td,
No credit for T/R
That's correct for certificated performance as in the AFM, which already includes a ‘dry’ factor. The AFM data and further factoring (wet) is predominantly used for dispatch; whereas ‘actual’ - unfactored performance is in the FCOM for crew use, and more often includes credit for T/R.
The impression I have is that operators who use ‘actual data’ tend to include T/R as standard and then consider the minimum FAA factor of +15% on top. Like most landing data this is satisfactory if the runway condition is as reported, but if the braking action is less than planned, then (factored) actual data may run out of runway earlier than other factored data. Do 737 operations predominantly use ‘actual’ data?
A 2.4 factor was published in a Canadian report re landing on snow and ice, grooved / ungrooved runways, assessing equivalent safety with dry operations (IIRC they used a 737), i.e. using anything less than 2.4 on ice and snow has a higher risk than normal.
FAA and EASA are harmonised for AFM data, except EASA has additional requirements for contaminated operations. For operating data, EASA has moved rapidly towards Factored Operational Landing Distance lead by manufacturers (is 737 data available yet - all versions ?). FOLD is much more realistic than ‘actual’, but may be less than AFM factored data, although some views argue that there is a good correlation between FOLD and AFM for a wide range of operating conditions - is more tolerant of miss reporting braking action.
P.S.
Aviation Investigation Report A10A0032 - Transportation Safety Board of Canada
(727), para 1.9 discusses additional factors (up to 2.4) in very wet conditions, with/without T/R.
TC Reference. History of the Joint Winter Runway Friction Measurement Program. TP 13579
From
Joint Winter Runway Friction Measurement Program - Transport Canada
FAA position re improved data
https://www.aci-na.org/sites/default...fng_8-4-16.pdf still only advisory, whereas EASA mandates it.