hawk37, sorry for the late answer mate, I have done some research for official info and found some of it. ATC unit can refuse the entrance of the A/C despite the submitted FP/RPL, in exceptionally circumstances, if we are talking about experienced countries e.g. Israeli airspace has been closed immediately after 9/11 attacks and all the inbound traffic rerouted. One of the flights from my previous company was on the way to Ben Gurion and has been refused the entrance clearance, diverted to Larnaca refueled and came all the way back. However under normal operational conditions that one shouldn't happen, as the coordination process among the ATC units is done upon submission of the flight plan and supposed to be also acknowledged and accepted or rejected by such. Its a subject to the agreement between the ATC units (different countries) whether its simple receipting of AFTN message or sending active confirmation is sufficient, as i have read in DOC 4444. Consequently, the rejecting ATC should have submitted the negative message upon receipting of the FP details, in my opinion. Well, all in all, if you have been refused the entrance, the only thing you can do is turn back or reroute if possible, unless its an emergency and have declared it and you perceive that safest course of action would be to enter the IFR and e.g. to proceed to the decompression escape alternate (as an example).
Those are the excerptions i have found in the ICAO DOCs:
3.6.2 Adherence to flight plan3.6.2.2.1
3.6.2.3 Intended changes. Requests for flight plan changes shall include information as indicated hereunder:
a) Change of cruising level: aircraft identification; requested
new cruising level and cruising speed at this level, revised
time estimates (when applicable) at subsequent flight
information region boundaries.
b) Change of route:
1) Destination unchanged: aircraft identification; flight rules; description of new route of flight including related flight plan data beginning with the position from which requested change of route is to commence;revised time estimates; any other pertinent information.
15.6.1 Emergency separation
15.6.1.1 If, during an emergency situation, it is not
possible to ensure that the applicable horizontal separation can
be maintained, emergency separation of half the applicable
vertical separation minimum may be used, i.e. 150 m (500 ft)
between aircraft in airspace where a vertical separation
minimum of 300 m (1 000 ft) is applied, and 300 m (1 000 ft)
between aircraft in airspace where a 600 m (2 000 ft) vertical
separation minimum is applied.
15.6.1.2 When emergency separation is applied the flight
crews concerned shall be advised that emergency separation is
being applied and informed of the actual minimum used.
Additionally, all flight crews concerned shall be provided with
essential traffic information.
I don't think its necessary to make use of that procedure in case of simple course reversal, but could give you an idea though. In case of course reversal just prior to FIR, i would just turn 90 DEG staying within 10 nm from the airway centerline and in coordination with ATC descent to the appropriate reversal level turning on the back course, or if intended request specific en route holding instructions until further advice. Well, that's what I have found out, would appreciate any additional or corrective information.
Cheers.
Last edited by popay; 25th Jan 2006 at 13:32.