Will GE’s XA100 adaptive combat engine transform the F35 ?

Max Q · Wed Jun 02, 2021 3:23 am

This new ‘three stream’ engine is designed as a drop in replacement for the F35

It’s planned to provide 45k of thrust, a significant 10% increase over the current engine and 25% better fuel efficiency, in testing however its providing up to 20% more thrust

GE says this will give 30% more range or 50% more loiter time and significant increase in acceleration and combat capability

These new technologies are planned to migrate to the next two engine fighter which would not require so much thrust per engine

This seems like it could be a game changer for the F35A and C versions, apparently it’s not compatible with the B model

744SPX · Wed Jun 02, 2021 2:05 pm

I saw the article as well. Not sure why they are saying 45k as a 10% increase over the F135 (43k) would be 47.3K.

Going from 43k to 45k is hardly worth mentioning. That's even less than the planned F135 upgrade.

As the F135 was shown years ago to be capable of a 50k rating, the XA100 should most certainly be capable of that considering its 15+ years newer.

50k would make a real difference for the C model and give the F-35A a 1:1 thrust to weight ratio with full internal fuel and full internal (6) AMRAAM loadout at takeoff.

JayinKitsap · Wed Jun 02, 2021 5:01 pm

Is this a demonstration program?, I recall that there is only the Pratt engine for the F35 procurement.

Max Q · Wed Jun 02, 2021 8:20 pm

744SPX wrote:
I saw the article as well. Not sure why they are saying 45k as a 10% increase over the F135 (43k) would be 47.3K.

Going from 43k to 45k is hardly worth mentioning. That's even less than the planned F135 upgrade.

As the F135 was shown years ago to be capable of a 50k rating, the XA100 should most certainly be capable of that considering its 15+ years newer.

50k would make a real difference for the C model and give the F-35A a 1:1 thrust to weight ratio with full internal fuel and full internal (6) AMRAAM loadout at takeoff.

Not sure what the baseline was, what seems significant about this GE engine is that it’s exceeding promised thrust margins significantly along with substantial improvements in fuel burn

Agree that this should improve performance dramatically, I wonder how much actually, it should help transonic acceleration which appeared to be a weak point

I wonder if it will boost the F35’s rather anemic top speed, also if this ‘third stream’ may have an affect like a high bypass turbofan in quieting an incredibly noisy aircraft !

Max Q · Wed Jun 02, 2021 8:25 pm

JayinKitsap wrote:
Is this a demonstration program?, I recall that there is only the Pratt engine for the F35 procurement.

It is,

it’s a long term development program of GE’s to provide a higher performance ‘drop in’ replacement engine for the F35A and C models (still not sure why the B model is incompatible) and a longer term project to build a next generation engine for the F22 replacement, the projected thrust and fuel efficiency is way ahead of anything P&W is planning in any upgrades

I’ve barely touched the specifics of the design, it’s quite revolutionary and impressive technology, worth a google

LightningZ71 · Thu Jun 03, 2021 3:10 am

The F-35B requires a rather specific design and spec of PTO from the engine for the lift fan. These engines are significantly different in how they are designed where the PTO would be, and it likely has different power available there. I expect that the B will require its own engine upgrade program, though, arguably, it is the model that would most benefit from an improved engine. It has the most restricted fuel capacity of the three for starters.

texl1649 · Thu Jun 03, 2021 10:18 am

I believe this is the FG article discussed;

https://www.flightglobal.com/fixed-wing ... 31.article

The AETP program is ongoing, and they are building the second XA100 at this time to test later this year. Hopefully it will be funded. Having a choice as between the F100 and F110 worked well for the F-16 and F-15 and kept costs much lower than otherwise would be the case, imho.

tommy1808 · Thu Jun 03, 2021 10:37 am

Max Q wrote:
I wonder if it will boost the F35’s rather anemic top speed,

I do believe the top speed is not thrust limited but by the diverterless inlet efficency dropping of a cliff.

