Originally Posted by
good egg
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
All of the RNAV SID trials at Heathrow over the last few years have involved flyby rather than flyover waypoints. That hasn't stopped communities complaining about the concentration of flightpaths. I'd suggest that the net flightpath variations between aircraft types on the RNAV SIDs are an order of magnitude less than those when flying traditional procedural SIDs (which is of course the reason the NPRs are defined as 3km wide swathes).
Originally Posted by
good egg
That's why we see enhanced TBS about to start at LHR.
Out of interest, what are the enhancements relative to the current TBS regime?