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marki980908

Aircraft config question

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I have tried editing MIG-29SM from RHS configs a bit to see if I could make it closer to its real world counterpart in regards of speed
I have changed thrust coeficient, now the aircraft goes ~1500 with afterburner and around 1200 when it is off. However takeoff/stall speed changed from 220 to ~500 making it impossible for aircraft to take off 
Edited values:

thrustCoef[]={2.31,2.19,2.09,1.92,1.88,1.75,1.61,1.52000003,1.40000002,1.30000002,1.20999999,1.10000001,0,0,0,0};

My question would be, how does thrist coef even work? I looked into the bohemia description, but I dont really get it, according to this at 0Į thrust would be 2.31? Wouldnt it mean that it would take off waayyy faster instead of not take off at all?

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5 hours ago, reyhard said:

It sounds like you've edited also maxSpeed, is that correct?

That is correct, I have changed it to 1500, later changed it to 2200, however the max speed of an aircraft didnt increase after that.
How did you know? Is stall speed a percentage of max speed?

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19 minutes ago, marki980908 said:

How did you know? Is stall speed a percentage of max speed?

Well, my educated guess is that the higher you make the maxspeed value, the higher (or lower?) you need to adjust the values in the thrustCoef array as each entry corresponds to a % value of thrust energy.  I've been awake since 5am so my few surviving brain-cells cannot "do math" right now...

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48 minutes ago, Jackal326 said:

Well, my educated guess is that the higher you make the maxspeed value, the higher (or lower?) you need to adjust the values in the thrustCoef array as each entry corresponds to a % value of thrust energy.  I've been awake since 5am so my few surviving brain-cells cannot "do math" right now...

Probably, but seeing that RHS F22 has max speed of 2200, and higher thrust coef, I would assume I didnt change it to be too high. I am still confised how stall speed is related to those settings.

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All those large arrays are relative to maxSpeed. Here you can take a look at commented F22 flightModel.hpp https://pastebin.com/6y50e105

Unfortunately, I've removed comments from MiG-29 since I've used Excel spreadsheet to calculate some of the values, which I cannot find at the moment.

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21 minutes ago, reyhard said:

All those large arrays are relative to maxSpeed. Here you can take a look at commented F22 flightModel.hpp https://pastebin.com/6y50e105

Unfortunately, I've removed comments from MiG-29 since I've used Excel spreadsheet to calculate some of the values, which I cannot find at the moment.

I still cant figure out how it works, however I will try copying some of the F22 configs and see what happens

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Okay, so with these settings (F-22):

thrustCoef[] =
		{
			1.76,	// 	0
			1.69,	// 	120
			1.62,	// 	240
			1.68,	// 	360
			1.74,	// 	480
			1.81,	// 	600
			1.89,	// 	720
			1.95,	// 	840
			1.96,	// 	960
			1.96,	// 	1080
			1.92,	// 	1200
			1.4,	// 	1320
			0.4,	// 	1440
			0.0,	// 	1560
			0.0,	// 	1680
			0.0		// 	1800
		};

Soo lets say, I want to increase acceleration, which values would I increase and would it effect my stall speed?

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1 hour ago, marki980908 said:

Soo lets say, I want to increase acceleration, which values would I increase and would it effect my stall speed?


Well, first thing first - acceleration has nothing to do with a stall condition. In this game it was also differentiated. Lift (as a stall is a loss of a lift, generally) is controlled by envelope[] array.
As for increasing the acceleration, yes you can change the thrustCoef array. The numbers to be changed are the ones on the left (green), the red ones are just a reference speed (commented by //) as the array is divided in the range of 0-150% of max speed with 10% increment (in steps of 120 up to 150% which is 1800, which also indicates the max speed is just around 1200 in this array). One note tho - according to the example array posted above you will never reach a speed of 2200 kph if you have no thrust available at a speed of 1560 kph and above (unless in a prolonged dive). Also, your array should end at 3300 kph, in 220 kph steps.
By the way, the thrustCoef is a name that is somehow misleading. It's not like you have more power in AB at speed of 960kph (1.96) than at speed of 240 kph (1.62). Instead, the drag is higher when a plane is going faster, and to ensure a proper acceleration of a plane until the thrust is gone (no more acceleration) we have the thrustCoef here. This way we can model semi-realistic drag coefficients after passing a sound barrier as well, as described here:
https://aviation.stackexchange.com/questions/64307/acceleration-of-a-supersonic-aircraft-after-breaking-the-sound-barrier

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Hm something like this (not tested):

thrustCoef[] =
		{
			1.76,	// 	0
			1.69,	// 	220
			1.62,	// 	440
			1.68,	// 	660
			.
			.
			.
			0.25,	// 	2200
			.
			.
			.
			0.0		// 	3300
		};

Also, bear in mind that thrustCoef being dealing with drag have to be cross-checked against all "drag" coefficients you might add to the plane configuration like gear, speed brakes and flaps ones.
PS. I use 12.5% increment instead of 10% as described here: https://community.bistudio.com/wiki/Arma_3:_CfgVehicles_Plane_class_config_reference#thrustCoef
but maybe the 10% steps work, never personally tested it.

