Introduction8212;Mu numbers (friction values) measured by CFME can be used as guidelines for evaluating the surface friction deterioration of runway pavements and for identifying appropriate corrective actions required for safe aircraft operations. The original levels were based on the work of the FAA/AS-90-1 (3). The report states that based on friction values from a Mu Meter Mark II using Dunlop tires, and tests conducted by NASA in the 1970s using a Boeing 727, Table 1 of Mu Meter friction level classifications for runway pavement surfaces was established for friction measurements at test speeds of 65 Km/hr. Additionally, tests were conducted again with the Mu Meter Mark II outfitted with the Dico tire at 95 Km/h. Then a second order correlation was performed for the Mu Meter operating at 95 Km/h and at 65 Km/h resulting in the values shown in Table 2. These values were then fixed and used with correlations of other CFMEs to establish the present maintenance levels given in Table 3.2 of FAA Advisory Circular AC/150/5320-12. From the Wallops 1993 data, the IFI values were calculated and the 65 Km/hr data in Table 2 was used to calculate the FM60 value for each level. The data for the two speeds for the four CFMEs in the FAA report (3) were used to establish the SMp values for each level. Then a new level, New Grooved, was added based on the differences of grooved and un-grooved sites at the NASA Wallops test facility. Table 3 is a list of these values to be the standard values FM60 and SMp for any future calibration of CFME.
Airports8212;Routine testing is carried out in order to obtain data for scheduling remedial work on the runway surface. A single run on either side of the centerline may be regarded as sufficient or a set of runs covering the whole width of the runway may be preferred. At 3m spacing, the friction map which can be prepared from a set of runs of this kind provides excellent information on rubber buildup and surface polishing. Standard test speeds are typically 65 km/hr or 95 km/hr and standard test water film thickness is typically 1 mm.
TABLE 1 Original Mu Meter Friction Classifications of Runway Pavement Surfaces for 65 km/hr Test Speed
| Mu Value | Classification |
| 40 | Minimum |
| 50 | Maintenance Planning |
| 70 | New Design/Construction |
TABLE 2 Mu Meter Friction Classifications with a Dico Tire of Runway Pavement Surfaces for 65 km/hr and 95 km/hr Test Speed
| Mu Value | ||
| 65 km/hr | 95 km/hr | Classification |
| 42 | 26 | Minimum |
| 52 | 38 | Maintenance Planning |
| 72 | 66 | New Design/Construction |
TABLE 3 Recommended Friction Classification Levels from the Mu Meter for 65 km/hr