haroon - my understanding (based on UK ops under EUOPS) is that for 'normal' landings, crews must apply the same 15% factor to any 'unfactored' manufacturer (eg QRP/PIFS figures). The only time this is not needed is in an emergency or 'non-normal'.
Two items to view
the CAA information document :
http://www.caa.co.uk/docs/1428/20120...tedRunways.pdf
and a recent thread here on the topic
http://www.pprune.org/tech-log/47135...ent-exist.html