LO's F-15 vs. the F-15 Streak Eagle

[Yo-Yo]

... and listen to the driver.

 

 

As our practice shows the driver info is useful only in some fields of FM development. For expample, the short-periodic movement, controllability or some special flight cases such as departure, stall, etc. For the long-periodic or trajectory movement the info they give is not only less useful but rather desorientational.

It's not because of the lack of professionalism. Thre are objective reasons for it. The main one is the abscence of acceleration sensors in the sim. That's why accelerations/decelerations in the sim ALWAYS are underestimated by the pilots with RL experience. It's a well known fact amongst the sims developers. By the way if we have semi-dome visualization with correct angular size this effect reduces because of our side vision effect.

 

The first thing the pilot who tested Su-25 told us was: Your plane accelerates/decelerates to slow! OK, - we said, - look at your notes how much time to acc/decel from one speed to another.

Then we tested the model and it showed EXACTLY the same numers he had said.

 

But when the pilot described taxiing, stalling, takeoff and landing his information was very valuable.

[Trident]

If you, guys, provide a math converter to convert such terms as "great to fly", "nightmare", etc into tables and curves... I promise to revise the model. :)

 

As our practice shows the driver info is useful only in some fields of FM development. For expample, the short-periodic movement, controllability or some special flight cases such as departure, stall, etc. For the long-periodic or trajectory movement the info they give is not only less useful but rather desorientational.

It's not because of the lack of professionalism. Thre are objective reasons for it. The main one is the abscence of acceleration sensors in the sim. That's why accelerations/decelerations in the sim ALWAYS are underestimated by the pilots with RL experience. It's a well known fact amongst the sims developers. By the way if we have semi-dome visualization with correct angular size this effect reduces because of our side vision effect.

 

The first thing the pilot who tested Su-25 told us was: Your plane accelerates/decelerates to slow! OK, - we said, - look at your notes how much time to acc/decel from one speed to another.

Then we tested the model and it showed EXACTLY the same numers he had said.

 

I agree with Iguana King, Rhen's opinions are worthy of consideration. He has actually *quantified* his complaints as suggested by you in this post, so it's a different situation:

 

HOWEVER, have you looked at the performance of the aircraft in MIL power? It's severely ANEMIC! The time to climb is SIGNIFICANTLY longer than it would be IRL (more than 1.5 times greater) to get to 40,000 than the real jet at 39,000Lbs. The distances are 1.5 times greater as well. The combat ceiling at MIL power is reached earlier as well.

 

I would also like to point out that level flight acceleration at high altitude also appears off. Of course it's not quicker, it's quantitatively slower by 20%. This can be tested by taking a clean F-15 from M0.83 (to compensate for pylon drag) and accelerating a 39,000Lb Eagle at 40,000ft to M1.0, which should take about 25 sec, but actually takes 30.

 

LOMAC obviously isn't too far off at 10000 feet as evidenced by your chart, but what about 40000 as pointed out above?

 

I for one don't expect a quick fix, since the Ka-50 is your current priority, but I hope we can get to the bottom of this in preparation for AFM fighters in some future ED product :)

[GGTharos]

But Yo-Yo, Rhen did provide quantitative information. If you look back he provides specific data points; personally I appreciate that you two are talking even as it is right now, it is better than saying nothing at all. :)

 

 

As our practice shows the driver info is useful only in some fields of FM development. For expample, the short-periodic movement, controllability or some special flight cases such as departure, stall, etc. For the long-periodic or trajectory movement the info they give is not only less useful but rather desorientational.

It's not because of the lack of professionalism. Thre are objective reasons for it. The main one is the abscence of acceleration sensors in the sim. That's why accelerations/decelerations in the sim ALWAYS are underestimated by the pilots with RL experience. It's a well known fact amongst the sims developers. By the way if we have semi-dome visualization with correct angular size this effect reduces because of our side vision effect.

 

The first thing the pilot who tested Su-25 told us was: Your plane accelerates/decelerates to slow! OK, - we said, - look at your notes how much time to acc/decel from one speed to another.

Then we tested the model and it showed EXACTLY the same numers he had said.

 

But when the pilot described taxiing, stalling, takeoff and landing his information was very valuable.

[D-Scythe]

The first thing the pilot who tested Su-25 told us was: Your plane accelerates/decelerates to slow! OK, - we said, - look at your notes how much time to acc/decel from one speed to another.

Then we tested the model and it showed EXACTLY the same numers he had said.

