NASA NACA-TN-3814-1956 Effects of vertical fins near the nose of the fuselage on the directional and damping-in-yaw stability derivatives of an airplane model under steady-state an.pdf

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1、1“J1? NATIONALADVISORYCOMMITTEEFOR AERONAUTICSTECHNICAL NOTE 3814EFFECTS OF VERTICAL FINS NEAR THE NOSE OF THE FUSELAGE ONTHE DIRECTIONAL AND DAMHNG-IN-YAW STABIIXTY DERIVATIVESOF AN AIRPLANE MODEL UNDER STEADY-STATEAND OSCILLATORY CONDITIONSBy M J. Queijo and Evalyn G. WellsLangley Aeronautical Lal

2、xwatoryLangley Field, Va.WashingtonDecember 1956Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECHLIBRARYKAFB,NM.L.NATIONAL ADVISORY COMMITTEEI;llllllllllllllllllillllllllllllllFOR AERONALL CKILL7CIL”TECHNICIL NOTE 3814EFFECTS OF VERTICAL FINS NTAR

3、 THE NOSE OF THE FUSELAGE ONTHE DIRECTIONAL AND DAMPING-IN-YAWOF AN AIKPIANX MODEL UNDERSTABILITY DERIVATIVESSTEADY-STATEAND OSCILLATORY CONDITIONSBy M. J. Queijo and Evalyn G. WellsSUMMARYAn experimental investigationhas been made to determine the effectsof vertical fins near the nose of the fusela

4、ge on the directional anddsmping-in-yaw stability derivatives of a swept-wing airplane model. Theinvestigation included measurements of these characteristicsfor the modeloscillating about a vertical axis in a steady airstresn.The results of this investigation showed that, for angles of attackup to a

5、t least 12, fins placed above the fuselage nose decreased thedirectional stabilltybut increased the damping in yaw of the model inboth the steady-state and oscillatory conditionsbecause of the sidewashacting on the tail as welIlas the direct lift of the fins. Also, finsplaced above the fuselage nose

6、 were more effective in increasing thesteady-state or oscillatory damping in yaw than the addition of an equal*amount of area at the vertical tail.Fins pticed below the nose of the fuselage decreased the directionalastability snd increased the damping in yaw to a lesser extent than finsplaced above

7、the fuselage nose in the steady-state conditionbut reducedthe dsmoim in v“awin the oscillator condition. For a constamt valueof diret*ility, the dampin in yawby the use of a fin placed above the nose ofin tail size.INTRODUCTIONcouldbe greatly increasedthe fuselage and sm increaseSome of the present-

8、day high-speed airplanes have shown poor damping*of the lateral oscillation. This situation has led to renewed considera-tion of methods for improving the lateral dsmping. One of the methods 4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NAC!ATN

9、3814under considerationinvolves the use of vortex generators located s$ead .of the verticaltail. T!Iismethod takes advantage of the kg of the side- wash at the vertical tail due to the vortex generator. (See ref. 1, forexsmple.) me investigation in referencel-was concernedth two methods _of varying

10、the sidewash at the vertical tail: varying the wing hefghtsxd using vertical fins with their aerodynamic centers located over theassumed center-of-gravityposition of the airplane model. This fin po8i-tionwas chosen in order to minimize the loss in directional stabilitywhile generating the desired si

11、dewash. . T!hepresent investigationis also concernedtith the use of verticalfins for improving the dsmping in yaw.h this investigation,however,the vertical fins were located ahead of the assuned center-of-gravityposition of the model. Simple geometric considerationsshow that thisfin position should

12、increase the damping in yaw because of the directlift on the fins as well as the sidewash at the vertical tail. Sinceboth of these factors also tend to reduce the directional stability,the vertical-tail size was increased for use with some of the fins inorder to maintain directional stability.Result

13、ssteady-statewere obtained under conditions of steady-stateyawing, and with the mcileloscillatingabout asideslipping,vertical =is.SYMBOLSThe data presented herein are referred to the stability syptem ofsxeswith the origin at the projection of the quarter chord-of-thewingmean aerodynamic chord on the

14、 plane of setry. (See fig. 1.) Thesymbols and coefficientsare defined as follows:b wing span, ftbv vertical-tail span, ftbf vertical-fin span, ftc chord, ftfb/2E mean aerodynamic chord, g, c2dy, fts o:f frequency, cpslF2)F3jF4 designations of vertical fin usedmade in the present investigationto obta

