Su-27 Flight Model Discussion

[GGTharos]

It does so by basically providing a detent, or kicking the stick back. You can 'pull through' to override, AFAIK.

 

The manual description talks about the SU27 AFCS also providing G limit protection (and AOA protection)

 

In DCS this does not happen and you can pull as much G as IAS permits.

[IvanK]

So does that mean with FF stick you feel this in the Sim ?

[GGTharos]

I don't know the answer to that question. :(

[Valium]

I think I know the answer but tell me if I'm not right.

 

I had many problems to fly Su-27 and I also used not to use trimming ( I was using 'trim reset' any time and I didn't know how to even use it ).

My problems ended partly when I switched off Force Feedback ( I hope you mean Force Feedback when you wrote 'FF' ). I also changed deadzone and curves, and it was even playable but still got some problems like turning backs, etc.

 

I was wondering for a long time what's wrong with that. I wrote what FF excatly is. I turned it on and the plane was harder to playable, I had to change joystick's settings but - guess what - it made this game more realistic. Ironhand helped me a lot and he explained me how to use trimming. Now I must admit it looks completly different than some time ago.

 

My settings :

deadzone - 10

curves - 25 - 30

 

Some people wrote that they'd other settings but I checked it and I prefer mine. It depends on joystick in my opinion. I've got Logitech Attack 3.

 

 

 

 

Sorry for my English. I won't even wonder if it is incomprehensible.

[DarkFire]

I just watched a 2 hour film about the Su-27 on YouTube. Not sure how authoritative it is, but it seems to be fairly good as it includes interviews with some of the aircraft designers etc.

 

Starting at just after the 1 hour 5 minute mark there's a very interesting section all about the dynamic instability of the Su-27 and the "fly-by-wire system" as Sukhoi implemented it.

 

[DarkFire]

The manual description talks about the SU27 AFCS also providing G limit protection (and AOA protection)

 

In DCS this does not happen and you can pull as much G as IAS permits.

 

I vaguely remember reading in the old Su-27 Squadron Commander Edition days (~1999? 2000?) that the pilot can apply an additional 9kg (or was it 19kg) of force to the stick to deliberately exceed the G or AOA limited imposed by the control system. Obviously the FC3 Su-27 can't really replicate this.

 

I wonder if 'normal' Russian front-line fighter pilots are instructed never to disengage the FCS, or are they all trained to carry out manoeuvres like the kobra and bell?

[Valium]

Good to know it but it seems to me that now all Su-27 have fly-by-wire. Once I read something about it.

[Valium]

Ahh.. OK. If your nose is that high at 320 km/hr, then I think you must be coming in too shallow...or flaring too much just before touching down. IF you'd like, post a track of your landing and I'll take a look at it.

 

IIRC, the gear can go down anywhere under 500 km/hr. I think that's the real life cutoff point.

 

[EDIT]I'm very light in this example, but if you fast forward to the end, you'll see what things look like in my HUD (and from the outside as well) as I'm landing:

 

 

[/EDIT]

 

 

I saw this video once and I was wondering how it's possible this plane looks to be really stayable. I haven't know it's yours.

 

So you've got 2-3 deadzone and +20 curves.

 

I'll check it once again.

[Ironhand]

I just watched a 2 hour film about the Su-27 on YouTube. Not sure how authoritative it is, but it seems to be fairly good as it includes interviews with some of the aircraft designers etc.

 

Starting at just after the 1 hour 5 minute mark there's a very interesting section all about the dynamic instability of the Su-27 and the "fly-by-wire system" as Sukhoi implemented it.

 

That was part of a longer series on the Su-27 wasn't it? Or am I thinking of something else. The entire development history of the Flanker is fascinating stuff.

 

 

I saw this video once and I was wondering how it's possible this plane looks to be really stayable. I haven't know it's yours.

 

So you've got 2-3 deadzone and +20 curves.

 

I'll check it once again.

Sorry it's taken so long to respond. It's tax time in my country and figuring all of it out and filling in the forms took some time. :)

 

Hopefully by now you're on your way to smoother flight.

[DarkFire]

That was part of a longer series on the Su-27 wasn't it? Or am I thinking of something else. The entire development history of the Flanker is fascinating stuff.

 

I think the video I linked is the full version, there are a few shorter 30 minute segments.

 

I'm trying to look for a good book on the Su-27 but can't find one...

[Ironhand]

I think the video I linked is the full version, there are a few shorter 30 minute segments.

 

I'm trying to look for a good book on the Su-27 but can't find one...

Ahhh...that must be it. I was thinking of the shorter segments of it.

