What type of icing is caused by supercooled water striking the aircraft's airframe and sticks to the outside of the airplane?

The correct answer is structural icing, which occurs when supercooled liquid water droplets collide with an aircraft's surface and freeze upon contact. This type of icing typically forms in conditions where the aircraft is flying through clouds containing supercooled water. The immediate freezing of these droplets creates a layer of ice that adheres to the airframe, and this can significantly affect the aerodynamic properties of the aircraft, increasing drag and decreasing lift.

Rime icing, on the other hand, consists of small ice particles that form when ice crystals freeze quickly in an unsteady pattern, leading to a rough surface. Clear icing, which is often mistaken for structural icing, results from larger supercooled droplets that freeze more slowly and create a smooth, transparent layer of ice that can be particularly hazardous. Mixed icing contains characteristics of both rime and clear ice, as it occurs in conditions where both small and large water droplets exist.

Each type of icing affects flight operations differently, but structural icing is specifically characterized by the freezing of supercooled water droplets upon contact with the aircraft's surface.