F-15E vs. F-18C

[JB3DG]

48 minutes ago, Temetre said:

Probably also helped that precision guidance allowed you to do more 'standoffy' stuff and could accurately hit targets from high altitudes and speeds. Even tornado was made when guided weapons were still in its very early phase, and you had to come close or fly low for precisition strikes. Desert Storm was IIRC where guided munitions were first time used in massive numbers? Our beloved Maverick became famous there.

But yeh, I know the SE has TFR and can do the missions; even the F-15C turned out a lot more versatile in terms of flight regime than I expected. Just seems strange to take a high altitude fighter and make it do low attack run jobs from a specialized low altitude swept wing bomber. Made me wonder whats the drawbacks, theres gotta be some.

Good point, high flying fighters seems like they can rely on their huge wings flying low with heavier payloads? Guess it might be more draggy, or the engines might not be as optimized for low altitude. Not that it should be that hard to beat TF-30s with upgraded 80s engines.

I guess the trade-off really might just be range for the most part then? Could imagine that especially low flight profile missions have a much shorter radius. For most DCS maps its probably gonna be more than enough though. I actually just flew through a good chunk of Syria in a low level flight F-18 bombing mission (Viggens wouldve been proud). Probably couldve done >1 hour of flight at ~mach 0.7 with 8000lb of bombs and 1x CFT. F-15E should do even more.

Actually, do we know if the F-15E can go supersonic at sea level with reasonable bomb loads? Looks like F-111 was rated up to mach 1.2 at low altitude. Or I guess the question would be "is rated to go supersonic at low altitude with bombs", im sure its capable to do so.

 

No jet, not even the F-111, is going to go over Mach 1 at low alt with anything hanging outside the bomb bay. The F-111 is actually worse in terms of thrust vs drag compared to the F-15E.

Edited May 4, 2023 by JB3DG

[Temetre]

vor 27 Minuten schrieb JB3DG:

No jet, not even the F-111, is going to go over Mach 1 at low alt with anything hanging outside the bomb bay. The F-111 is actually worse in terms of thrust vs drag compared to the F-15E.

Yeah I almost suspected that one.

Though wasnt the Tornado or Viggen designed to for supersonic low strikes with bombs on the outside? I mean, wouldnt otherwise supersonic capabilities be kinda pointless for low flying bombers?

[henshao]

  

1 hour ago, Temetre said:

Probably also helped that precision guidance allowed you to do more 'standoffy' stuff and could accurately hit targets from high altitudes and speeds. Even tornado was made when guided weapons were still in its very early phase, and you had to come close or fly low for precisition strikes. Desert Storm was IIRC where guided munitions were first time used in massive numbers? Our beloved Maverick became famous there.

But yeh, I know the SE has TFR and can do the missions; even the F-15C turned out a lot more versatile in terms of flight regime than I expected. Just seems strange to take a high altitude fighter and make it do low attack run jobs from a specialized low altitude swept wing bomber. Made me wonder whats the drawbacks, theres gotta be some.

Good point, high flying fighters seems like they can rely on their huge wings flying low with heavier payloads? Guess it might be more draggy, or the engines might not be as optimized for low altitude. Not that it should be that hard to beat TF-30s with upgraded 80s engines.

I guess the trade-off really might just be range for the most part then? Could imagine that especially low flight profile missions have a much shorter radius. For most DCS maps its probably gonna be more than enough though. I actually just flew through a good chunk of Syria in a low level flight F-18 bombing mission (Viggens wouldve been proud). Probably couldve done >1 hour of flight at ~mach 0.7 with 8000lb of bombs and 1x CFT. F-15E should do even more.

Actually, do we know if the F-15E can go supersonic at sea level with reasonable bomb loads? Looks like F-111 was rated up to mach 1.2 at low altitude. Or I guess the question would be "is rated to go supersonic at low altitude with bombs", im sure its capable to do so.

