Board index FlightGear Development Weather

Icing conditions

Everything related to weather simulation, visuals should be discussed in the shader subforum.

Icing conditions

Postby legoboyvdlp » Tue Jul 04, 2017 9:53 am

Hey there,
I have developed a quite advanced simulation of icing for the A320Family. However, I'm not so certain about my icing conditions. At present I use '
Code: Select all
var spread = temperature - dewpoint;
   if((spread < maxSpread and temperature < 0) or (temperature < 0 and visibility < 1000)) { # freezing fog or low temp and below dp
      setprop("/systems/icing/icingcond", 1);
   } else {
      setprop("/systems/icing/icingcond", 0);
   }
.

However, I am not convinced about whether this accurately simulates icing conditions. I know that in clouds below 10 TAT, you should be turning on the anti-ice, at least for the A320 (by SOP).

I was wondering if there is a simple way to get the altitude and position of Advanced Weather clouds, or if there are any better conditions that I could put in this if satement?

By the way, the freezing fog definition is according to Wikipedia, where it says that in the UK fog is defined at 1000m visibility or less. Should I increase that to around 2000m, so it includes freezing mist?

Jonathan
User avatar
legoboyvdlp
 
Posts: 7981
Joined: Sat Jul 26, 2014 2:28 am
Location: Northern Ireland
Callsign: G-LEGO
Version: next
OS: Windows 10 HP

Re: Icing conditions

Postby Isaak » Tue Jul 04, 2017 12:18 pm

I've been searching for this too, as I am doing the same for the 777. Didn't find it yet, so if there's a solution, I 'm happy to hear about it too!
Want to support medical research with your pc? Start Folding at Home and join team FlightGear!
Isaak
 
Posts: 767
Joined: Sat Jun 04, 2011 3:52 pm
Location: Hamme, Belgium
Pronouns: he, him
Callsign: OO-ISA
Version: next
OS: Windows 10

Re: Icing conditions

Postby legoboyvdlp » Tue Jul 04, 2017 1:10 pm

You may use my code at www.github.com/it0uchpods/A320Family for the 777.
As far as I know, there is icing code in Nasal/icing.nas and /PitotIcing.nas (not hooked up to PFD yet). There is also some code in -main.xml.
User avatar
legoboyvdlp
 
Posts: 7981
Joined: Sat Jul 26, 2014 2:28 am
Location: Northern Ireland
Callsign: G-LEGO
Version: next
OS: Windows 10 HP

Re: Icing conditions

Postby Thorsten » Tue Jul 04, 2017 3:30 pm

You may have tried this already - but can't you simply use the current visibility? The larger AW clouds and layers should reduce visibility when you are inside the cloud (and the smaller ones are unlikely to lead to icing...)
Thorsten
 
Posts: 12490
Joined: Mon Nov 02, 2009 9:33 am

Re: Icing conditions

Postby legoboyvdlp » Tue Jul 04, 2017 6:00 pm

Sure. That's just about what I would need; thanks :)

Edit: I take it that is "/environment/visibility-m", as defined in local-weather.nas? I'll continue assuming that is the case.
User avatar
legoboyvdlp
 
Posts: 7981
Joined: Sat Jul 26, 2014 2:28 am
Location: Northern Ireland
Callsign: G-LEGO
Version: next
OS: Windows 10 HP

Re: Icing conditions

Postby Thorsten » Tue Jul 04, 2017 6:07 pm

Yes, that should be it. If that doesn't give you what you need, I'll have to take a look whether we can provide something else.
Thorsten
 
Posts: 12490
Joined: Mon Nov 02, 2009 9:33 am

Re: Icing conditions

Postby legoboyvdlp » Tue Jul 04, 2017 7:06 pm

I can confirm that the property reduces when we are in cloud, so we should be in business :D
User avatar
legoboyvdlp
 
Posts: 7981
Joined: Sat Jul 26, 2014 2:28 am
Location: Northern Ireland
Callsign: G-LEGO
Version: next
OS: Windows 10 HP

Re: Icing conditions

Postby Isaak » Wed Jul 05, 2017 6:06 pm

For me that property doesn't reduce in clouds. It 's fixed at 25000 below about 2500-3000ft AGL and above that increases with altitude (and decreases when descending), but doesn't decrease while flying through clouds. Advanced weather is on, live data, winds aloft waypoints and realistic visibility.
Want to support medical research with your pc? Start Folding at Home and join team FlightGear!
Isaak
 
Posts: 767
Joined: Sat Jun 04, 2011 3:52 pm
Location: Hamme, Belgium
Pronouns: he, him
Callsign: OO-ISA
Version: next
OS: Windows 10

