DCS Su-27 sustained turn performance in-game flight test results

[LJQCN101]

Hello guys. Here I present the flight test data of the aircraft's sustained turn performance. Although I did pay a lot attention while testing the bird to ensure the accuracy of the data, don't take it too seriously.;)

 

DATA BASIS: FLIGHT TEST

 

Time of test: Nov. 15, 2014

 

DCSW version: 1.2.11.33921

 

CONFIGURATION: 34% internal fuel, clean aircraft, test conducted below 50m (BARO), MAX AB, standard day (QNH: 760mm HG; Temp: 15° C).

 

Actually I took off with 70% internal fuel and then adjust the aircraft for a stable & constant-speed turn below 50m. Upon reaching 34% fuel, I took a read of the current g-load. One test each for a single number.

 

BTW I used the F-16C Block50 E-M chart as a basis chart to draw the curve. Source: T.O.GR1F-16CJ-1-1.

 

Edited November 14, 2014 by LJQCN101

[rrohde]

For the uninitiated among us, what are we looking at? EL5 terms, please. :)

[LJQCN101]

For the uninitiated among us, what are we looking at? EL5 terms, please. :)

 

Enter the chart with mach number or kph, proceed vertically to desired Ps curve (Ps=0 means sustained turn. The green curve of Su-27 is also a Ps=0 curve.) or the dashed curve which means g-load.

 

And then proceed horizontally to read turn rate. Here you go.;)

[rrohde]

Thank you.

[Esac_mirmidon]

Pretty the same as this russian table.

 

[Shaman]

Pretty the same as this russian table.

 

 

Wow, just wow, good job ED!

[GGTharos]

It's close. The original table is, IIRC, for a Su-27 with 2 R73, 2 R27R and 50% fuel.

 

As you can tell from that table probably, it isn't representing a modern F-16.

[Esac_mirmidon]

Nope.

 

It´s for a F-16A with legacy engine.

[Aerovenator]

I wonder how difficult it is to create this EM Diagrams for myself. How do I have to perform the test flight? Any ideas?

[Mayer]

Hi LJQCN101,

 

It seems what you've done needed of works. thanks a lot.

In order to use corretly the data, could you please explain how to read this document? why example maybe ?

[Ironhand]

Hi LJQCN101,

 

It seems what you've done needed of works. thanks a lot.

In order to use corretly the data, could you please explain how to read this document? why example maybe ?

Look several posts above yours to his response to someone else or simply click: LJQCN101's explanation. Find the airspeed: say "880k/h". Follow the line up to where it intersects the Ps=0 curve for the Su-27 (highlighted as green). Follow the horizontal line to the left and read the sustained turn rate in degrees/second for that airspeed. In this case 21*. Another example: for an airspeed of 400k/h, the sustained turn rate would be 19.1*.

Edited January 16, 2015 by Ironhand

[FLANKERATOR]

Thanks LJQCN101, results look good.

Let us know if you do any further testing.

[Aerovenator]

In order to use corretly the data, could you please explain how to read this document??

 

Take a look at this article:

 

http://www.simhq.com/_air/air_011a.html

[Bourrinopathe]

Thanks a lot for the test LJQCN101!

 

I've highlighted some values on this one:

standard atmosphere used

 

I was interested in the Mach number for the max sustained turn rate.

The highlighted "21°/s" is just a rough value. It's easier to remember.

 

(thanks to Esac_Mirmidon for the original file and information)

[amazingme]

It feels closer than it should be after the latest update.. I'm still being able to pull >15 Gs without the aircraft to break apart but the good news is that you can't pull more than let's say 20Gs..

Did anyone test that yet?

[Robin_Hood]

I wonder how difficult it is to create this EM Diagrams for myself. How do I have to perform the test flight? Any ideas?

 

I did them for the Su-33 a year ago (still WIP version), you can take a look at page 55 (I am aware about the "6 R-27ET" typo) if you want.

 

I am not sure how the OP did it, but here's how I did (BTW, don't expect something easy, especially with the new flight model):

 

1°) For instantaneous turn

 

- disable blackout effects for the testing

- above corner speed, just pull as hard as you can (trying to stay in level flight) and record the Gs you are able to pull at each speed (try to record a good number of data, and make several recordings for the same speeds to ensure an acceptable accuracy)

- below corner speed, this is more tricky, since you have to pull just the right amount to be at your max performance (AoA just under the limit) ; this is more time intensive, as you will lose speed very quickly and have to make a lot of tries (personnally, I paused the game to read Gs and true airspeed in external view)

 

These will give you the the V-n diagram. Then, you can apply the turn rate formula to have the max instantaneous turn rate (see formula below)

 

Example raw data (with fitting curves)

 

2°) For sustained turn

 

- this is even trickier. What you have to do, for each speed you want to record, is to stabilize your aircraft in a level turn with constant speed and therefore constant Gs.

To do this, go in afterburner (I recommand using infinite fuel) and start a level turn and tighten (adjusting bank) it until your speed is stable (because of the energy you bleed while turning). The real tricky part is to keep everything stable for some time: your altitude, bank angle and airspeed must be constant (this will give a sustained turn). Record the true airspeed and G, then (depending on your airspeed and preference) try either a lower airspeed or a higher one (you can use the airbrake to lower your airspeed in some situations).

It is a pretty time consuming task, but will give you data points for maximum sustained turn performance. Then, apply the turn rate formula.

 

The turn rate formula is:

 

TR = 9.81*sqrt(n²+1)/V with n the G-loading and V the true airspeed (in m/s)

 

The background of the EM diagram is made with the same formula, and the one for turn radius = V²/(g*sqrt(n²+1)) for constant G and constant radius

 

Example turn rate raw data

 

For my document, I re-drawed all the curves in vectorial to give a cleaner look.

 

Hope I helped. I have not found the courage to try doing the Su-27 yet.

[LJQCN101]

I did them for the Su-33 a year ago (still WIP version), you can take a look at page 55 (I am aware about the "6 R-27ET" typo) if you want.

 

Hi, sry for late response. I only tested for the sustained turn and did fairly the same as yours.

 

Yeah you have to make a perfect constant-speed level turn and at the same time monitor the fuel state so that you take a read on the G-loading at exactly 34% fuel. (my example)

 

Strongly suggest you give it a try. I didn't find the SU-27 PFM much harder to fly. Just make good use of pitch/yaw trim to help pulling the stick and ticking rudders against sideslip.

 

Regards.

[Robin_Hood]

Personally I used unlimited fuel to avoid inconsistencies. Hopefully it shouldn't cause any difference in the flight characteristics.

 

I still do not have the heart to take on the Su-27 yet. Besides, I am waiting a bit to be sure the PFM is finished and stable.

[LJQCN101]

It's close. The original table is, IIRC, for a Su-27 with 2 R73, 2 R27R and 50% fuel.

 

As you can tell from that table probably, it isn't representing a modern F-16.

 

IIRC the origin table is for a clean Su-27 weighting of 18920kg.

Edited August 23, 2015 by LJQCN101