The increase in landing distance using autoland for the 747-400 is due to the AFM statement that when using auto brakes with autoland operations, touchdown should be assumed to occur at 2500 feet from the runway threshold. The 747-400 was certified under 25-7 when the flare distance was 4 seconds, or approximately 1000 feet and the associated advisory landing distances in the FCOM were based on the 1000' touchdown. After TALPA-ARC, the FCOM now includes the 1500' touchdown recommendation. As such, the autoland distances add 1000' or 1500', depending on whether the advisory distances are non-TALPA (unfactored) or TALPA. Western Global was not using the TALPA distances (factored). An amendment to Part 25 around 2011 changed the way AFM air distance is calculated. As such, later Boeing models use a flare time rather than a fixed distance. For the 747-8, the landing distances assume a 7 second flare distance. Thus the heavier the landing weight, the longer the flare distance. Due to this, the AFM doesn't include any additive for autoland distances.