I don’t know where you got such Cm values for the Su-27 at all
Sukhoi Su-27/30/33/35/37 Flanker series & Su-34 Fullback - History, Design, Performance & Dissection
They are in the TsAGI paper, although they are not necessarily specific to the Su-27 but rather to unstable aircraft in general… presumably it is for an Su-27-esque aircraft as that was the design consensus at the time.
The Su-27’s performance is more modest, It is still unclear at what speed it is measured
In the Tsagi papers it is more general than specifically for the Su 27.
Look at where Cm=0 positions. It’s at around 72° AOA, which is more than the known Cm of F-16 (65°), F-18 (56°) or Jas-39 (65°). A modest Cm curve would’t allow a max attainable AOA of 100°.
I agree with MiG_23M that it is for an Su-27-esque aircraft.
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Actually the static margin at low AOA, which most people like to refer to, doesn’t tell much as it is not the whole picture. But hey, you would need a wind tunnel for a whole picture. That’s why it’s fun to do speculations.
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The Su-27’s IRST is underperforming in range quite a lot:
Rough translation:
Detection range for a fighter at max dry thrust with the clear sky in the background from the rear hemisphere with an aspect of 0/4 - 2/4 is about 50 km and 20-35 km with the clouds / sea / earth in the background. For a target in afterburner from the front hemisphere with aspect of 1/4 is 90 - 100 km. The locking range is about 70% of the detection range. The detection range for a full dry thrust target from the front at an angle of 5° - 15° is about 10 km. To ensure higher locking ranges from the front, increase the aspect angle above 15°.
Now, a few notes:
The fraction aspects represent the ratio of the visible length to the full length of the target, which means that the aspect angle is the inverse sine of that fraction.
Spoiler
That is, if we call \theta the aspect angle and R the aspect fraction (say, 2/4), then R = \sin (\theta) and \sin^{-1}(R) = \theta. Thus:
- 0/4 is 0°
- 1/4 is 14.48°
- 2/4 is 30°
- 3/4 is 48.59°
- 4/4 is 90°
For the IRST on the MiG-29, the detection ranges are used for detection and locking ranges in the game. (The manual gives a 15 km detection range for a MiG-21 flying side on), so I guess the detection ranges should be used to configure the ranges for the Su-27’s IRST.
But what is the “fighter” in the manual mentioned? I thought it could be the MiG-21 (bis?), since the MiG-29 manual uses it and the Su-27 is from a similar time frame. However, the F-15 (and sometimes the F-16) is often used for those kinds of things also (R-27T detection ranges, for example). So, what fighter is it?
There is an archived page from NIIP (the manufacturer) about the N001VEP (an upgrade of the N001 present on the Su-27S). It also has the ranges for the IRST, which is slightly upgraded from the one we have in the game. But if you look at the ranges, they match quite well. They also use quite odd aircraft for those tests: the Su-15 for rear aspect detection, and a MiG-25 flying above Mach 2.0 in afterburner for front aspect. This leads me to believe that the data is also relevant for the IRST we have in the game, as those tests seem to be using older aircraft and the ranges match the one in the Su-27SK manual.
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Now, this is how the Cm curve of F-15 would look like considering it’s only able to stabilize at 35+ AOA (45+ units in cockpit). Also a downward slope means it has a positive static margin.
This the difference between a stable design and a relaxed stability design.
I’ll add a few details that may be of interest.
The Su 27 ( the original, not the new versions like the Su 35 etc) is electronically limited to 24AoA (soft limit) and above 28 AoA it is transversely undriveable. The F-16 has a hard limit of 25 or 28 AoA to avoid deep becoming region. The MiG 29 has positive stability but can cobra maneuver and the first version 9-12 had an AoA limit of 27 ( soft limit).
F-15 can’t cobra but can go above 30 AoA.
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Where does this statement come from?
Probably from definition about “deep stall”.
Do we have any reports on the integration status of the IRST rangefinder within the HUD? Based on what I’ve observed, we should be receiving information regarding target altitude/speed, a flight direction vector, along with the IRST elevation set at +30º|-15º.
Can someone make something so gaijin fix the Su-27 so it not break it wings? Seriously 35% to 40% of my death on it are because the Tip of the wing break for Whatever reason…
Thx.
How do you even rip it? I have only ripped once or twice so far (close to 100 matches). Don’t roll when you turn and don’t just yank the mouse when you need to adjust your flight path at high speed, roll in the direction first.
Flanker will rip out over approx. 11G(7.5*1.5) at nominal condition, and that’s historical extreme airframe limit. You better treat it quite delicate than other airframes at highspeed unlike F-15 or MiG-29.
I don’t think G limits decrease based on speed in-game, has very similar maximum overload based on speed to the F-15 irl.
NASA has a nice definition of deep stall.
I doubt it is the case for Su-27. Does the Su-27 has insufficient nose-down control capability at high AOA?
Nicely put, although it is unclear whether the Mig-29 with a normal center of gravity has sufficient nose-up Cm to pull off a cobra, if not at an aft CG. As TsAGI put it, the level of aircraft instability dCm/dCL influences noticeably the maximum AOA.
The AOA limit of F-16 (25.2~25.8° AOA depends on the version of FLCS), is mostly due to insufficient nose-down controllability and the effect of inertia coupling, risking a pitch-up departure. Then there’s the reduced lateral-directional stability and controllability issue at high AOA, also experienced by Mig-29 and Su-27 type of aircraft, as explained by TsAGI.
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It is fixed value indeed, and cuz GJ think critical value is 7.5G than 9G, thy set critoverload value based on 7.5G (can found in FM data/ 1.35m N critoverload)
And i agree 7.5G limit is more reasonable, thus we can not pull more than 13.5G below M0.85 but we can pull exceed 11G easily around M1.0 in game
So as a limitimg value, 11G limit is more suitable than 13.5G