Clear Ice or Glaze Ice

If a large supercooled water droplet strikes an aircraft, it will start to freeze and this will release latent heat. This will delay the freezing process whilst part of the supercooled water droplet will flow back over the impact surface forming clear ice. The amount of a supercooled water droplet that freezes on impact is 1/80th of the droplet for each degree below freezing.

Clear ice is a transparent form of ice formed by large supercooled water droplets, and it can be dangerous. There can be much flowback and the ice appears transparent because there is no air trapped under the flowback icing.

The ice will destroy aerofoil shapes and its weight can cause problems of control because the build-up can be uneven. It is illustrated in Figure 16.1.
Propeller icing can cause severe vibrations and as the ice adheres strongly, when it breaks off, the pieces can be large and cause skin damage.

Clear ice forms in Ns, Cu and Cb at temperatures from 0 to -20 °C.

It is the most dangerous form of icing because 1) of the speed at which it can build up on the aircraft and 2) it might be very difficult to detect due to its transparency.