General
As mentioned in the Academy an emergency is a situation as determined by the pilot. He knows best the situation of his aircraft and therefore he will decide what he finds necessary seen the circumstances.
In VATSIM,
to alert ATC properly it is recommended as soon as possible to squawk 7700 (unique emergency code).
This action is additional to any (further) report on a radio frequency.
When the pilot is on an active ATC frequency, he will use that active radio frequency.
If not under control of ATC, the GUARD frequency (121.5) shall be used to attrackt attention of any ATC around.
Be advised, in principle the use of GUARD in VATSIM is text based.
If the pilot did not squawk 7700 yet, ATC will ask him to do so.
Proper recognition of an emergency present in the airspace is advisable.
For ATC,
it is recommended to always hand over emergency traffic to the next controller in sequence.
Prior to that, proper coordination between the two ATC units concerned shall take place to allow the receiving controller to prepare to the situation of receiving an emergency.
The aim here is to allow as many as possible controllers to gain experience in the handling of emergency traffic.
Note: An emergency can exist in many ways and under many diferent circumstances. Therefore only general guidelines can be made. For the rest the ATC in charge has to use his experience and his own judgement about the ongoing situation.
For details please refer to the chapter about Emergencies