LGW SIDs, East, Northeast off 26L
 

Is there a fundamental difference in geographical routing between the original LAM/CLN departures of 26L and the RNAV1 SIDs? The reason I ask is that living in Redhill, we are subject to regular overflight, particularly evening departures from LGW. (In context, I am ex BA B737/DC-10 flying shorthaul and longhaul from LGW) Also AD 2-EGKK-3-1 shows the noise preferential routings but the notes for the RNAV1 plate says, "RNAV1 SIDs reflect NPRs". Have these flight paths changed when they previously avoided this area and if so why?
Many thanks for any answers.

NPRs at designated airports can only be changed by the Government, and that would require public consultation, so that can't be the reason for what you're seeing.

An aircraft flying the conventional SID, which strictly speaking is a procedure rather than a routing, can wander up to 1.5km either side of the nominal NPR centreline before it's considered "off-track".

An RNAV1 SID, on the other hand, is a route that approximates the NPR by defining a series of waypoints which, as Heathrow residents have found over the last couple of years, are flown much more precisely, the effect being to concentrate traffic (and therefore noise) over a much narrower swathe than the 3km wide NPR

If you are experiencing flights that are considerably adrift from the conventional NPR, that should be reflected in Gatwick's published track-keeping stats.

The new SIDS are slightly different in that they turn back closer to the centreline (very useful������) but as approximately 95% of the time they are put on headings as they turn the corner, I would imagine that fact has passed nearly everyone by.

Is it possible that this is due to the area being even more saturated for far more periods of the day? Subsequently the aircraft are following the same track more and more, rather than having more quieter times previous where a few directs or headings off SID were more common?

As I thought, "heading select", from ATC, during the turn radius but surely the ATCO has to give a heading to achieve a track within the NPR? Is there a commercial or operational advantage to either ATC or an aircraft operator, to limit the bank angle and fly a wider turn? (In my day on the DC-10 this was classed as a "close in turn" and not easy to fly with a heavy aircraft).
PS to the above. A quick look at flight radar shows several departures off LGW 26L , following the NPR precisely. However the LHR south east traffic is routing via Redhill! Perhaps that's the problem, albeit with a much higher altitude.

As with any NPR, the requirement to stay within the 3km swathe only applies until the aircraft reaches 4000 ft.

<<However the LHR south east traffic is routing via Redhill! Perhaps that's the problem, albeit with a much higher altitude.>>

They'll be on radar headings at that time.

Having experienced living in this area in the past I remember noticing the LHR outbounds more than LGW as many were long haul and slow climbers. Presumably they are vectored towards LGW before turning more to the east to avoid conflict with the Biggin inbounds. Also when traffic allows, eg mid-late evening when LHR arrivals start to reduce, sometimes LGW 26L outbounds on right turn out on northbound SIDs are vectored north early tracking towards just east of LHR and these may affect your area.

Thanks for all your replies, My partner (writer and retired social work manager) was shocked at the traffic intensity when I showed her "flight radar"! Pembroke

There's a restriction that no gatwick departure may be vectored over Horley (small dotted area displayed on radars) regardless of height, but no such restriction applies to Heathrow departures, for example westerly detling departures leaving Epsom on approx 130degrees, level at, or even climbing to 6000'. So a Far East bound Heathrow heavy at perhaps 5000'(if the controller is feeling brave) is fine, but a light Manchester bound shuttle out of FL100 is not. Go figure...