1、NASA TECHNICAL NOTE GROUND-RUN TESTS WITH A BOGIE LANDING GEAR IN WATER AND SLUSH Lungley Reseurch Center zdngley Stdtion, Hampton, NATIONAL AERONAUTICS AND SPACE Q. / ADMINISTRATION WASHINGTON, D. C. JULYY966 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
2、IHS-,-,-TECH LIBRARY KAFB, NM 0130339 NASA TN D-3515 GROUND-RUN TESTS WITH A BOGIE LANDING GEAR IN WATER AND SLUSH By Robert C. Dreher and Walter B. Horne Langley Research Center Langley Station, Hampton, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION For sale by the Clearinghouse for Federal Sci
3、entific and Technical Information Springfield, Virginia 22151 - Price $2.00 i Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GROUND-RUN TESTS WITH A BOGIE LANDING GEAR IN WATER AND SLUSH By Robert C. Dreher and Walter B. Horne Langley Research Cente
4、r SUMMARY Ground-run tests were made with a bogie-type landing gear on water- and slush- covered runways to obtain data on fluid-displacement drag, wheel spin-down, wheel spray patterns, and fluid-spray drag. Tests were made with the normal four-wheel (dual tan- dem) configuration and with configura
5、tions consisting of one and two wheels at different locations on the bogie truck. runway fluid depths ranged from 0.15 to 2.0 inches (0.38 to 5.08 centimeters). Tire inflation pressures were 25, 50, and 75 pounds per inch2 (17.2, 34.5, and 51.7 newtons per centimeterq, and the vertical load per tire
6、 was approximately 5000, 6000, or 12 000 pounds (22 200, 26 688, or 53 378 newtons) depending on the wheel configuration. Some tests were also made with a simulated wing flap mounted to the rear of the wheels in the take-off and landing positions. alleviator mounted between the wheels of the dual-ta
7、ndem wheel configuration. The ground speeds ranged from 15 to 110 knots and the In addition, a few tests were made with a spray Results indicated that ground speed, vertical load, tire pressure, fluid density, fluid depth, and wheel location affected the fluid-displacement drag, the wheel spin-down
8、characteristics, the wheel spray patterns, and the fluid-spray drag developed by this landing gear. produced a maximum drag on the upper mass which was approximately 70 percent greater than that measured on the landing gear. tandem wheel configuration reduced the maximum fluid drag approximately 45
9、percent. Fluid spray impinging on the simulated wing flap in the landing position The spray alleviator installed on the dual- INTRODUCTION The National Aeronautics and Space Administration for the past several years has been studying the adverse effects of water- and slush-covered runways on the tak
10、e-off and landing performance of airplanes. In 1960, the NASA performed slush tests on a single airplane wheel at the Langley landing-loads track. On the basis of these tests, a method for predicting airplane take-off distance in slush was developed and is presented in reference 1. This method did n
11、ot account for drag due to slush spray impinging on the airplane or for tire hydroplaning effects, since only the drag due to displacing the fluid on Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-the runway from the paths of the front wheels of the
12、 landing gear was considered. As a result of these tests and of full-scale tests of reference 2, the Federal Aviation Agency instituted the “1/2 inch rule” which prohibits jet-transport airplanes from taking off on runways covered with slush or water greater than 1/2 inch (1.27 centimeters) in depth
13、. However, uncertainties such as tire size, tire pressure, number of wheels, high forward speeds, and vertical load existed when the slush drag prediction method devel- oped with the single wheel was applied to particular airplanes. Because of these uncer- tainties, it was believed that full-scale t
14、ests on a jet transport operating in slush would provide results which would be useful in confirming or refining the slush drag prediction method. Such tests were performed in the fall of 1961 by the FAA with NASA technical assistance on a commercial jet transport owned by the FAA. The results of th
15、ese tests were reported in references 3, 4, and 5; some of these results are shown in figure 1. These results indicated that the effects on slush drag of slush-spray interference and impingement and of hydroplaning were large and, therefore, the simple theory of refer- ence 1 was not adequate to pre
16、dict slush drag. In order to obtain information on runway fluid-displacement drag, wheel spin-down, wheel spray patterns, and fluid-spray drag, the NASA conducted ground-run tests on water- and slush-covered runways at the Langley landing-loads track. A four-wheel (dual tandem) bogie landing gear wa
17、s used in these tests. Seven separate wheel config- urations, six of which consisted of one and two wheels in different locations on the landing-gear truck and the normal four-wheel (dual tandem) configuration, were used during the tests. Tests were also made with a simulated wing flap mounted to th