 

I think a lot of your conceptualizations are wrong which is leading you in the wrong direction; the f-111 could do mach 2.5+ at altitude it was not some low-altitude-only platform from a design perspective. Even the B-52 was prepared to do terrain-following attack profiles during the cold war, let alone the F-15. Similarly, the F-15 is not some "high altitude fighter" like a Ta-152 it is designed to go to the enemy and kill them at any altitude

Edited May 4, 2023 by henshao

[Temetre]

vor 21 Minuten schrieb henshao:

  I think a lot of your conceptualizations are wrong which is leading you in the wrong direction; the f-111 could do mach 2.5+ at altitude it was not some low-altitude-only platform from a design perspective. Even the B-52 was prepared to do terrain-following attack profiles during the cold war, let alone the F-15. Similarly, the F-15 is not some "high altitude fighter" like a Ta-152 it is designed to go to the enemy and kill them at any altitude

Yup, I think that might well be the case. Its easy to get general misconceptions like that, thats why im asking those question!  

 

My impression is like, a big reason the F-15 is so expensive is because it has to be an effective high altitude fighter? Huge wing, powerful engines+afterburner and lots of fuel, resulting in a big fighter. Good low altitude performance almost comes by itself after that. Like, the F16/F18 being cheap in comparision, partially because they skip extreme requirements like that. 

Of course thats very different from a Mig-25 which is ONLY good for flying very fast in a straight line. Thats trying to keep down an aircrafts complexity by limiting its capabilities. The F-15 is expensive and big in order to expand capability without bigger compromises.

 

Tbh my understanding of F-111 and Tornado is still quite limited. Ive heard of stories of the F-111 flying 2.5 hour missions in low altitude and high subsonic speeds, with quite substantial bomb loads. That is kinda insane, the F-15E probably cant do the same?

Edited May 4, 2023 by Temetre

[henshao]

30 minutes ago, Temetre said:

Yup, I think that might well be the case. Its easy to get general misconceptions like that, thats why im asking those question!  

 

My impression is like, a big reason the F-15 is so expensive is because it has to be an effective high altitude fighter? Huge wing, powerful engines+afterburner and lots of fuel, resulting in a big fighter. Good low altitude performance almost comes by itself after that. Like, the F16/F18 being cheap in comparision, partially because they skip extreme requirements like that. 

Of course thats very different from a Mig-25 which is ONLY good for flying very fast in a straight line. Thats trying to keep down an aircrafts complexity by limiting its capabilities. The F-15 is expensive and big in order to expand capability without bigger compromises.

 

Tbh my understanding of F-111 and Tornado is still quite limited. Ive heard of stories of the F-111 flying 2.5 hour missions in low altitude and high subsonic speeds, with quite substantial bomb loads. That is kinda insane, the F-15E probably cant do the same?

 

If you think the F-15 is complex add swing wings to the equation (there is a reason we are still using Eagles but not Varks and Tomcats)

 

The F-15E carries ~20k lbs of fuel internally which is obviously well shy of the ~34k lbs of internal tankage in an F-111; the F-15E couldn't do everything the F-111 could do, but the same is true in the opposite direction much more drastically. In regards to the Foxbat it holds several records which are yet unassailable, not the least of which is speed over a 100km circuit which involves sustained ~5g turns at greater than mach 2.5. Such an energy maneuverability profile is to this day untouchable by anything which breathes air (that we know about). In fact I would hypothesize you can gauge how much someone knows about air combat by how highly they respect/fear the Mig-31 as a fighter particularly from during-the-cold war/post-soviet perspective

[Temetre]

vor 58 Minuten schrieb henshao:

If you think the F-15 is complex add swing wings to the equation (there is a reason we are still using Eagles but not Varks and Tomcats)

Oh yeah, thats part of what I ment with the "extreme" feature set. 

vor 58 Minuten schrieb henshao:

The F-15E carries ~20k lbs of fuel internally which is obviously well shy of the ~34k lbs of internal tankage in an F-111; the F-15E couldn't do everything the F-111 could do, but the same is true in the opposite direction much more drastically. In regards to the Foxbat it holds several records which are yet unassailable, not the least of which is speed over a 100km circuit which involves sustained ~5g turns at greater than mach 2.5. Such an energy maneuverability profile is to this day untouchable by anything which breathes air (that we know about). In fact I would hypothesize you can gauge how much someone knows about air combat by how highly they respect/fear the Mig-31 as a fighter particularly from during-the-cold war/post-soviet perspective

Tbh the Foxbat partially holds records because its not really a particularly useful plane design, from what I gather? I mean that thing originally had engines from cruise missiles with 150 hour lifespan. Im sure that produced a lot of power, but its not really smart design. Also never used outside of home territory IIRC.

