So according to the Jeppesen Airway Manual the approach can be executed if SPL VOR is unserviceable, but would you really execute this approach when the VOR is U/S under heavy IMC conditions?
VOR is a special case. Due to its historical role, all IFR aircraft is
assumed to have at least one VOR receiver, or an acceptable substitute (e.g., a VOR fix on RNAV). Therefore a VOR requirement will
not be listed in the notes, even if it is required (outside of the final approach segment; if the VOR is a primary instrument required for the final approach segment, then VOR will be included as part of the approach title).
So the equipment required to execute the approach is listed by: 1) the approach title/procedure name; plus 2) notes on the chart; plus 3) any VORs required to execute the approach.
Notes on the Plan View denote equipment required for
procedure entry. Notes on the briefing strip denote equipment required
to complete the approach.
For documentation see
FAA Order 8260.19F (Flight Procedures and Airspaces) paragraph 8-6-6(h) and
AIM Chapter 4 (Approaches -- Equipment Requirements).
Technically, the title of the procedure is for identification purposes, not to list the required equipment. However, the first part of the title is the primary navaid
providing lateral guidance for the final approach segment. This is documented in
FAA Order 8260.3B TERPS Section 6.
Examples (using DME):
1. Title includes DME (e.g., ILS/DME) -- then DME is required to fly the final approach segment
2. Title doesn't include DME, but "DME Required" is noted in the plan view -- this means DME is required for
entry into this procedure, though not necessarily used during the final approach
3. Neither the title nor the Plan View include DME, but "DME Required" is noted in the briefing strip -- this means DME is required elsewhere in the approach (e.g., during the missed approach segment)
4. In all cases, VOR may be required as well