What's with the slow stabilizer lately?

I will use the payload and fuel indicated in the aerodynamic graphics tests i have for the Su-27. But as you can see is NOWHERE NEAR 28º/S. Its about 22º/S.

I will use de payload and fuel indicated in the aerodynamic graphics tests i have for the Su-27. But as you can see is NOWHERE NEAR 28º/S. Its about 22º/S.

 

Roger that. What is the fuel load on that chart?

2xR73 + 2XR27 + 50% internal fuel i think.

I need to check it.

Quick test.

50% internal fuel, 2xR-73 - 2xR-27R.

Max ITR 23.6º/Sec at 6.5G and 580km/h.

Tacview-20171020-163021-DCS.zip.rar

Yeah, I don't see a problem here.

ITR seems reasonable. I did an overlay in a hurry, however Tacview telemetry is inaccurate so aligning for airspeed and load factor vs the hand drawn chart posted above is just about useless.

Now try with the W key...

@Sinusoid (m3 was typo, not energy concertation obviously) No problem here but when I post a book chapter before and get "Huh" that look like trolling. Maybe its all about language barrier here or intonation of written words. Nevermind, all good, dont get me wrong.

My intentions are aimed to clear something out as everyone has different perspective about coorelation of engine power, airplane hydrailics and aerodynamic stability. I like people actually trying to recreate chart behaviour of FM in DCS to figure out some standpoints. Thats good. So lets carry on cos I found this very important topic that has huge impact on plane agility or entaglment in close combat environment.

So, my source says that max instantaneous turn rate of Flanker (at sea level and at 8G) is 28º/s performend in RL. DCS doesnt have stick limiter that can be overriden by brute force so in this test plane has to achieve 8G by using Y(?) key. Right?

That chart line looks like sustained turn rate to me (at R=500m). Can someone translate that from russian?

Next issue: I'm not sure does actual speed of movement of control surfaces (in DCS) is directly coorelated to deflection rates or mean reaction time. That could be a problem here (what you see is not what you get) but, comparing those DCS videos from actual RL videos, faster deflection rate is achieved in RL eversince in DCS that deflection rate is reduced in few latest updates. What you think why?

@Sinusoid (m3 was typo, not energy concertation obviously) No problem here but when I post a book chapter before and get "Huh" that look like trolling. Maybe its all about language barrier here or intonation of written words. Nevermind, all good, dont get me wrong.

.

I get it, now worries.

My intentions are aimed to clear something out as everyone has different perspective about coorelation of engine power, airplane hydrailics and aerodynamic stability. I like people actually trying to recreate chart behaviour of FM in DCS to figure out some standpoints. Thats good. So lets carry on cos I found this very important topic that has huge impact on plane agility or entaglment in close combat environment.

 

So, my source says that max instantaneous turn rate of Flanker (at sea level and at 8G) is 28º/s performend in RL. DCS doesnt have stick limiter that can be overriden by brute force so in this test plane has to achieve 8G by using Y(?) key. Right?.

Where is your source? Please provide one.

That chart looks like sustained turn rate to me. Can someone translate that from russian?

It displays ITR.

Next issue: I'm not sure does actual speed of movement of control surfaces (in DCS) is directly coorelated to deflection rates or mean reaction time. That could be a problem here (what you see is not what you get)

This assumption that visual control surface deflection rates correlate precisely with maneuverability in DCS which then also correlate to real life visual deflection rates vs maneuverability has been wrong from the start. That's what I've been trying to explain.

...

 

That chart line looks like sustained turn rate to me (at R=500m). Can someone translate that from russian?...

 

Can't translate everything. Some of the shorthand is beyond me but here's some of it:

• The chart is titled: Fig 6: Region of feasibility of horizontal maneuvers
  

Here's what else I can decipher:

• Граница установившегося разворота :: The limit for steady turning
   
  
• Ограничение V(?)makc :: V(?)max Limit
   
  
• граница по визуальному контакту :: visual contact limit
   
  
• граница по прочности :: endurance (strength?) limit
   
  
• Полный форсаж :: Full afterburner
   
  
• H= :: Altitude= (I think this last is correct)
  

Quick test.

