Lockheed Martin F-35 Lightning II Joint Strike Fighter (JSF)

LMFS said:
The question is, whether it makes sense to rush into that huge investment and take that unnecessary risk for the sake of giving the F-35 an edge it intrinsically lacks due to the airframe design. The obvious temptation for the MIC is, predictably, to throw more money at it and hope that the current US advantage in engine performance allows them to save face, but that would be only more of the usual denial that ends up creating an even bigger trouble for the US air power further down the road. Because it will make current readiness and operational cost problems much worse and because rivals are not so far from having analogous propulsive advances on more dynamically capable platforms that would allow them to practically match a re-engined F-35 even having a less performing engine themselves. US planers should not lose so much sleep over the performance of the F-35 and forget unrealistic global air dominance goals first and foremost, that being done the rest of pieces of the puzzle would fall in place by themselves
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Nope, this makes little sense.

The biggest performance challenge the F-35 is facing is thermal management of the onboard systems, especially in anticipation of Block 4 capabilities, hardly an intrinsic quality of the airframe. Even currently, the F135 is struggling to meet the thermal requirements for the onboard systems at high speed at low altitude, hence a time limit on operations at the lower right of the envelope. The AETP is developed specifically for additional range and greater thermal management capability in anticipation of future Block upgrades especially as the strategic focus shifts to the Pacific. Kinematic improvements is hardly the only factor behind adaptive propulsion, and to argue that it’s about “saving face” over kinematics is frankly a bunch of tripe.
 
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icyplanetnhc (Steve) said:
Nope, this makes little sense.

The biggest performance challenge the F-35 is facing is thermal management of the onboard systems, especially in anticipation of Block 4 capabilities, hardly an intrinsic quality of the airframe. Even currently, the F135 is struggling to meet the thermal requirements for the onboard systems at high speed at low altitude, hence a time limit on operations at the lower right of the envelope. The AETP is developed specifically for additional range and also greater thermal management capability in anticipation of future Block upgrades especially as the strategic focus shifts to the Pacific. Kinematic improvements is hardly the only factor behind adaptive propulsion, and to argue that it’s about “saving face” over kinematics is frankly a bunch of tripe.
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Despite of them not being discussed very actively in the media (unless to justify further expenses), I am well aware of the (airframe related) thermal constraints of the F-35 on top of the kinematic ones Steve, those would call to keep Block 4 demands in line with what an improved F135 and airframe as a whole can support, instead of making the viability of the platform contingent on some revolutionary leap in engine performance. The wrong strategic goals are the problem and the solution to those is not technical.
 
The biggest performance challenge the F-35 is facing is thermal management of the onboard systems
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Are you telling me the F135 doesn't provide enough heat to keep the avionics / electronics from freezing at high altitude ? Or on the contrary, they overheat ?
 
Archibald said:
The biggest performance challenge the F-35 is facing is thermal management of the onboard systems
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Are you telling me the F135 doesn't provide enough heat to keep the avionics / electronics from freezing at high altitude ? Or on the contrary, they overheat ?
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Providing cooling; the jet relies on dumping heat into the engine bypass stream as well as into the outside air via the fuel-air heat exchanger above the right intake (intake on the upper fuselage, opposite of the gun on the F-35A). There's also scoops under the wings but IIRC they're just for cooling the engine bay and don't have proper heat exchangers in their flow.

Currently the F-35 does meet its cooling needs, but with production Lot 17 they're adding new hardware to the ESM suite and those additional amplifiers, etc require additional cooling. I believe some hardware upgrades being made may have reduced cooling requirements, but I wouldn't be surprised if there's restrictions imposed or expanded around having a low fuel state while being in high-Q and/or high throttle flight conditions.

Some of you may remember issues in the past where the jets were having mission systems shut down on the ground during hot-pits or rapid turnarounds as hot ambient temps + high engine / airframe temps + not enough fuel to act as a heat sink forced the jets to shut down non-essential heat-generating systems; one of the ideas tested (and perhaps implemented) back then was painting fuel trucks white (vs green) so that the fuel being put into the jets would be appreciably cooler and bring temperatures back down quicker.
 
Archibald said:
The biggest performance challenge the F-35 is facing is thermal management of the onboard systems
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Are you telling me the F135 doesn't provide enough heat to keep the avionics / electronics from freezing at high altitude ? Or on the contrary, they overheat ?
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As @Dragon029 mentioned, it’s for avionics cooling. One of the benefits of a 3-stream adaptive engine design is that the third bypass stream can greatly increase the thermal management capabilities.