 

Yeah...Rhen DID provide numbers, and they DIDN'T match. Specifically, he said that acceleration from Mach 0.83 to Mach 1.0 at 39000lbs/40000ft was off by 5 seconds (it takes 25 seconds IRL compared to 30 seconds in LOMAC).

 

Is it possible that maybe you guys simply interpreted the Dash 1 chart wrong? If nothing else, how much can talking to Rhen hurt? :)

[GGTharos]

I think the in-game top-speed chart at that altitude shows the curve zig-zagging around that of the real chart, which -might- be a reasonably acceptable error. There was, however, some information provided -specifically- about MIL power thrust v altitude which should be looked at.

[D-Scythe]

I think the in-game top-speed chart at that altitude shows the curve zig-zagging around that of the real chart, which -might- be a reasonably acceptable error. There was, however, some information provided -specifically- about MIL power thrust v altitude which should be looked at.

 

I brought this up before - in the "real" top speed chart, the F-15's top speed shown (around Mach 2.3-4ish) is an airframe limit, not a performance limit - extended flight times beyond Mach 2.3 is not really friendly to the airframe. The curve literally looks like it hits a wall, with basically the F-15's envelope past that speed being truncated out.

 

However, Lock On's curve looks like it takes it as an ACTUAL performance limit. It tops off at Mach 2.4, WITHOUT the wall. That's probably another indication of the lack of acceleration/thrust at altitude.

 

 

If you take into consideration that the speed curve for the real F-15 above extends to Mach 2.5+ above, than the F-15C *severely* underperforms at altitude (specifically, between 38 - 50 000 ft).

[GGTharos]

The actual FF is not indicated correctly. I have a little app for my G-15 that indicates fuel flow properly (by measuring fuel used) together with a custom bingo setting.

[Yo-Yo]

Yeah...Rhen DID provide numbers, and they DIDN'T match. Specifically, he said that acceleration from Mach 0.83 to Mach 1.0 at 39000lbs/40000ft was off by 5 seconds (it takes 25 seconds IRL compared to 30 seconds in LOMAC).

 

Is it possible that maybe you guys simply interpreted the Dash 1 chart wrong? If nothing else, how much can talking to Rhen hurt? :)

 

I agree... in Lomac this time even is not 30 but 32 s.

 

Did you noticed engine trim number 25 second acceleration is for? 102%!

As we have turn and envelope data for 97.7% we presumed this trim value for MAX thrust.

The same time for 95% trim in Dash 1 is about 42 s.

 

Though the thrust is not a linear function of GG rpm the small part of this function can be linearized so try to find the time for 97.7 s regarding these Dash 1 numbers... ;)

[GGTharos]

But, how does it relate to the actual engines? Your G-15 profile is probably just taking a known conversion factor. I'll bet the in-game engine FF is directly linked to the calculated FF, as opposed to indicated...which would SERIOUSLY be underfeeding those engines for their max MIL output. :smilewink:

 

 

My app does Fuel 0.1s before - Current fuel for fuel consumption and reports that in lbs/min.

[GGTharos]

My FF is correct for LO. It works off the fuel gauge.

[SwingKid]

If you operate with MOORZILKA's data kinda " THE engine XXXX-XX has XX lb of thrust" you must know the speed the thrust is for and if it includes ram loss.

 

Of course, I have accounted for both. The bench thrust is at a speed of zero. The thrust that I measured in Lock On is also at a speed of zero.

 

At zero speed, ram loss is also zero, both for the real F-15C and for Lock On.

 

-SK

[SwingKid]

Please note that me and of course Yo-Yo and others are still waiting for proof (chart, formula, or whatever) showing that it isn’t modeled accurate.

 

What's wrong with

 

http://forum.lockon.ru/showthread.php?p=321044#post321044

 

and

 

http://forum.lockon.ru/showthread.php?p=322900#post322900

 

?

 

-SK

[TucksonSonny]

What's wrong with

 

http://forum.lockon.ru/showthread.php?p=321044#post321044

 

and

 

http://forum.lockon.ru/showthread.php?p=322900#post322900

 

?

 

-SK

 

I guess the formula proves not to be accurate or this graph is not accurate:

 

[GGTharos]

As it should. Are you passing the known disparity on to ED?

 

 

They already know its wrong. I'll bring it up again.

I was able to use my little app to compute some flight profiles which I've seince forgotten ... for F-15's and A-10's.

[TucksonSonny]

The fastest I've ever been in level flight was M2.42 on an intercept. That's after dropping the centerline, with 4Slammers, and 4 Sidewinders.

 

That's not the fastest I've ever been though...

 

You dropped 4slammers and 4sidewinders?

