correct as is Low Altitude Turbulence / AoA Buffeting Below 200 Feet AGL

[Hawkeye91]

On approach when you drop below 200' the AoA indicator starts to buffet up and down around the FPV. Seems to happen shore based and carrier based landings. This effect isn't experience in other aircraft from my knowledge. Not sure what's causing the phenomenon. I've heard of tower turbulence on carrier approach but I don't see a reason for it to be happening on shore based landings. 

You can see from the video that prior to 200' AGL the on Speed AoA is held rock solid in the center of the E bracket and the second you pass below 200' some kind of simulated turbulence starts happening. Not sure what the cause of this might be.
 

 

F18 Low Level Buffet.trk

Edited January 19, 2022 by Hawkeye91

[BIGNEWY]

Hi, 

do you have any evidence it should not happen? 

I will take a look at the track soon. 

thanks

[Hawkeye91]

39 minutes ago, BIGNEWY said:

Hi, 

do you have any evidence it should not happen? 

I will take a look at the track soon. 

thanks

I don't think evidence exists that it shouldn't happen as the only explanation I can think of would be turbulence which, to my knowledge, isn't simulated in DCS(turbulence is simulate, but it is set to zero for my example mission in the video above). I think the question is, what evidence is there that it should be happening? Is there some kind of simulated low level turbulence effect on the F18 that's meant to simulate turbulence caused by passing behind the super structure of the carrier. Maybe this effect is also applied to shore landings? Thanks for checking.

Edited January 19, 2022 by Hawkeye91

[wilbur81]

15 minutes ago, Hawkeye91 said:

 it shouldn't happen as the only explanation I can think of would be turbulence which, to my knowledge, isn't simulated in DCS or on other aircraft.

 

 

Are you kidding? Turbulence has been an option in DCS under the weather tab for years now... I always crank it up to get that more realistic air-feel.

[Hawkeye91]

20 minutes ago, wilbur81 said:

Are you kidding? Turbulence has been an option in DCS under the weather tab for years now... I always crank it up to get that more realistic air-feel.

Huh, well I'll be damned, but that still isn't the case here, as the mission I used in my example has turbulence set to zero. Also no need for the hostility. I didn't know it existed. 

Edited January 19, 2022 by Hawkeye91

[Hawkeye91]

This F18 HUD footage shows a burble where the E bracket bobbles up and down when the plane passes behind the super structure then settles back centered once the plane passes the super structure, but other than that, it seems much more stable and its hard to say if that was cause by the pilot pitching the plane down a little bit and back up as has slightly high on the ACLS needles. 

 

Edited January 19, 2022 by Hawkeye91

[wilbur81]

57 minutes ago, Hawkeye91 said:

 Also no need for the hostility. 
 

Indeed. That was silly and certainly needless on my part for sure. Sorry about that. 

[Hawkeye91]

So I redid the mission and with wind set to zero wind and its steady all the way down the buffeting doesn't happen. So with wind applied, there's some low level turbulence being applied to the F18 which is strange; just because wind exists doesn't make it turbulent below 200' especially only about 12 knots of wind and no gust factor. Sure terrain can influence turbulence, but generally steady state wind doesn't make it choppy like that unless its very hilly/mountainous steep terrain or you're coming down right next to a tree line or something or you could have strong gust factors, which I see not settings for gust factor. You can see in the mission, Al Minhad is about as flat as it gets. You may get thermals on a very hot day, but thermals wouldn't be only held to 200' and below, they can go for 1000s of feet.  Currently, it appears that wind + below 200' = turbulent. No wind = no turbulence, which is a fallacy because wind shouldn't always mean turbulence.

Edited January 19, 2022 by Hawkeye91

[BIGNEWY]

Tested today doing approaches using your track and I am not seeing a problem, trim for AOA on the E bracket and no issues. 

[Hawkeye91]

18 hours ago, Hawkeye91 said:

 

So I redid the mission and with wind set to zero wind and its steady all the way down the buffeting doesn't happen. So with wind applied, there's some low level turbulence being applied to the F18 which is strange; just because wind exists doesn't make it turbulent below 200' especially only about 12 knots of wind and no gust factor. Sure terrain can influence turbulence, but generally steady state wind doesn't make it choppy like that unless its very hilly/mountainous steep terrain or you're coming down right next to a tree line or something or you could have strong gust factors, which I see not settings for gust factor. You can see in the mission, Al Minhad is about as flat as it gets. You may get thermals on a very hot day, but thermals wouldn't be only held to 200' and below, they can go for 1000s of feet.  Currently, it appears that wind + below 200' = turbulent. No wind = no turbulence, which is a fallacy because wind shouldn't always mean turbulence.

 

@BIGNEWY This seems to be the issue with what I’m having and what’s causing the instability on approach.

Wind = turbulence below 200’AGL

no wind = no turbulence

Which neither of the above statements are absolutes IRL, from experience. You can have turbulent days with little to no surface wind and you can have smooth days with a moderate breeze. For some reason, the game engine is generating turbulence below 200’ even though the turbulence setting in the mission editor is set to 0. 

[Tuuvas]

@BIGNEWY I managed to replicate this issue with the following steps

1. Begin "Caucasus FA-18C Free Flight.miz" edited to have no wind (this F/A-18C mission has wind by default)
2. Get into landing configuration, onspeed AOA
3. Descend passed 200ft in glideslope
4. Experience zero shaking/turbulence from 200ft AGL to touchdown
5. Reload mission WITH wind (ex. use an unmodified version of the free flight mission)
6. Repeat steps 2 and 3 above

• Expected Results: No shaking/turbulence from 200ft AGL to touchdown
• Actual Results: Shaking/turbulence when passing through 200ft AGL

DCS Version: 2.7.10.19473

I think the question now is whether or not the expected results is actually what should happen.  That I don't know.

[BIGNEWY]

please attach a short track replay showing it happen so we can check it. 

thanks

[Tuuvas]

@BIGNEWY

Attached are two track files, one with wind and one without.  Same mission.

Hornet_Landing_NoWind.trk

In the No Wind track, there is zero turbulence when passing through 200 feet

Hornet_Landing_WithWind.trk

In the With Wind track, there is subtle but noticeable turbulence when passing through 200 feet

[Vlad_Mig]

Also it can be seen that rudder is rotating really fast when you decent less than 300-250 feet. I’ve noticed that a week ago, but didn’t know whether is was a bug or not. 

[Tuuvas]

@BIGNEWY See below recording I put together showcasing the issue a bit better:

 

[BIGNEWY]

Thanks Tuuvas, 

I have spoken to the team this morning, we don't think it is an issue, with wind enabled there will be some turbulence, the speed of the wind will have an effect, the wind in the track is a slight crosswind.