And in PANS-OPS, for Precision Approaches it states:
1.4.8.8.3.1.1 Procedures involving glide paths greater than 3.5° or any angle when the nominal rate of descent (Vat for the aircraft type x´ the sine of the glide path angle) exceeds 5 m/sec (1 000 ft/min), are non-standard. They require the following:
a) increase of height loss margin (which may be aircraft type specific);
b) adjustment of the origin of the missed approach surface;
c) adjustment of the slope of the W surface;
d) re-survey of obstacles; and
e) the application of related operational constraints.