[SwingKid]

Swingkid:

 

The difference between a 40,000Lb & 50,000Lb Eagle when coming off the runway to 350 is still pretty negligable...

 

Well that's an interesting change of topic, but it's not what the Dash-1 says, and it's not what I was asking. Please, let's clarify with an illustration:

 

 

First, I have taken the liberty of marking the part of the Dash-1 that YOU said to disregard with a big red "X"

 

Now, let's turn our attention to the region of the Dash-1 chart that is in the blue circle. What we're looking at here is the curve labeled "5,000 FT." In particular, note how unlike all the other curves on this chart, the 5,000-ft curve becomes perfectly vertical as we follow it downwards.

 

The two purple arrows indicate the gross weights of 30,000 and 45,000 lbs. Between these two arrows, the 5,00 ft curve is vertical. It is NOT vertical between 40,000 and 50,000 lbs.

 

That's why in this post:

http://forum.lockon.ru/showthread.php?p=323798#post323798

 

I am asking about 30,000 lbs and 45,000 lbs. The Dash-1 chart claims that regardless of this weight difference of 50%, the F-15 will require the exact same horizontal distance to climb to 5,000 feet, and that the horizontal distance is 1.0 nm. It makes no such claim for an F-15 increasing its weight from 40,000 to 50,000 lbs.

 

What do you think? Is the Dash-1 chart correct about this?

 

-SK

[SwingKid]

I guess the formula proves not to be accurate or this graph is not accurate:

 

 

Hmm, I don't think anybody in these 22 pages is complaining about performance at 10,000 feet.

 

-SK

[GGTharos]

I matched the -1 chart above in a test right now ... after you get to 350KIAS (from SAKI) I get 1nm to get to 5000' out of a 30000lbs aircraft, 1nm at 40000lbs, and 1.2nm at 45000lbs - 1.4 or so at 50000lbs.

 

At least ... I think I matched it.

 

Getting to 350 took 1nm, 1.2nm, 1.5nm and 1.6nm respectively. What exactly is the problem here?

[SwingKid]

I matched the -1 chart above in a test right now ... after you get to 350KIAS (from SAKI) I get 1nm to get to 5000' out of a 30000lbs aircraft, 1nm at 40000lbs, and 1.2nm at 45000lbs - 1.4 or so at 50000lbs.

 

Getting to 350 took 1nm, 1.2nm, 1.5nm and 1.6nm respectively. What exactly is the problem here?

 

The fact you can do all of the above, with only 34,000 lbf thrust. A real F-15 has 47,000.

 

http://forum.lockon.ru/showthread.php?p=323739#post323739

 

Therefore, matching the Dash-1 = underpowering the F-15.

 

-SK

[GGTharos]

No, matching the -1 is matching the -1. I did this test using MAX power.

Did you do your measurements when the throttle was already at AB?

 

Also the post you refer to - the 1nm figure was (looks liek it was) just a 'hey, let's say this happens in 1nm across the board and we're done'.

 

I don't disagree that in some regimes the F-15 is underpowered. I just don't think you can say 'it matches the -1, and therefore it is underpowered'.

 

Don't you have some more charts in there that might prove more useful SK?

 

Acelleration? Ps curves for all g/altitudes?

 

Rhen's point that it was very easy to cause a variation from the -1. Also the MAX power -1 is matched - I suggest you rbeak otut the MIL power -1, and post it - we'll all find it -much- more interesting I think. :)

[SwingKid]

No, matching the -1 is matching the -1. I did this test using MAX power.

Did you do your measurements when the throttle was already at AB?

 

Correct.

 

Also the post you refer to - the 1nm figure was (looks liek it was) just a 'hey, let's say this happens in 1nm across the board and we're done'.

 

I would agree, not only for this chart, but also for others in the Dash-1. The low-altitude lines all look like someone took a ruler and just drew a stright line through (0,0) - without any regard for what this physically means. That's the whole point I'm trying to make - to Yo-yo, to Rhen, to anyone who is interested. The Dash-1 contains some data that is too approximate for our use.

 

I don't disagree that in some regimes the F-15 is underpowered. I just don't think you can say 'it matches the -1, and therefore it is underpowered'.

 

Back up a bit, I think you have misunderstood the order of cause and effect that I'm trying to present:

 

(1) By F=m*a, I have established, beyond any reasonable doubt, that the sea level thrust of the F-15C in Lock On does not exceed 34,000 lbf.

 

(2) Despite this, the sea level performance of the F-15C in Lock On matches the Dash-1.

