F-35 Cancelled, then what ?
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Courtney. I appreciate the issue is serious, but I use 'critical' in its literal sense. Rumour is that its back to the drawing board...the original one! If true, this whole program becomes the biggest white elephant in military history.
LO. No, and the 'silence' there is deafening too. The only comment I've read came from Bogdan..."it was quite a blaze"..
LO. No, and the 'silence' there is deafening too. The only comment I've read came from Bogdan..."it was quite a blaze"..
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Below the Glidepath - not correcting
The 2 "solutions" to the F-135 problem are to (a), bed in the abradable seals i.e. in a tightly controlled operating environment - which implies operating limitations until bedded in, and (b), pre-cutting wear channels in the abradable seals - which seems to negate the entire point of an abradable seal. The root cause still lies in determining if the core shaft flex (due to inertial and gyroscopic forces) will cause a reoccurence of the friction and excessive heat during "normal" operations and manoevers.
Just how much material can you remove during weight saving measures and still maintain the required rigidity of the design? I'm sure someone at PW is pondering that question. The way to get it out of spotlight and get to IOC would of course be to impose a restricted operating regime that avoids the engine problem all together but creates an artifically benign operating environment. I'm sure no-one would even consider that.
Just how much material can you remove during weight saving measures and still maintain the required rigidity of the design? I'm sure someone at PW is pondering that question. The way to get it out of spotlight and get to IOC would of course be to impose a restricted operating regime that avoids the engine problem all together but creates an artifically benign operating environment. I'm sure no-one would even consider that.
Do a Hover - it avoids G
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Good points Two's in
In the early days of the Harrier/Pegasus combination we had fan rubs following very high pitch rate manoeuvres. The pitch rates (and so gyroscopic forces) involved were way beyond the envelope then used for designing engines and were achieved during low speed combat manoeuvres made possible by using the reaction controls. The engine men sorted it as a normal part of the aircraft/engine development programme.
The other similar development issue was that the USMC used the nozzle lever at high IAS to destroy the enemies aiming solution. This raised much higher stresses in the nozzle actuation system than was expected as they had only been designed for up to 250kt IAS.
Easy – tell them not to do it said the designers.
Rubbish said the company pilots because if it helps pilots to achieve their task pilots will do it (whatever it is). So we strengthened things to allow them to go to reverse thrust at reasonably high speeds and made the actuator stall at about 40deg nozzle at silly speeds. After this initial nozzle deflection killed the speed a tad the actuator unstalled and the nozzles went all the way.
So I wonder if the rub that caused the fire resulted from a manoeuvre inside or outside the engine design spec and so will the accountants I guess.
As for the manoeuvre itself, if it turns out that the aerodynamics can hand out more than was expected that will be very good news for operators in the longer term. However in the end the engine men will have to tolerate what the airframe can do.
In the early days of the Harrier/Pegasus combination we had fan rubs following very high pitch rate manoeuvres. The pitch rates (and so gyroscopic forces) involved were way beyond the envelope then used for designing engines and were achieved during low speed combat manoeuvres made possible by using the reaction controls. The engine men sorted it as a normal part of the aircraft/engine development programme.
The other similar development issue was that the USMC used the nozzle lever at high IAS to destroy the enemies aiming solution. This raised much higher stresses in the nozzle actuation system than was expected as they had only been designed for up to 250kt IAS.
Easy – tell them not to do it said the designers.
Rubbish said the company pilots because if it helps pilots to achieve their task pilots will do it (whatever it is). So we strengthened things to allow them to go to reverse thrust at reasonably high speeds and made the actuator stall at about 40deg nozzle at silly speeds. After this initial nozzle deflection killed the speed a tad the actuator unstalled and the nozzles went all the way.
So I wonder if the rub that caused the fire resulted from a manoeuvre inside or outside the engine design spec and so will the accountants I guess.
As for the manoeuvre itself, if it turns out that the aerodynamics can hand out more than was expected that will be very good news for operators in the longer term. However in the end the engine men will have to tolerate what the airframe can do.
Very big engine. G(z) airframe and mass items limits already reduced. Production already going ahead whilst testing still has a long way to go. Carrying known faults. Customers over a barrel. Project Office with too much to lose and defensive of the project. Customers with shrinking budgets vs increasing unit and support costs. Over-reliance on narrow-band stealth. Range, payload and performance compromises to achieve STORVL capability. Uncertainty about ioc dates and capabilities.
Well, the list could go on, but as someone that really wanted this to work, I'm seeing this program in a very dark place. I don't doubt the amazing technological advances et al, but this not looking good. Too big to fail? Yes. Concurrent design/testing/building has too many people locked in.
The obvious lack of openness and updates on the engine failure is seriously turning me off this programme. Yes, I've seen all the parallels with other plants.
Right now I think we'll eventually end up with a platform that does stuff, but I think we're in danger of not having a great one. And not many of them. Disappointing, worrying and uncertain times.
Sorry guys, I'm very worried now.
EDIT. No, John Farley, the operators may have to tolerate what the engine can stand. But I admire your glass half full approach.
Well, the list could go on, but as someone that really wanted this to work, I'm seeing this program in a very dark place. I don't doubt the amazing technological advances et al, but this not looking good. Too big to fail? Yes. Concurrent design/testing/building has too many people locked in.
The obvious lack of openness and updates on the engine failure is seriously turning me off this programme. Yes, I've seen all the parallels with other plants.
Right now I think we'll eventually end up with a platform that does stuff, but I think we're in danger of not having a great one. And not many of them. Disappointing, worrying and uncertain times.