 

50% internal fuel, 2xR-73 - 2xR-27R.

 

Max ITR 23.6º/Sec at 6.5G and 580km/h.

I must be misreading the chart, I guess. (It's already been a long day and it's only past noon.) Isn't that what the chart says you'll get for that airspeed and G-loading?

The chart stays that is almost 21º/sec at 6.5G and 580 km/h and 21.5º / sec at 850 km/h. So its pretty much the same in DCS. 1.5º sec more.

I can translate the chart:

The upper left Zebra limit line is : Limit by max AoA ( 200 meters )

The other Zebra line that goes to the G scale is: Limit by max G´s.

The continuos line is for the Su-27, the doted line for the F-15, BOTH at Max Afterburner.

Te curves OUTSIDE the max G Zebra line is: Not allowed because out of max G boundaries. ( Literally Limit for Steady Turn )

The vertical Zebra lines to the right side are: max speed at 200 meters. max speed at 3000 meters.

The lines that are crossing the curves ( R-500 R-1000 R-2000 ) are Turn Radious.

And the Chart is MAXIMUM INSTANTANEUS TURN RATE. Not sustained turn rate.

Another consideration, i was testing with the AoA-G limiter OFF:

At Sea level 680 Km/h i was able to reach 28.9º/sec at 9.2G. Like in real life deactivating the limiter allows the pilot to pull more on the stick without the force detent.

The problem is that with the AoA-G limiter off you are OUT OF G LIMITS ¡¡¡

So, its possible to go beyond 22º-23º / sec ITR ( safe max margin ) but you are going to DESTROY the Su-27 if you repeat the same 28.9º 9.2 G a couple of times.

So:

Its possible to go beyond the ITR max value turning OFF the AoA-G limiter but is not SAFE. You can have more ITR ( around 5º/sec more for more or less 3-4 seconds ) but you are overstressing the airframe going beyond the G-AoA limiter, you can enter in departure or stalling the Su-27 and more important you can break the plane. Not to mention it takes AGES to recover the speed if you are in combat.

...

 

 

And the Chart is MAXIMUM INSTANTANEUS TURN RATE. Not sustained turn rate.

 

...

First, thanks for the more complete translations. Looking forward to playing with some of this, if I can find the time.

OTOH, out of curiosity, what are you translating as Maximum Instantaneous Turn Rate? The text I translated (установившегося) does, indeed, translate as "sustained" or "steady" as in "частота установившегося режима" (steady-state frequency). And those lines it indicates look like sustained rate lines.

Is Instantaneous Turn Rate.

This word "установившегося" and the phrase "Граница установившегося разворота" is not about Sustained Turn Rate is for the limits or boundaries of a Steady Turn.

What this means is that if you pass that boundary you enter a " Vibrated Turn, Turbulence Turn or Not Steady turn " You are surpasing max G, and possible, max AoA so you are entering, ( sorry i dont know the technical word in english, maybe is BUFFETING? ) into a shaking flight situation because extreme G-AoA near the departure-stall-over stressing the airframe.

So your plane is starting to shake, vibrate, move, etc, and you are no more in a steady, controlled turn.

Also try yourself but its impossible to keep 580 km/h at 6.5 with full afterburner and at the same time 23º / sec Turn. Or you keep the speed, or the G, but not both. So it must be Instantaneous Turn Rate.

Based on the available ITR data, the FM seems damned close in turning performance with the limiter. The load limit line can be exceeded if you're careful and know what your jet weighs. Also, the chart doesn't display turn rates at very low airspeeds, where the flanker can do some real wizardry.

Pretty close to the real charts. Only a little more ( 1.5º /sec more but maybe i´m doing the test lighter than i should be ).

I testing more things to be completly sure that this chart is ITR and not STR.

So maybe i´m wrong and is Sustained Turn Rate but i dont think so.

PD: I think im wrong. XDDDD.

This chart must be Sustained Turn Rate, Not Max Turn Rate. I was testing more focused in keeping speeds, G, and level flight and i´m matching the chart for Sustained Turn rate almos identically.

DCS Su-27 50% fuel 2xR73 2xR27

400 Km/h and 16.8º

500 Km/h and 18.7º

600 Km/h and 20.3º

700 km/h and 20.1º

800 km/h and 20.8º

All sustained.

