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F-35B down.

Old 30th Sep 2018, 15:54
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Originally Posted by Finningley Boy
I've no idea I'm sure you'll be utterly surprised to hear. I simply asked if there was a trend affecting the B and not the other two, it could be a common fault or it could be simple bad luck! That's the extent of my technical knowledge, but you sound like you have far greater insight! Could it be that there is a problem, yet to be determined, affecting the drive shaft for the great rotating dustbin which hoovers up internal capacity and re-shapes the airframe? I don't know.

FB
I certainly know no more than what's in the public domain but you seem to be pointing directly to the lift fan. Nowhere in any of the press reports have I seen mention of lift fan issues
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Old 30th Sep 2018, 18:12
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Originally Posted by Finningley Boy
I've no idea I'm sure you'll be utterly surprised to hear. I simply asked if there was a trend affecting the B and not the other two, it could be a common fault or it could be simple bad luck! That's the extent of my technical knowledge, but you sound like you have far greater insight! Could it be that there is a problem, yet to be determined, affecting the drive shaft for the great rotating dustbin which hoovers up internal capacity and re-shapes the airframe? I don't know.

FB
Finningley,

May I offer the following observations?

Yes, it's quite possible that there is a problem with the drive shaft. Even after the (literally) tens of thousands of hours of test rig work, full scale tests, testing of actual production hardware spanning tens of thousands of operating cycles, yes, it's possible that there is a problem with the lift fan drive shaft. Or not. Or there may be a problem with the huge 'dustbin' at the aft end of the aircraft that burns highly flammable fuel and runs at incredibly high speed. Or not. The lift fan certainly does occupy internal capacity. And yes, it reshapes the airframe. A bit like the weapons bays, and almost every other bit of equipment in the aircraft of whatever variant. But if you have a requirement for a STOVL capability, you need a powered lift system. This will impact the design. It's called a design trade off.

This is the first F-35 lost, after nearly 12 years and well over 100,000 flying hours. That's not a bad achievement, and British engineers (and pilots) have played a huge part in it. Might be nice, once in a while, to acknowledge that.

Once again, sincere best regards to the pilot, I hope that the excellent UK sourced Martin Baker seat has done its job, as MB seats have invariably done for many years. And best regards to all those on the programme who will now be working flat out to find out what caused this crash.

Engines
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Old 30th Sep 2018, 18:33
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FOD Plod,

My understanding is that any F-35As wouldn't be for the aircraft carriers. I'm sure that it would be folly to buy 138 F-35Bs just so that both carriers can set sail with a deck crowded with F-35Bs. For two carriers, 48 I'm sure would be enough to ensure that as likely only one would be on task at any time, a full compliment was on board. My understanding is the A version has a better performance can carry more fuel and ordnance.

Harley Quinn,


I think you're reading more into my comments than is actually there, I simply mentioned the lift fan as I do believe it is an unnecessary loss of space and taxation on everything it can't carry otherwise. It also means more fuel has to be used for the main engine to drive the shaft. I didn't even hint that the lift fan had anything to do with the crash. My simple innocuous question was is there an under lying problem with the F-35B as it appears to be (not is) troubled more than the other two variants. I certainly never even alluded to the cause or suggested there was only a single cause. But if you want a personal opinion on the matter, then yes, I think the F-35B is unduly limited in performance and payload, not because I possess any erudite knowledge but because it stands to reason, for all the obvious reasons, lift fan engine, extra drain on fuel, increased premium on space, additional weight penalty in conventional flight, in which mode it will spend very much most of its time aloft.

Engines

I take your points, many thanks.

FB

Last edited by Finningley Boy; 30th Sep 2018 at 18:38. Reason: ADD MORE
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Old 30th Sep 2018, 20:44
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Finningley,

Glad I was able to be of help. Perhaps I can offer a little more help.

The basic point is that the F-35B is required to be a STOVL aircraft. This means that it has to pay a range/payload penalty. This was known and understood from the outset, and the original JSF requirement document reflected this in a shorter range requirement and reduced weapons carriage requirements (amongst other things).

