F-4E Air to Air Weapons/Capabilities Discussion

[Aussie_Mantis]

A topic expanding off of Air to Air discussion in a Ground Attack related thread.

 

One thing that I've noted in my previous explorations of F-4 vs MiG-21 seems to be that a favoured tactic, contrary to depictions in World of War by Nihongo Entertainment, is to take the F-4E fully vertical against a MiG-21bis into an egg-shaped turn. Apparently the miG-21bis just cannot keep up below 17000, giving the F-4 the advantage. 

In addition, I wonder what the specific differences between AIM-7E and AIM-7E-2 are.

Edited June 11, 2023 by Aussie_Mantis

[Temetre]

Thx, good idea to make a thread about it. Generally seems like everything that could carry and use Sparrows, did so, and most planes got upgraded to carry them if possible. Indicates to me that the weapon was considered quite useful.

I wonder if people underestimate the launch constraint aspect? They have very limited aspect ratios and ranges. Like, if you have to get behind the enemy at 2 miles distsance, then Id think the Sparrow would have a good hit chance as well, even mid-vietnam ones. With an 'all aspect' BVR missile, they probably took all the difficult shots with it.

Even in DCS, with the Aim-120: If you have F-16s or F-15s lobbing Aim-120s at each other, then competent pilots can really manage MARs and pull some serious maneuvers to dodge missiles. That would result in a low PK, but not be indicative of the missile being bad. And holding locks with semi active missiles is way more difficult.

 

Thats not to say there arent issues and quirks with the Sparrow missile, especially early. Same for the sidewinder, eg see how 2017 theres was a report where an Aim-9xgot deterred by a SU-17s flares. Apparently the 'dirty', inconsistently burning flares confused the counter-mechanism of the missile.

Idk, I find this really interesting, because recently ive also learned just how wrong my understanding of the Vietnam air war was, in some regards. 

vor 8 Stunden schrieb Aussie_Mantis:

The 4 second figure previously quoted seems a bit weird. I think they're bringing up the original non-Dogfight Sparrows, since those have a 4 second delay between initial launch/booster ignition and guidance start. AIM-7E-2 and AIM-7F rectify this

Yeah, it would definitely be interesting to hear whats that about? We also had talk about the plane not allowing you to fire the missile when you arent in good enough constraints, so why would there be a 4 second delay where its just a dud? That seems very strange and a massive flaw.

Edited June 11, 2023 by Temetre

[Temetre]

Apparently the R-60 got some all aspect capability in DCS, apparently reported?

[KlarSnow]

The 4 second delay is due to the sparrow needing to settle its speed gate. This is a very real limitation on AIM-7E/E-2/E-3 sparrows due to the analog nature of the missiles. AIM-7F's and beyond do not have this limitation. You can fire the missile before the 4 seconds are up but the chance of it acquiring the target is very low if you do not wait.

This is very clearly laid out in F-4 weapons manuals and checklists.

[Temetre]

vor 33 Minuten schrieb KlarSnow:

The 4 second delay is due to the sparrow needing to settle its speed gate. This is a very real limitation on AIM-7E/E-2/E-3 sparrows due to the analog nature of the missiles. AIM-7F's and beyond do not have this limitation. You can fire the missile before the 4 seconds are up but the chance of it acquiring the target is very low if you do not wait.

This is very clearly laid out in F-4 weapons manuals and checklists.

That helps. The claim before side that the missile has no guidance if you fire airly, and that it applied to the 7M as well.

Also did a short google, I think I found a l link detailing the problem for ACM. Document is on history.navy.mil and declassified, is it okay to link here?

Zitat

c. Comit Time on AIM-7 Missile

Discussion

The 2 second radar settling time and the 1.8 second missile commit time and the 1.4 second launch delay add up to 5.2 seconds of total comit time. This time delay may cause missed opportunity to fire a missile. These times should be reduced if possible.

If this is what youre talking about, then it seems to be a mix of issues with missile, radar and launch delay. Some of the suggested fixes are upgrades to digital systems to speed up the aircrafts systems.