If I remember correctly, at high-Q environments (high speed, low altitude), the F-35 flies with weapon bays open for cooling.
 
icyplanetnhc (Steve) said:
If I remember correctly, at high-Q environments (high speed, low altitude), the F-35 flies with weapon bays open for cooling.
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I think you are confusing the fact that the bay are kept open after landing or lengthy ground roll prior to takeoff for that purpose. Heat management can require secondary systems to be shut off when fuel quantity is low (heat sink). But then, what you are suggesting is unheard.
 
Some of you may remember issues in the past where the jets were having mission systems shut down on the ground during hot-pits or rapid turnarounds as hot ambient temps + high engine / airframe temps + not enough fuel to act as a heat sink forced the jets to shut down non-essential heat-generating systems; one of the ideas tested (and perhaps implemented) back then was painting fuel trucks white (vs green) so that the fuel being put into the jets would be appreciably cooler and bring temperatures back down quicker.
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Can't help thinking about the Nimrod AEW-3 where they grew so desperate, they tried to use the fuel as heat sink for the avionics... which led to very silly consequences on the tank kerosene load and aircraft range.

Luckily the F-35 situation is far, far less serious.
 
TomcatViP said:
While Kelly admitted that the Air Force is chronically short of engines for the F-35 due to parts supply issues, he said great progress has been made in reducing the shortage from as many as 48 F-35s that were grounded “for power modules or some engine issues” to less than 40 aircraft. That is “not a trivial accomplishment,” Kelly said, “because every day, they’re introducing more jets to the system. So, it’s not a small improvement, it’s an exponential improvement, and I expect that trend to continue to zero.”

Getting there, however, required Kelly to “curtail some of our airshow schedule” to make sure “we don’t over-consume our engines for not a good return on our training investment.”

Kelly said he is satisfied with about 200 training hours for F-35 pilots per year, supplemented with simulators, and said that 65 percent aircraft availability is also acceptable, because it can be surged to over 70 percent. He said, the 65 percent figure is “a steady state line” for him.
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www.airforcemag.com

NGAD, New Weapons, E-3 Replacement Among Air Combat Command's Top Priorities, Kelly Says | Air & Space Forces Magazine

Gen. Mark D. Kelly outlined the top priorities for Air Combat Command, with the Next-Generation Air Dominance fighter topping the list.
www.airforcemag.com www.airforcemag.com
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Full interview:

View: https://www.youtube.com/watch?v=8RD78DuUaA8&ab_channel=TheMitchellInstituteforAerospaceStudies
 
The F-135 EEP package delivered to the JPO for assessments meets what the JPO requires as far as propulsion needs to support full block-4 and restore any performance degradation that may (or may not) be a result of these upgrades. It was developed by P&W based on requirements shared by the JPO. The push to get a new prototype engine into the platform comes from the Congress wanting to A) inject competition into the propulsion system, and B ) wanting to provide a near term (as early as FY-24?) EMD path to adaptive engines. Likely a number of years before the NGAD EMD is sanctioned. Raytheon's CEO does have a valid point and so does the JPO. An adaptive engine may only be feasible on the F-35A leaving the EEP as the only option for US and foreign F-35B's and the US F-35C's. Can the AF fully fund two adaptive engine EMD's and can you go from prototype ground testing, to completing an EMD program in 5-7 years (when enhancements will be needed?).

Will the new engine require the same EMD test program that the F135 went through? Will it need the creation of additional depot capacity? Will it need a separate component reliability program to be set up just as one was (and is ongoing) for the F-135? Finally, can you afford to do both (EEP+a brand new adaptive engine) and what other upgrades must be traded away to get to that?

So while he may be pitching for a path that profits his company, these are valid points and point to why P&W is in an advantage when it comes to the path forward. Of course Congress, the USAF, and DOD can completely set aside the ROI argument and just focus on performance but I think they'll try to strike some balance.
 
Re cooling:

The F-35's Power and Thermal Management System (PTMS) integrates the conventional functions of the ECS, emergency power system, engine starting system, and auxiliary power systems into a single, highly integrated system. The system features two primary modes of operation: stand-alone combusted-mode operation and bleed-driven operation when the F135 engine is running. The primary power and cooling enables stand- alone ground maintenance with no required external power and cooling carts.

The PTMS also provides primary power for on-ground engine starting, followed by seamless reconfiguration into bleed-driven operation to support flight operations. The PTMS likewise supports inflight emergencies and automatically reconfigures into combusted-mode operation to support flight control, emergency electrical power, and inflight engine-start assist power.

The PTMS provides 270 VDC and 28 VDC electrical power, as well as forced-air cooling for flight-essential systems. It also provides liquid cooling for aircraft avionics systems and pressurization for the cockpit, fuel system, and other aircraft systems. During flight, waste heat generated by onboard systems is rejected overboard via engine- mounted heat exchangers embedded within the F135 engine fan air duct. This eliminates the weight and volume penalties associated with conventional ram air heat-sink systems.
 
Considering the investment, are they less efficient than the F-22 in this heat exchange regard?
 
TomcatViP said:
I think you are confusing the fact that the bay are kept open after landing or lengthy ground roll prior to takeoff for that purpose. Heat management can require secondary systems to be shut off when fuel quantity is low (heat sink). But then, what you are suggesting is unheard.
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That may be it. I remember that there are certain conditions where the weapon bay doors are open to facilitate avionics cooling.
 
GTX said:
Foo Fighter said:
Considering the investment, are they less efficient than the F-22 in this heat exchange regard?
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More info please?
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Sorry, busy day. I am on about the heat dissipation tech for electronic gear and engine systems. I get that the F-35 is not that large an airframe but a lot is crammed into. If NGAD comes on line as expected I see the F-35 not having quite such a load to bear so might have that extra bit of leeway on cooling, or not.
 
F-22 / F119 does not have fan duct heat exchangers for airframe cooling purposes. It does integrate an independent fuel cooling flow control to move fuel thru the aircraft heat exchangers and the engine oil cooler at a higher rate than the engine fuel burn when needed, returning the excess fuel thru a air cooled heat exchanger (bleed air ejector assisted on the ground) to the fuel tanks. At high power and high altitude cold ambient temperature, the engine fuel burn provides sufficient cooling, at ground idle post flight with low tank levels and high ambient temperatures airframe cooling can be a challenge.

The problem with fan duct heat exchangers is that at high power settings, the pressurized fan discharge air is way too hot to provide any cooling to the airframe systems, so you have to shut this system down and use the high fuel flow for cooling instead. The three stream engines will delay this effect under high bypass conditions since the third stream will be less compressed and therefore cooler, making a third stream mounted heat exchanger more effective over more of the envelope.
 
Spain looking seriously at the F-35 (Navy/AF):

news.yahoo.com

Spain’s military still has eyes for the F-35 despite European fighter push

The Spanish Navy and Air Force are still interested in the American F-35 fighter jet, even though the government is about to join a Franco-German program to develop a new European plane.
news.yahoo.com news.yahoo.com

(perhaps one of the three nations which whom LM recently revealed having some open discussion with).
 
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TomcatViP said:
Spain looking seriously at the F-35 (Navy/AF):

news.yahoo.com

Spain’s military still has eyes for the F-35 despite European fighter push

The Spanish Navy and Air Force are still interested in the American F-35 fighter jet, even though the government is about to join a Franco-German program to develop a new European plane.
news.yahoo.com news.yahoo.com

(perhaps one of the three nations which whom LM recently revealed having some open discussion with).
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No surprise here. As unavoidable as Italian F-35Bs, because AV-8B Harrier: because Garibaldi & Asturias; and because "Juan Carlos" and "Cavour & Trieste". The two navies have had very parallel development since 1980 at least.

Spain dragging its feet for so long, relates to peculiar reasons.

-Retirement (and scrapping) of Asturias for budgetary reasons in 2013, unlike Garibaldi which not only remain in service but will survive as a rocket launch platform.

- Only one Juan Carlos vs Trieste and Cavour: clearly much less money there than on the italian side. Or different priorities. Less urgency for F-35s overall.

- Fact that Spain was never part of the "F-35 coalition" in the early 2000's. Unlike Italy, they seemed to be bothered about being a Typhoon coalition member. :D.

-More seriously: Typhoon probably sucked all money, and F-35 had to wait.

- Also not part of the Spanish air force long term plans, since Typhoon was already there.

- In the end Spain will get F-35s only as a last-ditch option for their Navy: no other way to replace AV-8Bs.

Also Spain armed forces never seemed to be bothered by multiple types. If you think Egypt is "spectacular" in that regard, Spain ain't bad either since the 50's.
They got: Mirage IIIs & Mirage F1s; F-4s, F-5s, and F-104s; then Hornets: then Typhoon. And Harriers for the Armada: first generation AV-8A, then AV-8B to the present day.
 
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Well the F-35 is a reality whereas the European fighter project could end up anywhere after who knows how many years.
 
There is room for both. It will even be better for the FCAS project if, at least, one lairforce get to gain some experience fielding stealth fighters.

It also allows participants to wait longer and refine the design into something truly efficient.
 
TomcatViP said:
There is room for both. It will even be better for the FCAS project if, at least, one lairforce get to gain some experience fielding stealth fighters.

