LM new Fighter - F-22 and F-35 hybrid
KenV, it sounds like what's being proposed is basically an F-22 airframe and engines, with F-35 avionics.
Which interestingly is sort of what I had in mind in post #4. The F-22 airframe is brilliant for air-to-air with lots of room for internal stores and fuel, but the electronics date to the 1990's.
I really think what the USAF wanted is more F-22s, but didn't think they could afford them - but now the F-35 has gotten so expensive that the F-22 doesn't look so bad anymore. Convince the Japanese to pay to put the F-22 airframe back in production with modern avionics, then both the USAF and the Japanese get what they really want.
Of course, it's too logical - it'll never happen
Which interestingly is sort of what I had in mind in post #4. The F-22 airframe is brilliant for air-to-air with lots of room for internal stores and fuel, but the electronics date to the 1990's.
I really think what the USAF wanted is more F-22s, but didn't think they could afford them - but now the F-35 has gotten so expensive that the F-22 doesn't look so bad anymore. Convince the Japanese to pay to put the F-22 airframe back in production with modern avionics, then both the USAF and the Japanese get what they really want.
Of course, it's too logical - it'll never happen
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I can't see how this idea makes an iota of sense. The F-22's fast as hell, but woefully deficient in range and persistence. And if you were going to re-do the avionics you wouldn't use the F-35 architecture, which dates to the era when you could only fit one big computer on a fighter (so you time-shared it with the peripherals). I suspect this is an LM ploy to convince everyone that the only affordable option is to keep buying JSFs.
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Perhaps I can offer a couple of thoughts here that might help.
A successful aircraft design usually has potential for incremental development, like the F/A-18 did. However, this option isn't always possible. I have some doubts whether the F-22 airframe, which is highly optimised for high altitude BVR air to air combat, would be much use for any other role without massive changes. It's also horribly expensive to produce in its current form. During my time on the F-35 programme, one phrase I frequently heard was 'whatever else we do, we're not designing the 35 like the 'legacy' aircraft' - LM personnel were referring to the F-22. Sadly, that rule didn't stop them making some fairly severe mistakes when designing the F-35's airframe, which led to the weight reduction effort from 2004 onwards.
Any 'hybrid' design of an F-22 and an F-35 would have to make one huge decision - one engine or two. As I've previously posted, a major problem with large twin engined combat aircraft is cost. Make that a large, twin engined aircraft plus high sustained 'g' capability and internal weapons carriage, and you get an unaffordable aircraft - like the F-22. (Note that the F-22 was just one of a number of US large twin engined combat aircraft projects of the 80s and 90s that ran clean off the affordability rails). The F-35 is the outcome of a procurement strategy that deliberately mandated a single engined solution in an attempt (not especially successful) to generate a more affordable programme. ORAC is right on the money - it always comes down to requirements - what they are and how much the customer is wiling to trade off. Yes, you could stuff F-35 avionics into an F-22 airframe. Whether the capability of such an aircraft would be what the customers actually wanted would be another thing.
Going the other way, you could possibly develop the F-35 airframe to give it more air-to-air capability - one option I believe may have already been looked at by LM was a 'big wing' land based F-35, without the large weight penalty that the carrier capable F-35C has to carry. That might deliver an aircraft with improved sustained 'g' performance, and more range and endurance. However, I don't have visibility of the drag/weight/speed sums to make this anything more than a very sketchy guess.
Darn hard stuff, this highly integrated low observable combat aircraft design. Best regards as ever to the really smart people actually trying to do it.
Engines
A successful aircraft design usually has potential for incremental development, like the F/A-18 did. However, this option isn't always possible. I have some doubts whether the F-22 airframe, which is highly optimised for high altitude BVR air to air combat, would be much use for any other role without massive changes. It's also horribly expensive to produce in its current form. During my time on the F-35 programme, one phrase I frequently heard was 'whatever else we do, we're not designing the 35 like the 'legacy' aircraft' - LM personnel were referring to the F-22. Sadly, that rule didn't stop them making some fairly severe mistakes when designing the F-35's airframe, which led to the weight reduction effort from 2004 onwards.
