I will now link the definitions for Good - Medium - ... with info from Boeing.
At the 2003 Boeing Performance and Flight Operations Engineer Confereence, Boeing presented:
Airplane Braking Coefficient - Pilot Reported Braking Action - Runway Description
0.4 - Approximates dry runway - Friction limited certification values
0.2 - Good - Wet Runway, Jar certification for compact snow
0.1 - Medium/Fair - Ice, Compacted Snow
0.05 - Poor/Nil - Wet Ice, Slush, Melting Compacted Snow, Standing Water
On a runway covered with wet ice, slush, melting compacted snow, or standing water the possibility of hydroplaning exists, which can result in nil braking capability. For that reason we recommend that the flight crew use the operational landing distance for POOR Braking Action in such conditions to determine the acceptability of landing on such a runway.
If we combine this with the definitions from ATA we get:
NORMAL/EXCELLENT - Friction limited certification values. Maximum energy stops possible with little deterioration in certified stopping distance.
Runway Description - Dry runway
Aircraft Braking Coefficient 0.4
GOOD - More braking is available than will be used in an average airline type deceleration. If a maximum energy stop were attempted, some distance in excess of certified stopping distance would be expected.
Runway Description - Wet runway. CS (JAR) certification for compact snow.
Aircraft Braking Coefficient 0.2
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.
Runway Description - Ice, Compacted Snow
Aircraft Braking Coefficient 0.1
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 facet of the operation and a very careful evaluation of all existing conditions is necessary. Possibility of hydroplaning/aquaplaning exists.
Runway Description - Wet Ice, Melting Compacted Snow, Slush, Standing Water
Aircraft Braking Coefficient 0.05
NIL - Extremely slippery with poor directional control even while taxiing.
Runway Description - Freezing rain condition if nothing were done to the runways or taxiways.
Aircraft Braking Coefficient 0.05
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Please give comments/feedback on the "suitabilty" of the above terms and relationships in an operational pilot's world.
(I will later bring in other documented relationships.)