Unable to Supercruise?

[tacoscent 0]

So in my wings over israel game I have used for awhile I have the Mig 31M mod which is my favorite plane. I have modified it to allow it to super cruise at very high speed. Its got insane dry thrust, 170000 per engine, and at 15000 meters could do 1.98 mach at 69% throttle, just shy of the afterburner. However I recently upgraded to Strike Fighters 2, i have put the exact same ini file in the proper folder for this airplane, yet, cannot go beyond 0.97 mach without afterburner.

 

Its rather hilarious that with 170000 dry per engine max, it can only manage 0.97 mach. Yet once the afterburners go to full 225000 each, it will pull past mach 4. What statistic is causing my plane to stop accelerating at .97 without afterburners? It can manage .97 mach at only 35% thrust. But if I increase it to say, 65%, it still doesnt go any faster regardless of altitude, the afterburners need to be engaged for it to go faster.

 

It has to be a difference with the 2 games, since the plane ini files are identical. Thanks.

Edited April 3, 2014 by tacoscent

[Fubar512 1,350]

A more demanding  (and accurate) flight dynamics model, that applies predetermined global parameters to flight models that lack the appropriate tables and data entries.

[tacoscent 0]

So whats the solution?

[Snailman 517]

First, SF1 and SF2 data files are not interchangeable....

 

apart from that.

There are aerodynamic coefficients,  more specifically the drag, which is set to such values that never allow the plane to break a certain value. Even if supersonic drag is low, because of high subsonic drag, the plane can never break the sound barrier. This is a method to create subsonic-only planes (like Yak-38 for example)

 

You can find a list about these values. As FM's are usually editted the simplest way, usually this has been done with CD0 = Zero-lift drag coefficient

CD0MachTableNumData=13
CD0MachTableDeltaX=0.20
CD0MachTableStartX=0.00
CD0MachTableData=0.984,0.9955,1.000,1.052,1.676,4.589,1.232,1.129,1.107,1.050,1.015,1.016,8.145

 

This means, the table has 13 values, each value means 0.20 mach speed increase, from zero.

So you can count, between 1 and 1.2 machs, the CD0 is 3 times more, and at 2.8mach 7 times more. So this plane, depending on engine power has low acceleration when breaching 1Mach especially at low altitude - and it cannot break 2.8M at any circumstance. (it's a Flagon, and it cannot reach that speed anyway with the current engine power)

So take a look at this value at each aerodynamic part of the plane, and experience with them. But keep in mind setting realistic values needs proper skills (in physics for example)))  and tech data, too.

[tacoscent 0]

Thank you for the help snailman, unfortunately I have no skills in the phsics department, and I never understood all those values.

 

This is from the mig 31m fuselage.

 

CD0MachTableNumData=8

CD0MachTableDeltaX=0.40

CD0MachTableStartX=0.00

CD0MachTableData=1.274,1.000,0.826,2.241,2.497,2.315,1.996,1.996

 

Of course there are more values on the other parts, but I figured I would start with this. I'll be honest I still dont really understand what the values in the machtabledata mean, and what each one signifies, and what changing the first value from say, 1.274 to 1.5 would do. 

 

If you wanted to make the mig 31 do mach 2 without afterburner, what would you change?

 

I notice the values are lower on this one, CLA.

 

CLaMachTableNumData=7

CLaMachTableDeltaX=0.40

CLaMachTableStartX=0.00

CLaMachTableData=1.000,1.000,1.000,0.623,0.792,0.914,1.002

 

What is the difference between these two values?

Edited April 3, 2014 by tacoscent

[Fubar512 1,350]

CLa = Coefficient of lift by alpha state. Thus, the CLaMachTable represents how Cla is effected by Mach level.  This should be left alone, as it doesn't effect a model in level flight.

 

CD0 = Coefficient of drag in level flight at zero lift. CD0MachTable represents how that value is effected by Mach level.

