Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS2498262 A
Publication typeGrant
Publication dateFeb 21, 1950
Filing dateSep 16, 1946
Priority dateSep 16, 1946
Publication numberUS 2498262 A, US 2498262A, US-A-2498262, US2498262 A, US2498262A
InventorsMaurice A Garbell
Original AssigneeGarbell Res Foundation, Maurice A Garbell Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Fluid foil lifting surface
US 2498262 A
Images(3)
Previous page
Next page
Description  (OCR text may contain errors)

Feb. 21, 1950 M. A. GARBELL 2,498,262

FLUID FOIL LIFTING SURFACE Filed Sept. 16, 1946 3 Sheets-Sheet 1 /l I FIGURE I 472 %M/J(INVENTOR.

Feb. 21, 1950 M. A- GARBELL FLUID FOIL LIFTING SURFACE 3 Sheets-Sheet 2 Filed Sept. 16', 1946 FIGURE ZOEhumm SPANWISE SEMI-SPAN STATION ROOT I 3 FIGURE 3 INVENTOR.

Feb. 21, 1950 Filed SECTION LIFT SECTION LIFT SBP 1945 3 Sheets-Sheet 5 FIGURE 5 -4 LIJ ROOT SPANWISE- SEMI-SPAN 2 STATION 2 FlGURE U J 5 2 u.

u. m 0 U ROOT SPANWISE SEMISPAN STATION d.f4 INVENTOR.

Patented F eb. 21 1950 UNITED STATES PATENT (OFFICE-J Maurice A. G'arbll, San"Francisco, Calif, as-

signor, by direct and mesnc assignments, "of one-fourth to *Maurice A. Garbell,= Inc.,*San Francisco, Galif.,a corporation of California, andthree-fourths to GarbellResearch Foundation, San Francisco, Calif, a corporation of California Application September 16, -194.6-,-Serial-N0. 697,281

1 This invention relates to the design and construction of surfaces to bedriven through a fluid, and -in particular through the air,- intended to produce a'useful force component perpendicular t the relative velocity of the fluid with respect -1948;-the general object-of which-is the-attainment of good" stalling characteristics on lifting surfaces by means of anovel method-0f fluid-foil selection,"wherein the mean-line camber-and if necessary the thickness ratio of one or more fluid foil sections interjacent "between the root and the tip'o'f the lifting surface' are varied :from the respective values obtainable by straight line fairing between the-root'and tip sections by following the subject methodof :the said co-pending application.

The 'general' objects of the invention specified in the instant application are the attainment of good stalling characteristics, the elimination of violent rolling moments, the creation of stable mose-downpitchingmoments at the stall. the -niaintenance of adequate lateral 'control effectiveness, the reduction of the fluid-dynamic drag, and a reduction "of the resulting drag moment with respect-to the-root ofthe'lifting surface.

Another object of the invention specified-inthe iristant' application is the attainmentof especiall'y high lifting-surface liftcoefficients in those 'designs" in which engineering considerations other than those pertaining solely to the control of stalling characteristics. perrnit Y the "fluid-dynami- 'fluid foil sections are defi'ned' and explained-in the subject specification of 5 this invention.

Other objects an'd advantages will hex-apparent from anexamiriati'on of the" drawings "accompan'ying the-instant application taken in -'con- 4 junction with the following and in which:

Figure l shows aschem'atic perspective view of a lifting surface designedand constructediaccbfding to theniethod outlined in the' subje'ct specification.

Figure 2illustrates the spanwise distribution of actually prevailing section lift coefficients and the spanwis-e distribution of maximum attainable section lift coefficients on a typical lifting surface designed and constructed'acconding t0 the sub- =ject method of this invention.

Figure 3 illustrates the typical --inception.iand growth of the :stall of alifting surface designed and constructed according to the subject :rnethod o'f'this invention. a V Figure 4 illustrates the procedure employed in the finding of 'the optimum spa-nwise wlocation of the third controlled fluid-foil section in "a lifting surface designedwand constructed: according to "the subject :method of this invention.

Figure 5 illustrates the spa-nwise"distribution sQf actually. prevailing section lift cCOEfl'lClGIltS and the spanwise': distribution -,of-:maximum attainable section lift coefficients ion-a typical iliftinjg :Sunface designed and constructed according to the sub.-

ject metnodbf this invention; :the' ":tip :sectionwof said lifting surface having a thickness ra,tijo smaller than the optimum thickness ratio for lab,- .solutely maximum attainableesectioniliftrcoefi'le :cient for theseriesoftfiuidefoiIsectiQnsEemDIQyed in the lifting surface.

'A preferred embodiment -.of this -:invention is described in the following specification; thepbroad. .scope of the invention" is expressed inthe claims concludingthe instantapplication.

The invention consists of =novelrmethodssand combinations of :methodsdescribed hereinafter, all of which contribute-to;produce;arsafe and rem-- cient lifting surface. :Referring' to the idrawingsiforamoresspecifidqdetails of the invention, Figure I'ISBI'VGStO illustrate ---the preferredsembodiment ofithis.inuenti0n-,cc0msprisinga lifting surfacewith threerorrmore felon- -trol1edfluid-foi1 sections, in which a section with a small mean-line camber l'is IOCBLtBdiidU-th'fIfOOt rof the lifting 1 surface; .1 av section with: a: greater mean-line camber 3 is rlocated at fthetfiuidadyinamically eff ective -tip of the, lifting: surface afthe actual tip fairing ofthe lifting surfacermaycom- -prise a faired :three-adimensional'fibody without identifiable mean-line camber, whichzis =not-:.:of

