A new tow-behind continuous friction measurement device is available from NAC Dynamics, LLC, a division of Neubert Aero Corp (NAC). AIRPORT BUSINESS recently spoke with NAC Dynamics, LLC representatives on the capabilities of its FAA-certified Dynamic Friction Tester™ (DFT) (patent pending) and the need in the industry.
The tow-behind, wireless, and cable-free system was designed around the need to provide an all-inclusive friction testing device for airports, says Tim Neubert, president of NAC. Up until now, to describe runway pavement braking conditions the industry has used good, fair, poor, and nil. “What does that mean?” says Neubert. “If you’re in a 737 and the airport reports braking condition good, and I’m in my Learjet or my Cessna 172, that variable means something different to each aircraft.
“But when the airport reports actual friction value, those aircraft all have different performance ratings on that number. The flight computers that these airlines have been using for the past 15 years require that number to be put in, but it isn’t because the industry is still using good, fair, poor, nil.”
According to Barry Goff, VP of research and development for NAC, friction machines that are on the market today measure the coefficient of friction, designated by the Greek symbol Mu. “That Mu actually means the rolling resistance and the skidding resistance together. So the value that you actually give to the pilot is the combination of the skidding resistance and the rolling resistance. So the pilot know whether the rolling resistance has increased or decreased or whether it is the skidding resistance that’s increased or decreased.”
The Dynamic Friction Tester™ is designed to split out those two values. The device has two independent measuring tires; one measures the Mu factor, while the other measures the rolling resistance of the surface. “If you minus one from the other,” explains Goff, “you actually get the skidding resistance of the surface. So we have two wheels that measure three things.”
Goff says rolling resistance is an important measurement because if a runway or surface is dry, the runway resistance will just be the rolling of the tire on a dry service. However, as soon as there is water, snow, ice, or a contaminant in front of that tire, the rolling resistance increases, but the friction value may not necessarily increase at that point. The DFT, offering both values, gives pilots a more accurate reading of conditions on that runway.
Historically, says Goff, the device used to measure runway friction (decelerometer) gives some three to six readings per length of the runway. “That doesn’t accurately locate low friction areas,” he says. “It just gives the operator a total runway average.”
The NAC Dynamics DFT is designed to perform continuous readings over the length of the runway. The final reading is at one reading every meter, but it’s averaged out because, Goff says, it would be too much data. “We get one reading roughly every 34 milliseconds.”
The forces are measured by two axis transducers physically mounted on each wheel, explains Goff. “We’re measuring the forces exerted on the tires. That’s transmitted wirelessly to a portable computer on the tow vehicle that’s towing the DFT as we drive down the runway — so there’s no cables. Then we have a facility to either transmit that data, if we like, to the tower. Or, more commonly, they would just radio to the tower, and then the tower would radio to the pilot what the friction level is.”
For winter operations, the device also features a laser that shoots down to the pavement surface to tell the operator what the temperature of the pavement is as well as the ambient temperature. Explains Neubert, “That’s important for when they do winter operations to be able to identify the pavement temperature to know how to adjust their winter operations. Whether or not they need to apply sand, urea, or ethylene glycol to deice the runway.” This results in cost savings for the airport while being more environmentally friendly. Adds Goff, “Currently airports flood the whole length of the runway with deicing fluid. With this you would only go out and do deicing on [needed] portions of the runway.”
A 500-liter water tank is also part of the tow-behind, suitable for performing summertime friction condition testing.
For more information, visit www.airportnac.com.
The following product descriptions of equipment are offered as a service to readers and are not intended as an endorsement. To obtain more information on any item listed, contact the manufacturer or visit www.airportbusiness.com.
ARTIFICIAL TURF used by airports in lieu of natural turf in runway and taxiway safety areas is available from Avturf LLC. The aerospace synthetic surface is designed to improve safety, increase operational efficiency, improve capacity, reduce costs, and enhance the environment. www.avturf.com.
THE CYCLONE STYSTEM from Cyclone Surface Cleaning, Inc. is designed to remove runway rubber; clean ramps; recover glycol; remove paint lines; and clean parking garages. The system removes petroleum-based waste and other contaminants from concrete and asphalt with no discharge to the environment and no damage to the cleaned surface; www.cycloneclean.com.
