F-35 Cancelled, then what ?
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I'm a bit out of touch due to location at the moment and for a while, so I haven't been on top of the news lately. Has there been any news about the engine issue? I think we were expecting something a while ago, but it's all gone a bit quiet out here.
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Originally Posted by Willard Whyte
By the time Dave reaches IOC over here there'll probably be -D, -E and -Fs on the production line.
-RP
engine updates ?
Mach 2 asked -
This from 8 April – does not seem to have been mentioned here yet ...
P&W to re-evaluate interim fix for F135 engine problem - 4/8/2015 - Flight Global
And a reminder from JFZ90's post 5951 - 30 April -
P&W fights US government criticisms of F-35 engine reliability - 4/30/2015 - Flight Global
Has there been any news about the engine issue?
P&W to re-evaluate interim fix for F135 engine problem - 4/8/2015 - Flight Global
And a reminder from JFZ90's post 5951 - 30 April -
P&W fights US government criticisms of F-35 engine reliability - 4/30/2015 - Flight Global
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My Lord, thanks for the quick answer there, just before I disappear from civilisation again for a while.
So it looks like both P&W and LM are fighting a PR campaign, or at least in (public) denial that anything much is wrong. If the pre-trenching "temporary" fix makes the engine less efficient it's hard to see how that would not affect aircraft performance (again). It would be good to see the flight envelope return to normal, whatever that may be these days.
Again, I know I may be a bit behind the times on these matters (I don't have time to get back up to speed today), but I do find the mean time between failure figures shocking. The article at your link doesn't specify what those failures are, but those do not look like good numbers for sustained operations, especially as my interest is really in the Dave B.
I wonder how many more downgrades we will see before we start taking delivery of the "operational" jets. A bloke could start to lose a bit of faith in this. I hope I'm wrong.
So it looks like both P&W and LM are fighting a PR campaign, or at least in (public) denial that anything much is wrong. If the pre-trenching "temporary" fix makes the engine less efficient it's hard to see how that would not affect aircraft performance (again). It would be good to see the flight envelope return to normal, whatever that may be these days.
Again, I know I may be a bit behind the times on these matters (I don't have time to get back up to speed today), but I do find the mean time between failure figures shocking. The article at your link doesn't specify what those failures are, but those do not look like good numbers for sustained operations, especially as my interest is really in the Dave B.
I wonder how many more downgrades we will see before we start taking delivery of the "operational" jets. A bloke could start to lose a bit of faith in this. I hope I'm wrong.
The reliability numbers are a bit alarming.
However, it's surely an anomaly, since the F135 was mature six years ago...
The F135 is established and mature, with production engines set for delivery later this year after more than 12,000 hours of testing. It is also based on the proven and highly successful F119 engine powering the F-22 aircraft, meaning testing and operational performance on that fielded engine has pushed the F135 engine even further along its path to maturity.
http://tinyurl.com/135mature
Or at least, that's what the people in the know, doing the real work, said. And of course they must have been right.
However, it's surely an anomaly, since the F135 was mature six years ago...
The F135 is established and mature, with production engines set for delivery later this year after more than 12,000 hours of testing. It is also based on the proven and highly successful F119 engine powering the F-22 aircraft, meaning testing and operational performance on that fielded engine has pushed the F135 engine even further along its path to maturity.
http://tinyurl.com/135mature
Or at least, that's what the people in the know, doing the real work, said. And of course they must have been right.
MTBF = 25/45/25. I see your point MT. But don't lose faith because
So it will be OK. A bit like a car dealer telling you, "It's a bit shabby now, but once you buy it, it will suddenly be fine."
I do have a question for anyone in the know. What is the difference in the final result between letting the blades do the trenching and pre-trenching? Why should that alter the performance of the engine once the process is complete?
Let me be clear, in case I get the all-too-common response from the back of a tall equine, I am not asking about the reasons for pre-trenching, nor am I questioning the need for it. I am wondering if allowing the engine to do it itself results in a better, more accurate fit or to understand if there are other issues.