The UK is buying a STOVL aircraft because that's what the original UK requirement (NST 6464) was for - a Sea Harrier replacement to operate from RN ships. The UK got its Tier 1 level partnership partly due to its STOVL knowledge and expertise - the US JPO acknowledged that the STOVL variant was technically the most risky and they needed our help. NST6464 morphed into Future Carrier Based Aircraft (FCBA) and on formation of Joint Force Harrier, FCBA was renamed FJCA (Future Joint Combat Aircraft). None of this should obscure the fact that the UK said it wanted a STOVL aircraft and that it what it's getting. What has changed, and I think sometimes isn't clearly spelt out, is that the F-35B is now being required to be a Tornado replacement as well. I can fully understand that some RAF aircrew would see the need for a Tornado replacement as being more important that getting an aircraft to operate from aircraft carriers.

I'll repeat what I have posted many times - to me it would make sense for the UK to formally investigate a revised F-35 buy, replacing 138 F-35Bs with (say) 85 Bs and 65 less expensive As. The two variants could use a largely common training and support system, reducing the additional costs of running the two variants. The As could then come under full operational control of Air Command, with the Bs under Sea Command. Bs could still 'flex' over to land based roles by Sea Command if requested by Air.

For all I know this has already been looked at. Just my thoughts.

Incidentally, the F-35B doesn't need 'more' fuel to drive the lift fan shaft. The main engine operates as per usual, and the shaft extracts around half the power down the shaft to drive the fan. Because the fan is using cold air, the overall lift is developed using less fuel than by other options. When the F-35B does a VL, the main nozzle is actually operating at about half full thrust. Hope this helps.

Best regards as ever to all those working out the future force details,

Engines
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Old 30th Sep 2018, 21:13
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Salute!

TNX, Engines for good poop'

I, too, think the fan drive shaft could be a factor in Bee emergencies. Depending upon how close to touchdown in landing mode, seems possible you could still revert to conventional flight controls and such. The F-102 I flew a century ago would go ballistic in seconds if the "angle drive shaft" failed. It connected the motor to the hydraulic and electrical system pumps/generators. So Convair added some back up systems to prevent complete loss of control. My trusty Sluf had a RAT for that kinda problem, and my Viper had the EPU whicj ran on hydrazine or bleed air depending if the motor was still running.

I have watched the Stubbies here at Eglin make approaches with all the doors open but not always wind up in a hover as they would on the new Brit carrier or even for a short roll landing on terra firma. So seems an early warning could allow one to land conventionally.

Gums sends...
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Old 30th Sep 2018, 23:46
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For two carriers, 48 I'm sure would be enough to ensure that as likely only one would be on task at any time,
What about when both are on task....say the Falklands Redux or something similar?
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Old 1st Oct 2018, 07:38
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Originally Posted by SASless
What about when both are on task....say the Falklands Redux or something similar?
If both ever have to deploy with a full compliment of 36 F-35s a piece then two carriers plain and simple won't be enough, we're going to need a much bigger defence budget. As it is, we'll have both carriers at sea before we get even just 48 aircraft in total and we can be sure not all of those will be available at once. The rate of production and delivery is planned to be very slow indeed and I can't see that even if we could place 72 F-35s at sea at once, that such a large scale deployment to respond to a resurgent threat to the Falklands, would be at all likely. There seems to be a craven desire in some quarters for all 138 F-35s to be STOVL capable and all therefore able to go on the carriers. This may have been the thinking when the F-35 was seen as a Harrier/Sea Harrier replacement and nothing beyond. But it isn't, it is now the principal replacement for the Tornado GR as well. Any F-35s, which would be operating from land bases, including overseas deployments, would be better off as CTOL variants. As ENGINES has pointed out a mix would be the best solution. An approximate split in the 138 along a 50-50 ratio would mean 69 of each. One more point, if vertical lift and hovering is such a must have ingredient and not simply a patriotic British nod to our heritage in inventing vectored thrust, then surely everyone else; Netherlands, Belgium, Norway, Denmark, Canada, Australia, Israel, Italy, USAF and USN would settle for it.

FB
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Old 1st Oct 2018, 08:17
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If both ever have to deploy with a full compliment of 36 F-35s a piece
I believe the latest statements from the MoD indicate that the normal complement will now be 24 aircraft rather than 36.

