1、00cl-NATIONALADVISORYCOMMITTEE :FOR AERONAUTICSTECHNICALNOTE3364INVESTIGATION OF EFFECTIVENESS OF LARGE -CHORD SLOTTEDFLAPS IN DEFLECTING PROPER SLIPSTREAMS DOWNWARDFOR VERTICAL TAKE -OFF AND LOW-SPEED FLIGHTBy Richard E. Kuhn and John W. DraperLmgley Aeronautical LaboratoryLangley Field, VaWashingt
2、onJanuary 1955Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECH LIBRARY KAFB, NMNATIONAL ADVISORY C041TTEE Illllllllillllllllllilllillllllli=FOR AERONA IIClL5+i TECHNICAL NOTE 3364INVESTIGATION OF EFFECTIVENESS OF LARGE-CHORD SLOTTEDFIATS IN DEFLE
3、CTING PROPELLER SLIPSTREAMS MWNWARI!FOR VERTICAL TAKE-OFF AND LOW-SPEED FLIGHTBy Richard E. Kuhn and John W. DraperSUMMARYAn investigation of the effectivenesschord slotted flaps in rotating the thrustof a wing equipped with large-vector of propellers throughthe angles required for vertical take-off
4、 and for flight at very low speedshas been conducted in the facilities of the Langley 300 MPH 7- by 10-foottunnel.Under conditions of static thrust and with zero incidencebetween thethrust axis and the wing chord plane, the slotted flaps were effective inrotating the thrust vector upward about 63 wi
5、th a loss of ,slightlylessthan 10 percent of the thrust. When an auxiliary vane was added above thewing, the thrust vector was rotated upward 74 with a loss of only about10 percent of the thrust. With this vane configuration,vertical take-offcould be achieved with an initial attitude of 16 and at ai
6、rplane weightsup to 90 percent of the total propeller thrust. The addition of 10 inci-dence between the thrust axis and the wing increased the upward rotationof the thrust vector about 10. For the same turning angle, the divingmoments associated with the slotted-flap configurationswere approximately
7、twice as large as the diving moments of the configurationswith plainflaps md two auxiliary vanes.INTRODUCTIONThe practical utilization of the helicopter has indicated the useful-ness of aircraft that are capable of operating from very small bases. Theadvantages to be gained with an airplane that inc
8、orporatesboth the small-field capabilities of the helicopter and the high-speed potential of con-ventional airplanes are readily apparent. One possible means of achievingthese advantages would be to provide an engine-propeller combination thatis capable of providing static thrust in excess of the gr
9、oss weight. Thelift for vertical take-off could then be obtained by deflecthg the pro-peller slipstreams downward by means of wing flaps or both flaps and vanes.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NACA TN 3364Results of flight tests of
10、a model that utilized a cascade of wings to kdeflect downward the slipstreams of relatively large-dimnder propellersas a means of achieving vertical take-off are reported in reference 1;however, this configurationwas designed solely to demonstrate the feasi- fbility of this approach and to study the
11、 stabilityand control problemsin hovering and in vertical take-off and landing. No provision was madefor forward speed.A number of wing configwations that may be capable of deflecting theslipstream sufficientlyto make vertical take-off possible and that canalso be converted to conventionalmonoplane
12、wings for cruising flight arebeing investigatedat the Langley Aeronautical Laboratory. An illustrationof a take-off maneuver that would be possible withthis type of aircraftis presented as figure 1.The data of reference 2 indicate that a configurationhaving large-chord plain flaps and two auxiliary
13、vanes may possibly perform the neces-sary aerodynamic functions; however, the process of retracting and storingthe two auxiliary”v=es for conversionto a monoplane wing may involve seriousmechanical problems.The present investigationof the use of large-chord slotted flaps was qundertaken in an attemp
14、t to develop a configurationfor deflecting the pro-peller slipstreamthrough the large turning angles required for verticaltake-off without resorting to the use of auxiliary vanes or, at least, toprovide adequate slipstreamdeflection with a simpler vane configuration.SYMBOLSWhen a wing is located in
15、the slipstream of a propeller, large forcesand moments can be produced even though the free-stream velocity decreasesto zero. For this condition, coefficientsbased on the free-stresm dynamicpressure approach infinity and become meaningless. It appears appropriate,therefore, to base the coefficients
16、on the dynamic pressure in the slip-stream. The coefficientsbased on this dynamic pres6ure are indicated inthe present paper by the use of a double prime. The relationsbetween thethrust and the dynsmic pressure and velocity in the slipstreamhave beenderived in reference 2.The positive sense of the f
17、orces, moments, and angles determined forthe static-thrusttests is shown in figure 2. For the tests with foardspeed, the usual conventionfor forces was used; that is, the lift andlongitudinalforce were taken perpendicular and parallel, respectively,to the free stream. Ac “L Llift coefficient, q“s/2.