Im not familiar with the Mig-31 though, heard that one made reason of the rushed Mig-25 development. But im a bit skeptical of rumors about soviet/russian superweapons^^

Edited May 4, 2023 by Temetre

[Alpha]

15 hours ago, JB3DG said:

No jet, not even the F-111, is going to go over Mach 1 at low alt with anything hanging outside the bomb bay. 

There´s plenty of jets capable of supersonic lowlevel flight even with (certain) stores attached. For example F-4 with 4xAim9 and 2x Wing Tank could go super on the deck in max AB - other could do it, too.

[Temetre]

vor 3 Stunden schrieb Alpha:

There´s plenty of jets capable of supersonic lowlevel flight even with (certain) stores attached. For example F-4 with 4xAim9 and 2x Wing Tank could go super on the deck in max AB - other could do it, too.

Tbh yeah im a bit confused by that statement. In DCS, Viggen pilots do that stuff reguarly, and im pretty sure the F16 and even F18 can carry light payloads and go supersonic at 200 feet.

And after all, dedicated bomber planes/variants like the Viggen, Tornado and F-111 were rated for supersonic low level flight. I imagine that wouldve been a waste without carrying a payload? I think only the F-111 has an internal bay of those planes.

[GGTharos]

1 hour ago, Temetre said:

Tbh yeah im a bit confused by that statement. In DCS, Viggen pilots do that stuff reguarly, and im pretty sure the F16 and even F18 can carry light payloads and go supersonic at 200 feet.

And after all, dedicated bomber planes/variants like the Viggen, Tornado and F-111 were rated for supersonic low level flight. I imagine that wouldve been a waste without carrying a payload? I think only the F-111 has an internal bay of those planes.

Running around supersonic at sea level gives you an endurance for 5-6 minutes.  Any payload will easily delete the ability to go supersonic at low altitude (just because Viggens in game are able to doesn't make it correct), and most payload cannot be released (again N/A DCS) at supersonic speeds anyway.

[Temetre]

vor 1 Stunde schrieb GGTharos:

Running around supersonic at sea level gives you an endurance for 5-6 minutes. Any payload will easily delete the ability to go supersonic at low altitude (just because Viggens in game are able to doesn't make it correct)

To be frank, that feels a bit like a kneejerk reaction. If that capability exist, then its there, even if you think its not (or dont know if its) ever used.

And im fairly sure some of those capabilities are literally in the requirements of the aircraft and weapons. In fact, even F-18 weapons like the JSOW arent released at supersonic speeds, but specifically rated to be carried during supersonic flight. Also rated up to IMN 0.95 and down to 200 feet from what ive found, tho who knows if the military tested them at supersonic speeds. 

Im sure the F-111 or Tornado got more than 5 minutes of low alt supersonic endurance, and would only use it for temporary dashs through dangerous space anyway, just like most aircraft handle afterburners and supersonic speed. That doesnt mean the weaponry has to be released at supersonic speeds.

Zitat

Any payload will easily delete the ability to go supersonic at low altitude

And that part is just obviously wrong. Especially considering how fast some of those aircraft get with below military dry thrust.

Zitat

and most payload cannot be released (again N/A DCS) at supersonic speeds anyway

Which is irrelevant to the point im making. And im not sure what you mean with "most payloads", considering stuff like MK80 GP bombs isnt exactly niche munitions, and im pretty sure they can be carried and released in supersonic flight. Theres a question if a particular aircraft and mounting hardware is able to handle it, but its not magic.

The record for a 1000lb JDAM drop is 30k feet and mach 1.5, from an F22s internal bay. I dont think an F-16 in DCS can even do that, IIRC it struggled to go supersonic when I tested longer range JDAM lobbing recently.

Edited May 5, 2023 by Temetre

[GGTharos]

3 hours ago, Temetre said:

To be frank, that feels a bit like a kneejerk reaction. If that capability exist, then its there, even if you think its not (or dont know if its) ever used.

