Degraded Su-27 aerodynamic lift - ED Forums
 


Notices

Closed Thread
 
Thread Tools Display Modes
Old 02-08-2018, 03:58 PM   #1
Maverick Su-35S
Member
 
Maverick Su-35S's Avatar
 
Join Date: Sep 2014
Posts: 324
Default Degraded Su-27 aerodynamic lift

Hello,

After some update (don't know in which one), changes have been made to both the F-15 and Su-27 in terms of aerodynamic simulation (lift capabilities being easier to spot).

Initially (after the PFM came out), both the F-15 and Su-27 were capable of achieving quite authentic turn rates compared to the real planes (of course, depending on IAS and weight). The F-15 only had some critical AoA handicap (initially, now is better) as the plane's lateral-directional control was almost impossible to attain above 20 AoA (30 on the F-15's in cockpit indexer), while the Su-27 was worked quite well from the start in this area.

For whatever reason, after later updates (didn't stand to test aerodynamic parameters after each update) the Su-27's wings produce a quite lower lift for a given AoA (lower lift slope) while the F-15 does exactly the opposite.

Now, (a bit absurd one will find it), the F-15 turns better than the Flanker at both low (full aft stick full AB) and high speeds (around the best turn corner). For short, with both planes fueled the same (30% fuel), the F-15 completes the fastest (full aft stick from around corner speed) 360 turn in about 14.4 seconds, while the Flanker in no less than 15.8. How did this happen?

Here is a track and some output data from it:

Su-27 turns badly after latest updates.trk

Click image for larger version

Name:	F-15 lifting performance (turning capabilities).jpg
Views:	439
Size:	575.4 KB
ID:	178378

Click image for larger version

Name:	Su-27 lifting performance (turning capabilities).jpg
Views:	412
Size:	539.2 KB
ID:	178379

And here's a video of the Su-27's proven turning capabilities:
https://youtu.be/6mOAkNC3GSc

Aerodynamic modelers, can you please tell us what's going on?

Kind regards!
__________________
DCS modules owned: all, regardless of the fact that some are still a WIP and don't deserve 10 bucks!

When you're out of words when discussing something, let the maths talk for you.
I have an insatiable passion for helping simulated aircraft fly as real as possible.
Sincerely, your flight model fanatic!

Last edited by Maverick Su-35S; 02-13-2018 at 02:43 AM.
Maverick Su-35S is offline  
Old 02-08-2018, 04:32 PM   #2
Ironhand
Veteran
 
Ironhand's Avatar
 
Join Date: Aug 2004
Location: New Hampshire, USA
Posts: 3,730
Default

Haven't noticed any loss in performance myself except that temperature now has an effect on available thrust at lower altitudes. But this should effect on the F-15 similarly. Then again I also haven't been specifically testing for anything either.
__________________
http://rsoro.host22.com/Flankertraining_Images/Flankertraining_Banner-1a.jpg

Win 10 Pro x64, ASUS Z97 Pro MoBo, Intel i7-4790K, EVGA GTX 970 4GB, HyperX Savage 16GB, Samsung 850 EVO 250 GB SSD, 2x Seagate Hybrid Drive 2TB Raid 0.
Ironhand is offline  
Old 02-08-2018, 05:17 PM   #3
opps
Junior Member
 
Join Date: Nov 2012
Posts: 62
Default

Your graph shows quite impressive lift for Su-27.(24deg/s at 550km/h)
Try to use Stick Deflection Limiter Override( Y is default).
Su-27's FLCS only allows very slow onset G so there may be problem.

Last edited by opps; 02-08-2018 at 05:21 PM.
opps is offline  
Old 02-08-2018, 05:45 PM   #4
toutenglisse
Member
 
toutenglisse's Avatar
 
Join Date: Jun 2016
Location: French Alps
Posts: 374
Default

opps I bet you're right.
But personnaly I won't use the override, because since last update from 02-06-2018, I can break my Su-27 wings in a hard turn without it ^^
__________________
Hardware : I7 7700K - Z270 gaming M5 - 32GB ( 4x8 ) ddr4 3200Mhz - 1080Ti gaming X - SSD M2 - TM Twcs / TM Rgt yaw pedals / MS sidewinder FF2 - Oculus Rift CV1.
toutenglisse is offline  
Old 02-08-2018, 07:44 PM   #5
proletariat23
Member
 
Join Date: Feb 2017
Location: CA
Posts: 127
Default

only red air that ever worked well for me was mig29.

su family all flamed out with nose down attitude, very nose heavy aircraft, into inverted flat spin death. also had problems with wings ripping off and rear stabs dying when a little rudder applied.

Shes made of glass, or I need more practice, maybe a bit of both. its interesting to see your graphs. the flanker should crank the eagle in comparison, but I can't say if its slow or fast contrasting IRL.
proletariat23 is offline  
Old 02-08-2018, 07:53 PM   #6
Sweep
Senior Member
 
Sweep's Avatar
 
Join Date: Apr 2015
Location: Your Left 7 @3,000ft
Posts: 1,280
Default

Quote:
Originally Posted by proletariat23 View Post
only red air that ever worked well for me was mig29.

su family all flamed out with nose down attitude, very nose heavy aircraft, into inverted flat spin death. also had problems with wings ripping off and rear stabs dying when a little rudder applied.

