There are a lot of good written articles and videos about icing, our knowledge about its causes and effects has increased significantly during last years, but we still have dangerous encounters, incidents or accidents due to ice formation.
The problem with ice is that you don’t know how bad it is until you are in a serious situation. Prevention is the best course of action, or escape if you are in the middle of it.
There are several types of ice, but once you see it forming in your airplane surfaces all ice must be considered as a threat. Ice formation needs of certain conditions to meet, the most important of those conditions are moisture and sub-zero temperatures. Ice formation is faster on clouds with vertical development, where the water drops remain on a liquid state under below zero temperatures, often known as super cooled drops. When this drops hit the cold airplane surface, they freeze instantly. Want an example of super cooled drops? – Place a closed soda drink in the freezer and leave it there for several hours, observe later that the drink still conserves a liquid state, but it freezes as soon as you open it.
There are certain important considerations about operations under icing conditions; first, as airline pilots say, is the equipment. – What kind of aircraft are you flying? – A Jet? – A Turboprop? – Or a piston single or multiengine? I remember a couple of years ago I was flying a Piper Navajo without de-icing equipment and was very concerned about icing conditions on my route of flight. Then came an MD-80 pilot and told me they had no ice at FL120 during descent – Of course Captain! I thought, the temperature rise at your descent speed, (around 280 kts. at that altitude) is of nearly three degrees! Jet performance is not parameters you can compare with other turboprops or piston aircraft.
Second, which is your on board de-ice, anti-ice equipment? – Is it working properly? Once in the clouds is very unpleasant to discover that is not.
Third, are you going to climb through icing conditions? Are you going to remain inside of clouds with forecasted ice formation for the duration of the flight? Or are you going to descent through them? – This questions have a direct relationship with the type of aircraft that you are flying. A jet can exit icing conditions very quickly during climb to higher altitudes where the temperatures are so low that water does not exist on a liquid state, so, no ice formation.
A turboprop can face a serious challenge if it has to face severe ice formation during climb or during typical turboprops cruising altitudes. Not to mention a piston aircraft, even worst. If you going to descent through severe icing conditions, how about a go-around with an airplane degraded in performance due to ice accretion?
No doubt that flying in icing conditions requires careful planning.
One thing to bear in mind is that there is no aircraft that can sustain severe ice formation; again, the problem lies in that you don’t know how severe is it until you discover that ice is forming rapidly around the airplane.
When you discover that ice is forming quickly in your propeller aircraft, the only option may be begin a descent to a lower altitude, looking for warmer temperatures, but then it comes the fourth consideration; the terrain.
If you have to descent, how low can you go? – The mountains below you can be a hidden trap.
If you plan to fly on icing conditions or they are forecasted along the route, work on an exit to escape them in case that is necessary, being flying at a lower altitude, staying clear of clouds, or planning an alternate route of flight.
At last, when ice shows up, don’t sit there just wondering, do something quickly.
Want to read more about icing? I recommend these articles.
– The Naked Truth About Icing Conditions – By Eric Jaderborg
– In Flight Icing – Skybrary Aero
– Defining Know Ice – Bob Miller
– Flight Training AOPA – Aircraft Icing