Best regards
Thomas

VSMUT · Thu Jun 03, 2021 4:34 pm

tommy1808 wrote:
Max Q wrote:
I wonder if it will boost the F35’s rather anemic top speed,

I do believe the top speed is not thrust limited but by the diverterless inlet efficency dropping of a cliff.

Best regards
Thomas

Drag increases almost exponentially with speed. You can't overcome poor aerodynamics by just adding more power.

744SPX · Thu Jun 03, 2021 4:54 pm

LightningZ71 wrote:
The F-35B requires a rather specific design and spec of PTO from the engine for the lift fan. These engines are significantly different in how they are designed where the PTO would be, and it likely has different power available there. I expect that the B will require its own engine upgrade program, though, arguably, it is the model that would most benefit from an improved engine. It has the most restricted fuel capacity of the three for starters.

It also has the draggiest, most non-area-ruled airframe of the three thanks to the lift fan housing behind the cockpit.

Max Q · Fri Jun 04, 2021 2:24 am

744SPX wrote:
LightningZ71 wrote:
The F-35B requires a rather specific design and spec of PTO from the engine for the lift fan. These engines are significantly different in how they are designed where the PTO would be, and it likely has different power available there. I expect that the B will require its own engine upgrade program, though, arguably, it is the model that would most benefit from an improved engine. It has the most restricted fuel capacity of the three for starters.

It also has the draggiest, most non-area-ruled airframe of the three thanks to the lift fan housing behind the cockpit.

Good point, all three versions appear very draggy to me, As wide as it is it looks like it should have two engines

I didn’t realize that lift fan housing added that much drag

744SPX · Fri Jun 04, 2021 7:47 pm

Max Q wrote:
744SPX wrote:
LightningZ71 wrote:
The F-35B requires a rather specific design and spec of PTO from the engine for the lift fan. These engines are significantly different in how they are designed where the PTO would be, and it likely has different power available there. I expect that the B will require its own engine upgrade program, though, arguably, it is the model that would most benefit from an improved engine. It has the most restricted fuel capacity of the three for starters.

It also has the draggiest, most non-area-ruled airframe of the three thanks to the lift fan housing behind the cockpit.

Good point, all three versions appear very draggy to me, As wide as it is it looks like it should have two engines

I didn’t realize that lift fan housing added that much drag

Yeah, you can really see it to great effect in the head-on view of the B model compared to the A and C.

LightningZ71 · Fri Jun 04, 2021 8:14 pm

The drag isn't quite as bad as it appears. It looks worse than it is because the design is a lifting body at it's core. I'm not saying that the B doesn't carry a penalty in that area, just that it's not a major one.

texl1649 · Fri Jun 04, 2021 11:04 pm

It’s basically a bunch of oversized integral fuel tanks built around a massive engine and some tiny wings, with a few bomb bays, but also with stealth incorporated from the front aspect. Kind of a modern F-104 on roids if you will.

tomcat · Fri Jun 04, 2021 11:16 pm

texl1649 wrote:
It’s basically a bunch of oversized integral fuel tanks built around a massive engine and some tiny wings, with a few bomb bays, but also with stealth incorporated from the front aspect. Kind of a modern F-104 on roids if you will.

Not willing to argue here but in many respects the F-35 looks to me as the modern incarnation of the F-105. Consider the bomb bay, the look of the air intakes, the fact that it's a fighter but doesn't excel in dogfighting, you name it. The F-35 is just so much more compact, with so much more range, that's impressive.

Max Q · Sat Jun 05, 2021 3:09 am

Good points, otoh the F105 would leave the F35 in the dust

kitplane01 · Sat Jun 05, 2021 6:57 am

Max Q wrote:
744SPX wrote:
I saw the article as well. Not sure why they are saying 45k as a 10% increase over the F135 (43k) would be 47.3K.

Going from 43k to 45k is hardly worth mentioning. That's even less than the planned F135 upgrade.

