NASA NACA-TN-2534-1951 Experimental investigation of the low-speed static and yawing stability characteristics of a 45 degrees sweptback high-wing configuration with various twin v.pdf

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1、TECHNICAL NOTE 2534EXPERIMENTAL INVESTIGATION OF THE W-SPEED STATIC ANDYAWING STABJ311W CHARACTERX3TICS OF A 45 SWEPTBACKGH-WING CONFIGURATION WITH VARIOUSTWIN VERTICAL WING FINSBy Alex Goodman and Walter D. WolhartLangley Aeronautical IahatoryIangley Field, Va.WashingtonNovember 1951Provided by IHS

2、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBWY KAFB,NMInlllnnlllnlollllu00b54713NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS1TECHNICAL NOTE 2534IWZKH4ENTAL INKESTIGATIONOF THE LOW-SPEED STATIC ANDYAWING STABILITY CHARACTERISTICSOF A 45 SWEPTBACKHIGH-WING

3、 CONFIGURATIONWITH VARIOUSTWIN VERTICAL WING FINSBy Alex Goodman and Walter D. WolhartH3vvflf2and abbreviations:wing positionsfuselagehorizontal-tailpositionsvertical tailrear vertical fin (see fig. 2)basic fin (see fig. 2)modified fin (see fig. 2)APPARATUS AND MODELSThe tests of the present investi

4、gationwere conducted in the 6- byThe fuselagewas a body of revolution (finenessratio of 6.90)having a circular-arcprofile with a blunt tail end. The wing andhorizontal tail had an aspect ratio of 4.0, a taper ratio of 0.6, and anNACA 65AO08 profile in sectionsparallel to the plane of symmetry. Thequ

5、arter-chordlines were swept back 45. Ordinates for the NACA 65AO08airfoil section and for the fuselage are given in tables II and III,respectively. The twin lower-surfacefins tested fl and f2 hadaspect ratios of 1.2 and 1.7, respectively. These fins had flat-plateprofiles with round leading edges an

6、d beveled trailing edges. The smallrear vertical fin v was triangular in plan form and had an aspect ratioof 0.84.The model was mounted on a sie strut at the origin of the axesshown in figure2. Forces and moments were measured by means of aProvided by IHSNot for ResaleNo reproduction or networking p

7、ermitted without license from IHS-,-,-6 NACA TN 2534six-componentbslance system. Photographs of two of the model configu-rations tested sre presented as figure 3. 4Ql lifting surfaceswereset at 0 incidence with respect to the fuselage center lines. .The tests in straight flowTESTSwere made at a dyns

8、mic pressure Of39.8 pounds per square Foot which correspondsto-a Mach-number of about0.17 and a Reynolds number of 0.88 x 106 based on the mean aerodynamicchord of the wing. In yawing flow, the tests were made at a dynamicpressure of 24.9 pounds per square foot which correspondsto a Machnumber of ab

9、out 0.13 and a Reynolds number of 0.71 x 106 based on themean aerodynamic chord of the wing.In straight flow, the static longitudinal and lateral stabilitycharacteristicswere obtained from tests of the model at angles of yawof Oo and *5. The yawing stabilim characteristicswere obtained fromtests of

10、the model at values of rb/2V of O, -0.0311, -0.0660,”and-0.0870.The angle-of-attackrange for alJ tests was from about -2 up toabout 300.CORRECTIONSApproximate corrections,based on unswept-wing theory, for theeffects of jet boundaries have been applied to the angle of attack(reference k). The data ha

11、ve also been corrected for the effects ofblocking (reference5). Corrections for the effects of support-strutinterference have not been applied since the forces obtained for asimilarmodel in reference 2 were found to be small.The lateral forceof the static-pressuredue to yawing has been corrected for

12、 the effectsgradient associatedwith curved flow.RESULTS AND DISCUSSIONPresentation of Results and General Remarks.Some of the results illustratingthe static-stabilitydifficultiesdiscussed in the introductionare given in figure 4 and were taken fromreference 2.- .Provided by IHSNot for ResaleNo repro

13、duction or networking permitted without license from IHS-,-,-RACA TN 2534 7As indicated.in figure 4, a 45 sweptback low-wing, high-horizontal-tail configuration(W3 + F +V + , in fig. 2) has an unstable variation at moderate angles of attack because the horizontal tail is ina strong downwash field (s

14、ee references 1 and 2). This configuration,however, has good directional stabil-ithroughout the e-of-attackrange because of the favorable sidewash at the vertical tail causedbythe wing-fuselage interference. (See references 2 and 3.) On the otherhand, a 45 sweptback high-wing, low-horizontal-tailcon

