1、NASA TECHNICAL NOTE h m d T n z I- 4 u9 4 z NA _- SA TN D-34L7 - _- - LO K 1.A N A lRTl COPY FVJL AND INVESTIGATION OF A SEMISPAN DETERMINE GROUND EFFECT ON YAW CONTROL IN HOVERING TILT-WING VTOL MODEL TO FULL-SPAN FLAPS USED FOR by Kalman J. Grnnwald Langley Research Center Langley Station, Hampton
2、, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM I lllllllllll 1 Ill yylplllllllll 013015b NASA TN D-3437 INVESTIGATION OF A SEMISPAN TILT-WING VTOL MODEL TO DETERMI
3、NE GROUND EFFECT ON FULL-SPAN FLAPS USED FOR YAW CONTROL IN HOVERING By Kalman J. Grunwald Langley Research Center Langley Station, Hamptun, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION -. For sale by the Clearinghouse for Federal Scientific and Technical Information Springfield, Virginia 22151
4、 - Price $3.00 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INVESTIGATION OF A SEMISPAN TlLT-WING VTOL MODEL TO DETERMINE GROUND EFFECT ON FULL-SPAN FLAPS USED FOR YAW CONTROL IN HOVERING By Kalman J. Grunwald Langley Research Center SUMMARY A hov
5、ering force-test investigation on a semispan tilt-wing VTOL model was con- ducted to determine the ground effect on plain, single-slotted, and double-slotted full-span flaps used differentially as ailerons for yaw control. Although yawing effectiveness losses were experienced with all flap configura
6、tions near the ground, the slotted-flap configura- tions were considerably more effective in ground effect than the plain-flap configuration. INTRODUCTION Most of the present-generation propeller-driven tilt-wing VTOL aircraft are designed to use full-span flaps for the purpose of reducing the maxim
7、um wing-tilt angle required during transition and for providing greater efficiency (less power required) in the STOL mode. In the hovering mode with the wing effectively tilted 90 to the ground and the pro- peller wash blowing over the flaps, the flaps could be used to provide needed yaw control if
8、deflected differentially as ailerons. The hovering yaw control out of ground effect pro- duced in this manner can generally be estimated from the propeller thrust and the amount of turning effectiveness expected from the flaps. However, as the ground is approached, yawing effectiveness decreases. Th
9、is loss in effectiveness has been detected and meas- ured in other wind-tunnel tests (refs. 1 and 2) and in flight work on the VZ-2 aircraft (ref. 3). However, no detailed investigation indicating the most desirable flap configura- tion has been made. The purpose of the present static-force-test inv
10、estigation is to study this loss in In particular, this investigation covers the effects of flap-chord-to-propeller- yawing effectiveness as the ground is approached with a semispan, powered tilt-wing flap model. diameter ratio and the flap configuration - specifically the possible advantages of slo
11、tted flaps over plain flaps. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SYMBOLS A three-view drawing of the model indicating the positive sense of forces, moments, and angles as well as the center-of-moment location is presented in figure 1. Mea
12、surements for this investigation were made in the U.S. Customary System of Units. Equivalent values are indicated herein in the International System (SI) in the interest of promoting the use of this system in future NASA reports. AP b b ba ba E Cf D FL FX h MX MY MZ aMZ /Tb a6fo 2 propeller disk are
13、a, sq ft (m2) wing semispan, b/2, ft (m) wing full span, ft (m) aileron semispan, bJ2, ft (m) aileron full span, ft (m) wing mean aerodynamic chord, ft (m) flap chord, ft (m) propeller diameter, ft (m) lift force, lb (N) longitudinal force, lb (N) height of model above ground (measured from trailing
14、 edge of flap at sf = OO), ft (m) root bending moment (roll plane, fig. l), ft-lb (N-m) pitching moment (fig. l), ft-lb (N-m) root bending moment (yaw plane, fig. l), ft-lb (N-m) ratio of slope of bending-moment curve to flap-deflection curves, taken through Oo from *2O0, ft-lb N-m deg (deA Provided
15、 by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I qS local slipstream dynamic pressure, lb/sq ft (N/m2) R radius, in. (m) T semispan thrust, T/2, lb (N) T full-span thrust, lb (N) X,Y ,z distance along principal axes, ft (m) x/E,Yl/ CYU/E * 6f 6f flap deflec
16、tion, deg wing and flap ordinates in percent M.A.C. incremental flap deflection, deg flap deflection at 0 taken from *2O0, deg 6fO 6, vane deflection, deg 0 turning angle, deg Subsc ript s : max maximum U upper I? lower MODEL AND EQUIPMENT Photographs of the model are shown in figures 2 and 3. Figur
17、e 4 is a three-view drawing of the model with pertinent dimensions shown. NACA 4415 airfoil section (which was used previously in ref. 4). The wing consisted of a steel spar with a wood covering and had a detachable rear section into which various types of flaps could be mounted. The basic wing empl