It also allows participants to wait longer and refine the design into something truly efficient.
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Absolutely but fielding stealth fighters now is an immediate need with both Russia and China doing the same and with plans to export. What arrives in 15 years can't help with today.
 
Forest Green said:
TomcatViP said:
There is room for both. It will even be better for the FCAS project if, at least, one lairforce get to gain some experience fielding stealth fighters.

It also allows participants to wait longer and refine the design into something truly efficient.
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Absolutely but fielding stealth fighters now is an immediate need with both Russia and China doing the same and with plans to export. What arrives in 15 years can't help with today.
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I'm quite confident Rafale F4 with a load of Meteors can kick ass of anything presently flying.
Even more the very few Su-57s in existence and a handful of J-20s with the wrong engines.
If only the AdA could procure, a bit more than the present 80-100: the 180 planned, or, even better, the 320 once planned in my youth (1996).
 
TomcatViP said:
There is room for both. It will even be better for the FCAS project if, at least, one lairforce get to gain some experience fielding stealth fighters.

It also allows participants to wait longer and refine the design into something truly efficient.
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There is also the inclusion of Spanish industry into the F-35 lifecycle as a major carrot from Lockheed, the economic benefits from the Hornet replacement program outweigh the actual performance of the fighters themselves.
 
Archibald said:
I'm quite confident Rafale F4 with a load of Meteors can kick ass of anything presently flying.
Even more the very few Su-57s in existence and a handful of J-20s with the wrong engines.
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That's an unknown and probably unlikely in my opinion. I doubt the Russians and Chinese invested decades developing something that's less capable than a 4+ gen plane that's 20 years old and isn't VLO. And F4 isn't presently in service either.
 
You are reasonning backwards... and conveniently ignoring the points I raised.
 
Archibald said:
You are reasonning backwards... and conveniently ignoring the points I raised.
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I'm confused, are you saying a Rafale can or cannot beat Su-57s and J-20s? As regards other aircraft, sure it has a chance, it depends how good each side's EW and radars are.
 
Forest Green said:
Archibald said:
I'm quite confident Rafale F4 with a load of Meteors can kick ass of anything presently flying.
Even more the very few Su-57s in existence and a handful of J-20s with the wrong engines.
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That's an unknown and probably unlikely in my opinion. I doubt the Russians and Chinese invested decades developing something that's less capable than a 4+ gen plane that's 20 years old and isn't VLO. And F4 isn't presently in service either.
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1635583235875.jpeg
 
But can't the F35's problems be solved with digital twins or open systems architecture? Or is it too late?
 
Nope, don’t have secret squirrel clearances, but astute observations on the open source goes a long way.

A spherical sensor bulb will have a largely uniform signal return across most aspects while faceting concentrates those returns into large “spikes” in selective aspects while reducing them across most others. Obviously this property of faceting will diminish as the frequency lowers. A continuous curvature fairing smoothly blended into the fuselage may be able to have the best of both, but thus we haven’t seen IR-transparent glass in large scale production with complex curvatures like that. Anyways, this probably isn’t the thread to discuss this topic.

Edit: LOL, that was quick. Regardless, the point still stands.
 
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and a question on the F-35 in response to steve of a physical feature got deleted but its ok to talk about something similiar to the su-57 thread, why?
 
icyplanetnhc (Steve) said:
TomcatViP said:
I think you are confusing the fact that the bay are kept open after landing or lengthy ground roll prior to takeoff for that purpose. Heat management can require secondary systems to be shut off when fuel quantity is low (heat sink). But then, what you are suggesting is unheard.
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That may be it. I remember that there are certain conditions where the weapon bay doors are open to facilitate avionics cooling.
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I'm going off memory here and a post I made in 2016, but I believe the problem was some avionics system (implied to be a vehicle system, not a mission system) was moved into the weapon bays for greater ease of access for maintenance, etc. The problem however was that the weapon bays are a hot environment due to their proximity to the engine, and temperatures in the bay (when flying fast and low with a warm ambient air temp) were hotter than what at least one component within that avionics system was certified for.

The bay temps have been said to exceed 80C, so if the component was only certified to a standard testing temperature of like 85C it may have been getting exposed to conditions where it's lifespan is unknown. If my memory serves, there was talk about the program office having that component undergo further testing to see whether the certification could be extended (nullifying the risk), or whether it'd have to be replaced or have the restriction permanently imposed.

I don't think it was ever reported what finally happened, but I know DOT&E reports after 2015 never talked about the restriction again, so it might have turned out to be a non-issue, or perhaps they're still flying with the restriction today; I haven't heard any pilots or program officials mention the restriction since then either, but I also haven't seen any directly asked about it.
 

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