Edited June 11, 2023 by Temetre

[KlarSnow]

That is a very different issue than the speedgate settling time. The speedgate settling includes the 2 seconds for the radar to settle, and 2 more seconds for the missiles speedgate to settle. This is all before you commit the launch. once you commit the launch there will still be a delay from trigger squeeze to missile launch as the missile goes through its launch process.

You cannot make the commit time happen any faster without hardware changes. you can shoot the missile before the speedgate settles if you don't wait for the four seconds, which has a high probability of a ballistic launch that does not guide.

Again the speedgate issue in particular only applies to AIM-7E, E-2, and E-3. F's M's and better all do not have that particular delay or issue. If you have a good lock you can shoot 7F, M, MH, or P immediately. There will still be a commit time and a launch process that will result in the missile taking a second or so after you squeeze the trigger to come off the rail, but you do not have to wait any more time.

Edited June 11, 2023 by KlarSnow

[Temetre]

Btw, do you know if the Aim-9 has a longer delay as well? Wonder how it compares to the Mig-21BIS, that one has a pretty rough delay with heatseekers too.

vor 9 Minuten schrieb KlarSnow:

That is a very different issue than the speedgate settling time. The speedgate settling includes the 2 seconds for the radar to settle, and 2 more seconds for the missiles speedgate to settle. This is all before you commit the launch. once you commit the launch there will still be a delay from trigger squeeze to missile launch as the missile goes through its launch process.

Yeah I probably worded it badly, thats basically what I ment.^^

Aight, so gotta be patient with that thing after getting a lock.

Edited June 11, 2023 by Temetre

[MysteriousHonza]

4 hours ago, Temetre said:

Btw, do you know if the Aim-9 has a longer delay as well? Wonder how it compares to the Mig-21BIS, that one has a pretty rough delay with heatseekers too.

Yeah I probably worded it badly, thats basically what I ment.^^

Aight, so gotta be patient with that thing after getting a lock.

 

It takes approx 0.8 secs for early winders to go through launch sequence. 

[WinterH]

Does anybody here know what's different in the slightly upgraded variant of APQ-120 on DMAS bird btw? Wonder if it makes Sparrow employment any better, or was it just a reliability update etc.

Didn't know 4 secs delay didn't apply to AIM-7F, good to know, and we should be getting F too.

4 hours ago, Temetre said:

Btw, do you know if the Aim-9 has a longer delay as well? Wonder how it compares to the Mig-21BIS, that one has a pretty rough delay with heatseekers too.

I personally don't remember reading about a delay for Sidewinders in the manuals, but been sometime I've checked it last. I wouldn't be super suprised if it is the case, as most of the contemporaries we have in DCS like MiG-21Bis and Mirage F1 have some delay in firing off heat seeking missiles, but at the same time I don't remember it being as dramatic on F-5E, which is also mostly contemporary with the variants we'll get.

[303_Kermit]

6 hours ago, Temetre said:

Thx, good idea to make a thread about it. Generally seems like everything that could carry and use Sparrows, did so, and most planes got upgraded to carry them if possible. Indicates to me that the weapon was considered quite useful.

I wonder if people underestimate the launch constraint aspect? They have very limited aspect ratios and ranges. Like, if you have to get behind the enemy at 2 miles distsance, then Id think the Sparrow would have a good hit chance as well, even mid-vietnam ones. With an 'all aspect' BVR missile, they probably took all the difficult shots with it.

Even in DCS, with the Aim-120: If you have F-16s or F-15s lobbing Aim-120s at each other, then competent pilots can really manage MARs and pull some serious maneuvers to dodge missiles. That would result in a low PK, but not be indicative of the missile being bad. And holding locks with semi active missiles is way more difficult.

 

Thats not to say there arent issues and quirks with the Sparrow missile, especially early. Same for the sidewinder, eg see how 2017 theres was a report where an Aim-9xgot deterred by a SU-17s flares. Apparently the 'dirty', inconsistently burning flares confused the counter-mechanism of the missile.

Idk, I find this really interesting, because recently ive also learned just how wrong my understanding of the Vietnam air war was, in some regards. 

