1、on0-D-Pmn-lNATIONAL ADVISORY COMMITTEE -FOR AERONAUTICSTECHNICAL NOTE 3356EFFECT OF UG OF SIDEWASE ON THE VERTICAL-TAILCONTRIBUTION TO OSCILLATORY DAMPINGIN YAW OF AIRPLANE MODELSBy Lewis R. Fisher and Herman S. FletcherLangley Aeronautical LaboratoryLangley Field,Va.WashingtonJanuary 1955Provided b
2、y IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NMNATIONAL ADVISORY COMMITTEE FOR AERONAUTICSTECKNICAL NOTE 3356I!llilllllilllllllllllliilll;ll0Dbb18dEFFECT OF LAG OF SIDEWASH ON THE VERTICAL-TAILCONTRIBUTION TO OSCILIJYIQRYDAMPINGTN YAW OF
3、AJRPLANE M3DEL3By Lewis R. Fisher and Herman S. FletchersuMMARYTwo models were tested for which the rate of change of sidewashwith angle of sideslip could be varied. For the first mcxiel,this effectwas obtained by mounting auxiliary vertical fins on the fuselage at theassumed center of gravity; for
4、the second mdel, the change in the gra-dient of the sidewash was accomplishedby varying the vertical positionof the wing. In effect, these models permitted a systematic variationof the sidewash gradient at the vertical tailBoth models were tested in steady-yawingflow and by the freely* damped oscill
5、ation-in-yawtechnique to establish the effect of the lagof the sidewash on the unsteady Mteral damping of these models.An analysis indicated that the oscillatory damping in yaw is pro-portional to a factor which depends on the lag of the sidewash whereasthe steady-statedamping is independent of the
6、lag of the sidewash.Secondly, the directional stability is influencedby the static sidewashunder both steady- and oscillatory-flowconditionsbut is not affectedby the kg of the sidewash. The experimental results of this investi-gation verified qualitatively these analytically predicted trends. Nocons
7、istenteffect of frequency on the oscillatory damping in yaw wasevident in the frequency range covered by this investigation.A 45 sweptback-wingmodel at an angle of attack of 16 exhibitedvalues of thecorrespondingin damping isyawing moment%The poorthe other model, hereafter called the swept-wingmodel
8、, hadwing and tail surfaces swept back 45 at the quarter-chord line (seefigs. 3 and 4). Further geometric properties of the wings and verticaltaihi, both straight and swept, are given in the following table:Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS
9、-,-,-RACA TN 3356k7Wings Vertical tails4 thesecalled the low, middle, and high positions.The models with the wings in various vertical positions were alsoconstructed of laminated mahogsmy. The inertia in yaw for the completemodels varied between Iz = 0.44 and = 0.50 slug-ft2 depending onthe configur
10、ationand angle of attack.APPARATUSAll tests were conducted in the 6- by 6-foot test section of thes Langley stability tunnel. The steady-state stability characteristicsof the models were determined from standard force tests wherein themodel was mounted on a single-strut support at the assumed center
11、 ofgravity and the forces and moments recorded for the test conditionsbymeans of a conventioml six-componentbalsmce. The steady-yawingderivatives of the models were obtained by the standard curved-flowtesting procedure employed in the Langley stability tunnel.The apparatus described in reference 5 w
12、as used to measure theoscillatory stability characteristics. The mcdel was mounted on a strutwhich was free to rotate in yaw. The rotation was partly restrained andrestoring moments were provided by means of flexure pivots which supportedthe oscillating strut. A mirror clamped to a section of the st
13、rut whichextended outside the tunnel reflected a beam of light into an opticalrecorder. A continuous record of the motion of the model, after aninitial displacement in yaw, was obtained cm film. A timer in therecorder simultaneouslyexposed timing lines on the film in order thattime, as well as model
14、 displacement, could be read. Variation of theperiod of oscillation for the wing-height models was accomplished byclamping weights to the oscillation strut outside the tunnel and therebyvarying the yawing moment of inertia of the oscillating system. Thisd procedure is fully described in reference 5.
