1、ZIFx, g,f = CDPdlWVH 2 + dI 5 + dI (3)w wProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8It was found that a value of CD of 0.75 was required for the cal-culations of equation (3) to match the experimental data shown in figure 9for a 2-inch slush de
2、pth. Similarly, for the 1.3- to 1.5-inch water-depthdata shown in figure i0, it was found that a value of CD between 0.70and 0.75 was required. It is encouraging to note the similarity of theCD values obtained from the slush and water tests.At the present time no experimental data are available to c
3、heck thecalculations of this method for the condition of a tire rolling in snow.However, since it is not expected that the tire will completely removethe snow from the runway in the path of the tire as is apparently thecase for slush and water (fig. 5(c), the results should be conservative -that is,
4、 overestimation of the snow retardation force.Li260Retardation Forces Acting on Aircraft During Take-OffResults from the track investigation on a single wheel rolling on aslush-covered runway indicate that all of the slush in the path of thewheel was usually thrown from the runway with the exception
5、 of an icyfilm less than 0.i inch thick next to the runway. This phenomenon occurredat all test velocities, including velocities in excess of that requiredfor tire planing. It is assumed, therefore, that the retardation forcesdeveloped on rear wheels of a landing-gear arrangement, such as a dual-tan
6、dem bogie landing gear, are negligible and that only the leading wheelsof the landing gear need be considered. Accordingly, full slush drageffects on both nose-wheel tires and on the front four tires of the twomain gear bogies were assumed in the calculations. The four rear tiresof the two main gear
7、 bogies ar_ assumed to be free of drag due to slush.The retardation forces developed on each nose and leading main wheelduring the take-off may be calculated from equation (3) by using a valueof CD of 0.75 for slush and a value of CD between 0.70 and 0.75 forwa_er.For aircraft having negligible wing
8、 lift during the take-off roll upto rotational velocity, vertical tire deflections based on the averagevertical load acting on the tires during take-off may be used in equa-tion (3) to compute retardation force. For aircraft having a large reduc-tion in wheel load due to wing lift, it is necessary t
9、o compute the verti-cal tire deflection during take-off roll by the following means.Test results from the present investigation indicate that negligibledifferences exist between the static and freely rolling vertical-tire-deflection characteristics of the test specimen up to the maximum testforward
10、speeds (approximately 180 feet per second). It is assumed,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2ALi2609therefore, that the static vertical-tire-deflection characteristicsrepresent the take-off condition (rolling tire) with small loss inacc
11、uracy. If static vertical-load-deflection curves for the tires ofthe airplane under consideration are unavailable, the static verticaldeflection for each tire and vertical-load condition may be determinedby the following equation obtained from reference 2:F Z: g + wCz (4)2.4(p + O.08p r) _/wdIf reta
12、rdation forces due to spray impingement on other aircraft surfacesare disregarded, the total retardation force acting on an aircraft due toslush or water Fx,g,c is at any instantFx,g,e = NnFx,g,n + NmFx,g,mThe aircraft deceleration due to slush or water at any instant isFx,g,e (5)ar = WThe slush-tak
13、e-off calculation procedure requires that the variation ofaircraft horizontal acceleration with forward velocity during take-offroll on a dry runway be known. A typical variation is represented insketch 1.Iooooo0Dry-runway acceleration, aion, an0 2Velocity, VH= a - a rSketch i.Provided by IHSNot for
14、 ResaleNo reproduction or networking permitted without license from IHS-,-,-l0The net airplane acceleration an (dashed curve) on a slush- or water-covered runway maybe obtained by subtracting ar (calculated fromeq. (5) from the acceleration on a dry runway at each velocity incrementconsidered.The in
15、cremental distance traversed by the aircraft in going fromVH,0 to VH,1 = 2_Sl;_ - V 2_sI (VH,I) 2 (H,O)an, 0 + an, I(6a)In the same manner, the incremental distance traversed in going fromVH, 1 to VH, 2 = Ikq2;an, I + an, 2(6b)The curve of forward velocity plotted against runway distance for thetake
16、-off roll may be step integrated from equations (6).The comparison between an actual take-off in 0.6 inch of slush for afour-engine jet transport (ref. 4) and the predicted take-off distanceobtained by use of this method is presented in figure 13. The predictionoverestimates the actual take-off dist
17、ance by 500 feet.Li260Effect of Slush Depth on Take-Off DistanceThe predicted increase in take-off distance required for an airplanetaking off on runways covered with slush to depths equal to 0.5, 1.O, 1.5,and 2.0 inches is shown in figures 14 and 15 for two different airplanetake-off thrust conditi
18、ons. Also shown in these figures are the variationsof airplane net acceleration and slush retardation force with airplaneforward velocity. The data shown indicate that, as the slush depthsincrease, the aircraft net acceleration is reduced with correspondinglylonger take-off distances being required.
