1、NASA TECHNICAL NASA TM X- 72695MEMORANDUM(NASA-TM-X-72695) THE EFFECT OF .CHINE TIRES N75-23555ON NOSE GEAR WATER-SPRAY CHARACTERISTICS OFA TWIN ENGINE AIRPLANE (NASA) 26 p HC $3.75CSCL 01C Unclas G3/05 21787THE EFFECT OF CHINE TIRES ON NOSE GEAR WATER-SPRAY CHARACTERISTICSOF A TWIN-ENGINE PROPJET A
2、IRPLANEByThomas J. Yager, Sandy M. Stubbsand John L. McCarty0)This Informal documentation 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 incorporate
3、d in another publication.NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONLANGLEY RESEARCH (ENTER, HAMPTON, VIRGINIA 23665Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No. 2. Government Accession No. 3. Recipients Catalog No.TM X-726954. Titl
4、e and Subtitle 5. Report DateTHE EFFECT OF CHINE TIRES ON NOSE GEAR WATER-SPRAYCHARACTERISTICS OF A TWIN-ENGINE PROPJET AIRPLANE 6. Performing Organizatio Code7. Author(s) 8. Performing Organization Report No.Thomas J. Yager, Sandy M. Stubbs, and John L. McCarty10. Work Unit No.9. Performing Organiz
5、ation Name and Address 505-08-31-01NASA Langley Research Center 505-08-31-01Hampton, VA 23665 11. Contract or Grant No.13. Type of Report and Period Covere612. Sponsoring Agency Name and Address Technial MemorandumNational Aeronautics both complicated by the directional controlProvided by IHSNot for
6、 ResaleNo reproduction or networking permitted without license from IHS-,-,-requirements generally introduced when flameouts occur on multi-engine aircraft.Such a spray ingestiop problem has been encountered during operations ofthe Merlin IV, a twin-engine, prop4et, business-type airplane manufactur
7、ed bySwearingen Aviation Corporationr. On several occasions, this airplane suffereda loss of power, attributed to the ingestion of slush and water spray whichemanated from the nose gear tires. Typicall, this problem occurred undercrosswind conditions, only with the downwind engine, at speeds 4pproac
8、hing60 knots while operating in fairly deep slush, In addition to entering theengine air intake, the slush was observed to restrict the air flow to theoil cooler also located-at the front ofthe engine nacelle. In an attempt toalleviate this operational problem, NASA was requested by the FAA to assis
9、tthe airplane manufacturer in explorig the erits of equipping the nose gearof that airplane with Ichine“ tires. A qhine tire is one constructed with anextending lip molded into the sidewall just above the tread. This type oftire is generally designed to deflect water and slush to the side and awayfr
10、om intakes on aft-fuselage mounted jet engines. :Such tires are currentlyin service on several .commercial jet transports.The purpose of this paper is to present the results from an experimentalstudy to evaluate the effectiveness of nose gear chine tires in eliminatingor minimizing the spray ingesti
11、on problem associated with the Merlin IV air-plane. Accelerate-stop tests were conducted with the airplane cn the LandingResearch Runway at the NASA Wallops Fright Center. That runway was selectedbecause it was equipped with easily isolated, level, test sections well-suitedfor controlling the water
12、depth. Tests were made with several nose-gear tireconfigurations over a range of airplane ground speeds, surface water depths,and wind conditions.;APPARATUS AND TEST PROCEDURETest AircraftThe aircraft used in this investigation was a Merlin IV.executive twin-engine proplet manufacturedby Swearingen
13、Aviation Corp. A photograph of thetest .airplane is presented in figure 1 and sketches which provide geometricdetails are presented in figure 2. The airplane has a dugl nose gear whichon slush-covered runways has been observed under certain conditions to intro-duce spray into the.engine air intako l
14、ocated above the propeller hub and intothe oil cooler inlet located below and slightly aft of the hub. The locationof these intakeq relative to the nose gear is noted in figure 2(b). Also notedis the mean location of the wing leading edge between the engine nacelle andthe fuselage, as it is used lat
15、er for identifying spray locations. For thisinvestigation, the aircraft was lightly loaded and its mass was estimated tobe 3855 kg (850P lbm). At this mass, the-.static loading on the nose gear wasapproximately 4.45 kN (1000 lbf).The forward baggage compartment doors were removed from the test aircr
16、aftto provide space for mounting a motion picture camera, visible in figure 1.This camera provided a near head-on view of the spray in the vicinity of2Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the engine.Test TiresPhotographs of the nose gear t
17、est tires are presented in figure 3(a)and cross-sectional schematics are presented in figure 3(b). Tire A, thestandard tire currently in use op th the nearest being a size 18 x 4,4 whiqh, when fullyinflated, is approximately 5.1.cm (2 in.) larger in diameter than the stand-ard tire for this airplane