Yeah, it would definitely be interesting to hear whats that about? We also had talk about the plane not allowing you to fire the missile when you arent in good enough constraints, so why would there be a 4 second delay where its just a dud? That seems very strange and a massive flaw.

 

Probably some of you guys are overestimating AiM-7. Their overall efficiency in Vietnam was ~3%. To make it worse AN/APQ-120 had a tendency to loose contact in STT mode.  In fact in Vietnam one field mod of F-4 was very popular. A switch that fixes radar antenna in forward position (Like FLOOD mode in modern planes of '80). That allows AiM-7 to keep track . Pilots called that mode "Boresight"

In Bill Gunston's book most pilots coment's looked like "Shooting missiles is a lot of fun, but pose no threat for PLAF pilots"

About aerial dogfights - before inventing TOP Gun there was a month (August 1967 to be more precise), when USA ( can't recall if USAF or USN) Lost 8 Phantom's II without shooting down a single MiG (any type). It was a consequence of introducing a new PLAF Tactics in low flight lvl flights. Funny fact is, that CIA knew about new tactics and PLAF preparations, but.... considered these news to be ... to important to share it with USAF / USN or USMC, and classified it.

[Temetre]

vor 2 Stunden schrieb MysteriousHonza:

It takes approx 0.8 secs for early winders to go through launch sequence. 

Thx, so pretty similar to F-18 I think. Thats neat, way better than Mig-21BIS  

[Temetre]

vor einer Stunde schrieb 303_Kermit:

Probably some of you guys are overestimating AiM-7. Their overall efficiency in Vietnam was ~3%. To make it worse AN/APQ-120 had a tendency to loose contact in STT mode.  In fact in Vietnam one field mod of F-4 was very popular. A switch that fixes radar antenna in forward position (Like FLOOD mode in modern planes of '80). That allows AiM-7 to keep track . Pilots called that mode "Boresight"

In Bill Gunston's book most pilots coment's looked like "Shooting missiles is a lot of fun, but pose no threat for PLAF pilots"

But in the end A2A duels is like 190 downed migs and 80 downed US planes. And the US losses were mostly from the beginnig, when they made a ton of mistakes.

From what Ive read, one of the important moments where the tides turned was with Operation Bolo, when a bunch of migs got lured into combat with F-4s. But that was actually with F-4Ds, so without even upgraded versions.

From, what ive read, the kill percentage of Aim7s was 9/13% for USAF/USN or so? But thats including all misses, including ones that arent fault of the missile at all. Mind im not saying the Sparrow was a perfect weapon, far from it. But people saying its "no threat" just seems a bit hyperbolic if you look up how air duels actually played out.

vor einer Stunde schrieb 303_Kermit:

About aerial dogfights - before inventing TOP Gun there was a month (August 1967 to be more precise), when USA ( can't recall if USAF or USN) Lost 8 Phantom's II without shooting down a single MiG (any type). It was a consequence of introducing a new PLAF Tactics in low flight lvl flights. Funny fact is, that CIA knew about new tactics and PLAF preparations, but.... considered these news to be ... to important to share it with USAF / USN or USMC, and classified it.

IIRC there was actually something like 50 losses to migs without a single shotdown? Crazy stuff.

But the main issues seems to be training, the USAF had trained for a very different kind of combat.

Edited June 11, 2023 by Temetre

[303_Kermit]

4 hours ago, Temetre said:

its "no threat" just seems a bit hyperbolic if you look up how air duels actually played out.

I quoted a statement of Phantom II Pilot of Vietnam War era. I can find it precisely if you like. I also doubted it. In other book however I red, that Phantom II pilots were not quite liked by other USN pilots and colleagues. If the 2 statements (from 2 different books) are real , or somehow connected - I can't tell. It is however a very interesting story.

Edited June 11, 2023 by 303_Kermit

[Aussie_Mantis]

13 hours ago, KlarSnow said:

The 4 second delay is due to the sparrow needing to settle its speed gate. This is a very real limitation on AIM-7E/E-2/E-3 sparrows due to the analog nature of the missiles. AIM-7F's and beyond do not have this limitation. You can fire the missile before the 4 seconds are up but the chance of it acquiring the target is very low if you do not wait.

