Question about the Semicircular Rule
 

So, I'm in the process of revising for my Air Law exam this weekend and I'm a little puzzled about the Semicircular Rule (IFR Rule 34).

I understand the basic principle that above FL245, the cruising level is determined by the aircraft's magnetic track. Simple.

What I don't understand is the levels which are stipulated for tracks 000-179 degrees: FL250, 270, 290, 330 (wait, what about 310?), 370 (no 350 either?)

And for tracks 180-359 degrees: FL260, 280, 310 (not 300?), 350, 390.

Although it'll probably never be of any concern to me in a PA-28, I'd just to satisfy my curiosity!

Rich

What I don't understand is the levels which are stipulated for tracks 000-179 degrees: FL250, 270, 290, 330 (wait, what about 310?), 370 (no 350 either?)


Depends whether you are flying eastbound or west

have a look at this

Flight level - Wikipedia, the free encyclopedia

Level separation goes to 2,000 feet above 290 hence the gap then "missing" levels you mention. I guess it was to allow for altimeter errors in older aircraft. All old theory now as much of the world has RVSM airspace now (1,000 foot separation all the way up).

There certainly isn't any VFR traffic at in between levels at those altitudes!

Rich

All of the above, including the data you've been given (presumably from a very dated textbook) and your stated understanding of the basic principle, is complete tosh!

Fright Level's explanation would have been correct ten years ago, but that was before the introduction of RVSM between FL290 and FL410.

I would suggest that you should actually read Rule 34 of The Rules of the Air Regulations if you want to understand the quandrantal and semicircular rules. You can find it in Section 2 of CAP393, which can be downloaded from the CAA site under Search Publications.

Rule 34 is, as far as I can see, completely redundant today. All airspace in the UK above FL245 is controlled.

Fright Level's explanation would have been correct ten years ago, but that was before the introduction of RVSM between FL290 and FL410

Yep, which is why I said "All old theory now as much of the world has xMNPSx RVSM airspace".

Edited to change MNPS to RVSM (got my acronyms mixed up :\ )