 years ago. So I can more readily judge the validity of the F-35 critics, and quite frankly many of their complaints about the F-35 ring true to my ears.
EVERY new engine program will push the start of the art - if it doesn't there really isn't much reason to spend billions on the development. Different programs push different aspects - fuel burn or TSFC, weight, thrust to weight, noise, etc. But they all push the limit. Further, military engines tend to accept more risk and push a little harder than commercial engines (it's worth noting both the GEnx and Trent 1000 engines on the 787 and 747-8 have been surprisingly reliable at EIS - something that wasn't the norm on past new commercial engines). But there is another side to that - I've spent over 35 years dealing with engines from "the big three" - Pratt, Rolls, and GE/CFM. All three have various strengths and weaknesses - to the point that if you tell me the problem, I can generally - with close to 90% confidence, say which engine company it is. Example problems:
Compressor Stability
Inclement weather
Fan flutter
.
.
.
.
.
.
.
.
And the answers:
Compressor stability - Pratt
Inclement weather - GE/CFM
Fan Flutter - Rolls
As I noted in my earlier post 5159, tell me the problem is compressor blade rub/case distortion, and my answer would immediately be Pratt - they have a long history of that - and the other two don't. It's not that the F135 was beyond their models - it's that their models for case distortion simply are not as good as the other guys.
Oh, and don't fool yourself, Pratt may pay for the fix in the short term, but long term it's always going to come back to the taxpayer in the form of higher prices for future engines and spares. It always does
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LO,
I'll do my best, but I don't have the figures to 'elaborate'. I may be able to explain what information I have used to make the statements about T/W ratio.
The UK and US ASTOVL studies in the 80s generated a number of models and data around the driving technologies and capabilities needed for supersonic ASTOVL. Those were carried forward by the US in the late 80s and early 90s, and indicated that significant improvements in core engine performance were needed, in terms of specific thrust, sfc and also overall thrust to weight ratio. As I understood it, the studies showed that more thrust was needed from less engine volume and mass to make the STOVL sums work.
The DoD was also funding a major programme called Integrated High performance Turbine Engine Technology (IHPTET) (1987 to 2005), that involved all the key US manufacturers and was aimed at developing the key technology for the next generation of engines in a number of categories. F135 (and F136) both benefitted from this programme.
By the early to mid 90s, the DoD were convinced that the next generation of engines (with IHPTET technology) would be able to deliver the improved performance required to make the JSF work. Now, how this translated into actual figures for the F135, I can't comment. I would agree with you that this engine very probably has a lot of 'stuff' attached to it to deliver signature and other targets, but that can only be speculation. It's possible that your figures are 'apples and oranges', but I honestly don't know.
Longer - sorry, my bad, I should have been clearer. An engine mishap that doesn't totally destroy the engine, and doesn't cost a life is 'engineering gold', at least in my view. One that costs a life isn't.
Tdracer - thanks for an informative post. I heard similar concerns from the DoD engine guys in the 90s over P&W's record on military jet engines, and they were VERY keen to get the F136, along with it's UK developed LP compressor design, into service. However, the die is cast, and I agree that in the long term, the customer ALWAYS pays. That's a given for military engines whatever side of the pond you're on.
Best Regards as ever to those working the detail against the clock,
Engines
I'll do my best, but I don't have the figures to 'elaborate'. I may be able to explain what information I have used to make the statements about T/W ratio.
The UK and US ASTOVL studies in the 80s generated a number of models and data around the driving technologies and capabilities needed for supersonic ASTOVL. Those were carried forward by the US in the late 80s and early 90s, and indicated that significant improvements in core engine performance were needed, in terms of specific thrust, sfc and also overall thrust to weight ratio. As I understood it, the studies showed that more thrust was needed from less engine volume and mass to make the STOVL sums work.
The DoD was also funding a major programme called Integrated High performance Turbine Engine Technology (IHPTET) (1987 to 2005), that involved all the key US manufacturers and was aimed at developing the key technology for the next generation of engines in a number of categories. F135 (and F136) both benefitted from this programme.