As the F135 was shown years ago to be capable of a 50k rating, the XA100 should most certainly be capable of that considering its 15+ years newer.

50k would make a real difference for the C model and give the F-35A a 1:1 thrust to weight ratio with full internal fuel and full internal (6) AMRAAM loadout at takeoff.

Not sure what the baseline was, what seems significant about this GE engine is that it’s exceeding promised thrust margins significantly along with substantial improvements in fuel burn

Agree that this should improve performance dramatically, I wonder how much actually, it should help transonic acceleration which appeared to be a weak point

I wonder if it will boost the F35’s rather anemic top speed, also if this ‘third stream’ may have an affect like a high bypass turbofan in quieting an incredibly noisy aircraft !

I believe noise is a function of velocity of exhaust. Modern engines are quieter in large part because the larger bypass ratio reduces the exhaust velocity needed to produce a given thrust.

At max-thrust, the third stream will go through the core, gain maximum velocity, and probably be about as loud as the previous engine at max thrust. It might even be a bit louder because it's generating a higher thrust total. So on takeoff, I would not expect to see much quieting.

At lower thrusts the third stream would avoid the core, exist with a lower velocity, and reduce noise. So while cruising or landing it might be quieter.

It's actually a different engine, not just a modification of the existing engine, so lots of things will be different. It might have a different noise profile for that reason alone.

kitplane01 · Sat Jun 05, 2021 6:58 am

It's too bad this engine won't be available for the F-35B. That's the most payload limited version. A small increase in maximum thrust would generate a large increase in payload. The reduced fuel consumption would also generate an increase in payload.

wingman · Sat Jun 05, 2021 2:55 pm

Max Q wrote:
Good points, otoh the F105 would leave the F35 in the dust

You mean the F35 would fly through the dust of the F105 that didn't know what just blew it up. I think that's the only or primary point of the F35. If a squadron of them end up with just bullets trying to outshoot a squadron of newer Migs or Raffles it probably won't end well.

Max Q · Sat Jun 05, 2021 9:17 pm

wingman wrote:
Max Q wrote:
Good points, otoh the F105 would leave the F35 in the dust

You mean the F35 would fly through the dust of the F105 that didn't know what just blew it up. I think that's the only or primary point of the F35. If a squadron of them end up with just bullets trying to outshoot a squadron of newer Migs or Raffles it probably won't end well.

Remains to be seen, it’s all theoretical at the moment

Max Q · Sat Jun 05, 2021 9:20 pm

kitplane01 wrote:
Max Q wrote:
744SPX wrote:
I saw the article as well. Not sure why they are saying 45k as a 10% increase over the F135 (43k) would be 47.3K.

Going from 43k to 45k is hardly worth mentioning. That's even less than the planned F135 upgrade.

As the F135 was shown years ago to be capable of a 50k rating, the XA100 should most certainly be capable of that considering its 15+ years newer.

50k would make a real difference for the C model and give the F-35A a 1:1 thrust to weight ratio with full internal fuel and full internal (6) AMRAAM loadout at takeoff.

Not sure what the baseline was, what seems significant about this GE engine is that it’s exceeding promised thrust margins significantly along with substantial improvements in fuel burn

Agree that this should improve performance dramatically, I wonder how much actually, it should help transonic acceleration which appeared to be a weak point

I wonder if it will boost the F35’s rather anemic top speed, also if this ‘third stream’ may have an affect like a high bypass turbofan in quieting an incredibly noisy aircraft !

I believe noise is a function of velocity of exhaust. Modern engines are quieter in large part because the larger bypass ratio reduces the exhaust velocity needed to produce a given thrust.

At max-thrust, the third stream will go through the core, gain maximum velocity, and probably be about as loud as the previous engine at max thrust. It might even be a bit louder because it's generating a higher thrust total. So on takeoff, I would not expect to see much quieting.

At lower thrusts the third stream would avoid the core, exist with a lower velocity, and reduce noise. So while cruising or landing it might be quieter.

