Lockheed Martin F-35: News ONLY topic

rooster

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I understand the enthusiasm about the light carrier concept and the mobile basing and new attack vectors that it opens up.
However, we still need to keep in mind the limitations of such a platform. An LHA has just about enough room (10k cuft for armament) and fuel to maintain 'light carrier' ops tempo for a couple of days.
Severe limitations like mobility of the platform itself along with curtailed capability of a 'half airwing' means that you still need to have various support assets attached to it for it to function properly.
Its a force multiplier for full size carriers and many unfriendly nations can't sustain a fight against such a light carrier.
 

sferrin

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From above you get a better feel for the available space, or lack of it.

And this with a diagram of the layout for flight operations with 22 aboard. But one permanently on the starboard lift seems a bit unworkable as does the one on the take off run. So 20 is probably the max. IIRC the forward hangar bay is reduced height.

Actually that layout has seven forward, seven aft, and seven in the hanger...so the aircraft on the elevator might just be notionally one of the seven from the hanger being moved; if you take that one out you have twenty aircraft.

The USN was sufficiently impressed with their first F-35 deployment that they are already talking about growing the squadron to 14 or perhaps embarking two of ten for twenty. Everything I've read about actual deployments seems to indicate that F-35 is a huge leap forward in situational awareness electronically; everyone wants more.
If only they felt that way about the C's on the CVNs. They could easily support two squadrons of 12 aircraft without giving up anything. Two of those, two Super Hornets, a squadron of Growlers, and you're still only at 60 aircraft. Add half a dozen MQ-25s, 4 E-2Ds, 4 CMV-22Bs, 10 helos, and you're at 84.
 

Josh_TN

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Weird thought concerning managing the F-35s on amphibs. Would it be at all possible or practical to take off towards the stern of the ship? This would definitely reduce the lift of the aircraft due to the lack of forward motion, but for a STOVL type with low drag I would imagine it was possible. This would allow for a aircraft parked towards the front of the deck to not have to be repositioned astern. Possible? Practical? Too confusing for deck crews? In any case I admit it really would only be useful for an "alpha strike" scenario where you want to sortie most of the wing at once. Lower launch rates would recomend conventional deck move movement.
 

Dragon029

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It should be possible (unless there's something at the stern that could snag a landing gear), and to some extent has been tested; IIRC during the operational testing aboard the Queen Elizabeth for example they mentioned that they tested vertical landing while facing the stern.

However, I think unless there's an emergency where the ship has lost propulsion / steering, the wind over the deck is in the wrong direction and there's an immediate need to launch fighters, it won't happen, just because the time spent taxiing a jet ~500 feet probably won't be that big of a deal when also factoring in the need to reposition deck crew, etc.

I could be wrong, but I think the circumstances would have to be very niche to make sequential forward-then-aft launches the best course of action.
 

NeilChapman

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I understand the enthusiasm about the light carrier concept and the mobile basing and new attack vectors that it opens up.
However, we still need to keep in mind the limitations of such a platform. An LHA has just about enough room (10k cuft for armament) and fuel to maintain 'light carrier' ops tempo for a couple of days.
Severe limitations like mobility of the platform itself along with curtailed capability of a 'half airwing' means that you still need to have various support assets attached to it for it to function properly.
Its a force multiplier for full size carriers and many unfriendly nations can't sustain a fight against such a light carrier.

It's a nice idea as well if one plan for F-35B's is to have them forward deployed inside the A2AD area. You can bring these jets forward wo endangering a CSG.
 

icyplanetnhc (Steve)

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Relevant excerpt from General Nahom. Full Q&A in the links below.


Air Force Magazine: Let’s do a two-minute elevator speech on the five-year defense program. So we understand that we’re going to bring down the F-35s, we’re investing in NGAD, and we’re paying for nuclear, and so on. But some of that, … like the F-35, we can’t see, where does that go in Year 2, 3, 4, 5? … We’re not asking you to go line item by line item.

Nahom: Yeah, in general, the F-35 is gonna be a big one. Because, as you saw, the number is a little lower than it was last year.

Air Force Magazine: A lot lower.

Nahom: I will say, though, … we have not backed off our investment in the F-35. … When the F-35 was first brought on as a developmental program 20-plus years ago, there was a different threat. And as the threat has evolved, the systems that we need to put on the F-35 have evolved. And there’s a cost there. When you talk about getting to the next block of the F-35, and the systems we need for a peer fight, we are investing quite a bit of money on the F-35, and we intend to get not only that capability, but eventually get the capacity we need too. There are limits though. Would we have bought more F-35s if we had more resources? Yes, absolutely.

