Originally Posted by
chevvron
Nice one Pax
Although it depends where you put the point merge. If the 'point' of the point merge is at the latest point of the ILS where aircraft are normally vectored to then you get a spread of approach paths up until that 'point'. Beyond that point aircraft with fly the ILS like they always have.
However, if you place that 'point' miles and miles out then you will get an over-concentration of arrival flightpaths from there to touchdown.
It's hardly rocket science.
RNAV departures are slightly trickier....depends on the mix of routings and the amount of 'flyover' waypoints versus 'flyby' waypoints. By designing in more 'flyby' waypoints you get a bigger spread of departure routes....which is better for folk on the ground (less concentration of flightpaths because each aircraft takes a slightly different path, dependant on speed/weight/type etc.) even for the same RNAV SID.
However, not ideal for ATC in terms of 2 consecutive departures on same SID as each aircraft will fly slight variations on the same SID and therefore departure separation becomes an issue.
It's a good option if you can guarantee an alternation between say northerly and southerly departures all day long.
For the arrivals, if you had to have a point merge miles and miles from the airport (airspace limitations), you'd ideally have at least 2 routes to touchdown from the merge point....offering alternation (or 'relief routes') to residents on the ground.
Not always that simple though to design such structures. But certainly fairer to the communities underneath.