Any 'hybrid' design of an F-22 and an F-35 would have to make one huge decision - one engine or two. As I've previously posted, a major problem with large twin engined combat aircraft is cost. Make that a large, twin engined aircraft plus high sustained 'g' capability and internal weapons carriage, and you get an unaffordable aircraft - like the F-22. (Note that the F-22 was just one of a number of US large twin engined combat aircraft projects of the 80s and 90s that ran clean off the affordability rails). The F-35 is the outcome of a procurement strategy that deliberately mandated a single engined solution in an attempt (not especially successful) to generate a more affordable programme. ORAC is right on the money - it always comes down to requirements - what they are and how much the customer is wiling to trade off. Yes, you could stuff F-35 avionics into an F-22 airframe. Whether the capability of such an aircraft would be what the customers actually wanted would be another thing.
Going the other way, you could possibly develop the F-35 airframe to give it more air-to-air capability - one option I believe may have already been looked at by LM was a 'big wing' land based F-35, without the large weight penalty that the carrier capable F-35C has to carry. That might deliver an aircraft with improved sustained 'g' performance, and more range and endurance. However, I don't have visibility of the drag/weight/speed sums to make this anything more than a very sketchy guess.
Darn hard stuff, this highly integrated low observable combat aircraft design. Best regards as ever to the really smart people actually trying to do it.
Engines
Last edited by Engines; 25th Apr 2018 at 13:28.
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TWC -
ORAC is, as ever, spot on. Bigger wings weight more, create more drag, reduce speeds and 'g' limits. You might be asking why they gave the F-35C a bigger wing if it causes all that trouble.
The answer is that an F-35C has to operate from an aircraft carrier using 'cat and trap'. The larger wing is designed to deliver the lower approach speed required for carrier recoveries, and also to allow safe launch from the catapult at the weights required. The larger tailplanes and fins provide the required control power at lower speeds. There is also (less visible) major structural strengthening required to handle cat and trap loads. All this generates a substantial weight penalty. On the plus side, you get longer range and better endurance.
However.......if you were to put a big wing on the F-35a, and leave out the extra structure required for cat and trap (thereby reducing weight), you would still get a significant increase in range and endurance, but still with penalties in .speed, 'g' and acceleration. I understand that LM may, at one time, have been looking at just such a design (the 'big wing A'), but I don''t think it ever made it past initial studies.
It's all down to what you actually need the aircraft to do. This does lead to my observation that a number of aircraft originally designed for carrier use have transitioned well to land based roles. Why? My own (and personal) opinion is that heftily built big winged naval aircraft (with plenty of power) often make good 'fighter bombers'. The F-4 Phantom was a good example of what I'm referring to here. More advanced aerodynamics and flight control systems have allowed these 'heftier' designs to become very good 'fighters' as well - liken the F/A-18.
Final thought - often, requirements for land based aircraft are driven by land based pilots - and these pilots often seem to value pure 'fighters' above 'fighters bombers'. In the case of the F-35, the 'A' variant had more demanding 'g' requirements than either the B or the C. Hence the smaller wing, optimised to meet that (and other) requirements.
Best regards as ever to all those making the hard requirements decisions
Engines
ORAC is, as ever, spot on. Bigger wings weight more, create more drag, reduce speeds and 'g' limits. You might be asking why they gave the F-35C a bigger wing if it causes all that trouble.
The answer is that an F-35C has to operate from an aircraft carrier using 'cat and trap'. The larger wing is designed to deliver the lower approach speed required for carrier recoveries, and also to allow safe launch from the catapult at the weights required. The larger tailplanes and fins provide the required control power at lower speeds. There is also (less visible) major structural strengthening required to handle cat and trap loads. All this generates a substantial weight penalty. On the plus side, you get longer range and better endurance.
However.......if you were to put a big wing on the F-35a, and leave out the extra structure required for cat and trap (thereby reducing weight), you would still get a significant increase in range and endurance, but still with penalties in .speed, 'g' and acceleration. I understand that LM may, at one time, have been looking at just such a design (the 'big wing A'), but I don''t think it ever made it past initial studies.
It's all down to what you actually need the aircraft to do. This does lead to my observation that a number of aircraft originally designed for carrier use have transitioned well to land based roles. Why? My own (and personal) opinion is that heftily built big winged naval aircraft (with plenty of power) often make good 'fighter bombers'. The F-4 Phantom was a good example of what I'm referring to here. More advanced aerodynamics and flight control systems have allowed these 'heftier' designs to become very good 'fighters' as well - liken the F/A-18.