The general consensus would seem to be that the F-35B is the most successful of the three models, both the USMC and RN getting the other services to pay enormous amounts of cash for sub-optimal aircraft so they could get a far more effective platform to replace the Harrier. The USN in the meantime seems to buying new F/A-18s and how many F-35Cs will be bought remains to be seen; whilst the USAF F-35A buy seems to be increasingly caught up in arguments and proposals for either upgrading F-16s, building an F-22/35 hybrid or bringing forward the proposed long range penetrating fighter.

Regards splitting the UK order for F-35Bs would more probably lead to an additional purchase of further upgraded Typhoons rather than any F-35As without probes.
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Old 1st Oct 2018, 09:13
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Originally Posted by gums
Salute!
I have watched the Stubbies here at Eglin make approaches with all the doors open but not always wind up in a hover as they would on the new Brit carrier or even for a short roll landing on terra firma. So seems an early warning could allow one to land conventionally.
The Bs at Marham all seem to land with 'everything open' even when doing rolling landings - and the "short rolling vertical landing" is planned to be an operational mode on board the carriers to use less fuel than the traditional VL style
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Old 1st Oct 2018, 09:59
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Gums,

Thanks for coming back - I can offer some information on the F-35B lift system that may be of interest to you.

First, it might be of help to outline the way the F-35B achieves 'powered lift' flight. Power is extracted from the main engine by a shaft which drives the lift fan. The lift fan is aligned vertically, so generates a forward pillar of cold gas. The aft 'lift pillar' is generated by using a three Bearing Swivel Module (3BSM) located between the main engine's aft turbine stage and the nozzle. The 3BSM rotates through 90 degrees to generate the aft 'pilar' of hot gas. (By the way, both the 3BSM and the lift fan were designed by Rolls Royce). Both 'pillars' can be controlled in thrust and direction to control the aircraft.

The lift fan drive shaft runs between the first stage of the engine and a clutch/gearbox assembly on the aft side of the lift fan. The shaft is fixed to the LP shaft of the engine and rotates all the time. When going into 'powered lift' mode, the clutch is engaged, the shaft spins up the lift fan, and when the fan has fully spun up to shaft speed, the two are mechanically locked. The clutch is then disengaged. Going from "powered lift' to normal flight is the reverse procedure. 'Powered lift' mode is selected by a switch on the left hand control in the cockpit. This selection initiates the process I've just outlined, plus a lot of other stuff in around 15 seconds. This includes:
  • Upper lift fan door opens
  • Lower lift fan doors (2 off) open
  • Upper auxiliary air intake doors (2 off) open
  • Aft 3BSM doors (2 off) open
  • 3BSM swivels downwards
  • Roll post doors, one in each wing lower surface, open and roll post nozzles move downwards to clear wing aperture. (The roll posts are fed by bypass air from the main engine and provide roll control as well as around 2000 pounds of thrust)
  • Inboard weapons bay doors are partially opened to help control flows of hot and cold gas around the aircraft
  • All control surfaces are moved to optimise lift system thrust by controlling movement of air around the aircraft.
  • Aircraft flight control software transitions from normal wing borne control laws to powered lift control laws
  • Pilot controls change their function from 'wing borne' to 'powered lift' - in powered lift, pilot has no control over aircraft pitch attitude. Right hand 'inceptor' now functions as a vertical rate demand input (fore and aft control movement) and lateral rate input (side to side control movement). Left hand inceptor now functions as a fore and aft rate input using fore and aft motion.

Note - this list is not exhaustive. What (I hope) this lot puts across is that the transition to and from powered lift mode is a seriously complex process, and there are no 'standby' or secondary' drives or options available. The main point is that once you have committed to sucking half the power out of the main engine forwards to the lift fan, you have to stay on two 'pillars' of gas. There are numerous sensors, interlocks, fault detectors and so forth built into the powered lift system, and the F-35B development programme was (quite understandably) driven by the customer to ensure that the pilot would either be prevented from engaging power lift in an unsafe condition, or would be prompted to switch back to wing borne flight as soon as an issue arose. However, sudden failure of the lift fan will cause the aircraft to pitch nose down very quickly, and I believe that the F-35B seat system is equipped with an automatic ejection feature.

