2 OverviewWhy do airports measure friction ?CFME or Decelerometer – Why are they different and which is more accurate?Summer Testing – ProcedureWinter Testing – ProcedureWhich CFME is Right for your Airport ?
3 Why do we measure Friction ? Over time, the skid-resistance of runway pavement deteriorates due to a number of factors: The effect of these two factors are directly dependent upon the volume and type of aircraft traffic.mechanical wear and polishing action from aircraft tires rolling or braking on the runway surfacethe accumulation of contaminants
4 Why do we measure Friction ? Runway Contaminants, such as, rubber deposits, dust particles, jet fuel, oil spillage, water, snow, ice, and slush, all cause friction loss on runway pavement surfaces. The most persistent contaminant problem is rubber deposit from tires of landing jet aircraft. Rubber deposits occur at the runway touchdown areas and is extensive to remove. NOTE: Friction testing is required before and after rubber removal. Heavy rubber deposits can completely cover the pavement surface texture causing loss of aircraft braking capability and directional control, particularly when runways are wet.
5 Why do we measure Friction ? DC-9 Aircraft Wet Runway Landing Veer-off Accident Reynosa, Mexico; October 6, 2000
6 Why do we measure Friction ? Chicago Midway AirportRunway friction was a contributing factor
7 Why do we measure Friction ? Initial Reported Comments – Chicago Midway AirportNTSB preliminary reports that the runway was last cleared of snow and chemically de-iced approx. 45 minutes prior to Southwest aircraft landing.Airport officials reported the braking friction on the runway was “good” 30 minutes before the accident, but investigators have determined the runway condition at the time of the accident to be only “fair” to “poor”.
8 Why do we measure Friction ? July / August 2005 two aircraft over ran the Runway, one at Toronto and one at Bangladesh.The Air France A-340 was destroyed in the post accident fire. Both accidents involved landings in heavy rain and crosswinds conditions.According to Accident Records: During the last 15 years, there have been 130 accidents involving aircraft overruns and runway veer-offs, of which 3 resulting in complete loss of aircraft and 80 fatalities.
9 Why do we measure Friction ? During a heavy downpour, the conditions on the length of a runway can vary and may be deep enough to cause hydroplaning.A layer of water between the tires and the runway surface reduces the friction level to NIL braking action.When a runway is contaminated with water the information passed to the pilot is reported as “wet”.No water depth or location is reported.
10 Why do we measure Friction ? Typical Information given to the Pilot
11 Is a CFME the same as a Decelerometer? Continuous Friction Measuring Equipment is the continuous trace of friction along the length of the runwayAirport Surface Friction TesterMu MeterRunway Friction TesterGriptesterNAC Dynamic Friction TesterRUNAR Runway Analyser and RecorderBV-11Sarsys Friction TesterThe “Mu Value” is calculated by the horizontal force divided by the vertical force or by using the measured torque generated at the measuring tire.Info : FAA AC150/ C
12 Is a CFME the same as a Decelerometer? Continuous Friction Measuring Equipment (CFME)All approved CFME’s have different operating modes including different tires, tire inflation pressures, slip ratio, weights.Each CFME will record different friction values at different speeds as note in AC150/ C, Table 3-2.Info : FAA AC150/ C, Table 3-2
13 Is a CFME the same as a Decelerometers ? A Decelerometer only gives a spot check of the pavementBOWMONKTAPLEYTES ERD MK3VERICOM VC3000 RFMThe operation of a Decelerometer is to measure the forces generated in terms of g (deceleration ft/sec2)“under full skid conditions”.Decelerometers can be either Electronic or MechanicalInfo : FAA AC150/ A Appendix 4
14 Info : Road Research Laboratory Report 50 Is a CFME the same as a Decelerometer?Slip Wheel CFME 0.57µLocked Wheel Decelerometer 0.35µEffect of slip ratio on coefficient of braking friction on wet runwayInfo : Road Research Laboratory Report 50
15 Is a CFME the same as a Decelerometer? Both Mu Value and Braking Action reporting is acceptable for reporting pavement conditions.To date there is no correlation between CFME and a Decelerometer FACTA CFME is a precision measurement device and is more accurate and reliable than a Decelerometer because of several uncontrollable variables influencing the reporting (braking technique, vehicle condition, etc.) .Info : FAA CERTALERT No
16 SUMMER TESTINGAC150/ CMeasurement, Construction and Maintenance of Skid-Resistant Airport Pavement Surfaces
17 Summer TestingFriction Evaluations with CFME’s are required by the FAAWater is pumped directly in front of the friction measuring wheel(s) at a controlled rate.This gives standard repeatable conditionsThis is an ideal test for monitoring rubber build up and the runways micro and macro textureNot an ideal test for monitoring ponding or in conditions such as Snow, Slush or Ice.Summer Testing can only be performed using a CFMEInfo : FAA 150/ C
18 Summer Testing40mph Testing determines the overall Macrotexture / Contaminant / Drainage condition of the Pavement Surface.60mph Testing determines the overall Micro-texture of the Pavement SurfaceTests give a good indication of the runway drainage ability during rain conditions providing greater information for winter OPS.
19 TABLE 3-1 MINIMUM FRICTION SURVEY FREQUENCY Summer TestingTABLE 3-1 MINIMUM FRICTION SURVEY FREQUENCYInfo : FAA 150/ C Page 19
20 Friction / Distance 2D Charting Summer TestingFriction / Distance 2D ChartingRunway divided in to 300 foot sections and color coded for quick reference
21 Winter TestingAC150/5200/30AAirport Winter Safety and Operations
22 Winter TestingCFME are to be performed down the full length of the runway at a Safe Speed depending on runway conditions.Decelerometer, a minimum of Three(3) Braking tests in each zone are required in determining the average friction value for that zone. A total of 9 braking tests are performed.Friction surveys will be reliable as long as the depth of dry snow does not exceed 1 inch (25mm), or the depth of wet snow/slush does not exceed 1/8” (3mm) Info : FAA 150/ Page 11
23 Winter Testing Friction Surveys are to be performed when: The central portion is contaminated over a distance of 500 feet (150m) or more.Whenever visual runway inspections or pilot reports changing friction characteristics.Following anti-icing, de-icing, or sanding operationsAt least once(1) during eight(8) hour shift while contaminants are present.Immediately following any aircraft incident or accident on the runway.Info : FAA 150/ A, Page 11
24 Winter Testing Friction Measuring Procedures (C.C.C.L.S): Calibration: In accordance with the operating manualCoordination: Work closely with ATC/FSSClearance: contact ATC/FSSLocation: 10 feet from centerline, in direction of aircraft landingSpeed: Up to 40mph, as safety considerations allowInfo : FAA 150/ A, Page 12
25 Ref  : FAA CERTALERT No. 05-01 Winter TestingExample Reporting for FSS & ATCCFME:Friction Report using “DFT RWY 03R, , compacted snow at 0325hrs.Decelerometer:Friction Report using “BOWMONK RWY 03R, , compacted snow at 0325hrs.Caution :There is no correlation between a CFME and a Decelerometer Ref  : FAA CERTALERT NoInfo : FAA 150/ A Page 12