Heathrow takeoff routes - variations?

[oversteer]

I live quite close to the northern half of the Heathrow 27 takeoff routes (near Slough), where departing traffic usually follows quite a predictable path, northward toward Wycombe or northeast over Watford, turning at Burnham.

Last night about 1800, three departures all turned right much earlier than normal, looking at Casper they started turning almost over the QM reservoir.

Just wondering why this was.. pure idle curiosity. Something nasty on the weather radar perhaps? Didn't seem to affect any other traffic before and after.

[HEATHROW DIRECTOR]

The SID off 27R is to be estabished on 300 degrees to Burnham by LON D4, which means they should be turning by QMR. Have a look at the chart here:

http://www.ead.eurocontrol.int/eadbasic/pamslight-D7C0B05CC309D4516231CCF0D3417744/7FE5QZZF3FXUS/EN/Charts/AD/AIRAC/EG_AD_2_EGLL_6-4_en_2010-07-29.pdf

[oversteer]

Yes these were on the 300 towards Burnham but then turned onto north a lot earlier than normal, must have been almost a continuous right-hand turn as they took off. Must have been weather, there was some heavy rain around that day.

[Flightman]

Heathrow "track keeping" is around 95% across all 24 routes. Any deviations are normally Wx related. :ok: