I was in the tower working GND at the time and saw the airshow. It was most impressive if a little bizzare looking to see something approaching 09L turning hard right. I think the first two a/c turned right and the next headed north...only for the policeman to suddenly head back north east away from the field!!!
Dizzee
We do obviously use the MATS standard phraseology if we want someone to do something standard, like the standard MAP. In this case, however, I would agree with Roffa and start with an (brief!!) explanation of what you're doing and why, followed by turn/climb instructions (i.e. "c/s i'm going to have to break you off this approach due to category B traffic approaching from the north, so turn right now heading 180, climb to 3A") But the climb should definitely be in there somewhere!
Ham
It wasn't a trainee in the seat at the time but I reckon the suddenness of it all happening came as a surprise to the controller involved and unfortunately the climb insruction was forgotten. Did the controller go back into you later on to tell you to climb?
Nigel
I'm also with HD in that the possible missing of subsequent calls due to headsets is a worry!!
What if the subsequent call is for traffic information or more importantly, avoiding action??
FB
