Separation behind a 757 - Our manual says 2 minutes for
lighter types from the same departure point, or 3 minutes from an intersection. For other Medium vortex types or Heavies following there is no vortex minima, just route separation. This can sometimes be "wheels up".
We are very aware of the possible problems caused by the 757 and that some companies require a 2 minute minimum when following a 757 regardless of type - even a 767 pilot asked me for 2 minutes once.
If we intend to use a 1 minute separation behind a 757 it has become good practice to ask you first if you will accept it before you are lined up. It would be nice if you could tell us in advance if you need more than 1 minute in case we forget!
In the UK there have been no reports of wake vortex encouters behind a 757 on departure. Is this because we use 2 minutes sometimes or because there is less of a risk on departure than on arrival?
I believe that in Oz the 757 is categorised as a Heavy if leading and a Medium if following.
In the US it has its own wake vortex group and is considered to have the properties of a Heavy. US departure separations can be distance based (4 miles) rather than time. When time is used it is based on start of roll. Confusing!?
See <a href="http://www.pprune.org/cgibin/ultimatebb.cgi?ubb=get_topic&f=41&t=002107&p=" target="_blank">Vortex Wake and the 757</a> from a few months ago.
Edited to add link
[ 28 December 2001: Message edited by: cossack ]</p>