1、NASA TECHNICAL NOTECONASA TN D-/351pyCORNERING CHARACTERISTICS OFA 40 x 14-16 TYPE VII AIRCRAFT TIREAND A COMPARISON WITH CHARACTERISTICSOF A C40 x 14-21 CANTILEVER AIRCRAFT TIREby John A. Tanner and Robert C. DreherLaug/ey Research CenterHampton, Va. 23665NATIONAL AERONAUTICS AND SPACE ADMINISTRATI
2、ON WASHINGTON, D. C. OCTOBER 1973Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No.NASA TN D-73512. Government Accession No.4. Title and SubtitleCORNERING CHARACTERISTICS OF A 40 X 14-16 TYPE VHAIRCRAFT TIRE AND A COMPARISON WITH CHARACTER
3、-ISTICS OF A C40 X 14-21 CANTILEVER AIRCRAFT TIRE7. Author(s)John A. Tanner and Robert C9. Performing Organization Name and Address. DreherNASA Langley Research CenterHampton, Va. 2366512. Sponsoring Agency Name and AddressNational Aeronautics and Space AdministrationWashington, D.C. 205463. Recipie
4、nts Catalog No.5. Report DateOctober 19736. Performing Organization Code8. Performing Organization Report No.L-904610. 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 investigation wa
5、s conducted at the Langley aircraft landing loads and traction facilityto determine the cornering characteristics of a 40 X 14-16 type VTJ aircraft tire. Thesecharacteristics, which include the cornering -force and drag -force friction coefficients andself -alining torque, were obtained for the tire
6、 operating on dry, damp, and flooded runway sur-faces over a range of yaw angles from 0 to 20 and at ground speeds from 5 to 100 knots, bothwith and without braking.The results of this investigation indicated that the cornering capability of the 40 X 14-16type Vn aircraft tire is degraded by high gr
7、ound speeds, thin -film lubrication and tire hydro-planing effects on the wet surfaces, and brake torque. The cornering capability is greatlydiminished when locked-wheel skids are encountered.A comparison of the cornering characteristics of the 40 x 14-16 type VII aircraft tireand those of the C40 x
8、 14-21 cantilever aircraft tire presented in NASA TN D-7203 indicatedthat the cornering capability of the cantilever tire is greater than the cornering capability ofthe conventional tire on the dry surface but is less than that of the conventional tire on the wetsurfaces at high ground speeds. At 10
9、0 knots, the conventional tire develops a higher drag-force friction coefficient than the cantilever tire for most test conditions.17. Key Words (Suggested by Author (s) IAircraft tireHigh-speed corneringFriction coefficients19. Security Oastif. (of this report)Unclassified18. Distribution Statement
10、Unclassified - Unlimited20. Security Classif . (of this page)Unclassified21. No. of Pages 22. Price*Domestic, $2.7525 Foreign, $5.25For sale by the National Technical Information Service, Springfield. Virginia 22151Provided by IHSNot for ResaleNo reproduction or networking permitted without license
11、from IHS-,-,-CORNERING CHARACTERISTICS OF A 40 X 14-16 TYPE VH AIRCRAFTTIRE AND A COMPARISON WITH CHARACTERISTICS OF AC40 X 14-21 CANTILEVER AIRCRAFT TIREBy John A. Tanner and Robert C. DreherLangley Research CenterSUMMARYAn investigation was conducted at the Langley aircraft landing loads and tract
12、ionfacility to determine the cornering characteristics of a 40 x 14-16 type VII aircraft tire.These characteristics, which include the cornering-force and drag-force friction coeffi-cients and self-alining torque, were obtained for the tire operating on dry, damp, andflooded runway surfaces over a r
13、ange of yaw angles from 0 to 20 and at ground speedsfrom 5 to 100 knots, both with and without braking.The results of this investigation indicated that the cornering capability of the40 x 14-16 type VEI aircraft tire is degraded by high ground speeds, thin-film lubricationand tire hydroplaning effec
14、ts on the wet surfaces, and brake torque. The cornering capa-bility is greatly diminished when locked-wheel skids are encountered.A comparison of the cornering characteristics of the 40 x 14-16 type VTI aircrafttire and those of the C40 x 14-21 cantilever aircraft tire presented in NASA TN D-7203ind
15、icated that the cornering capability of the cantilever tire is greater than the corneringcapability of the conventional tire on the dry surface but is less than that of the conven-tional tire on the wet surfaces at high ground speeds. At 100 knots, the conventional tiredevelops a higher drag-force f
16、riction coefficient than the cantilever tire for most testconditions.INTRODUCTIONAs the costs and program risks associated with aircraft flight tests increase rapidly,many airplane manufacturers are relying on computer simulations to play a major role inthe development of new airplane designs and mo
17、difications. Recently the scope of thesecomputer studies has expanded to include landing-gear design problems. One of the con-sequences of this computer technology boom has been an increased demand for experimen-tal data on the aircraft tire high-speed lateral-friction characteristics needed to defi
