In-flight icing is one of the risk factors limiting the use and future potential of unmanned aerial vehicles (UAVs). Icing occurs when a UAV flies into a cloud and encounters supercooled water droplets, which then freeze on the surface of the aircraft. Ice accretion on an aircraft leads to severe aerodynamic disturbances, which can lead to a loss of control or even crashing the aircraft.
To mitigate this risk, UAVs can be equipped with an ice protection system that detects and removes the ice.
An ice protection system works by heating critical parts of the aircraft, such as wings and propellers. Generally, there are two different operating modes for ice protection systems: anti-icing and de-icing.
Anti-icing means continuously heating the surface of the UAV, not allowing any ice to form.
De-icing operates in cycles. In de-icing mode, a small, uncritical, amount of ice is allowed to form before it is removed. This is done by first melting the ice at the interface of the surface and then shedding it from the aircraft.
The main advantage of anti-icing is that it generates less aerodynamic disturbances than de-icing. On the other hand, de-icing requires significantly less energy than anti-icing. Energy-efficiency is very important for UAV ice protection systems, because the energy used for ice protection reduces the range and endurance of the UAV.
Combining anti-icing and de-icing
UBIQ Aerospace is doing research on UAV icing and developing the electrothermal ice protection system D•ICE. In D•ICE, we strive to combine the advantages of both anti-icing and de-icing modes in a hybrid approach.
D•ICE uses a parting strip solution where a small area of the UAV is continuously heated in an anti-icing mode. A larger area works in de-icing mode, periodically detecting and removing ice from the surface by exploiting the kinetic energy of the wind. This operation mode combines the advantages of anti-icing and de-icing, leading to low power requirements and low aerodynamic disturbances.
The video shows the difference between anti-icing and de-icing in an icing wind tunnel experiment.