15、in particular values of reduced frequency for model configurationsother than the basic configuration (with VI) on the basis that the purpose P-herein was to determine the effects of adding fins and changing tail size,kProvided by IHSNot for ResaleNo reproduction or networking permitted without licen

16、se from IHS-,-,-NACATN 3814 7both of which chsmge reduced frequency. It should be remembered, there-fore, that comparisons of data on some other basis (for example, all dataobtained at the same reduced frequency) might lead to comparisons andconclusions different from those obtained in the present i

17、nvestigation.All tests were made at a dynamic pressure of 24.9 pounds per sqarefoot, which orresponds ta a Mach number of 0.13 and a Reynolds numberof 0.87 x 106 based on the wing mean aerodynamic chord.Reduction of Test DataThe time required for the smplitude of motion of each model con-figuration

18、to damp to half-amplitude and the perial of the oscillationwere measured from the continuous film record. The measurements weremade at the large amplitudes of motion in order to minimize effects oftunnel turbulence on the model motion. The oscilhtory damping in yawand directional stabilitywere compu

19、ted frcrnthe following eressionsof reference 2:2. 772mz% rju - %,u = - qm2 (awindon-(+i)m doffl %3,UJ +F%r,m= however, the sidewash frcxnthe upper fin also reducesthe vertical-taileffectiveness. Addition of fins both above and belowthe fuselage center line caused a decrease in Cn$ which was very nea

20、rlyequal to the sum of the changes obtainedby adding the upper end lowerfins individually. At high angles of attack (above 20) some of the lowerfins contributeda large positive increment in CnP.Some of the data of.figures 7 to 10 are replotted in figure I-1toshow the relative effects of adding area,

21、to.thevertical tail or as afin near the nose of the fuselage. The desiiltsare given for anglesof attack up to l_2as curves of P p;oted against the arearatio Se/So, which is the ratio of total tail and fin ewosed mea to _the exposed area of vertical tail VI. we dashed line shows the varia-tion in P o

22、btainedby increasing thevertical-tail size. The solidlines show the change in P obtainedby adting fins to the model withthe various vertical tails. These results show, perhaps a Uttle morecle=ly, the decrease in “P caused by the addition of fins near thenose of the fuselage and also show that the_de

23、crease in P with addedfin area becomes greater with increase in angle of attack.Yawing derivatives.- The steady-stateyawing derivatives cyr Clrand Cnr for the various model configurationsare presented in figures12 to 15. Addition of a fin above or below the fuselage center lineincreased the damping

24、in yaw for sngles of-attack up to about 20. Finsabove the fuselage center line caused a greater increase in damping themdid fins of the same size below the fuselage.center line. This is due.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-L.NACA TN 38

25、14to the fact that for yawingthe damping in yaw, and the9flight the sidewash from the fins increasesvertical tail is more directly in the side-wash field of the upper fins than of the lower fins throughout most ofthe angle-of-attackrange tested. At high angles of attack (above20)some of the lower fi

26、ns decreased the damping in yaw of the model.Part of the data of figures E? to 15 are replotted in figure 16 ascurves Of Cnr against the area ratio Se/So. These data show that theaddition of area as a fin caused a greater increase in damping then theaddition of an equal amount of tail area and that

27、the upper fin is muchmore effective in increasing the damping than a lower fin of equal size.Both of these trends increase with angle of attack up to at least 12.The data of figures U end 16 are cross-plottedin figure 17 to showcorrespondingvalues of however,Pfor a given tail a smaller fin is requir

28、ed if it is placed above thefuselage center line than would be required if it were placed belowthe fuselage center line. Also, the damping in yaw of the basic modelcan be greatly increased while the directional stability Cnp is keptconstantby properly adding area at the tail and as a nose fin. Forex

29、ample, at a . 6.4, the value of Cnr of the mael with verticaltail V1 iS -0.56 and Cw iS 0.215. The damping-in-yawparameter Cnrcan be almost doubled while CnPexposed vertical-tail area by 60upper fin having an exposed areais kept constant by increasingthepercent (to obtain V3) and adding anof 15 perc

30、ent of that of tail V1.Oscillatory ResultsSideslip derivatives.- The sideslip derivatives measured during theoscillation tests are presented in figure 18 as curves of P,u + k2C!n,uplotted against the area ratio Se/So. The results are similar to thoseobtained under steady-state conditions (fig. 11) a

31、nd indicate that theterm k2. is small.r,uYawing derivatives.- The yawing derivatives measured during theoscillation tests are presented in figure 19 as curves of the dsmping-in-yaw parameter r,u - B,u) plotted against the area ratio Se/Sofor the various model configurations. The results sre generall

