Anti-icing systems are an option for aircraft, but they are typically mandatory in cold weather and high altitude conditions. This is because ice can form on an aircraft’s wings, tail, and other surfaces, which can greatly reduce the aircraft’s lift and cause it to stall or crash.
Forgetting to turn anti-ice on is a very serious issue, as it can lead to the formation of ice on the aircraft’s surfaces and result in a loss of control. It is the responsibility of the pilot to ensure that anti-icing systems are activated when necessary, and it is a standard operating procedure for the pilot to check the status of the anti-ice systems before takeoff.
If the anti-ice systems are not functioning properly, the pilot should not take off, and the aircraft should be repaired before it is flown again. In addition, the pilot should also monitor the weather conditions, and if ice starts to form on the aircraft’s surfaces, the pilot should turn on the anti-ice systems immediately.
(You can find many videos in YouTube or Facebook about anti ice)
( Short explanation about Anti-Ice )
Further Explanation by Anas Maaz ( Airline pilot. Airbus A320/A321 )
The ice protection equipment must be turned on whenever icing conditions exist. For icing to occur, you need a sufficiently reduced outside temperature and sufficient visible moisture. You strictly need two of these conditions to be there for ice to form over an aircraft.
On ground, when the outside temperature or Static air temperature (SAT) is below +10 degree Celsius and when visible moisture (clouds, fog, snow, sleet, rain etc) is present you should expect air frame icing. In flight, things are bit different. When in the air, the SAT does not give an accurate information about the actual temperature the aircraft is experiencing. As an aircraft gains speed, more and more air particles or molecules hit the aircraft. This converts the Kinetic energy of the air into heat. So, the real temperature of the aircraft skin is higher than the actual outside temperature or the SAT. We call this temperature, the Total air temperature (TAT). In high speed aircraft, we have TAT probes which basically stop and stagnate the moving air. This stagnation causes air to heat up and give an increase in temperature. We call this the Ram rise. This information is then fed to the cockpit indicators. Thus, when flying we look at the TAT reading and decide on when to turn on the anti ice equipment of the aircraft. The general rule is, you wait until the TAT temperature falls below +10 degree Celsius.
In flight, we rely on SAT only when the outside temperature goes below -40 degree Celsius. Once below this temperature, the clouds only have ice crystals and the super cooled droplets no longer exist. So, the chance of ice formation is greatly reduced at higher altitudes where the temperatures are usually below icing range. Those airplanes which fly at mid range altitudes (15000 to 25000 ft) are usually at the greatest risk of ice formation in flight because within these altitudes, the temperature is both low and high enough for some severe icing to exist. This is one of the reasons why turboprops have better anti ice equipment when compared to jet aircraft. In most turboprops, you will see a black lining on the wings and other lifting parts of the aircraft such as the tail plane. These are deicing boots that can pop up like a balloon to crack ice that forms over the flight critical areas such as the wings. In jet aircraft, you will mainly see heating used for anti ice purposes. The outer parts of the wings and the engine intakes are heated by engine bleed air to simply prevent ice formation. There are no anti ice systems on the tail surfaces and the inner parts of the wings. This is because jet aircraft tend to spend most of their flight time at higher altitudes where icing simply does not exist. The faster speeds also help because it results in more kinetic heating.
The failure to turn on anti icing in icing conditions can lead to:
- Engine intake icing. The ice that gets formed near and around the intakes can break off and enter the engine and damage the compressor rotor and stator blades. This can reduce the compression capability of the engine which can lead to engine stalls and surging. The ice can also hit the cowling and other outer engine coverings and cause physical damage.
Wing leading edge icing. Now, this is no brainer. Ice can change the shape of the wing and this can affect the wing’s ability to generate lift.
Ice adds to the effective weight of the aircraft. This means that the aircraft has to be flown at a higher angle of attack than normal. If the wings are iced up, this can lead to a very dangerous situation such as an unrecoverable stall.