By the early to mid 90s, the DoD were convinced that the next generation of engines (with IHPTET technology) would be able to deliver the improved performance required to make the JSF work. Now, how this translated into actual figures for the F135, I can't comment. I would agree with you that this engine very probably has a lot of 'stuff' attached to it to deliver signature and other targets, but that can only be speculation. It's possible that your figures are 'apples and oranges', but I honestly don't know.
Longer - sorry, my bad, I should have been clearer. An engine mishap that doesn't totally destroy the engine, and doesn't cost a life is 'engineering gold', at least in my view. One that costs a life isn't.
Tdracer - thanks for an informative post. I heard similar concerns from the DoD engine guys in the 90s over P&W's record on military jet engines, and they were VERY keen to get the F136, along with it's UK developed LP compressor design, into service. However, the die is cast, and I agree that in the long term, the customer ALWAYS pays. That's a given for military engines whatever side of the pond you're on.
Best Regards as ever to those working the detail against the clock,
Engines
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Engines,
The Third Amendment is quite affable, but in a Brit taxpayer's case one might go for the Magna Carta angle first.
Actually just chimed in to say (after being pointed on this forum and actually reading through as hefty as illuminating a chunk of the "Cats and flaps" thread, and some of this one too) your insight will continue to be appreciated.
One thing I didn't semi-immediately notice, anyone have recent figures of which country/service (for those of you with pilot wear to choose from) at the moment is getting how many of which type?
Loking at this from the angle that some type of F-35 might actually be the first/desired choice for lil' Finland's next jet. Unless Gripen NG really materializes then performs like a silent bat out of hell on cross-country skis, which isn't a proven sate of affairs yet. (Next jet TBD sometime between 2016-2020, in unknown numbers. Safe to assume that F-22 is either too costly or too unavailable.)
Arm waving is, of course, a democratic right. Third Amendment and all that. Please arm wave without let or hindrance. As ever, all I'll try to do is provide information to help the discussion along.
Actually just chimed in to say (after being pointed on this forum and actually reading through as hefty as illuminating a chunk of the "Cats and flaps" thread, and some of this one too) your insight will continue to be appreciated.
One thing I didn't semi-immediately notice, anyone have recent figures of which country/service (for those of you with pilot wear to choose from) at the moment is getting how many of which type?
Loking at this from the angle that some type of F-35 might actually be the first/desired choice for lil' Finland's next jet. Unless Gripen NG really materializes then performs like a silent bat out of hell on cross-country skis, which isn't a proven sate of affairs yet. (Next jet TBD sometime between 2016-2020, in unknown numbers. Safe to assume that F-22 is either too costly or too unavailable.)
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The problem is not about technical teething issues, it's all about the
money;
GAO Draft Slams F-35 On ?Unaffordable? Costs: $8.8B Over Legacy Fighters « Breaking Defense - Defense industry news, analysis and commentary
one of the funnier quotes;
Now there's a neat accounting trick.
money;
GAO Draft Slams F-35 On ?Unaffordable? Costs: $8.8B Over Legacy Fighters « Breaking Defense - Defense industry news, analysis and commentary
WASHINGTON: The F-35′s long-term costs may “not be affordable” and appear to be substantially higher than those of the existing combat aircraft fleets that the Joint Strike Fighter will replace, the Government Acocuntability Office says in a draft report.
....
The estimated gap between the F-35 sustainment costs and those of the F/A-18, F-15, F-16 and the Harrier fleets as measured in 2010 is impressive, about $8.8 billion, an increase of 79 percent. That estimate comes from the Pentagon’s authoritative Cost Assessment and Program Evaluation (CAPE) office, the GAO draft report says. The draft says that costs for the legacy fleet were about $11 billion a year in 2010. Based on CAPE’s estimate, the F-35′s annual costs will be $19.9 billion in 2012 dollars.
....
