Heading at an altitude on a SID

[Bill_Dodsworth]

This is a question for any London TMA controllers. This happens at other times, but the example I'm about to give is the most common I have experienced.
Doing the MID SID from LHR, on contacting the departure controller and having been identified they quite frequently give a clearance: "When out of 4000ft take up a heading of 195 degrees". At this point I am heading about 260 degrees at about 2000ft and as part of the SID I am about to do a left turn onto a heading about 30 degrees east of the assigned 195 degrees.
Are you expecting me to continue straight ahead until 4000ft and then turn left into 195 degrees? or
Are you expecting me to turn left with the SID (going through the assigned heading) and then at 4000ft turn right onto 195 degrees?
Many thanks

[Days of Future Past]

Hi Bill,

SID's are a politcally and noise sensitive subject. The obligations for noise avoidance terminate at 4000ft on departure from Heathrow. There are many noise monitoring sites around the Heathrow area and the ATCO is protecting both his and your backside by not letting you deviate from the SID until 4000ft.

The answer is therefore: continue exactly with the SID until you reach 4000ft and then (and only then) turn onto the heading requested i.e. in this case 195 degrees.

The technique is used in this case to take you away from the OCK stack and addtonally traffic approaching OCK to facilitate an earlier climb.

Hope this helps.

DoFP

[Bill_Dodsworth]

Many thanks,

Nobody I have flown with has been certain about the answer, so I will start spreading the word.

In the unlikely event that the frequency is quiet, it might be worth your chaps including the wording, "Remain on the SID until out of 4000ft and then turn onto heading 195 degrees"; that way the message may get through.

At least I will get it right from now on! :O

[SM4 Pirate]

In Oz I believe we should say, "At 4000 feet, Cancel SID, Fly heading 195"