The Chief has been very consistent, and going back to [former Chief of Staff Gen. David L. Goldfein] too, we’ve said we seek 72 new fighters a year. And what does 72 new fighters a year do? … Our fighter fleet age continues to rise. When you get to 70-plus fighters, we actually start taking the age down, and we start getting some of these older platforms [out].

I tell you, we never intended for some of these platforms to be in service this long. I mean, there’s no reason F-15Cs—and I grew up in the F-15C—there’s no reason we should still be flying it right now. We should have recapitalized those squadrons with new airframes by now. So we’ve got to get to the numbers.

Now, the threat says we’ve got to get to the [future] capability. In a perfect world, would I like the capability and a lot more F-35s—and [F-15]EXs? Absolutely. But, right now we’ve got to concentrate on making sure we get the F-35 we need. We continue the development, and then we buy as many as we can. And if we can get more, then there’s some goodness there.
 

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The F-35 has radar, infrared, and other sensors that form a picture hundreds of miles into Ukraine and Belarus, gathering information that is displayed on the cockpit screen, shared with allied F-35s on Air Policing missions nearby, and relayed to NATO command centers.

The U.S. government has publicly said it shares intelligence with Ukraine that is helping the country to produce battlefield successes. The 34th Fighter Squadron pilots would not say if the data their aircraft gather on Air Policing missions contributes to that picture, but U.S. Air Forces in Europe confirmed that information collected through a variety of platforms adds up to a common intelligence picture.
[...]
NATO Air Policing is the deterrence measure meant to ensure that boundary in the sky is not crossed.

“When we go up there, it’s not just a Wisconsin dude sitting in a gray aircraft up there,” said Sweeney. “It’s a representative of what NATO’s mission is: to deter, train, and provide readiness.”

Harvey spoke of the “honor” of being the execution arm of the NATO deterrence policy.

“You can see for miles and miles, just with your own eyes up there,” he said.

“You can look out, and you can see Lviv, for example, and it’s just particularly moving, knowing that all is right there,” he added, reflecting on the war and his NATO mission. “It has been, and I pray, will continue to be a purely defensive part.”

 

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With an interesting price breakdown document under excel available here


Remark:
I had no idea that Legion pod was so expensive
 

Dreamfighter

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I would have preferred to see them buy not just more F-35B´s but also some F-35C (or A), which could be fitted with the new adaptive-cycle engine.
And to see the RN add catapults to the Queen Elizabeth carriers. Too bad costs for that went up too much and it was cancelled.
 

rooster

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Well if there is another war (big war) in Europe, the B is a better choice than the C because Britain's runways will be smoked. The performance penalty over the C isn't that much of a difference to matter
 

TomS

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Well if there is another war (big war) in Europe, the B is a better choice than the C because Britain's runways will be smoked. The performance penalty over the C isn't that much of a difference to matter

How? Considering that Russia has failed to close the runways of even the Ukranian Air Force? Barring nukes, it's very hard to see how Russia has the wherewithal to mount an effective offensive counterair campaign that far beyond its borders. And if nukes come in, who cares what version of F-35 you have?
 

Dreamfighter

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Well if there is another war (big war) in Europe, the B is a better choice than the C because Britain's runways will be smoked. The performance penalty over the C isn't that much of a difference to matter

Performance penalty won´t be much of a difference until the C gets equipped with the new engine, which (today) seems not to be possible for the B. The adaptive engine will not only provide lower fuel-consumption and increased range and thrust, but will also offer an important increase in cooling.
 

Forest Green

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The A would surely be the best option. Our carriers have no cat so the C is useless for us. The A can carry a slightly better array of internal weapons and has better range than the B.
 

icyplanetnhc (Steve)

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Some relevant excerpts.

Although the Lockheed Martin F-35A is the only feasible alternative [to the F-15EX] as an F-15C/D replacement in the near term, the Air Force instead aims to slash planned orders for the stealthy, single-engine fighter over the next two years by as many as 34 jets, then ramp up orders after F-15EX procurement is completed in fiscal 2024. The 33-year-old F-15E fleet, meanwhile, emerges from the fighter reshuffling unscathed.

...

Air Force officials are seeking to finance new fighter capabilities such as NGAD and F-35 Block 4 by retiring aircraft in the short term. The strategy has usually been met with resistance by Congress. Indeed, the Air Force’s total aircraft inventory in fiscal 2022 comes out about even with the fiscal 2018 fleet, despite proposals to retire hundreds of aircraft over the five-year period.

At the same time, Kendall has proposed reengining the F-35. The Pratt & Whitney F135 is meeting specifications, but Block 4 electronic upgrades risk overwhelming the power and thermal management system. Pratt designed the 43,000-lb.-thrust engine to provide bleed air from the compressor to cool the onboard electronics. But the Block 3F electronics introduced in 2016 already demand twice the optimal 15 kW of bleed-air offtake. The Block 4 upgrades, which include a new core processor, will require a 47-kW offtake from the compressor.

The Air Force is debating whether to upgrade the F135 or shift to the product of the Advanced Engine Technology Development program. The candidates include the GE Aviation XA100 or Pratt XA101 turbofans, which feature adaptive controls for bypass flow that can offer at least a doubling of cooling capacity compared with the F135.
 
Last edited:

Ronny

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Some relevant excerpts.

Although the Lockheed Martin F-35A is the only feasible alternative [to the F-15EX] as an F-15C/D replacement in the near term, the Air Force instead aims to slash planned orders for the stealthy, single-engine fighter over the next two years by as many as 34 jets, then ramp up orders after F-15EX procurement is completed in fiscal 2024. The 33-year-old F-15E fleet, meanwhile, emerges from the fighter reshuffling unscathed.

...

Air Force officials are seeking to finance new fighter capabilities such as NGAD and F-35 Block 4 by retiring aircraft in the short term. The strategy has usually been met with resistance by Congress. Indeed, the Air Force’s total aircraft inventory in fiscal 2022 comes out about even with the fiscal 2018 fleet, despite proposals to retire hundreds of aircraft over the five-year period.

At the same time, Kendall has proposed reengining the F-35. The Pratt & Whitney F135 is meeting specifications, but Block 4 electronic upgrades risk overwhelming the power and thermal management system. Pratt designed the 43,000-lb.-thrust engine to provide bleed air from the compressor to cool the onboard electronics. But the Block 3F electronics introduced in 2016 already demand twice the optimal 15 kW of bleed-air offtake. The Block 4 upgrades, which include a new core processor, will require a 47-kW offtake from the compressor.

The Air Force is debating whether to upgrade the F135 or shift to the product of the Advanced Engine Technology Development program. The candidates include the GE Aviation XA100 or Pratt XA101 turbofans, which feature adaptive controls for bypass flow that can offer at least a doubling of cooling capacity compared with the F135.
This is kinda interesting.
So basically the optimal cooling from the compressor is 15kW, but it can provide up to 30 kW since block 3F?
 

F119Doctor

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Some relevant excerpts.

Although the Lockheed Martin F-35A is the only feasible alternative [to the F-15EX] as an F-15C/D replacement in the near term, the Air Force instead aims to slash planned orders for the stealthy, single-engine fighter over the next two years by as many as 34 jets, then ramp up orders after F-15EX procurement is completed in fiscal 2024. The 33-year-old F-15E fleet, meanwhile, emerges from the fighter reshuffling unscathed.

...

Air Force officials are seeking to finance new fighter capabilities such as NGAD and F-35 Block 4 by retiring aircraft in the short term. The strategy has usually been met with resistance by Congress. Indeed, the Air Force’s total aircraft inventory in fiscal 2022 comes out about even with the fiscal 2018 fleet, despite proposals to retire hundreds of aircraft over the five-year period.

At the same time, Kendall has proposed reengining the F-35. The Pratt & Whitney F135 is meeting specifications, but Block 4 electronic upgrades risk overwhelming the power and thermal management system. Pratt designed the 43,000-lb.-thrust engine to provide bleed air from the compressor to cool the onboard electronics. But the Block 3F electronics introduced in 2016 already demand twice the optimal 15 kW of bleed-air offtake. The Block 4 upgrades, which include a new core processor, will require a 47-kW offtake from the compressor.

The Air Force is debating whether to upgrade the F135 or shift to the product of the Advanced Engine Technology Development program. The candidates include the GE Aviation XA100 or Pratt XA101 turbofans, which feature adaptive controls for bypass flow that can offer at least a doubling of cooling capacity compared with the F135.
This is kinda interesting.
So basically the optimal cooling from the compressor is 15kW, but it can provide up to 30 kW since block 3F?
Yes, the F135 is supplying 30kW of bleed flow for 3F. However, this requires the engine to run hotter and faster to offset this diversion of core airflow, which reduces hot section life, driving the power module back to depot sooner than planned.
 

Ronny

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Some relevant excerpts.

Although the Lockheed Martin F-35A is the only feasible alternative [to the F-15EX] as an F-15C/D replacement in the near term, the Air Force instead aims to slash planned orders for the stealthy, single-engine fighter over the next two years by as many as 34 jets, then ramp up orders after F-15EX procurement is completed in fiscal 2024. The 33-year-old F-15E fleet, meanwhile, emerges from the fighter reshuffling unscathed.

...

Air Force officials are seeking to finance new fighter capabilities such as NGAD and F-35 Block 4 by retiring aircraft in the short term. The strategy has usually been met with resistance by Congress. Indeed, the Air Force’s total aircraft inventory in fiscal 2022 comes out about even with the fiscal 2018 fleet, despite proposals to retire hundreds of aircraft over the five-year period.

At the same time, Kendall has proposed reengining the F-35. The Pratt & Whitney F135 is meeting specifications, but Block 4 electronic upgrades risk overwhelming the power and thermal management system. Pratt designed the 43,000-lb.-thrust engine to provide bleed air from the compressor to cool the onboard electronics. But the Block 3F electronics introduced in 2016 already demand twice the optimal 15 kW of bleed-air offtake. The Block 4 upgrades, which include a new core processor, will require a 47-kW offtake from the compressor.

The Air Force is debating whether to upgrade the F135 or shift to the product of the Advanced Engine Technology Development program. The candidates include the GE Aviation XA100 or Pratt XA101 turbofans, which feature adaptive controls for bypass flow that can offer at least a doubling of cooling capacity compared with the F135.
This is kinda interesting.
So basically the optimal cooling from the compressor is 15kW, but it can provide up to 30 kW since block 3F?
Yes, the F135 is supplying 30kW of bleed flow for 3F. However, this requires the engine to run hotter and faster to offset this diversion of core airflow, which reduces hot section life, driving the power module back to depot sooner than planned.
Do you have additional source for that or it come from your experience working on these engine?.
Anyway, I find this pretty interesting since F-18E/F intended to provide 15kW liquid cooling for APG-79. Given that APG-81 has a bit more T/R modules than APG-79 (1626 modules vs 1368 modules), I wonder what the cooling requirement for APG-81 would be. Maybe 19-20kW?

1.png
 

Ronny

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I vaguely remember the cooling capacity of F-15E to be around 35-40 kW as well
 

F119Doctor

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Yes, the F135 is supplying 30kW of bleed flow for 3F. However, this requires the engine to run hotter and faster to offset this diversion of core airflow, which reduces hot section life, driving the power module back to depot sooner than planned.
Do you have additional source for that or it come from your experience working on these engine?.
Anyway, I find this pretty interesting since F-18E/F intended to provide 15kW liquid cooling for APG-79. Given that APG-81 has a bit more T/R modules than APG-79 (1626 modules vs 1368 modules), I wonder what the cooling requirement for APG-81 would be. Maybe 19-20kW?

View attachment 677766
39 years as a Customer Support / Field Service Engineer for P&W

Taking bleed air from the core airflow is a double penalty for engine performance. All of the air taken from the compressor has absorbed turbine power to get it pressurized - this lost turbine power has to be offset by pushing more fuel and temperature into the combustor. And this air is no longer available to drive the turbine, which means further fuel and temp increase. And the impact is increased at altitude where air density is lower but the cooling demands remain relatively constant.

This increased bleed flow pushes up the operating temperatures throughout the flight envelope. The engine performance is reduced when against the max operating limits, and the temperatures are increased at all other operating conditions, cumulatively using up available hot section life.
 

Ronny

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Yes, the F135 is supplying 30kW of bleed flow for 3F. However, this requires the engine to run hotter and faster to offset this diversion of core airflow, which reduces hot section life, driving the power module back to depot sooner than planned.
Do you have additional source for that or it come from your experience working on these engine?.
Anyway, I find this pretty interesting since F-18E/F intended to provide 15kW liquid cooling for APG-79. Given that APG-81 has a bit more T/R modules than APG-79 (1626 modules vs 1368 modules), I wonder what the cooling requirement for APG-81 would be. Maybe 19-20kW?

View attachment 677766
39 years as a Customer Support / Field Service Engineer for P&W

Taking bleed air from the core airflow is a double penalty for engine performance. All of the air taken from the compressor has absorbed turbine power to get it pressurized - this lost turbine power has to be offset by pushing more fuel and temperature into the combustor. And this air is no longer available to drive the turbine, which means further fuel and temp increase. And the impact is increased at altitude where air density is lower but the cooling demands remain relatively constant.

This increased bleed flow pushes up the operating temperatures throughout the flight envelope. The engine performance is reduced when against the max operating limits, and the temperatures are increased at all other operating conditions, cumulatively using up available hot section life.
I don't quite get it. How come the air used for cooling is not available to drive the turbine?. Isn't it supposed to pass through the fuel-air heat exchanger then still go into the turbine, just slightly hotter?.
Also if I understand correctly, this method of using engine air seem to generate much higher cooling capacity compared to the traditional ambient air scope right?. The air flow is obviously higher because the engine such air in?.
I recalled the cooling capacity of the big F-15E is only around 35kW, so for the medium size F-35 to have 30 kW cooling from its engine alone seem quite impressive. Then it probably get another 5-10 kW of cooling through the top left side cooling scope for a total of 40kW cooling
D806CC9B-9B1D-4351-A2C5-AFE799975329.jpeg
5595FD5B-1EB0-4B41-8BCA-88EA29540E14.jpeg
 

F119Doctor

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Yes, the F135 is supplying 30kW of bleed flow for 3F. However, this requires the engine to run hotter and faster to offset this diversion of core airflow, which reduces hot section life, driving the power module back to depot sooner than planned.
Do you have additional source for that or it come from your experience working on these engine?.
Anyway, I find this pretty interesting since F-18E/F intended to provide 15kW liquid cooling for APG-79. Given that APG-81 has a bit more T/R modules than APG-79 (1626 modules vs 1368 modules), I wonder what the cooling requirement for APG-81 would be. Maybe 19-20kW?

View attachment 677766
39 years as a Customer Support / Field Service Engineer for P&W

Taking bleed air from the core airflow is a double penalty for engine performance. All of the air taken from the compressor has absorbed turbine power to get it pressurized - this lost turbine power has to be offset by pushing more fuel and temperature into the combustor. And this air is no longer available to drive the turbine, which means further fuel and temp increase. And the impact is increased at altitude where air density is lower but the cooling demands remain relatively constant.

This increased bleed flow pushes up the operating temperatures throughout the flight envelope. The engine performance is reduced when against the max operating limits, and the temperatures are increased at all other operating conditions, cumulatively using up available hot section life.
I don't quite get it. How come the air used for cooling is not available to drive the turbine?. Isn't it supposed to pass through the fuel-air heat exchanger then still go into the turbine, just slightly hotter?.
Also if I understand correctly, this method of using engine air seem to generate much higher cooling capacity compared to the traditional ambient air scope right?. The air flow is obviously higher because the engine such air in?.
I recalled the cooling capacity of the big F-15E is only around 35kW, so for the medium size F-35 to have 30 kW cooling from its engine alone seem quite impressive. Then it probably get another 5-10 kW of cooling through the top left side cooling scope for a total of 40kW cooling
View attachment 677792
View attachment 677793
The F135 has a very sophisticated integration of the engine and airframe cooling systems with the fan duct coolers, IPP airflow, and ECS systems. Bleed air from the high compressor is pre-cooled by cooler fan bypass air before it leaves the engine into the airframe systems. Hot air from airframe systems is routed to other under fan duct heat exchangers to be cooled by fan bypass air under certain operating conditions, but not all. At high power settings, the fan bypass air is well over 400F, making it too hot to cool any ECS air. All of this airflow out and into the fan duct coolers is controlled by the ECS system with multiple valves to ensure cooling is achieved.

But the point missed is that air bled from the compressor at high pressure leaves the engine, that pressure being used by various IPP/ECS components to make cooling happen in the airframe. After that, the bleed air is at low pressure and cannot rejoin the engine high pressure core flow, and is exhausted overboard, lost to cause of making thrust.
 

Ronny

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I don't quite get it. How come the air used for cooling is not available to drive the turbine?. Isn't it supposed to pass through the fuel-air heat exchanger then still go into the turbine, just slightly hotter?.
Also if I understand correctly, this method of using engine air seem to generate much higher cooling capacity compared to the traditional ambient air scope right?. The air flow is obviously higher because the engine such air in?.
I recalled the cooling capacity of the big F-15E is only around 35kW, so for the medium size F-35 to have 30 kW cooling from its engine alone seem quite impressive. Then it probably get another 5-10 kW of cooling through the top left side cooling scope for a total of 40kW cooling
View attachment 677792
View attachment 677793
The F135 has a very sophisticated integration of the engine and airframe cooling systems with the fan duct coolers, IPP airflow, and ECS systems. Bleed air from the high compressor is pre-cooled by cooler fan bypass air before it leaves the engine into the airframe systems. Hot air from airframe systems is routed to other under fan duct heat exchangers to be cooled by fan bypass air under certain operating conditions, but not all. At high power settings, the fan bypass air is well over 400F, making it too hot to cool any ECS air. All of this airflow out and into the fan duct coolers is controlled by the ECS system with multiple valves to ensure cooling is achieved.