Re: Icing conditions

Postby jam007 » Sat Mar 09, 2024 11:34 am

I'm looking for some property that indicates if you are in cloud or not. Sadly I get the same result as Isaak. No change in visibility. Is there some other solution for this?
jam007
 
Posts: 576
Joined: Sun Dec 16, 2012 11:04 am
Location: Uppsala, Sweden
Version: 2020.4.0
OS: Ubuntu 22.04

Re: Icing conditions

Postby wlbragg » Sat Mar 09, 2024 5:38 pm

You can look at the c182 or c172 for how they do icing. Look at icing.nas it has all the props you should need.
Kansas and Ohio/Midwest scenery development.
KEQA, 3AU, KRCP Airport Layout
Intel i7/GeForce RTX 2070/Max-Q
User avatar
wlbragg
 
Posts: 7574
Joined: Sun Aug 26, 2012 12:31 am
Location: Kansas (Tornado Alley), USA
Callsign: WC2020
Version: next
OS: Win10/Linux/RTX 2070

Re: Icing conditions

Postby david.megginson » Tue Mar 12, 2024 3:41 am

I spent a lot of my 19 flying years around ice, so here goes:

There are two basic types of airframe icing, clear and rime. Where there's a combination, it's called "mixed".

Clear icing is the killer. It's caused by supercooled large water droplets, which come from either lifting action (e.g. near the top of a TCU) or warm, moist air overrunning cold air (e.g. a winter warm front) — also sometimes in freezing fog from cery cold air over open water or in lake-effect weather southeast of the Great Lakes. Even with boots, you stay away from this stuff at all costs in a piston aircraft, and as much as possible in a turbine aircraft (ditto for mixed icing).

Rime icing is typically fairly harmless unless it gets very thick, which takes time to accumulate. You'll pick up a bit of light rime climbing through a typical 2,000 ft winter stratus or stratocumulus layer, but it sublimates off quickly in the sunlight on top, even in very cold air. Light rime just a fact of life for winter IFR in Canada or the northern US. We try not to spend too much time in it, but in Canada we don't worry about a trace of rime even in basic planes with no deicing equipment, like a C172 or PA-28. The main rule is always to have an out ready.

Airframe icing is most common between about +1c and -10c outside air temperature. Below that, the likelihood falls off quickly. By -20c, most clouds will consist mainly of ice crystals, and nothing will stick to the airframe. In stratus clouds, that's pretty much universally true; however, if there's a lot of lifting action (for example, in a TCU or with ridge lift), it's possible the supercooled droplets could be pulled up into the colder air and not have frozen yet, so you really don't want to go through that kind of cloud even at -20c.

Finally, icing forms on thinner surfaces like antennas and temperature probes before it forms on wings. I had a black OAT probe sticking out of my front window. If there was just a tiny trace of frost on it, I didn't worry. If it got a lot of frost on it, then it was time to calmly execute my exit strategy. If I saw any drops of clear ice start to form, then it was an urgent situation and I had to ask ATC for an expedited altitude change. Canadian ATC is used to that, but US ATC kind-of freaks out — different attitudes, I guess.
David MEGGINSON (he/him)
I need more tea.
Scenery: FlightGear Americas Scenery
Fediverse: @david_megginson@mstdn.ca
User avatar
david.megginson
 
Posts: 597
Joined: Sat Dec 10, 2016 8:25 pm
Location: CYRO (Ottawa, Canada)
Pronouns: he/him
Version: next
OS: Linux Ubuntu

Re: Icing conditions

Postby jam007 » Tue Mar 12, 2024 9:28 am

Interesting, thanks!

@wlbragg: As far as i can tell they use cloud layers rather than in a particular cloud to calculate icing. I was interested in checking if you are in a cloud for then setting relative humidity to 100%.
jam007
 
Posts: 576
Joined: Sun Dec 16, 2012 11:04 am
Location: Uppsala, Sweden
Version: 2020.4.0
OS: Ubuntu 22.04

Re: Icing conditions

Postby david.megginson » Wed Mar 13, 2024 12:25 pm

In the advanced weather model, I'd guess that it should be possible to determine vertical air movement — lots means likely cumulus, little/none means likely stratus.

With severe clear (SLD) icing, there will often be a warmer (above 0c) thermal layer a few thousand feet above you. As I mentioned earlier, that's especially associated with the approach of a winter warm front (just like freezing rain on the ground).
David MEGGINSON (he/him)
I need more tea.
Scenery: FlightGear Americas Scenery
Fediverse: @david_megginson@mstdn.ca
User avatar
david.megginson
 
Posts: 597
Joined: Sat Dec 10, 2016 8:25 pm
Location: CYRO (Ottawa, Canada)
Pronouns: he/him
Version: next
OS: Linux Ubuntu


Return to Weather

Who is online

Users browsing this forum: No registered users and 3 guests