Why does the F-15E have a 22.5% thrust loss vs other aircraft

[Ziggy1989]

Look, I like flame & I don’t know how long you have known him, but I have been interacting with him for a long time. Since the last forum. We have agreed strongly on underperformances and disagreed on other random crap. He has outright proven me wrong before & I admit when I am wrong no matter how sarcastic I am about it.

I haven’t said he was wrong once here & only mistaken as above in this case. You see I tailored my comment specifically because yes, he was mistaken. Not even really that, just overlooked the subtle wording though the manual said from the gate "installed thrust". So yeah I think I can be a little hard on my boy for that.

I am a little upset with him because I feel he has shifted from once investigating a matter and pushing for realism to almost serving as a deterrence against it. My comment you replied to was aimed at cheer leaders.

Additionally, I am trying to get my life in order on a Monday night so unfortunately, I did not have a chance to fully read everything, but I did come back here and there, and he does kind of understand the concept of corrected thrust and mentions it. Yes, he overlooked the subtle wording.

If I may say one last thing regarding “disrespect” toward flame & the true perspective of how I view him. I am confused how he still isn’t a tech mod at this point. Regardless of this interaction here and who is “right or wrong” the dude has demonstrated & long established that he is cool headed in fierce, even disrespectful debate, articulate & able to sift through mountains of information on these technologies without being biased for any one particular tech tree or the other. Maybe he never cared to be staff at this point, I don’t know, but that is my thoughts on that.

@FeetPics

The trend is that Ziggy is feeding garbage into an LLM and it’s spitting out nonsense.

Why are you a little hater all of a sudden?

Do you want to see more? Shall we take a walk to the MiG-29G & I show you why the thrust rating applied is 100% installed thrust? That is my next puppy you know I have much more. The MiG-29 is 100% ICAO compliant.

[Ziggy1989]

Yes, I have unsent reports on all these fighters (including Soviets).

Even the Iranian tomcat does not even have to correct engines though differences are slight.

Matter of fact there is a lot on the tomcat performance. We can start a DM convo to get something rolling

[Ziggy1989]

Appreciate this, I was literally on my phone smoking a cigarette in the backyard and wanted to simply describe the concept for those unfamiliar & asked Gemini lol. I never used ChatGpt in my life.

Lol but feety swears I need to get on my desktop, open Theory in Aerospace Propulsion (real textbook btw) and spoon feed it to him when he is a big boy & has access to the internet himself.

To obsess over that as feety is doing is simply a tactic to obscure and divert from any productive discussion into the matter. I have no idea why he is having a tantrum right now & for some reason thinks I am going to pay attention now.

I will post pages and sources to back up what I say moving forward to best of my ability.

I am a lazy though & sometimes I feel those who I am speaking with are not worth my time.

(Oh & thank you for the suggestion regarding future utilization of AI descriptions & explanations, will do)

@Flame2512

Seems pretty clear cut to me:

Brother, it tells you what the installed thrust is in the beginning & tells you again.
You highlighted it…

You are arguing that because you do not understand what installed thrust is (static @ sea, standard day AKA take-off thrust) that is quoted by the manufacturer & since that rating is identical with the final, corrected thrust another unknown… (which quite literally means thrust that has been corrected & adjusted with all installation effects applied) You therefore conclude it is all uninstalled thrust by default…

That is essentially what you are bending over backwards trying to say.

look, I am going to shift over to the MiG-29 but it is related to the subject. I want to highlight how its the most fictional aircraft in all of war thunder starting with the thrust. I want to do this before Christmas. We can continue there or DM me so we productively go over documents etc. too & this matter as well because I do have some questions.

Oh btw team, look into the variable geometry nozzles found in the F-15E, They GREATLY minimize the installation loss & achieve very near perfect ideal thrust. We can hit this from so many angles these jets are straight up underperforming. But we need to research together.

In propulsion, installation penalties are the losses in thrust or efficiency when an engine is mounted in an aircraft versus tested in isolation, factors like:

• External aerodynamic loads (pressure distributions around the nozzle and flaps).
• Structural weight added by nozzle hardware.
• Drag from external flaps and fairings.
• Flow distortions at the nozzle exit due to aircraft geometry.

The balanced beam nozzle was designed to minimize these penalties by using external flaps shaped for recompression reducing base drag. Allowing the divergent section to float, so aircraft-induced loads naturally balanced instead of requiring heavy actuators. Achieving thrust coefficients of 0.97–0.98, meaning only 2–3% loss compared to ideal thrust, a very small installation penalty.

this paper demonstrates that the balanced beam nozzle delivers near ideal thrust efficiency (97–98%) across subsonic and supersonic regimes. This technology is modelled in-game but have zero effect competitively.