18、neaircraft cornering capabilities and to update tire shimmy analyses. References 1 to 5 areProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-examples of early research papers which present the results of studies of the low-speedyawed-rolling characteri
19、stics of several aircraft tires. Reference 6, a more recent-paper, presents the results of a study of the high-speed cornering characteristics of aC40 x 14-21 aircraft tire of cantilever design. However, no data are available on the.high-speed cornering characteristics of the conventional 40 x 14-16
20、 aircraft tire whichis used on many of the same commercial and military aircraft as the cantilever tire.The purpose of this paper is to present the results of an investigation conducted atthe Langley aircraft landing loads and traction facility to define the cornering character-istics of a 40 x 14-1
21、6 type VTI aircraft tire and to compare the results of this investiga-tion with the cornering characteristics of the C40 x 14-21 cantilever tire presented inreference 6. These characteristics, which include the cornering-force and drag-forcefriction coefficients and self-alining torque, were obtaine
22、d for the tire operating on dry,damp, and flooded runway surfaces over a range of yaw angles from 0 to 20 at groundspeeds from 5 to 100 knots, both with and without braking.SYMBOLSMeasurements and calculations were made in U.S. Customary Units and convertedto SI units. Values are given in both SI an
23、d U.S. Customary Units.TJ T,D brake torque measured on dry surfaceTz self-alining torqueV ground speed/LI, drag-force friction coefficient parallel to direction of motionu cornering-force friction coefficient perpendicular to direction of motions* wheel yaw angleAPPARATUS AND TEST PROCEDURETest Tire
24、sThe tires used in this investigation were size 40 x 14-16, type VII, bias-ply aircrafttires of 22 ply rating and had a rated maximum speed of 200 knots (1 knot = 0.5144 m/sec).Photographs of the conventional tire and of a cantilever tire of similar outside dimensionProvided by IHSNot for ResaleNo r
25、eproduction or networking permitted without license from IHS-,-,-are presented in figure 1. The conventional tire is shown before testing, and the cantile-ver tire is shown after testing. Throughout this investigation, the tire inflation pressurewas maintained at 1070 kPa (155 psi) and the vertical
26、load was fixed at a nominal value of 111 kN (25 000 Ib). (These loading conditions are the same as those used during thecantilever tire tests of ref. 6.) The tire was replaced when approximately 50 percent of the original tread was worn off.The cross section of the cantilever tire and that of the co
27、nventional tire are shownin figure 2. As illustrated, the larger rim opening available with the cantilever tire pro-vides space for a larger brake assembly without increasing the tire outside diameter.An additional advertised feature of the cantilever tire is its “run-flat“ capability. In theevent o
28、f complete loss of inflation pressure, the tire purportedly collapses symmetricallywithout folding to one side as does the conventional tire.Runway Surface ConditionsFor the tests described in this paper, approximately 174 m (570 ft) of a concretetest section were divided into three subsections to p
29、rovide tire cornering data on dry,damp, and flooded surfaces. The first 76 m (250 ft) of the test section were maintaineddry; the next 37 m (120 ft) were dampened (no visible standing water); and the remaining61 m (200 ft) were surrounded by a dam and flooded with water to a depth of approxi-mately
30、0.8 cm (0.32 in.). Thus, during one test, data were obtained for the three sur-face wetness conditions. The dry subsection was necessarily long to provide time forfull wheel spinup and, for those tests which involve braking, time for brake actuation.The concrete surface in the test section had a lig
31、ht broom finish which was somewhatsmoother than that of most operational concrete runways.Test FacilityThe investigation was performed at the Langley aircraft landing loads and tractionfacility, which is described in reference 7, and utilized the main test carriage whichweighs approximately 534 kN (
32、120 000 Ib). Figure 3 is a photograph of the carriage withthe installed test wheel assembly, and figure 4 is a closeup view of the wheel and showsdetails of the instrumented dynamometer which supports the wheel and measures the vari-ous axle loadings. In figure 5 is presented a schematic of the dyna
33、mometer instrumenta-tion which consisted of load beams to measure vertical, drag, and lateral forces and linksto measure brake torque, all at the wheel axle. Additional instrumentation was providedto measure brake pressure, wheel angular displacement, and carriage horizontal displace-ment. Continuou
