JT, “
.. the better risk management approach is to use the 1.67 factor as a risk mitigator for the higher touchdown speed.”
Agreed in principle, but the landing distance safety factor (concept) is only intended to provide some buffer for every-day normal variability in landings and may not be sufficient if one or more variables are in error in addition to a wind additive approach speed (
Large Transport Aeroplanes - Landing Performance).
In addition, strong winds / gusts are often associated with wet runways; and although the ‘wet’ landing distance factors are higher, the actual safety margin may not be as good as on a dry runway. In rare conditions there may be no margin at all, thus the landing techniques, accuracy, and use of retarding devices requires careful thought and briefing. Crosswinds should also be considered as they can affect landing distance required, particularly in conjunction with fast approach/touchdown speeds.
Centaurus “but Boeing tend to be vague in such areas” (#7).
Yes; not only vague but they have got their ‘unmentionables’ in a twist. On one hand they support industry standards for stabilised approaches, yet suggest a late deceleration; elsewhere their recommended max approach speed is above the industry accepted maximum of ref+15 and there is little guidance on the subsequent landing techniques and distance. Their problem appears to be a need to encourage safety, yet protect their landing performance. Perhaps different parts of the organisation?
The result is similar to other advice on approach speed / landing performance – manufacturers and regulators; in that operators have to be aware of the extensive range of issues, the limitations of information, and the assumptions made about these operations, and thus safety depends extensively on the crew decisions and actions during approach and landing; it is not assured by safety margins.