Quadrantal Rule Help
I'll probably make myself sound very dumb but what the hell....
when does one fly using quadrantal flight levels as opposed to "any old altitude" on qnh?
Is it simply when one is flying IFR?
If so, when does a flight become IFR? Does the commander need to inform the ATCO when filing an airborne flightplan that they intend to carry the flight out under IFR?
I do hope these questions are understandable.
Thanks in advance