(1) Unless otherwise authorised by the responsible ATSU, aircraft flown in compliance with the rules contained in this Division, shall comply with IFR procedures applicable in the relevant airspace.
(2) Unless otherwise authorised by the appropriate ATS authority, or directed by the appropriate air traffic control unit, controlled flights shall, insofar as practicable—
(a) when on an established ATS route, operate along the defined centre line of that route; or
(b) when on any other route, operate directly between the navigation facilities and/or points defining that route.
(3) An aircraft operating along an ATS route segment defined by reference to VHF omnidirectional radio ranges shall change over for its primary navigation guidance from the facility behind the aircraft to that ahead of it at, or as close as operationally feasible to, the changeover point, where established.
(4) Subject to the provisions of regulation 91.06.25, the PIC of an aircraft may execute, or endeavour to execute, a cloud-break or let-down procedure at an aerodrome or nominate an aerodrome as an alternate aerodrome: Provided that the requirements relating to cloud-break or let-down procedures and to flights under IMC, as published by the Director in the IAIP, can be complied with.