1、NASA TECHNICAL NOTECOm13- 106%ASA TN D-7203EXPERIMENTAL INVESTIGATION OFTHE CORNERING CHARACTERISTICS OFA C40 x 14-21 CANTILEVER AIRCRAFT TIREby Robert C, Dreher and John A. TannerLangley Research CenterHampton, Va. 23365NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. APRIL 1973Provi
2、ded by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No. 2. Government Accession No.NASA TN D-72034. Title and SubtitleEXPERIMENTAL INVESTIGATION OF THE CORNERINGCHARACTERISTICS OF A C40 X 14-21 CANTILEVERAIRCRAFT TIRE7. Author(s)Robert C. Dreher and
3、 John A. Tanner9. Performing Organization Name and AddressNASA Langley Research CenterHampton, Va. 2336512. Sponsoring Agency Name and AddressNational Aeronautics and Space AdministrationWashington, D.C. 205463. Recipients Catalog No.5. Report DateApril 19736. Performing Organization Code8. Performi
4、ng Organization Report No.L-876610. Work Unit No.501-38-12-0211. Contract or Grant No.13. Type of Report and Period CoveredTechnical Note14. Sponsoring Agency Code15. Supplementary Notes16. AbstractAn experimental investigation was conducted at the Langley aircraft landing loadsand traction facility
5、 to define the cornering characteristics of a size C40 X 14-21 aircrafttire of cantilever design. These characteristics, which include the cornering-force anddrag-force friction coefficients and self-alining torque, were obtained for the tire oper-ating on dry, damp, and flooded runway surfaces over
6、 a range of yaw angles from 0 to20 and at ground speeds of 5 to 100 knots, both with and without braking. The resultsof this investigation show that the cornering-force and drag-force friction coefficients andself-alining torque were influenced by the yaw angle, ground speed, brake torque, suriacewe
7、tness, and the locked-rwheel condition.17. Key Words (Suggested by Author(s)Tire frictionAircraft tiresBraking and cornering -19. Security dassif. (of this report)Unclassified18. Distribution StatementUnclassified - Unlimited20. Security Classif. (of this page) 21 No. of .Pages 22. Price*Unclassifie
8、d 21 $3.00For sale by the National Technical Information Service, Springfield, Virginia 22151Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-EXPERIMENTAL INVESTIGATION OF THE CORNERING CHARACTERISTICSOF A C40 X 14-21 CANTILEVER AIRCRAFT TIREBy Robert
9、 C. Dreher and John A. TannerLangley Research CenterSUMMARYAn experimental investigation was conducted at the Langley aircraft landing loadsand traction facility to define the cornering characteristics of a size C40 x 14-21 aircrafttire of cantilever design. These characteristics, which include the
10、cornering-force anddrag-force friction coefficients and self-alining torque, were obtained for the tire oper-ating on dry, damp, and flooded runway surfaces over a range of yaw angles from 0to 20 and at ground speeds of 5 to 100 knots, both with and without braking. The resultsof this investigation
11、show that the corner ing-force and drag-force friction coefficients andself-alining torque were influenced by the yaw angle, ground speed, brake torque, surfacewetness, and the locked wheel condition.INTRODUCTIONAs the weight and landing speeds of airplanes increase, more severe demands areplaced up
12、on the braking capability of the landing-gear system for safe ground operations.One of the more efficient approaches to obtain greater brake torque for larger aircraft isto increase the brake diameter, but to do so requires a wheel with a larger diameter.This approach implies a tire with a larger di
13、ameter, an increased storage space require-ment, and added landing-gear weight. Recently, however, the tire industry introduced anew tire design which has the same overall diameter as that of the standard or conven-tional tire but with a larger inside diameter (rim opening) which permits the use of
14、largerbrakes. This design has been referred to as the cantilever tire, so-called because thesidewalls overhang the rim in an unsupported manner. A few of these cantilever tireshave become available for airplane use, and in view of the continuing interest of theNational Aeronautics and Space Administ
15、ration to determine the performance character-istics of aircraft tires of various design and construction, a study was undertaken todetermine the cornering properties of a tire of cantilever design. The purpose of thispaper is to present the results of that study. .Provided by IHSNot for ResaleNo re
16、production or networking permitted without license from IHS-,-,-An experimental investigation was conducted at the Langley aircraft landing loadsand traction facility to define the cornering characteristics of a size 40 x 14-21 aircrafttire of cantilever design. These characteristics, which include
17、the cornering-force anddrag-force friction coefficients and self-alining torque, were obtained for the tire oper-ating on dry, damp, and flooded runway surfaces over a range of yaw angles from 0to 20 and at ground speeds of 5 to 100 knots, both with and without braking.(1 knot = 0.5144 meter/second.
