DarkFire

True, it does need a little finesse for absolute accuracy, but "feet off" is good advice for those suffering from wild rudder gyrations, as seen all too frequently in YouTube videos of Su-27 pilotage. There is a good argument to be made that performing proper co-ordinated turns is part of 'getting the basics right', but I think the default behaviour is close enough that concentrating on other things like maintaining steady altitude in turns is more important to start with :)

This is what you need: The vertical axis is maximum rated G and the horizontal axis is mach number. A couple of things to bear in mind: 1) The graph and the aircraft are calibrated for an all-up weight of 21,400Kg. Heavier will result in lower maximum safe G loading and lighter --> higher safe G loading. 2) Actual airframe destruction will not take place immediately if you exceed the amount shown on the graph. The airframe seems to have a built-in safety margin of between 1.4x and 1.7x (depending on weight & speed) rated maximum G. Destruction of your airframe will take place if you exceed the safety margin. 3) G loading applied slowly is safer than G-loading applied quickly. If you give it time to work the AOA / G limiter will usually prevent you from entering an over-G condition. 4) The Su-27 really, really doesn't like negative G. If you watch videos of real Su-27s the pilots almost always roll inverted & pull rather than pushing over. 5) At the point at which your wing broke it looked like you were rolling as well as pitching. Multi-axis inputs cause significantly higher G than single-axis inputs. Instead of rolling & pulling, roll then pull. One of the few times that the AOA / G limited will not save you is during over-G caused by multi-axis inputs. 6) Feet off the rudder!! The Su-27 performs co-ordinated turns for you. The only time you need to use the rudder is during cross-wind landings.

The over-G warning system, better known as nagging Nadia (probably part of the Ekran system), is calibrated for an all-up weight of 21,400Kg so it'll give you over-G audible warnings based on what it thinks is an over-G condition for that specific weight. When you look at the possible configurations that give you that all-up weight: 1) 2 x R-27ER, 2 x R-73, ~35% fuel. 2) 4 x R-73, ~56% fuel. I'd say that the calibration is fairly obviously aimed at an early-model Su-27 that has PVO (air defence forces) missions in mind. I'm starting to wonder if the Su-27S version that we have in DCS, designed for the VVS (frontal aviation, has A-2-G capability that the standard model doesn't have) might have had a different calibration, or even a basic variable one. The AOA & G limiter in our DCS Su-27 is designed to keep you from over-stressing the airframe and as YoYo pointed out has a certain maximum stress value in mind. It is the case that it will save you at any weight and at any speed unless you're heavy, right in the middle of the 'mach notch' on the max-G diagram and sharply corner the stick (i.e. max deflection in pitch & roll). Different issue: Apologies in advance for a slight topic hijack, I've discovered another autopilot oddity. I was doing a speed test at 10,000m. When I accelerated past about M2.3, the AP produced a very slow but diverging pitch oscillation. Vertical velocity started oscillating from -6 to +6 which grew to roughly -10 +10 by the time I was passing M2.5 at which point I turned off the AP. Not sure if this was a one-off or a small issue with the new autopilot.

Couldn't agree more. I'd much rather ED take the time to make it a good quality release rather than rush something out just to meet some arbitrary release date.

It's also worth pointing out that some time next year 1.5 and 2.0 are going to be combined, so eventually there will be one version of DCS World (2.5) in which it will be possible to chose maps etc. so any purchases made for 1.5 or 2.0 should carry across to 2.5.

Thanks for the clarification about this. :thumbup:

One other thing I've noticed with the new ACS is that the slight cockpit shaking that would start at around 18-20 degrees AOA can now start slightly earlier. Depending on speed etc. it can start at 15-16 degrees AOA. No more severe in amplitude than it used to be, so I guess it's even more useful now as a warning that you're approaching relatively high AOA and should consider easing off.

No: a couple of seconds after you have electrical power on, the HSI is good to go. This isn't necessarily true of the hydraulics (after turning on the engines watch the flaps indicator for a couple of minutes) but the spin-up time of the navigational gyros doesn't seem to be simulated. I'm guessing that in keeping with other Russian aircraft like the Su-25, the real thing has a spin-up time of 3 minutes. That being said I've never seen footage of an Su-27 starting up that didn't already have external power connected, so by the time the pilot has finished his or her engine start check list the gyros are probably already well aligned anyway.