18、oyed an The three plain-flap configurations are presented in 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-figure 5 (a 15-percent-chord flap, a 25-percent-chord flap, and a 37.5-percent-chord flap). The flaps were constructed to deflect through a
19、 range of angles from 70 to -70 in increments of loo. The 40-percent-chord single-slotted-flap configuration is pre- sented in figure 6. This configuration was tested with full-span flaps and with “cutouts“ to simulate possible engine nacelle locations. The nacelle cutouts were 4 inches (10.2 cm) wi
20、de and were located directly behind the existing model nacelles. these configurations the flaps could be deflected 60 to -60 in increments of loo. two double-slotted-flap configurations are shown in figure 7. The smaller double- slotted flap employed a 14-percent-chord vane and a 22-percent-chord fl
21、ap. The larger flap used the same 14-percent-chord vane and a 44-percent-chord flap. Each of these flap systems could be varied through a range of angles from 60 to -6OO in increments of 100. In both The In order to provide symmetry, the model was mounted on a reflection plane as shown in figures 1
22、and 2. The 2-foot-diameter (0.61-m) fiber-glass propellers were located in the same position with respect to the model throughout the tests. A 7- by 12-foot (2.14-m x 3.66-m) wood groundboard, as shown in figure 2, was placed behind the model to simulate the ground. The board could be moved to any d
23、esired height or removed to simulate the out-of -ground-effect condition. The distance from the model to the wall was 16 feet (4.88 m) (h/D = 8). The test room was large enough to allow the air to be considered free air; therefore, h/D = 00 was used for the test condition. Flow surveys were made by
24、the use of a tuft grid located on the center line of the A camera mounted on the ceiling of the room photographed outboard propeller (fig. 2). the tuft grid. The tuft grid consisted of 2-inch (5.08-cm) long tufts 3 inches (7.62 cm) apart. The grid was 8 feet (2.4 m) wide and each wire spacing in the
25、 aft direction was 3 inches (7.62 cm). Wires were removed as the groundboard was moved closer to the wing. Slipstream dynamic-pressure measurements were made at several spanwise sta- tions at locations above and below the wing surface by the use of the pressure rake as pictured in figure 8. floor-mo
26、unted strain-gage balance. The propeller loads were measured from strain gages mounted in the engine nacelles. All the force data were recorded on strip-chart recorders. Force measurements taken from the wing were determined from a TESTS The test procedure used was to vary the flap deflection throug
27、h its complete range of deflections with the groundboard at a fixed position. When a complete range of flap deflections was tested, the groundboard was moved to another position. 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-The three plain-flap
28、configurations were tested at ratios of groundboard height to propeller diameter h/D of 00, 3.00, 2.50, 2.00, 1.50, 1.00, 0.75, 0.50, 0.38, and 0.25. The propellers operated at a near-constant rotatational speed of 6000 rpm. The propeller rotation for the three plain-flap configurations was to the l
29、eft as viewed from behind the model. The single- and double-slotted-flap configurations were tested at ratios of ground- board height to propeller diameter of 03, 1.75, 1.25, 1.00, 0.75, 0.50, 0.375, and 0.25. Rotational speed was set constant at 6000 rpm. However, the propeller rotation was opposit
30、e of that tested for the plain flaps; that is - rotation was to the right as viewed from behind the model. of rotation. Previous work has indicated that the direction of rotation appears to have only negligible effects on slipstream turning in the hovering mode. The propeller available at the time o
31、f the tests dictated the mode During the tests the tuft grid described in the preceding section was photographed at each height and flap deflection in order to record the airflow at each condition as the model was moved toward the ground. rake at different span locations of the plain wing in the und
32、eflected condition. were also made at a number of ground heights. Tests were also conducted with the total-pressure These tests PRESENTATION OF FESULTS Each figure presenting the basic force data is plotted in parts (a) and (b), in a man- Parts (a) present the ratio of lift force to ner similar to t
33、hat used in past investigations. thrust, the turning effectiveness, the turning angle, and the ratio of pitching moment to thrust times propeller diameter. axis. All basic data are presented as a function of flap deflection with the exception of turning effectiveness. Parts (b) present the moments a