Final thought - often, requirements for land based aircraft are driven by land based pilots - and these pilots often seem to value pure 'fighters' above 'fighters bombers'. In the case of the F-35, the 'A' variant had more demanding 'g' requirements than either the B or the C. Hence the smaller wing, optimised to meet that (and other) requirements.
Best regards as ever to all those making the hard requirements decisions
Engines
Engines, I don't recall where I heard it, but my understanding is that the F-35 form drag is horrible in the transonic/supersonic regions - regardless of the model. As a result the F-35 would never be really good at dog fighting (especially as compared to the F-22 which seems to be the gold standard).
While it's certainly true that a twin engine aircraft will cost more than a single engine, much of that cost advantage has been thrown away on the F-35 due to the need for the engine to be so powerful - making it the most expensive engine in history... Plus, a single engine aircraft will always have higher operational losses than a twin so there is a hidden cost.
While it's certainly true that a twin engine aircraft will cost more than a single engine, much of that cost advantage has been thrown away on the F-35 due to the need for the engine to be so powerful - making it the most expensive engine in history... Plus, a single engine aircraft will always have higher operational losses than a twin so there is a hidden cost.
Ecce Homo! Loquitur...
The 1 vs 2 engines is an age old argument. The single engine mafia will state that, over the life of the fleet, the additional loss of aircraft due to engine failure is less than the overall extra cost of engines/fuel etc. That might comfort the bean counters, but not the single engine pilot when his only one fails over the middle of the ocean. Which is why those who operate at long range from a suitable base over water or ice tend to vote for 2 rather than 1 engine.
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TDRacer,
Yes, the F-35 does have higher transonic form drag than the F-22 - but that's an inevitable consequence of the sort of aircraft the customer demanded. The F-22 is a large, long, relatively slim aircraft with shallow weapons bays optimised for AAM carriage. The F-35 isn't, because it can't be. During the redesign in 2004/5, the LM team made strenuous efforts to reduce form drag, which was certainly higher than they had predicted. There were a large number of 'tweaks' made to the Outer Mould Line (OML) in that period.
Whether the F-35 'would never be really good at dogfighting' is not a question I can really answer. What I would observe is that the F-35 has a very decent thrust/weight ratio, more lifting surface than people might think, and most importantly, its sensor, communications and mission equipment suite is extremely good. It's certainly not as good an out and out air combat machine as the F-22 - but the laws of physics get in the way there. All the reports from the pilots flying it tell us that it's a very potent air combat machine. But it's not an F-16, because it wasn't designed that way.
As for twin versus single engine (the issue also mentioned by Orac), I would just repeat an important point that I have posted many times on this thread (and I don't mind doing so again in the least). The genesis of the F-35 programme was the spectacular failure of a number of US tactical aircraft combat aircraft programmes in the 70s and 80s. They were mostly large, twin engined, twin seat designs. The OSD (the central staff of the US DoD) did a ton of analysis and 'lessons learned' stuff. Their conclusion (and one which I fully understand) was that large twin engined fighter designs will usually be very expensive. Getting a big aircraft to haul itself around the sky at high speeds and high 'g' demands very special structures and very powerful engines. The F-22 is, in my view, the surviving programme from that period. The engines are an earlier (and not much less powerful) variant of the engine fitted to the F-35. The F-22 is large and heavy by any standard - go and look up the figures. And here's the thing - the F-22 came in very late, hugely over cost, and was cut from a 1,000 aircraft programme to the 195 built.
The conclusion the OSD drew was that any future tactical combat aircraft programme simply HAD to be a single seat single engine design - the aim was to keep the size down to something that had a chance of being affordable. The USMC STOVL requirement was deliberately used by the OSD as a 'driver' to make JSF single engine, single seat, as there was (and is) no practical twin engined solution for a STOVL fighter bomber. Of course, anyone is free to say that the OSD was wrong - but that was their decision and that's why the F-35 is the size and shape it is.
As to the single/twin debate - terms like 'mafia' and 'bean counters' aren't always helpful, but I as an engineer who spent some years working with a single engined fighter at sea I understand how strongly pilots can feel about this. I'd just observe that there have been plenty of very successful single engined combat aircraft designs, some of which went to sea. (The A-4 Skyhawk comes to mind). Engines have become far more reliable, as the F-35 programme has shown. The USN was strongly opposed to a single engined solution for JSF, but in the end, they were convinced by some pretty comprehensive research into loss rates and through life costs. (I wasn't party to that information, so I can't vouch for its accuracy).