Regardless of supersonic or not, using max AB at high speeds massively limits endurance.

3 hours ago, Temetre said:

And im fairly sure some of those capabilities are literally in the requirements of the aircraft and weapons. In fact, even F-18 weapons like the JSOW arent released at supersonic speeds, but specifically rated to be carried during supersonic flight. Also rated up to IMN 0.95 and down to 200 feet from what ive found, tho who knows if the military tested them at supersonic speeds. 

The only thing that matters is what's cleared for those aircraft to do; the rule of thumb is A/G munitions are launched subsonic.

3 hours ago, Temetre said:

Im sure the F-111 or Tornado got more than 5 minutes of low alt supersonic endurance, and would only use it for temporary dashs through dangerous space anyway, just like most aircraft handle afterburners and supersonic speed. That doesnt mean the weaponry has to be released at supersonic speeds.

Pretty sure you can do the math on the duration yourself, the necessary information is out there.  And yes they can do a dash.  Is it going to be supersonic?   Very payload dependent, but with any significant payload and with any maneuvering at all, the answer is likely to be 'no'.  It's not like 600kts is slow, it's just not supersonic.

3 hours ago, Temetre said:

And that part is just obviously wrong. Especially considering how fast some of those aircraft get with below military dry thrust.

... when they're clean.   The F-111 can get to M1.2 on the deck...when clean.  It is literally the maximum speed is can achieve, at least safely so.   Put a bomb load on it and you might not even get to Mach 1 in level flight.   Drag coefficients are not laughing matters, they're serious stuff; increasing the drag index of an aircraft has an immediate and measurable impact on top speed; the F-111 is quite aerodynamic when clean, the F-15E not really, but either way hanging stuff off the wings does bad things to the DI.   

3 hours ago, Temetre said:

Which is irrelevant to the point im making. And im not sure what you mean with "most payloads", considering stuff like MK80 GP bombs isnt exactly niche munitions, and im pretty sure they can be carried and released in supersonic flight. Theres a question if a particular aircraft and mounting hardware is able to handle it, but its not magic.

Most fighter aircraft are only cleared to release iron bombs at subsonic speeds as far as I know.  Supersonic release has been the exception, not the rule.

3 hours ago, Temetre said:

The record for a 1000lb JDAM drop is 30k feet and mach 1.5, from an F22s internal bay. I dont think an F-16 in DCS can even do that, IIRC it struggled to go supersonic when I tested longer range JDAM lobbing recently.

Yeah but it's a Raptor, making it pretty irrelevant since the airflow mechanics of the release itself are different.

[Alpha]

It´s getting a bit much OT here, I think. The (wrong) statement was "they _can´t_ go super with stores", which is just false for a lot of military fast jets. 

 

The question of a tactical use is a very different one. There are cases where a dash "as quick as possible" is not a bad idea and for the Pilot it´s really not that interesting if it´s M1.0+ or M0.999 - he just cares for his situation in relation to a threat. Running into fuel problems later might be the lesser of a problem... Also operating limits (be it speed limits, release limits, G-Limits,...) really are just for when you´re in training / planning to use the jet again. If you need to be fast as there´s a really bad guy in your six you just run with all the speed you can get and don´t care about limits. 

[SinusoidDelta]

On 5/4/2023 at 2:13 PM, henshao said:

If you think the F-15 is complex add swing wings to the equation (there is a reason we are still using Eagles but not Varks and Tomcats)

 

The F-15E carries ~20k lbs of fuel internally which is obviously well shy of the ~34k lbs of internal tankage in an F-111; the F-15E couldn't do everything the F-111 could do, but the same is true in the opposite direction much more drastically. In regards to the Foxbat it holds several records which are yet unassailable, not the least of which is speed over a 100km circuit which involves sustained ~5g turns at greater than mach 2.5. Such an energy maneuverability profile is to this day untouchable by anything which breathes air (that we know about). In fact I would hypothesize you can gauge how much someone knows about air combat by how highly they respect/fear the Mig-31 as a fighter particularly from during-the-cold war/post-soviet perspective

Not to drag this further OT but is there any reliable source for a MiG-25 performing a sustained ~5G turn, at mach 2.5? At one time I recall seeing a V-n diagram indicating a load factor structural limit beyond ~2.5G fully fueled with a max limit of 4.5G. I’m sure more than one foxbat exceeded those numbers, but skeptical one could sustain those load factors at such a high mach. 