18、e rear of the wheels and some tests were made with a fluid-spray-drag alleviator mounted on the bogie landing-gear truck. The tests were made at various ground speeds, tire pres- sures, runway fluid depths, and vertical loads. The purpose of this paper is to present the results obtained during this
19、investiga- tion. These results show the effect of fluid-covered runways on landing-gear drag and wheel spin-down, the fluid spray patterns developed with the different wheel configura- tions, and the drag produced by fluid spray impinging on a simulated flap. In addition, the results show the possib
20、ility of reducing spray drag by means of an alleviator. SYMBOLS Measurements for this investigation were taken in U.S. Customary Units and equivalent values are indicated herein in the International System of Units (SI). Details concerning the use of SI together with physical constants and conversio
21、n factors are given in reference 6. 2 I. . I Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-tire width, inches (centimeters) bst DS Wdry tire width, inches (centimeters), at inflation pressure of 75 pounds per inch (51.7 newtons per centimetera) dra
22、g due to fluid, pounds (kilonewtons) runway fluid depth, inches (centimeters) reference runway fluid depth, 1.0 inch (2.54 centimeters) vertical load on landing gear, pounds (newtons) tire inflation pressure, pounds per inch2 (newtons per centimeter2) ground speed, knots tire hydroplaning speed, kno
23、ts ratio of wheel angular velocity on a wet runway to that on a dry runway surface APPARATUS Test Vehicle This investigation was made at the Langley landing-loads track. The test vehicle of this facility is the carriage shown in figure 2 and weighs approximately 100 000 lb (444.8 kN). steel rails wh
24、ich are 30 ft (9.14 m) apart and 2200 ft (670.56 m) long. The carriage straddles a concrete runway which has a surface similar to airport runways. A vertical drop carriage to which the test landing gear is attached is incorporated within the main carriage. Further information on the operation of thi
25、s facility is given in reference 7. This carriage is catapulted by a hydraulic jet to speeds up to 120 knots along Landing Gear The dual-tandem bogie landing gear used in this investigation was equipped with 12.50 - 16, 38- inch-nominal-diameter (96.52 cm), type 111, 10-ply -rating, dimple -tread ti
26、res. A schematic drawing of the test fixture and landing gear is shown in figure 3. oleo-pneumatic shock strut of the gear was replaced by an 8-inch-diameter (20.32 cm) The 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-bar. was carried on the fro
27、nt axle and 54 percent on the rear axle. Due to the geometry of the landing gear, 46 percent of the total static vertical load Wheel Configurations Seven configurations of the landing-gear wheels were used during the tests. These configurations, in order of testing, are shown by the sketches in tabl
28、e I. For configura- tions I, IV, V, and IA the landing gear was free to pitch about the truck-beam pivot since the pitch snubbers were removed. A wire rope fastened between the front axle and the test fixture prevented the gear from pitching down to an excessive degree when it was air- borne. Config
29、uration I was the normal condition in which all four wheels were mounted on the landing gear. In configuration 11 the two rear wheels were removed and replaced by steel bars which were attached from the wheel axles to the upper part of the vertical drop carriage. Similarly, in configuration III the
30、two front wheels were removed and replaced by steel bars. A diagonal wheel arrangement was obtained in configuration IV by removing the right front and left rear wheels. wheels in tandem. Single wheel configurations VI and VII consisted of the left front and the rear wheel, respectively. A spray-dra
31、g alleviator was attached between the dual tandem wheels for some of the tests; this configuration was designated configuration IA. Configuration V consisted of two single Water and Slush Trough Concrete dikes placed along the sides of the track runway formed a trough 9 ft (2.74 m) wide and 512 ft (
32、156.06 m) long as shown in figure 4. Temporary dams of a puttylike material were placed at each end of the trough to retain the slush and water for testing. Slush was made by the ice-crushing machine shown in figure 5. Photographs and a description of a similar slush-laying operation are given in re
33、ference 5. The crushed ice was first leveled manually to the approximate test depth desired. Just before the start of a test run, the slush was trimmed to the desired test depth by the machine shown in figure 6. The crushed ice was allowed to melt to a slushy condition before a test. The average spe
