1、NA.SA TECHNICALMEMORANDUMNASA TM X-72797C_d:E(NASA-T_-X-72797) EVALUATION OF HIGHP_ESSURE.W_.TER 5LAS_ gITH ROTATING SPRAY EAB_0_ PEHCVING PAINT _N RUBBER DEPOSITS _CMAI_POPT RUNWAYS, ANE 5EVIEW OF RUNWAYSLIPPERINESS P._CEIE_.S CREATED EY RUBBERN76-12081UnclasG3/09 03927EVALUATION OF HIGH PRESSURE W
2、ATER BLAST WITH ROTATING SPRAY BARFOR REMOVING PAINT AND RUBBER DEPOSITS FROM AIRPORT RUNWAYS,AND REVIEW OF RUNWAY SLIPPERINESS PROBLEMS CREATED BY RUBBERCONTAMINATIONByWalter B. Horne, Langley Research Center andCaptain Guy D. Griswold, Base Civil EngineersLangley Air Force BaseThis informal docume
3、ntation medium is used to provide accelerated orspecial release of technical information to selected users. The contentsmay not meet NASA formal editing and publication standards, may be re-vised, or may be incorporated in another publication.NATIONALAERONAUTICSANDSPACEADMINISTRATIONLANGLEYRESEARCHC
4、ENTER,HAIIPTON,VIRGINIA23665Reproduced byNATIONAL TECHNICALINFORMATION SERVICEU S Depilttmenl o| ComntefceSpt_nilfield, VA. 22151Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted with
5、out license from IHS-,-,-,iI._-_72797 I 2.G:,m_wm,_ No4 Ti,_S_m,aEVALUATION _FHIGH PRESSURE WATER BLASTWITH ROTATING SPRAY BAR FOR REMOVING PAINT AND RUBBERDEPOSITS FROM AIRPORT RUNWAYS, AND REVIEW OF RUNWAYSL_rppED;NE_ PQnRi_I_KPRFATFI_ BY RUBBER CONTAMINATION7, Autho(s)Walter B. Home, Langley Rese
6、arch Center andCaptain Guy D. Griswold, Base Civil Engineers, LAFB9. Performing Orgenizatiofl Name and AddrmlNASA Langley Research CenterHampton, VA 2366512. Sponsming Agency Name md AddressNational Aeronautics however, the production rateswere much higher. The paint on the threshold markings was re
7、moved with onepass made forward and the second backward with the tractor-trailer rig.Runway Traction MeasurementsThe Langley Research Center (LaRC) diagonal-braked vehicle (DBV) wasused to measure the slipperiness of the runway 7/25 before and after paint andrubber removal. The DBV was developed by
8、LaRC in 1967 to measure the slipperi-ness of airport runways and is described in reference I. Since then, flighttests on CV-990, F-4D, C-141, B-727, DC-9, L-lOll, B-737, and Caravelle jetaircraft indicate that this device and braking technique can be used toestimate stopping performance for these ai
9、rcraft on wet runways within _+15%accuracy using the method shown in figure 2 which was developed in reference 2.It should be noted that such accuracy of prediction is obtained when theaircraft antiskid braking system is operating normally (no prolonged wheelskids). The flight tests also demonstrate
10、d that the DBV, as well as anyother ground vehicle friction measuring device, cannot predict aircraft stop-ping performance when anomalous antiskid braking performance, such as pro-longed wheel skids, occurs to an aircraft during braking on slippery runways.Anomalous antiskid braking performance occ
11、urrences are infrequent, not pre-dictable, and are dependent upon antiskid system design, runway slipperinesslevel, and pilot braking imputs as described in reference 3. All aircraftantiskid braking systems employed on aircraft made in the United States atthe present time are susceptable to anomalou
12、s antiskid performance, especiallyif the initial pilot brake application is hard and occurs before the wheelsare fully spun-up at touchdown under slippery runway conditions.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-For the abovereason, it is do
13、ubtful whether the DBVor any otherground vehicle friction measuring system, can be used to reliably predictaircraft stopping performance at time of landing on slippery runways untilthe “state of the art“ of antiskid braking system design advancestoeliminate such anomalousantiskid braking performance
14、s. However, it shouldbe understood that this aircraft operational problem with antiskid brakingsystem performance in no way detracts from the ability of the DBVto ratethe slipperiness of runways.DBV runway test zones.- Figure 3 shows the location of areas on LAFB run-way 7/25 chosen for DBV tests. A
15、s shown in the figure, test zones l and 4 wererubber coated. Test zone 2 was located near the middle of the runway besidethe runway centerline and is subjected to aircraft wheel traffic, but did notcontain any rubber deposits. Test zone 3 was located beside the runway edgeabreast of test zone 2. Thi
16、s test zone is subjected to neither rubber de-posits nor aircraft wheel traffic, and thus should reflect the originaltraction characteristics of the runway surface as modified only by surfaceweatherina and contamination blown on to the surface such as from dust or jetfuel. Test zone 5 was a 3(_x 150
17、-foot painted runway marker. This test zonewas also untrafficked and contained no rubber deposits.DBV test procedure.- The DBV test technique requires locking a diagonalpair of wheels on a ground vehicle (see figure 2) and measuring the stoppingdistance required to bring the vehicle to rest from a b