Edited May 6, 2023 by SinusoidDelta

[henshao]

5 hours ago, SinusoidDelta said:

Not to drag this further OT but is there any reliable source for a MiG-25 performing a sustained ~5G turn, at mach 2.5? At one time I recall seeing a V-n diagram indicating a load factor structural limit beyond ~2.5G fully fueled with a max limit of 4.5G. I’m sure more than one foxbat exceeded those numbers, but skeptical one could sustain those load factors at such a high mach. 

 

 

https://www.thisdayinaviation.com/25-september-1960/screen-shot-2014-09-25-at-7-49-05/

 

Now pump that up to 1628 mph and run the math (for the Mig-25)

[JB3DG]

On 5/5/2023 at 2:44 PM, Alpha said:

It´s getting a bit much OT here, I think. The (wrong) statement was "they _can´t_ go super with stores", which is just false for a lot of military fast jets. 

 

The question of a tactical use is a very different one. There are cases where a dash "as quick as possible" is not a bad idea and for the Pilot it´s really not that interesting if it´s M1.0+ or M0.999 - he just cares for his situation in relation to a threat. Running into fuel problems later might be the lesser of a problem... Also operating limits (be it speed limits, release limits, G-Limits,...) really are just for when you´re in training / planning to use the jet again. If you need to be fast as there´s a really bad guy in your six you just run with all the speed you can get and don´t care about limits. 

Super at low altitude is the key here. Mach 1.1 at 1000ft is a very different beast to Mach 1.1 at 25-30 000ft. Not only is the speed of sound higher, but the gap between IAS and TAS is considerably smaller because of much greater air density, and as a result, the drag penalty is proportionately greater. You *might* achieve at least Mach 1 with stores and full AB at high altitude. Not going to happen at low altitude. 

 

On 5/4/2023 at 12:41 PM, Temetre said:

Yeah I almost suspected that one.

Though wasnt the Tornado or Viggen designed to for supersonic low strikes with bombs on the outside? I mean, wouldnt otherwise supersonic capabilities be kinda pointless for low flying bombers?

Supersonic capability at all should be thought of rather as a side effect of low altitude requirements design. If you try to reduce drag and increase power to be able to hit 600kts at low altitude, you are probably going to sail through mach at high altitude.

[Alpha]

That´s why I wrote "on the deck". Even the F4 could/can fly supersonic at sea level, with the mentioned 4xAim9 and 2xWing Tanks and internal fuel on any ICAO Standard day with max AB. Plenty of jets can do that (Hornet is one of the Exceptions, if I recall correctly). I don´t know where the myth "no super at low level" comes from, but it´s 100% wrong. If you can get your hands on a -1 check the performance diagram for "level Flight Envelope" - you will be suprised...

 

At high level it´s rather easy to push beyond M1.0 with stores. The F4 will go beyond M1.6 at high Altitude with the above mentioned loadout. 

 

Most of the times I flew above M1.0 the jet was not clean.  

Edited May 8, 2023 by Alpha

[Temetre]

Am 5.5.2023 um 20:44 schrieb Alpha:

It´s getting a bit much OT here, I think. The (wrong) statement was "they _can´t_ go super with stores", which is just false for a lot of military fast jets. 

Yup, thats pretty much what I was asking. Is that really true, cant those things not be done?

Idk why answers kept moving in the direction of military viability, efficiency and how things are done by the books. That wasnt the point.  

vor 2 Stunden schrieb JB3DG:

Supersonic capability at all should be thought of rather as a side effect of low altitude requirements design. If you try to reduce drag and increase power to be able to hit 600kts at low altitude, you are probably going to sail through mach at high altitude.

