The chart at the bottom says that :
перегрузки, превышающие ограничения
ηу max=8 при М<0,85; ηу max=5,5 при М≥0,85
overloads exceeding the limits
ηu max=8 at M<0.85; ηu max=5.5 at M≥0.85
Sukhoi Su-27/30/33/35/37 Flanker series & Su-34 Fullback - History, Design, Performance & Dissection
if you have a source on these please make a bug report
I can read your post with understanding. Can do you??
Plane it’s in normal flight godition not extending 5-10 AoA from 300km/h to ~680km/h… With minimal input going suddenly into deep stall condition.
Any way
Just go into game use full controls and check your self or at least compare to other planes…
Again it depends on the game’s coding of the static margin at those specific AOA. The small tail F-16A from the example above has a negative static margin at 0-15 AOA, so it would not be stabilized and sudden pitch departure can happen if no input is given at higher speeds. It’s possible that the Su-27 is given similar static margin in game.
If you don’t think the Su-27 should have such a low static margin then you should report it.
BTW the DCS Su-27 is just a bad example. At the very first release, the dev said the aircraft should exhibit neutral static margin at low AOA, which was the case back then. But with later updates the static margin get increased and increased, and now you can fly the aircraft just fine without the SDU (FBW) as if it’s a stable aircraft.
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The Su-27 is statically unstable in a small speed range, then it is statically neutral
Su-27 is not unstable or relaxed stability…
It’s stable.
With you assumptions and post before after reach +40 AoA Su-27 suppose, after cobra stay in deep stall and it’s not the case. It’s possible to recover within evelator movement.
Also it’s working in both directions of the pitch depends from input it’s going into positive or negative pitch.
Report it… Interesting that any of aviable Su-27 manual for me it’s not mentioned pitch increasing at low speeds…
Do you have a source to prove this or are you gonna keep posting “nuh uh” in response to people when you’re wrong?
I think we can all be sure of the fact that the Su-27 is statically unstable.
If anyone understands Russian, you can go watch this video where this Ukrainian pilot says some things about the su27
(he also says that the su27 is aerodynamically unstable)
the moment he says the su27 is aerodynamically unstable is: 22:50
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The chart at the bottom says that :
перегрузки, превышающие ограничения
ηу max=8 при М<0,85; ηу max=5,5 при М≥0,85
overloads exceeding the limits
ηu max=8 (g)at M<0.85; ηu max=5.5 (g) at M≥0.85
- Maximum operational overloading with the estimated gross weight of 21400 kgf:
− PU max = 8,0 with [M]≤0,85
− PU max = 6,5 with 0,85<[M]≤1,25
− PU max = 7,0 with [M]>1,25
For the weights, which differ from estimated gross weight, the g-force is established from the detachment:
− m•PU max = const = of 171000 kgf with [M]<0,85, but not are more than PU = 9,0
− m•PU max = const = of 139000 kgf with 0,85<[M]≤1,25, but not are more than PU = 7,0
− m•PU max = const = of 150000 kgf with [M]>1,25, but not are more than PU = 7,5
The stability of the Su 27 varies depending on the amount of fuel. Generally speaking, it is stable with larger amounts of fuel, and more destabilised with smaller amounts. It also depends on speed. it is more unstable in subsonic than supersonic.
Without FBW the Su 27 is controllable up to about 10AoA and up to manual speeds. The pilot has to land the aircraft. This also gives the answer to how unstable it is by design. Compared to the F-16, the Su 27 is generally more stable.
It should also be said that the Su 27 is not a pure FbW aircraft, but is a combination of FbW, hydromechanical control and CAS. So it is not an F-16 style aircraft. That’s just to give you an understanding.
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I think everyone but Yoshi was on the same page here, however we are still trying to test the performance in-game. I think it is quite clear the energy loss during turns is too high even though the sustained turns match the known data. Lacks specific excess power.
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Yes I’m in totally different page. Like I’m speaking about apple’s and you about pears.
All planes various stability depending from fuel. It’s just IN comparison to other aircraft in GAME odd to me that we have delta and unstable planes BEHAVING more generally gently at low speed and overall HANDLING is just lest difficult to maintain. IN COMPARISON to unstable by design planes…
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The Su-27 is not stable in practically all ranges of fuel loading
From what little I’ve read about the Su 27, it should be more or less unstable only with a certain smaller percentage of fuel.
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As a curiosity I attach an excerpt from the manual for those who would like to try the AoA characteristics of the Su 27.
"To ensure good maneuverability characteristics over the entire acceptable range of angles of attack at subsonic flight speeds, automatic control systems for wingtips and flaperons based on the angle of attack signal are introduced. As the angle of attack increases, the lateral stability and controllability characteristics remain satisfactory up to α up.
At speeds below 400 km/h and α ≥ 24°, the airplane has reduced lateral controllability. When climbing out of roll at speeds less than 400 km/h while performing maneuvers along the boundary of the ERP response, an angle of attack greater than α dop may occur.
Therefore, when climbing out of a roll, control the angle of attack without allowing αdop to be exceeded.
At angles of attack α > 28° up to stall the controllability of the airplane is absent.
Aerodynamic shaking occurs at angles of attack α=9°-5° at M=0.5-0.9, respectively. As the angle of attack increases, the intensity of shaking increases and stabilizes after Δα=2°-3°.
The nature of the shaking is soft. Over the entire range of angles of attack, shaking does not impede piloting and cannot serve as a warning sign of approaching α extra.
When the wingtip control system is deactivated and fails, piloting is safe and has no peculiarities up to α ∼10°.
Airplane behavior with deflected toes at 30° (landing gear retracted, flaperons retracted) has no peculiarities. Failure of control of the nosings and flaperons at subsonic speeds does not cause aircraft evolutions requiring pilot intervention. The maximum incremental overload at this ΔPu ≈ 0.5. The available roll angular velocity decreases with increasing angle of attack, but remains sufficient up to α extra (more than 20°/sec). The efficiency of lateral control in horizontal flight provides a roll angular velocity ωx ≥ 1.5°/sec.
At takeoff and landing modes with released wing and landing gear mechanization provides angular velocity ω 1.0°/sec.
Characteristics of stability and controllability of the aircraft without hangers and with all variants of missile armament remain acceptable up to angles of attack:
The limit is 24 AoA, you can’t really see it, there’s a green line.
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Everything is wrong.
What does the alignment and control of the wing mechanization have to do with it?
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I don’t know what you’re answering. The description is from the manual and refers to AoA.
Thanks for your contribution to subject.
Now @MiG_23M can we see any documents about instability during subsonic speeds ?? To be at the same page of course.
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Mentioned by Sukhoi themselves on ICAS2002 congress:
• Su-27S/SK basic single seat configuration (typical role is interception) with neutral and small
negative margin of longitudinal stability, maximal Mach number up to 2.3 and airspeed up to 1350 km/h.
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