Hmm, I might have been wrong in my last post. The closest thing to reliable information I've found was a photo from MAKS 2009 that showed a small dielectric dome on the tip of the tail boom of an Su-34 that came from the aircrew training centre at Lipetsk. It's worth noting though that the bort number on that particular Su-34 was number 1, so it may well have been a very early production example or even an early prototype. Even then, I've not been able to find anything to suggest that what was under the dielectric dome was a rear-facing radar. It might equally (and more likely) be a receiver for the EW system on the aircraft. The Su-37 prototype allegedly featured a rear-facing radar (type unknown but possibly an N005?) but since nobody bought any of them, I guess we'll never know for sure. Of note, the Wikipedia article on the Su-34 mentions the rear-facing radar but has no relevant citation, so to be taken with a large pinch of salt. Sounds like this is indeed one of those ideas that came from a combination of observed features & a big dose of conjecture and then gets repeated so often that it becomes accepted knowledge, when in reality it isn't true. Edited to add: Some great photos of an Su-34 being build here. That thing is HUGE! http://foxtrotalpha.jalopnik.com/these-riveting-photos-show-how-russias-su-34-fullback-f-1735446088

Multi-axis control inputs seem to generate a... suspiciously large amount of G compared to single-axis inputs. I'm not sure if this simulates additional airframe stress caused by differential bending moments applied to respective wings, or whether the cumulative G is slightly too high. In any case, ever since we got airframe damage modelling the old high-speed maximum barrel roll tactic for missile avoidance has become mostly fatal.

As far as I'm aware a rear-facing radar was tested in a very early Su-34 prototype and they even tried having R-73 missiles that would fire forwards, do a 180 and kill targets approaching from behind. I believe that they found that the range of the rear-facing radar and 180-turning R-73s were so poor that the space would be much better used by EW equipment, which is what the tail boom in the production Su-34 houses, along with the chute & APU exhaust.

A quick synopsis for you: 1. Cross-talk between roll & yaw is gone. Turning at any speed and any weight is now much more crisp and precise with no wallowing. 2. The AP is now functional down to much lower speeds, probably around 320 Km/h or even lower depending on weight. This means that landing using AP is now possible. Cruise with a full AA war load & full fuel is also now possible up to 12,000m altitude and beyond. 3. The adjusted AOA limiter will now protect you from over-G at any weight & at any speed. Turning off the AOA limiter using the W key gives you the same handling as the old version, i.e. no G limit. Ironhand - Thanks, interesting track.

Ah, good point. Hopefully ED will fix that issue as a priority.

Good points. For heavy landings I usually have the airbrake out and use higher throttle settings to compensate. For very heavy landings I usually come over the runway threshold at around 310 Km/h then chop the throttle as I flare. I certainly wouldn't trust the AP to do any of that but for regular landings at 20,000 - 23,000Kg (tops) the AP isn't a bad option. Despite how user friendly the Su-27 is now compared to the old version of the ACS, I still don't consider it to be a particularly new-pilot-friendly aircraft compared to something like the Eagle or M2000.

Yes, the standard "A" autopilot will now successfully take you all the way in to a runway. Since the DCS Su-27 doesn't have the dedicated 'land' mode that the button suggests the real one does, I think they incorporated the capability in to the general autopilot function. Probably not entirely unrealistic since the navigation system is programmed with the position & orientation of most local runways anyway. As Ironhand pointed out though, you have to be reasonably well within parameters for an AP landing to be successful, and the pilot still has to control the throttle manually. One thing I'm not yet sure about is whether the AP that our DCS Su-27 has is capable of landing anywhere or whether it needs a Russian ILS for full functionality. I'm tempted to say that it simply works anywhere, so not quite realistic: I vaguely remember reading somewhere that the landing assist in the real Su-27 disengages either at the inner ILS marker or at the runway threshold.

Will the VA server be upgrading to 1.5.5?

Canopy bug?

You often have to precisely fly over all the waypoints in a mission to achieve mission success. Might be the problem you had with your mission.

1. Agree. It's a little difficult to calculate as the AOA limiter / stick pusher wavers around a bit but I'd roughly calculated somewhere between 115 & 125% of safe maximum. 5. Surprising - I'd always thought that the route following "A" mode when landing took you to the inner marker, or at whatever point the system lost the ILS signal. Still, if it can actually land now then maybe that's a better simulation of the real system. I was much heavier when I tested it - somewhere around 27,000Kg, but in fairness I may have been using Alt-6 instead of "A" mode. I think the ACS still has a few interesting quirks but it's light years ahead of the old version, especially at low speed.

