Hi vfr880i
Restrictions on simultaneous operations on parallel runways depends on the spacing between the runways and this is a major factor to be considered when planning runway positions. The document best able to explain this is ICAO DOC 9643, otherwise known as the SOIR document.
Under ICAO rules, independent parallel approaches would be available at Heathrow if we provided a second final director and a separate monitoring controller to ensure safety in the event of wander. There would be environmetal implications to this because at present vertical separation would have to be maintained until within 10nm from touchdown; essentially this means that the environmetally friendly Continuous Descent Approaches would not be available. The possibility of increasing this range is currently being addressed to the regulator so that CDAs can be achieved.
Parallel departures are permitted when the initial departure tracks diverge by at least 15 degrees and are subsequently separated by radar.
Using each runway for arrivals and departures (mixed-mode) is under consideration for Heathrow now. The separation of missed approaches from previous departures is a significant issue but is resolved by enabling the Tower controller to turn the missed approach away from the initial departure track. This happens quite regularly at Gatwick, where the single runway enables significant turns to be made. At Heathrow there is less room for this because of the other runway but it is still possible. The third runway makes it even more interesting!
1035m is the minimum separation needed if independent parallel approaches are to be made, 915m for dependent parallel approaches (2nm staggered).
Hope that is useful, come back to me if you need more.
Kind regards
Point 4
P.S. During your interview don't call them planes, it comes across as slightly unprofessional, call them aircraft