PANS-OPS Vol I Part I Section 2 Chapter 1 Para 1.4:
1.4 USE OF FLIGHT MANAGEMENT SYSTEM (FMS)/
AREA NAVIGATION (RNAV) EQUIPMENT
1.4.1 Where FMS/RNAV equipment is available, it may be used to fly conventional procedures provided:
a) the procedure is monitored using the basic display normally associated with that procedure; and
b) the tolerances for flight using raw data on the basic display are complied with.
1.4.2 Lead radials
Lead radials are for use by non-RNAV-equipped aircraft and are not intended to restrict the use of turn anticipation by
the FMS.