You're right and I was wrong. My mistake. Exactly as you pointed out, altitude hold works as I described, whereas level flight does indeed have a problem as you described. I'd confused myself about what ACS mode I was using. And I agree, we now have solid titanium tires! Another observation on the autopilot - I tried using the route following mode to land, or at least take me to the inner ILS marker. That also suffered serious problems with maintaining altitude, though it was otherwise stable in terms of pitch & yaw, even down to ~300 Km/h. Final observation - the nasty level of cross-talk between yaw & roll that the ACS had is now completely absent! Roll control feels wonderfully crisp, responsive & accurate even at low speeds & high weight. ED really made a massive difference to the Su-27 with this update. :thumbup: I also tried flying with the AOA limiter disengaged - this feels a lot like our old Su-27 did pre-patch, but of course with no AOA limiter at all. Still very nice crisp response but with the ability to go in to and beyond the AOA / G safety margin. I'd recommend binding the AOA limiter disengagement button (W) to a HOTAS key, I think it's going to get some serious use now during WVR combat.

It does still work, but as part of the fixes applied to the AP it loses then regains much more altitude than it used to. For example, if you're at 0m/s Vv and engage the autopilot at say 10,000m it'll dip down to maybe 9,960m before gradually climbing back up again. We'll need to be much more careful when turning on the AP at very low altitudes I think, but it's much better than having to fly at high altitude manually. I haven't tried landing with it yet. To be honest I never use the auto-land capability but I'll try it out. The one test I did was rather extreme: all-up weight of 27,720Kg with a full A-A weapons load at 12-13,000m altitude. I wanted to see how low an IAS it could cope with before it went woolly on me. The yaw & roll I experienced could well have been due to being at very high altitude (I was close to 14,000m at that point), at high weight and at very low IAS. Might well perform better at low level and especially at lower weight.

OK, some very early initial impressions: 1. The autopilot is now much more effective at much lower IAS values. Where it used to have to be engaged at above or equal to 560 Km/h, that figure now is significantly lower, somewhere between 320 and 340 Km/h IAS. At around 330 Km/h IAS a slow but significant yaw & roll sets in, particularly at very high altitude, but if IAS increased above ~340 then it damps out. THEY FIXED THE AUTOPILOT!!!! WOOOHOOO!!!!!!!!!!!! :sorcerer: This has opened up the region between 10,000m and say 12,500 - 13,000m to autopilot use for high-altitude cruise. If you're going up there then I'd advise very gradual rates of climb and to keep your IAS as high as possible. This will make flights beyond 1,500Km in range much, much easier now than they were before where the autopilot could only really be used up to 10,000m for safe cruise at 85-87% RPM. 2. The AOA limited / stick pusher is now significantly more proactive in limiting AOA and hence G values to safe levels. Essentially the limiter will now save you under any weight / speed conditions, as it did before, but now with a much wider margin of safety. For example, I was in a descending turn at around 5,000m, ~1.3M with full stick back. G was limited to roughly 5.5-6. Weight was 27,720Kg. 3. The effect of turning off the limiter with the "W" key is now much more pronounced. If you turn off the limiter the ACS will (obviously) allow you to go to maximum aerodynamic G values which can and will destroy your airframe. Changing the ACS to manual mode with the "S" key still does what it does. Use above ~450Km/h is not advised unless you know exactly what will happen when you switch to manual mode and are ready for it. Otherwise, instant G lock and pilot death and/or airframe destruction. All in all the Su-27 has become much more care-free, but with the ability to push beyond what the ACS wants to allow you to do, if you're prepared and are able to fly manually within the safety limits of the airframe. Awesome work ED!! Edited to add: This is it! This is the ACS update I've wanted for months. The only things that are ever going to prise me out of the cockpit of my Su-27 are the Spitfire and the Typhoon...

It'd be great if ED could include a directory with the DCS World installation titled something like "community resources" or similar. MOOSE and MIST would be the obvious first choices for inclusion. Wishing Flight Control a speedy recovery :thumbup:

Thanks, I'll crack on with testing. Hopefully the patch will have dropped by the time I'm home from work tomorrow.

Awesome! Thanks! Still testing but I might wait till 1.5.5 is released then re-test it to see if anything has changed. At the moment I have a sort of master worksheet containing every Su-27 performance analysis I've ever done. Would you mind if I copy & paste your formulae in to my work sheet? I'll post it when I'm done with the G testing, probably on Sunday some time provided 1.5.5 is released tomorrow (patches are usually on a Friday I think?). Edited to add: From the 1.5.5 patch notes: Su-27. Flight control system with AOA and G-limiter has been adjusted Su-27. Autopilot has been adjusted Su-27. Tires strength has been adjusted :notworthy: :notworthy: :notworthy: :notworthy: :notworthy: