Originally Posted by backofthedrag
Is there any way of relating CRFI to ICAO friction index ?
I doubt that there is a scientifically reliable method due to the many variables – notable that
“there is not, at present, a common friction index for all ground friction measuring devices. Hence it is not practicable at the present time to determine aeroplane performance on the basis of an internationally accepted friction index measured by ground friction devices.” (JAA EASA NPA 14/2004).
There is a plot of ‘braking mu’ vs CRFI for the Falcon aircraft in Fig B-2 in
Benefit-Cost Analysis of Procedures for Accounting for Runway Friction on Landing (3.6mb) Appendix B. However, without knowing what the relationship between braking mu and measured mu is, then there would only be tenuous links with the ICAO index. Table B-2 appears to indicate a 2:1 relationship, which I believe is used by some operators, but the extent of the variability and possible error, is shown in Fig 3-1 where on a wet runway there can be a range of 1-3 CRFI units depending on how wet the runway is and the construction materials used – beware wet concrete.
Also see
Managing Threats and Errors During Approach and Landing PPT 2.7M where slide 27 attempts to pull some of the variables together in a practical way.