Pub User,
As ex Mil aircrew, then in twilight years of mil career as an ex mil ATCO.. now a civ ATCO, avoiding action should not be a rate one turn - it is more urgent and is given to either maintain standard separation or, worst case scenario, to avoid collision.
If a pilot is instructed to turn under a normal instruction, he should do this straight away, (after the usual Clear left/right check and reply to ATC), using a rate one turn.... saying that Avoiding Action means turn straight away on a rate one turn implys that pilots are encouraged to hang about and dither when given normal vectoring instructions - not true, a vector turn is given for a reason, be it for spacing in the radar pattern or long range conflict resolution... it is an INSTRUCTION, not a suggestion!!!
Plain*Jane
Avoiding action should be given to avoid confliction or to maintain minimum separation, be it 5 or 3 miles or 1000 or 3000 feet and is therefore to be acted upon straight away with as much as the pilot can give us.
Avoiding Action is not ideal - conflicts should be resolved well ahead, but this is not always possible (pop up traffic, poor radar performance and even (may I say it) controller workload to name a few excuses).
MATS part 1 (JSP318A for Pub User) states that the minima are just that and can be reduced on a few occaisions - Loss of searation being one of them - however if a loss of separation situation is about to happen, then avoiding action should be used. It should be given in ample time to ensure that the action will be effective i.e. controllers should not sit and watch a situation unfold before giving avoiding turns at five miles!!
Other users may have heard mil controllers giving avoiding action to A/C about to enter CAS without authorisation... it may be pop up traffic that is fast moving, and a HARD turn is what is required to remain clear - again a justifiable and sensible use of avoiding action.
The phrase "C/S avoiding action C/S turn HARD right/left immediately....... "is not standard phraseology.. the HARD part is non standard, as pilots should be giving avoiding action the best rate of turn available at all times (with due consideration to A/C performance).. however the 'hard' does creep in because some ATCO's feel it neccesary to amplify the urgency.
Unfortunately, and civil pilots may correct me here, maybe what ATCO's expect and what pilots believe to be expected of them differ, in a large part, due to company policy??
If I, however, was a pilot of a fully laden passenger jet and was given avoiding action, I would go all out to give the hardest turn and worry about the passengers afterwards - at the end of the day, it would also be my own life I was possibly saving!