This comment was some time ago, but would you mind sharing which specific pages and what document this is from? @BBCRF We are working on the report to fix the Su-27 now. I hope we can forward these issues.
@unluckyg@DracoMindC@Giovanex05
What we must do is test a larger amount of charts, variables, etc from the manuals to ensure everything matches 1:1. If there is a discrepancy with what is said in the manual and how it performs in-game… it must be documented and compiled into a larger list so we can formulate a report on the issue. Currently we know the issue from datamine, but we are unable to use that to bug report. So we must adjust and collect data.
Once we think there is sufficient data we need to compile it into a singular report. I suggest we start with verifying stall speeds, speed or altitude loss during aerobatic maneuvers, so on. If anyone needs the manuals / charts please let us know so we can distribute them and ensure everyone is able to test.
I’m referring to conditions where no pitch inputs (aka neutral evelator) above stall speed. Su 27 is not “relaxed” stability.
So above stall speed and no input it’s supposed to be rock steady or going to stabilise.
Also to overall FM in game slower you go more evelator input you need to keep AoA. In some jet in game it’s opposite… And some prop like MB5 and some Spitfires
It’s commonly due to the aerodynamic center being shifted forward as the elevator is shadowed by the separated flow from the stalled wing and the fuselage, usually above 40 deg AOA. This causes the static margin being reduced to negative as the more AOA you gained, the more pitch-up moment is generated, resulting in an uncommanded pitch-up even with a neutral elevator. The reduced static margin also contributes to the Cobra maneuver.
You can check it from the Cm curve of a neutral stab. The static margin is indicated by the slope (derivative) of the neutral stab Cm curve. Examples of F-16 and F-18:
A boresight acm mode for the 27 would be nice. As it is right now the vertical scan scans too slowly and the hmd sometimes locks, sometimes doesn’t. I’ve missed numerous r-27er opportunities due to clunky radar controls. A small constantly scanning boresight mode like in the f-15 and the mirage would help with quick target acquisition a lot. Especially in these 16v16 matches.
And if we’re to talk about real life accuracy of this mode existing, well it does exist, in fact it’s the primary ACM mode on flankers. And also you know, the flanker is supposed to have about 500 rounds of ammo, not 150, but no one talks about that.
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.
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…
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.
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.
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…