Moreover, P&W’s ground-based testing of the production configuration shows that version should meet current reliability targets once it enters flight operations later this year, Croswell says.
I do have a question for anyone in the know. What is the difference in the final result between letting the blades do the trenching and pre-trenching? Why should that alter the performance of the engine once the process is complete?
Let me be clear, in case I get the all-too-common response from the back of a tall equine, I am not asking about the reasons for pre-trenching, nor am I questioning the need for it. I am wondering if allowing the engine to do it itself results in a better, more accurate fit or to understand if there are other issues.
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CM,
The idea of letting the engine blades accomplish the trenching provides the best possible seal preventing efficiency loss. The only down side I can think of resulting from this method maybe associated with smaller engines in flame out situations where core lock can occur, i.e., the engine casing cools too rapidly around the core. This was a problem on the CF-34 engines until the clearances were reset.
The idea of letting the engine blades accomplish the trenching provides the best possible seal preventing efficiency loss. The only down side I can think of resulting from this method maybe associated with smaller engines in flame out situations where core lock can occur, i.e., the engine casing cools too rapidly around the core. This was a problem on the CF-34 engines until the clearances were reset.
The intention is that letting the knife-edges make their own trench in the seal material gives you the closest possible fit. Eventually seals and other things start to wear and more air will leak forward through the engine, reducing efficiency.
Making a larger trench theoretically means lower efficiency, but that's only in one stage. The overall effect might be very small. It might be zero insofar as the performance after x hours or cycles is the same as it would have been without the mod.
The longer-term concern is whether the root cause (the fact that flexing of the engine wasn't accurately modeled or found in flight-sciences testing) will bite us later.
Making a larger trench theoretically means lower efficiency, but that's only in one stage. The overall effect might be very small. It might be zero insofar as the performance after x hours or cycles is the same as it would have been without the mod.
The longer-term concern is whether the root cause (the fact that flexing of the engine wasn't accurately modeled or found in flight-sciences testing) will bite us later.
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LO,
It's what happens when bragging about the new product (drinking one's own bathwater) before the product is completely wrung out, i.e., flight tested throughout the flight envelope. There are differences between the F119 engine and the F135 engine and therein lies the problem. The F119 has only a one stage LPT while the F135 has a two stage LPT, weight balance change, an added 17 inches in length plus higher temperatures to achieve higher thrust to weight capability. As the old saying goes, "Don't count your chickens before the eggs hatch".
IMHO, this is the real problem. Also, as I recall, the seal in question isn't a seal between the tip of the blades and the outer engine casing, but one to the inner compartment surrounding the LP shaft.
The F135 is established and mature, with production engines set for delivery later this year after more than 12,000 hours of testing.
The longer-term concern is whether the root cause (the fact that flexing of the engine wasn't accurately modeled or found in flight-sciences testing) will bite us later.
Right, TD - it was an inner-end seal.
The ultimate "fix" may emerge several years down the road, probably labeled as an "enhanced enduring engine" or similar marketing flannel, and with a healthy price tag attached.
The ultimate "fix" may emerge several years down the road, probably labeled as an "enhanced enduring engine" or similar marketing flannel, and with a healthy price tag attached.
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LO, Others,
Perhaps I can help a little here.
The CALF study involved not only DARPA but at the USN. While it looked at Harrier replacements, and by inference RN requirements, the UK wasn't formally involved.
The UK MoD was certainly sighted on JAST, but again in no more than an unofficial 'sighting' role. The first UK person to formally join the project in Washington was an RN Cdr AEO in around 1993/4. Further personnel joined later in the 90s. UK input to JSF requirements started around 1997 or so, with a UK RN pilot joining the JPO. As far as I know, the UK MoD didn't formally 'join' the JSF programme (i.e. commit money) until 2001, when it signed the STOVL MoD for the development phase. BAES had been part of the early stages of JSF, teamed with NG as one of the three designs competing for the 'X-plane' phase. When they lost out, they joined up with LM. The UK MoD signed up to the post-SDD MoU in 2007.
