Co-ordination between en-route controllers.

[OhNoCB]

Wondered about this last week when the below exchanges happened a couple of times.

Situation; currently being vectored en-route flying heading 160

"ABC own navigation direct CLIPY, contact London Control on xxx.xxx"
change freq
"London Control ABC FL90 direct CLIPY"
"ABC roger turn left heading 160"

This makes me wonder what coordination goes on between the two en-route controllers, as I would have thought the first one would arrange with the next one for the direct routing into their sector, and it seems strange to go straight back to the previous vector on transfer. Would reasons would often be behind this?

[tczulu]

Probably the offering sector had you on a heading to provide separation against traffic in their airspace and when you were clear of conflict then sent you own navigation to the next waypoint. The receiving sector then obviously needed you on a heading against traffic that was unknown to the transferring sector. Personally,if I have traffic on a heading pointing in generally the right direction,I transfer it on the heading to avoid situations as you have hilighted.After 40+ years only 26 working days to go!

[DTY/LKS]

Usually when an aircraft is transferred on a heading then the receiving sector cannot turn that aircraft until it is in the confines of the receiving sector without making a phone call.
As tczulu says, Sector A would have had you on a heading against traffic for separation purposes then released you back on your own nav before transfer to Sector B. This means that on contact with Sector B they could put you on any heading to suit them for separation, even though you may still be in Sector A's airspace.
You can "second guess" what heading the next sector may want but as each controller is controlling their own piece of airspace, then by being put on your own nav to CLIPY then Controller A was giving Controller B the freedom to put you on any heading he required (if any) without needing to get you released for turns.
It just so happens that this time both controllers wanted you on 160

Hope that helps.

[OhNoCB]

Thanks so much for the replies. Always good to further the understanding of the system. Was never before aware of the difference in that regard between an own nav and a heading on transfer. Very good stuff.

[zonoma]

For the majority of transfers, no verbal coordination will ever take place. You could be either subject to a standing agreement (being cleared to or at a specific level) or at a coordinated level. The coordinated level can be done electronically between some sectors and if not, the telephone call may just be to agree the level. Unless coordinated, it is agreed that you will be on your own navigation or on a heading along the anticipated route and then you are subject to what DTY/LKS describes. As you can imagine, there are many procedures that we follow which cut the workload down as much as possible and coordination is one of the big refinements.