I always thought that aircraft with "Heavy" added to their callsign were anything large (e.g. anything larger than an A318, A319, A320, A321, and all kinds of 737)... 

it is to designate the aircraft that cause large amounts of turbulence. the 757's unusually powerful engines also give it a heavy designation.

Actually I do believe it is determined by takeoff weight isn't it?  I'm not sure what the threshold is for the heavy designation though.

It's an old traditional phrase coined by 'surfer dude' pilots that weren't looking forward to the flight, as in "Wooagh, heavy man" - it has since been shortened to 'heavy' in an effort to keep busy communications frequencys free of 'surf talk' - man

See you at the beach dudes

TSC.

Officially, "heavy" as regards ATC parlance refers to aircraft which, at the time they are being handled, weigh over 300,000 lbs. gross.

There may be some airliners that have legally operational weights below 300,000 but GTW or GLWs at or above 300,000, which would explain the ATC option in FS9.

I've yet to hear any arriving airliner not referred to as "heavy" by the crew or controllers in all the time I've been monitoring my local approach and tower freqs, however.

Generally, "heavy" is the only weight reference made in ATC communications... not sure why, exactly, as any airliner is obviously heavy enough for concerns about wake turbulence, etc., whereas an inexperienced light-single pilot flying into a controlled field may not realize that that loaded Caravan or Gulfstream in front of him is heavy enough to upset his little trainer with its wake turbulence...

Here's a weight-reference list from some ATC training pdf. I found online:

 
Heavy: Gross weight greater than  300,000 lbs.
Large: Gross weight greater than 12,500 lbs. but less that 300,000 lbs.
Small: Gross weight less than 12,500 lbs.

beefhole wrote on Dec 12^th, 2006 at 1:53pm:



It's the weight. Wingtip vortices (which are the most dangerous component of aircraft wake turbulence, although not the only component) are almost entirely dependent on weight, in terms of their intensity. Wings can be designed to minimize the effect somewhat (and yield better cruise efficiency), but in most cases, it's all about gross weight, not wing shape or length.

Airspeed figures into it only because when climbing or descending, the ratio of weight to lift and thrust to drag changes, causing much more kinetic energy to be released at the wingtips than during cruise, when the wing isn't working quite as hard. And a wing works hardest when it has a heavy load and not much airspeed to help generate lift.

With flaps down, the wing now has more camber, and will get more lift with less airspeed, and the energy of the wingtip vortices will be reduced somewhat. This is why the most dangerous tip vortices are off slow, heavy planes in a clean configuration... such as climbing out or intital descent just prior to lowering gear and flaps.


http://en.wikipedia.org/wiki/Wingtip_vortices

beaky wrote on Dec 12^th, 2006 at 2:19pm:

Either way Rotty, as far as I know, ALL 757s get the designation 'heavy', regardless of weight.