It's actually a different engine, not just a modification of the existing engine, so lots of things will be different. It might have a different noise profile for that reason alone.

Very insightful

This is such a revolutionary engine that promises such great improvements I wonder if some of this technology could eventually migrate over to civilian
jet transport engines

CRJockey · Sat Jun 05, 2021 10:28 pm

Max Q wrote:
wingman wrote:
Max Q wrote:
Good points, otoh the F105 would leave the F35 in the dust

You mean the F35 would fly through the dust of the F105 that didn't know what just blew it up. I think that's the only or primary point of the F35. If a squadron of them end up with just bullets trying to outshoot a squadron of newer Migs or Raffles it probably won't end well.

Remains to be seen, it’s all theoretical at the moment

What remains to be seen? The superiority of the F35 vs F105? Or the knife fight superiority of a Rafale or MiG?

Max Q · Sun Jun 06, 2021 3:21 am

CRJockey wrote:
Max Q wrote:
wingman wrote:

You mean the F35 would fly through the dust of the F105 that didn't know what just blew it up. I think that's the only or primary point of the F35. If a squadron of them end up with just bullets trying to outshoot a squadron of newer Migs or Raffles it probably won't end well.

Remains to be seen, it’s all theoretical at the moment

What remains to be seen? The superiority of the F35 vs F105? Or the knife fight superiority of a Rafale or MiG?

What remains to be seen is whether the F35 can prevail in an airborne fight against a contemporary

kitplane01 · Sun Jun 06, 2021 6:46 am

Max Q wrote:
kitplane01 wrote:
Max Q wrote:

Not sure what the baseline was, what seems significant about this GE engine is that it’s exceeding promised thrust margins significantly along with substantial improvements in fuel burn

Agree that this should improve performance dramatically, I wonder how much actually, it should help transonic acceleration which appeared to be a weak point

I wonder if it will boost the F35’s rather anemic top speed, also if this ‘third stream’ may have an affect like a high bypass turbofan in quieting an incredibly noisy aircraft !

I believe noise is a function of velocity of exhaust. Modern engines are quieter in large part because the larger bypass ratio reduces the exhaust velocity needed to produce a given thrust.

At max-thrust, the third stream will go through the core, gain maximum velocity, and probably be about as loud as the previous engine at max thrust. It might even be a bit louder because it's generating a higher thrust total. So on takeoff, I would not expect to see much quieting.

At lower thrusts the third stream would avoid the core, exist with a lower velocity, and reduce noise. So while cruising or landing it might be quieter.

It's actually a different engine, not just a modification of the existing engine, so lots of things will be different. It might have a different noise profile for that reason alone.

Very insightful

This is such a revolutionary engine that promises such great improvements I wonder if some of this technology could eventually migrate over to civilian
jet transport engines

The main usefulness of the three stream technologies is that it allows for a high maximum thrust when the third stream is aimed at the core, and an efficient lower thrust mode when the third stream bypasses the core. Think fighter jet able to achieve high speed and cruise efficiently. Modern airliners don't need this functionality as much. They're typically designed almost entirely to optimize cruise fuel consumption.

CRJockey · Sun Jun 06, 2021 7:12 am

Max Q wrote:
CRJockey wrote:
Max Q wrote:

Remains to be seen, it’s all theoretical at the moment

What remains to be seen? The superiority of the F35 vs F105? Or the knife fight superiority of a Rafale or MiG?

What remains to be seen is whether the F35 can prevail in an airborne fight against a contemporary

Awkwardly cautious position I think. But yeah, on technical terms we have yet to see an encounter.

SteelChair · Sun Jun 06, 2021 12:43 pm

You've got to credit GE for trying. They won't give up on getting onto the F35. They keep being denied even though their product is better because politics. I don't know why or how PW has such political clout, but they do.

LightningZ71 · Sun Jun 06, 2021 1:17 pm

Supposedly, P&W is working on a PIP for the F35 engine that’s applicable to the F35B. From what’s been posted here before, it’s a few percent more power and a modest efficiency boost. Combined, those two things make a big difference for the B.