34、cific gravity of the slush used in this investigation was 0.88. TEST PROCEDURE The runway fluid depth dl and the slush density, in the case of slush tests, were measured immediately prior to each test at the eight stations along the trough shown in figure 4. Before each test, the vertical drop carri
35、age was positioned so that the landing- gear wheels were approximately 2.0 in. (5.08 cm) above the runway surface. Then the test carriage was catapulted to the desired ground speed by means of the hydraulic jet. In order to minimize landing-gear oscillations during the tests, the landing gear was 4
36、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-l allowed to contact the runway well ahead of the test section. Views of the slush bed before and after a typical test are shown in figures 7 and 8, respectively. All tests were made with freely rolling
37、 (unbraked) wheels. In the investigation, a series of tests was made with each of the wheel configura- tions shown in table I. The ground speed VG ranged from 15 to 110 knots. Tire inflation pressures p of 25, 50, and 75 lb/in2 (17.2, 34.5, and 51.7 N/cm2) were used and the runway fluid depth dl wat
38、er tests and from approximately 1.0 to 2.0 in. (2.54 to 5.08 cm) for the slush tests. The vertical load per tire for the different wheel configurations is given in table I. In addition, a few tests were made on the dual tandem wheels (configuration I) with a verti- cal load of approximately 12 000 l
39、b (53 378 N). A simulated wing flap was mounted to the rear of the landing-gear wheels as shown in figure 9. angle of 220 during tests with all the wheel configurations and also at an angle of 55O with configuration VI. the dual tandem wheels (configuration IA) as shown in figure 10. ranged from 0.1
40、5 to 2.0 in. (0.38 to 5.08 cm) for the This flap was mounted at an Tests were also made with a spray-drag alleviator mounted on INSTRUMENTATION The drag load cell shown on the sketch in figure 3 was used to measure the drag forces developed between the landing-gear wheels and the runway whereas the
41、upper mass drag dynamometer measured the total drag developed on the landing gear and the simulated wing flap (fig. 9). the drag load experienced by the simulated wing flap alone. Instrumentation was pro- vided to measure the angular velocity and displacement of each landing-gear wheel and the verti
42、cal displacement of the vertical drop carriage. The horizontal displacement and ground speed of the main carriage were obtained by means of a photocell. source from the photocell was interrupted at 10-ft (3.048 m) intervals along the runway and produced a pulse on an oscillograph-record trace. instr
43、umentation were continuously recorded during the tests by means of an 18-channel oscillograph. The difference between these two drag measurements gives The light The electrical outputs of the Several 16-mm motion-picture cameras operating at 200 frames per second and one 70-mm camera operating at 10
44、 frames per second were mounted at various locations on the main carriage in order to obtain motion pictures of the landing-gear wheels during each test. RESULTS AND DISCUSSION Previous research conducted on fluid-covered runways clearly shows that the phenomenon of tire hydroplaning can greatly inf
45、luence the tire-ground forces developed 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-_ I ll11l11llllII 11ll11l1l1 I II on aircraft. Available experimental data on hydroplaning were summarized in refer- ence 8, in which the following simple expre
46、ssion was developed for estimating tire hydro- planing speed VP = 9p where VP tire hydroplaning speed, knots P tire inflation pressure, lb/in2 (N/cm2) Since one of the main purposes of this investigation was to determine fluid drag effects on a landing gear under hydroplaning conditions, this equati
47、on was used to select tire pressures for study that would cause the test tires to hydroplane well before the maximum speed capability (approximately 120 knots) of the test carriage was reached. Fluid Drag Parameter When an unbraked tire rolls on a fluid-covered runway, as in airplane take-off, the m
48、oving tire contacts and displaces the stationary runway fluid. The resulting change in momentum of the fluid creates hydrodynamic pressures that react on the tire and runway surfaces. The horizontal component of the resulting hydrodynamic pressure force is termed If luid-displacement drag“ and the v
49、ertical component, “fluid-displacement lift.“ Additional fluid forces termed “fluid-spray thrust or drag“ and Yluid-spray lift“ are created on aircraft when some of this displaced runway fluid in the form of spray sub- sequently impinges on other parts of the aircraft such as the tires, landing gear, and flaps. The fluid drag parameter is defined as the incremental drag developed from all f
