What is atmospheric in-flight icing?
Atmospheric icing is a term that describes special weather conditions that can lead to ice accumulation on an aircraft. If an aircraft encounters such conditions during flight, the process is called in-flight icing.
What conditions lead to icing?
Atmospheric icing occurs when meteorological conditions exist that allow for the existence of supercooled liquid droplets in the air. Such supercooled liquid droplets are typically found in clouds (in-cloud icing), but can also occur as freezing rain or freezing drizzle (precipitation icing)
What are supercooled droplets?
Supercooled means, that the droplets have a temperature below the freezing point, but remain in liquid form. This can happen when the droplets lack an ice nucleus (a small particle that acts as a “seed” starting crystallization). Droplets found in clouds are about the size of the width of human hair (15-80 micrometres) while precipitation droplets are much bigger, up to several millimeters in size.
Why is icing bad for UAVs?
When an unmanned aerial vehicle (UAV) flies through atmospheric icing conditions, ice starts to grow on the wings and propellers. As the ice grows, it alters the shape of these aerodynamic surfaces – which leads to flow disturbances. These disturbances reduce the ability of the aerodynamic surfaces to generate lift and thurst while also increasing the resistance (drag). This can quickly lead to hazardous situations where the aircraft cannot keep itself in the air.