34、s time histories of the output of the instrumentation were recorded by anoscillograph mounted on the test carriage. For this investigation, a landing-gear strutwas not employed because the dynamometer was needed to measure the forces andmoments accurately.3Provided by IHSNot for ResaleNo reproductio
35、n or networking permitted without license from IHS-,-,-Test ProcedureThe test procedure consisted of setting the dynamometer and tire assembly to thepreselected yaw angle, propelling or towing the test carriage to the desired ground speed,releasing the drop-test fixture to apply the preselected vert
36、ical load to the tire, andmonitoring the output from the onboard instrumentation. The yaw angle was increasedin 5 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 a ground vehicle; for higher speeds, thecarriage was pro
37、pelled by the hydraulic jet as described in reference 7. In tests whichincorporated wheel braking, the brake was actuated after the vertical load had beenapplied and the tire was in a steady-state rolling condition. Time histories of the outputof the instrumentation were recorded as the tire passed
38、consecutively over the dry, damp,and flooded test surfaces.40 x 14-16 TYPE VH AIRCRAFT TIRE RESULTSTime histories of forces in the vertical, drag, and side directions; brake torque;and wheel angular velocity were recorded on an oscillograph throughout each test. Thesetime histories were used to comp
39、ute steady-state values of the cornering-force frictioncoefficient i perpendicular to the direction of motion and the drag-force friction coef-sficient y. j parallel to the direction of motion. The self-alining torque Tz is a groundtorque in the footprint which is developed about the vertical or ste
40、ering axis of the wheeland which alines the tire with the direction of motion when positive; it is computed fromthe load transfer between the two drag-load beams shown in figure 5. In this section arediscussed the effects of yaw angle, ground speed, brake torque, and surface wetness onthe cornering
41、characteristics of the 40 x 14-16 type VII aircraft tire.Effect of Yaw AngleThe effect of yaw angle on the cornering-force and drag-force friction coefficientsand self-alining torque of the 40 x 14-16 type VH aircraft tire is presented in figure 6 forvarious ground speeds, surf ace-wetness condition
42、s, and braking torques.Cornering-force friction coefficient.- Data which describe the effect of yaw angleon the cornering-force friction coefficient /ig developed with and without braking arepresented in figure 6. The brake torque values given in the figure were those measuredon the dry surface; the
43、se same brake pressures were used in the tests on the damp andflooded surfaces. For the unbraked condition, the data presented in figure 6(a) indicatethat, in general, /ig increases with an increase in yaw angle, reaches a maximum value,and then decreases with further increases in *. Increasing the
44、ground speed reduces thevalue of i , particularly at the higher yaw angle and on the wet surfaces. Furthermore,increasing the ground speed reduces the yaw angle at which maximum cornering is devel-4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-oped
45、. Typically, the maximum cornering at 5 knots is developed at a yaw angle of approxi-mately 15, whereas the maximum cornering at 100 knots appears to occur at about 10.The data presented in figures 6(b) and 6(c) indicate that the braking effort of these tests -resulted in a locked-wheel skid on the
46、flooded surface at all yaw angles with correspondingnegligible values of /g. Partial wheel spindown occurred with light braking on the dampsurface at a yaw angle of 15 and locked-wheel skids occurred at all yaw angles on thatsurface during heavy braking.Drag-force friction coefficient.- Figure 6 als
47、o shows the effect of yaw angle on thedrag-force friction coefficient /n,. The data obtained without brake torque (fig. 6(a)indicate that p., generally increases with an increase in yaw angle and decreases withincreasing ground speed on all three surfaces, particularly at high yaw angles. Dataobtain
48、ed with light and heavy braking (figs. 6(b) and 6(c) also indicate that /i increaseswith increasing yaw angle but, as expected, at a higher level at a ground speed of 5 knots.At 100 knots, either wheel spindown or wheel lockup reduces the value of fi, to about0.1 or less on the damp and flooded surf
49、aces.Self-alining torque.- The effect of yaw angle on the self-alining torque Tz is alsoshown in figure 6. The data indicate that for most test conditions presented, Tz gener-ally increases from zero to a maximum positive value at a 5 yaw angle and then decreaseswith a further increase in yaw angle. The self-alining torque generally decreases when theground speed is increased, especially on the we
