Su-27 in departed flight

I've noticed that the Su-27 goes into departed flight even if the ACS is active. I've even done the Cobra with it active. If I force negative g-loading it can depart. Is this correct?

Once for a moment in Multiplayer, I'm at 500kph in a level flight and then pulled into the vertical. The aircraft just overshoots 28° AOA and pitch departure occurs at a speed as fast as 300kph.

EDIT: Sometimes it does, sometimes doesn't. Tried to replicate that but failed.

Nice read Esac_mirmidon.

PD: This explains why when i´m trying to make a vertical tail slide from 0 speed i always enter in a inverted departure. Another thing is the inverted recovery manuever don´t work very often, maybe because i start the vertical tail slide too low or maybe i´m doing something wrong.

As a rule of thumb, if you see or expect rapid pitch-down movements, pull the stick all the way back and use Direct Control Mode to override FCS pitch-up control authority if possible. Then inverted departures can be well avoided. :thumbup:

Ref Su-27SK manual (some kind of translated-by-robot version):

With the pitch angles it is more than 80° (in the position, close to the vertical)

 

to set control stick along the listing to the neutral position, to create the angle of attack of 10°-15° and to maintain it before lowering of the nose of aircraft of lower than the horizon, to collect the velocity of 300 km/h, to execute half-roll and to derive aircraft in the level flight, without exceeding α add.

 

With a drop in the velocity to 100 km/h in the process of lowering nose in the inverted flight position of aircraft it to be sultry tendency toward the transition to the negative angles of attack by the taking of control stick “on itself” up to the complete motion, preserving the angle of attack of 10°-15°.

 

With the speed loss of less than 100 km/h in the process of accomplishing the zoom at the pitch angles of more than 75° the aircraft has a tendency toward a spontaneous increase in the pitch angle, after which follows th lowering of nose (“signaling”) e progressive on the rate with the passage through the perpendicular position and the transition to the negative g-forces. For the transfer into the positive overloads and preventing the development of the inverted spin it is necessary to completely deflect control stick to itself and to hold it in this position before the appearance of the positive overloads. With the appearance of the positive overload ([Pu]=0,5-1,0) to set control stick on the pitch to the neutral position, to increase velocity to the V = 300 km/h and to derive aircraft from the dive, without exceeding α add.

Has anyone run into a departure that was unrecoverable (assuming you had enough altitude under you)? I ask because I spent about an hour this AM trying to force the issue and anything I put myself into--inverted or otherwise--was easily recoverable. The most altitude I lost was about 4000m while trying to make things worse. Finally decided that enough was enough and recovered.

Could you share your departure exit technic please?

I´m always in troubble trying to recover from an inverted departure after a vertical tail slide from 0 speed at idle RPM.

Any minimum altitude to make a vertical tail slide?

Has anyone run into a departure that was unrecoverable (assuming you had enough altitude under you)? I ask because I spent about an hour this AM trying to force the issue and anything I put myself into--inverted or otherwise--was easily recoverable. The most altitude I lost was about 4000m while trying to make things worse. Finally decided that enough was enough and recovered.

If you mean a free fall after a stall then I had a few from 12.000 meters to zero with no chance of a recover.

Some with nose down and some flat inverted.

2 trk files are in the Su27 chitchat thread.

#123 and 124.

I'd also like some tips on recovery, specifically from an inverted flat-spin or deep stall.

I've encountered this seemingly 100% deadly situation a few times, with no recovery possible after pushing the nose over at many varying speeds and altitudes.

After entering this state I've tried:

1.) Full AB, full aft stick with FCS override.

2.) Cut power to idle, full aft stick with FCS override.

3.) Full AB, full aft stick no FCS override.

4.) Cut power to idle, full aft stick no FCS override.

I've attempted all of these with and without aileron, and rudder imputs.

For my testing I've tried to enter the state at 5000m altitude with indicated airspeed of 525kmh each time.

The aircraft seems to recover just fine from any high positive angles of attack just fine even at low speeds, in spins, and highly progressed stalls. However, if I let the nose dip into negative angles the aircraft departs rapidly and does not allow recovery once departed. I've managed to prevent the aircraft fully entering the regime a few times by going full aft stick whilst overriding the FCS and adding power, though again once the aircraft enters the aforementioned inverted regime its usually a good idea to go ahead and depart my ass from the aircraft.;)

Something looks strange to me with these inverted stall depart of Su27.

I think if planes is not in inverted spin but just inverted stall depart it should drop nose by itself without doing any reaction from pilot.

And from inverted spin it should recover using correct procedure.

So i think ivnerted stall depart of Su27 actually in DCS it is probably flight model bug, similar like with sudden negative G push going to inverted with stabilisation ON - i suppose no plane fly like these way.

I've only tried the following recovery methods when I entered the inverted stall/spin above 4000m.

The following methods successfully pitched the nose down to allow build up of air flow over the wing:-

Method #1

1) Throttles idle.

2) Full rudder in opposite direction of spin.

3) Air Brake on.

Method #2

1) Throttles idle.

2) Speed below 300kph

3) Deploy chute!

4) May need to restart engines.