So im sorry for any mistake i´d made or wrote.

Is Instantaneous Turn Rate.

 

This word "установившегося" and the phrase "Граница установившегося разворота" is not about Sustained Turn Rate is for the limits or boundaries of a Steady Turn.

 

....

I think I understand...

EDIT: just read your subsequent post. It's a challenge translating a language with which you are not intimately familiar, especially when things get technical, isn't it?

Yes XDD.

But this part is correct.

The translation is more or less over that boundary the Su-27 enters in "buffeting"?. Thats the correct word in english for vibrations because high G-AoA?

What is not correct is that this chart is instantaneous turn rate. It should be Sustained Turn Rate. I´m testing more things to be sure.

Yes XDD.

 

But this part is correct.

 

The translation is more or less over that boundary the Su-27 enters in "buffeting"?. Thats the correct word in english for vibrations because high G-AoA?

 

 

What is not correct is that this chart is instantaneous turn rate. It should be Sustained Turn Rate. I´m testing more things to be sure.

Since I'm not going to have time to investigate myself, I'll take your word for it.

Out of curiosity, though, in your above post (#63), you list some airspeeds and rates. What altitude were you at? I notice that they follow the 200 meter curve line for the Su-27 (which I translated as a sustained turn) pretty closely.

Sea Level, all this numbers are at Sea Level, DCS 1.5.7. 15º Celsius. 50%Fuel 4 missiles. Sustained Turn Rate with Afterburner.

I cant do that on 2.1 because the average height is greater.

Yep, the word you're looking for is buffet. Buffeting can occur in various degrees and can be used to tell you your aircraft AoA just by feel and sound.

As an interesting example, if you have the L-39 you might notice that you can fly it at 1g in various degrees of buffet with flaps up and flaps mid. Flaps full can depart with very little indication.

I already did these tests, initially thinking that the STR was too high ... but it turns out the FM is pretty spot-on for STR, and I've got nothing on Yo-Yo :D

I had to repeat the tests several times until I could get my flying steady enough. Also, thanks goes to Bushmanni for data collection scripts.

Sea Level, all this numbers are at Sea Level, DCS 1.5.7. 15º Celsius. 50%Fuel 4 missiles. Sustained Turn Rate with Afterburner.

 

I cant do that on 2.1 because the average height is greater.

What I'm understanding from the graphics is that the Su-27 has the better instantaneous turn rate, but the F-15 has slightly better max sustained turn rate? I thought that the Su-27 had the better max sustained turn rate....

Also the F-15's sustained turn rate maxes at a lower speed than the Su-27's, which means smaller turn radius... (which is probably an advantage)

But, ignoring max sustained turn rates, the Su-27 has better sustained turn rates at slower speeds... (which is probably also an advantage)

That's what I'm understanding...

Excellent. Thank you. So max instantaneous turn rate occurs at slightly under 600 km/hr with a 9G pull at sea level.

Exactly. But is 8.5G not 9.

Thanks for helping me understand both ITR and STR.

The good thing is that with the AoA- G límiter off im able to reach 29°\sec at 8.8 G at Sea Level. Just like the chart.

But you must be extremly careful because the overstress.

Exactly. But is 8.5G not 9.

My mistake, I misread the number. I thought the number above the 8 was a 0 (=10). Just noticed the small "tail" at the bottom. 9 makes more sense.

The good thing is that with the AoA- G límiter off im able to reach 29°\sec at 8.8 G at Sea Level. Just like the chart.

...

Ah good. You were able to confirm it.

You understand the graph correctly, but what's not known is that the F-15's STR on this graph is over-estimated by about 1deg/s in some places.

What I'm understanding from the graphics is that the Su-27 has the better instantaneous turn rate, but the F-15 has slightly better max sustained turn rate? I thought that the Su-27 had the better max sustained turn rate....

 

Also the F-15's sustained turn rate maxes at a lower speed than the Su-27's, which means smaller turn radius... (which is probably an advantage)

 

But, ignoring max sustained turn rates, the Su-27 has better sustained turn rates at slower speeds... (which is probably also an advantage)

 

That's what I'm understanding...