When you got enough power and aerodynamics in on area, then you can take a lot of capability for granted. Thats why I was originally confused, especially considering what an F16/F18 can do, being much smaller fliers.^^

vor 41 Minuten schrieb Alpha:

(Hornet is one of the Exceptions, if I recall correctly)

I think Ive read about that a long time ago. It wasnt really about a lack of power or drag, and more that it was discovered that the airframe vibrated a lot when going supersonic at low altitude, and it got limited to subsonic because of that.

Not sure if it was Hornet or Super Hornet tho. And if it was more of a peacetime maintenance thing, or actually a restriction with no exceptions.

Edited May 8, 2023 by Temetre

[jubuttib]

On 10/6/2022 at 2:39 PM, Beirut said:

 

Carnage. Mayhem. Victory. 

"Aaah! You smell that? Smells like..." *HURK* *DEAD*

[JB3DG]

On 5/8/2023 at 3:05 AM, Temetre said:

Yup, thats pretty much what I was asking. Is that really true, cant those things not be done?

Idk why answers kept moving in the direction of military viability, efficiency and how things are done by the books. That wasnt the point.  

When you got enough power and aerodynamics in on area, then you can take a lot of capability for granted. Thats why I was originally confused, especially considering what an F16/F18 can do, being much smaller fliers.^^

I think Ive read about that a long time ago. It wasnt really about a lack of power or drag, and more that it was discovered that the airframe vibrated a lot when going supersonic at low altitude, and it got limited to subsonic because of that.

Not sure if it was Hornet or Super Hornet tho. And if it was more of a peacetime maintenance thing, or actually a restriction with no exceptions.

 

Just checked my '93 -1 for the 15E, -229 engines. Max mach at full burner at low altitude is 1.2 at sea level (goes up to 1.3 at 10 000ft) for a clean jet, which is also the structural design limit. Put 12 Mk-82s, LANTIRN, 4 AIM-9s, + CFTs, and it drops to about 1.05 at sea level, 1.2 at 10 000ft, with 1.25 being the CFT design limit at that altitude. In addition, a clean jet level acceleration to mach 1.2 at 10 000ft takes between 26 and 32 seconds depending on temperature deviation. With the above 12 Mk-82 loadout, that jumps up to 64 seconds on a STD-10°C day, and simply won't reach mach 1.2 on a STD+10°C day. More like Mach 1.1.

I don't have performance charts for the F-111F (the most powerful variant), but given that the max AB thrust was only 25000lbf, while the -229 is 29000lbf, plus the 111F is 16000lbs heavier, I don't think it would better the numbers much. At the very least the low level acceleration would be worse than the F-15E, even if the max mach was higher. It is doubtful that a clean F-111F would have gone over Mach 1.3 at full burner at low alt.

For comparison though, I looked up the F-105D and it is also only marginally better at Mach 1.2 at sea level to Mach 1.4 at 10000ft for a clean jet. Performance tanked comparably to the F-15E when loaded.

Even the F-16 doesn't do much better than any of the above jets when clean, and does considerably worse when loaded.

Finally, the F-4E charts with 4 AIM-7s only equals the above numbers, which means that anything else added on is only going to get worse from there.

I can't post the charts, but someone who has them like GGTharos (I assume?) can back me up on this. Technology doesn't get better going back in history. It gets worse.

 

[GGTharos]

Yep, all of the above.   Plus at those altitudes, the engines drink an insane amount of gas at max power.  

[Temetre]

vor 35 Minuten schrieb JB3DG:

Just checked my '93 -1 for the 15E, -229 engines. Max mach at full burner at low altitude is 1.2 at sea level (goes up to 1.3 at 10 000ft) for a clean jet, which is also the structural design limit. Put 12 Mk-82s, LANTIRN, 4 AIM-9s, + CFTs, and it drops to about 1.05 at sea level, 1.2 at 10 000ft, with 1.25 being the CFT design limit at that altitude. In addition, a clean jet level acceleration to mach 1.2 at 10 000ft takes between 26 and 32 seconds depending on temperature deviation. With the above 12 Mk-82 loadout, that jumps up to 64 seconds on a STD-10°C day, and simply won't reach mach 1.2 on a STD+10°C day. More like Mach 1.1.