As I posted earlier on, the US were extremely keen to get BAES in the programme for their unique knowledge and experience of STOVL propulsion integration and flight control.
The main thing I'd like to see recognised one day is the great work done by knowledgable and committed service engineers and aircrew (and BAES engineers) who kept the US/UK lines open through the late 80s and early to mid 90s. their unsung work is the reason the UK was able to get its special 'Tier 1' partner status on JSF. Some of them should have got gongs. Most of them didn't.
On variant choices, I was fairly familiar with the fuel tank layouts, and I can state with some confidence that the main reason the F-35C has more fuel than the A is the bigger wing, with a bigger wing fuel tank. The only reason the C has this sized wing is purely to get on board the CVN at a fully controllable 138 knots or so. Yes, not having an internal gun also helps.
The internal gun did impact tank capacity on the A model, but hot half as much as the boom refuelling receptacle, which occupies a large portion of the main centre fuel tank on top of the wing. That receptacle also adds a lot of weight, as a lot of it is plated in steel to withstand boom strikes. I seem to remember that there was a study done into getting the USAF to adopt a probe refuelling solution (might have been by RAND as well as the GAO), but the USAF weren't willing to change from the boom system. Good reasons were offered, but it aded a good whack of costs to the design.
Interestingly, the original 27mm Mauser cannon installation would have had less impact on the internal volume and external drag. Sadly, US politics won out (as well as an understandable desire to reduce the technical risk associated with a 27mm linkless feed) and the 25mm Gatling was substituted. Heavier, and larger internal volume. Shame.
I am quite certain that somewhere in LM and the DoD, there are schemes for a 'big wing' A model, that would have a C model wing. I'd expect such an aircraft to have a very useful range indeed.
Hope this stuff is of some passing interest. Best Regards as ever to all those who play their parts along the way,
Engines
Perhaps I can help a little here.
The CALF study involved not only DARPA but at the USN. While it looked at Harrier replacements, and by inference RN requirements, the UK wasn't formally involved.
The UK MoD was certainly sighted on JAST, but again in no more than an unofficial 'sighting' role. The first UK person to formally join the project in Washington was an RN Cdr AEO in around 1993/4. Further personnel joined later in the 90s. UK input to JSF requirements started around 1997 or so, with a UK RN pilot joining the JPO. As far as I know, the UK MoD didn't formally 'join' the JSF programme (i.e. commit money) until 2001, when it signed the STOVL MoD for the development phase. BAES had been part of the early stages of JSF, teamed with NG as one of the three designs competing for the 'X-plane' phase. When they lost out, they joined up with LM. The UK MoD signed up to the post-SDD MoU in 2007.
As I posted earlier on, the US were extremely keen to get BAES in the programme for their unique knowledge and experience of STOVL propulsion integration and flight control.
The main thing I'd like to see recognised one day is the great work done by knowledgable and committed service engineers and aircrew (and BAES engineers) who kept the US/UK lines open through the late 80s and early to mid 90s. their unsung work is the reason the UK was able to get its special 'Tier 1' partner status on JSF. Some of them should have got gongs. Most of them didn't.
On variant choices, I was fairly familiar with the fuel tank layouts, and I can state with some confidence that the main reason the F-35C has more fuel than the A is the bigger wing, with a bigger wing fuel tank. The only reason the C has this sized wing is purely to get on board the CVN at a fully controllable 138 knots or so. Yes, not having an internal gun also helps.
The internal gun did impact tank capacity on the A model, but hot half as much as the boom refuelling receptacle, which occupies a large portion of the main centre fuel tank on top of the wing. That receptacle also adds a lot of weight, as a lot of it is plated in steel to withstand boom strikes. I seem to remember that there was a study done into getting the USAF to adopt a probe refuelling solution (might have been by RAND as well as the GAO), but the USAF weren't willing to change from the boom system. Good reasons were offered, but it aded a good whack of costs to the design.