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11 minutes ago, NightIntruder said:


Well, first thing first - acceleration has nothing to do with a stall condition. In this game it was also differentiated. Lift (as a stall is a loss of a lift, generally) is controlled by envelope[] array.
As for increasing the acceleration, yes you can change the thrustCoef array. The numbers to be changed are the ones on the left (green), the red ones are just a reference speed (commented by //) as the array is divided in the range of 0-150% of max speed with 10% increment (in steps of 120 up to 150% which is 1800, which also indicates the max speed is just around 1200 in this array). One note tho - according to the example array posted above you will never reach a speed of 2200 kph if you have no thrust available at a speed of 1560 kph and above (unless in a prolonged dive). Also, your array should end at 3300 kph, in 220 kph steps.
By the way, the thrustCoef is a name that is somehow misleading. It's not like you have more power in AB at speed of 960kph (1.96) than at speed of 240 kph (1.62). Instead, the drag is higher when a plane is going faster, and to ensure a proper acceleration of a plane until the thrust is gone (no more acceleration) we have the thrustCoef here. This way we can model semi-realistic drag coefficients after passing a sound barrier as well, as described here:
https://aviation.stackexchange.com/questions/64307/acceleration-of-a-supersonic-aircraft-after-breaking-the-sound-barrier

The reason why I mentioned stall is because I edited (increased) thrustcoef and max speed and stall speed went from 220 to 500. Thats why I mentioned it.
Ohh okay I think I get it, but than why is there coef for more than 100% of thrust, how do you go 110%-150%?
 

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3 minutes ago, marki980908 said:

The reason why I mentioned stall is because I edited (increased) thrustcoef and max speed and stall speed went from 220 to 500. Thats why I mentioned it.
Ohh okay I think I get it, but than why is there coef for more than 100% of thrust, how do you go 110%-150%?
 


That's interesting findings, I would never say it has anything in common 🙂 Anyway, I would go with whatever I would discover in test flights then. But I rather keep the numbers low and close to 0 above the 100% speed just to make sure I can reach the max speed anyway.

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8 minutes ago, NightIntruder said:


That's interesting findings, I would never say it has anything in common 🙂 Anyway, I would go with whatever I would discover in test flights then. But I rather keep the numbers low and close to 0 above the 100% speed just to make sure I can reach the max speed anyway.

Does having numbers above 100% prevents aircraft from reaching max speed?

 

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Actually, those numbers should be useless, but I don't know what method the game engine deals with the drag. It might as well be the same as the issue of 

altFullForce 				= 100;  
//Altitude value in meters at which the aircraft starts to progressively lose thrust influence until altNoForce is reached. Below this altitude, thrust influence is always at its maximum. Simulates effect of thinning air on engine performace.
altNoForce 				= 4300;

Some people tend to set the second coef as the real-life max ceiling an aircraft can reach. The problem is, the altNoForce tells us at what altitude there is no thrust available to keep a plane flying. I have never reached the desired altitude if set this way. Always had to set it much higher, as the max ceiling is the altitude a plane can reach while still being able to climb with 100-500ft/min of vertical speed.
Same may go to the thrustCoef and the use of those numbers above 100%. Those 110-150% numbers are perfectly useable and understandable in the case of Aileron or Rudder coefs, but in case of the thrust... oh well, what thrust do you have above a max speed since you cannot reach it? 😉 
I don't know, never really bothered creating a plane 100% exact on numbers, as the plane's simulation in this game is very lacking IMO. But, my suspicions are there might have to be some positive numbers over 100% in the array otherwise, your plane may decelerate while diving at its max speed, instead of accelerating. I would just test different settings in the array if I was in your shoes.
PS. Geeez, I did it again 😉 The short answer is - the higher the number the better acceleration is, so while keeping some high numbers in the speed range of 110-150% should definitively not prevent the plane from reaching max speed, instead it should allow it to go faster, beyond the max speed. This is how I see it.

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I am super confused now, I just tried these values on a shikra

thrustCoef[]=
			{
				1.76,	
				1.69,	
				1.62,	
				1.68,
				1.74,	
				1.81,	
				1.89,	
				1.95,	
				5.96,	
				5.96,	
				5.92,	
				1.4,	
				0.4,	
				0.0,	
				0.0,	
				0.0		
			};	

It barely reaches 900km/h. However when values that start with "5" get replaces with "1", it can reach 1300+

Edit: okay so I found this formula: fSpeed = maxI * (speed / (maxSpeed * 1.5f))
What does "speed" and "f" stand for?

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20 hours ago, marki980908 said:

Edit: okay so I found this formula: fSpeed = maxI * (speed / (maxSpeed * 1.5f))
What does "speed" and "f" stand for?


The notation with the "f" suffix isn't rare among configs so I suppose it's a kind of a unitless coefficient?  The calculation seems to give you the 150% of max speed referenced by the array.
As for speed it may be the speed in a specific increment (one of the points of the thrustCoef curve).
Yeah, it's quite a dumb idea to provide people with counterintuitive examples and tools with no explanations. Oh my BI...

