De-icing / Anti-Icing
Sunday 10th January 2016, CPH.
Last Sunday, the weather in both Copenhagen and Oslo had great impact on both our passengers travel plans and also on our schedule. I, together with my FO P Anderberg did our best to keep it both safe and efficient. However, these matters takes time. A normal de-icing in Copenhagen takes about 5 minutes. This Sunday, it took almost 18 minutes – due to special conditions (sticky snow). Combined with runway clearing, slot times to OSL, ground equipment not able to function at it’s best during heavy snow, push back tractors loosing grip when trying to move our heavy Airbus 321, gate guidance systems breaking down etc. It was one of those days… As a commander you can’t let this inflict your decision making or your way of handling the specific flight. During these circumstances thing takes time – and there isn’t much you can do about it. Most important – Never let pressure come creeping up on you! My task is to secure a safe operation – That’s my number one priority.
Some of you have asked questions about de-icing. Below is a very abbreviated quick course – Enjoy!
A delicate matter
As many of you probably know that an airplane wing is a very delicate construction. Everything is there for a reason, and the manufacturer has worked hard in order to build the most efficient wing profile.
Ice, frost and snow alters the wings character a lot. Even the thinnest layer of frost on the upper side of the wing could in some instances be lethal if left on the wings before takeoff. In Scandinavia, we have a very good knowledge about handling these advere situations during our cold winter season. The authorities have come up with a system governing the safe dispatch of various types of aircrafts. At the end, the Commander (Captain) has the ultimate responsibility to checkand decide which treatmet that should be used.
3 types of fluids
The three most common types of deicing fluids are
Type I/Type II/Type IV
Type I is un-thickened and either colorless or orange
Type II is thickened and either colorless or yellow
Type IV is thickened and colorless or green.
A one step procedure is done with Type I, simply to remove the existing layer of frost/snow/ice. The fluid is mixed with hot water. A one step procedure with Type I is only possible if there is no precipitation present and takeoff expected within a couple of minutes after the treatment
A two-step procedure is necessary as soon as there are some kind of precipitation present in combination with low temperatures. First step removes existing deposits and the second step prevents snow/frost/ice to build on the wings, airframe & stabilizer (within a certain time frame). This is called anti-icing (compare de-icing). De-icing is a removal procedure, Anti-icing is a preventive procedure.
Type IV fluids are even thicker and gives longer anti-ice effect. However, these fluids have a couple of disadvantages as well, and are seldom used nowadays.
After completion of the treatment, the Commander needs a de- anti icing report from the ground personnel, where after he checks a Hold Over Time table (HOT) to decide the latest time a takeoff is possible. This is depending on type of fluid, precipitation, temperature etc.
A pre takeoff check is done before every takeoff after de-icing.