18、. Two chine tires of this size but of differentconfiguration were selected for testing in this study and designated as tiresC and D. As shown in figure 3(b) the chine for tire C extended 1.37 cm(0.54 in.) beyond the sidewall at a radius 3.63 cm (1.43 in.) less than theundeflected tire radius. The ch
19、ine for tire D protruded 1.32 cm (0.52 in.)beyond the sidewall at a radius 2.92 cm (1.15 in.) less than that of the unde-flected tire. Thus, for equal load and inflation pressure, the chine of tireD was slightly closer to the runway surface than that of tire C.Test tire B is a conventional tire of t
20、he spane size as that of the twochine tires, and was included in the program to provide data for evaluatingdirectly any possible merits for achine tire. The standard size 16 x 4.4tire (tire A) was tested at an inflation pressure of 550 kPa (89 psi) where-as the larger size tires were inflated to onl
21、y 340 kPa (50 psi) - the pressureidentified by the airplane manufacturer necessary to provide the same loadfactor on the aircraft structure. The tread pattern of the various test tiresdiffered because tires with a uniform pattern were not available when the pro-gram was conducted. These tread differ
22、ences, observable in figure 3, wereconsidered to have an insignificant effect on the developed water spraypatterns.Runway Test SurfacesThe tests were conducted on the 2670m (8750 ft) Landing Research Runwayat Wallops Flight Center because the unique, flat-surface test section ofthat runway provided
23、a ipeans for obtaining a uniform pontrolled water depthwhich was considered essential for describipg the water spray patternsdeveloped by the airplane during a test run. Figure 4 presents a geometriclayout of the runway test section and shows the three areas which wereflooded for testing. Each area
24、consisted of a strip 1.8m (6 ft) wide toaccomodate the nose gear and 107m (350 ft) long, bounded by dams and floodedto designated depths by means of fire department tank trucks as shown infigure 5. Test areas 1 and 2 were flooded to a nominal water depth of 1.27cm (0.5 in.) and test area 3 was flopd
25、ed to a depth of 2.54 cr (1 in.). Damswere also installed 7.6m (25 ft) either side of the centerline of eachflooded test strip to retard the water dispersion across the entire 45.7 m(150 ft) runway width.The surface of the runway in test areas 1 and 3 was smooth concretewhereas that of area 2 was eq
26、uippe4 with transverse grooves 0,63 cm (1/4 in.)wide and deep, spaced 2.54 cm (1 in.),apart. Thus, areas 1 and 2, flooded to3Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the same nominal depth, provided the opportunity to evaluate what effectsgroo
27、ving might have on the nose wheel water spray characteristics duringflooded runway operations.Photographic CoverageThe extensive photographic coverage of the tests supplied the only meansfor gathering spray data. Motion picture (16 mm) cameras, a 70 mm sequencecamera, 35 mm hand-held cameras and tel
28、evision cameras were employed for eachtest run and the photographs in figure 6 indicate the scope of the coverage.The onboard motion picture camera was mounted just outside the fuselage at theforward baggage compartment door and looked aft at the engine and the wingleading edge (figure 6(a). This ca
29、mera was placed on the downwind side ofthe airplane since it was the downwind engine which was most susceptible toflameout due to spray ingestion. The photograph of figure 6(b) is typical ofthe 35 mm camera coverage obtained by observers positioned on the downwind sideof the runway adjacent to each
30、of the three test areas. A motion picturecamera together with a television camera were mounted onboard a helicopter toprovide an overhead view (figure 6(c) of some of the test runs. An Inter-mediate Focal Length Optical Tracker (IFLOT) trailer, mounted with two motionpicture cameras equipped with di
31、fferent lenses, was located on each side ofthe runway and at the end of test area 3. Film frames obtained from the twocameras on the downwind IFLOT trailer are shown in figure 6(d) (150 mm lens)and figure 6(e) (85 mm lens). Also mounted on this downwind IFLOT was atelevision camera whose signals, li
32、ke those from the helicopter TV camera, wererecorded on tape for immediate viewing. The motion picture cameras on theupwind IFLOT were identical to those on the downwind side but, instead of aTV camera, that IFLOT was equipped with a 70 mm sequence camera which was usedduring some of the runs, prima
33、rily for documentary photographs.A single, tripod-mounted 16.mm motion picture camera was positioned atthe edge of the runway near the end of test area 3 in an attempt to obtain anearly head-on view of the spray pattern. This camera, operated remotely forsafety reasons, could not be panned to track
