It baffles me how completely oblivious a few individuals in this forum are to the difference between excersing the rights of PIC, and normal operations:
The whole "I can do whatever the hell i want because it's my aircraft" attitude sickens me. Yes; in the event of an emergency it is the commanders obligation and right to do whatever he can to ensure the safe and successful outcome of the flight. This does not mean you can do as you please, all the time, when it is completely unwarranted.
Since when in Gods name do you "request" a deviation which if not done will take the bloody wings of?
Since when in Gods name do you, as a responsible individual, adress the situation so late? Did that big CB just all of a sudden pop out of nothing, leaving you only one option? Surely, don't allow yourself and your passengers to get killed, but how the hell did you paint yourself so far into that corner in the first place?
Such knee-jerk reactions can cause safety hazards for not only you, but for other aircraft. By adressing the problem at an early stage, where many different solutions may provide successful outcomes, you can work with those around you, to find the best solution for all.
The only obligation a pilot in command has: is to inform the controller that you are going to deviate. It is not required to supply parameters of the deviation or even of the direction of the deviation.
Well, since the PIC is ultimately responsible for the safe conduct of the flight, I would challenge that statement. When you're doing something that no-one expects you to (remember, most ATC units don't see the weather you see, and there are still places in the world with no radar), then by all means, do tell the rest of us. I agree that communication is secondary to flying the airplane/avoiding mountans/not getting killed, it is still vital.
By asking for permission to deviate you are giving the air traffic controller your command authority. NEVER allow an air traffic controller to take command of your aircraft.
I probably shouldn't let that statement get the best of me, but get of your god damn horse. It's not about that. It's not even close to being about that. It's about making it work for everyone, under the assumption that all hell didn't break loose all of a sudden, with no forewarning. ATC and most others in here know the deal.
So... sorry for the rant. I'll probably be shot down by a lot of you, but hopefully some of you will understand my frustration. Hat, coat, door.