But the point missed is that air bled from the compressor at high pressure leaves the engine, that pressure being used by various IPP/ECS components to make cooling happen in the airframe. After that, the bleed air is at low pressure and cannot rejoin the engine high pressure core flow, and is exhausted overboard, lost to cause of making thrust.
Wait a second, so if I understand you correctly, not only the air from the low pressure stage of the engine (the fan stage) is used for the cooling of the aircraft. But also the air from the high pressure compressor (the core) is used for cooling?. Isn't that a bit counter productive?. And why don't they use the fuel to take heat from the avionic/airframe, then flow the fuel into the heat exchanger for cooling (you know like a computer cooler). Isn't that a lot more efficient since liquid conduct heat much better? what the point of taking air from the engine into the airframe and not the other way around aka pumping fuel over hot stuff then into the heat exchanger inside the cool section of the engine
Slide1.JPG

Another thing, I thought that only the vent on top of the body is used for avionic cooling and the belly vents are for engine and airframe cooling? (I vaguely remember reading that on Codeonemagazine)
But from what you explained earlier, both top side and belly side vents can be used for both function: avionic cooling and airframe cooling?

F-35 top vents.png
F-35 bottom vents.PNG
 

Ronny

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Nevertheless, I still think F-35 cooling capacity is pretty insane if it can get 30 kW from the engine integrated fuel air heat exchanger alone. With an additional 5-10 kW cooling from the top body vents, it seem pretty competitive even when compare to something like F-15EX
1.PNG
 

rooster

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I don't quite get it. How come the air used for cooling is not available to drive the turbine?. Isn't it supposed to pass through the fuel-air heat exchanger then still go into the turbine, just slightly hotter?.
Also if I understand correctly, this method of using engine air seem to generate much higher cooling capacity compared to the traditional ambient air scope right?. The air flow is obviously higher because the engine such air in?.
I recalled the cooling capacity of the big F-15E is only around 35kW, so for the medium size F-35 to have 30 kW cooling from its engine alone seem quite impressive. Then it probably get another 5-10 kW of cooling through the top left side cooling scope for a total of 40kW cooling
View attachment 677792
View attachment 677793
The F135 has a very sophisticated integration of the engine and airframe cooling systems with the fan duct coolers, IPP airflow, and ECS systems. Bleed air from the high compressor is pre-cooled by cooler fan bypass air before it leaves the engine into the airframe systems. Hot air from airframe systems is routed to other under fan duct heat exchangers to be cooled by fan bypass air under certain operating conditions, but not all. At high power settings, the fan bypass air is well over 400F, making it too hot to cool any ECS air. All of this airflow out and into the fan duct coolers is controlled by the ECS system with multiple valves to ensure cooling is achieved.

But the point missed is that air bled from the compressor at high pressure leaves the engine, that pressure being used by various IPP/ECS components to make cooling happen in the airframe. After that, the bleed air is at low pressure and cannot rejoin the engine high pressure core flow, and is exhausted overboard, lost to cause of making thrust.
Wait a second, so if I understand you correctly, not only the air from the low pressure stage of the engine (the fan stage) is used for the cooling of the aircraft. But also the air from the high pressure compressor (the core) is used for cooling?. Isn't that a bit counter productive?. And why don't they use the fuel to take heat from the avionic/airframe, then flow the fuel into the heat exchanger for cooling (you know like a computer cooler). Isn't that a lot more efficient since liquid conduct heat much better? what the point of taking air from the engine into the airframe and not the other way around aka pumping fuel over hot stuff then into the heat exchanger inside the cool section of the engine
View attachment 677804

Another thing, I thought that only the vent on top of the body is used for avionic cooling and the belly vents are for engine and airframe cooling? (I vaguely remember reading that on Codeonemagazine)
But from what you explained earlier, both top side and belly side vents can be used for both function: avionic cooling and airframe cooling?

View attachment 677805
View attachment 677806
Roger on the vents cooling function. What ever happened to the heat issues with the two weapons bays?
 

Vanessa1402

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Yes, the F135 is supplying 30kW of bleed flow for 3F. However, this requires the engine to run hotter and faster to offset this diversion of core airflow, which reduces hot section life, driving the power module back to depot sooner than planned.
Do you have additional source for that or it come from your experience working on these engine?.
Anyway, I find this pretty interesting since F-18E/F intended to provide 15kW liquid cooling for APG-79. Given that APG-81 has a bit more T/R modules than APG-79 (1626 modules vs 1368 modules), I wonder what the cooling requirement for APG-81 would be. Maybe 19-20kW?

