not a bug F18 roll rate decreases as speed increases, F16 doesn't

[OldFlyer]

Hi

At times I've found the F18 to be sluggish when rolling. Today I played around with it and found that approx. the 400-500 knot range is the sweet spot for F18 roll rate. Below 400 the jet becomes sluggish to roll and above 600 it's very slow. 

 

The F16 on the other hand does not exhibit this behaviour - it just continues rolling at the same rate from 350 to 600+.

 

Is this realistic? Presumably one of them is incorrect, and I'm hoping it's the F18. Surely roll rate is unaffected by forward speed.

 

Here are 2 tracks. Exact same mission in mission editor, both clean aircraft. F16 and F18, rolling as speed increases. Both full stick to the left (from memory I went left, but whichever way it was - was full stick). You can see that the F18 when up around 600 knots barely wants to roll. 

F16_rolling_test.trk F18_rolling_test.trk

[Temetre]

I think it might be because the F-18 g-limiter is dynamic, considering weight, stores, speed, etc. I think it even actively measures wing-bending. On that basis, g-limit, and evidently roll authority, are constantly adjusted.

Otoh, the F-16 got an FBW, but it seems to be much more static limitations and capabilities; it treats the aircraft as if its always clean and light. Only the Stores CAT 1/3 switch has slightly stricter limits to roll-rate and AoA for heavy loads, but doesnt even touch the G-limit.

 

Basically, the F-18 limiter protects the plane and payload, probably also limits long-term stress on the airframe. For the F-16, the pilot is supposed to make sure the plane and its payload doesnt break. Currently thats not much of an issue tho, because the game doesnt simulate that type of damage.

Edited June 2, 2023 by Temetre

[OldFlyer]

I see what you’re saying, but rolling around the axis should only be 1g so not sure why the g-limiter should be making any adjustments.

Also, there shouldn’t be additional (significant) wing loading / g-forces as speed increases such as to reduce the roll rate to the extent that it does?

[Pavlin_33]

3 hours ago, OldFlyer said:

Hi

At times I've found the F18 to be sluggish when rolling. Today I played around with it and found that approx. the 400-500 knot range is the sweet spot for F18 roll rate. Below 400 the jet becomes sluggish to roll and above 600 it's very slow.
...

If it makes you feel any better, MiG-29 has the same thing. At high speeds, its roll-rate drops significantly. It's what happens in real life also.

[razo+r]

4 hours ago, OldFlyer said:

[...] Surely roll rate is unaffected by forward speed.

[...]

 

Roll speed is definitly dependant on airspeed. The faster you go, the less effective ailerons can become. They may even lose total effectiveness or in the worst case produce aileron reversal. However, what exactly happens to the effectiveness depends on the wing design. And I personally cannot tell you what would happen in case of the F-18 design. Reduced effectiveness does seem to be plausible though.

[OldFlyer]

Fair. However check out the tracks I provided - 600 knots in the viper, no change to roll rate. Same in the F18 and it’s dangerously slow. Would love ED to look and comment.

[CageyLobster]

If you look up the Natops manual in section 11.1.8 talks about aircraft stability and dynamic response.  It does mention in situations the FCS does limit roll.  But, I am not a hornet guy, so my knowledge in what the book says vs. what happens in DCS is very, very limited.  I just recently read about it, and was curious if this was what you could be witnessing in the -18.

[Temetre]

vor 5 Stunden schrieb OldFlyer:

I see what you’re saying, but rolling around the axis should only be 1g so not sure why the g-limiter should be making any adjustments.

Also, there shouldn’t be additional (significant) wing loading / g-forces as speed increases such as to reduce the roll rate to the extent that it does?

There is radial G-force, or centrifugal G-force, and the roll rate limiter is almost certainly there to protect wings, pylons and payload from that.

Either way, calling it a "g-limiter" is an oversimplification, it does a bit more than that.

vor 3 Stunden schrieb OldFlyer:

Fair. However check out the tracks I provided - 600 knots in the viper, no change to roll rate. Same in the F18 and it’s dangerously slow. Would love ED to look and comment.

Its more that the Viper is dangerously high. You can probably break the aircraft quite easily, if you put some 2000 lb bombs below it and do max rate rolls. In reality that is, because that damage model is missing ingame.

 

edit: To be fair, if Im misunderstanding the FBW and the F-18 has no active limiting of the roll rate, then I would agree - that would seem pretty dodgy, how even minimal loads make the F-18 roll so much slower.

Edited June 2, 2023 by Temetre

[Hulkbust44]

Roll speed is definitly dependant on airspeed. The faster you go, the less effective ailerons can become. They may even lose total effectiveness or in the worst case produce aileron reversal. However, what exactly happens to the effectiveness depends on the wing design. And I personally cannot tell you what would happen in case of the F-18 design. Reduced effectiveness does seem to be plausible though.

At highspeed the stabilators are exclusively used for roll.

Sent from my moto g stylus 5G (2022) using Tapatalk