It's damn scary that folk are questioning the requirement for Landing Distance Factors. CAO 20.7.1b refers.
11
11.1
Landing distance required
For subparagraph 5.1 (a), the landing distance for a jet-engined aeroplane is:
(a) for an aeroplane engaged in regular public transport operations when landing on a dry runway, or in charter operations when landing on a dry or wet runway — 1.67 times the distance required to bring the aeroplane to a stop on a dry runway; or
(b) for an aeroplane engaged in regular public transport operations when landing on a wet runway:
(i) 1.92 times the distance required to bring the aeroplane to a stop on a dry runway; or
(ii) the distance set out in the flight manual or operations manual for operations conducted on wet runways.