 

Not sure what would be a good book. Some are extremely expensive but that doesn't mean anything necessarily. A lot of the books you find are going to be long on pictures and extremely short on deep, accurate information.

[Bourrinopathe]

Good reads on the Su-27 are very hard to come by if you're after technical information and precise flight characteristics. I'm not even thinking about the avionics ;)

 

Speaking about big pictures and tiny descriptions, but still interesting: Sukhoi Su-27 Walk Around No. 47 by Squadron Signal Publications is a pleasant read with tiny details:

The main wheel well of an Su-27 Flanker-B is painted Gray. All Soviet

fighter aircraft have the fuel lines painted Yellow, a holdover from the World War II

German Messerschmitt Me 262 The German Luftwaffe painted all fuel lines in

their jets Yellow. The tubes and the winng are part of the electrical and hydraulic

systems. (Jens Schymura)

Pretty expensive for the content, so it's more like a pretty book for the collection.

 

I think the one by Yefim Gordon is also a classic (2007). It's about the history and the Su-27 family. Not heavy on the technical data.

 

Also: Air Power Australia has some very good articles.

(it may be the closest thing to what Jane's was)

 

And there's the Su-27SK Flight Manual around.

[Esac_mirmidon]

Don't take Air Power Australia as a reliable resource of anything.

[Bourrinopathe]

Oh ok. Was there some kind of controversy or doubtful analysis?

I thought (and hoped) it was well documented (and sourced). I'll push the criticism-throttle, just in case ;)

Thanks for the input.

[GGTharos]

Copp has a specific agenda: He wants Australia to buy F-22's, not F-35's. He hates that he started a company to repair F-111's, but the gov't decided to scrap them and ... go for F-35's :D

 

Basically, if it isn't an F-22, then everything that's Russian made will completely dominate it - that's his slant when he writes these things.

 

It's also known for a fact that he likes to double Russian missile ranges, despite what we see in actual combat manuals.

 

Russian data-links - awesome, can find F-35's and clobber them. Western datalinks - wait what? The west has data-links? Naaaah :D

 

You get the idea. You can get some good info from APA, you just have to be careful and think about what you're reading a bit.

 

Oh ok. Was there some kind of controversy or doubtful analysis?

I thought (and hoped) it was well documented (and sourced). I'll push the criticism-throttle, just in case ;)

Thanks for the input.

[Loaded_Dice]

I have started playing DCS again after a longer break and while I must admit that although the new Su-27 FM is much more convincing there are a few quirks I doubt are like that in real life:

 

- The plane can depart into an unrecoverable spin, apparently when the wing tanks are still not empty (above 5200kg fuel left). If it enters a pitch oscillation no matter what you do there is no chance to recover it (one thing I didn't had time to try is to enable Direct Control Mode). Have to say this only happened once while vertical maneuvering with some drones in the Georgian campaign.

 

- Always enters an inverted spin when trying to do the tailslide maneuver. This does not appear to happen on airshows :-)

 

- Enabling the autopilot and then disabling disrupts the trim around the pitch axis. However I'm using the MS FFB2 with the sensors taped over so I could release the handle while in autopilot so this might be a controller specific issue.

 

Apart from this the new FM is really great especially at critical regimes and landing.

[Ironhand]

 

- Always enters an inverted spin when trying to do the tailslide maneuver. This does not appear to happen on airshows :-)

...

Only addressing this, it's a matter of pitch angle. The airshow routines use a pitch angle during the climb of 70-75 degrees. Do not exceed 75*. Check out the Flankertraining.com channel on YouTube. There's a replication of the Radom 2013 routine there flown with the sim. It includes the two tail slides made during that show.

Edited April 14, 2015 by Ironhand

[Valium]

I'd like to make a video how I fly Su-27 but I don't know which program is the best to use. I've Fraps installed but it records videos to 20 secounds only and to change it, I would have to pay over 30$.

 

Any idea?

 

To be honest, I see that everything is fine when I'm focused on thing I'm just doing.

 

Can you explain me how auto-pilot excatly works?

I only use these commends :

Alt + 1

H

Alt + 9

But I see there're also other combinations but I don't have enough knowledge to understand what they mean.

[Bourrinopathe]

[APA-Copp]

 

"double Russian missile ranges" ?! Ouch. "Slightly" unprofessional, indeed. :doh:

Thanks for all the details GGTharos. That's helpful. I'll take a pint of salt with the articles I may read here.

 

------

 

v1.2.16.38601 update for the Flanker :

• Gear and speed brake drag is tweaked.
  
• The nozzle automatics is corrected.
  
