CyberAirVA

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Icing

One of the things that can and will affect your aircraft is icing. I will explain the types of icing, why icing forms and how to avoid it. Ignoring icing can very well lead to a crash.

Types
There exist a couple of groups of ice. They are:

Structural ice
Clear ice
Rime ice
Mixed ice
Induction System Icing

Lets start with the last, Induction system ice. This is simply ice that forms in or around the air intake, engine. It can have massive affects on the engines (and therefore the aircrafts) performance. The first group though is the structural ice, which can be split into three groups (see above). Clear ice is glossy, and is formed when super-cooled water droplets flow over the aircrafts surface after impact and freeze into a smooth sheet of solid ice. It is most often encountered when flying in temperatures between 0 degrees and -10 degrees Celsius. Also in Cumulonimbus clouds at temperature down to -25 degrees. Rime ice is milky, opaque and granular. It forms when small super-cooled water droplets hit the aircraft and instantly freezes. Most usually encountered in stratiform clouds at temperatures between 0 degrees and -20 degrees Celsius. Mixed ice is as the name implies a mixture of clear and rime ice. It is hard, irregular. It is formed when super-cooled droplets varying in size hit the aircraft and (or) flying through snow, ice pellets or small hail. Structural icing is dangerous because of the increase weight and drag, and the decrease in lift and thrust. You might fall out of the sky, literally.
Note that ice that are already present on the aircraft before take-off is just as dangerous as any of the types above.

Why does icing form?
Ice is just a form of water, and when waters temperature falls below 0 degrees Celsius it freezes. We all know this. But water sometimes doesn't freeze when it's temperature is at or slightly below 0 degrees. It's then called super-cooled water/droplets (as mentioned above). Super-cooled water has the somewhat unpleasant habit of freezing when it comes in contact with something cold and hard, like the surface of the aircraft. So when does icing occur? Well as you read above it usually happens around or below 0 degrees Celsius. and it seems to happen when we fly through clouds. But it can also happen when we fly through rain, drizzle or haze.

How to avoid it
The first thing to avoid icing is to check the weather reports. You can check for icing reports at ADDS. In a weather report icing will be mentioned as ICG (ICING), ICGIC(ICING IN CLOUDS), ICGICIP(ICING IN CLOUDS AND PRECIPITATION) and ICGIP (ICING IN PRECIPITATION).
AIRMETs (WA) take up icing especially. This part is called AIRMET ZULU and can look like below. This AIRMET describes an area of occasional moderate rime or mixed icing in clouds and precipitation is forecasted from 4000ft to 14000ft MSL over Washington and from 6000ft to 16000ft over Oregon and California. Conditions are expected to continue beyond the end of the forecast period (20Z) to 02Z. Note that all the altitudes in the AIRMETs (and SIGMETs) are in MSL (mean sea level) unless otherwise stated. In the METARs and TAFs the altitude is in AGL (above ground level).

SFOZ WA 141345Z
AIRMET ZULU UPDT 2 FOR ICING AND FRZLVL VALID UNTIL 142000
AIRMET ICG FOR WA OR CA
FROM YQL TO GGW TO BFF TO ALS 140W SFO TO 120W FOT TO 120W TOU TO YQL
OCNL MDT RIME/MXD ICGICIP BTWN 040 TO 140 WA AND BTWN 060 TO 160 OR/CA. CONDS CONTG BYD 20Z THRU 02Z.

SIGMETs (WS) also takes up icing but only severe icing. SIGMETs also cover a greater area than AIRMETs do.

Another important thing we can do is too make sure the aircraft isn't iced up on the ground since this will make it harder to take-off (if at all), and it surely won't make flying any easier.

If you encounter moderate to severe icing on the altitude you are flying, ask ATC for another level, either higher or lower (since icing might not exist in the higher or lower altitudes). If a real pilot would encounter icing he might/should file a pilots report of it, it will let the forecaster know where there are icing and this will help other pilots to avoid the problem.

Don't forget to use your anti-icing equipment. The equipment should be used before the icing occurs, meaning when you suspect that icing might arise. It most probably won't help very much once icing has occurred. Also use the pitot heat always, because if this freezes up you won't know your speed!!!

Don't Under estimate Icing

Check the AIRMETs, SIGMETs, METARs and TAFs.
Check for icing on the aircraft when on ground.
Use your pitot heat and if necessary carburetor heat.
Be extra careful when flying in:
Temperatures below 0 degrees Celsius
Cumulonimbus or stratiform clouds
Rain
Snow
Ice pellets
Haze
Hail
Use anti-icing equipment if you suspect that icing might arise.
If encountering moderate or severe icing, ask for another altitude.
If you encounter light icing and suspect it might get moderate
and severe ask for a change too.

Always be on the safe side, since the other side isn't a very nice one.

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