As has been pointed
out the practice of issuing descent clearances followed by an 'expected' lower level is very much frowned upon due to the potential for level busts.
If NATS were to study the paper mentioned by MONT BLANC properly again, it will find the issue of level busts from 'expect' clearances was fully covered and investigated. A great deal of effort was done with SD into level bust occurances - the result concluding that 'expect' clearances were NOT directly contributable to level busts.
What was VERY apparant during the period of that papers production was that LATCC Ops (as was in those days....) did not want the extra workload of publishing, in any form other than MATS pt2, such restrictions.
The report was finally accepted however, and NATS agreed to publish, but with a delay of over approx 1 yr due to workload issues. ScOACC were VERY helpfull throughout the consultation, and fully supported it's findings. Their restrictions were published without delay - and incorporated into STARS where applicable.
I still believe the restrictions should be published - there ARE big aircrew issues here, mainly in the planning and management areas of the descent and approach. UK airspace is unique in the hugely early descnts for some airfields.
LTMA and MTMA airfields aren't too badly off descent wise, and so one isn't badly caught out.
Descents to 'regional' airfields such as NM as BOAC mentions CAN create unnecessary issues for the flight deck. Midlands Group airfields are also another classic. Descent is SO far ahead of what is ideal/economic, one CAN be badly caught out.
Now, don't get me wrong, I am not bemoaning the system for this. The UK has a tremendous ATC system, held together mainly by it's frontline, operational staff (controllers). The SA's are there for good reason, and provide a system capacity benefit that ALL operators benefit from.
BOAC does have a perfectly valid point however, and I know exactly where he is coming from.......
I suggest NATS pull out that working paper from what is several years back now and give it a bloody good read!
30W (pilot)