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F-35 Cancelled, then what ?

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F-35 Cancelled, then what ?

Old 31st May 2015, 00:19
  #6101 (permalink)  
 
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By the time Dave reaches IOC over here there'll probably be -D, -E and -Fs on the production line.
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Old 31st May 2015, 00:40
  #6102 (permalink)  
 
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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.
God, I hope not, the, -A, -B and -C's are bad enough!

-RP
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Old 31st May 2015, 10:47
  #6103 (permalink)  
 
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engine updates ?

Mach 2 asked -
Has there been any news about the engine issue?
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
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Old 31st May 2015, 11:39
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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.
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Old 31st May 2015, 12:26
  #6105 (permalink)  
 
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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.
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Old 31st May 2015, 12:26
  #6106 (permalink)  
 
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MTBF = 25/45/25. I see your point MT. But don't lose faith because

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.
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.
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Old 31st May 2015, 13:46
  #6107 (permalink)  
 
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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.
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Old 31st May 2015, 13:54
  #6108 (permalink)  
 
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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.
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Old 31st May 2015, 14:35
  #6109 (permalink)  
 
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LO,

The F135 is established and mature, with production engines set for delivery later this year after more than 12,000 hours of testing.
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".

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.
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.
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Old 31st May 2015, 15:29
  #6110 (permalink)  
 
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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.
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Old 31st May 2015, 15:58
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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
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Old 31st May 2015, 16:05
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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.
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Old 31st May 2015, 16:25
  #6113 (permalink)  
 
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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....
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Old 31st May 2015, 16:29
  #6114 (permalink)  
 
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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.

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.
Although I don't know about their entitlement to "gongs", I second your proposal. Recognition is well deserved and long overdue.

Best,

Courtney
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Old 31st May 2015, 18:00
  #6115 (permalink)  
 
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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.
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Old 31st May 2015, 21:45
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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
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Old 31st May 2015, 21:56
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It's official!

F-35 is

"badASS"

there's even a video..



So it must be true.....

Question. What is the similarity between F-35 and Climate gate??

Ans. True believers will literally say and do anything for the "cause".....

Last edited by glad rag; 31st May 2015 at 22:03. Reason: ho hum.
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Old 31st May 2015, 22:44
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Originally Posted by Engines
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.
On paper, you are right, Engines. I rarely take issue with you, but here we must disagree.

Firing the Mauser air-to-air or air-to-ground is a death ray. I have had consistently good results with it in the F-3. The high muzzle velocity, the stable barrel and the virtually instant start are all excellent features that make it that way.

I used the 20mm Gatling on the F-4 as a podded gun (a-a and a-g) and in the F-15 (a-a). Apart from the harmonisation issues on the F-4, they were, essentially the same weapon, but with an amazing aiming system in the Eagle. Against benign targets, allowing for a relatively short spin-up time, the Gatling is sufficiently accurate. Maybe not the death ray, but I could hit targets with it.

Now the differences.

1500 rounds per minute in a single stream, 260g projectile. 6000 rounds per minute, probably half that weight. I would need to put, maybe, 3 rounds through a target to hurt it with the Mauser, I would probably need 5 with the 20mm Gatling. Against a benign target, a dart or a flag, I would probably achieve the required number of hits very easily with the Mauser.

Against a manoeuvring target, when my aircraft isn't necessarily at the ideal speed or attacking position (as I would have from an academic, training set-up) things are very different. I may not be able to track the target. If I can, it may not be the ideal QWI firing solution. It may be a raking pass. It may be a very high angle-off or even close to head-on. Under those circumstances the death ray would be great only if I can point it at the target accurately enough and long enough to hit it - a few times. Distance between rounds becomes a much more significant factor. And that is where the 6000 rpm becomes such a dominant issue. And in that situation one doesn't need to wait until the sighting solution is perfect, rather one opens fire early so the spin-up time is no longer a factor.

