Airway width/wx deviation
Input on the following query would be appreciated :
Assuming I am on an e.g. Oceanic airway of an 8 NM width, 4 NM either side of me and I need to deviate around a small CB, lets say two miles right of course, do I need ATC approval ? Will a say 30 degree heading change for that CB trigger bells and whistles on your screen ?
And what if I am closer to a terminal area, lets say on a STAR where the airway,or tolerances,are considerbly tighter, can I still sneak left or right in the same fashion without ATC approval ?
The above statements assume I am aware of the width of the airway I am on. My airplane's FMC will inform me what the required RNP is of the airspace/airway I am on and it narrows down as I transition from say Oceanic airspace of 4 NM to Domestic airspace of maybe 2 NM down to 0.3 NM when I am on the approach.
Do ATC have a similar concept of "narrowing" airway width or navigational tolerances as I approach a terminal area ?
Regards