I hope this stuff helps those reading this thread make some sense of where the F-35 is now. If it doesn't, someone tell me and I'll happily take a break.
Best Regards as ever to all those working hard to keep all our people safe,
Engines
Yes, the F-35 does have higher transonic form drag than the F-22 - but that's an inevitable consequence of the sort of aircraft the customer demanded. The F-22 is a large, long, relatively slim aircraft with shallow weapons bays optimised for AAM carriage. The F-35 isn't, because it can't be. During the redesign in 2004/5, the LM team made strenuous efforts to reduce form drag, which was certainly higher than they had predicted. There were a large number of 'tweaks' made to the Outer Mould Line (OML) in that period.
Whether the F-35 'would never be really good at dogfighting' is not a question I can really answer. What I would observe is that the F-35 has a very decent thrust/weight ratio, more lifting surface than people might think, and most importantly, its sensor, communications and mission equipment suite is extremely good. It's certainly not as good an out and out air combat machine as the F-22 - but the laws of physics get in the way there. All the reports from the pilots flying it tell us that it's a very potent air combat machine. But it's not an F-16, because it wasn't designed that way.
As for twin versus single engine (the issue also mentioned by Orac), I would just repeat an important point that I have posted many times on this thread (and I don't mind doing so again in the least). The genesis of the F-35 programme was the spectacular failure of a number of US tactical aircraft combat aircraft programmes in the 70s and 80s. They were mostly large, twin engined, twin seat designs. The OSD (the central staff of the US DoD) did a ton of analysis and 'lessons learned' stuff. Their conclusion (and one which I fully understand) was that large twin engined fighter designs will usually be very expensive. Getting a big aircraft to haul itself around the sky at high speeds and high 'g' demands very special structures and very powerful engines. The F-22 is, in my view, the surviving programme from that period. The engines are an earlier (and not much less powerful) variant of the engine fitted to the F-35. The F-22 is large and heavy by any standard - go and look up the figures. And here's the thing - the F-22 came in very late, hugely over cost, and was cut from a 1,000 aircraft programme to the 195 built.
The conclusion the OSD drew was that any future tactical combat aircraft programme simply HAD to be a single seat single engine design - the aim was to keep the size down to something that had a chance of being affordable. The USMC STOVL requirement was deliberately used by the OSD as a 'driver' to make JSF single engine, single seat, as there was (and is) no practical twin engined solution for a STOVL fighter bomber. Of course, anyone is free to say that the OSD was wrong - but that was their decision and that's why the F-35 is the size and shape it is.
As to the single/twin debate - terms like 'mafia' and 'bean counters' aren't always helpful, but I as an engineer who spent some years working with a single engined fighter at sea I understand how strongly pilots can feel about this. I'd just observe that there have been plenty of very successful single engined combat aircraft designs, some of which went to sea. (The A-4 Skyhawk comes to mind). Engines have become far more reliable, as the F-35 programme has shown. The USN was strongly opposed to a single engined solution for JSF, but in the end, they were convinced by some pretty comprehensive research into loss rates and through life costs. (I wasn't party to that information, so I can't vouch for its accuracy).
I hope this stuff helps those reading this thread make some sense of where the F-35 is now. If it doesn't, someone tell me and I'll happily take a break.
Best Regards as ever to all those working hard to keep all our people safe,
Engines
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I recall that the principal hold-out on the single-vs.-twin issue was the USN, and much analysis was done to convince them that a single was acceptable. As Engines points out, the STOVL aircraft had to be a single - nobody knows how to make a STOVL fighter that does not crash immediately if it loses an engine in powered lift, so more engines = less safety.
Ironically, however, the F135 ended up being more than twice as heavy and more than twice as expensive as the F414, which delivers a little more than half the thrust. I bet the OSD analysts didn't see that coming. Why this is the case, I'm not sure, but I suspect a combination of a certain cube-square effect in engine design (small engines generally have high T/W), LP turbine and shaft issues associated with the lift fan, and possibly some stealth and cooling features.
