Hi Luftwaffle
In South Africa you can certainly fly under IFR in IMC without a flight plan, as long as one is not required under the legislation governing when flight plans must be filed. We don't have 'flight itineraries' and, if SAR is required, then a flight plan becomes a mandatory legal requirement.
In the UK too, you can fly under IFR, in IMC, without a flight plan. Indeed, to give just one quote from the UK AIP: "An aircraft electing to change the conduct of its flight from compliance with the instrument flight rules to compliance with the visual flight rules shall, IF (my bold!) a flight plan was submitted....."
The UK AIP actually has a section headed "Instrument Flight Rules" which has as point 1 :"IFR flight. ICAO Annex Rules as applied within UK Airspace and incorporating UK differences." It doesn't say it is a definition but this must be the intention. Points 2 et sequitur are the "rules".
So we come back to flight under instrument flight rules being flight following the rules. And these rules will change from one state's airspace to anothers.
I think it just comes down to that if one wants to fly under "instrument flight rules", one first decides what state's airspace one will be in, and then follow their particular rules for coplying with the "instrument flight rules".
What a pity IFR wasn't originally called IF for instrument flight, (just for example.) We would then have no problem, I think, with "Flight under IF, whether in IMC or VMC, must be conducted in accordance with the instrument flight rules as laid down by the state in whose airspace one is conducting the flight".
The apparent circularity of my definition is only because the word "rules" is included in the term IFR when it is being used to determine the rules that have to be followed!!!
A thought provoking thread!
[This message has been edited by GRpr (edited 06 May 2001).]