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39 years as a Customer Support / Field Service Engineer for P&W

Taking bleed air from the core airflow is a double penalty for engine performance. All of the air taken from the compressor has absorbed turbine power to get it pressurized - this lost turbine power has to be offset by pushing more fuel and temperature into the combustor. And this air is no longer available to drive the turbine, which means further fuel and temp increase. And the impact is increased at altitude where air density is lower but the cooling demands remain relatively constant.

This increased bleed flow pushes up the operating temperatures throughout the flight envelope. The engine performance is reduced when against the max operating limits, and the temperatures are increased at all other operating conditions, cumulatively using up available hot section life.
I don't quite get it. How come the air used for cooling is not available to drive the turbine?. Isn't it supposed to pass through the fuel-air heat exchanger then still go into the turbine, just slightly hotter?.
Also if I understand correctly, this method of using engine air seem to generate much higher cooling capacity compared to the traditional ambient air scope right?. The air flow is obviously higher because the engine such air in?.
I recalled the cooling capacity of the big F-15E is only around 35kW, so for the medium size F-35 to have 30 kW cooling from its engine alone seem quite impressive. Then it probably get another 5-10 kW of cooling through the top left side cooling scope for a total of 40kW cooling
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The F135 has a very sophisticated integration of the engine and airframe cooling systems with the fan duct coolers, IPP airflow, and ECS systems. Bleed air from the high compressor is pre-cooled by cooler fan bypass air before it leaves the engine into the airframe systems. Hot air from airframe systems is routed to other under fan duct heat exchangers to be cooled by fan bypass air under certain operating conditions, but not all. At high power settings, the fan bypass air is well over 400F, making it too hot to cool any ECS air. All of this airflow out and into the fan duct coolers is controlled by the ECS system with multiple valves to ensure cooling is achieved.

But the point missed is that air bled from the compressor at high pressure leaves the engine, that pressure being used by various IPP/ECS components to make cooling happen in the airframe. After that, the bleed air is at low pressure and cannot rejoin the engine high pressure core flow, and is exhausted overboard, lost to cause of making thrust.
sorry for my dumb question but what is bleed air and how is it different from ram air and bypass air?
 

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sorry for my dumb question but what is bleed air and how is it different from ram air and bypass air?
Ram Air - outside air brought onboard the airframe using forward facing scoops

Bypass Air - On a turbofan engine, pressurized fan discharge air that bypasses around the engine core via the bypass ducts and goes directly to the engine exhaust to make thrust

Bleed Air - Pressurized air taken from the engine compressor flow and sent to the airframe for cockpit pressurization and airframe systems heating / cooling. You can have bleed air taken from the back end of the core compressor only (example F-15/F100 13th stage bleed)), from the middle of the compressor (F-16/F100 switches from 13th stage bleed at low power to cooler 7th stage bleed at high power), and/or from fan bypass air (F-16/F100-229 bleeds fan duct flow to an airframe heat exchanger to pre-cool the 7th / 13th bleed air before it enters the ECS system).
 

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The F135 has a very sophisticated integration of the engine and airframe cooling systems with the fan duct coolers, IPP airflow, and ECS systems. Bleed air from the high compressor is pre-cooled by cooler fan bypass air before it leaves the engine into the airframe systems. Hot air from airframe systems is routed to other under fan duct heat exchangers to be cooled by fan bypass air under certain operating conditions, but not all. At high power settings, the fan bypass air is well over 400F, making it too hot to cool any ECS air. All of this airflow out and into the fan duct coolers is controlled by the ECS system with multiple valves to ensure cooling is achieved.

But the point missed is that air bled from the compressor at high pressure leaves the engine, that pressure being used by various IPP/ECS components to make cooling happen in the airframe. After that, the bleed air is at low pressure and cannot rejoin the engine high pressure core flow, and is exhausted overboard, lost to cause of making thrust.
Wait a second, so if I understand you correctly, not only the air from the low pressure stage of the engine (the fan stage) is used for the cooling of the aircraft. But also the air from the high pressure compressor (the core) is used for cooling?. Isn't that a bit counter productive?. And why don't they use the fuel to take heat from the avionic/airframe, then flow the fuel into the heat exchanger for cooling (you know like a computer cooler). Isn't that a lot more efficient since liquid conduct heat much better? what the point of taking air from the engine into the airframe and not the other way around aka pumping fuel over hot stuff then into the heat exchanger inside the cool section of the engine
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Another thing, I thought that only the vent on top of the body is used for avionic cooling and the belly vents are for engine and airframe cooling? (I vaguely remember reading that on Codeonemagazine)
But from what you explained earlier, both top side and belly side vents can be used for both function: avionic cooling and airframe cooling?

