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

[britgliderpilot]

What, you trust an Eagle pilot and his "Dash-1" nonsense over me??

 

You'll live to regret that. :)

 

Check PM

 

-SK

 

Have done my own numbers and am satisfied. Those were in full AB on the deck, right?

 

I can't see any way for the drag at those speeds to be taking 10,000lbs away from the accelerative force . . . . so no there no longer seems any doubt that the Lomac F-15 isn't producing the published thrust levels when it most probably should be. Mmmn.

[S77th-GOYA]

Nice ninja edit, D-Scythe. :smilewink:

[Rhen]

Have done my own numbers and am satisfied. Those were in full AB on the deck, right?

 

I can't see any way for the drag at those speeds to be taking 10,000lbs away from the accelerative force . . . . so no there no longer seems any doubt that the Lomac F-15 isn't producing the published thrust levels when it most probably should be. Mmmn.

 

This is extremely apparent at MIL power. If I had to fly the Eagle in afterburner (not full AB) as much as I had to fly the LOMAC F-15, just to approximate performance in MIL power...

 

Regardless what SwingKid says :P about comparing the streak to the combat Eagle, it's not a real comparison. The comparisons can be made against the Dash 1 and the performance capabilities it produces.

 

The more I fly the LOMAC Eagle at the edge of the high/low airspeed and high AOA envelope, I see that it's not the Eagle but some other aircraft.

 

If the LBF thrust at SL is incorrect for the LOMAC Eagle in comparison with the real thing, then why did it leave beta like that? It's common knowledge what the PW-100 and the PW-220 produce . . . whatever you guys are trying to model.

 

Drag shouldn't be hard to establish either, if you have a copy of the F-15A-1. There's plenty of methods to extrapolate for each weapon, pylon, and tank.

 

The mass - weight of the aircraft is a known quantity as well.

 

Now, this might be heresy, since I'd like a model that conforms to reality - BUT! it's not necessary to model the thrust exactly - it can be off, by as much as 12% and still produce something that behaves like the real Eagle, if the other numbers are also off by roughly 12%.

 

Yo-Yo has established that the LOMAC F-15 behaves closely to the dash 1 climb schedule using the appropriate techniques, and MAX AB. But he hasn't established that it conforms to the dash 1 in any way in any other power setting - MIL power. The combat ceiling, level flight, and sustained level turn performance are off.

 

What we all agree upon is the fact that there's indeed something amiss here. I'm sure this also applies to your favorite Russian aircraft as well, if these anomolies in aircraft behavior affect the Eagle.

 

The most important thing is to eventually fix this by reevaluating the engine data - whether it's tabular or whatever, the drag coefficients, or aircraft mass with respect to force to produce an appropriate acceleration.

 

Who ya gonna believe, a pencil-necked geek with a slide rule and streak Eagle charts, or an Eagle driver and his dash 1 :P :megalol: :smartass: :D

[Rhen]

What, you trust an Eagle pilot and his "Dash-1" nonsense over me??

 

You'll live to regret that. :)

 

You must spread more rep before giving it to...:megalol:

[SwingKid]

Rhen,

 

I hesitate to say, "the Dash-1 is full of crap," but I think you'll be forced to agree that its information is not appropriate for the type of performance modelling we need in Lock On. Consider the following chart.

 

 

It dosn't take a rocket scientist - anyone who's watched a Viking takeoff at an airshow will know that a 30,000-pound aircraft with 47,000 lbf engine thrust does NOT need two nautical miles of horizontal distance to reach a mere 5,000 feet of altitude.

 

The problem is that we're focusing on a tiny corner of the Dash-1 chart, where most of our sim flying is done, but that part of the chart is just a ruler-drawn extrapolation of the performance of MUCH heavier, draggier F-15s to much higher altitudes - which is what most of the Dash-1 is about. This crude level of approximation in the low-altitude, low-weight, low-drag parts of the chart(s) is NOT sufficiently precise of a reference for our simulator.

