Originally Posted by
mxwbuaa
in chapter 8 of ICAO doc 4444 -ATS surveillance services, the separation between the departing aircraft and following arrival aircraft is not specified, so, when can the controller in tower can instruct an aircraft to take off based on the position of arrival aircraft on final ? and what's the logic behind it?
and in this article: "Two minutes are required between take-offs when the preceding aircraft is 74 km/h (40 kt) or more faster than the following aircraft and both aircraft will follow the same track" what kind of speed does it mean ? cruising speed or the actual speed in the phase of departure?
thanks!
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)