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Old 11-16-2014, 05:16 AM   #1
mytai01
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Default 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?
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Old 11-16-2014, 05:35 AM   #2
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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.

Last edited by LJQCN101; 11-16-2014 at 03:46 PM.
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Old 11-16-2014, 01:03 PM   #3
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http://forums.eagle.ru/showpost.php?...&postcount=285
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Old 11-16-2014, 02:12 PM   #4
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Nice read Esac_mirmidon.

Quote:
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.

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

Last edited by LJQCN101; 11-17-2014 at 01:40 PM.
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Old 11-16-2014, 06:01 PM   #5
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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.
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Old 11-16-2014, 07:16 PM   #6
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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?
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Old 11-16-2014, 07:35 PM   #7
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Quote:
Originally Posted by Ironhand View Post
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.
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Old 11-16-2014, 09:01 PM   #8
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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.
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Old 11-16-2014, 09:27 PM   #9
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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.
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Old 11-16-2014, 10:13 PM   #10
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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.
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