Icing.

[Lump Jockey]

Hello one and all.
I've read some posts on icing, there's a few things bugging me though.
1. What are the different names given to "ice"/icy conditions. I've heard "rime" and "clear". Is there also a "blue" and/or more?
2. Does icing only occur, and I'm gathering it does, when the a/c hits water droplets, ie. through a cloud for example?
3. Contrails. How come some a/c leave no contrail even though they're in the high FL's and it's a gauranteed -30/40?
TIA,
LJ.

[BigHitDH]

Lump,

While not qualified to answer your question, I hope I can help you a little until someone more knowledgeable chips in.

1. Blue ice is generally the ice that forms aroun the heated drain masts for the galleys/toilets. This only usually occurs when the heating element in the mast fails, and can cause all sorts of problems (no water for the gallys etc, plus a long defrost time on the ground).

Frost/Ice has so many names. "Hoar Frost" is generally the type that forms as liquid water hits a very cold surface and freezes. You can sometime see this on wings on aircraft on the ground, as the fuel within has been cold-soaked for a while.

2. As a general rule, icing conditions (in flight) generally occur anywhere where the temerature (OAT/TAT) is at or below 10 degrees celcius, and there is visible moisture in the atmosphere (ie, cloud/fog). Also, crew on jet aircraft would be advised to select countinuous ingnition/anti-ice protection if there is standing water/slush/ice/snow on the taxiways and runways.

3.Contrails are an odd one. For formation several factors have to be met, including, ambient temperature, pressure, and dew point. In some conditions, you can even see jet engines produce contrails on the ground! Try a google search on contrails, there has been much research into it.

I hope that helps, aplogies if I am myself misinformed.

[Lump Jockey]

Thanks for the effort! What is ambient temp/pressure?

[BigHitDH]

Ambient temp/pressure is the temp/pressure "surrounding" the aircraft, or "static air temperature".