Heathrow SIDs
 

Not really a professional quwstion so asking here not ATc.

LHR SIDs havent changed materially all that much over a good few years in terms of tracks but I have often wondered that with improved aircraft climb performance the former Clacton now Brookmans Park SID doesnt mirror the Dover departures of the 27s which have a hard left of about 120 degree turn close to the airport boundary LHR and then a further turn south of Staines .

departures headed north easterly though make only a small 30 degree or so right turn for Burnham north of Slough and then another turn over a notional point, Chiltern, then head NE passing just north of Watford and on eastwards. so roughly similar but with a much wider radius for those going via BP

Obviously there is a good reason for them being different I just wondered what it is
PB

The first part of each SID, up to 4000 feet, is defined as the Noise Preferential Route (NPR).

NPRs, as you rightly say, have remained unchanged for many years and neither Heathrow nor NATS has the power to change them, only the Government.

The historical reasons for their routes are lost in the mists of time, but they were likely defined to take account of issues like populated areas, etc, as they were in the 1960s. A further reason why the BPK SID doesn't mirror the tight turn of the DET SID could be potential conflict with Northolt traffic.

You would probably get a more definitive response if you did ask in the ATC forum - they are quite friendly over there. :O

The answer could be NIMBYs.
A couple of years ago, a new departure route for southbound traffic was trialled so that instead of Heathrow departures going over the Woking area, they went over Ascot instead.
There were widespread compliants from the Ascot/Bagshot/Windlesham area and the routes reverted to the original ones.

I'm not sure that answers the OP's question about why the NPRs/SIDs were put where they were in the 1960s, though it does illustrate the difficulties faced by any proposal to alter them, even on a temporary basis

It was always planned that the trial would only last for 5 months, from August 2014 to January 2015, before reverting to the original MID SID, but such was the public opposition to the trial that it was terminated two months early, in November 2014.

thanks all and indeed i had heard long ago that it was something to do with Northolt , and I will ask in the ATC forum as you sat they are generally an open minded lot there.

I remember the fuss over noise a few years back having attended a public meeting on it where people made astonishing claims about being kept awake all night by the chanegs-of course there are no departures from LHR much after 10 30 or so.

On the other hand NATs?HAL didnt do themselves any favours insisting that all flights over Bagshot were well over 6000 feet overlooking the fact that a considerable number of BA pilots live in the area and were brought up short by a A320 captain who said that he routinely overflew his house at 6000 ft to avoid conflict with inbounds-and as to fate it seemed BA chose the evening for a specially heavy LHR-Capetown 747 to struggle 'low' and noisily over the meeting hall

ATCOs obviously have it easy nowadays with BA pilots doing their own separation!!

Is there an altitude restriction on the left turn (Dover?) SIDs off the 27 runways? I ask as when I'm in my usual parking space on the M25 the ones that turn hard left after take off always seem to stay low to my eye compared to departures that head west or turn right

Aerospark, I have always assumed they are held low when necessary to get underneath the Epsom hold and occasionally the Biggin hold, and the traffic from both routing to join the approach. Presumably Gatwick traffic also can have an effect on outbound altitudes and routings which seem to vary considerably throughout the day.

Incidentally, I was awake very early this morning and had a squizz at Flight Tracker; seemed to be more than usual amount of heavy traffic in all four Heathrow holds; wonder if there was a delay or perhaps some of the trans-Atlantics had very favourable winds...

HD

I should point out that he meant nothing like that-quite the opposite in fact that he was frequently only cleared to 6000 quite properly to stay beneath the inbounds headed for Ockham.

As to altitudes i have often depatrted LHR on both these routes and it seemed quite common at busy times to stay at 6000ft until past Biggin let alone Epsom and much the same going north to stay below Bovingdon

PB

The only close-in altitude restriction on the published Dover (actually DET) SID off the 27s is to cross the Epsom NDB at or above 4000 ft.

AeroSpark

Like you when I watch from the M25 car park the 27 take-offs on the left turn to Detling do appear low but maybe it's because the turn starts very early which enhances the low altitude impression and of course many modern "heavies" use de-rated power for take-off on such long runway lengths so they will be low anyway, I remember living in Egham area in the early 70's and to watch and listen to Cyprus Airways and BEA Trident 2's on the Dover departure off 27's (28's then) to Greece and Cyprus was ear splitting to say the least but exciting all the same,

What also might be a factor is that the end point of the DET SID is relatively a long way from LHR, so modern FMSs will moderate the climb rate. If the end point of the SID was brought closer to the airport (truncations, which have already occurred with WOBUN/BUZAD changing to UMLAT/ULTIB and SAM changing to GOGSI/GASGU) then this might result in steeper climb gradients.

Yes, although the GOGSI/GASGU height restrictions haven't changed from the old SAM SID, the ULTIB SID in particular has the "5000 ft or above" restriction at 13 nm along track, whereas the same restriction on BUZAD was at 18 nm.

Best 'low turn' I saw out of Heathrow was one day when I happened to be in a coach on the M4 eastbound; a Concorde departed 09R and commenced a right turn (presumably departing via BCN) at what seemed to be below the height of T4.

09R departures
 

May be related to the fact that BA419 LUX-LHR was carrying out a go-around on 09L as the QF was taking off from 09R.