34、bout the roll and yaw The following table is presented for the convenience of the reader: Figure Basic force and moment data: 15-percent-chord plain flap - h/D = 03 to 1.00 . 9 h/D = 0.75 to 0.25. . 10 h/D = 00 to 1.00 . 11 h/D = 0.75 to 0.25. . 12 h/D = 00 to 1.00 13 h/D = 0.75 to 0.25. 14 25-perce
35、nt-chord plain flap - 37.5-percent-chord plain flap - 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figure 40-percent-chord single-slotted flaps . h/D = co to 1.00 15 h/D . 0.75 to 0.25. 16 h/D= co to 1.00 17 h/D . 0.75 to 0.25. 18 h/D=mto1.00 19
36、 h/D . 0.75 to 0.25. 20 h/D = 00 to 1.00 21 h/D = 0.75 to 0.25. 22 40-percent-chord single-slotted flaps (with nacelle cutouts) - 14-percent-chord vane, 22-percent-chord double-slotted flaps - 14-percent-chord vane. 44-percent-chord double-slotted flaps - Analysis : Comparison of turning effectivene
37、ss (ref . 5) 23 Effect of flap-chord length on control moment and FL/T (plainflaps), h/D= co 24 Effect of configuration on control moment, h/D . 03 . 25 Comparison of total control moment for each configuration. h/D . 00 26 Control moment in ground effect. h/D = 0.25, for - Plainflaps 27 All configu
38、rations . 28 29 Ground effect losses for each configuration, q/D = 0.22 . Hovering control effectiveness - . g: All configurations cflD”0.22 32 cf/D=Range; h/D=m 34 Effect of nacelle cutouts on control moment 33 Hovering control effectiveness compared with other investigations - h/D=Range 35 Tuft su
39、rveys: 40-percent-chord single- slotted flap (nacelle cutouts) - 14-percent-chord vane. 44-percent-chord double-slotted flap - h/D . 1.75 to 0.25; sf . Range 36 h/D = 03 to 0.25; sf and 6v . Range . 37 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-
40、,-Figure Pressure surveys, above and below plain flap at 74-percent chord: h/D = 00 to 0.25; = 0.236 to 0.672 . 38 b/2 h/D = - and 0.25; = 0.236 to 0.672 39 Isometric projection: h/D = 03 and 0.25; = 0.236 to 0.672 40 b/2 b/2 Schematic representation of flow field . 41 DISCUSSION Ground Effect on Ba
41、sic Data The basic force and moment data for each configuration are presented in two parts. The first part represents conditions of ground height ranging from out of ground effect h/D = 00 to 1 propeller diameter above the ground h/D = 1.0. (See figs. 9, 11, 13, 15, 17, 19, and 21.) occur with chang
42、e in ground height when compared with out-of -ground-eff ect conditions. However, observations of the data in the second part of the figures for each configuration at the lower ground heights h/D = 0.75 to 0.25 increasingly larger changes in the aerodynamic forces and moments when compared with the
43、out-of -ground-eff ect condition. In this height range only small changes in any of the forces and moments (figs. 10, 12, 14, 16, 18, and 20) show Control Effectiveness Out of Ground Effect Slipstream-deflection characteristics. - Differential deflection of the ailerons on a ._ - _ - - - . tilt-wing
44、 configuration in hovering produces a yawing moment by the action of the ailerons in deflecting the slipstream, forward on one wing and rearward on the other. slipstream-deflection characteristics of the flap systems (used as ailerons) used in the present investigation are compared with the results
45、of previous investigations (as summa- rized in ref. 5) in figure 23. The Effect of aileron chord and type.- The effects of aileron chord and a comparison of plain and slotted ailerons are presented in figures 24 and 25, respectively. the chord of plain ailerons increases their effectiveness in produ
46、cing yawing moments as would be expected (fig. 24). The use of slotted flaps as ailerons (fig. 25) greatly increases the yawing moment that can be attained at the larger positive deflections (20 to 60 and above). Moreover, the lift loss, at moment values that can be achieved by both plain and slotte
47、d ailerons, is significantly lower for the slotted configurations. These improve- ments in control effectiveness and reduction in lift loss at positive deflections are due to the flow through the slots delaying flow separation on the aileron. At negative deflection, -. . Increasing 7 Provided by IHS
48、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-.- 3j however, the slotted ailerons are less effective than the plain ailerons because of the poor undersurface contour at negative deflections (trailing edge up). As a result, the total con- trol moment that would be
49、 produced on a complete configuration is only slightly greater than that for plain ailerons (fig. 26). Available flap sections were used for the slotted ailerons in this investigation. It is possible that some improvement in effectiveness at negative deflection could be achieved by altering the lower surface contour
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