Interestingly, the original 27mm Mauser cannon installation would have had less impact on the internal volume and external drag. Sadly, US politics won out (as well as an understandable desire to reduce the technical risk associated with a 27mm linkless feed) and the 25mm Gatling was substituted. Heavier, and larger internal volume. Shame.
I am quite certain that somewhere in LM and the DoD, there are schemes for a 'big wing' A model, that would have a C model wing. I'd expect such an aircraft to have a very useful range indeed.
Hope this stuff is of some passing interest. Best Regards as ever to all those who play their parts along the way,
Engines
Thank you, guys for that. As I imagined, but with some excellent detail as well. I'm sure there will be more to come if the modelling is flawed; let's hope we don't have more set-backs or worse.
Good answers.
Good answers.
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SRVL and Bring Back Weight
As I understand it there has been not a lot of if any trials of SRVL, rolling landing on the QEC class carriers, this is necessary to enable a loaded F35B to return to the ship with weapons aboard.
Let us hope that the stresses of ski jump take off and rolling landing do not necessitate the F35D, an F35B with the heavier undercarriage of the F35C....
Let us hope that the stresses of ski jump take off and rolling landing do not necessitate the F35D, an F35B with the heavier undercarriage of the F35C....
Engines,
Thank you for your insight - informative as ever.
There was bit more involvement than you list there. We did quite a bit of evaluation work in the early days on behalf of the US, but that was more operational effectiveness than engineering. The first time round was very generic, concept stuff and we didn't get into differences between models until later.
As for the gun, even with the weight penalty, I wouldn't argue with the choice of the Gatling. For air-to-air the rate of fire makes it very effective and gives the pilot plenty of chances to hit the target in a vital organ. The chosen calibre offers greater punch for other uses too, if one wants to put an expensive aircraft in an environment where its stealth won't protect it from small arms fire.
Although I don't know about their entitlement to "gongs", I second your proposal. Recognition is well deserved and long overdue.
Best,
Courtney
Thank you for your insight - informative as ever.
There was bit more involvement than you list there. We did quite a bit of evaluation work in the early days on behalf of the US, but that was more operational effectiveness than engineering. The first time round was very generic, concept stuff and we didn't get into differences between models until later.
As for the gun, even with the weight penalty, I wouldn't argue with the choice of the Gatling. For air-to-air the rate of fire makes it very effective and gives the pilot plenty of chances to hit the target in a vital organ. The chosen calibre offers greater punch for other uses too, if one wants to put an expensive aircraft in an environment where its stealth won't protect it from small arms fire.
The main thing I'd like to see recognised one day is the great work done by knowledgable and committed service engineers and aircrew (and BAES engineers) who kept the US/UK lines open through the late 80s and early to mid 90s. their unsung work is the reason the UK was able to get its special 'Tier 1' partner status on JSF. Some of them should have got gongs. Most of them didn't.
Best,
Courtney
The UK didn't formally join the program until 2001? I don't know how much money was involved, but there was certainly deep involvement.
Ambassador Kerr: Three words from the United Kingdom Government -- priority, confidence, partnership.
Collaboration on JSF is a very high priority for the United Kingdom Government because it is the prime way in which we see our meeting the Royal Navy's requirements for a STOVL [Short takeoff and vertical landing] follow-on to our present Sea Harriers...So JSF is a very high priority for the United Kingdom.
Confidence. The United Kingdom Government has a rather high confidence in this program, principally because of the attention Dr. Perry and Dr. Kaminski have explained, the attention that this program devotes to affordability. How to achieve the technological advance that is required at an affordable cost is a problem for defense procurement machines on both sides of the Atlantic. We think it is being extremely well addressed in the JSF program, so our confidence in JSF is high.