This is very clearly laid out in F-4 weapons manuals and checklists.

Oh, the speed gate. I thought they were thinking about 4 seconds after launch, not 4 seconds before launch.

AIM-7Es in the-game-which-will-not-be-named had this weird 3-4 second delay when they were first released that kept them flying straight until they decided to turn on guidance.

Edited June 12, 2023 by Aussie_Mantis

[Aussie_Mantis]

10 hours ago, 303_Kermit said:

Probably some of you guys are overestimating AiM-7. Their overall efficiency in Vietnam was ~3%. To make it worse AN/APQ-120 had a tendency to loose contact in STT mode.  In fact in Vietnam one field mod of F-4 was very popular. A switch that fixes radar antenna in forward position (Like FLOOD mode in modern planes of '80). That allows AiM-7 to keep track . Pilots called that mode "Boresight"

In Bill Gunston's book most pilots coment's looked like "Shooting missiles is a lot of fun, but pose no threat for PLAF pilots"

About aerial dogfights - before inventing TOP Gun there was a month (August 1967 to be more precise), when USA ( can't recall if USAF or USN) Lost 8 Phantom's II without shooting down a single MiG (any type). It was a consequence of introducing a new PLAF Tactics in low flight lvl flights. Funny fact is, that CIA knew about new tactics and PLAF preparations, but.... considered these news to be ... to important to share it with USAF / USN or USMC, and classified it.

Boresight was later implemented as a standard modification for the radar starting on the F-4E onwards. It's the forerunner to ACM mode.

 

9 hours ago, Temetre said:

But in the end A2A duels is like 190 downed migs and 80 downed US planes. And the US losses were mostly from the beginnig, when they made a ton of mistakes.

From what Ive read, one of the important moments where the tides turned was with Operation Bolo, when a bunch of migs got lured into combat with F-4s. But that was actually with F-4Ds, so without even upgraded versions.

From, what ive read, the kill percentage of Aim7s was 9/13% for USAF/USN or so? But thats including all misses, including ones that arent fault of the missile at all. Mind im not saying the Sparrow was a perfect weapon, far from it. But people saying its "no threat" just seems a bit hyperbolic if you look up how air duels actually played out.

IIRC there was actually something like 50 losses to migs without a single shotdown? Crazy stuff.

But the main issues seems to be training, the USAF had trained for a very different kind of combat.

 

 

I have made a post prior about USAF vs USN loss rates/kill rates of F-4s in response to another user's claims that , which I wil attach here:

Spoiler

  

On 3/26/2023 at 9:55 PM, Aussie_Mantis said:

the US Navy made 40 kills with F-4s of all variants- B, J, and N. 23 kills with USAF F-4Es, 44 with F-4Ds and 41 with F-4Cs means that the US Air Force killed 108 MiGs over Vietnam- higher kill numbers. Due to statistics, and the fact that USAF losses overall during the conflict are inflated due to:

1. USAF aircraft were used more heavily during the conflict, present in higher number and flying a higher number of sorties due to being present in higher number

2. USAF F-4s filled a higher variety of missions, and most squadrons were flying in and out of North Vietnam doing anything from SEAD, interdiction over the Ho Chi Minh to TARCAP while USN F-4s almost exclusively only ever did air to air missions and never did any of the more dangerous SEAD/Iron Hand missions that more than likely inflated USAF losses. Marine squadrons were mostly flying missions down south with their phantoms, not up north.

The USN kill rate during linebacker was 6:1, the USAF one 2:1, but this doesn't actually account for any factors like Route Pack (the USAF usually flew the more dangerous ones or ones defended more by SAM rather than MiG) or mission (USAF aircraft, as mentioned earlier, did a lot of more dangerous missions, often flying into low flak on Iron Hand or Strike Missions, while USN VF squadrons usually stayed more than far out of it and were not prone to being shot down while laden with bombs due to generally not carrying bombs in the first place). In addition to that, K/D statistics really depend on how you count them. Navy pilots and also planners were far more liberal with what they counted as "kills" as opposed to USAF ones, who were far more stringent and made it far more difficult to justify a plane as having "killed" another.

