Summary Ice creates drag, disrupts airflow on wings, and damages engines, affecting aircraft performance significantly. Supercooled water droplets cause icing; different types of ice, like dangerous clear ice and less dangerous rime ice, have various impacts. Pilots must classify icing conditions based on accumulation rates, from trace to severe, to determine safety and necessary actions.
Aircraft icing is the accretion of ice on an aircraft's surface. It can lead to loss of performance, increased fuel consumption, and, in the worst-case scenario, loss of control. Therefore, anti-icing systems are a critical part of an aircraft that enables it to fly safely.
This threat was evident this week when an ATR 72 crashed near São Paulo after flying through an area with a severe ice warning, leading to the death of 61 souls onboard. How does icing occur? Icing is caused by the presence of Supercooled Water Droplets (SWD). SWD can remain in liquid form at very low temperatures because they lack a freezing nucleus.
Pure water droplets turn into ice when either they are cooled to very low temperatures or when they meet a freezing nucleus. A freezing nucleus can be a speck of dust or any other form of impurity around which the water freezes. Supercooled water droplets are thus pure water droplets, and this allows them to remain as a liquid.
It is these droplets that are most dangerous to aircraft - when supercooled water droplets make contact with an aircraft, they freeze instantly bec.