Insane rate of roll?

[HellSpawn000]

Hi there,

 

 

I experience insane rate of rolls after 1.52, and I (though I never flown the real plane) doubt it is realistic? The fast rolling usually ends up in redout. It feels very arcade-ish.

[tweet]

The T-38 roll rate at maximum stick throw was 720 degrees/second. Full stick aileron rolls of more than two rolls were prohibited. It has been a long time since I flew it but I seem to remember the reason for the -1 prohibition had something to do with disorientation as well as aerodynamic/structural issues. I do remember that it was very easy to bounce the other guy's head off the canopy if he was not prepared for the high roll rate.

 

The Talon is an extreme example because it had, IIRC, the highest roll rate of any jet way back when and maybe still. It also was clean. Adding wing tanks, external weapons, and "wet" wings of combat jets adds mass that must be overcome by aerodynamic forces of ailerons and/or spoilers. This limits roll rate but, yes, some of these fighters can generate considerable roll rates in an appropriate configuration. I've yet to see roll rates in any DCS a/c that I'd consider inappropriate or excessive. Some of the a/c are actually more sluggish than I'd expect. That is only my opinion however since I have not flown any of them with the exception of two sorties in the F-15A family model way back in the early '80s. The real jet seemed slightly more responsive than the sim.

[HellSpawn000]

Thank you for your detailed reply. That puts this matter in a different aspect (I may now believe this is how the Fishbed rolls :) ). I haven't tried with loaded pylons yet, if it's still the same then maybe we can assume it's a minor bug?

[tweet]

I don't know if the MiG21 flight model is sufficiently sophisticated to give you a definite feel difference. About the most any PC flight sim controller can provide is a change in stick deflection to achieve a given roll or pitch rate. You might be able to tell the difference or maybe not. I suspect, I haven't flown the MiG21 recently enough to remember for sure, you will see some difference but the under wing stores are neither plentiful nor all the heavy for a a short span delta wing jet with an inherently high roll rate. Fly a clean A-10 followed by one loaded to near maximum weight if you want to get a good demonstration of the difference. You would definitely be on to a bug if the A-10 has no difference. The MiG21? Maybe, maybe not.

[HellSpawn000]

I haven't tried it, but I found this link in the "AoA 36 degrees" topic that points out my 'problem'.

 

[ame=

]

[/ame]

[El Hadji]

Just for the record, LNS have a qualified MiG-21 pilot on their team. My bet is that the behaviour of the DCS MiG-21 isn't too bad compared to the real deal. Then again I haven't flown it IRL and never will so who knows.

 

About Novak Djordjijevic:

 

"You’d be hard pressed to find an individual with a more impressive resumé than Novak. Not only does he serve his country with distinction as a MiG-21 fighter pilot, he has also authored several books. He has single handedly built our advanced flight modelling and large parts of the DCS: MiG-21."

Edited January 17, 2016 by El Hadji

[Exorcet]

Being light and having a short wingspan helps with roll rate, though the rate in that video does look pretty high. I'm not sure if it's wrong though.

[streakeagle]

Some fighters can hit or exceed 720 deg per sec. But even if capable, most never hit that number. It is a theoretical peak and may take a bit of time to accelerate to that peak. A useful aircraft is one that can precisely roll 180 deg and stop in the least amount of time. Not one that can spool up to some insane number if held to a low AoA with the stick slammed to one side. I don't recall ever seeing a published value for the MiG-21bis, but it isn't going to be much if any better than 720 deg per sec and depending on its ailerons, may be much slower. So if the in-game value as displayed in the video is greater than 720 deg per sec, it is most likely wrong.

 

I have flown plenty of virtual aircraft where actual pilots of that type were consulted and the end result was less than accurate, despite repeated assurances that the consultant said it was 100% correct.

 

At the same time, I have seen actual pilots question the performance of virtual aircraft that followed the published data 100%.

 

The lesson is that what pilots feel/perceive is not being represented correctly by a PC whether the physics are modeled correctly or not. Which brings up the question: given that frequently reality and "immersive" are not one in the same on a PC flight sim, which do you prefer?

 

Reality is having the virtual aircraft hit the known numbers perfectly: time to climb, acceleration from Mach 0.8 to Mach 1.2, sustained/instantaneous turn rates, rotation speed, takeoff roll, etc.

 

"Immersive" is having it feel the way you expect (or in the case of experienced pilots the way it actually felt).

 

Limited display resolution, limited display size, limited frame rates, little or no force feedback , etc. all contribute to differences between mathematically correct and perception.

 

I enjoy the "feeling" of flight. In DCS, the Bf109K4 in particular feels real to me during taxi/takeoff/level flight/landing. I can't quantify the feeling. But given my experience at the wheel in Cessnas and Pipers, the Bf109K4 is more "immersive" to me than any other aircraft available in DCS. I don't know the "textbook" performance of the 109 to criticize any aspect of it. So I can't judge its physics as being mathematically accurate or not. I simply enjoy flying it.