Sorry guys, I'm very worried now.
EDIT. No, John Farley, the operators may have to tolerate what the engine can stand. But I admire your glass half full approach.
I do hope I am proved wrong, but I have a feeling in my water it will all end in tears, and squillions of £, $, €, will have been expended for no useful result. Then what..................
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Original quote by CM: I think this could be classed as a serious design flaw.
Right now I think we'll eventually end up with a platform that does stuff, but I think we're in danger of not having a great one.
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..So I wonder if the rub that caused the fire resulted from a manoeuvre inside or outside the engine design spec and so will the accountants I guess...
“That’s why we’re worried, if it were outside the envelope we’d say just don’t fly there but it was inside the envelope, so that’s why we have to fix it.”
LF
FWIW (not very much) in the software industry people have this kind of problem all the time. A developer can't offer sensible, achievable features because they wouldn't get the contract. So they have to be bull****ters to make a sale.
There's some finite time or amount of money available so there has to be some invented "reason" or other for ignoring experience about how long things take or how much they cost. In software the current "reason for ignoring experience" is agile development which, sort of ironically, is about how to cut features to fit time and budget. Nobody actually does it properly because their contract specifications would not be met. Contracts are written at the beginning of a project when everyone knows the least about how feasible each feature is.
Ultimately it's all an excuse for coping with human problems of trying to decide what you want before you understand all the problems fully and not being prepared to pay a reasonable price for a reasonable outcome. To get the money, magic must be promised.
There's some finite time or amount of money available so there has to be some invented "reason" or other for ignoring experience about how long things take or how much they cost. In software the current "reason for ignoring experience" is agile development which, sort of ironically, is about how to cut features to fit time and budget. Nobody actually does it properly because their contract specifications would not be met. Contracts are written at the beginning of a project when everyone knows the least about how feasible each feature is.
Ultimately it's all an excuse for coping with human problems of trying to decide what you want before you understand all the problems fully and not being prepared to pay a reasonable price for a reasonable outcome. To get the money, magic must be promised.
Last edited by t43562; 13th Oct 2014 at 07:10. Reason: clarification
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t43562, surely you aren't suggesting the Contractors invovled in the F-35 program made promises to meet customer targets that they knew were improbable at best, are you? 
There are already inunerable Contract Variation Proposals to sort through, irrespective of the engine issue. I see this all ending up in a court room tbh.
There are already inunerable Contract Variation Proposals to sort through, irrespective of the engine issue. I see this all ending up in a court room tbh.
I take those points about promising "magic", but I do think P&W thought they could (hopefully still can) do it. It wouldn't have been good for them or anyone else if things were otherwise. That, of course, doesn't make the issue any less grave. As t43562 says, this will doubless be a significant redesign, which could involve some effect on the whole platform.
It was always a 'big ask' (sorry, I don't like that expression either), but that's how boundariesare pushed. One of the consequences of this concurrent development is that so many aspects of this program are now stalled.
There is no plan B, so this had better work. I always understood and was disappointed by the spec of this thing. My hopes for the final product are not high anymore.
It was always a 'big ask' (sorry, I don't like that expression either), but that's how boundariesare pushed. One of the consequences of this concurrent development is that so many aspects of this program are now stalled.
There is no plan B, so this had better work. I always understood and was disappointed by the spec of this thing. My hopes for the final product are not high anymore.
Do a Hover - it avoids G
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I am not so pessimistic as some here for two reasons.
Firstly the likely length of the programme (in my view 60 years starting in 2000) and secondly the fact that the operators (all of them) have so much to learn about how to use the gradually emerging operational systems (surely more capable and complex than with any other new single seat aircraft) that to have a restricted manoeuvre envelope (even for a few years) while the engine is sorted is actually not a problem so far as the guys in the crew rooms are concerned.
I do realise that the politics, the finances, the sales and the PR aspects will have their own very serious issues about all this (and doubtless other engineering problems that could well appear later!) but I would still love to be in an F-35 crew room while it is all gradually sorted, because I would have plenty of super stuff to do.
Firstly the likely length of the programme (in my view 60 years starting in 2000) and secondly the fact that the operators (all of them) have so much to learn about how to use the gradually emerging operational systems (surely more capable and complex than with any other new single seat aircraft) that to have a restricted manoeuvre envelope (even for a few years) while the engine is sorted is actually not a problem so far as the guys in the crew rooms are concerned.
I do realise that the politics, the finances, the sales and the PR aspects will have their own very serious issues about all this (and doubtless other engineering problems that could well appear later!) but I would still love to be in an F-35 crew room while it is all gradually sorted, because I would have plenty of super stuff to do.
Depends on the restrictions, John. In the air-to-air (defensive or offensive) performance (speed, manoeuvre, altitude, etc.) is vital. We've already seen significant reductions in some of these; more could seriously degrade effectiveness and survivability.
I'd love to feel as up-beat and confident about it as you clearly do. Yes, there will be lots of toys to play with, but the toys aren't much use if the performance is further limited.
I'd love to feel as up-beat and confident about it as you clearly do. Yes, there will be lots of toys to play with, but the toys aren't much use if the performance is further limited.
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LowObservable wrote:
"No photos of AF-27 have been released either. "John Hurt in Alien", is one description."
It's a wonder why some intrepid reporter hasn't filed a FOIA request....
"No photos of AF-27 have been released either. "John Hurt in Alien", is one description."
It's a wonder why some intrepid reporter hasn't filed a FOIA request....