The estimated gap between the F-35 sustainment costs and those of the F/A-18, F-15, F-16 and the Harrier fleets as measured in 2010 is impressive, about $8.8 billion, an increase of 79 percent. That estimate comes from the Pentagon’s authoritative Cost Assessment and Program Evaluation (CAPE) office, the GAO draft report says. The draft says that costs for the legacy fleet were about $11 billion a year in 2010. Based on CAPE’s estimate, the F-35′s annual costs will be $19.9 billion in 2012 dollars.
The GAO does say that the military “has begun some cost savings efforts and established sustainment affordability targets for the F-35 program, but DoD did not use the military service budgets to establish these targets,” so they “do not provide a clear benchmark…” As one example of that disconnect, the auditors say that the program “arbitrarily lowered” the estimate for F-35 fuel costs by 10 percent.
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Engines,
Many thanks for the reply, I hope you and Mrs Engines enjoyed the break.
I understand that the engineers involved are having issues, and I completely understand the terms of reference that they have been subjected to in regards to performance demands.
It just seems that there has been a serious case of over-promise and under-deliver going on here, regardless of the 'reasons'.
One would think, given the decades that we have been building jet engines for, that 'design issues' could be accounted for in a reasonable and rational way when forecasting future timelines.
Referencing past design 'teething problems' as an 'excuse' is simply saying 'we don't learn....'
It's just as well there isn't a serious shooting match looming on the horizon...
Many thanks for the reply, I hope you and Mrs Engines enjoyed the break.
I understand that the engineers involved are having issues, and I completely understand the terms of reference that they have been subjected to in regards to performance demands.
It just seems that there has been a serious case of over-promise and under-deliver going on here, regardless of the 'reasons'.
One would think, given the decades that we have been building jet engines for, that 'design issues' could be accounted for in a reasonable and rational way when forecasting future timelines.
Referencing past design 'teething problems' as an 'excuse' is simply saying 'we don't learn....'
It's just as well there isn't a serious shooting match looming on the horizon...
Originally Posted by Lockheed Martin
Marine Corps F-35B IOC shall be declared when the first operational squadron is equipped with 10-16 aircraft, and US Marines are trained, manned, and equipped to conduct CAS, Offensive and Defensive Counter Air, Air Interdiction, Assault Support Escort, and Armed Reconnaissance in concert with Marine Air Ground Task Force resources and capabilities. Based on the current F-35 JPO schedule, the F-35B will reach the IOC milestone between July 2015 (Objective) and December 2015 (Threshold). Should capability delivery experience changes or delays, this estimate will be revised appropriately.
The IHPTET T/W goal was 20:1, which is 2x better than we do today (F414/EJ200 are close) and 3x better than the F135.
I was pretty close to IHPTET at the time and it was recognized that it would, in the appropriate cycle, provide you with the dry thrust needed for non-afterburning VL (the use of A/B having been recognized as a nonstarter by then.)
The ATFE was always aimed at 10:1, but that didn't take a 2D nozzle into account, which is why the F119 is relatively heavy. If the F135 was a 10:1 engine it would weigh 4000-4300 lb (depending on whose thrust figures you believe) but it weighs 6500+ lb (says P&W). That's a lot for a length of straight jetpipe and some thermal-management kit.
I was pretty close to IHPTET at the time and it was recognized that it would, in the appropriate cycle, provide you with the dry thrust needed for non-afterburning VL (the use of A/B having been recognized as a nonstarter by then.)
The ATFE was always aimed at 10:1, but that didn't take a 2D nozzle into account, which is why the F119 is relatively heavy. If the F135 was a 10:1 engine it would weigh 4000-4300 lb (depending on whose thrust figures you believe) but it weighs 6500+ lb (says P&W). That's a lot for a length of straight jetpipe and some thermal-management kit.
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Hempy,
Thanks for the kind wishes.
The challenge for designers and engineers is that the performance envelope is always being pushed. This is true for all combat aircraft systems, especially propulsion. The F135 is an extremely advanced engine, with a number of novel features. Many of these are firmly 'US eyes only', but my (slightly informed) guess is that it is pushing the boundaries in all areas.
