What is wake turbulence?
Every aircraft generates rotating air vortices from its wingtips during flight. These vortices - called wake turbulence - can be dangerous to following aircraft, especially smaller ones behind larger ones.
Wake categories
Aircraft are classified by weight into wake turbulence categories (see also aircraft categories for how weight class affects performance and approach speeds):
| Category | Code | Example aircraft |
|---|---|---|
| Super | J | A380 |
| Heavy | H | B747, B777, A340 |
| Medium | M | B737, A320 |
| Light | L | Cessna, Piper |
Required spacing
Controllers must apply increased separation behind heavy and super aircraft:
- Heavy behind super: 6nm
- Medium behind heavy: 5nm
- Light behind heavy: 6nm
- Light behind medium: 4nm
- Same category or larger behind smaller: standard 3nm (terminal) or 5nm (en-route)
Why controllers care
During approach sequencing, wake turbulence spacing often determines the minimum gap between arrivals. A runway handling mostly B737s can land one every 90 seconds. Mix in a few heavies and the gaps grow, reducing throughput.
FAA RECAT wake categories
In 2012 the FAA began rolling out RECAT (Re-Categorization), replacing the traditional 4-tier system (L/M/H/J) with a more granular 6-category scheme (A through F) based on wingspan and weight. RECAT allows tighter spacing between certain aircraft pairs that the old system over-separated - for example, a B757 following an A380 no longer gets the same spacing as a Cessna following an A380. RECAT is now active at major US airports including Atlanta, Chicago O'Hare, and several others, and has measurably increased arrival rates without reducing safety.
In radarcontrol.io
Aircraft have wake turbulence categories (visible in the data block as L/M/H/J). The simulation uses these for realistic traffic generation. Wake spacing is part of what makes sequencing a challenge - you can't just stack everyone 3nm apart when heavies are in the mix.
Related: How arrivals are sequenced | What are aircraft categories? | How does ATC separation work?