 

(3) Therefore, the Dash-1 does not describe the sea level performance of the 47,000 lbf F-15C correctly.

 

(3) follows from (1) and (2), not the other way around.

 

Don't you have some more charts in there that might prove more useful SK?

 

Me?

 

Of course. I use the Streak Eagle data, which has so far given me no such ridiculous contradictions.

 

Does the Dash-1 have more useful charts?

 

No. They are all like that - straight lines that somebody drew with a ruler down from high altitude to the artifically fixed point of (0,0).

 

Acelleration? Ps curves for all g/altitudes?

 

I have some more data, but it is MUCH more complicated to analyze. It's basically a graph of airspeed, altitue, Gs, turn rate, turn radius, etc. during a mock dogfight between an F-15 and an A-4. Beautiful stuff, but if we can't even agree on what thrust the F-15C should be producing at takeoff, and whether tLock On and/or the Dash-1 describe it correctly, then we have little hope of analyzing that.

 

Rhen's point that it was very easy to cause a variation from the -1. Also the MAX power -1 is matched - I suggest you rbeak otut the MIL power -1, and post it - we'll all find it -much- more interesting I think. :)

 

Trouble is, do we know what the mil power thrust is supposed to be?

Much easier to analyze max power, I think. That thrust evel is published in many places, and is more easily verifiable.

 

Walk before we run.

 

-SK

[GGTharos]

I disagree SK. MIL thrust is VERY important. MIL thrust defines your entire cruising envelope.

 

Now, you're asserting that the F-15C in LO only produces some 34000lbf.

 

I have an ACMI file which does indeed show my F-15C accelerating at 1G or so one the runway - this was a 30000lbs F-15, so if we're looking at a /pure/ thrust availability of 47000lbf, my TWR should be something a little over 1.5, and so I should be accelerating at 1.5g+.

 

However, we can still match the -1 in some cases, and we can't in others. So I'm not entirely certain what is going on here.

The -1 is NOT for an under-powered F-15 - there are some other factors that we're missing.

[TucksonSonny]

In the past I made this graph by extracting data from the F-16 hffms.

It shows the relation between altitude and maximum thrust at full AB produced:

 

 

I think this is the answer for your thrust behavior problem.

 

The conclusion: At high altitude your jet engine produces less thrust but needs less thrust to perform!

 

 

 

A question for ED:

 

What about the LEF modeling (the Leading Edge Flap)

(The LEF effect was included with the data to calculate the lift in hffms)

[Pilotasso]

SOnny you just discovered the weel, but thats not what were talking about.

We all knew thrust decreases at altitude but what you missed in your study is the rate a wich that hapens and how much of that total max power is achieved in military thrust only. On some engines AB produces double the power of military thrust, on others such as the F-22 engines its 80% of total power.

 

In my opinion its just the drag issue. OK the model aint perfect and there is discrepancies just like those I described above, but its the weapons drag by far that have the worst impact. If ED is over this I dont think its worth to keep beating a dead horse.

[TucksonSonny]

On some engines AB produces double the power of military thrust, on others such as the F-22 engines its 80% of total power.

 

 

What engine are we talking about again? 220? :D

 

Anyway little list history:

 

General Electric:

 

F110 – GE – 100

F110 – GE – 129

F110-GE-132:

The Block 60 F-16E/F, which is being developed for the United Arab Emirates, features extra payload and range, in part due to the new F110-132 engine being developed by General Electric, which produces 145kN of thrust.

 

Pratt & Whitney:

 

For the F100-PW-200 version,

normal dry thrust is 12,420 pounds, rising to a maximum thrust of 14,670 pounds at full

military power. Maximum afterburning thrust is 23,830 pounds.

 

F100-PW-229: Pratt & Whitney introduced the more powerful (F100-PW-229 early 1990s)

(rated at 29,100 pounds of thrust with full afterburner)

 

The F100-PW-200+ (was intended for foreign air forces which were denied access to

the more powerful -229)

F100-PW-220E: A kit has been developed to bring earlier -200 engines up to a standard nearly equivalent to -220, these converted engines being designated F100-PW-220E.

 

F100- PW-220 (used in F16 – MLU)

 

Performance of the F100 (used in the Belgium F-16A/B) is today comparable with the F110-132 engine being developed by General Electric, which produces 145kN of thrust or 32000 pounds of thrust

PS. 145Kn (kilo newtons) is about 32597.29 pounds-force

 

From its original 24,000-pound thrust class rating the F100 has matured into an engine that can produce in excess of 32,000 pounds of thrust (+33% thrust increasing) and remains a standard for fighter engine performance.