Boeing aircraft are certified with a demonstrated landing distance. The test flight is accomplished at Vref, touchdown at 1000', max manual braking and no reverse thrust. This is the distance in the AFM.
From the demonstrated landing distance the required FAR Dry Landing Field length is calculated by the following method:
Demonstrated landing distance = .6 x (Available Runway Length). Or rewritten: 1.67 x (Demonstrated landing distance)=available runway.
For example, if the AFM distance for a given weight is 2500', then the required FAR Dry Landing Field Length for dispatch is 2500' x 1.67 = 4175'.
FAR Wet Landing Field Length is the Dry distance increased by 15%, or Dry x 1.15 = FAR Wet Field length
In the above example, the required Wet Landing Field Length would be 4175' x 1.15 = 4801'.
The AFM landing data is the certified landing distance provided by the OEM that is required by FAR Part 25 and 121.
Manufacturers will also provide Advisory Landing distances that include auto brake settings, non-normal configurations and contaminated runway conditions.
The Advisory distances are now factored to account for a longer flare distance and a 15% additive in accordance with the SAFO 06012 and TALPA ARC recommendations.