18、)SYMBOLSMeasurements and calculations were made in U.S. Customary Units and convertedto SI Units. Values are given in both SI and U.S. Customary Units.Brp p brake torque measured on dry surfaceTz self-alining torqueV ground speedJLI j drag-force friction coefficient parallel to direction of motionHs
19、 cornering-force friction coefficient normal to direction of motion4 wheel yaw angleAPPARATUS AND TEST PROCEDURETest TireThe cantilever tires used for this test were size 40 x 14-21 bias-ply aircraft tiresof 22 ply rating and they had a rated maximum speed of 200 knots. A photograph of oneof the tir
20、es, taken subsequent to the investigation, is presented in figure 1. Several largecommercial and military airplanes are presently using a tire of this diameter on theirmain landing gears. Throughout this investigation, the tire inflation pressure was main-tained at 107 N/cm2 (155 psi) and the vertic
21、al load was fixed at a nominal 111 kN(25 000 Ib). The tire was replaced when approximately 50 percent of the original treadwas worn off.The sketch of figure 2 compares the cross section of the cantilever tire with thatof the corresponding tire of conventional design. As illustrated, the larger rim o
22、peningProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-available with the cantilever tire provides space for a larger brake assembly withoutincreasing the tire outside diameter. An additional advertised feature of the cantilevertire is its “run-flat“
23、capability. In the event of complete loss of inflation pressure, thetire purportedly collapses symmetrically without folding to one side as does a conven-tional tire.Runway Surface ConditionsFor the tests described in this paper, approximately 174 meters (570 feet) of aconcrete test section were div
24、ided into three subsections to provide tire cornering dataon dry, damp, and flooded surfaces. The first 76 meters (250 feet) of the test sectionwere maintained dry, the next 37 meters (120 feet) were dampened (no standing watervisible), and the remaining 61 meters (200 feet) were surrounded by a dam
25、 and floodedwith water to a depth of approximately 0.8 cm (0.32 in.). Thus, during the course of onetest, data were obtained for the three surface-wetness conditions. The dry subsectionwas necessarily long to provide time for full wheel spin up, and, for those tests whichinvolved braking, time for b
26、rake actuation. The concrete surface in the test section hada light broom finish which was somewhat smoother than that of most operational con-crete runways.Test FacilityThe investigation was performed at the Langley aircraft landing loads and tractionfacility which is described in reference 1 and u
27、tilized the main test carriage shown infigure 3. A photograph of the dynamometer used in the investigation is shown in figure 4and a schematic of the instrumentation is presented in figure 5. The dynamometer wasinstrumented with load beams to measure vertical, drag, and lateral forces, and thebrake
28、torque at the wheel axle. Additional instrumentation was provided to measurebrake pressure, wheel angular velocity, and carriage horizontal displacement. Continu-ous time histories of the outputs of the instrumentation were recorded by an oscillographmounted on the test carriage. For this investigat
29、ion a landing-gear strut was notemployed because the dynamometer was needed to measure the forces accurately.Test ProcedureThe test technique consisted of setting .the dynamometer and tire assembly to thepreselected yaw angle, propelling or towing the test carriage to the desired ground speed,releas
30、ing the drop-test fixture to apply a preselected vertical load to the tire, and moni-toring the outputs from the onboard instrumentation. The yaw angle was increased in5 increments from 0 to 20 and ground speeds ranged from 5 to 100 knots. To obtaina speed of 5 knots, the test carriage was towed by
31、a ground vehicle; for higher speeds,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the carriage was propelled by the hydraulic jet as described in reference 1. In testswhich incorporated wheel braking, the brake was actuated after the vertical load
32、hadbeen applied antt the tire was in a steady-state rolling condition. Time histories of theoutputs of the instrumentation were recorded as the tire passed consecutively throughthe dry, damp, and flooded test surfaces.RESULTS AND DISCUSSIONTime histories of forces in the vertical, drag, and side dir
33、ections; brake torque;and wheel angular velocity were recorded on an oscillograph throughout each test.These time histories were used to compute steady-state values of the cornering-forcefriction coefficient ns perpendicular to the direction of motion and the drag-forcefriction coefficient jid paral