Edited April 3, 2014 by Fubar512

[MAKO69 186]

I ran into similar problems when moddin' an A-4K Skyhawk with newer engine w/afterburner. There seems to be some sort of SF2 laws of physics that are etched in stone that can't be broken.

 

http://combatace.com/topic/76629-fa-4k-super-kahu-hawk/

[Snailman 517]

If you wanted to make the mig 31 do mach 2 without afterburner, what would you change?

 

I believe I have seen an SF2 standard MiG-31BM somewhere ( I remember so)... if that flies well, I can modify it for the old one. Take a look at that one. And also there's a MiG-31 in the NATO Fighters 5 mod as well.

 

I did modifications to the Su-11 and the Su-15 family, exactly for the same reason. So it is not a difficult task. But first take a look at these existing versions, before getting into large scale editting.

 

Also keep in mind that reaching 2.8M for the MiG-31 is only possible at optimal height... 50-60K feet

 

Try this, if it works better than the SF1. If not we take a look.

I started some standardization, but due to IRL conflicts I had to suspend all work at the moment((((

[tacoscent 0]

I believe I have seen an SF2 standard MiG-31BM somewhere ( I remember so)... if that flies well, I can modify it for the old one. Take a look at that one. And also there's a MiG-31 in the NATO Fighters 5 mod as well.

 

I did modifications to the Su-11 and the Su-15 family, exactly for the same reason. So it is not a difficult task. But first take a look at these existing versions, before getting into large scale editting.

 

Also keep in mind that reaching 2.8M for the MiG-31 is only possible at optimal height... 50-60K feet

 

Well see, reaching mach 2.8 isn't my issue, the plane actually performs well beyond mach 2.8, once you remove the limiter. I want to keep it semi realistic, so right now I have put a cap on mach 4.1. Beyond that I believe the engines will catch fire and the plane will explode due to too much heat. As long as the plane has enough thrust I believe it will be able to keep accelerating.

 

That isn't the issue. The issue is regardless of what the dry thrust is set to, it will NOT accelerate beyond 0.97 mach, without afterburner, I can set the dry thrust to 1 million in each engine, and it wont go any faster than mach 0.97 without the afterburners. There has to be some value that can be changed, if there isn't well, I guess we can close the book right here.

Edited April 3, 2014 by tacoscent

[MAKO69 186]

Its the numbers on the air on the wings or something, a veritable can of worms.

[+logan4 847]

You can also check these values in the "Flightcontrol"section of your AC_data.ini if you set these.

 

MaxSpeedSL=416.67   <- even with full burner you will not able to surpass it down low, unit is in: m/s

MachLimitDry=1.14      <- controls how fast you can go without burner, unit is in: mach

 

Re: mach4 the MiG31 will have more problems than overheating, structural parts would deform earlier than that.

[Wrench 9,846]

hmm,

"mach 4" Foxhound. sounds like THIS thread belongs in the "What If/Fantasy" category

[tacoscent 0]

That fixed it! Thank you so much for finding the value! I've never seen that one before so I had no idea it even existed.

 

Yeah it probably couldn't take that kind of speed, but if it were reinforced and flew high enough maybe it could? If it were flying above 25000 meters and had enough thrust I'm sure it could go beyond 2.8 mach, the Mig 25 could do 3.2.

Its the numbers on the air on the wings or something, a veritable can of worms.

 

Hey just wanted to double check with you in the aircraft.ini under flight data, there is a mach limiter. If you adjust that and you have enough thrust you should be able to go faster. Doesn't matter what the shape of an aircraft is its like a car if there is enough power/thrust pushing it along you will keep accelerating. This is a game so the stress on the chassis won't be taken into account.

[+Spillone104 553]

Remember that over the CD0 parameters of the aerodynamic surfaces there are others in the engine section. Particulary the DryMachTable and AltitudeTable. They work as modifier of the thrust value respectively by mach number and by altitude. No matter how much powerful the engine is even in dry thrust, if the value drastically drop around mach 1, the aircraft would not supercruise.