I don't have performance charts for the F-111F (the most powerful variant), but given that the max AB thrust was only 25000lbf, while the -229 is 29000lbf, plus the 111F is 16000lbs heavier, I don't think it would better the numbers much. At the very least the low level acceleration would be worse than the F-15E, even if the max mach was higher. It is doubtful that a clean F-111F would have gone over Mach 1.3 at full burner at low alt.

For comparison though, I looked up the F-105D and it is also only marginally better at Mach 1.2 at sea level to Mach 1.4 at 10000ft for a clean jet. Performance tanked comparably to the F-15E when loaded.

Even the F-16 doesn't do much better than any of the above jets when clean, and does considerably worse when loaded.

Finally, the F-4E charts with 4 AIM-7s only equals the above numbers, which means that anything else added on is only going to get worse from there.

I can't post the charts, but someone who has them like GGTharos (I assume?) can back me up on this. Technology doesn't get better going back in history. It gets worse.

Thx for putting down some numbers for those two planes! Mach 1.1 with 12x MK-82s doesnt seem that bad. But of course, considering you could likely go 0.9 or so with a fraction of the fuel usage, so not very useful.

Thats more like what I expected. Seems like generally Mach 1.2 is a massive barrier to overcome for planes flying low? Even a clean F-16 in DCS seems to struggle with that IIRC.

vor 10 Minuten schrieb GGTharos:

Yep, all of the above.   Plus at those altitudes, the engines drink an insane amount of gas at max power.  

Of course, gotta go very high for max afterburner to be ever not utterly wasteful.

Edited May 11, 2023 by Temetre

[GGTharos]

It's not 'mach 1.2' ... it's the 'never exceed speed' which is usually between 700 and 800kts, it just happens to be mach 1.2 or so at low altitude.  Exceeding that speed can result in melting canopies, engines, control surfaces being removed from your aircraft upon deflection etc.  Stuff that DCS doesn't model yet.

As for trying to do it with a bunch of payload that isn't AAMs, you could, but acceleration will be slow and fuel consumption will be massive.  It's possible that the munitions aren't even rated for that part of the envelope.  It's possible they weren't even tested at it, and that's not exactly a new thing with the strike eagle.

[mkellytx]

On 5/10/2023 at 11:51 PM, JB3DG said:

Just checked my '93 -1 for the 15E, -229 engines. Max mach at full burner at low altitude is 1.2 at sea level (goes up to 1.3 at 10 000ft) for a clean jet, which is also the structural design limit. Put 12 Mk-82s, LANTIRN, 4 AIM-9s, + CFTs, and it drops to about 1.05 at sea level, 1.2 at 10 000ft, with 1.25 being the CFT design limit at that altitude. In addition, a clean jet level acceleration to mach 1.2 at 10 000ft takes between 26 and 32 seconds depending on temperature deviation. With the above 12 Mk-82 loadout, that jumps up to 64 seconds on a STD-10°C day, and simply won't reach mach 1.2 on a STD+10°C day. More like Mach 1.1.

I don't have performance charts for the F-111F (the most powerful variant), but given that the max AB thrust was only 25000lbf, while the -229 is 29000lbf, plus the 111F is 16000lbs heavier, I don't think it would better the numbers much. At the very least the low level acceleration would be worse than the F-15E, even if the max mach was higher. It is doubtful that a clean F-111F would have gone over Mach 1.3 at full burner at low alt.

For comparison though, I looked up the F-105D and it is also only marginally better at Mach 1.2 at sea level to Mach 1.4 at 10000ft for a clean jet. Performance tanked comparably to the F-15E when loaded.

Even the F-16 doesn't do much better than any of the above jets when clean, and does considerably worse when loaded.

Finally, the F-4E charts with 4 AIM-7s only equals the above numbers, which means that anything else added on is only going to get worse from there.

I can't post the charts, but someone who has them like GGTharos (I assume?) can back me up on this. Technology doesn't get better going back in history. It gets worse.