Thirdly, partnership. The United Kingdom Government is very satisfied with the full consideration that has been given in this source selection process to the Royal Navy's requirements. The United Kingdom Government has been fully and satisfactorily involved at all stages of this selection. We are confident that an equitable and significant share of JSF work will go to U.K. industry, and we believe there's a very real determination -- I speak for the British team -- but there's a real determination in both parts of the JSF Team -- American and British we think -- to make this U.S./U.K. collaboration a significant success.
Defense.gov Transcript: DOD News Briefing
Clearly there was enough involvement by 1994 for BAE to join McAir's "dream team", which meant significant contact with Wiechmann's very sensitive stealth tech in the Phantom Works.
Ambassador Kerr: Three words from the United Kingdom Government -- priority, confidence, partnership.
Collaboration on JSF is a very high priority for the United Kingdom Government because it is the prime way in which we see our meeting the Royal Navy's requirements for a STOVL [Short takeoff and vertical landing] follow-on to our present Sea Harriers...So JSF is a very high priority for the United Kingdom.
Confidence. The United Kingdom Government has a rather high confidence in this program, principally because of the attention Dr. Perry and Dr. Kaminski have explained, the attention that this program devotes to affordability. How to achieve the technological advance that is required at an affordable cost is a problem for defense procurement machines on both sides of the Atlantic. We think it is being extremely well addressed in the JSF program, so our confidence in JSF is high.
Thirdly, partnership. The United Kingdom Government is very satisfied with the full consideration that has been given in this source selection process to the Royal Navy's requirements. The United Kingdom Government has been fully and satisfactorily involved at all stages of this selection. We are confident that an equitable and significant share of JSF work will go to U.K. industry, and we believe there's a very real determination -- I speak for the British team -- but there's a real determination in both parts of the JSF Team -- American and British we think -- to make this U.S./U.K. collaboration a significant success.
Defense.gov Transcript: DOD News Briefing
Clearly there was enough involvement by 1994 for BAE to join McAir's "dream team", which meant significant contact with Wiechmann's very sensitive stealth tech in the Phantom Works.
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LO,
I won't get into a 'who knows what' argument here - I can only set out what I know. If others know more/different, then just fine.
There was no UK money committed until 2001, apart from limited personnel costs.
The quote you set out was from 1996, and confirms that the US was being sighted on UK requirements (NST 6466) - but the UK's influence on the US decision was limited - very limited. We informed the process from our own UK STOVL knowledge, and from UK MoD advanced engine studies, but it was a US programme we were given (privileged) access to - not a joint programme in any way shape or form.
The contribution of the key personnel who kept those comms channels open during those intermediate years was immense - I think we can agree on that.
Courtney,
You'd be interested to know that for a typical air to air burst length, the Mauser puts more shells on target than the 25mm Gatling. All Gatlings take a while to get spun up). And the 25mm round, while very good, isn't as good as the 27mm. However, water under the bridge and all that.
Best Regards as ever to those who did the hard yards
Engines
I won't get into a 'who knows what' argument here - I can only set out what I know. If others know more/different, then just fine.
There was no UK money committed until 2001, apart from limited personnel costs.
The quote you set out was from 1996, and confirms that the US was being sighted on UK requirements (NST 6466) - but the UK's influence on the US decision was limited - very limited. We informed the process from our own UK STOVL knowledge, and from UK MoD advanced engine studies, but it was a US programme we were given (privileged) access to - not a joint programme in any way shape or form.
The contribution of the key personnel who kept those comms channels open during those intermediate years was immense - I think we can agree on that.
Courtney,
You'd be interested to know that for a typical air to air burst length, the Mauser puts more shells on target than the 25mm Gatling. All Gatlings take a while to get spun up). And the 25mm round, while very good, isn't as good as the 27mm. However, water under the bridge and all that.
Best Regards as ever to those who did the hard yards
Engines