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Relative to avionics cooling, yes to all of the above

The F-22 has liquid cooled avionics, where a PAO fluid is circulated through the black boxes to remove heat from the electronics. Other airframes have air cooled avionics where ECS air is circulated to remove the heat. I don't know what the F-35 uses, but probably both. That heat has to flow from high temperature to a low temperature heat sink unless you have something like a heat pump to move the heat to a higher temperature sink.

Fuel is used for multiple cooling functions - engine oil system, airframe hydraulics, avionics cooling. Ultimately, that waste heat is used in the engine when the heated fuel is burned. But there are limits on how hot the fuel can get before it starts breaking down and forming coke deposits inside the fuel passages within the engine. If the fuel gets too hot due to the heat rejection going into it, you have to find another place to cool the fuel, such as a ram air heat exchanger that may not work well on the ground or under high ambient air temperatures. The fuel in the tank is a constantly reducing level as it is consumed, reducing the total fuel heat sink capability later in the flight. And ram air means scoops, which impact RCS signature and airframe drag.

When you run out of fuel cooling capacity, bleed air become the next cooling source. While bleed air can be very hot, it is also high pressure. This pressure can be used to run an air cycle machine, which essentially turns that hot, high pressure air into cool low pressure air that is used for cockpit pressurization and avionics cooling, either directly with air cooling or with a heat exchanger for liquid cooling. The used cooling air is then dumped overboard, taking the heat with it. The F135 fan duct heat exchangers do help pull heat out of the system, making the cooling more effective, and heating the bypass air actually increases engine thrust, at least partially offsetting the aero drag of the heat exchangers.

But, the higher the cooling requirements, the greater the bleed air mass flow requirements, and the bigger the impact on engine operating temperatures and hot section life.
 

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The F-22 has liquid cooled avionics, where a PAO fluid is circulated through the black boxes to remove heat from the electronics. Other airframes have air cooled avionics where ECS air is circulated to remove the heat. I don't know what the F-35 uses, but probably both.
The F-35 uses a combination of air, PAO and fuel as cooling fluids.
 

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The F-22 has liquid cooled avionics, where a PAO fluid is circulated through the black boxes to remove heat from the electronics. Other airframes have air cooled avionics where ECS air is circulated to remove the heat. I don't know what the F-35 uses, but probably both.
The F-35 uses a combination of air, PAO and fuel as cooling fluids.
And in case anyone asks, PAO is Poly Alpha Olifin (spelling?) synthetic fluid that is very stable and a good heat transfer medium.
 

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Well if there is another war (big war) in Europe, the B is a better choice than the C because Britain's runways will be smoked. The performance penalty over the C isn't that much of a difference to matter

How? Considering that Russia has failed to close the runways of even the Ukranian Air Force? Barring nukes, it's very hard to see how Russia has the wherewithal to mount an effective offensive counterair campaign that far beyond its borders. And if nukes come in, who cares what version of F-35 you have?
You're thinking of the wrong war. Think island hopping and you'll understand why the F35B is their choice.
 

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Relative to avionics cooling, yes to all of the above
The F-22 has liquid cooled avionics, where a PAO fluid is circulated through the black boxes to remove heat from the electronics. Other airframes have air cooled avionics where ECS air is circulated to remove the heat.
Do you mean F-22 has no cooling air vents to let air in?.
When you run out of fuel cooling capacity, bleed air become the next cooling source. While bleed air can be very hot, it is also high pressure. This pressure can be used to run an air cycle machine, which essentially turns that hot, high pressure air into cool low pressure air that is used for cockpit pressurization and avionics cooling, either directly with air cooling or with a heat exchanger for liquid cooling.
Pardon my stupidity again but what exactly is air cycle machine and how can it turn the very hot bleed air to cool air?.
 

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Relative to avionics cooling, yes to all of the above
The F-22 has liquid cooled avionics, where a PAO fluid is circulated through the black boxes to remove heat from the electronics. Other airframes have air cooled avionics where ECS air is circulated to remove the heat.
Do you mean F-22 has no cooling air vents to let air in?.
When you run out of fuel cooling capacity, bleed air become the next cooling source. While bleed air can be very hot, it is also high pressure. This pressure can be used to run an air cycle machine, which essentially turns that hot, high pressure air into cool low pressure air that is used for cockpit pressurization and avionics cooling, either directly with air cooling or with a heat exchanger for liquid cooling.
Pardon my stupidity again but what exactly is air cycle machine and how can it turn the very hot bleed air to cool air?.
The F-22 does use fuel for cooling various airframe systems and engine bleed air for ECS pressurization and cooling. It also utilizes inlet boundary layer diverter air as a source for system cooling.

Wikipedia lookup for air cycle machine:
 

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