Originally Posted by
jmmoric
The standard surveillance separation is 5 nm, or any other depending on the minimum separation the unit has. And that is the surveillance separation between arrivals and departures as well.
What most approach controllers do, is either by standard agreement between TWR and APP, or individually, release aircraft with reference to arriving aircraft. Then the TWR controller can apply "reduced separation in vicinity of an airport", hence see both aircraft and determine there is no risk of collision, and thereby get well below normal surveillance separation.
On days with bad weather, where the "vicinity separation" also known as TWR-separation, cannot be used, there are a few "procedural separations", like the departure has to depart before the arrival reaches 5 NM final etc. Most TWR controllers will gladly accept releases with reference to arriving aircraft, and apply whatever separation is available depending on weather.
40 kts? It says 40 kts.... so the speed difference has to be 40 kts... if you take the TAS from their flightplan, I'd say you need to have a chat with your OJTI again.... But that could vary from place to place... but the way I was taught was we consider actual speed of the aircraft. (I've seen TAS from the flightplan used during basic training, just for the students to get a feel for it, and not "overburden" them)
but in non-radar environment or just procedural control environment , how can you know in real time the actual speed of a departing aircraft the speed of which is increasing ?