From another forum:-
The most recent FAA documents (six) on TALPA and avoiding an overrun, @
http://www.skybrary.aero/bookshelf/c...&dateSort=desc
The revised AC150 5200 Airport Field Condition Assessment has two similar TALPA Matrix. One is for Airport Operator Use (page 67), and the other is for Pilot Use (page 68) for relating the runway condition to a braking action.
The first allows use of a ground vehicle to provide an assessment; the second relies on pilot assessment - PIREP.
How can these subjective assessments be equivalent, i.e. provide a consistent report, is
'a noticeable reduction in braking' in an unspecified vehicle the same as 'a noticeable effect' in an aircraft. If not then the ground assessment of braking action could differ significantly from the reality experienced by a crew.
It would appear that the more reliable estimate of braking action is to use the contaminant type and depth.
Is this a valid concern, if not then why not.