So I've been, again, not flying for a month. But I have been studying a bit for my "Radiotelephony" certificate exam, which I'll be taking in Brussels next week - if the corona situation still allows it.
The exam has an oral an theoretical section. They also provide a list of topics that will be covered.
One of the topics is knowing the Semi-circular system. Read the details in the AIP:
For VFR flights above 3500 ft AMSL the system dictates an altitude or level to fly at depending on your magnetic heading. If you fly a heading 000 to 179 you fly at a specific altitude/level (3500 ft), and if you fly 180 to 359 you fly another (4500 ft).
Note that in Belgium, the transition altitude is 4500 ft, so above that we talk about Flight Levels (FL).
This is useful for safety.
Avoiding Fighter Jets
Every time F-16's fly over my house at low altitude, I wonder how I could possibly avoid them when flying my ULM around.
The AIP has a note that might help with that:
take note that high speed low level military flights, having a flight visibility less than 5 KM, are mandatory conducted under IFR and are therefore maintaining semi-circular IFR cruising altitudes based on the regional QNH.
So if the jets are flying under IFR, they are using the semi-circular system also at low altitudes. This means they'll cruise at 1000 ft or 2000 ft, relative to the regional QNH.
This means it's less likely I'll meet a fighter jet on my path while flying at 1500 ft, regional QNH.
Still, do they have radar? Do they see me on that radar? Can they avoid me? Sure hope so ...