 

How did the underpowered engine thrust get past beta testing? Well of course - it didn't. As D-Scythe has already indicated, we've been reporting and complaining about this for years. Unfortunately, somebody keeps telling ED that "the Dash-1 is correct," so we never get listened to!

 

;)

-SK

[Rhen]

Ok, let me try to explain this again, in a way that even a PhD can understand :P . Those charts are based on only ONE WAY of flying. The way that those charts work is by using the climb methodology of the Dash 1. It should IN NO WAY be misconstrued to be applicable to a climb profile differing from the Dash 1 profile, like, shall we say, a viking climbout or a STREAK Eagle climbout.

 

The Dash 1 method of climbout is to get to 350KCAS in 1NM from brake release (if using MAX), or 2NM (if using MIL). It does NOT pertain to a climbout that starts at GREATER than 350KCAS or a pitch attitude greater than that to hold 350KCAS in MAX.

 

Like I've said before, I can make the LOMAC Eagle beat these charts too, but I'm NOT following the -1 climbout methodology, I'm following some other type.

 

Now when you say that the -1 is INcorrect, you're just plain wrong IF it pertains to the performance of the F-15 when using the -1 climb techniques. :book: Now, I'll totally agree with you that the -1 Climb charts are INcapable of describing the time/fuel/distance of a viking climbout or a STREAK Eagle climb profile. It can't. The -1 wasn't designed to show you numbers for that because we don't fly climbouts that way on a day-to-day basis. We usually fly the -1 climb profile.

 

That's why I've always wondered HOW you guys are using these charts. These charts were all based on flight performance using a specific technique. Now if you model the mass appropriately, drag appropriately, the engine thrust that follows a very flat parabolic curve with respect to velocity vs engine thrust available, and a very flat (linear might actually work) curve (opposite the previous curve) representing altitude vs engine thrust, then you'll satisfy my desire for the aircraft to actually meet the -1 performance benchmarks, and your desire to accelerate straight up near sea level.

 

Again, we all agree something's wrong here. We're arguing about where to find the answers and the metrics to measure where and how it's wrong. You're privy to more about the LOMAC F-15 than I, so perhaps we could work together to find the real answer. :)

[SwingKid]

The Dash 1 method of climbout is to get to 350KCAS in 1NM from brake release (if using MAX)

 

Huh?

MAX (47klbf) thrust will take a 30klb F-15 from 0 to 350 KCAS in about 12 seconds, over a distance of 0.6 nm.

 

What does the Dash-1 expect that we're doing for the next 0.4 nm/18 seconds, in order to prevent our F-15 from accelerating past 350 KCAS, before we start our climb?

 

Turning loops in a holding pattern over the runway? :)

 

-SK

[hitman]

You know what I havent had in a while? Big League Chew.

[Rhen]

Huh?

MAX (47klbf) thrust will take a 30klb F-15 from 0 to 350 KCAS in about 12 seconds, over a distance of 0.6 nm.

 

What does the Dash-1 expect that we're doing for the next 0.4 nm/18 seconds, in order to prevent our F-15 from accelerating past 350 KCAS, before we start our climb?

 

Turning loops in a holding pattern over the runway? :)

 

-SK

 

Don't get caught up in that stuff. Like I've said in a previous post. The chart is appropriate after getting to 350KCAS. Don't worry about 0.4NM and 4 seconds (not 18 ). What's that in the immense scheme of things? That table starts at 350KCAS and airborne in MAX. This would take care of tire drag, induced drag, etc.

 

I've also said that the acceleration to 350 isn't represented on the chart. The 1NM burner, and 2NM MIL thing just represents a median weight Eagle that accelerates to 350. Wadaya gonna do? The difference is pretty negligible and is less than the variations in pilot technique in the climb to altitude - especially if doing a formation takeoff.

 

Next?

[SwingKid]

The chart is appropriate after getting to 350KCAS.

 

You mean to say that below 5000 feet, a 45,000 lb F-15 climbs the same as a 30,000 lb F-15?