If I remember correctly, Phantom losses in the book: Vietnam Air Losses: USAF, Navy, and Marine Corps Fixed-Wing Aircraft Losses in SE Asia 1961-1973 by Chris Hobson were 51 losses total between the USN and USAF. If we don't account for separate losses- the USAF comes off with a higher kill ratio by virtue of higher kills. However, this is irrelevant, since the USN was not operating with the USAF.

According to the USAF's own data and accouting for Unknowns, 38 phantoms were lost in air to air combat according to their 1973 Operational Summary. This includes aircraft damaged that either landed at base or crash-landed at base and were subsequently written off. The USN is quoted by a USAF Society article as having lost 7 Phantoms, but this only accounts for aircraft that were shot down and never made it back to the carrier- not write-offs or crash-landings. If we adjust for these, the USN lost about ~15 phantoms, while the USAF lost 38 (this already accounts for the crashes) resulting in ratios of 2.84210526 for the USAF, and 2.66666667 overall for the USN. But this is biased due to a small number of USN aircraft killed and missions flown relative to the USAF. I can't say for certain whether the USAF or the USN was better in air to air combat when the USAF just got so many more kills that whatever I say about the USN will be statistically irrelevant and difficult to actually extrapolate any data about. The USAF had nearly 2300 aircraft lost by any cause over 11 years of combat. The US Navy lost significantly less, but also contributed less aircraft, so it honestly makes sense.

I'm not trying to disrespect USAF or USN pilots here. Both made immense sacrifices for their country and my respect goes out to both. What I'm trying to make a point of is that trying to give one service a handjob while actively trying to discredit the other benefits nobody, not me, not you, and not the thousands of USAF servicemen that to us, are just numbers, but to everyone they knew, were people of real flesh and real blood. Both deserve respect. The least I can do for them is to tell the truth of the horrific war they fought, underprepared for the fights that they would engage in due to doctrinal errors and inexperience of using missiles in air to air combat.

We could debate USN/USAF kill ratios forever, but that would derail the thread. The crux of the matter is, neither air arm was prepared for Vietnam- the US Navy was probably the better prepared of the two, but not by much, and their training regimes as opposed to the USAF worked better, especially after '68, and that showed during Linebacker. Thankfully, the USAF got its proverbial #*$@ together and kicked ass in desert storm, and so did the Navy.

TL;DR, the ultimate USN vs USAF loss ratio is about the same.

Sparrow Failure Rates can be attributed to multiple things but it includes things like maintenance, the environment, and shoddy training. The IAF in the 1973 and 1982 wars encountered a lot more success with the AIM-7, with a ~60-70% average kill ratio throughout all those wars, though in 1982, reportedly, Soviet Jammer Pods e.g. SPS-141 were proving a challenge to deal with for the more primitive radars on the F-4E and the seekers on the AIM-7E/F that they were using.

 

I'd also like to ask a question of you lot and also of @SgtPappy, who made a graph on this-

 

Can someone please tell me what the instantaneous/sustained turn rates of the slatted F-4 are? There's a bunch of different values out there and people are saying anything from the F-4E rating worse than an unslatted F-4 to information that contradicts what people here have previously said about the MiG-23, and I'd like to arm up on ammunition for the inevitable fights coming soonish to DCS.

aod for Sgt Pappy, you previously made this graph:

What is the sauce for your information? You stated 1F-4C-1 for F-4E unslatted, and 1F-4E-1 for slatted ones, but I can't find these graphs. In addition, are these instantaneous or sustained rate speeds? And what in the world are the big blue and big red graphs?

Edited June 12, 2023 by Aussie_Mantis

[303_Kermit]

4 hours ago, Aussie_Mantis said:

What is the sauce for your information? You stated 1F-4C-1 for F-4E unslatted, and 1F-4E-1 for slatted ones, but I can't find these graphs. In addition, are these instantaneous or sustained rate speeds? And what in the world are the big blue and big red graphs?

