A10C engine model

[Yo-Yo]

You can use std day or ISA setting - in DCS it means a field near SL and 15C.

[Vitormouraa]

So Yo-Yo, there is no issue? Everything looks right I think

 

Yesterday I was testing the A-10s stall, and it matches to what you said. The ITT reaches 800. AFAIK, it is a function of the external air temperature and etc.

[Raistlen007]

So Yo-Yo, there is no issue? Everything looks right I think

 

Yesterday I was testing the A-10s stall, and it matches to what you said. The ITT reaches 800. AFAIK, it is a function of the external air temperature and etc.

 

I think a major issue with stalls isn't whether we stall at the right speeds but what happens during a stall. Right now in DCS in a stall during a turn the aircraft pretty much spirals out of control with massive wing dip.

 

This might be in conflict with the real aircraft given this excerpt from the flight manual:

 

Aileron and rudder control can be maintained throughout the

stall, provided there is not a large amount of sideslip. Aileron

is more effective than rudder in controlling roll. Control effectiveness

decreases steadily as AOA increases above stall,

and aileron effectiveness also decreases as sideslip increases.

In some cases, aileron effectiveness can be reduced to near zero

when the aircraft is stalled with sideslip present. Yaw can easily

be controlled with rudder. In all cases, drag increases dramatically

as AOA increases above stall.

[Yo-Yo]

So Yo-Yo, there is no issue? Everything looks right I think

 

Yesterday I was testing the A-10s stall, and it matches to what you said. The ITT reaches 800. AFAIK, it is a function of the external air temperature and etc.

 

I think so... :) but playing now with the engine I see that the negative temperature area at SL could be adjusted better, referring to the manual, but this fact does not affect ISA condition from + 35C to -10...15C.

 

It's not a 15 minutes work... the task is very challenging, because in this case the overall set of parameters must be revised... and it's hundreds of numbers that are not directly determine performance and gas parameters. And most of the engine stations parameters are UNKNOWN and I have to pull the sliders only by theory and intuition :).

[Dojo]

I think so... :) but playing now with the engine I see that the negative temperature area at SL could be adjusted better, referring to the manual, but this fact does not affect ISA condition from + 35C to -10...15C.

 

It's not a 15 minutes work... the task is very challenging, because in this case the overall set of parameters must be revised... and it's hundreds of numbers that are not directly determine performance and gas parameters. And most of the engine stations parameters are UNKNOWN and I have to pull the sliders only by theory and intuition :).

 

Yo-Yo, thank you tremendously. The acknowledgement here is genuinely appreciated. May I add, that while I understand this isn't trivial work, and there are naturally other priorities from a dev perspective that may and must supersede this, just the fact that there is some acknowledgement alone is productive for us, the consumer.

 

Stalling at unexpected times, the inability to perform expected climb rates, and execute certain attack profiles in DCS are why this issue is so passionately pursued. This is especially pronounced in Nevada, where the elevation is higher and the temperature is hotter ;) I can't tell you enough how good it feels just to start to have a conversation about this.

Edited August 4, 2016 by Dojo

[bkthunder]

I think so... :) but playing now with the engine I see that the negative temperature area at SL could be adjusted better, referring to the manual, but this fact does not affect ISA condition from + 35C to -10...15C.

 

It's not a 15 minutes work... the task is very challenging, because in this case the overall set of parameters must be revised... and it's hundreds of numbers that are not directly determine performance and gas parameters. And most of the engine stations parameters are UNKNOWN and I have to pull the sliders only by theory and intuition :).

 

Yo-Yo are you saying that you noticed some inaccuracies with the A-10 Engines, or with the atmospheric modelling of DCS? :helpsmilie:

[SCU]

I think a major issue with stalls isn't whether we stall at the right speeds but what happens during a stall. Right now in DCS in a stall during a turn the aircraft pretty much spirals out of control with massive wing dip.

 

Thank you, this is what I'm trying to say.

 

@YoYo, I tried pulling up at 0.75M yesterday, wing dips aggressively before the steady stall tone.

[Yo-Yo]

Yo-Yo are you saying that you noticed some inaccuracies with the A-10 Engines, or with the atmospheric modelling of DCS? :helpsmilie:

 

THe first one - atmosphere is a kind of thing that is basic and well polished.

 

By the way, possibly, I was not clear - the are is ISA -10...15 to ISA +35 temperatures, it means that you can set T from 0C to +50C in ME and be sure in accurate engine performance.

[Yo-Yo]

Thank you, this is what I'm trying to say.

 

@YoYo, I tried pulling up at 0.75M yesterday, wing dips aggressively before the steady stall tone.

 

what AoA in units did you see?

[Vitormouraa]

Wow, I always had that doubt, setting the external temperature to +50°C and still getting good results, the aircraft must have some difficulties to fly when the temperature is too high, and this is exactly what happens.

 

However, if there is any issue, that's up to ED decide, to change or not change anything..

