Definition
An ICAO wake turbulence category for aircraft with a maximum certificated takeoff weight of 300,000 pounds (approximately 136,000 kg) or more, whether or not they are operating at that weight during a particular flight.
Plain English
A big airplane — one certified to take off at 300,000 pounds or more. Once an aircraft falls in this weight class, it is always called 'Heavy' on the radio, even when it is flying lighter.
Context Anchor
You will hear this in air traffic control communication, often as the word “Heavy” after an aircraft’s call sign, and in discussions about spacing behind large aircraft.
Derivation
Heavy comes from an old English word meaning weighty or hard to lift. In this FAA use, the important point is that “heavy” refers to the aircraft’s approved takeoff weight capability, not just how much weight it happens to be carrying today.
Why Pilots Care
Following too closely behind a heavy aircraft risks encountering wake turbulence strong enough to cause loss of control.
Intuition Check
Do not read “heavy” as simply “loaded heavily today.” In this context, an aircraft is Heavy because of what it is capable of weighing at takeoff, even if the specific flight is lighter.
Example Sentence 1
Example Sentence 2
The controller identified the 747 as heavy and assigned us a two-minute delay for wake turbulence.