about the separation between departing aircraft and the following landing aircraft
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!