GLASS BEADS, used in airport pavement striping and safety products, are available from Flex-O-Lite. The exclusive Hi-Index Type III Airport glass bead is designed to provide better retroreflectiveness. Also designed to increase situational awareness; www.flexolite.com.
A LINE OF RUNWAY BROOMS is designed and manufactured by M-B Companies, Inc. Includes dedicated and multi-purpose front mount brooms, multi-function, and towed brooms. M-B also offers a line of attachment brooms and pavement marking/striping equipment; www.m-bco.com.
REJUVASEAL® asphalt sealer/rejuvenator for airport runways and taxiways is available from Pavement Rejuvenation International, LP. The three-in-one treatment is designed to seal, protect, and revitalize asphalt pavement; designed to penetrate the surface of asphalt and become an integral part of the binder. Reduces viscosity and brittleness; increases ductility and flexibility; treated surfaces are fuel, water, and chemical resistant; www.rejuvaseal.com.
RUBBER AND PAINT REMOVAL SERVICES are provided by Rampart Hydro Services. Units operate at 36,000 psi and 16 gpm to remove rubber and paint from asphalt and concrete surfaces. Equipment is designed to be mobile and can exit the runway within 60 seconds. Rubber is removed from within the groves of the runway, restoring the friction coefficient. Paint removal ranges from surface cleaning in preparation for repainting to 100 percent removal without damage to asphalt or concrete surfaces; www.rampart-hydro.com.
THE POLYPLANER RANGE, from Schibeci Road Services Pty Ltd, is designed to be an aggressive removal tool to cut, level, or polish steps in concrete or asphalt, runways, taxiways, and aprons. Available in various widths of nine to 18 inches; www.schibeci.com.
TRAFFIC COATINGS AND FEDERAL SPECIFICATION PAINT are manufactured and supplied by TMT-Pathway; visit www.tmtpathway.com.
THE STARJET™ system from NLB Corp. is designed to remove runway markings. Rotating water jets (up to 40,000 psi) remove up to 7,000 feet per hour, without damaging runway. Self-contained NLB system includes water tank, ultra-high pressure pump, and optional vacuum unit; www.nlbcorp.com.
TRACR II AND SNOMETR touch screen-based runway surface condition reporting and monitoring equipment are developed and manufactured by Tradewind Scientific Ltd. The company is also the North American agent for Findlay Irvine GripTester, SARSYS SFT and TES Decelerometer Friction Measuring Instruments; www.TradewindScientific.com.
DIAMOND SHIELD FORTIFIER is available from SGA Global. DSF is designed to allow users to open pavement to vehicle traffic in just two to four hours; www.sgaglobal.us.
THE DRS511 RUNWAY SURFACE CONDITION SENSOR is available from Vaisala. Reports generated include: runway wet; frost on runway; snow on runway; ice on runway. The DRS511 is compatible with all Vaisala AWOS; www.vaisala.com.
THE STRIPE HOG SYSTEM from Waterblasting.com is designed to remove all types of markings and runway rubber. The system utilizes a 40,000 psi pump at 6-12 gpm to produce the cutting power necessary to remove markings. Includes full vacuum recover and is designed to remove 100 percent of markings without damage to surface; www.waterblasting.com.
GLASGRID PAVEMENT REINFORCEMENT, from Saint-Gobain Technical Fabrics, is designed to prevent reflective cracking. Glas Grid is a high-strength fiberglass mesh capable of turning stresses horizontally so they may be dissipated within the new overlay, minimizing crack reflection. The material is self- adhesive; www.glasgrid.com.
NEWLIFE LIQUID POTHOLE FILLER is available from NewLife Surface Solutions, L.L.C. Designed to be a low temperature, liquid mix that conforms to fill potholes and cracks with adhesion and not track in the sun or fracture in sub-zero temperatures; www.potholefiller.net.
T-17 MMA POLYMER CONCRETE PATCHING MATERIAL for runway rehabiliation is available from TRANSPO Industries, Inc. Designed to provide a rapid cure time, it can be used as a neat mortar for thin patches, overlays, grouting, or filled with special aggregate for full-depth single-pour patches; www.transpo.com.
