alf5071h
Thanks for the input. May look a bit confusing to start with, but sorting out your input I think we can handle it.
First we have to distinguish between description of braking action and description of surface conditions
Braking action
Normal
Good
Medium/Fair
Poor
Unreliable
Surface conditions
Dry
(Damp - no longer in use according to latest harmonisation -
http://www.easa.eu.int/home/easa NPA 14/2004, CRD 14/2004)
Wet
Slush
Wet snow
etc.
+ combinations of these
Surface conditions (for reporting purposes) is a topic of its own, and I will stop here for not loosing track of the braking action terms with assosiated definitions.
You make reference to the 1995 evaluation -
http://ntl.bts.gov/lib/1000/1100/1106/wrfmrwg1.pdf . I know this document and there are several statements in this document which are not stricktly correct. When you start to combine the definitions with measured friction coefficients you start to get into trouble. The first mistake is that one mix operational measurements (snow and ice) and measurements for maintenance purposes (wetted surface). And once you start talking about friction measurements you have to distinguish between different friction measurement devices. So let us address these things under an other heading and concentrate on the braking action terms. Otherwise your quote from the document are in line with earlier mentioned definitions for braking action.
With respect to the James Brake Index. Today it is named Canadian Runway Friction Index. Info found at
http://www.tc.gc.ca/CivilAviation/co.../CRFI/menu.htm The CRFI has been updated to current knowledge through the Joint Winter Runway Friction Measurement Program (JWRFMP).
The term Excellent would have to be compared to normal, and we have (with assosiated descriptive terms):
Normal/Excellent - Maximum energy stops possible with little deterioration in certified (dry) stopping distance.
Good - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted (wet), some distance in excess of certified stopping
distance would be expected.
Medium/Fair - Sufficient braking and cornering force is available for a well-flown approach and landing using light braking. However, excess speed or long touchdown would result in an extremely low safety factor depending on runway length and crosswind component. Careful planning and good judgment are required.
Poor - Very careful planning, judgment, and execution are absolutely essential. Crosswind becomes a "priority one" consideration. While a safe and successful approach, landing, and stop can be accomplished if all factors are favorable, there is little room for error. Care must be exercised in every aspect of the operation and a very careful evaluation of all conditions is necessary.
Unreliable - "Unreliable" will be reported when surface conditions do not permit a meaningful action value to be determined (i.e., standing water, slush, wet snow [potential hydroplaning]).
We have also sorted out following items to be treated seperatly:
1. Surface conditions (for reporting purposes)
2. Type of friction measurements - operational vs. maintenance
3. Harmonisation of friction measurement devices.