Originally Posted by
FullWings
However, I was under the impression that the sort of interpolation/abstraction which might appear sensible on the surface (there is a non-approved app for stopping distance on my current type, I think using the same methods as described above to produce a result) is not deemed appropriate by the authorities as the published data can only be used “as is”
Not sure what the rules that apply to you but here we are currently permitted to use something like
https://appadvice.com/app/gasco-perf...ator/942306086 The Archer 3 POH usefully states: "Effects of conditions not considered on the charts must be evaluated by the pilot, such as the effect of soft or grass runway surface on takeoff and landing performance ...". How else other than by using the UK CAA's Safety Sense leaflet 7?
(Things will change here when the dastardly new Part 91 comes into force and only approved data must be used.)
Originally Posted by
FullWings
.... or with strict linear interpolation when allowed.
I guess that pilots would be expected to use linear interpolation but nothing stopping anyone from using a better fit to the data (but don't do it in an exam as that risks getting the wrong answer in a multi-choice question). Extrapolation is another discussion entirely.