[SCU]

what AoA in units did you see?

 

I believe about 15 units. But it's hard to tell because i need to zoom in on the AoA gauge and make sense at the same time of the stalling behaviour.

 

Anyway I'm trying to test this again right now and will try to figure out some more accurate numbers.

 

EDIT: I just tried this, and as I said it's hard to tell, but as far as I can tell the plane starts to spiral at 0.75M a bit before the AoA gauge reaches 15 units, all before the stall tone sets in. The tones start setting in as the mach number goes below something like 0.71 mach while pulling and the spiralling stops, and the mach does go down really fast at this point.

Edited August 4, 2016 by SCU

[SCU]

Here's the vertical strafe HUD recording I talked about earlier:

 

 

[ame]

[/ame]

 

Now while the mach number is not shown in this video, the airspeeds and slant range to target can be replicated in the sim giving approximately the same mach number while pulling up like in the video. The pilot in this flight has apparently lowered the volumes of the stall tones, the steady one more than the chopped. Notice how when the chopped tone plays the pilot pulls even more without triggering any wing dips or spiralling like what would happen in DCS, which shows how more forgiving the stall behaviour is in the real life A-10. It also seems like the steady tone triggers as his speed increases while his nose is steady on an 80° dive angle (with no pulling or pushing).

 

In DCS, you will do the same pull at the same speed and dive angle and most probably spiral out of control until you relief the stick a bit, all without the stall tone(s).

[NineLine]

If you have time, try and replicate in the sim and show what you are seeing, save and post the track.

[SCU]

If you have time, try and replicate in the sim and show what you are seeing, save and post the track.

 

Sure I'll try it now again and will post it in a bit.

[SCU]

Stall Test.trk

 

The second and third attempts show this behaviour clearly (3 attempts in total). Also I noticed the elevators lose complete effectiveness at about .8 mach that I had to use the speed brakes to lose some speed in order to be able to pull up. I have no clue if this is normal behaviour or not.

[Vitormouraa]

I think you are right about the stall tones, reaching 430 KIAS, and the pulling the stick, I don't hear the stall alarm, but I can easily recover from this high-speed dive, you will lose the control if you dive with 50-60°.

 

EDIT: I tested with a different atmosphere condition, and the aircraft corresponds differently, also when you carry external loads, the recovery is a different. And to lose the control, you need to dive between 60-70, and not 50 as I said, diving with 50°, you can still recover from it easily without any problem.

 

The only problem I see, is the stall stones, I don't hear it when I recover from a dive at high speeds, 420-430 KIAS. I'll test it a bit more, watch the video and try to reproduce that in game.

Edited August 4, 2016 by Vitormouraa

[SCU]

The dive angle itself makes no difference at all.. All it does is get the plane to the .6M+ speeds. What makes the difference is the AoA which is a function of stall, stick pull, and Mach no. which is a stall tone's function.

Edited August 4, 2016 by SCU

[Vitormouraa]

I am talking about the AoA though.. I'm gonna fix it.

 

I used degrees as reference, I should have used AoA as reference, sorry for that.

Edited August 4, 2016 by Vitormouraa

[Jafferson]

I tested the engine today on ground with full trust and zero speed, the temperature is not exceed over 800 °C

I remeber i have read something about ITT max allowable during start and acceleration 900 °C for 12 seconds.

L or R Engine Hot Light Comes on at 880 Degrees... (Caution Light Panel)

I guess a standing hog with full Trust should start burning over time...

When i started flying the A10 i gave not to much Attention about the missing engine heat Management.

But since i Fly WWII planes, it bugs me.

 

Update:

Also i never saw a increase in fan Speed during a dive...

Its literally Full throttle Forward and don't care anymore.

Edited August 4, 2016 by Jafferson

[mvsgas]

I think it looks right, but I think we should standardize the scenario so we can replicate the results across different variables to rule out external factors.

 

Agree. We can't test properly if the environment is a factor (which was also the reason for my last questions, see this post):

http://forums.eagle.ru/showpost.php?p=2864874&postcount=70

 

I did a post all the other parameters I used, do we want to use this parameters?

Correction to original post

I set a mission with a .78 drag index;

At 2000 feet altitude and ambient temp of 15 Celsius and barometric pressure of 1088pa. Fuel was at 37% with a gross weight of 29070. no weapons, no gun ammo and 0 chaff/flare .

I was able to achieve 346 IAS

 

 

You can use std day or ISA setting - in DCS it means a field near SL and 15C.

Is there a specific barometric pressure we should use in DCS ISA?

 

Here's the vertical strafe HUD recording I talked about earlier:

Now while the mach number is not shown in this video, the airspeeds and slant range to target can be replicated in the sim giving approximately the same mach number while pulling up like in the video. The pilot in this flight has apparently lowered the volumes of the stall tones, the steady one more than the chopped. Notice how when the chopped tone plays the pilot pulls even more without triggering any wing dips or spiralling like what would happen in DCS, which shows how more forgiving the stall behaviour is in the real life A-10. It also seems like the steady tone triggers as his speed increases while his nose is steady on an 80° dive angle (with no pulling or pushing).