• Dependence of engine RPM by environmental parameters is corrected.
  

 

That could be interesting.

 

(also: R-27ER/ET. Decreased a weapon system calculated launch range in upper hemisphere. (is there any details?))

[Ironhand]

I'd like to make a video how I fly Su-27 but I don't know which program is the best to use. I've Fraps installed but it records videos to 20 secounds only and to change it, I would have to pay over 30$.

 

Any idea?

 

To be honest, I see that everything is fine when I'm focused on thing I'm just doing.

 

Can you explain me how auto-pilot excatly works?

I only use these commends :

Alt + 1

H

Alt + 9

But I see there're also other combinations but I don't have enough knowledge to understand what they mean.

You can try Open Broadcast. It's for streaming but you can also set it up for recording to your hard drive. I tried using it but kept getting a black screen for the video. But give it a try. It's free.

 

ACS (autopilot) from the manual, not personal experience as I simply don't use it much:

 

• H or LAlt-2 or LAlt-4: All three are barometric altitude hold. (H is the old command that was never removed. One of the others used to be pitch and attitude hold. But that's gone now. I used to use it to hold a stable climbing or descending turn.)
  

• LAlt-1: Attitude hold. It'll hold your nose's pitch as long as you are within 8* of bank and on a stable heading
  

 

• LAlt-3: Level to the horizon. I think in this one you can bank and/ or climb but the aircraft then returns to level flight with a neutral stick. (I haven't really played with this one myself. I'm just trying to decipher the description in the manual.)
  

 

• LAlt-5: Radar Altitude Hold. Can be engaged when less than 1000 meters above ground level (AGL). If you get too low, it'll pitch you up. At low altitudes, use it very carefully. It's not designed to pitch you up in time to clear mountains or even large hills.
  

 

• LAlt-6: Route Following Mode. Just that. It'll follow the programmed navigation route course lines.
  

 

• LAlt-9: Turns off the current mode.
  

Edited April 14, 2015 by Ironhand

[Valium]

Oh wow, I didn't expect that.

I'm going to check it.

[Ironhand]

 

• LAlt-3: Level to the horizon. I think in this one you can bank and/ or climb but the aircraft then returns to level flight with a neutral stick. (I haven't really played with this one myself. I'm just trying to decipher the description in the manual.)
  

 

On rereading this, I think this is the old "Panic Mode". It'll return you to level flight regardless of your attitude. Don't know if this is still the case but, at one time, it would pull you out of an inverted dive and back to level flight given enough altitude.

[Bourrinopathe]

On rereading this, I think this is the old "Panic Mode". It'll return you to level flight regardless of your attitude. Don't know if this is still the case but, at one time, it would pull you out of an inverted dive and back to level flight given enough altitude.

 

Yes, it's still a fine emergency recovery mode (best placed on the stick like the Su-27 control stick).

It's also a very comfortable "stabilizer" if you need to check the systems on the fly.

The RESET button/mode is its buddy.

If you can afford the buttons your stick, I assume they really reflect how they're supposed to be used with the Su-27 and provide a very comfortable control.

Also, the general autopilot is on a primary trigger.

 

>>> Su-27 control stick configuration <<<

 

------

 

I've just tried the new nozzle "automatics" and taxiing is much smoother. When you raise the RPM to 77% the nozzles partially close but they remain partially closed if you lower the RPM right after (as low as 70%).

It's only a quick test but it feels more comfortable.

 

The new RPM dependence is also a very nice touch. It now depends on the altitude and (presumably) temperature (I didn't have the time to test different temperatures).

At 14000 m the reheat is activated around 95% RPM.

 

(and I just finished the audio on a training mission with the "old" static 69% idle RPM :D - back to the black board then…)

[Ironhand]

Yes, it's still a fine emergency recovery mode (best placed on the stick like the Su-27 control stick).

It's also a very comfortable "stabilizer" if you need to check the systems on the fly.

The RESET button/mode is its buddy.

If you can afford the buttons your stick, I assume they really reflect how they're supposed to be used with the Su-27 and provide a very comfortable control.

Also, the general autopilot is on a primary trigger...

Thanks for the confirmation. :)

 

...

 

(and I just finished the audio on a training mission with the "old" static 69% idle RPM :D - back to the black board then…)

I'd better hurry up and finish grabbing the video I need for the project I'm working on before I install that update. It'll change things. But this is the Beta Update, not the Public version?

[Bourrinopathe]

It's the public release.

(changelog)

 

You'd better not missclick the update invite as soon as you launch DCS ;)

Edited April 14, 2015 by Bourrinopathe