Good evening Frunobulax
I am currently on the development team looking into expansion of Heathrow and Stansted airports and ICAO 9643 is our section "Bible". We are investigating parallel mixed-mode & a third runway at Heathrow and a staggered parallel at Stansted. Our Concepts of Operation for both the Heathrow projects are now mature and we are in discussions with our regulator about relevant issues.
I believe that in effect it doesn't matter whether the two runways are on the same airport or not; what matters is the procedures that separate their operations. I don't believe that 9643 applies in your case. If I have understood your layout correctly then I suggest the following may be appropriate:
All departures from the southern runway must turn south by 30 degrees immediately after take off and the turn must be confirmed by radar or r/t before traffic is transfered from the southern tower frequency. It also seems appropriate that a PRIORITY telephone line between the southern tower and the northern final director is installed as this would be mitigation of any latent risk of navigational error from the arrival or departure.
If you would like to to know more about our experiences in this or if I can help further, please send me a message to that effect.
Point 4
