Surely you’ve listened to a chat between a pilot and control tower. They sometimes talk about Heavy, Medium, or Light. You might think they’re just discussing the aircraft type. You’re partially right. But these terms – Heavy, Medium, Light – they’re actually about wake turbulence categories.
When an aircraft takes off or lands, it creates something known as ‘wake turbulence.’ This phenomenon, a type of turbulence that occurs in the wake of an aircraft, is a crucial consideration in air traffic control. The international governing body for aviation, the International Civil Aviation Organization (ICAO), has designed a system to categorize wake turbulence and ensure safe distances between aircraft in flight.
Wake Turbulence Categories
ICAO defines four categories of wake turbulence based on the maximum certified take-off weight of the aircraft. These include Light, Medium, Heavy, and Super. Light aircraft weigh up to 7,000 kg, Medium aircraft weigh between 7,000 kg and 136,000 kg, and Heavy aircraft weigh 136,000 kg or more. The Super category is reserved for specific aircraft mentioned in ICAO’s documents, with the Airbus A380 being the only member as of 2023.
Interestingly, different aviation authorities may classify the same aircraft differently. For instance, the Federal Aviation Administration (FAA) classified the Antonov An-225, a huge Ukrainian cargo plane, as Super, while ICAO classified it as Heavy.
| Category | Designation | Description |
|---|---|---|
| Light (L) | Up to 7,000 kg | Aircraft types of 7,000 kg or less |
| Medium (M) | 7,000 kg – 136,000 kg | Aircraft types more than 7,000 kg but less than 136,000 kg |
| Heavy (H) | 136,000 kg and above | All aircraft types of 136,000 kg or more, excluding Super (J) category |
| Super (J) | Specified in ICAO Doc 8643 | Aircraft types specified as such in ICAO Doc 8643, Aircraft Type Designators |
Ensuring Clear Communication
The categorization system isn’t just for reference; it plays a vital role in maintaining safe distances between aircraft in flight. Pilots of Heavy and Super aircraft must include their category immediately after their call-sign in their initial radio contact with air traffic services (ATS). This alerts both ATS and other nearby aircraft to provide additional separation to prevent wake turbulence.
Managing Safe Distances
The ICAO prescribes distance-based separation minima for aircraft approaching and departing, based on the category of the preceding and succeeding aircraft. The minimum distance can range from 7.4 km to 14.9 km, depending on the type of aircraft involved.
| Preceding Aircraft | Succeeding Aircraft | Distance-Based Wake Turbulence Separation Minima |
|---|---|---|
| Super | Heavy | 9.3 kilometres (5.0 nmi) |
| Super | Medium | 13 kilometres (7.0 nmi) |
| Super | Light | 14.9 kilometres (8.0 nmi) |
| Heavy | Heavy | 7.4 kilometres (4.0 nmi) |
| Heavy | Medium | 9.3 kilometres (5.0 nmi) |
| Heavy | Light | 11.1 kilometres (6.0 nmi) |
| Medium | Light | 9.3 kilometres (5.0 nmi) |
Additionally, there are time-based separation minima for aircraft landing, ranging from 2 to 4 minutes depending on the types of aircraft. These regulations help to prevent accidents caused by wake turbulence.
| Aircraft Landing | Landing Behind | Time-Based Separation Minima |
|---|---|---|
| Heavy | Super | 2 minutes |
| Medium | Super | 3 minutes |
| Medium | Heavy | 2 minutes |
| Light | Super | 4 minutes |
| Light | Heavy or Medium | 3 minutes |
Wake Turbulence Groups
In addition to the categories, the ICAO also has wake turbulence groups based on wing span and maximum takeoff mass. There are seven such groups, ranging from A to G. These groups help further refine separation requirements between aircraft, increasing safety and efficiency in air travel.
Wake Turbulence Through the Years
Wake turbulence categories have been around since at least 1996, with the Super category being introduced by ICAO in 2020, although the FAA had already introduced it in 2014. This system has evolved over time, with constant updates and improvements based on experience and technological advancements.
The categorization and grouping of wake turbulence continue to be a pivotal aspect of air travel safety, playing a crucial role in maintaining safe distances between aircraft in flight. The advancements made by ICAO, FAA, and other authorities help ensure that air travel remains safe and efficient.
First love never dies. I fell in love with airplanes and aviation when I was a kid. My dream was to become a pilot, but destiny led me to another path: to be an aviation digital media content creator and a small business owner. My passion for aviation inspires me to bring you quality content through my website and social accounts. Aviation is indeed in my blood and blog!