18、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3364.Cn”8CxrTc“cEDiw.L.M“RsTvxxYap.75RMpitching-moment coefficient, 5qs/2xlongitudinal-forcecoefficient, q“s/2thrust coefficient, Tq“D2fi/4wing chord, ftmean aerodynamic chord of wing, ftpropell
19、er diameter, f-twing incidence, deglift, l-bpitching moment, ft-lbfree-stream dynamicdynsmic pressure inradius to propellerpressure, /pV2 2, lb/sq ftTslipstream, q + /lb/sq ft)-(D2ktip, fttwice area of semispan wing, sq ftthrust per propeller, lbfree-stream velocity, ft/seclongitudinal force, lbdist
20、ance along chord from leading edge, percent chorddistance perpendicular to chord, percent chordangle of attack between thrust axis and relative wind, degpropeller-blade angle at 0.75 radius, degProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-4 NACA T
21、N 3364flap deflection (subscript“30” or “6o” indicatespercentchord deflected), deginclinationof resultant-forcevector froa thrust axis atzero forward speed, CL”arc tan , degmass density ofxair, slugs/cu ftMODEL AND APPARATUS.The semispanwing in this investigationhad an aspect ratio of 4.55,a taper r
22、atio of 0.714, and an NACA 0015 airfoil section. A plan viewand a photograph of the model are presented in figures 3 and 4, respec-tively. The geometric characteristicsof the mcdel are presented in thefollowing table: *Wing:Area semispan), sqft. . . . . . . . . . . . . . . . . .Span semispan),ft . .
23、 . . . . . . . . . . . . . . . . .Meanaerodynanic chord, ft . . . . . . . . . . . . . . . .Rootchord, ft. . . . . . . . . . . . . . . . . . . . . .Tipchord, ft . . . . . . . . . . . . . . . . . . . . . .Airfoil section . . . . . . . . . . . . . . . . . . . . .Aspect ratio . . . . . . . . . . . . . .
24、 . . . . . . .Taper ratio . . . . . . . . . . . . . . . . . . . . . . . 5.125 . 3.416. 1.514. 1.75. 1.25NACA 0015. 4.55. 0.714Propellers:Disaster, ft. . . . . . . . . . . . . . . . . . . . . . . .Diskarea, sqft. . . . . . . . . . . . . . . . . . . . . . 3?;:Nacel.lediameter, ft. . . . . . . . . . .
25、. . . . . . . . . 0.33Airfoil section . . . . . . . . . . . . . . . . . . . . . . Clark YThe ordinates of the flaps were derived from the slotted flap 2-hof reference 3 and are presented in table I. The slotted flaps were sup-ported by external brackets as shown in figure 4. The cross section ofthe
26、auxiliary-vaneconfigurationis shown in figure 5. The vame was madeof l/8-inch sheet steel.The characteristicsof the propellers used are presented in refer-ence 4. The propellers were driven by variable-frequencyelectric motorsrated at 20 horsepower at 18,000 rpm. The large propeller diameter pre-ven
27、td the use of this high rotational speed, and during these tests thepropeller speed seldom exceeded 7,503 rpm. The rotational speed wasJ.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3364 5. determined by observing a stroboscopictype of ins
28、trument thatindicatedthe output frequency of a small alternator connected to the motor shaft.Eoth motors were driven from a common power supply, ad their speeds wereKusually matched within 10 rpm.The motors were mounted inside the aluminum-alloy nacelles thoughstrain-gagelesms so that the thrust of
29、each propeller could be measured.In addition, total lift, longitudinal force, sad pitching moment of themodel were measured on a balance at the root of the wing.Variations in wing incidence relative to the thrust axis were providedby using different motor-mount brackets for each incidence setting. T
30、hesebrackets were designed so that the thrust axis of each propeller inter-sected the chord plane at the qmrter chord of the mean aerodynamic chord.TESTS AND CORRECTIONSThe investigationused two different experimental setups. Most ofthe tests were conducted at zero forward speed on the static-thrust
31、 stand. at one end of a large room as shown in figures 4 and 6. For these tests,the thrust on each propeller was held at 2 pounds, which gave a dynamicpressure of 8 pounds per square foot in the slipstesm. The blade singlesof the two propellers were adJusted slightly (0.1 or less) in order todevelop
32、 the smne thrust on both propellers. The effects of flap deflec-(tion, propeller blade angle a75R . )3.7 and 8 , wing incidence, and theaddition of an auxiliary vane were investigated at zero forward speed.A few tests with foyward speed were conducted in the Ia.ngley300 MPH7- by 10-foot tunnel. For
33、these tests, the semispanmcdel was mountedfrom the tunnel ceiling and was equipped tith only the inboard propeller.The shaft thrust of the propeller was held constant throughout the angle-of-attack range and was chosen to give a dynsnic pressure of 8 poundsper square foot in the slipstreamat zero an
