No lift in very strong thermals

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XelSirko
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No lift in very strong thermals

Post by XelSirko » Mon Aug 03, 2020 2:58 pm

Hi everyone! New to this forum, condor 2 and soaring in general, but i'm pretty sure what i'm seeing in sim is some sort of a bug. Checking if community knows something about this before submitting official support question however.

With certain settings (in this case, I set almost maximum inversion level height and extremely high cloud base), in the center of very strong thermal, lift would completely disappear, with a visual and audio 'jerk' too.

Enabled helpers and recorded it: https://youtu.be/CqsdZlkDYIc

Links to specific moments when 'jerks' happen: It's almost as if thermal is too strong and it gets reset/ignored.

Also i think some other recent topics in this forum might've referred to this same problem:
viewtopic.php?f=32&t=19976&p=171092&hil ... al#p171092
viewtopic.php?f=32&t=19696&p=168896&hil ... al#p168896

Any idea what could it be?

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EDB
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Re: No lift in very strong thermals

Post by EDB » Mon Aug 03, 2020 5:42 pm

I see enough lift. The pilot is constantly leaving the lift though...
And when I see the sides of the video, there is some hardware problem.

Make a second video and now in the default Slovenia2 landscape.
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XelSirko
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Re: No lift in very strong thermals

Post by XelSirko » Mon Aug 03, 2020 6:00 pm

Yep, I'm leaving the lift on purpose just to illustrate the problem (the abrupt changes from good lift to no lift and back).
Make a second video and now in the default Slovenia2 landscape
Makes sense, will record and post later today.

Thanks

Rotareneg
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Re: No lift in very strong thermals

Post by Rotareneg » Tue Aug 04, 2020 1:10 am

Also attach the flight plan to your post, which will make it a lot easier for someone else to try to reproduce, assuming they have the Boulder map.
Image

XelSirko
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Re: No lift in very strong thermals

Post by XelSirko » Tue Aug 04, 2020 2:34 am

Reproduced in Slovenia2 landscape:
https://www.youtube.com/watch?v=UDFxmTN3Tho
There are a few abrupt lift changes in first 50 seconds of the video, but there are also thermals generating no lift at all later: links to specific timestamps are in video description, I don't expect anyone to sit through the whole 15 minute video :)

Also reproduced without VR, both Fullscreen/windowed and with another glider.

Another note. This seems to affect the "base" of the thermal, where several yellow and red stream converge. Problem doesn't exist at higher altitude:
Image

Rotareneg wrote:
Tue Aug 04, 2020 1:10 am
Also attach the flight plan to your post, which will make it a lot easier for someone else to try to reproduce, assuming they have the Boulder map.

Attached:
thermal_test.fpl
I put 'Start' turnpoint right at the thermal i can reproduce this in and added airborne start at max height so it's easy to get there. Problem happens in lower part of thermal, around 3400 feet, and for some reason only after about 6-7 minutes of flight time passes.
You do not have the required permissions to view the files attached to this post.

tiberius
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Re: No lift in very strong thermals

Post by tiberius » Tue Aug 04, 2020 8:30 am

I think the problem here might not be the thermal itself but how the thermal helpers are representing it. As thermals mature it’s not uncommon not to find lift at lower levels.
Image

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Paul_UK
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Re: No lift in very strong thermals

Post by Paul_UK » Tue Aug 04, 2020 2:05 pm

Can't deny that you're seeing an issue however I cannot replicate it with the FPL you have provided in the thermal at the start point. Here is what I tried:

FPL as is in the JS1-18
FPL with thermals set to 'very strong' in JS1-18 as you mentioned that earlier
FPL with thermals set to 'very strong' in Blanik. I went right down to the top of the trees and was able to climb away no problem. Before going that low I flew through the thermal several times and it was all smooth.

From my experience if you see red going up in the thermal markers at the height you are at you will climb. They fade as they get closer to the ground and in this faded area is where you'll struggle to climb.

:oops: just noticed you stated 6 to 7 mins of flight time, I'll report back as I flew there at VNE
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Paul_UK
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Re: No lift in very strong thermals

Post by Paul_UK » Tue Aug 04, 2020 2:25 pm

I can confirm I see the same, very very strange.

If I fly at VNE in the Blanik to the thermal it's smooth right from bottom up. I flew across at various heights.

If I fly over to the thermal slowly (7mins) I noticed the problem at 4300QNH, It was like there was lift but the very core had nothing. At that height I could climb away just had to be sure not to touch the core. Down at 3400QNH the core was totally dead, total opposite from if I arrived there after 3-4mins of flight.

There is also the strange jump / snatch present for me too.

I've never seen anything like that before, bizarre.
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XelSirko
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Re: No lift in very strong thermals

Post by XelSirko » Tue Aug 04, 2020 4:07 pm

Paul_UK wrote:
Tue Aug 04, 2020 2:25 pm
I can confirm I see the same, very very strange.

