Unfactored or Certified Landing Distance. The landing distance determined during certification as required by 14 CFR part 23, § 23.75 and part 25, § 25.125. The unfactored landing distance is not adjusted for any safety margin additives. The unfactored certified landing distance may be different from the actual landing distance because not all factors affecting landing distance are required to be accounted for by certification regulations. For example, the unfactored certified landing distances are based on a dry, level (zero slope) runway at standard day temperatures, and do not normally take into account the use of auto brakes, auto-land systems, head-up guidance systems, or thrust reversers. This is considered the baseline landing distance from which all subsequent user calculations emanate.