Moreover, while you're adding complexity with two engines, you also end up with a nice logical layout for all your system lines, wiring and other accessories, and it's easier to install a weapons bay. On the F-35, everything has to be wrapped around the outside of a four-foot storm drain. The main configuration risk in a twin is gooning up the boat-tail design. Deltas and canards are a good way to avoid that trap.
As for transonic drag: Consider that you have to stuff another storm drain into the fuselage behind the cockpit. Also, you have an aircraft the size of an F/A-18E but <15 feet shorter, mostly because of ship-compatibility issues (the jet was designed to fit on the Invincibles) and with internal weapons. You're going to end up with Rosie O'Donnell rather than Uma Thurman.
Ironically, however, the F135 ended up being more than twice as heavy and more than twice as expensive as the F414, which delivers a little more than half the thrust. I bet the OSD analysts didn't see that coming. Why this is the case, I'm not sure, but I suspect a combination of a certain cube-square effect in engine design (small engines generally have high T/W), LP turbine and shaft issues associated with the lift fan, and possibly some stealth and cooling features.
Moreover, while you're adding complexity with two engines, you also end up with a nice logical layout for all your system lines, wiring and other accessories, and it's easier to install a weapons bay. On the F-35, everything has to be wrapped around the outside of a four-foot storm drain. The main configuration risk in a twin is gooning up the boat-tail design. Deltas and canards are a good way to avoid that trap.
As for transonic drag: Consider that you have to stuff another storm drain into the fuselage behind the cockpit. Also, you have an aircraft the size of an F/A-18E but <15 feet shorter, mostly because of ship-compatibility issues (the jet was designed to fit on the Invincibles) and with internal weapons. You're going to end up with Rosie O'Donnell rather than Uma Thurman.
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George,
You're right on the money about the USN and their attitude to a single engined design. And also right on the mark about the problems with a large single engine and its effect on the structure. However, single engined it was always going to be. To be fair, the F119 has performed tolerably well throughout the development programme. The powered lift system, despite the significant risks involved, has also performed well, in my view.
On the length of the aircraft - I know I've posted this one before but: the F-35B was not required to be compatible with an Invincible class ship except for a requirement to be able to conduct a ski jump takeoff from their runway and ramp. This requirement was left in to drive the ski jump STO capability. The requirement to be compatible with the Invincible class lift was left out of the final iteration of the JORD. In fact, there was a clear statement that the aircraft was not required to be compatible with the Invincible lift and hangar deck layouts. I've got a reasonably clear handle on this as I was the engineer responsible for monitoring how the LM team was handling the various shipboard compatibility requirements. I also had to brief various visiting UK senior officers on how limited the UK's shipboard integration requirements were. There were studies carried out into getting an F-35B down an Invincible lift earlier on in the programme, and I remember seeing a diagram of a scheme for small 'fold down' wing tips on the jet - these were canned well before contract award.
Given the extent of the subsequent airframe redesign in 03/04 to get the weight (and drag) of all three variants back inside the box, its my firm belief that if the guys at LM would have got an advantage from making the aircraft longer, they would have done it in a heartbeat. LM were looking hard at absolutely every option including new tails, revised fuselage layouts and many, many other ideas. I'd suspect that other constraints (LHD/LHA elevators? LHD deck parking?) may have had an effect on length and wingspan.
As LM found out, designing a supersonic, stealthy, STOVL aircraft about the size of an F-4 (hat tip to George K Lee for pointing this out) is a very hard thing indeed. Having an airframe design team whose last completed job was the F-16 didn't help. Ignoring offers of help from the UK also didn't help. Not having a Chief Designer DEFINITELY didn't help. Water under the bridge now, aircraft are deployed on USN LHDs as we speak.
Best Regards as ever to all those who take the kit into harm's way - fly safe, come home safe.
Engines
You're right on the money about the USN and their attitude to a single engined design. And also right on the mark about the problems with a large single engine and its effect on the structure. However, single engined it was always going to be. To be fair, the F119 has performed tolerably well throughout the development programme. The powered lift system, despite the significant risks involved, has also performed well, in my view.