Regarding the stall speed. As Reyhard said, all those large arrays are relative to maxSpeed. You changed the max speed to 2200. So, my guess is your envelope[] also has changed itself into something like this:

envelope[] =
		{
			0,	// 	0
			0.11,	// 	220  = 10%
			0.83,	// 	440
			1.97,	// 	660
			2.42,	// 	880
			2.69,	// 	1100
			3.87,	// 	1320
			5.27,	// 	1540
			6.89,	// 	1760
			8.72,	// 	1980
			9.7,	// 	2200 = 100% (max speed)
			9.6,	// 	2420 = 110%
			9.2,	// 	2640 = 120%
			8.5,	// 	2860 = 130%
			8.2,	// 	3080 = 140%
			8.0	// 	3300 = 150%
		};

Just make sure, the second item in the array (10%) has something above 1 or so (need tests), to allow the plane to start flying at around 220 kph. Obviously, all those numbers below have to be at least equal to the first number that ensures the flyable state of a plane. Example:

envelope[] =
        {
            0,    //     0
            1.11,    //     220  = 10%
            1.83,    //     440
            1.97,    //     660
            2.42,    //     880
            .

            .
            .
            8.0    //     3300 = 150%
        };

 

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2 hours ago, NightIntruder said:


The notation with the "f" suffix isn't rare among configs so I suppose it's a kind of a unitless coefficient?  The calculation seems to give you the 150% of max speed referenced by the array.
As for speed it may be the speed in a specific increment (one of the points of the thrustCoef curve).
Yeah, it's quite a dumb idea to provide people with counterintuitive examples and tools with no explanations. Oh my BI...

Regarding the stall speed. As Reyhard said, all those large arrays are relative to maxSpeed. You changed the max speed to 2200. So, my guess is your envelope[] also has changed itself into something like this:


envelope[] =
		{
			0,	// 	0
			0.11,	// 	220  = 10%
			0.83,	// 	440
			1.97,	// 	660
			2.42,	// 	880
			2.69,	// 	1100
			3.87,	// 	1320
			5.27,	// 	1540
			6.89,	// 	1760
			8.72,	// 	1980
			9.7,	// 	2200 = 100% (max speed)
			9.6,	// 	2420 = 110%
			9.2,	// 	2640 = 120%
			8.5,	// 	2860 = 130%
			8.2,	// 	3080 = 140%
			8.0	// 	3300 = 150%
		};

Just make sure, the second item in the array (10%) has something above 1 or so (need tests), to allow the plane to start flying at around 220 kph. Obviously, all those numbers below have to be at least equal to the first number that ensures the flyable state of a plane. Example:


envelope[] =
        {
            0,    //     0
            1.11,    //     220  = 10%
            1.83,    //     440
            1.97,    //     660
            2.42,    //     880
            .

            .
            .
            8.0    //     3300 = 150%
        };

 

How do you even do those calculations?
Also, I changed my top speed to 1800 and copied the thrustcoef from SU-57 (RHS). So now aircraft flies and takes off at reasonable speeds. However I would like to increase its acceleration and to make it able to actually reach 1800 (currently does 1500). I set last numbers as high as >5. but aircraft now can only reach 900kmph instead of 1300kmph it reached before or 1800 I want it to reach. I am VERY confused by these settings, and how they work together.

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3 hours ago, marki980908 said:

I am VERY confused by these settings, and how they work together.


So am I, after years of modding for Arma, because little is well explained and mostly by modding community rather than by BI (except the scripting part tho). Which is weird, and looks more like shooting oneself in the foot, since modding is something that's been keeping the genre alive for years. Welcome to the Arma modding jungle... I'd suggest joining the arma discord, there are bunch of helpful lads, knowledge in a nutshell.

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8 hours ago, NightIntruder said:


So am I, after years of modding for Arma, because little is well explained and mostly by modding community rather than by BI (except the scripting part tho). Which is weird, and looks more like shooting oneself in the foot, since modding is something that's been keeping the genre alive for years. Welcome to the Arma modding jungle... I'd suggest joining the arma discord, there are bunch of helpful lads, knowledge in a nutshell.

Problem is that I asked for help in discord and all I got was this:  fSpeed = maxI * (speed / (maxSpeed * 1.5f)) without any explonation

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Perhaps, they don't like to do the whole work for somebody? Or maybe they simply didn't know what those variables mean? In any case, you were left with the problem alone. At least, you can do something for the modding community and reveal the true meaning hidden behind the calculation through testing and being questioning 😉 In my opinion, it isn't worth the whole hustle tho, but hey, this is your hobby and your time. Do whatever you damn like to do with it.

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34 minutes ago, NightIntruder said:

Perhaps, they don't like to do the whole work for somebody? Or maybe they simply didn't know what those variables mean? In any case, you were left with the problem alone. At least, you can do something for the modding community and reveal the true meaning hidden behind the calculation through testing and being questioning 😉 In my opinion, it isn't worth the whole hustle tho, but hey, this is your hobby and your time. Do whatever you damn like to do with it.

Problem is that what I want is very simple, to make an aircraft bit faster. And all I am getting while playing with values is it slowing down, literally what ever I do, it slows down. There must be some other kind of value that makes everything go wrong

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