15、figuration(W2 + F + V + HI, .infig. 2) has good longitudinal stability characteristicsbecause the horizontal tail is below the wing wake for most of the angle-of-attackrange. This configuration,however,becomes directionallyunstable at moderate and high angles of attack because of an unfavorablesidew

16、ash at the v=tical tail (references2 and 3).A high-wing, low-horizontal-tail.arrangementwhich is desirable forlongitudinal stabilitymakes possible the repositioning of the verticalfin area from the rear of the fuselage to a region of less adverse side-wash; namely, the surface of the wing. The prese

17、nt investigationwas,therefore, tie to determine the static-stabili and yawing-stabilityderivativesof a 45 sweptbackhigh-wing, low-horizontal-tailmodel withvertical fins located on the wing.The data obtained during the present investigationare given ascurves of the static longitudinal and lateral sta

18、bili characteristics(figs. 5 to 7) and yawing chmacteristics (fig. 8) plotted against angleof attack for the model with various fin arrangements.Static Stability CharacteristicsBasic configurationswithout vertical fins.- For practical consider-ation, the 45 sweptback high-wing, low-horizontal-tailco

19、nfigurationW2+F+V+H1 of reference 2 was modified so that the horizontal tailwas located above the hypothetical jet sxis but stillbelow the wingchord plane. This resulted in the basic co,pfigurationW2 + F +H3 ofthe present paper. (See fig. 2.) However, the basic configurationW2+F+H3 was ,stilllongitu

20、dinallystable throughoutthe angle-of-attack range (figs. 4 and 5) as might be expcted from the relativeposition of the wing and horizontal tail (references1 and 2).As pointed out in references 2 and 3, a m-tiw coiationwill have a positive effective dihedral CZY at 0 angle of attackbecause of the win

21、g-fuselage interference. A plqwical picture indicatingthe cause of this effect is presented in figure g(a). The directionalY. _ . . . .-. . . .- - -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,- . .0 NACA TN 2534instabili of the basic configuration

22、 positive( cn) is attributableto the unstable yawing moment associatedwith fuselages (reference6).Basic configurationwith twin lower-surfacefins.-”Thetwin verticalfins fl were tested on the lower sur$ace of the wing at 0.70b/2and 0.98b/2. The addition of the twin lower-surfacefins to the basicconfig

23、urationat either stationhad no appreciableeffect on the longi-tudinal characteristics(fig. 5). The main effect of adding the twinlower-surfacefins at either stationwas to make the”complete configu-ration W2 + F + H3 + fl directionallystable throughout the angle-of-attack range. The fins at 0.98b/2 c

24、ontributed a larger stabilizingincrement in CnW than did the inboard fins at ().7()b/2because of thelonger tail length (fig. 2). The contributionof the twin lower-surfacefin configurationsto the dlrtional stabilityparameter cn was smallat low angles of attack in comparisonwith the contributionof the

25、 single-vertical-tail configurationof reference 2. (Compsrefigs. 4 and 5.)However, cn for the high-wing, single-vertical-tailconfigurationofreference 2 reversed sign (the configurationbecame directionallyunstable) at moderate angles of attack; whereas, the twin lower-surfacefin configurationwas tiec

26、tionally stable throughout the angle-of-attackrange. .The spanwiseposition of the twin lower-surfacefins had a markedeffe”cton the effective-dihedralparameter c2 at 0 angle of attack.With the twh lower-surfacefins located at 0.Ob/2, the antisymmetricloading induced on the wing at 0 angle of attack i

27、ncreased the effectivedihedral. As the fins were moved outboard, the antisymmetricloafinginducedby the twin lower-surfacefins on the wing reduced the positiveeffective dihedral. With the fins located at 0.98b/2, the inducedloading apparentlywas large enough to cancel the positive effectivedihedral c

28、ausedby wing-fuselage interference (fig. 5). A representationis given in figure g(b) of the spanwise load distributionover the wingas affectedby the wing-fuselage interferenceand the wing-fin interference.Although considerationof figure g(b) till not indicatewhether theincrement in CZ causedby addit

29、ion of the twin luwer-surfacefinswill be positive or negative for all -spanwisepositions of the fins, itdoes indicate the direction in which CZV will change with a changein spanwiseposition of the fins.Basic configurationwith twin upper-surfacefins.- The twin lower-surface fiq configurationswere tie

30、ctionally stable throughouttheangle:of-attackrange but to a lesser degree at low angles of attackthan the single-vertical-tailconfigurationof reference 2. Since - - - . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NACA TN 2534 9the 0.70b/2 loca

31、tion of the twin lower-surfacefins appeared to bereasonable from structural considerations,an attempt was made to improvethe stabili of this configurationby adding a small amount of fin areaabove the wing surface to form fin f2. Only a small improvementwasobtained in the directional stabili (figs. 5