To add the confusion there's a ton of various engine modifications for F-4E. They affected throttle response, engine smoke behaviour, thrust. Question: is there the same engine in compared planes? Is the slot a reason for better performance, or is there something else?

[Bremspropeller]

5 hours ago, Aussie_Mantis said:

And what in the world are the big blue and big red graphs?

The thick lines are the corresponding ITR lines to the thin lines, which are the STR lines.

LH line of the doghouse is the lift limit (AoA limited). RH roof-line of the doghouse is the structural limit. Not sure why it changes from 7.33g to 6g, but Pappy will surely be able to explain that.

The vertical line on the right is either Mach/ KIAS limit or max attainable airspeed/ Mach, which is lower on the slatted bird, thanks to the additional drag.

[Aussie_Mantis]

1 hour ago, 303_Kermit said:

To add the confusion there's a ton of various engine modifications for F-4E. They affected throttle response, engine smoke behaviour, thrust. Question: is there the same engine in compared planes? Is the slot a reason for better performance, or is there something else?

There are???
 

I thought they just used the one J79-GE-17. Do you mind telling me about them?

[KlarSnow]

F-4E's in the USAF all just had variants of the J79-GE-17. I have found no thrust difference for any of the four variants listed in the -1; A/E/F or G. All are listed as being 17,900 lbs of thrust in max afterburner and 11,870 in Mil power. The only difference is the E/G are low smoke with different igniters.

[Aussie_Mantis]

49 minutes ago, KlarSnow said:

F-4E's in the USAF all just had variants of the J79-GE-17. I have found no thrust difference for any of the four variants listed in the -1; A/E/F or G. All are listed as being 17,900 lbs of thrust in max afterburner and 11,870 in Mil power. The only difference is the E/G are low smoke with different igniters.

I see, that makes sense

[303_Kermit]

5 hours ago, Aussie_Mantis said:

There are???
 

I thought they just used the one J79-GE-17. Do you mind telling me about them?

J79-GE-17A / C / E - main difference smoke trail. Different other variants were also tested - since those data come from tests I'm just wondering about precise specification of tested planes. That's all

[G.J.S]

46 minutes ago, 303_Kermit said:

J79-GE-17A / C / E - main difference smoke trail. Different other variants were also tested - since those data come from tests I'm just wondering about precise specification of tested planes. That's all

17C & E we’re fitment on late production F-4E I seem to remember. Unsure of exact type on the early birds.

[SgtPappy]

On 6/12/2023 at 12:54 AM, Aussie_Mantis said:

Can someone please tell me what the instantaneous/sustained turn rates of the slatted F-4 are? There's a bunch of different values out there and people are saying anything from the F-4E rating worse than an unslatted F-4 to information that contradicts what people here have previously said about the MiG-23, and I'd like to arm up on ammunition for the inevitable fights coming soonish to DCS.

aod for Sgt Pappy, you previously made this graph:

What is the sauce for your information? You stated 1F-4C-1 for F-4E unslatted, and 1F-4E-1 for slatted ones, but I can't find these graphs. In addition, are these instantaneous or sustained rate speeds? And what in the world are the big blue and big red graphs?

 

All of that data is from the TO manuals. The images attached to this post are in TO 1F-4E-1 from 1979 and are on digital pages 198 (top) and 445 (bottom). I took the max CL line from pg 198 and just used some meth math to convert it to instantaneous turn rate while both pages 198 and 445 show the same allowed structural limit line.

You can see that at 42000 lbs, that the max CL line intersects the max allowed structural limit at 7.5 G (I mistakenly put 7.33 G) and it drops linearly vs speed/Mach past Mach 0.7 until it's 6 G at Mach 1.05.

The blue thin and dotted lines are also sustained turn rates copied straight from the manual.

There are the same corresponding plots for the hard wing/BLC F-4E in the 1-F-4C-1 TO.

 

 

This data is the probably the most reliable data out there so I've used it for all my comparisons. If you've ever come across the FMS plots for the Phantom or any other plane, note that they are calculations and they do not at all match the aforementioned manuals.

