What are aircraft categories? ​

Not all aircraft fly the same. A Cessna 172 and an A380 are both airplanes, but they climb differently, cruise at different speeds, approach at different speeds, and leave very different wake turbulence behind them. Aircraft categories exist to capture these differences in a single letter.

Weight-based categories ​

Aircraft are classified by maximum takeoff weight into four wake turbulence categories:

The boundaries aren't arbitrary. They correlate with how much wake turbulence the aircraft generates and how susceptible smaller aircraft are to that wake.

Performance differences ​

Category drives performance in ways controllers need to understand:

Climb rate. A light aircraft might climb at 500-1,000 feet per minute. A medium jet climbs at 2,000-3,000 fpm when light, less when heavy. A fully loaded B777 at high altitude might manage 1,000 fpm or less. This affects how quickly you can get altitude separation after departure.

Speed range. Light aircraft cruise at 100-200 knots. Medium jets operate in the 250-450 knot range (IAS varies with altitude). Heavies cruise at similar or slightly higher speeds at altitude but are much faster on approach. You can't slow a B747 to 150 knots on final - it'll fall out of the sky. A Cessna can't go 250 if you wanted it to.

Approach speed. This is where categories hit controllers hardest. Light aircraft approach at 70-90 knots. Medium jets come in at 130-150 knots. Heavies approach at 150-170 knots. A Super A380 is even faster. When you're sequencing a mix of categories to the same runway, these speed differences create compression - the heavy in front is fast, the regional jet behind is slower, and the gap changes throughout the approach.

Runway occupancy. Bigger aircraft take longer to land, slow down, and clear the runway. A Cessna can touch down, brake, and turn off in 2,000 feet. A B747 needs 6,000+ feet and takes 45-60 seconds to clear. This affects how tightly you can pack arrivals.

Wake turbulence spacing ​

The main reason categories exist. Heavy and super aircraft generate powerful wingtip vortices that can flip a smaller aircraft. Controllers must apply minimum spacing:

• Behind a Super (J): 6nm for heavy, 7nm for medium, 8nm for light
• Behind a Heavy (H): 4nm for heavy, 5nm for medium, 6nm for light
• Behind a Medium (M): 4nm for light
• Same category or larger behind smaller: standard separation (3nm terminal, 5nm en-route)

These minimums often exceed standard radar separation and become the limiting factor for runway throughput. An airport handling all mediums can run tight spacing. Mix in heavies and the required gaps grow, cutting capacity.

How controllers use categories ​

When you look at a traffic sequence, the wake category letters tell you what to expect. A line of M, M, M, H, M, L means: standard spacing, standard, standard, then extra gap behind the heavy, then extra gap behind the medium (for the light). You plan the sequence around the gaps.

Heavies also need to be at their assigned altitude before you can clear someone else through. A heavy climbing slowly at FL310 blocks you from descending other traffic through that altitude until they're past.

In radarcontrol.io ​

Aircraft have wake turbulence categories visible in the data block as L, M, H, or J. The category determines the aircraft's performance profile - heavies climb slower, approach faster, and need more space.

The sim uses realistic performance data from the OpenScope aircraft database. Each aircraft type (B738, A320, B77W, A388, etc.) has its own climb rate, speed range, approach speed, and acceleration characteristics. You'll feel the difference when a fully loaded heavy takes forever to climb versus a light medium jet that rockets up to altitude.

Wake turbulence spacing is part of the separation system. The sim tracks categories when checking for conflicts, so you need to maintain proper wake spacing behind heavies and supers. Getting a mix of L, M, and H arrivals onto a single runway with proper spacing is one of the more satisfying puzzles in approach control.

One limitation: the sim doesn't model actual wake vortex physics (vortex drift, decay time, wind effects on vortex movement). Spacing is distance-based, matching the standard ATC rules rather than simulating the aerodynamics behind them.

Related: What is wake turbulence? | How arrivals are sequenced | How does ATC separation work?

Guides: Arrivals guide | Command reference

Play Atlanta TRACON - one of the busiest airports, mixing heavies and mediums on parallel runways.