32、y similarto those obtained in the steady-state tests (exceptfor the lower findata) and show that for any particular tail size the addition of a vert-ical fin above the fuselage center line generally increased the dampingin yaw and that the increase was greater than that obtained by adding anProvided

33、 by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10 NACA TN 3814equal area at the vertical tail. Both of these trends increasedwith .increase in angle of attack to a = 120 i%-general, fins aced belowthe fuselage center line decreased the oscillatorydamping in

34、 yaw. -A comparison of figures 16 and 19 shows that the oscillatorydsmpingin yaw was greater thsm the steady-statedamping for all configurations .tested. This may be largely attributableto the effect of the lag of .-the sidewash (discussedin ref. 1) which increases the oscillatorydampingover the ste

35、ady-statedamping by the factor 1 - $ me large osciLlatory damping for the model with vertical fins was caused by the largesidewash generatedby the fins. The increase in oscillatorydamping overthe steady-statedamping for the model with no fins may be associatedwith the dihedral and incidence of the w

36、ing or vortex flow from the fuse-lage.The demping-in-yawparameter Cnr,ti- Cnp,o is plotted against thedirectional.-stabilityparameter P,O + k?CnU a71a9 .032 .030V2 + F2,1 .060 a71 063 a71f%63 .078 .077 .0803 +%,U .m2 .065 .060V3 + %,2 .075 .075 .078V3 + F1,U + %,2 .Wo .061 .058V3 + F2, u a71 C%o .ob

37、7 .037V3+F2,g .068 .Q58 a71W3V3+ F3,U a71W .036 a71 0303 + F3,2 .t% a71c .067V3+ F4,U .d$ a71 027 .0233+ F4, z .062 a71 061 .064v a71082 .082 .4 + %,U a71 o? .0s9 a71 Vo4 + *1,2 .080 .079 .083:1, -.-d- .! J. . JPhotowqh., ,.,of Wel used in the tivestigation. V3,!,.“, ,W3W. 1+ F3,U + F3,1., ,!2IProvi

38、ded by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-L, . ,Iigmmmcm?dmksA$d nwu 352 “Gswp0fa33dw 3PTwmfm 0.6634FV. .wR1 428“G UACA63-010TPNACA 63-012=m-.iFigure 3.- Drawing of model used in the Investigation. All dhnensiomjare h inches.Provided by IHSNot for R

39、esaleNo reproduction or networking permitted without license from IHS-,-,-. NJICATN 3814.-*Oalcul.atadaerodynamiccenter,c.Vertical%8 . cJ % h =,in. Totaltail Expoeedtail )!mxmedtailareaQailarea,aq h area,sfa TotalninareaVI 12.68 18.9010.95lJ.28 1h8 107 .25V2 14015 21.1012.26k.78 184 MO a7135V3 15.50

40、 23.1013.h35.26 221173 .l!ov 16.75 25.00I,4r-m f 1-17-Fin , ill. Ol. 1+ in.z,*. i,ill. TOtU. nn Kxpo88a rln Exposed fina71reaaraa, eq h area, ma TotiluinKareaFl L.59 L.24 3.32 2.306.50 27.0 12.3F2 .0286.CO 10.00 4.70 3.25 $2.033.1 .077F3 ?.26 6.70 11.18 5.263.63 65.0 inued.E-Provided by IHSNot for

41、ResaleNo reproduction or networking permitted without license from IHS-,-,-.NACA TN 3814 270-.0047008-or2Cy -.0f6.020-.024z028-.032.CZJ2.004-.006.0/2.Cw.094c/070/2Angk of offock, CC degFigure 10.- Concluded.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS

42、-,-,-NACA TN 3814.!6- .-+.3,4c%.J.2./o/.0 /.2 /.4AreaaddedatverticaltailAreaaddeda6upperfhAreaaddedasl?r !?AreaaddedequallyasUPWr andOerfin, -Figure 11.- Variation of pas measured1.6 1.8 Z.O ZZ Z4 2.6e/so(a) a= OO.with exposed vertical tail and fin meain steady-statetests.a71a15.Provided by IHSNot f

43、or ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3814 29. - . Areaaddedatverticaltail*AreaaddedasupperfinAreaaddedas bier finAreaaddedequallyasupperad lowerfin/.0 /.2 /.4 /.6 /.8 2.0 2.2 24 2.6Se/S(b) a= 6.Figure XL.- Continued.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-