Hi 10W,
I would agree in part about the FMC, but:
a) This has not cropped up before when controlling FMC aircraft........even with various headings (occassionally in TC we have to use some very creative headings
)aircraft still make the standing agreement level, or get very close to it.
b) I asked the pilot initially if he had been cleared to FL220 level by HEMEL, and rather than mention that he missed it because of the FMC he started talking about me cancelling the previous clearance, which leads me to believe that the FMC was not the prime factor in them missing the restriction.
The problem is we would all expect the pilot to comply with the vertical element of the previous clearance when using a heading, but the point is I have practical experience of this not happening, and the pilots thought that what they were doing was absolutely OK.
I really think it is time the AIP and MATS Part 1 were updated with relation to clearances to take into account places such as LATCC where it is imperative aircraft make standing agreement levels.
Expedite