19、Increasing the aircraft take-off thrust, of course, increases anaircrafts performance on slush-covered runways as is shown in figures 14and 15. If the maximum commercial runway length available is 10,O00 feet,the take-off of an airplane having a 13,O00-pound-thrust engine configu-ration is marginal
20、for a slush depth of 1 inch and impossible for slushdepths of 1.5 and 2.0 inches. The take-off of an airplane having a17,000-pound-thrust engine configuration is marginal only for the 2.0-inchProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-iislush de
21、pth. It should be noted that the possibility of severe damageto airplane surfaces under spray impingementmight practically limit theslush depth permissible for take-off even if the airplane has the capa-bility for take-off in greater slush depths.CONCLUSIONSLi260Under the test conditions for the exp
22、erimental data on a 32 8.8,type VII, 22-ply-rating rib-tread airplane tire and the assumptions madein the studies described in this report, the following conclusions maybe stated with respect to the unbraked rolling of aircraft tires andairplanes on slush- or water-covered runways:i. The retardation
23、 forces measured on a tire rolling in slush andwater suggests a parabolic variation with increasing forward velocity.2. The retardation force acting on a tire on a water-covered runwayincreases approximately linearly with increasing water depth.3. Data obtained by use of the retardation-force equati
24、on were inreasonable agreement with experimental data when drag coefficients between0.70 and 0.75 were used.4. Calculations in which the retardation-force equation was usedtogether with the horizontal acceleration and velocity characteristicsof a jet transport operating on a dry runway were in good
25、agreement withresults obtained in an actual slush take-off of this airplane.Langley Research Center,National Aeronautics and Space Administration,Langley Field, Va., August 15, 1960.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-12REFERENCESi. Batte
26、rson, Sidney A.: Investigation of the MaximumSpin-Up Coeffi-cients of Friction Obtained During Tests of a Landing Gear Havinga Static-Load Rating of 20,000 Pounds. NASAM_MO12-20-58L, 1959.2. Smiley, Robert F., and Horne, Walter B.: Mechanical Properties ofPneumatic Tires With Special Reference to Mo
27、dernAircraft Tires.NASATR R-64, 1960. (Supersedes NACATN 4110, 1958.)5. Trant, JamesP., Jr.: NACAResearchon Friction Measurements. Proc.First Int. Skid Prevention Conf., Pt. I, Virginia Council of HighwayInvest. and Res. (Charlottesville), Aug. 1959, PP. 297-308.4. Sparks, Allan R.: Report on Effect
28、 of Slush on Ground Run Distanceto Lift-Off. Doc. No. D6-5198, Boeing Airplane Co., Jan. 1960.Li260Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-130kO,-IIcO0,1!0kOdo.r-I+-_0_0_ 0_-I.r-IbO0_0I%.r“tProvided by IHSNot for ResaleNo reproduction or netw
29、orking permitted without license from IHS-,-,-14Vertical an dra_ axleaccelerometersfL-60-6.1Figure 2.- Test fixture suspended below main carriage shown in figure i.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-!OJ/00000oocdJ_0_-_IbO.r“l_d,-t(1)bOI4
30、J04j11)4 _0o._-0I1)fflif/0%r)!%.r“tProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-:6f_Jc.,!II oococ_4_oIbO,e4,-1bD0i-),-t0%r-I4-_r_!%!OCProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-3A17!L-60-673(a
31、) Snow ice being deposited in trough.Figure 5.- Slush trough at landing-loads track.L-60-674Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-18t_!t-_roomoJL-O0-075L-60-676(b) Slush being trimmed to a 2-inch depth immediately before a test run.Figure 5
32、.- Continued.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-19IL-60-681L-60-682(c) Appearance of slush trough immediately after a test run.Figure 5- Concluded.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from
33、IHS-,-,-204._-0_0%,r-Ir_!,d%hi?,r-t!g,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-21O4!1E XIO 34o_J=_ /%/,XlO 3/ Bry _ dl Slush_ 6_ = 2.0 in._ p = 1.695 slugs/f_ 3Wat er_ d I = 0.5 in./1- _.j_ oii _ _ C_I_-2L160r2O3,=o,i_ 0 2 4 6 .BJ _ , : % :r18
34、0_z6o _ _ i150 _ vuOro_ c_rrlage Comou_ed t re de_lBc_ on (fro_ wrtical load)Forward ol wheel axle center llne(in uareczlon of moi_om)-“d_ t6 I/1.0 1.2 1.4 1,6 1.8 2.0 212 2_4 2.6 2.8 3.D 3,2 3.4 3.6 3_8 ,0T_m_,_cFigure 7.- Time histories of a typical run, showing variation of wheelloads, velocities
35、, and displacement during unbraked rolling throughslush and water troughs, p = 115 pounds per square inch.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-22oc0 _1or-tiiI!Iio0N0hi)O mt _m,-t_ .r-I,1:I %N O_ OO4-_ -r-t,._ .H,-.I hi?_a ,-t_ I1)%C_O I1)!