Shes made of glass, or I need more practice, maybe a bit of both. its interesting to see your graphs. the flanker should crank the eagle in comparison, but I can't say if its slow or fast contrasting IRL.
Right control + enter and a lot of trim change in pitch/AOA changes.

As for cranking Eagles...Think combat configurations.
__________________
"Salt Shaker" - Long live v1.2.2, home of the 10 minute flight
Sweep is offline  
Old 02-08-2018, 08:02 PM   #7
Maverick Su-35S
Member
 
Maverick Su-35S's Avatar
 
Join Date: Sep 2014
Posts: 324
Default

Quote:
Originally Posted by opps View Post
Your graph shows quite impressive lift for Su-27.(24deg/s at 550km/h)
Try to use Stick Deflection Limiter Override( Y is default).
Su-27's FLCS only allows very slow onset G so there may be problem.
I know what you are talking about with the G limitation, but this is not the problem. If people still can't see the difference between the initial PFM and the latest updates, I have to detail things a bit more thorough.

24deg/s at 550km/h with 30% fuel is impressive? Then what do you say about the F-15, did you look at it? Sorry, but you prove to not know how these values are in reality.
__________________
DCS modules owned: all, regardless of the fact that some are still a WIP and don't deserve 10 bucks!

When you're out of words when discussing something, let the maths talk for you.
I have an insatiable passion for helping simulated aircraft fly as real as possible.
Sincerely, your flight model fanatic!
Maverick Su-35S is offline  
Old 02-08-2018, 08:09 PM   #8
Sweep
Senior Member
 
Sweep's Avatar
 
Join Date: Apr 2015
Location: Your Left 7 @3,000ft
Posts: 1,280
Default

Why 30%?

Is that what the real charts are for (obviously, the ones available!)? Haven't looked at the Flanker charts in a while...
__________________
"Salt Shaker" - Long live v1.2.2, home of the 10 minute flight
Sweep is offline  
Old 02-08-2018, 08:16 PM   #9
Maverick Su-35S
Member
 
Maverick Su-35S's Avatar
 
Join Date: Sep 2014
Posts: 324
Default

Quote:
Originally Posted by proletariat23 View Post
only red air that ever worked well for me was mig29.

su family all flamed out with nose down attitude, very nose heavy aircraft, into inverted flat spin death. also had problems with wings ripping off and rear stabs dying when a little rudder applied.

Shes made of glass, or I need more practice, maybe a bit of both. its interesting to see your graphs. the flanker should crank the eagle in comparison, but I can't say if its slow or fast contrasting IRL.
Su-27/33s don't flame out cause of attitude angles, if this is what by mistake you refer to, but below a given G-load, no matter the plane's orientation from the Earth. Nose heavy? Just the opposite. If it would be nose heavy then it couldn't reach high angles of attack, maybe not even reach the critical AoA (less to say the supercritical). Sorry, don't look bad at me, but you have to learn / understand a bit of flight dynamics. The plane's CG (center of gravity) seems realistic where it is, the only problem that comes on when you push the stick until reaching an AoA below -20 is that the elevators become shadowed (turbulent and inefficient airflow) by the wing due to the relative position between the wing and elevators in the plane's vertical plane. The way to get out of the negative deep stall is quite simple, but you need a bit of altitude (at least 2000 meters). Set the controls to direct pitch (needed for high alpha or cobra), fully pull the stick and wait until the AoA goes as much negative as it can get, then release it to neutral once the AoA wants to reduce. If the AoA managed to get below -20, pull the stick and get out of this unstable region. If not, repeat the process..., full stick pull until the AoA reaches a maximum negative value, then release until it drops to below -20.

On the other hand, yes, the Flanker won against the Eagle in real tests and beat it in turns. The Eagle had an impossible chance to stay or get behind the Flanker. Now (after latest updates) in DCS we see the opposite, so we need a fix.
__________________
DCS modules owned: all, regardless of the fact that some are still a WIP and don't deserve 10 bucks!

When you're out of words when discussing something, let the maths talk for you.
I have an insatiable passion for helping simulated aircraft fly as real as possible.
Sincerely, your flight model fanatic!
Maverick Su-35S is offline  
Old 02-08-2018, 08:17 PM   #10
Maverick Su-35S
Member
 
Maverick Su-35S's Avatar
 
Join Date: Sep 2014
Posts: 324
Default

Quote:
Originally Posted by Sweep View Post
Right control + enter and a lot of trim change in pitch/AOA changes.

As for cranking Eagles...Think combat configurations.
Very good pointing! Yes, think combat configuration..., it still beats the Eagle in turns if both have dogfight missiles left (usually those are the missiles they remain with).
__________________
DCS modules owned: all, regardless of the fact that some are still a WIP and don't deserve 10 bucks!

When you're out of words when discussing something, let the maths talk for you.
I have an insatiable passion for helping simulated aircraft fly as real as possible.
Sincerely, your flight model fanatic!
Maverick Su-35S is offline  
Closed Thread

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT. The time now is 08:14 AM. vBulletin Skin by ForumMonkeys. Powered by vBulletin®.
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.