The final point I would offer is that the F-35B has a wide powered lift flight envelope, all the way from zero knots to somewhere over 200 knots. The aircraft was required to be able to conduct landings in the powered lift mode all the way from a 'near conventional' to a full vertical recovery. I'm not surprised to hear that Eglin based aircraft are doing a range of rolling landings. For Dave, I am not sure that an RVL uses less fuel than a VL. I am fairly sure that for the Harrier/Sea Harrier, the most fuel efficient way to land was a conventional rolling landing with the nozzles aft (I am sure that a PPruner out there will correct me on this in the likely event that I'm wrong). Basically, the more time you spend not using the wings for lift, the more fuel you use.

The SRVL method for carrier use is driven solely by the Uk's desire to bring back heavier loads at higher temperatures and lower pressures than was called for in the JSF Requirement Document (the JORD). Fuel economy doesn't as far as I know, have anything to do with it. Again, I'm happy to be put right on that.

Hope all this stuff helps, best regards as ever to all the very bright and amazingly hard working Brits who worked with their equally talented US counterparts to make all this stuff work. I'm not sure they always get the credit they deserve.

Engines
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Old 1st Oct 2018, 12:16
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To illustrate the post from Engines:

From "MCAS Cherry Point, May 2018"



From "MCAS Cherry Point, May 2018"
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Old 1st Oct 2018, 13:12
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ORAC, FB,

I thought it might be helpful to other readers of this thread if I responded to your posts. As ever, please feel free to tell me if it's not. I do confess to being a little confused by the assertion that the 'general consensus' is that the F-35B is the 'most successful of the three models', apparently on the grounds that 'the USMC and RN (are) getting the other services to pay enormous amounts of cash for sub-optimal aircraft so they could get a far more effective platform to replace the Harrier'. It's hard to know where to start in responding to this, but my points of fact would be as follows:

The three F-35 variants arose from the Joint Strike Fighter programme, which was jointly funded by the USAF, USN and the UK MoD. The aim of the programme was to develop a family of three aircraft to replace a number of legacy aircraft that were becoming expensive to support. The JSF programme was bounded by a key restriction - the aircraft had to be single engined and single pilot. This was a DoD response to to massive cost overruns and failures of a number of USAF and USN tactical aircraft programmes over the preceding 15 years or so. The USAF and the USN (note that the USMC's budget is managed by the USN within DoD) joined the programme on the basis that developing a family of three aircraft would be cheaper than trying to develop three wholly different aircraft. Here in 2018, it's clear to all that the JSF/F-35 programme has experienced significant overruns in both cost and schedule. But to characterise the programme as the USMC and RN getting the other services (which I suppose means the USAF and the RAF) to 'pay for a 'Harrier Replacement' is, in my respectful view, a bit off the mark.

I would also question the assertion that the F-35B is a 'sub-optimal' aircraft. Yes, it has less range and payload than the F-35A. But by design, not by being 'worse'. To repeat, if you want a STOVL aircraft, you suffer a penalty. (Incidentally, the F-35C, as a 'cat and trap' design, suffers penalties as well, including maximum speed, acceleration and turn performance). If you mean that the F-35A and F-35C are 'sub-optimal', that rather begs the question of 'sub-optimal compared to what?'. Possibly to large twin engined, twin seat aircraft. Which were probably unaffordable (my view again). Rafale? Gripen?

It's useful to remember that the UK got into JSF because the MoD had endorsed the RN's requirement for a Sea Harrier replacement (NST 6464). That formed the basis for our entry into the JSF programme via what was titled 'The UK STOVL MoU'. That was FCBA. On the arrival of Joint Force Harrier, the UK's requirement was rebadged as FJCA, and the aim expanded to replace both the Sea Harrier and Harrier GR7/9 fleets. I believe that this was the basis for the development of the UK's '138' figure. (others may correct me). So to be clear - the UK's involvement in the JSF was for an RN/RAF Harrier replacement. Nobody was 'getting the RAF' to pay for 'their' aircraft, unless one assumes that all military aircraft development funds within the MoD 'belong' to the RAF. Personally, I don't.

