Definition
An icing intensity category in which the rate of ice accumulation on an aircraft is so rapid that deicing or anti-icing equipment fails to control it, or ice builds in locations the equipment cannot protect. An immediate change of altitude or course is required to exit the conditions.
Plain English
Ice is forming on the airplane faster than the aircraft's ice-protection systems can remove it. The pilot must leave the area right away.
Context Anchor
Pilots encounter this term in weather briefings, pilot reports, and significant weather advisories when icing conditions may affect a flight route.
Derivation
Severe comes from Latin words meaning serious or strict. Icing means the formation of ice. In aviation, severe icing is not just “a lot of ice”; it is a serious icing level where the airplane may no longer be able to manage the ice safely.
Why Pilots Care
Severe icing can quickly destroy lift and control, forcing an immediate diversion or landing to avoid loss of aircraft control.
Grounding Statement
In severe icing, ice is forming faster than the airplane can safely shed or tolerate it.
Intuition Check
Severe does not just mean “unpleasant” or “noticeable” here. In aviation icing, severe means the situation may be beyond what the aircraft can safely manage, so prompt escape is required.
Example Sentence 1
ATC relayed a SIGMET for severe icing between 8,000 and 14,000 feet, so we requested a lower altitude to stay out of the affected layer.
Example Sentence 2
After entering severe icing the pilot immediately requested a lower altitude to exit the freezing level.