Thanks
alf5071h The link was new to me, but did not help me to get any closer. (But I found other interesting material presented)
I have found some old reports with B-727, DBV and Mu-Meter data from 1971 and DC-9, DBV and Mu-Meter data from 1972. This are preliminary reports from the
Joint FAA-USAF-NASA Runway Research Program From the 1972 report:
Background - .........In 1968, a number of friction measuring vehicles were tested at NASA Wallops Station, Virginia, to ascertain the suitability of the various vehicles for measuring friction in a repetable manner and for providing an index that might be correlated with aircraft stopping performance and/or used to produce information which could be used as an operational guide to pilots during inclement weather conditions. As a result of these and subsequent tests, two ground vehicle measuring methods emerged, each showing promise of correlating with aircraft stopping performance and each showing capability of becoming the basis for an operational technique. The two methods are the NASA diagonal-braked vehicle (DBV) and the British Mu-Meter. Although testing to date has produced data which indicate reasonable correlation may exist between these vehicles and some aircraft, sufficient experimental data has not been obtained to show that such correlation would apply over the range of operational aircraft types and slipperiness conditions likely to be encountered in scheduled air carrier operations.
In order to establish further degree of stopping distance correlation that might be obtained between modern jet transports and ground friction measurement vehicles over a wide range of slipperiness conditions, the FAA, USAF, and NASA are conducting a "Joint FAA-USAF-NASA Runway Research Program"
From the discussion in the report we find that there was a correlation between two DBV vehicles (FAA and NASA) of aproximately +-10%
Further:
The British prefer to show the correlation of aircraft stopping distance with Mu-Meter friction reading under normalized aircraft stopping energy conditions. ..........Boundary lines have been faired through the data obtained under aircraft maximum braking (no reverse thrust) conditions. At a Mu-Meter friction reading of 0.5, the data scatter about a mean point between the boundary lines is approximately +-15%
I do think that I am getting closer to the "source" of the 1.15 factor.
Anybody who can support me on this?