34、lel to the direction of motion. The self-alining torque Tzabout the vertical or steering axis of the wheel was computed from the load transferbetween the two drag load beams shown in figure 5. The following sections discuss thevariation of these cornering characteristics with yaw angle, ground speed
35、, brake torque,and surf ace-wetness conditions and concludes with remarks on tire wear and surfacerubber contamination resulting from the high-speed yawed rolling tests.Effect of Yaw AngleThe effects of yaw angle on the cornering characteristics of the test cantilevertire are presented in figure 6 f
36、or various ground speeds, surf ace-wetness conditions,and braking torques.Cornering-force friction coefficient.- Data obtained with no brake torque (fig. 6(a)indicate that as the yaw angle i/ increases from 0, the cornering-force friction coeffi-cient MS generally increases sharply, reaches a peak v
37、alue, and then graduallydecreases with a further increase in if/. Figure 6 also shows that there is a pronouncedeffect of ground speed on ns, particularly on the damp and flooded surfaces. The lowerthe ground speed, the higher the cornering-force friction coefficient. The maximumvalue of )Lts occurr
38、ed at the lowest test speed, 5 knots, and was about 0.6 on the drysurface and about 0.5 on the damp and flooded surfaces. On the flooded runway at thehigher ground speeds ns is shown to increase slightly when the yaw angle wasincreased from 15 to 20. This increase can be attributed to an increase in
39、 the sideforce produced as the tire displaces surface water rather than to an increase in the tirefriction force. The maximum value of /is occurs at a 10 yaw angle for all casesexcept at the 5-knot speed on the dry surface.Two brake torque conditions are presented in figures 6(b) and 6(c). The brake
40、torque values given in the figures were those measured on the dry surface and the sameProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-brake pressures were used in the tests on the damp and flooded surfaces. With theintroduction of braking, the variat
41、ion of cornering-force friction coefficient with yawangle at a test speed of 5 knots was very similar to that for the unbraked wheel. Thefigures show that at 5 knots the maximum JLLS on all surfaces was developed at yawangles between 10 and 15. At a ground speed of 100 knots, maximum jig was devel-o
42、ped at a 10 yaw angle on the dry surface and at a 5 yaw angle on the damp surfacewhen brake torque was applied. However, at yaw angles greater than 5 at that speedon the damp surface, even light braking was sufficient to induce a locked wheel skidwhich reduced /is to negligible values. When the runw
43、ay surface was flooded, anybraking effort at 100 knots resulted in a locked wheel skid and a corresponding loss incornering capability, regardless of the yaw angle.Drag-force friction coefficient.- The drag-force friction coefficient ju for thefree rolling tire is shown in figure 6(a) to increase al
44、most linearly with yaw angle on thedry, damp, and flooded surfaces and to decrease slightly with increasing ground speed.Figure 6(b) shows that with a light braking effort, (j.$ increases with i/ on all threesurfaces at a ground speed of 5 knots. A similar trend is noted at 100 knots on the drysurfa
45、ce; however, at this speed light braking induces locked wheel skids on the dampsurface at high yaw angles and on the flooded surface at all yaw angles. With heavybraking (fig. 6(c), ji reaches a peak value of about 0.4 at yaw angles of 10 to 15under the three surface conditions at a ground speed of
46、5 knots. The variation in thedrag friction coefficient with yaw angle at 100 knots on the dry surface is similar to thatat the lower speed although there was a partial wheel spin down at the 15 yaw angle. Atyaw angles above 5 on the damp surface and at all yaw angles on the flooded surface,heavy bra
47、king at 100 knots caused locked wheel skids. The skidding value of n onthese wet surfaces is shown to be about 0.1 for both light and heavy braking.Self-alining torque.- A positive value of the self-alining torque Tz is a stabi-lizing torque developed at the ground about the vertical or steering axi
48、s of the wheelwhich would tend to aline an unrestrained tire with the direction of motion. The unbrakedyawed-rolling data of figure 6(a) indicate that Tz reaches a maximum positive value ata 5 yaw angle and then decreases with any further increase in yaw angle for all surfaceconditions. Negative val
49、ues of Tz are generally noted for the higher yaw angles;thereby an unrestrained tire at those angles would have a tendency to diverge from thedirection of motion. The figure further shows that ground speed has little effect on themagnitude of Tz on a dry surface; however, Tz generally decreases with increasingground speed on the wet surfaces. The data of figure 6(b) show that with ligh