[FeetPics]

So just so we can understand this correctly.

You are saying that the installed thrust loss of the F-15 engine should only amount to 2 percent? And you are sure about that?

[Ziggy1989]

Installation loss is not the only loss applied to the aircraft sweetie pie.

PS. I would like to correct this comment. I am not sure. because I have not pulled up the F-15E manual, isolate & compare the balanced beam to earlier engine models of other variants. Remember thrust can be ideal depending on certain flight conditions etc. This is modern engine design after all. Just do some damn research & stop being a darn Negative Nancy.

what I do know is that the Americans are kind of the best at nozzle design and achieve very minimal installation losses in their engine design in the newer fighters…

The variable geometry nozzles & balanced beam are present in game they are modelled & even have sound effects as well, but zero performance effect in-game. It is worth researching my friend.

Yet we are here stuck arguing one’s long drawn out interpretation on a F-4J manual that already states what the installed thrust is in wording that even a child can understand as well as in engineering terminology.

[FeetPics]

You’re so close to getting it.

[FeetPics]

@Ziggy1989

To obsess over that as feety is doing is simply a tactic to obscure and divert from any productive discussion into the matter. I have no idea why he is having a tantrum right now & for some reason thinks I am going to pay attention now.

This is just deflecting from overall point that I made about acceleration performance in-game and the fact that I showed the F-15 is accurately modeled in this metric. In fact it is technically overperforming.

[Ziggy1989]

@FeetPics

This is just deflecting from overall point that I made about acceleration performance in-game and the fact that I showed the F-15 is accurately modeled in this metric. In fact it is technically overperforming.

My apologies, but I honestly haven’t read anything you have said on the subject.

I just do not have the energy right now kiddo. But we can play sim later when I get on if you like?

But hey, do cheer up buttercup, acceleration can be talked about while the thrust can still be underperforming. There are several aircraft that have concerning acceleration performance with low thrust output that never were adjusted. GJ seems to like to offset lack of thrust by increasing aerodynamic efficiency in models they need to compete. Sometimes more than appropriate. That’s why you exist I suppose.

[kizvy]

@Ziggy1989

GJ seems to like to offset lack of thrust by increasing aerodynamic efficiency in models they need to compete. Sometimes more than appropriate. That’s why you exist I suppos

can you give examples?

[Ziggy1989]

I want to clarify some things & show you I did read your step-by-step process. Well, most of it & its missing things besides not being whole pages.

@Flame2512

Corrected thrust in that context means uninstalled thrust that is corrected to match standard atmospheric conditions.

Yes, you are correct. But it is more than that.

@Flame2512

Notice how contrary to your claims NONE of those corrections account for installation losses. They are purely about cancelling out any influences on the measured thrust to ensure the final value is representative of purely the bare uninstalled engine under standard atmosphere conditions.

NO, Its not “bare” because it already been corrected… It is the theoretical engine performance under standard conditions… per DoD, FAA & ICAO airworthiness certification:

At Sea Level, Standard Day…

The corrected thrust is the engine’s ideal, standard-day performance & is the input element in the final installed thrust calculation, and you apply installation correction factors (Remember I mentioned those) which are usually multiplicative ratios or factors for intake drag, bleed air loss, etc. to get the final installed thrust.

You have none of those elements to complete the final installed thrust calculation because It is standard protocol (Airworthiness Certification) that the detailed correction factors needed to convert corrected thrust to final installed thrust are not typically included in a flight manual.

This is where your confusion lies…
Or… It is entirely possible you do have them, but have left them out here…

It doesn’t matter, because the manuals do provide (Per DoD Airworthiness Certification) the final certified installed thrust to give us the target range for such calculations, ensuring our engine performance and installation match the aircraft’s certified limits. Anything outside of these ranges is NOT ACCEPTABLE.

as you see here:

& this…

Is why you see this from the get-go leaving ZERO room for interpretation though you STILL managed to do it:

I am sorry, bro. It is wild to me that instead of back tracking your steps to consider the possibility that you may be mistaken/missing some critical elements in this formula of yours, you decide to assume & conclude confidently that none of this actually means installed thrust, though it declares it repeatedly. Even for several serial produced batches of the aircraft…

Installed thrust is an aircraft-specific value, accounting for losses from the inlet, nozzle, bleed air, and other aircraft systems, which varies by airframe design and is usually only provided in the form of performance charts or data specific to that aircraft model, often calculated by the aircraft manufacturer, not the engine manufacturer.

The flight manual focuses on parameters the pilot uses to set thrust like RPM or engine pressure ratio and the resulting performance data for the aircraft (takeoff distance, climb rate), which already incorporates the installed thrust.

The actual calculation details are usually found in engineering data or engine models used for performance analysis, not operational documents.

[FeetPics]

Oh look more AI slop.

[Ziggy1989]

Nah just copy paste from these.

@FeetPics

This is just deflecting from overall point that I made about acceleration performance in-game and the fact that I showed the F-15 is accurately modeled in this metric. In fact it is technically overperforming.

Look, I understand you have a YouTube podcast or whatever, but the world does not revolve around you. I honestly never read a thing you said prior to my first post on the subject a couple days ago. Remember I’ve been gone all year.

Look at all your post the last few days. You are seething & they are all about me. I was nice, even asking to play sim regardless of how negative you are. You are now starting to creep me out.

The F-15 accelerates too fast, there I said it. Can you leave me alone & stop trolling? You have been on my bumper non-stop demanding my attention the second I came back. I would like you to stop & give me a some space.

@FeetPics

Oh look more AI slop.

No not AI, I worked hard to tailor my post repeatedly as not to be rude to Flame but you continuously set the atmosphere purely to negative & I kind of lose track of who I am actually speaking with.

[spartinwarrior64]

that would change horsepower per ton or in this situation thrust to weight, not the thrust which we are talking about…

[spartinwarrior64]

what do you think the F-15’s variable intakes do?

[Ziggy1989]

Yeah. Variable are more capable at supersonic & over wider range of regimes than the S duct. Able to fine tune accordingly. They have their drawbacks like weight etc.

F-15 is still the fastest fighter in US service correct? Highest top speed, right?

[Knuckles7080-live]

Too bad the yf12 didn’t enter service supposedly it tested aim47 successfully

Spoiler

[quartas121]

@Knuckles7080-live

yf17

YF-12. YF-17 was the predecessor to the F/A-18 that competed with the YF-16 for the LWF program and lost

@Knuckles7080-live

supposedly it tested aim47 successfully

not supposedly, it did, multiple times

[Knuckles7080-live]

Oh yeah typo my bad

[itango]

Kicks in at about mach .5 and decreases loss significantly
But kinda bad at takeoff

There were probably later minor tweaks to the intakes after modeling to optimize thrust. The math’s all in here for calculating intake pressure which can help with calculating overall thrust.

19810006485.pdf

19780015152.pdf

[Flame2512]

@Ziggy1989

I am sorry, bro. It is wild to me that instead of back tracking your steps to consider the possibility that you may be mistaken/missing some critical elements in this formula of yours, you decide to assume & conclude confidently that none of this actually means installed thrust, though it declares it repeatedly. Even for several serial produced batches of the aircraft…

Installed thrust is an aircraft-specific value, accounting for losses from the inlet, nozzle, bleed air, and other aircraft systems, which varies by airframe design and is usually only provided in the form of performance charts or data specific to that aircraft model, often calculated by the aircraft manufacturer, not the engine manufacturer.

I have explained in detail why I believe the thrust given for the J79-GE-10 in the F-4J Flight Manual to be for an uninstalled engine. How about you answer me this:

As you stated yourself “Installed thrust is an aircraft-specific value”. The J79-GE-10 is used in multiple different aircraft, so:

• Why would the US navy datasheet for the j79-GE-10 that I shared previously list installed thrust, when this would be different from aircraft to aircraft?
• Why would the test procedure detailed in the J79-GE-10 maintenance manual give you an installed thrust value, as once again the expected installed thrust would be different from aircraft to aircraft?
  • And this ignores the fact that I literally explained step by step how that corrected thrust value is arrived at, and demonstrated that at no point is a correction for installation losses applied.

Or on second thoughts maybe don’t bother. Here is J79 page from a General Electric Aircraft Engines brochure. Notice that thrust rating for the J79-10: 11,870 lbf at military thrust and 17,859 lbf at max afterburner, and that it states the J79-GE-10 is used on both the F-4 Phantom and A-5 Vigilante. Interesting how the listed thrust values exactly match the previous US navy datasheet I shared for the engine, as well as the SAC document, and the and the static test bench results listed in the maintenance manual isn’t it?

Spoiler

Now at this point we could engage in a long debate about whether those thrust values are installed or uninstalled; and if they are installed which aircraft they relate to, or whether the F-4 and A-5 happen to have exactly identical installation losses despite completely different intake designs. But how about we avoid that and instead consult the RA-5C flight manual:

So there we have it in black and white: 17,859 lbf at max afterburner is the uninstalled rating of the J79-GE-10, just as I’ve been saying all along. Also notice how the J79-GE-8 thrust ratings match those listed in the F-4J flight manual as well.

So either the F-4J has literally zero installation losses (making the installed thrust equal to the uninstalled thrust) or maybe, just maybe, the F-4J flight manual (like many others I have seen) is using the uninstalled ratings.