Definition
A form of structural icing that combines the characteristics of both rime ice and clear ice on the same surface. It forms when supercooled water droplets of varying sizes strike the aircraft and freeze in a way that produces both the rough, milky, opaque texture of rime and the smooth, glassy, transparent layers of clear ice. The result is an irregular, rough deposit that is harder to remove than either type alone and that disrupts airflow more severely than rime ice on its own.
Plain English
Ice that is part rough and milky and part smooth and glassy, formed at the same time on the aircraft. It picks up the worst features of both kinds of ice — it sticks well, it builds an uneven shape, and it is difficult to shed.
Context Anchor
Seen in structural icing discussions, especially when flying in clouds or freezing precipitation where droplet sizes and freezing behavior are not all the same.
Derivation
Rime is an old word for frost. Clear describes the more transparent ice that forms when water spreads before freezing. Mixed simply tells you the airplane is collecting both kinds at the same time or in the same area.
Why Pilots Care
Mixed ice is particularly hazardous because it is difficult to remove with de-icing equipment and can significantly alter airfoil shape, reducing lift and increasing drag.
Grounding Statement
Picture the airplane moving through freezing cloud drops: some drops freeze instantly into rough white ice, while others smear back and freeze into a harder clear layer.
Intuition Check
Do not assume “mixed” means mild or less dangerous. Do not assume “clear ice” means there is no ice; it means the ice may be harder to see.
Example Sentence 1
The PIREP from the aircraft ahead reported mixed rime and clear ice between 6,000 and 9,000 feet, so we requested a lower altitude before entering the cloud layer.
Example Sentence 2
Post-flight inspection revealed mixed rime and clear ice on the leading edges after flying through the frontal system.