Why is de-icing offered?

[stefangr]

Hi team,

from what I have learnt here https://www.fsdreamteam.com/forum/index.php/topic,17202.msg121160.html#msg121160 (I hope this is still the most current version of de-icing rules) I would expect GSX to offer de-icing when

Outside temp < +8°C
AND
( Dewpoint >= (Outside Temp -2) OR it's snowing)

Is that still correct?

I have encountered some situations where de-icing was offered where I think it should not.

Current example: EDDW 131420Z 15003KT 9999 FEW015 M01/M07 Q1042 R88/190095 NOSIG

Outside temp = -1°C
Dewpoint = -7°C
It's not snowing

In this case, the GSX menu asks me if I want to have de-icing treatment. Yes, outside temp is below +8°C but it's not snowing, and dewpoint is lower than 2 degrees below outside temp. I would think that in this example without snow, the dewpoint needs to be -1, -2 or -3°C for de-icing.

Maybe there has changed anything in the meantime?

Using P3Dv4 and Active Sky with GSX Level 2

I have enabled logging of offsets within FSUIPC to make it clearer:
x28D0 delivers outside temperature in °F: 30.178346 / -32 then *5 /9 delivers °C -> -1.01°C
x04C8 delivers dewpoint and needs to be divided by 256 -> 63744 / 256 = 249 -> if it's above outside temp, 256 need to be subtracted: 249-256 = -7°C
x04CC delivers precipitation: 1 = rain / 2 = snow / 0 = none

[virtuali]

from what I have learnt here https://www.fsdreamteam.com/forum/index.php/topic,17202.msg121160.html#msg121160 (I hope this is still the most current version of de-icing rules)

No, it's not, the current version works a bit different and, when the Metar doesn't arrive, or is corrupted, usually because of using 3rd party weather engines, the Dew point is not used ( since there's no variable in the sim to get it, the only way to get it is from Metar ), and a simpler strategy of checking just the outside temperature + precipitation is used.

Note that, "Metar" here doesn't necessarily mean real world metar from the internet ( which can be used or not, depending on the add-on used ), from our point of view, it's just "Simconnect Metar", meaning a data result GSX asks to the sim, which is provided using the standard Metar format so, even if you just set a weather theme manually, it will still generate a Metar report, GSX doesn't know how the weather was generated, it only ask Simconnect for the Metar, and it's supposed to arrive, and if it doesn't, or is wrong or contains error, or doesn't arrive in time, GSX will use the simpler strategy that doesn't involve reading the Dew point.

[stefangr]

Thanks, Umberto, for this clarification.

Is there any way that this information (the received METAR from Simconnect and whether this is being used as basis) is logged in any log file?

Let's assume in my example the requested METAR had erros and was not respected, from where do you get the precipitation? I checked the offset 04CC delivering 0 which means none. So still wondering where this de-icing offer in GSX was coming from.

[virtuali]

Is there any way that this information (the received METAR from Simconnect and whether this is being used as basis) is logged in any log file?

Yes, if you have logging enabled in the Troubleshooting section of the GSX settings, problem with Metar will be logged there.