The adoption of the F-35B as the 'Tornado replacement' was (in my personal view, happy to be told I'm wrong) a result of the MoD realising that the UK's defence budget could not afford another military aircraft procurement programme in the same timeframe as JSF. The MoD and the RAF had spent a lot of time and money on what were (in my opinion) non-starters such as a UK designed and built 1000 mile range stealth bomber, and the various FOAS studies. Moreover, by this time, Eurofighter/Typhoon was suffering massive cost and schedule overruns (not as widely reported as the issues with JSF/F-35, but that's the UK media and defence issues for you) which were threatening to overwhelm the MoD's procurement budget. Back in the late 1990s, I worked for a while for a truly exceptional MoD senior civil servant. He had briefing charts that clearly set out his view of the future for the RAF's combat aircraft fleet. That future was Typhoon to replace Tornado F3 and JSF to replace Tornado GR. How right he was.

As to USAF and USN F-35 buys, I've seen nothing to indicate that they are moving away from their stated acquisition plans. The USN has always planned to use F/A-18s for as long as they were combat capable, and buy new Super Hornets if the F-35 programme slipped. I've seen nothing from the USAF that shows any desire to build any more F-16s, and no news of any major F-15/F-16 life extension programmes. In my view (and only in my view), talk of an F-22/F-35 'hybrid' is speculative at best. While I worked at Fort Worth, I heard many Americans say openly that whatever they were going to do on F-35 'they sure as hell wouldn't do it like they did it on the legacy aircraft' - 'legacy' meant the F-22. The USAF's new 'long range fighter' is years away, and I am sure that wise heads in the DoD are dusting off their parametric studies to get a handle on the likely cost of a large, highly manoeuvrable,long range, twin engined aircraft.

I suppose what i'm trying to say (in a long winded way) is that trying to characterise the F-35B as a sub-optimal aircraft forced on the RAF by a cunning RN/USMC cabal is not only plain wrong, but a disservice to all those BAeS, RR, MoD, RN and RAF folk who have given their all to this programme and earned the UK much credit within the US service and industry community. I've seen young Brits (including RAF aircrew) absolutely stun US meetings with their calm, polite and utterly professional inputs. They have made a huge difference.

Best regards to all my old friends in the JSF programme, and to the young RN and RAF personnel getting ready to take the F-35B fleet forward.

Engines
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Old 1st Oct 2018, 13:14
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Nice post, Vzlet - they make the point perfectly!

Best regards

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Old 1st Oct 2018, 13:29
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Two words for Engines.

Bravo Zulu.
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Old 1st Oct 2018, 14:13
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Engines, did we sign up for 138 JCBA / JSF before or after the decision to build the QE class carriers? Ie, was it ever intended for them to operate from Invincible class ships?

( Unusually for prune this is a genuine question, I am not trying to make any points!)
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Old 1st Oct 2018, 14:25
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I would also question the assertion that the F-35B is a 'sub-optimal' aircraft.
I didn’t say the F-35B was suboptimal, on the contrary, I said that it is far more effective than the Harrier that it replaces.

What I did say was that was achieved by the other services having to accept suboptimal aircraft for their roles. I think you would agree that, if either had had the option to start with a clean sheet of paper, neither would have accepted the limitTions imposed by weight, size, structure etc which imposed to achieve the, limited, commonality eventually achieved.

I've seen nothing from the USAF that shows any desire to build any more F-16s, and no news of any major F-15/F-16 life extension programmes.
USAF To Keep Upgraded F-16s Till 2048 As Fate Of F-15C In Doubt - The Drive

https://insidedefense.com/insider/ai...-rfp-f-16-slep

https://www.airforcetimes.com/news/y...f-15cd-eagles/




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Old 1st Oct 2018, 14:49
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Salute!

Yeah, Dave and Engines.

The Stubbies I see here with all the doors open but flying a conventional pattern do not seem to have the nozzles deflected, so there must be one flight control law mode that transitions from "fan engaged" but no nozzle rotation, to full landing/hover.

One day I saw what appeared to be a demo of all three versions, maybe for some high rollers, heh? The Bee was last in line for the overhead pattern.(circuit for you Brits). All the doors open. So I pulled off the road and watched as they all came back and the A and C landed, but the B stopped over the runway and hovered for a few seconds. It then accelerated and did a closed pattern and a short rolling landing. I would estimate it rolled maybe 500 or 600 feet.