Has anyone run into a departure that was unrecoverable (assuming you had enough altitude under you)? I ask because I spent about an hour this AM trying to force the issue and anything I put myself into--inverted or otherwise--was easily recoverable. The most altitude I lost was about 4000m while trying to make things worse. Finally decided that enough was enough and recovered.

Well, I've gone into the ground a number of times after failing to recover properly from Cobra attempts. In most of those cases though, both engines were stalled out, and on one occasion I was going backwards (don't ask how I managed that because I have no idea).

I think in all the cases where I managed an engine restart I got out o.k.

Wasn't really spinning in any of these cases though, and in a few of them I may have spent too much time trying for engine restarts rather than reestablishing aircraft orientation. I suspect that if I had tried for my relights after getting control of the plane I might have made it out of those ones.

Also, starting altitude was usually between 3000 and 3500 m.

Could you share your departure exit technic please?

 

I´m always in troubble trying to recover from an inverted departure after a vertical tail slide from 0 speed at idle RPM.

 

Any minimum altitude to make a vertical tail slide?

Are you going straight 90 degrees up? It could be why your departing, maybe?

Yes, i´m going to the vertical, idle and let the tail fall down on the vertical and i always enter on inverted departure.

i´m only able to exit the departure 1/5 times stoping the rotation and pulling the stick all the way, then adding RPM and when i´m over 300, half rolling.

I don't know the parameters for a tail slide, but is it 90 degrees up? Should we try 60 see if we can do it, and add 10 degrees until we depart. I am going to try now.

Like I said, I have no idea of the tail slide parameters so not sure if this is correct, please let me know. I think the best looking one was at 70 degrees. I could not keep the 90 degrees and ended up doing a loop.

I tried from 60 to 90 degrees. Almost hit the ground on the first one.

Tne SK manual says cristal clear that this kind of vertical tail slide a 0 speed at the top is one of the situations for a inverted departure.

So...

What is the page number in the SK manual that talks about tail slides? I do not know how to say tail slide in Spanish.

Could you share your departure exit technic please?

 

I´m always in troubble trying to recover from an inverted departure after a vertical tail slide from 0 speed at idle RPM.

 

Any minimum altitude to make a vertical tail slide?

Generally, I'm not fighting the aircraft, just nudging it in the direction it'd like to go. The goal is always to get the nose pointing down long enough for the airspeed to reach about 300 km/hr.

Every departure's different but, in general terms: As I fall off the cliff, I'll pull the throttles at idle, discourage any spin and encourage any dip in the nose. Once I get the nose to dip far enough, I'll let it run and it'll usually pendulum right through until I'm upright. As it starts to drop back, I'll push the stick full forward to make sure it continues the drop. Then go stick neutral before I'm pointing toward the ground--otherwise it'll most probably push through to inverted again. Once I'm pointing toward the ground, I wait for my airspeed to increase and, finally, let the engines spool up as I gently pull back on the stick. I'm usually flying again within 2500m.

If you mean a free fall after a stall then I had a few from 12.000 meters to zero with no chance of a recover.

Some with nose down and some flat inverted.

2 trk files are in the Su27 chitchat thread.

#123 and 124.

I'll look for them. Won't have a chance to view them until Tuesday--unless I catch a break somewhere.

Rich

I´m talking about this.

Sorry for my poor english, probably this maneuver in english uses a different name than Tail Slide

Si, yo entiendo, eso es lo que trate de aser en la "track" que puse. Pero no se que parte de el manual habla de esa maniobra...I don't have spell check for Spanish so hope that makes since.

Page 108

First Paragraph: Entering inverted departure.

Second way: Because speed loose near vertical.

Thanks for the tips Ironhand, now i´m improving my departure technic ¡¡¡ 4/5 times i´m able to exit safe.

 

 

I'll look for them. Won't have a chance to view them until Tuesday--unless I catch a break somewhere.

 

Rich

Thank you Sir!

Just deploy flaps and pull all controls against the spin. Altitude loss of only 2000m.

Thank you Sir!

Took a quick look at the one where you went up to 12,000m and lost it. I took control after you were falling inverted. After falling another 3000m with nothing I was doing having any effect, I decided to pop the speed brake to see if 1) it would either change the center of gravity or 2) act as a small sail ( or whatever). That did the trick. Give it a try. Someone earlier had mentioned the speed brake.

EDIT:

Like I said, I have no idea of the tail slide parameters so not sure if this is correct, please let me know. I think the best looking one was at 70 degrees. I could not keep the 90 degrees and ended up doing a loop.

I tried from 60 to 90 degrees. Almost hit the ground on the first one.

As near as I can tell, to have the Flanker in a perfect vertical orientation, you need to hold 88 degrees on the HUD. When I have some time I want to see if I can tail slide. I always fall off to the front or back.

Took a quick look at the one where you went up to 12,000m and lost it. I took control after you were falling inverted. After falling another 3000m with nothing I was doing having any effect, I decided to pop the speed brake to see if 1) it would either change the center of gravity or 2) act as a small sail ( or whatever). That did the trick. Give it a try. Someone earlier had mentioned the speed brake.

 

EDIT:

 

 

As near as I can tell, to have the Flanker in a perfect vertical orientation, you need to hold 88 degrees on the HUD. When I have some time I want to see if I can tail slide. I always fall off to the front or back.

Thank you so much... I'll give it a try.. or two.... ;)