 

However, in a DCS level sim, I want to be able to follow the pilot's manual 100%. I have the flight manual of the MiG-21bis. I don't know what the real aircraft did, but I do know what the flight manual says and what USAF pilots that flew the MiG-21F-13 said. I am mostly happy with the feel of the current release of the MiG-21bis, but it doesn't match some of the real-world data points.

 

So, I guess I am a rivet counting a-hole. I want an aircraft to be immersive AND hit the known numbers. Not an easy job, especially since the accurate numbers may not be available and "immersive" is a subjective value. What is immersive to me may not be immersive to you.

 

How does any business ever survive trying to please hard core flight sim junkies?

Edited January 17, 2016 by streakeagle

[BlackLion213]

Being light and having a short wingspan helps with roll rate, though the rate in that video does look pretty high. I'm not sure if it's wrong though.

 

Very true, plus all of these instances of crazy roll rate are occurring at high speed, like ~650 knots. All 4th Gen US fighters regulate roll rate via their SAS, CAS, or FBW system to limit the roll rate as speed climbs. When the USN was testing the Tomcats DFCS system, the test aircraft were losing panels on the engine nacelles due to excessive roll rates at higher speeds.

 

I don't think that the MiG-21 has a system to reduce roll rate at high speed, so these rapid rolls seem feasible.

 

 

I have flown plenty of virtual aircraft where actual pilots of that type were consulted and the end result was less than accurate, despite repeated assurances that the consultant said it was 100% correct.

 

At the same time, I have seen actual pilots question the performance of virtual aircraft that followed the published data 100%.

 

The lesson is that what pilots feel/perceive is not being represented correctly by a PC whether the physics are modeled correctly or not. Which brings up the question: given that frequently reality and "immersive" are not one in the same on a PC flight sim, which do you prefer?

 

Reality is having the virtual aircraft hit the known numbers perfectly: time to climb, acceleration from Mach 0.8 to Mach 1.2, sustained/instantaneous turn rates, rotation speed, takeoff roll, etc.

 

"Immersive" is having it feel the way you expect (or in the case of experienced pilots the way it actually felt).

 

Limited display resolution, limited display size, limited frame rates, little or no force feedback , etc. all contribute to differences between mathematically correct and perception.

 

I enjoy the "feeling" of flight. In DCS, the Bf109K4 in particular feels real to me during taxi/takeoff/level flight/landing. I can't quantify the feeling. But given my experience at the wheel in Cessnas and Pipers, the Bf109K4 is more "immersive" to me than any other aircraft available in DCS. I don't know the "textbook" performance of the 109 to criticize any aspect of it. So I can't judge its physics as being mathematically accurate or not. I simply enjoy flying it.

 

However, in a DCS level sim, I want to be able to follow the pilot's manual 100%. I have the flight manual of the MiG-21bis. I don't know what the real aircraft did, but I do know what the flight manual says and what USAF pilots that flew the MiG-21F-13 said. I am mostly happy with the feel of the current release of the MiG-21bis, but it doesn't match some of the real-world data points.

 

So, I guess I am a rivet counting a-hole. I want an aircraft to be immersive AND hit the known numbers. Not an easy job, especially since the accurate numbers may not be available and "immersive" is a subjective value. What is immersive to me may not be immersive to you.

 

How does any business ever survive trying to please hard core flight sim junkies?

 

I hear you, things will never be perfect trying to translate the experience of operating a high-performance vehicle onto a stationary computer. Those pilot SMEs have a hard job trying to conclude if something feels right with all of the missing feedback and sensations. I also agree that the Bf109 is very engaging and seems to capture the sensation of flight very well in my eyes (as does the MiG-21 IMHO).

 

Trying to get things right by the numbers might not be simpler - many operational aircraft may not perform by the book either. Many service aircraft operate with slightly detuned engines to reduce the time before engine rebuilds and improve reliability (the case for both the F-15 and F-14A). I've heard a few pilots say that you can't trust the manual when it comes to certain performance figures (a B-25 pilot flat out laughing about the published rate of climb figures).

 

Novak posted a while back that the MiG-21's flight model used data from his own telemetry:

 

http://forums.eagle.ru/showpost.php?p=2299164&postcount=380

 

Which he said deviated from published reports and varied from aircraft to aircraft.

 

So is it better to have performance match the test flights of optimized aircraft or match the average operational aircraft? Can telemetry data be trusted?

 

I think all of us want these modules to be as perfect as possible - that doesn't make us a-holes. How we respond to the inevitable imperfections is the defining feature. ;)

 

And your right, the developers need to take our critiques with a grain of salt...how else can they get out of bed in the morning and continue the march towards perfection?

 

-Nick

[Manuel_108]

I haven't tried it, but I found this link in the "AoA 36 degrees" topic that points out my 'problem'.

 

 

Holy cow that looks extreme.

[Art-J]

I remember this insta-blackout-roll appeared just after 1.5 release, then it was dialed down. Don't tell me it's back again...

[Holbeach]

RL roll rate for a snap roll, on the Mig-15, is 6 to 8 seconds at 600 -700 kph.

 

..