On the length of the aircraft - I know I've posted this one before but: the F-35B was not required to be compatible with an Invincible class ship except for a requirement to be able to conduct a ski jump takeoff from their runway and ramp. This requirement was left in to drive the ski jump STO capability. The requirement to be compatible with the Invincible class lift was left out of the final iteration of the JORD. In fact, there was a clear statement that the aircraft was not required to be compatible with the Invincible lift and hangar deck layouts. I've got a reasonably clear handle on this as I was the engineer responsible for monitoring how the LM team was handling the various shipboard compatibility requirements. I also had to brief various visiting UK senior officers on how limited the UK's shipboard integration requirements were. There were studies carried out into getting an F-35B down an Invincible lift earlier on in the programme, and I remember seeing a diagram of a scheme for small 'fold down' wing tips on the jet - these were canned well before contract award.
Given the extent of the subsequent airframe redesign in 03/04 to get the weight (and drag) of all three variants back inside the box, its my firm belief that if the guys at LM would have got an advantage from making the aircraft longer, they would have done it in a heartbeat. LM were looking hard at absolutely every option including new tails, revised fuselage layouts and many, many other ideas. I'd suspect that other constraints (LHD/LHA elevators? LHD deck parking?) may have had an effect on length and wingspan.
As LM found out, designing a supersonic, stealthy, STOVL aircraft about the size of an F-4 (hat tip to George K Lee for pointing this out) is a very hard thing indeed. Having an airframe design team whose last completed job was the F-16 didn't help. Ignoring offers of help from the UK also didn't help. Not having a Chief Designer DEFINITELY didn't help. Water under the bridge now, aircraft are deployed on USN LHDs as we speak.
Best Regards as ever to all those who take the kit into harm's way - fly safe, come home safe.
Engines
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Whether the Invincible requirement made it into the final JORD was a bit of a moot point: the PWSC configuration was well under way by then, and the rival team was having a difficult time selling the reasons why its PWSC looked very different from the X-32. It's also possible that weight considerations precluded a longer airplane.
I believe that the wing span (A & B) is set by the non-folding wing and the requirement to line up X aircraft side-by-side on the LHA/LHD aft of the island.
Just for larfs, here's an early JSF concept with the UK folding wing. Reminds me of the A6M Zero.
I believe that the wing span (A & B) is set by the non-folding wing and the requirement to line up X aircraft side-by-side on the LHA/LHD aft of the island.
Just for larfs, here's an early JSF concept with the UK folding wing. Reminds me of the A6M Zero.
The conclusion the OSD drew was that any future tactical combat aircraft programme simply HAD to be a single seat single engine design - the aim was to keep the size down to something that had a chance of being affordable.
BTW, in all seriousness, thanks for the insight...
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George,
I think you're right on the money when you link the length of the F-35 to the weight. STOVL aircraft are always seriously weight challenged to meet available thrust (lift), that's why the P1127 was a stubby short span delta. Some things don't change much. Perhaps the OSD's strategy for using STOVL to drive down aircraft size worked a bit.
As an aside, look at the significant reduction in fin size from PWSC and AA-1 to the final production F-35A and B designs - during the weight reduction, LM realised that they had put big fins on the aircraft to meet a 'high sustained AOA' requirement that had been fed into a working group by the USAF. That requirement was nowhere in the JORD, nor was it required to meet the modelled air combat capability requirements. I mention this only to offer a minor counter to the charge of 'gold plating' - but TDR is quite right that the US DoD (and the individual services) have a severe tendency to bang the table and demand stuff that's actually either 'nice to have' or even worse 'we want it like we've done it in the past'. Don't get me wrong - sometimes, this stuff is invaluable, and based on hard won experience. Sometimes, however, it's nothing more than 'tradition'. The trick is telling the difference.
You're also right that the USMC spotting requirement constrained wing span - but to this day I can't be sure which one (weight, spotting) actually drove the final design. Probably both, at various times.
Going back to the thread, if LM wanted to 'leverage' their hard won F-35 experience, I'd expect them to take the F-35 layout, free it from STOVL and commonality, and develop a larger land based single engined fighter-bomber. But hey, I'm a retired engineer with nothing else to do but speculate.
Best Regards as ever to all those working out what the heck they are going to need in 20 years time....
Engines
I think you're right on the money when you link the length of the F-35 to the weight. STOVL aircraft are always seriously weight challenged to meet available thrust (lift), that's why the P1127 was a stubby short span delta. Some things don't change much. Perhaps the OSD's strategy for using STOVL to drive down aircraft size worked a bit.
As an aside, look at the significant reduction in fin size from PWSC and AA-1 to the final production F-35A and B designs - during the weight reduction, LM realised that they had put big fins on the aircraft to meet a 'high sustained AOA' requirement that had been fed into a working group by the USAF. That requirement was nowhere in the JORD, nor was it required to meet the modelled air combat capability requirements. I mention this only to offer a minor counter to the charge of 'gold plating' - but TDR is quite right that the US DoD (and the individual services) have a severe tendency to bang the table and demand stuff that's actually either 'nice to have' or even worse 'we want it like we've done it in the past'. Don't get me wrong - sometimes, this stuff is invaluable, and based on hard won experience. Sometimes, however, it's nothing more than 'tradition'. The trick is telling the difference.
You're also right that the USMC spotting requirement constrained wing span - but to this day I can't be sure which one (weight, spotting) actually drove the final design. Probably both, at various times.
Going back to the thread, if LM wanted to 'leverage' their hard won F-35 experience, I'd expect them to take the F-35 layout, free it from STOVL and commonality, and develop a larger land based single engined fighter-bomber. But hey, I'm a retired engineer with nothing else to do but speculate.
Best Regards as ever to all those working out what the heck they are going to need in 20 years time....
Engines
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When you are free from commonality a great many things will be different. You could design around the new variable-cycle engine, which is clearly the USAF's choice for its next airplane. I suspect that range, speed and magazine depth will be favored over agility and that the survivability concept will be "stealth-plus-XYZ". Indeed, if this is not done, any new airplane won't have the legs for Asia-Pacific, magic engine or not.
In retrospect - the weight reduction effort should have been a Woah! moment, but the extent of the change was kept very much out of the public view and all the attention was on the Middle East.
In retrospect - the weight reduction effort should have been a Woah! moment, but the extent of the change was kept very much out of the public view and all the attention was on the Middle East.
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Indeed. Two F414 engines in the Super Hornet weigh less and cost less, and produce more thrust than a single F135. And the F414 EPE (Enhanced Performance Engine) produces significantly more thrust with no weight gain and (reportedly) no increase in life cycle cost (the EPE includes all the durability improvements of the EDE version.) And it seems that packaging two smaller engines into a tactical jet is easier/better than trying to package one big engine. Two engines allows a lot of stuff to fall more naturally into place. And USAF was never truly interested in affordability. Boeing's funky looking X-32 looked like it did because Boeing's design was optimized for low developmental, fly-away, and life-cycle cost. It was truly designed for mass production. It lost for the simple reason that in the end, performance trumps cost.
Last edited by KenV; 2nd May 2018 at 13:49.
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Ken,
The 'single vs twin engine' arguments will doubtless go on as long as combat aircraft are being designed. I'm sure that there will be both single and twin engined combat aircraft designed in the future. For my part, I think both can work, depending on requirements.
On the X-32, you are absolutely right that the Boeing design was optimised for low life cycle cost - I was very impressed with the briefings I attended on how hard they had worked to design a truly 'affordable' aircraft. However, I do (gently) disagree with you on why it lost. In my (hopefully informed) view, the Boeing design lost because it just didn't work. More specifically, it was not a viable STOVL design. The main reason was physics - using hot gas as a propulsive medium (as the X-32 did) is always going to be less efficient that a lift system that uses (in part) cold gas, as the X-35 showed.
Boeing's plan was to build an exceptionally light weight airframe to overcome their lift performance deficit. Their delta design (which built on the long running STOVL Strike Fighter (SSF) programme for the USMC) was well placed to achieve this, but their attempt to use a thermoplastic wing failed at the early stage - fixing this generated a significant weight penalty, which they never quite got past. They also hit problems with Hot Gas Ingestion (HGI), and their solutions (additional jet curtains, and finally additional jet thrusters for lift) were never deemed to be practical. The addition of the aft tails late in their programme (to deal with controllability problems with the CV variant) was, in my view, the final straw.
Again just my view, but one that was held by many people associated with the JSF programme - Boeing's really strong card was their proposal for mission systems development, integration and test. I heard senior figures say that they wished that they had the chance to award the airframe and lift system to LM, and the mission systems to Boeing. Given the problems LM have experienced since then, I wonder whether that might not have been a better route. However, it's water under the bridge, as I've already said. Marines are now at sea with F-35Bs out of Japan, and I (for one) really wish them safe flying and return home.