34、gle of attack. Tests wereconducted with the propeller removed and with the propeller installed andoperating at several thrust coefficients. The Reynoldsslipstreambased on the mean aerodyrmnic chord of 1.514Inasmuch as all static-thrusttests were conductednone of the corrections that are normally app
35、licable towere applied for these tests.number in thefeet was 0.8 x 106.in a large room,wind-tunnel testsThe data obtained in the Langley 300 MPH 7- by 10-foot tunnel have* been corrected for the effects of the tunnel walls on the angle of attackand longitudinal-forcecoefficient of the mcdel and on t
36、he velocity in thetunnel. These corrections were applied as indicated in reference 4.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 NACA TN 3364Correction to the free-stream dynamic pressure for the effects of modelblockage are negligible at low a
37、ngles of attack and have not bee appliedbut can be determined from reference 4.RESULTS AND DISCUSSIONStatic-ThrustConditionIn order to achieve vertical take-off, it is neces6ary to satisfythe conditions in which the lift is greater than the weight and the netlongitudinal force is equal to zero. The
38、cotiigu-rationof reference 2with plain flaps and auxiliary vanes would satisfy these conditionswithan initial attitude of 23 for airplane weights up to 95 percent of thepropeller thrust. Without the auxiliary vanes an attitude of about 45would be required for the plain-flap configuration.Basic slott
39、ed-flapcofiiguration.-The slotted-flapconfigurationshown in figure 2 was investigatedto determine whether the desired turningcould be obained with a less-complicatedwing arrgement than that ofreference 2 (plainflap with two auxiliary vanes). The effect of flapdeflection on the aerodynamic characteri
40、sticsis shown in figure 7. Acomparison of the data of fies 7(c)(d)jand(e)withthedataOfreference 2 indicatesan appreciable improvement in turning effectivenesswith the slotted-flapconfigurationas comparedwith the,p$in-flapconfiguration. Deflection of the 60-percent-chordflap 60 and the30-percent-chor
41、dflap 40 effectively rotated the thrust vector upwardabout 63 with a loss of slightly less than 10 percent of the thrust.The slot openings of the flap for this investigationwere determinedby the path of the nose of each flap (table I) which was derived fromreference 3. These openings are not necessa
42、rily optimum for this config-uration. It is well lmown that, under forward-speed conditionswithoutslipstream,variations in slot openi5 may have rather large effects Onthe aerodynamic characteristicsof wings equipped with slotted flaps.One test in which the flap was incorrectly assembled indicated th
43、at thesemne effects may probably occur also at zero forward speed when the slottedflaps are used to deflect the propeller slipstream.Effect of auxiliary vane.- The auxiliary-vane configurationshown inflgq.ure5 was tested in an attempt to increase the rotation of the effectivetliiust+ector.top surfac
44、e ofbe extended tobeen deflectedtested was notthe vane couldThis vane could possibly be designed as a “slat” on thethe leading edge of the 60-percent-chordflap. It couldthe desired position after the 60-percent-chordflap hadabout 600. The contour of the l/8-inch-sheetmetal vaneexactly the same as th
45、e upper surface of the flap and thusnot be retracted (see fig. 5); however, the contourProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACA TN 3364 7.differences were small smd were not expected to produce important effectson the reults obtained.P Th
46、e aerodynamic characteristics of the configuration with the aux-iliary vane extended are presented in figure 8. With the auxiliary vaneextended the effective thrust vector was rotated upward 74 with a lossof only about 10 percent of the thrust (fig. 8(e). Vertical take-offwould be possible with this
47、 configuration at an initial attitude of 16and at airplane weights up to 90 percent of the total propeller thrust.Effect of incidence.-Positive incidence between the wing chord planeand the propeller thrust axis is seen to increase appreciably the turningangle (fi s. 9 and lO).5 At the lower turning
48、 angles an increase ofabout 3.5 is obtained for each 5 of incidence; however) at the gherturning angles the ratio of increased turning amgle to wing incidence singleis almost one to one within the 10 range of incidence investigated.The inclusion of incidencebetween the wing and the thrust axis had.n
49、o consistent effect on the nose-dowm pitching moment for constant flapsettings (fig. 9(b). The flap deflections required for a given turningangle were reduced, however, and resulted in a small reduction in pitching.moment for a given turning angle.T as men-*.tioned previously, variations in slot open have rather large effects.Provided by
