To non-pilots, it can often seem like pilots have their own language and speak in code. One such instance is when pilots use the word “heavy”.

But why do pilots say “heavy” and what does it mean?

Pilots say “heavy” when they are referring to an aircraft with a Maximum Takeoff Weight of 136 tonnes (300,000 lbs) or more.

Pilots use the term to warn of the potential of wake turbulence, which can be very dangerous.

Why Do Pilots Say Heavy?

It is important that pilots state that the plane they are piloting is big because such heavy aircraft can cause wake turbulence which can be very dangerous for other planes nearby.

So by saying “heavy”, pilots let Air Traffic Control know that the airplane is big and that any other aircraft nearby should leave additional separation to avoid wake turbulence.

Do All Pilots Have to Say “Heavy”?

While the rules may vary slightly in different countries, generally, the “heavy” designation is used for aircraft in the heavy wake turbulence category.

Some countries may require pilots to affix “heavy” to their callsign in all radio transmissions, while others only require it on initial contact with new Air Traffic Service sectors.

Heavy Airplanes & Wake Turbulence

It is so important that pilots say “heavy” to warn of the potential of wake turbulence forming due to wingtip vortices.

Wake turbulence is particularly hazardous during takeoff and landing because the affected aircraft won’t have enough altitude for recovery.

Aircraft with short wingspans are most affected.

At best (or in its mildest form) wake turbulence can cause just slight rocking of the wings of a plane. At worst, though, it can cause a total loss of control of an aircraft.

Other FAA Weight Classifications for Airplanes

The terms “super”, “heavy”, “large” “medium” and “light” are used to categorize aircraft by their weight.

  • Light: Aircraft with a Maximum Takeoff Weight of less than 7 tonnes
  • Medium: Aircraft with a Maximum Takeoff Weight between 7 tonnes and 136 tonnes
  • Large: Aircraft with a Maximum Takeoff Weight of more than 19 tonnes and 140 tonnes. Only used in the USA.
  • Heavy: Aircraft with a Maximum Takeoff Weight of 136 tonnes and more
  • Super: Aircraft with a Maximum Takeoff Weight of 639 tonnes and more

Examples of “Heavy” Aircraft

All wide-body aircraft are classified as Heavy.

This includes many of the most popular commercial airliners, including the Boeing 737, Boeing 747, Boeing 747-8, and Airbus A330.

Several regional planes like the Boeing 757 and Airbus A321 are classified as “Large”.

Private jets like the Learjet 70, Embraer ERJ 145, and Embraer Phenom 300 are classified as “Medium”.

Only the Antonov An-225, Airbus A380, and Scaled Composites Stratolaunch, which is used to carry air-launch-to-orbit rockets, are classified as “Super.”

What is the Minimum Separation Distances for Aircraft By Weight?

According to the FAA, the following is how many miles of separation is required between airplanes of various weight categories:

  • Heavy behind super: 6 miles
  • Large behind super: 7 miles
  • Small behind super: 8 miles.
  • Heavy behind heavy: 4 miles
  • Small/large behind heavy: 5 miles
  • Small behind B757: 4 miles

As you can tell, the minimum distance reduces as the maximum takeoff weights get smaller.

You might have also noticed how there is no separation for Super aircraft listed.

This is because Super aircraft like the Airbus A380 can fly behind any other aircraft without any danger of experiencing wake turbulence.

However, for other reasons, flying just two and half nautical miles behind another aircraft is recommended for a Super aircraft.

Do Pilots Use Other Unique Terms?

Pilots use several other terms that are unique to aviation.

These include:

  • Tree
  • Fife
  • Niner
  • Souls on board
  • Pan-Pan
  • Roger
  • Mayday
  • Feet wet