 

 

 

To answer your questions on the actual rates and how they compare, in the old F-4E vs XX aircraft thread, people have posted USN official F-4J turn data and MiG-23ML data and the F-4E performs quite favourably. To summarize, the F-4J with a 4x4 AIM-7/9 loadout needs to be almost empty on fuel (~20% fuel) to match the sustained turn performance of the slatted F-4E per the manual at 60% fuel with 4xAIM-7Es - a max STR of about 14.7 deg/s at SL. Of course because the F-4J is so light in this configuration, it has a higher structural limit, so keep that in mind. These limits will probably go out the window anyway in DCS.

The MiG-23ML and MLA (which are much later, circa 1976 variants - contemporary not to our upcoming early F-4E but to the F-14A and F-15A) have a slightly better STR with wings fully forward but I understand that they are unstable there (not sure which axis) and they have very low structural limits in that configuration, which again are likely to be ignored in game if the plane doesn't break.

 

 

In summary, plots are from actual USAF published manuals and in the same relative configuration,  the slatted F-4E will out rate instantaneously and sustained any US hard wing F-4 by a big margin except when both are at supersonic speeds (where the turn rates drop a lot anyway). The MiG-23ML/MLA have a better max theoretical STR with wings forward but it is unclear if that rate can be used due to the structural limits and stability issues in that wing configuration.

 

EDIT: Upon review at home of my Excel plots, it seems that the 1F-4C-1 and 1F-4E-1 use the exact same symmetrical load limit plot. This would imply they are ballpark suggested limits rather than accurate turn data. So I used the Vn diagrams to find an average CL for each of the hard and slatted wing jets and just plugged those average CL values back into n = L/W = CL*(0.5*rho*S*V^2)/W where n = load factor and W was the new weight I wanted - in this case a more realistic loaded weight per the STR graphs. Sorry for the confusion, it has been a while since I made these plots. I would assume that interpolating and extrapolating would yield similar results.

 

Edited June 14, 2023 by SgtPappy

[Bremspropeller]

18 hours ago, SgtPappy said:

To summarize, the F-4J with a 4x4 AIM-7/9 loadout needs to be almost empty on fuel (~20% fuel) to match the sustained turn performance of the slatted F-4E per the manual at 60% fuel with 4xAIM-7Es - a max STR of about 14.7 deg/s at SL. Of course because the F-4J is so light in this configuration, it has a higher structural limit, so keep that in mind. These limits will probably go out the window anyway in DCS.

Hey Pappy, thanks a lot for your explanations!

Is there a way to estimate through the available manuals, how much drag the inboards with 4x AIM-9 are factoring in for the Juliet? The difference between slats/ no slats should qualitatively persist, of course, but I'd imagine taking off the inboards on the J would shift the numbers a little more towards parity. Maybe 30-35% (just a random guess) fuel to achieve the same STR as the slatted Echo at 60%.

[SgtPappy]

2 hours ago, Bremspropeller said:

Hey Pappy, thanks a lot for your explanations!

Is there a way to estimate through the available manuals, how much drag the inboards with 4x AIM-9 are factoring in for the Juliet? The difference between slats/ no slats should qualitatively persist, of course, but I'd imagine taking off the inboards on the J would shift the numbers a little more towards parity. Maybe 30-35% (just a random guess) fuel to achieve the same STR as the slatted Echo at 60%.

So the issue is that even though you can calculate the drag index in the 1F-4E-1 manual for any combination of external stores, both the weight and drag go up between the STR plots.

It would be possible to ignore the 1000 lb gain between the first two STR plots in the manual and just interpolate STR as a function of drag index but you'd get some error from ignoring the weight change.

However, it may be more accurate to apply this method to the F-4J plots which I still have to find (I only have a screenshot of 1 plot but I imagine there are more). The one plot I have shows 37500 lbs with a full 4x4 A2A loadout. This weight seems to be a common "control" point that a lot of the data is centered around in all three manuals (F-4C, F-4E, NATOPS F-4J). If we're lucky, there will be another plot at the same weight but maybe clean or just 4 Sparrows and then you can more accurately apply the drag index interpolation. I'll have to dig more to see if I can find the other plots. I might know a guy.