 

-SK

[Yo-Yo]

This is extremely apparent at MIL power. If I had to fly the Eagle in afterburner (not full AB) as much as I had to fly the LOMAC F-15, just to approximate performance in MIL power...

 

 

If the LBF thrust at SL is incorrect for the LOMAC Eagle in comparison with the real thing, then why did it leave beta like that? It's common knowledge what the PW-100 and the PW-220 produce . . . whatever you guys are trying to model.

 

Drag shouldn't be hard to establish either, if you have a copy of the F-15A-1. There's plenty of methods to extrapolate for each weapon, pylon, and tank.

 

The mass - weight of the aircraft is a known quantity as well.

 

Yo-Yo has established that the LOMAC F-15 behaves closely to the dash 1 climb schedule using the appropriate techniques, and MAX AB. But he hasn't established that it conforms to the dash 1 in any way in any other power setting - MIL power. The combat ceiling, level flight, and sustained level turn performance are off.

 

The most important thing is to eventually fix this by reevaluating the engine data - whether it's tabular or whatever, the drag coefficients, or aircraft mass with respect to force to produce an appropriate acceleration.

 

It does conform. In the future if you establish that something wrong in the performance please proove it by evidences kinda :) "I tried to accelerate 39000 lb F-15 at 10000 ft then I plotted speed vs Mach chart AND IT OFF for XX%". Or smth similar. 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.

If you consider correct that F-15 must have max L/D ratio about 6-7 to fit acceleration and sustained turn charts, OK, but others consider it ridiculous... especially if they know that MiG-29, for example, has 10 and Su-27 has even more.

 

Sorry, but if somebody wants to complain to the performance issues he has to make some tests and compare it with official charts for the same (or very close) conditions. Only in this case the issue will be valued.

 

And as a dessert for doubtful Thomases I attached the MIL acceleration chart for 39000 lb F-15 at 10000 ft (Fig. A9-11).

[GGTharos]

But what about at 30000'?

 

Also, I do not have official charts - where may I find them? :)

[rogue_blade]

so uhhh whats the conclusion here? once again we all realize the f15's performance isn't accurately modeled?

[S77th-GOYA]

so uhhh whats the conclusion here?

 

There is no conclusion here. Yo-Yo says the F-15 is modeled correctly and the real world F-15 pilot says it isn't. Although, you might make your own conclusions.

[TucksonSonny]

so uhhh whats the conclusion here? once again we all realize the f15's performance isn't accurately modeled?

 

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.

[TucksonSonny]

There is no conclusion here. Yo-Yo says the F-15 is modeled correctly and the real world F-15 pilot says it isn't. Although, you might make your own conclusions.

 

I wonder if the real F-15 pilot ever flew over Mach 2.5 (it is possible that even with 3000 hours they never could do it because of limiters or downgraded engines)

 

Not sure about the loadout/drag issue anyway..

[Rhen]

It does conform. In the future if you establish that something wrong in the performance please proove it by evidences kinda :) "I tried to accelerate 39000 lb F-15 at 10000 ft then I plotted speed vs Mach chart AND IT OFF for XX%". Or smth similar. 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.

If you consider correct that F-15 must have max L/D ratio about 6-7 to fit acceleration and sustained turn charts, OK, but others consider it ridiculous... especially if they know that MiG-29, for example, has 10 and Su-27 has even more.

 

Sorry, but if somebody wants to complain to the performance issues he has to make some tests and compare it with official charts for the same (or very close) conditions. Only in this case the issue will be valued.

 

And as a dessert for doubtful Thomases I attached the MIL acceleration chart for 39000 lb F-15 at 10000 ft (Fig. A9-11).

 

I guess this wasn't enough for ya, a few posts back, huh? :doh:

 

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.

 

My emphasis added. All comparisons made from the LOFC Eagle to the F-15 Dash 1.