18、rake application speedof 60 mph. The test is performed for both wet and dry conditions of thepavement under investigation, and the wet/dry stopping distance ratio (SDR)obtained depicts the slipperiness of the pavement relative to dry conditions.Instrumentation on board the ground vehicle records gro
19、und speed, wheel speed,stopping distance, and deceleration. The ground velocity time historiesobtained during DBV braking tests can be differentiated with time and, aftercorrections for air and rolling resistance, be used to estimate the frictioncoefficients developed between the sliding (locked whe
20、el) tires and the pave-ment. Both the SDR method and this latter method were used to evaluate theslipperiness of the pavement surfaces under study in this investigation. Forthe present investigation, the DBV was equipped with ASTM E249 smooth treadtest tires (inflated to 24 psi), and the vehicle wei
21、ghed approximately5440 pounds.Runway wetting.- A LAFB fire department foam truck, filled with water andequipped with a pressurized spray bar made two passes (opposite directions)over each DBV test zone just prior to the start of the DBV wet runway brakingtests. This wetting technique deposited water
22、 uniformly over the width(approximately 15 feet) and length (150-1200 feet) of each test zone to aninitial water depth of O.05-O.04-inch as measured by a NASA water depthgage. When the water truck cleared the test zone, the DBV made its testruns. As many of 6 DBV test runs could be made on a test su
23、rface beforethe runway dried out. The elapsed time from wetting was recorded for eachDBV run. Most of the runs were conducted in the early evening and morningProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-hours from 7:00 pmto 7:00 amwhenthe runwaywa
24、s closed to aircraft trafficduring the runwaypaint and rubber removal program.Results and DiscussionThis section of the paper presents and discusses the results obtainedfrom the present investigation in removing paint and rubber deposits andrestoring tire-pavement traction by meansof high pressure w
25、ater blast usinga rotating spray bar.Paint and rubber removal production rates.- The high pressure water blastwith rotating spray bar equipment removed paint at an average rate of 3,188square feet/hour, and removed rubber at an average rate of 13,612 square feet/hour. The removal rates on paint vari
26、ed from a high of 4,800 sq ft/hour to alow of 2,057 sq ft/hour. This large rate difference occurredprimarily becauseof the different type and configurations of runway markings. For example,straight-ahead driving could be employed on runway edge markings while thresholdbar markings required frequent
27、repositioning of the equipment with a forward-backward type cleaning operation. Rubber removal rates also varied greatlywith this equipment, and ranged from a high of 17,666 sq ft/hour to a low of8,000 sq ft/hour. This variation occurredprimarily because of the differentwidth spray bars used, differ
28、ent thicknesses of rubber buildup, and someexperimenting with the rubber removal technique.Paint removal.- Visual observations and photographs taken during andafter paint removal on runways 7/25 and 17/35 (see figure l, 4, and 5), indi-cated that the high pressure water blast with rotating spray bar
29、 did anexcellent job of removing bulk paint from the runway marking areas. The bulkpaint was broken up into small particle sizes (see figure 4) which were easilyremoved from the runway by runway vacuum sweepers, especially when the pave-ment surface dried out.In most runway marking areas, a faint re
30、sidual paint stain remainedafter two passes of the cleaning equipment. Close visual inspection of thestains showed that the stains appeared to be below the top of the pavementsurface texture, and impregnated vertical or nearly vertical slopes ofpavement surface granules. These surfaces were probably
31、 not exposed to directimpingement by the high velocity water jets of the rotating spray bar. Figure5 shows a photograph taken of the approach end of runway 17 during re-paintingof the threshold bar markings after paint removal. This photograph shows someslight discoloration of the pavement surface i
32、n the paint removed areas pro-duced by the residual paint stains. Base civil engineering judged the stainproblem to be insignificant and felt that paint removal achieved on the run-ways satisfied its paint removal specifications. No pavement surface damageattributable to the paint removal equipment
33、could be found on either runway7/25 or runway 17/35 after the paint removal program was completed.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Rubber removal.- Visual observations and photographs made before andafter rubber removal on runway 7/25
