Definition
Liquid water that remains in the liquid state at temperatures below 0°C (32°F) instead of freezing. The water is unstable in this condition and will freeze almost instantly when it strikes a surface, such as an aircraft in flight.
Plain English
Water droplets that are colder than freezing but still liquid. They turn to ice the moment they hit something solid, like a wing or propeller.
Context Anchor
Seen in aircraft icing, freezing rain, and maintenance discussions about ice forming on aircraft surfaces.
Derivation
From 'super-' meaning 'beyond' and 'cooled,' so literally 'cooled beyond' the normal freezing point. The name signals that the water has been chilled past where it would usually freeze, yet has not done so.
Why Pilots Care
Supercooled water droplets freeze instantly on contact with an aircraft surface, creating ice that changes wing shape and reduces control effectiveness.
Analogy
It is like liquid water that is ready to freeze but has not had the right contact point yet. The aircraft surface can provide that contact, so the water turns to ice on impact.
Grounding Statement
Imagine flying through a cloud at –5°C; the cloud is full of liquid droplets that look harmless, but each one freezes onto your wing the instant it touches.
Intuition Check
Supercooled does not mean the water is already ice or simply “extra cold.” It means the water is still liquid even though its temperature is below freezing.
Example Sentence 1
The pilot avoided the cloud layer because it likely contained supercooled water that could cause rapid airframe icing.
Example Sentence 2
Forecasts warning of supercooled water help crews decide whether to activate de-icing equipment before departure.