If I fly at VNE in the Blanik to the thermal it's smooth right from bottom up. I flew across at various heights.

If I fly over to the thermal slowly (7mins) I noticed the problem at 4300QNH, It was like there was lift but the very core had nothing. At that height I could climb away just had to be sure not to touch the core. Down at 3400QNH the core was totally dead, total opposite from if I arrived there after 3-4mins of flight.

There is also the strange jump / snatch present for me too.

I've never seen anything like that before, bizarre.

Paul, huge thanks for taking the time to reproduce this! This should exclude my PC/HW as potential root cause.

BTW, this particular thermal was an example conveniently close to initial starting point. Other thermals later in the flight that were worse: generating no lift at all even outside the core and at pretty high altitude, the snatch/jerk with them is present, but often almost unnoticeable:
https://www.youtube.com/watch?v=UDFxmTN3Tho&t=248s
https://www.youtube.com/watch?v=UDFxmTN3Tho&t=460s

I'll try to experiment some more this week with weather settings to see how they change this behavior. At least I want to understand which settings to tune to avoid ever encountering 'fake' thermals like this.

P.S. The whole reason I started playing with manual weather settings - many default weather presets put clouds way too low for Colorado landscapes (Denver ground level: 5,280 feet ~= 1600 meters), often right on the ground :)

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EDB
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Re: No lift in very strong thermals

Post by EDB » Tue Aug 04, 2020 5:33 pm

XelSirko wrote:
Tue Aug 04, 2020 2:34 am

Another note. This seems to affect the "base" of the thermal, where several yellow and red stream converge. Problem doesn't exist at higher altitude:
Image

I haven't got the time now to check for the, as I understand it, "hollow thermals". :?

But that thermals aren't easy to pic up at low altitudes is normal. Even more when you set narrow thermals. And that when they start to grow old, they will dye. And you will notice this first at the bottom of the thermal.

The rising air creates a small low pressure area below the thermal that will suck in air from all sides. Just like a chimney. If this air is also warmer then the surrounding air, the thermal will continue. But this sucked in air has to funnel vertically before it starts generating vertical lift.

I understand you are new to soaring. Maybe go through this manual : FAA - Glider Flying Handbook (PDF, 46.5 MB) (Full version)
For thermals start at page 9-6.
Last edited by EDB on Tue Aug 04, 2020 5:42 pm, edited 1 time in total.
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Paul_UK
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Re: No lift in very strong thermals

Post by Paul_UK » Tue Aug 04, 2020 5:40 pm

EDB, whilst I'm quite low hour RL (95ish) I've been dabbling in Condor for some time.

Usually when a thermal is dying and the lift isn't working the thermal helpers become extremely faint / hardly visible. At this point in time the red part of the thermal helper is not at that point. I'm only basing this on my prior experiences. I'll have another play later, I'll hang around and watch what the thermal does for a bit longer. I did notice that with that particular thermal there was no CU at the top of it.

What is most bizarre is the jump / snatch the glider makes. It's like an on / off switch for the lift, totally binary. I've never experienced that before in Condor at all.
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Re: No lift in very strong thermals

Post by EDB » Tue Aug 04, 2020 5:57 pm

Paul_UK wrote:
Tue Aug 04, 2020 5:40 pm
What is most bizarre is the jump / snatch the glider makes. It's like an on / off switch for the lift, totally binary. I've never experienced that before in Condor at all.

I can imagine that with very strong and very narrow thermals it feels a bit binary. From -10m/s to +10m/s in less then one second. I know one guy from my first club that went with his head through the canopy of his LS3 in the Alps because of sudden sink on circuit.

You hear the flexing and cracking of the air-frame. But it looks a bit weird in the video indeed... Is that with all the gliders or only with the Blanik?
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Re: No lift in very strong thermals

Post by Paul_UK » Tue Aug 04, 2020 6:04 pm

EDB,

I just buzzed over in the Ventus-18 and getting there quickly the lift is smooth and consistent from just above treeline. I kept climbing / descending and sure enough after about 7mins the weird jump / no lift starts.

I hung around to watch the thermal and it is a generating thermal, a CU was forming as I finished experimenting.

I'm stumped, I've never had a thermal react like that ever and I've flown many many thermals in Condor.
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Rotareneg
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Re: No lift in very strong thermals

Post by Rotareneg » Tue Aug 04, 2020 9:25 pm

To be fair, tornadoes and other atmospheric vortexes can have sinking air in the middle... ;)

Here's my video reproducing this:

Image

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EDB
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Re: No lift in very strong thermals

Post by EDB » Wed Aug 05, 2020 12:32 am

@ XelSirko

One other thing I found strange in one or both (? Speaking from memory now) videos is that sometimes the electronic vario sound wasn"t changing pitch/volume when entering lift while the instruments where indicating changing lift positively. As if the video sound wasn't synced correctly sometimes... Did you change the vario settings?

I'm only able to look into these vertical hickups and hollow thermals in more detail in or after the weekend....
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