Given the number of nations that use the B, I can see a lot of international support for such an improvement. Just 5% in both categories gives significant improvements in range and payload and makes the VSTOL carriers more effective.

art · Sun Jun 06, 2021 5:29 pm

I wonder if with this engine F-35 could get through transonic to supersonic in level flight and stay there without afterburner being needed.

Max Q · Mon Jun 07, 2021 12:12 am

CRJockey wrote:
Max Q wrote:
CRJockey wrote:

What remains to be seen? The superiority of the F35 vs F105? Or the knife fight superiority of a Rafale or MiG?

What remains to be seen is whether the F35 can prevail in an airborne fight against a contemporary

Awkwardly cautious position I think. But yeah, on technical terms we have yet to see an encounter.

Is there any other way to be cautious ?!

mxaxai · Mon Jun 07, 2021 10:08 pm

VSMUT wrote:

Drag increases almost exponentially with speed. You can't overcome poor aerodynamics by just adding more power.

While drag may play a role, I'm quite sure that the F-35 top speed is limited by the materials and the temperatures they can tolerate. It has so much thrust available, I'd be very surprised if that was the reason to limit it to M1.6. For the B and C, the temperature problems are well documented https://www.defensenews.com/air/2019/06 ... h-coating/

A new engine that would enable supercruise might mitigate some of those issues at low supersonic speeds. Still, aerodynamic heating at high speeds would remain troublesome.

tommy1808 · Wed Jun 09, 2021 8:59 am

mxaxai wrote:
VSMUT wrote:

Drag increases almost exponentially with speed. You can't overcome poor aerodynamics by just adding more power.

While drag may play a role, I'm quite sure that the F-35 top speed is limited by the materials and the temperatures they can tolerate. It has so much thrust available, I'd be very surprised if that was the reason to limit it to M1.6. For the B and C, the temperature problems are well documented https://www.defensenews.com/air/2019/06 ... h-coating/

A new engine that would enable supercruise might mitigate some of those issues at low supersonic speeds. Still, aerodynamic heating at high speeds would remain troublesome.

A new engine won´t change the inlet, and inlets are important for supersonic performance. Take a good old Panavia Tornado, top speed with the ramps moving: Mach 2+, top speed with ramps in-op: Mach 1.3. That is equivalent to a three times drag increase.

best regards
Thomas

VSMUT · Wed Jun 09, 2021 9:30 am

mxaxai wrote:
VSMUT wrote:

Drag increases almost exponentially with speed. You can't overcome poor aerodynamics by just adding more power.

While drag may play a role, I'm quite sure that the F-35 top speed is limited by the materials and the temperatures they can tolerate. It has so much thrust available, I'd be very surprised if that was the reason to limit it to M1.6. For the B and C, the temperature problems are well documented https://www.defensenews.com/air/2019/06 ... h-coating/

A new engine that would enable supercruise might mitigate some of those issues at low supersonic speeds. Still, aerodynamic heating at high speeds would remain troublesome.

The F-35 is a very draggy aircraft. A result of the big internal bomb bay, massive engine and a common airframe that is designed to accommodate the massive lift fan on the F-35B. And as Tommy brings up, the inlets. Drag increases almost exponentially with speed, and you need to overcome the drag. At some point you'd have to double the power to achieve a meaningful improvement. Adding power is not the solution to going faster once you reach a certain point, and everything I've read and seen about the F-35 seems to indicate that it is pretty close to that point.

JetBuddy · Wed Jun 09, 2021 4:57 pm

+30% range and +50% loiter time would be a huge benefit for many F-35 operators. Especially Norway, where the main air base is located at Ørland, which is more than 1000 km away from the border area with Russia, where most interceptions happen. The idea now is to keep at least 4 aircraft at Evenes as a continuation of the QRA mission which is today located at Bodø (which will be closed).

The other side of the coin is that nobody will approve changing the engines of new F-35s. Especially when the F-35 acquisitions have been so politically loaded. I could see it as part of an MLU sometime in the 2030s.

ThePointblank · Wed Jun 09, 2021 11:42 pm

VSMUT wrote:
mxaxai wrote:
VSMUT wrote:

Drag increases almost exponentially with speed. You can't overcome poor aerodynamics by just adding more power.

While drag may play a role, I'm quite sure that the F-35 top speed is limited by the materials and the temperatures they can tolerate. It has so much thrust available, I'd be very surprised if that was the reason to limit it to M1.6. For the B and C, the temperature problems are well documented https://www.defensenews.com/air/2019/06 ... h-coating/

A new engine that would enable supercruise might mitigate some of those issues at low supersonic speeds. Still, aerodynamic heating at high speeds would remain troublesome.

The F-35 is a very draggy aircraft. A result of the big internal bomb bay, massive engine and a common airframe that is designed to accommodate the massive lift fan on the F-35B. And as Tommy brings up, the inlets. Drag increases almost exponentially with speed, and you need to overcome the drag. At some point you'd have to double the power to achieve a meaningful improvement. Adding power is not the solution to going faster once you reach a certain point, and everything I've read and seen about the F-35 seems to indicate that it is pretty close to that point.

Not really; the frontal aspect of a F-35C is about the same as a F/A-18E/F Super Hornet:

https://www.f-16.net/forum/viewtopic.ph ... 2&p=248729

Comparing a F-35A to a Eurofighter or Rafale:

Also, the Super Hornet, Rafale, and Eurofighter all carry their weapons externally; external weapons, fuel tanks and pylons significantly increase drag. Not many fighters out there can claim that they can carry a pair of 2,000lb bombs, enough fuel for a typical strike mission and 2 air to air missiles, and fly at their top rated speed for as long as they have enough fuel to keep going. Every other fighter is subsonic only with anything hanging off of them.

Max Q · Thu Jun 10, 2021 2:49 am

ThePointblank wrote:
VSMUT wrote:
mxaxai wrote:
While drag may play a role, I'm quite sure that the F-35 top speed is limited by the materials and the temperatures they can tolerate. It has so much thrust available, I'd be very surprised if that was the reason to limit it to M1.6. For the B and C, the temperature problems are well documented https://www.defensenews.com/air/2019/06 ... h-coating/

A new engine that would enable supercruise might mitigate some of those issues at low supersonic speeds. Still, aerodynamic heating at high speeds would remain troublesome.

The F-35 is a very draggy aircraft. A result of the big internal bomb bay, massive engine and a common airframe that is designed to accommodate the massive lift fan on the F-35B. And as Tommy brings up, the inlets. Drag increases almost exponentially with speed, and you need to overcome the drag. At some point you'd have to double the power to achieve a meaningful improvement. Adding power is not the solution to going faster once you reach a certain point, and everything I've read and seen about the F-35 seems to indicate that it is pretty close to that point.

Not really; the frontal aspect of a F-35C is about the same as a F/A-18E/F Super Hornet:

https://www.f-16.net/forum/viewtopic.ph ... 2&p=248729

Comparing a F-35A to a Eurofighter or Rafale:

Also, the Super Hornet, Rafale, and Eurofighter all carry their weapons externally; external weapons, fuel tanks and pylons significantly increase drag. Not many fighters out there can claim that they can carry a pair of 2,000lb bombs, enough fuel for a typical strike mission and 2 air to air missiles, and fly at their top rated speed for as long as they have enough fuel to keep going. Every other fighter is subsonic only with anything hanging off of them.