36、 %CO _04._!I-roOx0Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-230_O!0OJ-r4 _o 030 c_ c_J r-I0 0 0 ,_ coN c_Q.0I I Io_ H r-tf-(xjI,-I+ :3L Jo_rr_:1_ r-.IQ_,.-tr!_ “M r_Sc_IIAC_0r_0- 0r_0CO 000 _ .r_o0r_oI Ic_0c_0ql cJ_x_ _oo=oj uo_%_p_%_A0uIDoio0_
37、D,do4._,i-I%oo.r-I%4_%00-rl4-_%Io:,%Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-24Ir-4III._ It I|IIO. _ _ _“ _ ,-, r_r._s,%-.“-.o o ) 0“ _ %,0 ,o _ I i I I8 8 g 8,-4ql _a _ _e0_0j u0T%epz_%_r_o- oJ-80or-_0o0q00I0p-,-40,.-I0-_-IO0%00.eln_%00.r-t%!
38、c;,-4-r-tIomoProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A25O!Ir_!ooo r-_ O “_+_ O_ O_ _ OOD! I8 o 80ql _eo_oj uoI%ep1_%_H00ooJOA0Doo0- %d _%_ r,t%oo_ ._ -o%(1)%oo4._- _%m!,-t% goftProvided by IHSNot for ResaleNo reproduction or networking permit
39、ted without license from IHS-,-,-26r 0 - 8_JidI , slush orwater depth/_I/fJ+11 ijV wF _nway!IPOC_0Figure 12.- Tire cross section.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-270xo_JI160 Lift-off - Dry runwayPredicted; P = 1.6 slugs/ft 3- 0. in. sl
40、ush0.6 in. slushActual take-off in 0.6 in.C) slush; p : 1.5_ to 1.714slu_s/ft3_(_ef.h)I00hoGross weight . 210,000 ibAlt.- Sea levelTemp.- . h2FWind 7.3 knots head windRunway slope . ZeroFlaps 3OEngines . h operatin_ atdry take-offthrust_urbo-compr es sor s-One ogeratin_Take-off tirust 13,000 ib/en_i
41、ne2OI I I I I Io 2 h 6 8 lo 12 x lO3Runway distance, ftFigure 13.- Comparison of the calculated take-off distance with theactual take-off distance required for a four-engine jet transport ona runway covered with 0.6 inch of slush.Provided by IHSNot for ResaleNo reproduction or networking permitted w
42、ithout license from IHS-,-,-288oFGross weiFht . 210,C,_? liAlt .- Lea fewWind . 7.3 k:_ots he_d wind_rlway slope . Zerolaps Cnpin_s h oetatlr_ at drytake-of f th r_astTu/io-c _!ses_ors One oFierati_vTake-of |ilru_t 3,O(, 1/_n_neri0L_21 _ ! 1 1ksJnway _h_t_,n:e, ft5US _n_“ “_“ 2 I I I _I “_/t / J X _
43、OiJ-_ “_ _ _ Slush _e_t_ _ in. _/- : _: _:7 ?: _-_ .-/ i_-,“ .-_x._-_ ./- -_ / - _/_“ I - “20 i_O 60 I!O i_ 120 140 160Forward velocity, knol, sFigure 14.- Effect of slush depth on the take-off distance required fora four-engine jet transport operating at 210,000 pounds gross weightwith l,O00-pound-thrust engines.!Poc_0Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
