pilot1957,
Does this mean that if separation is 2 mins and controller estimates that after he gives clearance it'll take following aircraft 30 secs to ack, spool up, then roll to where first a/c rotated he will give it after 90sec?
I can't speak for DXB, but I think that's what TR was saying. That is certainly the case for the UK.
I know that in some areas of Europe, a different method is taken, as you say: The time the first aircraft begins to roll is noted, and then the controller begins to transmit the take-off clearance 120 seconds after the noted time. The theory being that the time taken to transmit, readback, react and start to move should cover any difference in the period between start of roll and rotation.
5milesbaby,
It is a VERY long time since my aerodrome days, however I remember something like if the preceding aircraft is wheels up at 10:00.29 then 10:01.30 is an acceptable "2 minute" departure interval. Is that still the case or should the book now state "120 seconds" to make it precise?
The book still says 2 minutes, although the requirement has been 120 seconds as far as I remember. The time marking on paper strips used to be HH:MM which could have lead some to use the 'ATC minute'.
With our EFPS, when the controller selects a strip as airborne, it automatically records MM:SS on the strip, which is very useful for judging the next clearance.