The ICAO wake turbulence category (WTC) is entered in the appropriate single character wake turbulence category indicator in Item 9 of the ICAO model flight plan form and is based on the maximum certificated take-off mass, as follows:
J (Super) aircraft types specified as such in Doc 8643 (Aircraft type designators). At present, the only such type is the Airbus A380-800 with a maximum take-off mass in the order of 560 000 kg. (see Airbus A380 Wake Vortex Guidance)
H (Heavy) aircraft types of 136 000 kg (300 000 lb) or more (except those specified as J);
M (Medium) aircraft types less than 136 000 kg (300 000 lb) and more than 7 000 kg (15 500 lb); and
L (Light) aircraft types of 7 000 kg (15 500 lb) or less.
Variants of an aircraft type may fall into different wake turbulence categories, (e.g. L/M or M/H). In these cases, it is the responsibility of the pilot or operator to enter the appropriate wake turbulence category indicator in the flight plan.
State Variations to ICAO Wake Turbulence Category
States may elect to operate variations to the ICAO scheme if they wish. One example of this is the UK where the main differences are the re-definition of the lower weight end of the ICAO ‘MEDIUM’ category:
An extra category called ‘SMALL’ is defined as aircraft types with an MTOM (maximum take-off mass) of between 17000 kg and 40000 kg
The ‘LIGHT’ Category defined in the ICAO scheme is extended to cover aircraft types with an MTOM of up to 17000 kg
In 1997 a further modification was made for the purpose of separation in the approach phase at London Heathrow, London Gatwick, London Stansted and Manchester airports, and at London Luton in 1999, by dividing the Medium category for landing aircraft into Upper and Lower Medium. In light of the safe operational experience over the years since 1997 it was decided in 2010 to extend this categorisation to all UK aerodromes.
ICAO Doc 8643 - Aircraft Type Designators contains designators for those aircraft types which are most commonly provided with air traffic service (ATS) as well as additional information such as Wake Turbulence Category.