32、 and 6). None of theother parameters were affected appreciably except for a small increasein longitudinal stabili at moderate angles of attack,The twin uer-surface fin configuration W2 + F + H3 + fl at 0.70b/2also had good longitudinal stability throughoutthe angle-of-attackrange (fig. 6). The longi

33、tudinal stabili for the moderate angle-of-(attack range was better more negative C%) than had been obtained withthe other twin-fin arrangementstested. This increase in longitudinalstabili may be athibuted to the fact that the twin upper-surface finsmight have delayed the normal inboard movement of t

34、he wing-tip vorticeswith an increase in angle of attack. This delay in the inboard movementof the wing-tip vortices would have caused the horizontal tail toorate in a less unfavorable downwash field.The twin upper-surface fin configurationwas directionally stable(negative Cn throughout the angle-of-

35、attackrange. The variationJOf Cn with angle of attack was nearly constant for this configuration.At 0 angle of attack, a more negative value of Cnti was obtained withthe upper-surfacekin configurationthan was obtaindwith the lower.surface fin configuration (comparefigs. 5 and 6). This negativeincrea

36、se in CnV can be accounted for by considering the effects onthe fins of th”induced antisymmetric loading on the wing causedby thewing-fuselage interference. For a high-wing configuration,the inducedloading would tend to increase the contribution of the upper-surfacefins and to produce an equal and o

37、pposite effect on the lower-surfacefins. The representationof the induced loadings presented infigure 9(b) indicates such an effect. At moderate angles of attack,the upper-surfacefins were approximately50 percent as effective asthe lower-surfacefins. At high angles of attack Cn$, for the upper-mrfac

38、e fins, became less negative as the angle of attack was increased.The value of the effective dihetial parameter CZti at a = 0,obtained with the upper-surface fins, Twas approximatelythe same asthat obtained with the lower-surface fins (figs. 5 and 6). Considerationof the loads acting on the wing (fi

39、g. 9(b) indicates that, since theaddition of lower-surface fins at 0.70b/2 made Czllrmore positive(fig. 5), the addition of upper-surface fins at th same spanwise stationshould make CZV less positive, relative to the CZV of the basicconfiguration W2 + F + H3. This apparent contradictionof the data c

40、an_ . . -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10beasNACA TN 2534explainedby accounting for the effects of the loading on the finswell.as the loading on the wing. The load on the lower-surface finsproduced little rolli”moment since the cent

41、er of presswe of the loadwas approximatelyin the plane of the roll axis. The load on the upper-surface fins, however, produced a positive rolling moment (for positiveangles of yaw) since the center of pressure of the load was above theroll axis.The effective dihedral CZV was positive throughout the

42、angle-of-attack range for the twin upper-surface fin configuration. The factthat clv generally changes sign is attributedto the stalling of thewing tips. The fact that for this case CZV did not change sign mighthave been due to the delay of the stall inboard of the fins, or possiblyto the fact that

43、the increment in positive %$ produced by the loadon the fins was lsrge enough to compensate for the effects of wing-tipstall.Basic configurationwith wing fins and small fuselage fin.- A studyof the directional stability characteristicsof the model with twin fins .generally showed low directional sta

44、bility at low angles of attack but.reasonably high stability at moderate and high angles of attack. Thehigh-wing, single-vertical-tailconfigurationof reference 2 had a largeamount of directional stabili at low angles of attack but was unstableat moderate angles of attack (fig. 4). It appeared, there

45、fore, that acombination of the best features of each type of fin arrangementwouldbe desirable. Several conibinationsof twin vertical wing fins and asmall vertical-fin on the fuselage therefore were tested on the basicconfiguration,and the results are shown in figure 7. A comparisonofthese results wi

46、th those of figures 5 and 6 indicates that the additionof the small fuselage fin produced a small increase in directionalstabili at low angles of attack and a small decrease in directionalstability at the high angles of attack. This decrease in directionalstabili at high angles of attack may be attr

47、ibuted to the unfavorablesidewash at the smalJ fuselage fin.parameters were affected appreciablylage fin.Yawing StabiliNone of the other aerodynamicby the addition of the small fuse-CharacteristicsBasic configurationwithout vertical fins.- The basic configurationw+F+H3 had very little damping in yaw

48、 negative Cnr as shown in( )figure 8. - Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 2534 II-.The negative value of Czr obtained at a = 0 can be accountedfor by studyi4MaxM.: The Aerodynamic Forces on Airship Hulls. NACARep. 18k,a71. .- - . . -z . . .-. -. _ . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-14. -.-NACA TN 234.TABI.EI.- GEOMETRICCHARACI!HRISTICSOFMODEL.Fuselage:Length,in.