decimal86
Good question, been covered before, but always brings up a variety of answers. Here is MY take on it.
Depends on what yo mean by a "normal" clearance. If you mean simply "descend FL280" this is an instruction to leave now but with no other restriction. If you mean "descend FL280 be level at XYZ" it is less clear. My opinion, and i stress it is
my opinion is that top of descent is pilots discretion, descent profile is at pilots discretion also, as long as you meet the restriction I dont care how you do it. I give such a clearance when there is no other traffic to effect your descent.
But........
Many controllers disagree with me on this point. They believe, and could probably quote you section of an official ICAO document to back themselves up, that descend means descend and do it now because now is when I am issuing the clearance. They will say that the minimum rate of descent allowed by ICAO without notice from the pilot is 500fpm, and if that is enough for the traffic then they are covered.
Thats fine, and it is a personal choice, and I'm sure when they explain it to the incident investigators they will be proved right.
If there is traffic to effect your descent profile I will give you some form of control to keep you clear of it, be it a rate of descent, a heading or a speed restriction, indeed I normally clarify a clearance with no descent restriction with "descend when ready...." or "pilots discretion descend.....".
But the old favourite of this discussion is this.
If in doubt......ask . It is potentially a safety issue so surely if you are unsure of what is meant by a clearance it is best to clarify.
Hope this answers your query, and I look forward to restricting you the next time you fly through.