 

You can say that your Eagle is modelled correctly, but take it from a guy with 2,500 hours in the jet - you're wrong. The charts say it as well. You can show me charts of your F-15 gliding into Mare Chronium on Mars to prove that it's got plenty of thrust in MIL, and I'll still tell you that you've modeled it incorrectly because it doesn't conform to the Dash 1, which you have in your posession.

 

The F-15 is great to fly between 30,000ft & 40,000ft, but your F-15 is a nightmare. It's behind the power curve in any power setting other than MAX. There's no way I can lock up a MiG-29 flying at 5,000ft at 60+NM, at 35,000ft, at M0.9, and accelerate to M1.5 and fire a slammer and kill it at, oh, let's say greater than 20NM. Now that's realistic.

 

Swingkid:

 

The difference between a 40,000Lb & 50,000Lb Eagle when coming off the runway to 350 is still pretty negligable - how can I put this - as long as you use the Dash ONE climb profile. Now, if you want to take a 40,000Lb Eagle, hold it on the deck until 500KCAS and then pull a 4g climb straight up and compare that to a 50,000Lb Eagle doing the same, then YES there will be major differences in altitude and airspeed after 30 sec.

[Rhen]

I wonder if the real F-15 pilot ever flew over Mach 2.5 (it is possible that even with 3000 hours they never could do it because of limiters or downgraded engines)

 

Not sure about the loadout/drag issue anyway..

 

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...

[Yo-Yo]

May be the reason is not in F-15 but in AI MiG-29? If so I agree that AI MiG-29 is overmodelled. :)

 

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. :)

 

Once again: everyone can take a table from the Flight Manual and perform his own test flight in the same conditions then compare the results.

[S77th-GOYA]

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...

 

It comes down to this: Either Rhen is a liar or LOMAC is completely ludicrous in F-15 velocity/drag modeling. Personally, I think Rhen has never presented anything that even begins to make himself less than 100% trustworthy. But Ed has seemed to base their modeling on data that they don't fully comprehend.

[S77th-GOYA]

May be the reason is not in F-15 but in AI MiG-29?.

 

No, it is in F-15.

 

Overmodeling of the MiG is a completely different issue and from real world data of the MiG it is not limited to AI. The whole thrust of this thread is the F-15 and I have not seen any mentions of comparisons to the MiG as a reason to doubt the F-15 modelling, although they exist.

[S77th-GOYA]

I could be wrong about this but it seems that ED may have taken the placard top speed limits of the F-15 airframe and used that as data for the modeling of the max thrust of the F-15 engines. Possible?

[Yo-Yo]

It comes down to this: Either Rhen is a liar or LOMAC is completely ludicrous in F-15 velocity/drag modeling. Personally, I think Rhen has never presented anything that even begins to make himself less than 100% trustworthy. But Ed has seemed to base their modeling on data that they don't fully comprehend.

 

It seems to me that somebody else can not comprehend it.

Feel free to do the same Russian crytics do: if you want to proove that something is wrong in Lomac please MAKE YOUR OWN INVESTIGATION.

 

"Kakie vashi dokazatel'stva?" :)

 

We all understand that it is not so easy as to write to the forum. It requires more time. It's necessary to maintain profiles, perform pure sustained turns, generalize your test data, etc. It's necessary to know HOW TO calculate your test results to compare with Dash 1.

 

Otherwise there is no sense to fish in the air.

[Pilotasso]

Im all in favour to fix all aircraft. But to me and for now it would sufice to fix drag factors for weapons they carry. No one would have opened this thread if we didnt require to afterburn to keep level flight up high. I think there is no point to exarcebate positions because then no one will be willing to hear the other side.

[Yo-Yo]

Im all in favour to fix all aircraft. But to me and for now it would sufice to fix drag factors for weapons they carry. No one would have opened this thread if we didnt require to afterburn to keep level flight up high. I think there is no point to exarcebate positions because then no one will be willing to hear the other side.

 

I agree.

The weapons drag was not tuned accurately because there are no accurate data when databased was created. Now we have more data and this issue have to be fixed. But please be patient because it requires much more working time than one plane tuning.