 

In DCS, you will do the same pull at the same speed and dive angle and most probably spiral out of control until you relief the stick a bit, all without the stall tone(s).

There is so many things we do not know about that video, how can we used it?

 

I think we need to know how many units of AOA pilot was using, aircraft weight, trim, weapons loaded, atmospheric conditions, where the speed brakes open or close, etc.

 

I only see "wing rocking" above 22 units of AOA, where can we find info to compare?

[Aginor]

I did a post all the other parameters I used, do we want to use this parameters?

I'd say yes, if there aren't even better suggestions from ED.

[bkthunder]

I tested the engine today on ground with full trust and zero speed, the temperature is not exceed over 800 °C

I remeber i have read something about ITT max allowable during start and acceleration 900 °C for 12 seconds.

L or R Engine Hot Light Comes on at 880 Degrees... (Caution Light Panel)

I guess a standing hog with full Trust should start burning over time...

When i started flying the A10 i gave not to much Attention about the missing engine heat Management.

But since i Fly WWII planes, it bugs me.

 

Update:

Also i never saw a increase in fan Speed during a dive...

Its literally Full throttle Forward and don't care anymore.

 

That's the thing. 800 seems to be the maximum in DCS, at full throttle. On the real aircraft, 800 is probably reached before full throttle (waiting for confirmation on this from A-10C crew chiefs)

 

@Yo-Yo what is the amount of thrust produced by the A-10C engines in DCS (in standard conditions, full throttle)?

In my opinion it is fundamental to understand if the amount of thrust is the same as IRL, with the ITT being off, or if the ITT being off also means a lower thrust.

[Yo-Yo]

That's the thing. 800 seems to be the maximum in DCS, at full throttle. On the real aircraft, 800 is probably reached before full throttle (waiting for confirmation on this from A-10C crew chiefs)

 

@Yo-Yo what is the amount of thrust produced by the A-10C engines in DCS (in standard conditions, full throttle)?

In my opinion it is fundamental to understand if the amount of thrust is the same as IRL, with the ITT being off, or if the ITT being off also means a lower thrust.

 

Equal ITT does not determine equal thrust (see the real engine records). Thrust for high-bypass ratio engines is more a function of Nf. ITT, in general, it's a matter of efficiency of compressor, fan, turbines.

 

So, playing with efficiency figures adjusting the model or dealing with manufacturing tolerances and wear in the real engine you can see different ITT with the same thrust.

 

I mentioned above that ITT limiter adjustment is a mean to obtain necessary predicted fan speed, i.e. specified thrust.

[Aginor]

Thanks for the clarification, Yo-Yo!

 

As for the fans (since this may be related to fan speed):

Someone (Snoopy I think) mentioned that the hydraulic pressure created by a windmilling engine may be higher than in real life, making some real life emergency procedures not suitable in the sim.

 

Would you also be interested to look into that possible issue if we can dig up more sources for that? And if yes, should we do it here (since it is engine related) or open a separate thread for that?

I guess it is lower priority and I completely understand if you say no, but if you are going to touch the A-10C that would be something interesting for the "hardcore" guys that actually do emergency procedure training.

[mvsgas]

Thanks Yo-Yo.

For those saying the engine are under performing, I am willing to help try to test. But I think we need to test things like maximum speed, take off speed, acceleration speed and forget the ITT. I think the problems lays in understanding the technical manual. I think the stall is another subject all together.

I was looking at the 1A-10A-1-1 last night, specifically the takeoff section. I figure I post the number I got from different table and see if people get the same before we can go test it.

We can set a mission with a .78 drag index at Sochi taking off from the runway, ambient temp of 15 Celsius and barometric pressure of 1088pa. Fuel at 37% with a gross weight of 29070. no weapons, no gun ammo and 0 chaff/flare.

This is strictly from the manual, I have not test it yet nor check them in DCS. I figure lets make sure we are looking at the manual the same way.

I'm, assuming zero degrees of slope on Sochi since I am not sure if slope is modeled. I have to test in DCS see if there is any wind and direction off wind. I mention wind, because in order to send barometric pressure, I think we have to use dynamic weather.

- Takeoff speed = 117 IAS

- Single engine rate of climb with gear down at seven degree flaps 900 feet per minute (fpm), with gear up 1300fpm, with flaps and gear up, 1400 fpm

- Take off ground run zero flaps = 1000 feet

- Take off ground run seven degrees flaps = ~900 feet

- Continuation speed = 110 IAS

- Acceleration check = 93 IAS at 10 seconds

- Predicted fan speed = ~ 82%

- Required fan speed for single engine rate of climb, gear down and seven degree flaps ~72%