When you do that, you run the risk of the unexpected. This appears to have happened here. It's not at all unusual for new engine programmes, and as I've posted before, the 135 appears to have delivered well to date.
I suppose that, as an engineer, I expect problems. I don't want them to happen, but they usually do.
LO, we could trade engine performance figures for some time, the only common factor being that neither of us has access to the actual data needed for a comparison. All I will say is that if the 135 had not delivered on its thrust/weight targets, the F-35B would not have passed the major review of a few years ago. What I can say is that when I left the programme some years ago, the engine was on target for weight, and was starting a further weight reduction plan that had been applied by the DoD as a 'stretch' target.
During the F-35B weight reduction plan, the propulsion system was required to achieve further reductions, one of the major changes arising from that was re-engineering the 3BSD from steel to titanium. RR's performance on this effort was described to me as 'absolutely stellar' by some hard bitten engineers at Fort Worth. Other areas of work on the propulsion system, led by talented young Brits, generated significant improvements in VL thrust efficiency.
My bottom line - I believe that the F135 driven propulsion system for the F-35B is meeting its weight and performance targets. Others may (and probably will) differ.
Hope this lot is of some interest,
Best regards as ever to those actually crunching the numbers,
Engines
Thanks for the kind wishes.
The challenge for designers and engineers is that the performance envelope is always being pushed. This is true for all combat aircraft systems, especially propulsion. The F135 is an extremely advanced engine, with a number of novel features. Many of these are firmly 'US eyes only', but my (slightly informed) guess is that it is pushing the boundaries in all areas.
When you do that, you run the risk of the unexpected. This appears to have happened here. It's not at all unusual for new engine programmes, and as I've posted before, the 135 appears to have delivered well to date.
I suppose that, as an engineer, I expect problems. I don't want them to happen, but they usually do.
LO, we could trade engine performance figures for some time, the only common factor being that neither of us has access to the actual data needed for a comparison. All I will say is that if the 135 had not delivered on its thrust/weight targets, the F-35B would not have passed the major review of a few years ago. What I can say is that when I left the programme some years ago, the engine was on target for weight, and was starting a further weight reduction plan that had been applied by the DoD as a 'stretch' target.
During the F-35B weight reduction plan, the propulsion system was required to achieve further reductions, one of the major changes arising from that was re-engineering the 3BSD from steel to titanium. RR's performance on this effort was described to me as 'absolutely stellar' by some hard bitten engineers at Fort Worth. Other areas of work on the propulsion system, led by talented young Brits, generated significant improvements in VL thrust efficiency.
My bottom line - I believe that the F135 driven propulsion system for the F-35B is meeting its weight and performance targets. Others may (and probably will) differ.
Hope this lot is of some interest,
Best regards as ever to those actually crunching the numbers,
Engines
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M1 Abrams tank... Then it went into combat and totally kicked ass - arguably the best tank ever. Turned out the only thing the critics had right was the 'gas hog' part.
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Originally Posted by LO
The IHPTET T/W goal was 20:1, which is 2x better than we do today (F414/EJ200 are close) and 3x better than the F135.
I was pretty close to IHPTET at the time and it was recognized that it would, in the appropriate cycle, provide you with the dry thrust needed for non-afterburning VL (the use of A/B having been recognized as a nonstarter by then.)
The ATFE was always aimed at 10:1, but that didn't take a 2D nozzle into account, which is why the F119 is relatively heavy. If the F135 was a 10:1 engine it would weigh 4000-4300 lb (depending on whose thrust figures you believe) but it weighs 6500+ lb (says P&W). That's a lot for a length of straight jetpipe and some thermal-management kit.
I was pretty close to IHPTET at the time and it was recognized that it would, in the appropriate cycle, provide you with the dry thrust needed for non-afterburning VL (the use of A/B having been recognized as a nonstarter by then.)
