Definition
A category of in-flight turbulence in which the aircraft is subjected to large, abrupt changes in altitude and attitude, with large variations in indicated airspeed. The aircraft may be momentarily out of control, occupants are forced violently against seat belts, and unsecured objects are tossed about.
Plain English
Very strong, jolting bumps in flight that throw the airplane around enough to briefly take it out of the pilot's full control. People without seatbelts would be thrown around the cabin.
Context Anchor
Seen in weather briefings, pilot reports, and ground training discussions about when to avoid, leave, or prepare for rough air.
Derivation
From Latin 'turbulentus,' meaning 'full of commotion' or 'restless.' 'Severe' comes from Latin 'severus,' meaning 'serious' or 'harsh.' Together they describe air motion that is harsh enough to be a serious threat to the flight.
Why Pilots Care
It can exceed aircraft structural limits, cause serious injuries, and requires immediate speed reduction to maneuvering speed plus possible course deviation.
Grounding Statement
In severe turbulence, the air is moving so sharply that the airplane may be shoved up, down, or sideways faster than the pilot can smoothly correct.
Intuition Check
Do not read “severe turbulence” as simply “very bumpy.” In aviation use, it means turbulence strong enough that aircraft control may be briefly lost and injury or damage is possible.
Example Sentence 1
The crew reported severe turbulence at 12,000 feet over the ridge, and ATC began rerouting following traffic to a smoother altitude.
Example Sentence 2
ATC broadcast a PIREP of severe turbulence at 8,000 feet, prompting the crew to request a higher altitude.