Yes but the F18 has two engines, the F35 has the drag of a two engine aircraft but only has one

Aircraft that carry weapons, fuel etc on external pylons have a big advantage though, if they have to they can get rid of all that drag in an instant by jettisoning it and immediately improve their maneuverability and speed by a quantum leap

The F35 is always carrying that weight and drag with it even if it is internal

ThePointblank · Thu Jun 10, 2021 5:02 am

Max Q wrote:
ThePointblank wrote:
VSMUT wrote:

The F-35 is a very draggy aircraft. A result of the big internal bomb bay, massive engine and a common airframe that is designed to accommodate the massive lift fan on the F-35B. And as Tommy brings up, the inlets. Drag increases almost exponentially with speed, and you need to overcome the drag. At some point you'd have to double the power to achieve a meaningful improvement. Adding power is not the solution to going faster once you reach a certain point, and everything I've read and seen about the F-35 seems to indicate that it is pretty close to that point.

Not really; the frontal aspect of a F-35C is about the same as a F/A-18E/F Super Hornet:

https://www.f-16.net/forum/viewtopic.ph ... 2&p=248729

Comparing a F-35A to a Eurofighter or Rafale:

Also, the Super Hornet, Rafale, and Eurofighter all carry their weapons externally; external weapons, fuel tanks and pylons significantly increase drag. Not many fighters out there can claim that they can carry a pair of 2,000lb bombs, enough fuel for a typical strike mission and 2 air to air missiles, and fly at their top rated speed for as long as they have enough fuel to keep going. Every other fighter is subsonic only with anything hanging off of them.

Yes but the F18 has two engines, the F35 has the drag of a two engine aircraft but only has one

Aircraft that carry weapons, fuel etc on external pylons have a big advantage though, if they have to they can get rid of all that drag in an instant by jettisoning it and immediately improve their maneuverability and speed by a quantum leap

The F35 is always carrying that weight and drag with it even if it is internal

It's very telling that the Super Hornet requires 2 engines to push around an aircraft that weights almost the same as a single engined F-35C. And the F-35C can carry more weapons and fuel.

mxaxai · Thu Jun 10, 2021 8:51 am

ThePointblank wrote:
It's very telling that the Super Hornet requires 2 engines to push around an aircraft that weights almost the same as a single engined F-35C. And the F-35C can carry more weapons and fuel.

So does the F-5. It's the total installed thrust, not the number of engines that matters. The F-18E has 196 kN, the F-35A has 191 kN (both with afterburners). And despite the draggy canted pylons, the F-18E can (theoretically) achieve M1.8.

ThePointblank · Thu Jun 10, 2021 12:38 pm

mxaxai wrote:
ThePointblank wrote:
It's very telling that the Super Hornet requires 2 engines to push around an aircraft that weights almost the same as a single engined F-35C. And the F-35C can carry more weapons and fuel.

So does the F-5. It's the total installed thrust, not the number of engines that matters. The F-18E has 196 kN, the F-35A has 191 kN (both with afterburners). And despite the draggy canted pylons, the F-18E can (theoretically) achieve M1.8.

The F-18E can only reach its top speed clean, with no weapons or external fuel tanks. The F-35 will reach its top speed with a payload.

mxaxai · Thu Jun 10, 2021 1:49 pm

ThePointblank wrote:
mxaxai wrote:
So does the F-5. It's the total installed thrust, not the number of engines that matters. The F-18E has 196 kN, the F-35A has 191 kN (both with afterburners). And despite the draggy canted pylons, the F-18E can (theoretically) achieve M1.8.

The F-18E can only reach its top speed clean, with no weapons or external fuel tanks. The F-35 will reach its top speed with a payload.

Yes, but even a clean F-35 (A, B or C) is not permitted to go past M1.6, and a clean B or C cannot maintain M1.3 due to thermal issues. Hence, since the crosssections of the (clean) F-18E and F-35C seem to have similar size and both aircraft feature approximately the same thrust and empty weight, either the F-35 is significantly draggier or has other reasons (thermal, structural ...) that limit its top speed.

For example, an F-35C can only fly at Mach 1.3 in afterburner for 50 cumulative seconds, meaning that a pilot cannot clock 50 seconds at that speed, slow down for a couple seconds and then speed back up. However, the time requirements reset after the pilot operates at military power — an engine power setting that allows for less speed and thrust than afterburner — for a duration of three minutes.