15、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8 lIACATN 3356TESTS 4Force TestsLThe model with auxiliary fins was tested without a wing and at anangle OY attack of 0 through the range of static sideslip angles of20 for the fuselage alone, the fusela
16、ge with each of the verticaltails V1 and V2, and the fuselage and each of the vertical tails incombinationwith each of the auxiliary fins Fl, F2, and F5. Thestatic sideslippingderivativeswere derived from these data by measuring the variations of the rolling-moment,yawing-moment,and lateral-forcecoe
17、fficients through = 15. Because the sideslippingderivatives smdthe sidewashproperties of the models with varying wing position wereatieady avaihble in reference 4, these mdels were not tested again.The steady-yawingderivativesfor all models were measured by meansof the standard stability-tunnelcurve
18、d-flowtechnique. Tunnel-wallcurvatureswere employed to correspondwith values of the yawing-velocityparameter b of O, -0.0512,5 -0.0660,and -0.0868 for these models.Oscillation Test8The oscillation tests of the models with auxiliary fins were madein order to determine whether an effect of sidewash on
19、 the unsteadylateral damping of a model could be detected. These tests consisted ofdeflecting the model several degrees in yaw and then releasing it. Theresulting oscillatoryyawing motion of the model was allowed to damp toless than one-half its original amplitude. These tests were made, atabout the
20、 same frequency of oscillation,for the fuselage and the largervertical tail V2 and the fuselage and V2 in combinationwith each ofthe auxiliary fins Fl, F2, and F3. The period of oscillation forthese tests was about 1.5 secondswhich corresponds to a value of thereduced frequency of k = 0.0045.The osc
21、illation tests of the models with varying wing position weresomewhatmore elaborate tests and were similar to those of reference 5.ese models were tested at fou frequencies of oscillation covering therange of reduced frequencies from k = 0.002 to k = 0.020. Thestraight-wingmodel was tested for angles
22、 of attack of 0 and 8, andthe swept-wingmodel for angles of attack of 0 and 160. The higherangles of attack are well below the stall for each model. (See ref. 4.)The wings of the mdels were tested in the low, middle, and high posi-tions in order to vary the sidewash characteristics,and the approxima
23、te rtail incrementsto the stability derivativeswere obtainedby testingthe tail-on and the tail-off configurations. rProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-9k Test ConditionsThe tunnel conditionsfor all tests are tabulatedbelow:d rK, F1 being
24、 the smallest fin and F3 the largest.l?romthese data, the vertical-tail contribution to the yawing-momentcoefficientwas determined and is shown in figure 9 for both the auxiliary-fins-off and the auxiliary-fins-on configurations. The yawing-moment.increment due tc the interference of the auxiliary f
25、ins corresponds to anadditional angle of attack at the vertical tail which is termed the side-the _.difference between the steady and oscillatory data for both the tail-off and the tail-on damping which is the oscillatorywing contributiondiscussed previously in this paper. The second difference is t
26、he lagof the sidewash effect which appears during oscillationbecause ofthe presence of sidewash due to . The same trend took place to asmaller extent for u = OO. The curves, shown as calculated in figure 18,were obtainedby measuring the differencebetween the tail-on and tail-offcurved-flowdamping, m
27、ultiplying this differenceby appropriate valuesaoof 1 - ,a and adding these tail contributionsto the oscillatory tail-off -values. The trends appear to be about the same as those for the experi-mental tail-on oscillationdata. “Figure 19 is a similar figure for the directional stability. Thedecrease
28、in directional stabilitywhich takes place when the wing is movedfrom the low to the high position is about the same during steady andoscillation testing. The calculated curves, for this figure, were estab-lishedby estimating a value of CyB from reference 10, and multiplyingthe value obtainedby the a
29、ppropriate tail-length factors and measuredvalues of 1+ tail off.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.4-.4Figure 7.-with.020:02.08.040:04:08, ! , , , 1 I , I20 16 /2 -8 -4 0 4 8 /2 /6 20- degStatic sideslipingdata for mcdel with auxiliary
30、 fins. Fuselageeach auxiliary fin in ccmibinationwith small vertical tail.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3356 27.4.20-.4.020:02.08.040:04:0820 16 /2 8 4 O 4 8 12 K 20-p, O&gFigure 8.- Static sideslipping data for model with a
31、uxilisry fins. Fuselaewith each auxiliary fir-in combinationwith large verical tail. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-28 NACA TN 3356- .$,finon (&J, fm Off,08 8.W 4q-0 0-.04 .4.08 -8-20 -10 0 10 20-B.08.040-.04708840-0-4-8-20 -10 0 10
32、20-A.08 8.04 4pn o 0:04 -4-.m -8-20 -10 0 20-B.08 8.04 4offhi 0+x -4708 -8-20 -lo 0 10 20-/.08046)0-.04.0884or-4-8-20 -lo 0 0 20-B08 8,04 4or(cd 0-.04 -4-.08 -8-20 -10 0 10 20-B(a) Small vertical tail, VI. (b) Large vertical tail, V2.Figure 90- The effect of sideslip angle on the vertical-tail incre
33、mentsto the yawing-moment coefficientresulting from the auxiliszy finsand on the sidewash due to the auxiliary fins.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3356.4.20o /AF2 3Figure 10.- T!neeffect of aspect ratio of auxiliary fin on the rate ofchange of sidewashwith amgle of sideslip.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
