LeadSled (#9) I prefer to use 'requirement' opposed to ‘legal’; requirements can either have a legal or advisory basis.
I agree that the requirement for the minimum landing field length is 60%, applying to both dispatch and inflight. However, whilst dispatch requires the use of AFM data, it is less clear that the AFM data has to be used in flight -
See the conflict between CAT.OP.MPA.300 – Ops Manual, and CAT.POL.A.105(a) – AFM, but CAT.POL.A. 100 does allow ‘approved performance standards that ensure a level of safety equivalent to that of the appropriate chapter’.
Assuming a top–down precedence, then ‘other approved performance data’ could be used for landing (EASA) – I cannot find an equivalent for the FAA or Australia.
I cannot identify any relevant changes in certification standards (CS 25 aircraft), and whilst the operational requirements (EU IR OPS) continue to evolve, this is apparently without significant change in the actual requirements. However, the landing data and methods of calculation which can be used to meet the requirement (as approved by the regulator) has undergone significant change, e.g. introduction of contaminated data and thence to OLD/FOLD. These can be, or are considered as ‘other approved performance data’; hence the widesperad use of Airbus FOLD.
Whilst there is an agreement to harmonise FAR 25 and CS 25 (aircraft) this does not mean that EASA is following FAA; some differences exist, e.g. CS 25 already has requirements for contaminated data, FAA has not.
For operational requirements, FAA part 121 vs EU IR Ops, there are significant differences, generally where the FAA is lagging due to a backlog of ‘law making’, thus the use of ACs.
I agree that OLD/FOLD should give a longer required distance than the AFM due to the method of calculation.
In Europe it appears that FOLD is generally accepted as ‘approved performance data’; the FAA also appears to be following this; see AC 25-32 “11.3 Contaminated runway landing performance data approved by either the Joint Aviation Authorities or EASA in compliance with either their contaminated runway type certification or operating requirements are acceptable when using the optional process identified in this AC, …”