JS, thanks again for the additional info – IFALPA leaflet (#17).
This has the potential to be a valuable guide, but as with most aspects of aviation it is essential to know what assumptions or generalities are being made, and the limits of the referenced data.
The briefing leaflet and your comments on QRH data imply that certificated data is only used pre-flight. In practical terms this may be so, but the leaflet may over exaggerate the value of advisory data ‘en-route’ in normal operation.
Also, the use of revers thrust is overemphasized, see previous posts on reliability. Reverse thrust is a valuable safety feature. However, it is increasingly being used as the norm (must-have in order to stop), but in terms of landing risk (safety) this might not be justified; however it can recover adverse situations (nice-to-have if things go wrong).
Many pilots seek clarity between these alternative views. The regulations require specific margins for dispatch, but there are none for a pre-landing check (a check the FAA still only recommends).
EU OPS-1 is more specific – 'be safe'. This requires judgment, which requires knowledge and skilled application.
The IFALPA leaflet inadvertently encourages a ‘can we land’ attitude, whereas the alternative is ‘should we be landing’; if “yes”, then operators can consider how this can be achieved safely. The latter view requires good situation assessment and appropriate use of data.
Whilst flight test certificated data does not consider temp, slope, (CS 25.125); the presentation of this data in the AFM may show operational factors (CS AMC 25-1518).
The advisory ‘operational’ actual data has many assumptions. The most understated is the 1000ft airborne distance. Boeing quotes this for ‘small’ aircraft, but for larger aircraft this is 1250ft; thus the IFALPA leaflet is not generic. Furthermore, in-service data (research / FDM, FOQA) indicates that these distances are unrepresentative or normal operations (being much longer) and therefore a distance of Boeing 'actual + 15%' is more representative of what an accurate landing (with reverse and all else equal) might achieve.
The examples of spoiler / reverse effectiveness appropriately emphasise human error, but this emphasis overlooks other sources of failure / malfunction – ‘what if’.
The leaflet adds understanding, but the industry requires much more - clarity and simplicity as JT outlines above.