I have personally talked with one or more pilots, including the USMC dude that had a lotta influence on the landing mode. He was a Harrier pilot and suggested that with the FBW crapola the plane should have an easier landing mode than the Harrier. Hence, move throttle for fore and aft, and use stick for up/down plus some left right. Rudder for yaw. The USAF pilots flying the sim said it was like cheating to land on a boat!
++++++++++++++++++++++=

All must remember that the aircraft/weapon system must meet the nation's operational requirements to engage in combat. The Harrier was one example that the Brits have used in combat more than once. However, I agree with the proposal for Britain to have a mix of Bees with either the "A" or Cee. Like they did with the Harrier and to some extent the Tornado.

My best wishes for the Motherland's acquisition and employment of a plane from the colonists.

Gums sends...

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Old 1st Oct 2018, 14:55
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Hence, move throttle for fore and aft, and use stick for up/down plus some left right. Rudder for yaw.
Seems un-intuitive to me, I'd have expected throttle to be up-down, stick to be fore-aft.

A bit like... a helicopter!
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Old 1st Oct 2018, 15:30
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ORAC,.

Thanks for the response - it's always good to exchange views.

It looks as if the USAF is following the USN path and getting more life out of the F-16 as the F-35 deliveries have slipped. I would note that previous attempts to get more airframe life out of the F-16 fleet have not been a roaring success, and the RFP stuff you kindly supplied indicates a possible max of about 490 F-16s affected. The F-15X is still a proposal from Boeing, no sign of the USAF going there yet.

Yes, I'd absolutely agree that a 'clean sheet of paper' design for a USAF replacement for the F-15 and the F-16 would have been very different to the F-35A. Whether it would have been affordable as a separate programme is another matter. The USAF is just as good at 'gold plating' a requirement as any other Air Force.

I would offer the thought that the F-35 family has a little more commonality than some people think. Avionics and weapons systems are massive cost drivers for combat aircraft, and these systems are (I am led to understand) almost completely common across the three fleets. There are also common items across the main engines, another big cost driver. Ditto many of the aircraft systems components in the fuel, hydraulic, thermal management and electrical systems, as well as life support and escape. Also training and support programmes. And the fact that a single line is assembling and delivering all three variants.

Best regards as ever to the smart people managing the transition from one fleet of aircraft to another.

Engines
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Old 1st Oct 2018, 15:47
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Originally Posted by Timelord
Engines, did we sign up for 138 JCBA / JSF before or after the decision to build the QE class carriers? Ie, was it ever intended for them to operate from Invincible class ships?

( Unusually for prune this is a genuine question, I am not trying to make any points!)
Timelord,

Happy to help as best I can. I think that the 138 figure for FCBA was downstream of the decision to go for the carriers. My recollection is that it appeared at the first iteration of the list of the various partners' planned production totals in around 2002 ish. Note that these were never firm orders. The UK was the first customer to significantly alter their buy, slipping their delivery timelines well to the right, to the current dates.

The original NST6464 called for an aircraft that could be operated from the Invincible class ships. By the time the contracts was awarded to LM in October 2001, the JORD (Joint Operational Requirements Document) showed that the UK's ship/aircraft integration requirements had been pared right back to a series of what were essentially place holders. These included:
  • The aircraft had to be able to launch off an 'Invincible Class' ramp at a specific weight, configuration and take off run
  • The aircraft had to be 'dimensionally compatible with Invincible class flight deck and hangar layouts'. This meant that an F-35B could be physically parked on the flight or hangar deck. Notably, it didn't have to fit down the lifts
Over the next two to three years, the UK was working hard to find the best way to marry an as yet to be designed F-35B with an as yet to be designed CVF (which became the QE class). This was not at all straightforward. Among the first items that the UK added to their contract were studies into an optimised new ramp design for the CVF and the initial studies into Short Rolling Vertical Landings.

Sadly, most of this work was thrown into confusion in 2010 when the UK changed tack to the F-35C. Even more confusion ensued when they changed back in 2012. It has to be said that the UK's credibility within the US as an informed and reliable customer took a bit of a knock over that period. I think it says a lot for the strength of the relationship at the working level that we managed to rebuild our reputation on the programme.

Best Regards as ever to all those who have done the hard yards on the hard days,

Engines
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