34、the airplane or zoomed to get abetter view of test areas 1 and 2 in the distance. Consequently, it was usedonly to aid in defining the spray characteristics of the airplane while tra-versing test area 3 (see figure 6(f).Test ProcedureThe procedure for each test run began with the wetting process. Af
35、terthe tank trucks flooded the three 1.83 m (6 ft) wide test strips to approxi-mately the desired depths (1.27 cm (0.5 in.) in areas 1 and 2; 2.54 cm (1 in.)in area 3), observers at each area recorded the average of many water-depthmeasurements and the runway was cleared. For each run, the pilot acc
36、eleratedthe airplane rapidly to the desired test speed and attempted to maintain thatspeed as the airplane traversed the three test areas with the nose gearcentered in the flooded strips. Motion picture cameras were started prior tothe airplane entering the first test area; other cameras were operat
37、ed afterthe spray pattern had been developed in each test area. Following each run,the observer at each test area would again measure water depths and instructIGI PAG SProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the tank trucks as to the amount o
38、f water needed for the next test.The aircraft ground speed was monitored by a stationary radar systempositioned at the edge of the runway. During the course of a test run, anobserver with radio communications to the test aircraft called out to thepilot the ground speed values as obtained by the rada
39、r and the pilot adjustedthe airplane speed accordingly. The nominal test ground speeds were 40, 60,80, 95 and 110 knots.Table I is a compilation of all test run conditions and identifies foreach test the tires installed on the dual wheel nose gear of the airplane,the wind speed and heading, includin
40、g the crosswind component, the averageaircraft ground speed and the average water-depth reading in each of thethree test areas. Tire A was tested first since it was the standard tirefor the airplane and the one with which the pilot was familiar in terms ofairplane handling qualities. Furthermore, ti
41、re A was similar to that usedon the airplane when spray ingestion problems had been experienced. Tire Bwas next tested to make an orderly transition from the standard equipment0.4 m (16 in.) tire to the 0.46 m (18 in.) tire. For the initial chinetire tests, each of the chine tires, C and D, were ins
42、talled only on thedownwind side of the dual tire nose gear with a conventional 0.46 m (18 in.)tire retained on the upwind side. Subsequent to these tests, dual tires ofthe same chine design were run over an expanded speed range including onerun with reverse thrust applied as the airplane entered tes
43、t area 3 (run 17for tire D and run 22 for tire C). The test program was concluded withadditional runs on dual standard tires (tire A) at water depths more con-sistent than in the initial runs with that tire (runs 1, 2 and 3).RESULTS AND DISCUSSIONThe results from this experimental program were deriv
44、ed primarily froma study of the photographic and television coverage employed during thecourse of each test. Figures 7, 8 and 9 are typical photographs presented toillustrate the effects of. such.Itest- variables as aircraft ground speed, tireconifiguration, and surface. water depth on the spray pat
45、tern produced by thenose gear during flooded runway operations. Figure 10 attempts to summarizeall of the test data by defining the approximate grid location of the down-wind water-spray core in the vertical plane which contains the wing leadingedge. These core locations are based upon estimates mad
46、e by observers re-viewing the photographic and television coverage and hence are somewhat sub-jective. The spray patterns from the conventional and chine tires are dis-cussed in the paragraphs which follow.Conventional TiresTire A was tested because it was the tire employed when the airplanehad expe
47、rienced spray ingestion problems while in service. Tire B was testedbecause it was a conventional tire of the same size as the two chine tires.These tires provided baseline data for comparison with the chine-equippedtires.5Provided by IHSNot for ResaleNo reproduction or networking permitted without
48、license from IHS-,-,-The spray pattern of the conventional tire is highly dependent upon theaircraft ground speed as noted in figures 7(a) and 10. Below the criticalhydroplaning speed.(the hydroplaning speed V, in knots, is approximated bythe equation, V = pV , where p is the tire inflation pressure
49、 in psi), alarge portion of the spray appears to emanate from the side of the tire foot-print, yet there is an apparent bow wave which throws spray ahead of andover the tire to the extent that the tire is typically hidden in spray mist(see figure 7(a). Above the critical hydroplaning speed, no bow wave isevident, the tire is quite visible, and the spray is directed aft and to theside of the tire footprint.As noted
