Speedwinner, the discussion depends on how the LDR is defined.
The AFM usually contains the un-factored certificated landing performance: – 50ft, Vref, etc, etc.
Landing distance required (LDR) for dispatch is usually defined by operational requirements and includes a factored increment based on the AFM. This data is the distance from the threshold (assumed to be 50ft) until the aircraft stops, plus the required safety margin, e.g. 1.67.
Most manufactures publish un-factored ‘actual’ landing distance; some operators may use their own data. This distance may (more often does) depend on reverse thrust, which the AFM / dispatch do not, and may cover a range of runway braking conditions, which again may not be the same as for dispatch. These data are ‘pared to the bone’ in making several unrealistic assumptions, e.g. 1000ft touchdown.
Although this performance can be used for pre-landing calculations according to local operational regulations, it is now generally accepted that like the un-factored AFM data, the distances cannot be achieved in everyday operation.
The FAA recommends a minimum addition of 15%, which even then might just be a better ‘actual’ if everything works; this may be the operator’s LDR.
EASA (EU-OPS 1) requires a check to ensure a safe landing, which many operators interpret as a fully factored margin equivalent to dispatch and only reduce that in emergency conditions.
Currently the industry is trying to standardise the inflight-use data to provide a more realistic 'actual' distance – Operational Landing Distance, OLD. This makes more realistic assumptions about touchdown speed and distance amongst other apsects.
Airbus have started to use OLD, and often with the minimum addition of 15% publish Factored OLD, FOLD.
Thus which distance are you considering in your debate?
Perhaps your debate is more about not knowing what the LDA is based on?