Best regards as ever to all those making it work in the real world,
Engines
The 'single vs twin engine' arguments will doubtless go on as long as combat aircraft are being designed. I'm sure that there will be both single and twin engined combat aircraft designed in the future. For my part, I think both can work, depending on requirements.
On the X-32, you are absolutely right that the Boeing design was optimised for low life cycle cost - I was very impressed with the briefings I attended on how hard they had worked to design a truly 'affordable' aircraft. However, I do (gently) disagree with you on why it lost. In my (hopefully informed) view, the Boeing design lost because it just didn't work. More specifically, it was not a viable STOVL design. The main reason was physics - using hot gas as a propulsive medium (as the X-32 did) is always going to be less efficient that a lift system that uses (in part) cold gas, as the X-35 showed.
Boeing's plan was to build an exceptionally light weight airframe to overcome their lift performance deficit. Their delta design (which built on the long running STOVL Strike Fighter (SSF) programme for the USMC) was well placed to achieve this, but their attempt to use a thermoplastic wing failed at the early stage - fixing this generated a significant weight penalty, which they never quite got past. They also hit problems with Hot Gas Ingestion (HGI), and their solutions (additional jet curtains, and finally additional jet thrusters for lift) were never deemed to be practical. The addition of the aft tails late in their programme (to deal with controllability problems with the CV variant) was, in my view, the final straw.
Again just my view, but one that was held by many people associated with the JSF programme - Boeing's really strong card was their proposal for mission systems development, integration and test. I heard senior figures say that they wished that they had the chance to award the airframe and lift system to LM, and the mission systems to Boeing. Given the problems LM have experienced since then, I wonder whether that might not have been a better route. However, it's water under the bridge, as I've already said. Marines are now at sea with F-35Bs out of Japan, and I (for one) really wish them safe flying and return home.
Best regards as ever to all those making it work in the real world,
Engines
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On the X-32, you are absolutely right that the Boeing design was optimised for low life cycle cost - I was very impressed with the briefings I attended on how hard they had worked to design a truly 'affordable' aircraft. However, I do (gently) disagree with you on why it lost. In my (hopefully informed) view, the Boeing design lost because it just didn't work. More specifically, it was not a viable STOVL design. The main reason was physics - using hot gas as a propulsive medium (as the X-32 did) is always going to be less efficient that a lift system that uses (in part) cold gas, as the X-35 showed.
And I agree that the "winner take all" approach was likely a mistake. In the best of all worlds the best result might have been as you suggested: a LM airframe with a Boeing combat system. It's too bad that McDonnell wedded itself early on to a gas coupled lift fan rather that LM's shaft coupled lift fan and thereby lost the first round of down-select. Boeing's combat system was really McDonnell's and McDonnell's ariframe looked very promising except of course for a non compliant STOVL system. On the other hand, had McDonnell won, would USN now have a Super Hornet? Seems unlikely. For that matter, had Boeing won, would USN now have a Super Hornet? Would Boeing really compete with itself? The fact that EVERY Douglas airliner was killed and the entire Douglas manufacturing site bulldozed after Boeing took over probably answers that question. Maybe McDonnell and Boeing both losing JSF was really a win in the long run. Between LM, Boeing, and NGC, we now have three very viable military aircraft designers/manufacturers in the US. And I believe that to be a good thing.
What intrigues me is the major power conflict scenario. When people talk about the Japanese buying a cross bred F-22 / F-35 to "counter Chinese ambitions or threat"....are they serious? Can one ever envisage a situation where Japanese fighters are actually engaging in combat with Chinese fighters over each others teritory? Or the US and Russia in air to air combat....of course not,it will never come to this.
It will either be a minor glitch and be papered over quickly (like the Turkish/Russian incident recently) or both combatants will have lost the political war and pressed the button saying: Armageddon.
Whilst I agree nations should build to handle skirmishes,surely we (the world) are still not spending billions in R and D to counter a front line head on attack in this day and age?
They are deluded if they are.
The world will never need an F35/F22 hybrid - WTF?
It will either be a minor glitch and be papered over quickly (like the Turkish/Russian incident recently) or both combatants will have lost the political war and pressed the button saying: Armageddon.
Whilst I agree nations should build to handle skirmishes,surely we (the world) are still not spending billions in R and D to counter a front line head on attack in this day and age?
They are deluded if they are.
The world will never need an F35/F22 hybrid - WTF?