Who would use a rifle to hit a flying bird? I would choose a shotgun.

On paper, yes, the Mauser looks good. And it is an excellent weapon. Given the choice in the less benign environment of combat ops, I would be very happy with the Gatling.

Differences in calibre. Yes, hence more hits required for the Gatling and remember I have been talking 20mm, not 25. I once stood in the Royal Ordinance Factory's test range and watched the difference between 30mm HE Aden Cannon rounds at 1200 rpm and the Vulcan cannon. The destructive power of the Aden was incredible. The move to 25mm closes that gap hugely, especially at the higher rate of fire.
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Old 31st May 2015, 23:29
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As I understand it there has been not a lot of if any trials of SRVL, rolling landing on the QEC class carriers
I am not aware that any aircraft has landed on any QE class ship, so that does rather mean that no SRVL trials on QE class ships (can I call them boats yet?) have taken place. However SRVL has been done for real by a digital STOVL jet pretending to be an F-35B, on a ship that was, for demonstration purposes, a passable stand-in for a QE class ship (but it wasn't as fast, the flight deck wasn't welded on straight with regards to the rest of the ship and other aircraft kept turning up and knocking lumps out of the deck paint). It's been done, lots and lots, by simulated F-35Bs on simulated QE class ships (and other ships). Hard sums have been done to look at amongst other things, the sort of tedious metal bendy stuff that excites people if for some reason something goes "twang" unexpectedly. Or possibly "crack". People are still interested in having a go for real, which might suggest to you that there are least some people that think it's not a lost cause. We'll see.

, this is necessary to enable a loaded F35B to return to the ship with weapons aboard.
No it isn't. I suspect you might mean something like "very heavily loaded in weather conditions that are unfavourable", in which case you have a point. But that's not going to happen all the time is it? I leave it an an exercise for you to work out how often it will happen. However, my point is that F-35Bs loaded with (inert) weapons have already landed on ships, so clearly SRVL is not an essential pre-requisite.

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....
like I said, "hard sums". But hey, the Harrier's undercarriage was designed well before ski-jumps were invented and you had to work pretty hard to break them by doing a ski-jump. Like by steering off the side or taking way too long a run-up and having the nose-leg go "twang" on ramp-exit, (on the occasion I know of, because the bloke given the job of marking the take-off roll start line during land-based ski-jump trials didn't appreciate that the distance was referenced to ramp-exit, not the base of the ramp. Fortunately, the aircraft landed safely with a bust nose-leg, 'cos STOVL jets can do that, and subsequently had a long and interesting flight test career including doing the SRVL thingy which failed to break any more legs).

If "Engines" had written this post he would have been a bit more polite. But he's a bit more professional than I am, whereas I've just seen this stuff done and felt I ought to say something.
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Old 1st Jun 2015, 09:50
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No Hover
Yes I am aware that SRVL has been simulated, I am also aware that the landing of an F35C on a UK Carrier was simulated as a fait accompli, this was before it became apparent that there were problems with the hook catching a wire, since resolved. Something can be simulated with all the best inputs but it does not necessarily mean that the real aircraft will behave as the simulator suggests.

There was a discussion I think on here about the bring back weight for a Vertical Landing for an F35B and as I recall it did not allow much unused ordnance to return to the ship, implicitly this might mean having to drop say an unused Storm Shadow into the drink, yes when the interface has been done, also as far as I am aware the F35B is not cleared to use any external points at the moment so has at most been taking off and landing on USS Wasp with a full tank of fuel, 2 1,000 lb bombs and two AMRAAMs, not a particularly heavy load out.

As regards trials of SRVL, I think that you are confirming that as far as anyone is aware there have been no trials of this sort of landing on an area similar to that available on a QEC Carrier. My point was that as much of the flight control of the F35 is down to software, it would seem that, if I am correct, that the software for SRVL has yet to be tested on an actual development aircraft and implicitly therefore has not been released to the fleet.
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