 

Just checked the 1F-111F-1 limits section, the max Mach at SL is 1.2, up and away the limit is total temperature of 418 degrees F or 2.5 which ever is less.  There’s also a 300 second limit above 308 degrees F total temperature as well as a note that above M2.2 the paint will blister.  Carriage limits vary by wing sweep, but max for any loading of Mk82’s is 0.9 from 45-72 degrees of sweep.  Mk84 airs go up to 1.4 or 700 kts and Mk84’s with conicals only go to 1.3 and 650 kts.  So, the limits very much look to be weapons limitations not drag limitations.  My 1F-111(B)A-1-1 is not accessible at the moment so I can’t get the performance charts at this time.  That said, the F was well known for the capability to exceed limits for Mach and speed at all altitudes.

As for the Vark/Mud Hen drag comparison it isn’t as simple as the Vark weighs more and has slightly less thrust.  The Vark has a much better profile for wave drag than the Mud Hen and the wing loading is much higher, so I wouldn’t be surprised to see it have lower trans/supersonic drag.  Furthermore, as we’ve seen with the Tomcat the TF30’s create more thrust than the F110’s supersonic, given the variable inlets (on both aircraft) and difference of pressure ratios of the TF30 and F100 (higher than the TF30) those trans/supersonic thrust numbers need to come from the -1-1’s not from SL, uninstalled static thrust.  It’s a bit counter intuitive but lower pressure ratio engines with a variable inlets/exhausts will often outperform higher pressure ratio engines.  This BTW is one of the reasons the French went with the lower (compared to the F100) pressure ratio M53 which does pretty good supersonic.

[Ramstein]

I have not read every post in this weird comparison between the two aircraft. Totally different aircraft. F-18 was replacement for the F-14. The F-15, while on the heels of the F-4 Phantom, was meant to replace several aircraft, but mainly as A-A Interceptor, replacement for the F-111 (F-111 was very, very long distances), but the F-15 could not carry some of the larger weapons and much shorter leggs than F-111 (but weapons have evolved with so many long range missiles on so many platforms). But very capable of chasing down and delivering knockouts to other aircraft for long distances. Then they decided to give it some air to ground capabilities. The F-18 is multirole Navy fighter bomber. Totally different. Not even close. IMHO.

[JB3DG]

12 hours ago, mkellytx said:

Just checked the 1F-111F-1 limits section, the max Mach at SL is 1.2, up and away the limit is total temperature of 418 degrees F or 2.5 which ever is less.  There’s also a 300 second limit above 308 degrees F total temperature as well as a note that above M2.2 the paint will blister.  Carriage limits vary by wing sweep, but max for any loading of Mk82’s is 0.9 from 45-72 degrees of sweep.  Mk84 airs go up to 1.4 or 700 kts and Mk84’s with conicals only go to 1.3 and 650 kts.  So, the limits very much look to be weapons limitations not drag limitations.  My 1F-111(B)A-1-1 is not accessible at the moment so I can’t get the performance charts at this time.  That said, the F was well known for the capability to exceed limits for Mach and speed at all altitudes.

As for the Vark/Mud Hen drag comparison it isn’t as simple as the Vark weighs more and has slightly less thrust.  The Vark has a much better profile for wave drag than the Mud Hen and the wing loading is much higher, so I wouldn’t be surprised to see it have lower trans/supersonic drag.  Furthermore, as we’ve seen with the Tomcat the TF30’s create more thrust than the F110’s supersonic, given the variable inlets (on both aircraft) and difference of pressure ratios of the TF30 and F100 (higher than the TF30) those trans/supersonic thrust numbers need to come from the -1-1’s not from SL, uninstalled static thrust.  It’s a bit counter intuitive but lower pressure ratio engines with a variable inlets/exhausts will often outperform higher pressure ratio engines.  This BTW is one of the reasons the French went with the lower (compared to the F100) pressure ratio M53 which does pretty good supersonic.

Yeah I've seen the effects of intake geometry on the T-38A vs the PMP T-38C (dropped max mach from 1.6 to 1.15). The F-15 does have variable inlets and exhausts though, I believe more advanced and capable than the F-111. That said, I would want to see total form drag as well as wave drag numbers. Greater mass means lower acceleration even when in level flight (simple a = F/m) and if the pig has a larger frontal area than the F-15E the total drag is still going to be worse. Combined with lower acceleration means you would have to spend more time in burner to simply get to the same speed which makes it less practical.