The ATFE was always aimed at 10:1, but that didn't take a 2D nozzle into account, which is why the F119 is relatively heavy. If the F135 was a 10:1 engine it would weigh 4000-4300 lb (depending on whose thrust figures you believe) but it weighs 6500+ lb (says P&W). That's a lot for a length of straight jetpipe and some thermal-management kit.
The F135-PW-100 and F135-PW-400 don't have all that extra junk (they are comparable to traditional jet engines with some stealth radar/ir features added and in your words are the jet engine core with a "length of straight jetpipe and some thermal management kit"). The weight for the F135-PW-100 is around 3,750 lbs. This would put the thrust to weight ratio of the actual F135 engine at around 11.467.
If you are comparing a F135-PW-600 to a legacy engine it is an apples to oranges comparison because legacy engines don't have all the STOVL equipment.
Engines - I'm not arguing that the engine weight isn't on target; I'm saying that compared to other fighter engines, the CTOL/CV engine's T/W is low. I don't pretend to know why this is so.
J58spike - Your post is not accurate, I'm afraid. These weights have been confirmed by P&W. Many other figures float around on the Internet but they are fantasy.
J58spike - Your post is not accurate, I'm afraid. These weights have been confirmed by P&W. Many other figures float around on the Internet but they are fantasy.
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The picture you posted is referencing requirements, not the weight of the actual engine. That is why is states "not to exceed weight." (And those are older requirements btw, as the program has evolved they have rebalanced mass reqs. between different sub-systems).
Do you have a primary source that actually states what the weight is?
Do you have a primary source that actually states what the weight is?
The weights were confirmed to me, via email, by a P&W official, in 12/10. Those more recent figures are 6444 lb for CTOL and 10342 lb for STOVL.
Now, please cite your own evidence for your figures, including historical cases where an engine was delivered at less than 60 per cent of its contracted NTE weight.
Now, please cite your own evidence for your figures, including historical cases where an engine was delivered at less than 60 per cent of its contracted NTE weight.
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Even with 'weight reduction programs' those figures are close enough to be at least ballpark.
3.5 tons of metal pushing out 17 tons of thrust on an MTOW 26 ton aircraft that just happens to have a wing area roughly half of other Gen 4 or 5 fighters.
This all reminds me of stories I read about the German Propaganda machine keeping civilian hopes alive during the dark days of 1944 with promises of magical 'Wünderwaffen' that were going to save them all.
I hope all the promises come true. I will truly admire the machine if they do.
3.5 tons of metal pushing out 17 tons of thrust on an MTOW 26 ton aircraft that just happens to have a wing area roughly half of other Gen 4 or 5 fighters.
This all reminds me of stories I read about the German Propaganda machine keeping civilian hopes alive during the dark days of 1944 with promises of magical 'Wünderwaffen' that were going to save them all.
I hope all the promises come true. I will truly admire the machine if they do.
F-35C Carrier Trials
On 20 Sep 14 I was able to get on the USS Nimitz during Fleet Week in San Diego. One of the sailors I spoke to said he was looking forward to the next task which was trials with an aircraft that had never been on a carrier before. Unless there is some new "black" aircraft, I assume that this will be the F-35C as per this earlier report:
Navy's F-35C Completes Landing Tests Ahead of October Sea Trials - USNI News
If correct, this would mean no slippage to the plan since Jan 2014.
Navy's F-35C Completes Landing Tests Ahead of October Sea Trials - USNI News
If correct, this would mean no slippage to the plan since Jan 2014.
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Re:F-35C Carrier Trials
I would rather doubt that, not much is flying and what is flying is limited because of the unresolved engine problem. Six more days left in September and without a release by the safety folks by September 30, everything starts slipping according to General Bogdan.
BTW, I wonder if there has been a solution to transporting spare engines to the carrier as they are too big and heavy for what was to be conventional transport.
If correct, this would mean no slippage to the plan since Jan 2014.
BTW, I wonder if there has been a solution to transporting spare engines to the carrier as they are too big and heavy for what was to be conventional transport.
Last edited by Turbine D; 24th Sep 2014 at 14:59. Reason: Grammer correction