[CORRECT AS IS] Odd rocking in G-onset

Noticed that a quick pull from 1 to 9 G results in an odd bouncing/rocking in G onset (esp. around 500 kts), i.e. the aircraft seems to suddenly command negative stab at around 5 G's to slow the G onset, only to then let it pick up again until it gradually slows the closer you get to 9 G. As a result a quick 9 G break produces a sort of rocking sensation in pitch & G build up, something also noticable on the virtual pilots head movement in the cockpit.

Perhaps it's related to the odd high speed pitch stutter?

Track provided below.

The sudden slow down in G onset rate at around 6 G's is quite noticable.

Note: The track also shows an issue with rudder oscillations.

Onsetrocking&ruddershake.trk

Video showcasing the issue:

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Track has been provided, so might wanna change the title :)

Many thanks BIGNEWY

Observed the following in external view:

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As one can see the stabilators initially make an odd up/down bouncing movement when applying & holding full aft stick, which explains the odd rocking in G-onset/pitch rate that the DCS F-16 currently suffers from.

This could be linked to what @Syndrome previously reported as the horizontal stabilators lacking in speed of deflection, and thus in order to prevent a G-overshoot they have to apply opposite deflection sooner as the whole movement is slower than it should be. This would also affect how fast the G's can be put on (G-onset rate), and thus fixing this might also go some way to solving this issue.

Could be due to a "good" relaxed stability model but with a "bad" FLCS transcription (?).

I don't see the bouncing of the stabs as particularly problematic as for a relaxed stability aircraft you would expect to see a control input to initiate the pitch rate immediately followed by a counteracting input to "catch" the aircraft before it becomes divergent. That isn't to say that it doesn't need tuning.

I don't see the bouncing of the stabs as particularly problematic as for a relaxed stability aircraft you would expect to see a control input to initiate the pitch rate immediately followed by a counteracting input to "catch" the aircraft before it becomes divergent. That isn't to say that it doesn't need tuning.

I agree that a counter deflection is to be expected, it just appears that the stab movement speed is perhaps too low which in turn forces the FLCS to initiate the counter deflection earlier and over do it, causing that odd momentary slow down in G-onset/pitch rate.

Could be due to a "good" relaxed stability model but with a "bad" FLCS transcription (?).

I do believe there are definitely issues with ED's current implementation of the Vipers DFLCS, which shows itself in a number of ways:

1. G-onset rate is suspiciously low

2. 9.3 G's cannot be attained in the horizontal as defined pr. the real DFLCS laws

3. Negative 3 G's cannot be attained at all

4. Weird rocking in G-onset/pitch rate

Personally I see issues 1,2 & 4 being connected, and I suspect an extra 0.3 G's allowed combined with faster stab deflection speeds might help solve it.

Hi!

I do believe there are definitely issues with ED's current implementation of the Vipers DFLCS,

...

 

1. G-onset rate is suspiciously low

2. 9.3 G's cannot be attained in the horizontal as defined pr. the real DFLCS laws

3. Negative 3 G's cannot be attained at all

4. Weird rocking in G-onset/pitch rate

... roll inertia, CATIII roll rate, landing gains ... etc ...

It is not really a matter believes, it is rather facts.

But ... it is a WIP.

Regards.

Hi!

 

 

... roll inertia, CATIII roll rate, landing gains ... etc ...

 

It is not really a matter believes, it is rather facts.

But ... it is a WIP.

Regards.

Yeah, WIP, let's hope it really is WIP and not one of those things that get stuck in the infamous ED loop of "provide evidence" and whatever you provide isn't good enough.

There are a bunch of issues with the engine simulation as well, been like that since day 1 of EA.

Generally I'd love to see progress on the FM parts before focus on the avionics.

Generally I'd love to see progress on the FM parts before focus on the avionics.

Yeah I tend to agree. But I think avionics and weapons are more obvious the end user. I think most people flying it in the sim aren’t experienced enough with the real jet to notice/care about the G onset rate, or the roll-rate in CAT-III etc, but they really want to fire some Mavericks or HARMs. I am sure it will get looked at though.

Yeah, WIP, let's hope it really is WIP and not one of those things that get stuck in the infamous ED loop of "provide evidence" and whatever you provide isn't good enough.

There are a bunch of issues with the engine simulation as well, been like that since day 1 of EA.

Generally I'd love to see progress on the FM parts before focus on the avionics.

Yes the FM should take precedence over all else IMO as well. But BIGNEWY promised an update on this when he knows more. Hopefully that is sooner rather than later at this point.

Thanks for the update BIGNEWY, I just really hope future doesn't mean many months.

@BIGNEWY

Do you know wether there will be any update to FLCS laws/control surface speeds etc with the next big update?

The problem is still there with the latest patch. Stab movement speed still appears way too slow, and there is a sudden slow down in onset rate at ~6 G.

still investigating or it has been confirmed ?

Note:

 

It should be mentioned some factors that affect flight characteristics ( including wing rock) can be seen when terminating high roll rate manoeuvres at high speeds above 400 Knots.

 

It maybe related to this, but the team will review it once they have time.

 

Thanks

I think OP means there's a rocking in pitch-up maneuvers, with inconsistent G evolution rate. Nothing to do with the roll here.

A testing of short period pitch mode should reveal this. For example simply draw a graph of pitch rate vs time, or load factor vs time, using step input to see how the aircraft responses.

By watching the video it looks like this:

Yes, we will look into it, but as the OP's video shows a high roll rate at speeds over 400Knts it was worth mentioning.

Yeah, it also looks like a pitch-up maneuver coupled with rolling is quickly creating sideslips, but a certain gain schedule (maybe somewhere near the lateral acceleration feedback) in the yaw FLCS is too high for this airspeed/altitude and wants to quickly eliminate that sideslip, causing the rudder to oscillate. Just my two cents.