Bedder Believeit
To HKG Phooey, I forgot to mention in the response to your request for auto freq transfer on Departure. When RWY 07 is in use (the bulk of the time over the course of a year) the overshoot path for aircraft on RWY 07L ILS/D app is not quite separated from the SID Departure path for an aircraft departing RWY 07R. Therfore if an aircraft performs a missed approach on 07L, at the same time as an aircraft is becoming airborne off 07R, then both aircraft can be kept "in house" (in this case the Tower) so that a suitable vertical (and visual) separation can be implemented by the two concerned controllers (118.4 and 118.2) before transfer to Departures (123.8). Obviously two differing requirements might be: Situation 1. A heavy cargo aircraft overshooting on the North RWY against a lightish medium flight to nowhere climbing like a rocket off 07R, we may instigate an altitude restriction on the freighter, and get the light departure to expedite climb. Situation 2 would be the exact reverse. This is also one of the reasons why we are reluctant to approve requests for practice VOR/D approaches onto either 07L or 25R as the overshoot paths are both "Maintain Runway heading", and it means that we lose a departure slot. Whilst this in itself is not critical, the aspect of having to make the decision at such an early stage when you request the approach means that the system does not often know how many departures may be taxiing out. This may explain why you don't always get your request.