Gysbreght, the issue of glideslope vs descent is a grey area.
Based on my (dated) experience, the EU OPS (previously JAR OPS) requirements stem from the certification requirements for steep approach; the results of which, as you state, are published in the AFM. However, in the absence of a specific certification regulation (previously a STOL / FWG working paper), the certification basis appears to be the operational requirements – a circular reference.
Here, glideslope has been interpreted as requiring precision guidance for a straight-in landing – electronic or visual (PAPI).
A descent without precision guidance has been referred to as a vertical path, see CS25 AMC No. 1 to CS 25.1329 Flight Guidance System, Appx 1, 4.2.3.3 Assessment – Approach without Vertical Path Reference
Note that the FGS requirement – use of AP, requires special approval above 4.5 deg.
I would not be surprised to see other references creep out of the woodwork of certification.
Therefore there appears that there is no specific limitation on an aircraft’s descent path i.e. = max rate of descent; cf descents prior to capturing an ILS GS.
Thus I see the issue in Bomba’s question as how far the descent analogy can be extrapolated for an approach to an airfield, but not necessarily a runway for a straight-in landing. My previous post attempted to distinguish between these.
Again there can be grey areas; Sion (LSGS) 6 deg ‘precision’ descent to 3.5 GS, and Lugano (LSGA) 6.65 deg descent for a visual (PAPI) straight-in landing; but I fear that my experiences are out of date.
P. S. Canadian background
https://www.tc.gc.ca/eng/civilaviati...25-011-314.htm
And from EASA NPA 2011-09, but where this has ended up, who knows???
"Steep approach and landing Flight test and structure item
The scope of CS-25 does not cover steep approach and landing capability and consequently additional airworthiness requirements are required with provisions to enable an aeroplane to use an approach path angle greater than or equal to 4.5° (a gradient of 7.9 %). Certification Review Items have raised an appendix containing these additional requirements which have evolved over the years and the most recent standard is proposed here. The requirements of this appendix cover only CS-25 Subparts B and G and they apply in lieu of CS 25.121(d). … It is therefore proposed to create a new Appendix Q in Book 1 and an AMC to Appendix Q in Book 2."
P P S ‘Q’ found it. Page 281 – note definitions ‘an approach to land’; nothing for the airfield.
http://easa.europa.eu/system/files/d...2014-026-R.pdf