34、(see figures 6 and 7) suggest that thehigh pressure water blast with rotating spray bar did an excellent job inremoving bulk rubber deposits from the runway aircraft touchdown areas.Visual inspection and photographs 6 and 7 also indicate that faint residualrubber stains are frequently left in the cl
35、eaned rubber-contaminated pave-ment surface after a single pass of the rubber removal equipment. Aspreviously mentioned, these stains are felt to be the result of the highvelocity water jets of the rotating spray bar not being able to directlyimpinge on vertical or nearly vertical faces of the pavem
36、ent surface granules.Base civil engineering judged that the just described rubber removal achievedby the high pressure water blast with rotating spray bar met its 95% rubberremoval specification requirement. Comparison of photographs in figures 6, 7,and 8 suggest that the rubber removal achieved at
37、the approach end of runway7 by the high pressure water blast with rotating spray bar was approximatelyequivalent to the rubber removal obtained by chemical treatment given thisrunway in 1970 (discussed later in the paper). It can be seen from thesephotographs that a uniform rubber removal was obtain
38、ed by both chemical andthe test rubber removal treatments. There was no evidence with these treat-ments of non-uniform rubber removal such as streaking or grooving that wasreported for mechanical grinding (reference 4) and high pressure water blastwith stationary spray bar (reference 5 and 6) treatm
39、ents. No pavement surfacedamage attributable to high pressure water blast with rotary spray bar wasevident on runway 7/25 after the rubber removal program was completed. Thehigh velocity water jets from the spray bar did, however, loosen some smallpieces of concrete contained in previously cracked a
40、reas of the concretepavement. These particular areas of the concrete pavement would have beencorrected by routine runway maintenance. The water blast rubber removaljust accelerated the loosening or unraveling process in the broken concretepavement area.Restoration of pavement skid resistance.- The a
41、pproach ends of runway7/25 were covered with medium to heavy rubber deposits that has accumulatedsince the last rubber removal program conducted on this runway in 1973 (seefigures 6 and 7). The rubber accretions in these runway areas tended to fillthe pavement surface voids and thus reduce the magni
42、tude of the average pave-ment surface texture depth as measured by the NASA grease test. In addition,the rubber-coated surfaces were very smooth and lacked microtexture. Theseeffects are shown by comparing the surface photographs and NASA grease testaverage texture depth (A.T.D.) measurements given
43、in figure 9 and 10 for thecontaminated and uncontaminated runway test zones.DBV wet/dry stopping distance ratios (SDR) obtained before and afterrubber removal by the high pressure water blast with rotating spray bar inthese test zones are shown in figure 3 and given in Table I. These datashow two di
44、fferent slipperiness effects. First, an obvious increase in run-way slipperiness (increase in SDR values) is noted for test zone 2 over testProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-zone 3 which comparestrafficked and untrafficked runwaysurface
45、s having norubber deposits. The increase in slipperiness of test zone 2 over test zone3 is attributed to aircraft tire polishing the pavementsurface in the wheeltracks during landing, taxying, and take-off operations that have occuredduring the past 31 years (present age of these pavementsurfaces).
46、The NASAgrease test measurements(see figure IO) indicate that the polishing actionmust be more associated with decreasing the microtexture rather than the macro-texture of the pavement, since the A.T.D. values for the untrafficked andtrafficked surfaces have approximately the sametexture depth range
47、. Secondly,the rubber deposits covered areas of the runway showa large increase in SDRmagnitudes over a similarly trafficked area (compare zones l and 4 with zone2 in Table I) without rubber deposits. This increase in runway slipperinessmost probably stems from the reduced pavementmicrotexture and m
48、acrotextureobtained on the rubber-coated surfaces.The data in table I indicate that the test rubber removal equipment re-movedsufficient rubber in the rubber covered areas of the runway to restoretraction levels to the trafficked no rubber condition, but not to the un-trafficked no rubber condition.
49、 This result indicates that the high velocitywater jets from the rotating spray bar cleaned the surface of bulk rubber, butdid not disturb the underlying pavementsurface. Restoring the runway trac-tion to untrafficked surface levels obviously requires retexturing the pave-ment surface to renovate the existing tire polished surface. To summarize,the high pressure water blast with rotating spray bar removedbulk r