The F-35B can fly for 80 cumulative seconds at Mach 1.2 or 40 seconds at Mach 1.3 without risking damage.

But for both the C and B models, flying at Mach 1.3 over the specified time limits poses the risk of inducing structural damage to the aircraft’s horizontal stabilizer.

https://www.defensenews.com/air/2019/06 ... h-coating/

SteelChair · Thu Jun 10, 2021 7:03 pm

Didn't the SH versus Tomcat demonstrate that no parameter is more over-rated than top speed? Was the M2.44 top speed of the Tomcat ever tactically useful? What really counts are weapons, electronics, radar, networking, and reliability.

mxaxai · Thu Jun 10, 2021 7:19 pm

SteelChair wrote:
Didn't the SH versus Tomcat demonstrate that no parameter is more over-rated than top speed? Was the M2.44 top speed of the Tomcat ever tactically useful? What really counts are weapons, electronics, radar, networking, and reliability.

True, more thrust would probably be more useful by providing better acceleration rather than an increased top speed. Though the tactical advantage might be small. Looking at legacy fighters like the F-18 and the proposed F414 EPE, many militaries decided that more thrust isn't necessarily worth the cost.

744SPX · Thu Jun 10, 2021 8:20 pm

SteelChair wrote:
Didn't the SH versus Tomcat demonstrate that no parameter is more over-rated than top speed? Was the M2.44 top speed of the Tomcat ever tactically useful? What really counts are weapons, electronics, radar, networking, and reliability.

Actually, the F-14A was capable of mach 2.5; moreso than the F-15 as it could do it in real world conditions. Multiple pilots have attested to this. It also means it could carry a full load of 6 Sparrows and 2 sidewinders at mach 2+. That kind of speed is tactically useful for intercepts and in some cases, out running/out lasting some types of missiles in a tail chase. I'd take speed over stealth any day, as long as that speed is at least an honest mach 2.5. The F-14A with the wing glove vanes could also pull 7.5g at mach 2+. The F-22 and Eurofighter are the only other aircraft that might be able to do that.

Max Q · Fri Jun 11, 2021 2:54 am

A vital capability that hasn’t been mentioned is the most important.

A Navy pilot in an F18 that loses an engine hundreds of miles from the carrier or a land base can return for a safe landing on the other engine

An F35 pilot has no such option

ThePointblank · Fri Jun 11, 2021 6:56 am

Max Q wrote:
A vital capability that hasn’t been mentioned is the most important.

A Navy pilot in an F18 that loses an engine hundreds of miles from the carrier or a land base can return for a safe landing on the other engine

An F35 pilot has no such option

Twin engined fighters are no more reliable than single engined fighters.

In fact, the opposite is true; a twin engined fighter is more likely to go down because of engine related issues; see the USAF's Class A mishap data between the F-15 and F-16 using the F100-PW-229 engine:

https://www.safety.af.mil/Portals/71/do ... PW-229.pdf

https://www.safety.af.mil/Portals/71/do ... PW-229.pdf

meecrob · Fri Jun 11, 2021 11:33 pm

Max Q wrote:
A vital capability that hasn’t been mentioned is the most important.

A Navy pilot in an F18 that loses an engine hundreds of miles from the carrier or a land base can return for a safe landing on the other engine

An F35 pilot has no such option

The Navy and their F-8's and A-7's would like a word....

texl1649 · Sat Jun 12, 2021 12:04 am

We’ve had the tomcat 21 discussion several times on this board. Ultimately, it’s good that a more capable alternative is available for the F-35, imho.

LyleLanley · Sat Jun 12, 2021 12:15 am

meecrob wrote:
The Navy and their F-8's and A-7's would like a word....

They need to get in line behind literally every carrier aircraft before the Tigercat... And the A-1, T-45, and the mighty war Scooter!!!

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