Non-standard flight levels and coordination
 

Last week, heading east via REDFA with London, I found myself in and out of a lightly icing stratocu layer at FL90. Being unpressurised I didn't want to go to FL110, so I requested, and was offered without comment, FL100 -- which would conventionally be a westbound level.

By contrast, I remember a similar occasion a couple of years ago heading south east via SASKI, asking for FL100 and being told that only FL90 or FL110 were available in that direction.

Does a non-semicircular flight level require special coordination with adjacent ACCs? Always, never, or does it depend on the adjacent FIR?

I have found in recent years that westbound and eastbound levels are more commonly being used for the "other" direction. This may be bad practice, but as long as everybody is aware of the use of these "non standard" directional levels there should not be a problem. Maybe there was already traffic at FL100 making it easier for you to cruise at 90 or climb through to 110?

It was a while ago, but my recollection of the conversation left me with the impression, perhaps incorrect, that it was more to do with approaching the FIR boundary (might have been KONAN rather than SASKI, I forget) than traffic.

:ugh::ugh:That could have been a reason for not giving you clearance for FL100.:rolleyes:some coworkers are really hard to work with!:ugh:

If the necessary co-ordination has been carried out with the relevant agency, particularly if the flight is in regulated airspace, it poses no problem. In certain UK sectors it is not at all unusual to utilise "opposite direction" levels [or ODLs] as a matter of routine. It enables a large amount of traffic to cruise at or fairly close to optimum economy level. During the early part of the morning, for example, most jet levels are used for the eastbound Atlantic rush......about mid-morning there is a switch to using most jet levels [irrespective of directional convention] for the westbound Atlantic rush.
In your specific case a controller will always make the extra effort if you have an icing problem. In other parts of UK airspace the airway base may be so high as to preclude choice of "unpressurised" levels....the use of ODLs allows best and efficient use of airspace to the benefit of all users.