ICAO mandates separation minima based upon wake vortex categories that are, in turn, based upon the Maximum Take Off Mass (MTOM) of the aircraft.
These minima are categorised are as follows:[1]
Light – MTOM of 7,000 kilograms (15,000 lb) or less;
Medium – MTOM of greater than 7,000 kilograms, but less than 136,000 kilograms (300,000 lb);
Heavy – MTOM of 136,000 kilograms or greater.
There are a number of separation criteria for take-off, landing and en-route phases of flight based upon these categories. Air Traffic Controllers will sequence aircraft making instrument approaches with regard to these minima. Aircraft making a visual approach are advised of the relevant recommended spacing and are expected to maintain their own separation.
The FAA does not use the ICAO categories for wake turbulence separation[2], instead using the following:
Edit 11/26/10 from
http://www.faa.gov/documentLibrary/media/Order/ATC.pdf pdf page 616 document page BG-8
"Appendix A is being revised to harmonize FAA weight category standards with those of the International Civil Aviation Organization (ICAO). All aircraft with a maximum certificated takeoff weight of more than 41,000 pounds but less than 300,000 pounds maximum certificated takeoff weight will now be classified as a “Large” aircraft according to FAA standards. Aircraft with a maximum certificated takeoff weight of 300,000 pounds or more will now be classified as a “Heavy” aircraft according to FAA and ICAO weight classification standards. This change reclassifies all B757 aircraft as “Large” aircraft; however, controllers are required to apply the special wake turbulence separation criteria as specified in paragraph 5-5-4. This change cancels and incorporates N JO 7110.525, Appendix A, Aircraft Information Fixed-Wing Aircraft, effective April 8, 2010."
Super - A separate designation that currently only refers to the Airbus A380
Heavy - Aircraft capable of takeoff weights of 300,000 pounds (140,000 kg) or more whether or not they are operating at this weight during a particular phase of flight.
Large - Aircraft of more than 41,000 pounds (19,000 kg), maximum certificated takeoff weight, up to but not including 300,000 pounds (140,000 kg) .
Small – Aircraft of 41,000 pounds or less maximum certificated takeoff weight