any consequence in the application of theesu-b- .--ject' invention) -an-dione' or more interjacentysec- :tions 2 are E selected cfollowing @themethod outlined below, said .t-interiacent lfluidefoiI sections having values" of'the:meaneline-fcamberc'at Mari -ance with the va1ues4"obtainablerat thez-respecs tive spanwise stations by-means zofnstraight line fairing between the. fiuid-sfoil wsectionwlocatcdeat the root and the fluid-foil section located at the tip of the lifting surface, wherein the respective values of the mean-line camber of one or more of the interjacent fluid-foil sections exceed the mean-line camber of the more highly cambered tip section. It shall be understood that the preceding considerations apply to all types of lifting surfaces regardless of the respective thickness ratios of the root and tip sections. It shall also be understood that additional considerations relative to the respective thickness ratios of the various controlled fluid-foil sections are presented herein for lifting surfaces wherein the thickness ratio of th root section is the greatest, and the thickness ratio of the tip section is the smallest, respectively, of any fluid-foil section employed in the lifting surface.

Figure 2 illustrates the preferred manner in which this invention, through the employment of the aforementioned method of fluid-foil selection, achieves the establishment of a curvilinear polygon 5 describing the spanwise distribution of maximum attainable section lift coefficients, said curvilinear polygon being so shaped that it envelops closely the curve 6 describing the spanwise distribution of the actually prevailing section lift coefficients, except that beyond the spanwise point I at which the highest actually prevailing section lift coefiicient occurs the maximum attainabl section lift coefficient exceeds substantially the actually prevailing section lift coefficient, so that the stall inception occurs near midsemispan, spreads more prevalently inboardward and to a smaller extent outboardward as shown in orderly progression by curves l2, l3, l4, l5, and [6 in Figure 3, and does not involve the extreme tip of the lifting surface prior to the breakdown of the fluid flow over the entire remaining lifting surface. As used herein the curvilinear polygon 5 describing the spanwise distribution of maximum attainable section lift coefficients is established by the respective values of the maximum attainable lift coefficients of the root section 9, the tip section 8, and the third or additional control section II, and by the respective maximum attainable lift coefficients 5 of the sections obtained by conventional fairing between each pair of controlled sections 9--l I, ll-B, etc.

The curve 6 describing the spanwise distribution of the actually prevailing section lift coefficients at the maximum lift coefficient of the lifting surface is obtained by conventional methods of experimentally verified calculation for the desired lifting surface, taking into consideration the planform, effective aerodynamic washout, section lift-curve-slope characteristics, etc.

The term envelopment as used herein signifies the establishment of curvilinear polygon 5 on the convex side of the curve 6, wherein each individual branch 9-! l, I|--8, and so forth of the curvilinear polygon 5 is tangent or nearly tangent to curve 6.

The following specification outlines the method employed in the design of the subject lifting surface of this invention, whereby to select the most opportune values of fluid-foil section mean-line camber and fluid-foil section thickness ratio required to achieve the objects of the instant invention:

To apply the subject method of this invention it is actually necessary to know only th planform of the lifting surface and the desired stall pattern. Inasmuch as practical considerations other than those pertaining solely to the control of the stalling characteristics ordinarily predetermine certain design parameters of the lifting surface,

4, preferred embodiments of the subject method of this invention are hereinafter explained for two typical combinations of predetermined design parameters:

In the first typical configuration the following design parameters, for example, are assumed to be given a priori: (a) the planform of the lifting surface, based on structural and practical design considerations; (b) the series of fluid-foil sections to be employed, based on high-speed and other performance requirements; (0) the maximum permissible effective aerodynamic washout, based on drag considerations and structural bendingmoment limitations; ((1) the thickness ratio of the fluid-foil section at the root, based on the critical-Mach-Number requirements and structural weight considerations; (e) the thickness ratio of the fluid-foil section at the tip, based on practical space requirements for control-surface balances, etc; (f) the maximum mean-line camber of any fluid-foil section on the lifting surface, based on drag and pitching-moment limitations.

The subject method of this invention is employed firstly to design the lifting surface without any effective aerodynamic washout, that is, with the three or more controlled fluid-foil sections placed at such an angle of incidence with respect to the reference chord plane of the lifting surface that the said fluid-foil sections operate at their respective zero-lift angles of attack when the entire lifting surface operates at its angle of attack for zero overall lift.

Based on fundamental experimental wind-tunnel data available for the preselected series of fluid-foil sections, graphs are plotted showing the variation in the maximum attainable section lift coefficient versus the mean-line camber, thickness ratio, and Reynolds number, respectively; similar graphs are plotted showing the variation in the section zero-lift angle of attack versus the mean-line camber, thickness ratio, and Reynolds number, respectively.

For the spanwise location of the third and additional controlled sections 2 and II, the subject method of this invention utilizes preferably locations between the spanwise point of the highest actually prevailing section lift coefficient I and the spanwise point located twice as distantly from the tip 8 as point 1, with a preferable optimum at the point H, where the tangent to the inboard portion of the curve of spanwise dis-' tribution of the actually prevailing section lift coefficients 1, 8 intersects the horizontal tangent l 9 to the same curve, as shown in Figure 4.

It will be understood, however, that inescapable practical design considerations may require that the additional controlled sections 2 and ll be placed at spanwise stations located inside power plant nacelles or at those spanwise stations where the lifting surface is mechanically jointed for sudden changes in planform taper, or sweep-back, as is the case in craft with removable or foldable outboard panels.

The thickness ratio obtainable at the third section II is calculated by straight-line interpolation between the root section and the tip section or is determined by such structural or other criteria of different nature as may be considered to prevail. However, the subject method of this invention teaches that best results are achieved if the thickness ratio of the tip section 3 is smaller than the optimum section thickness ratio for absolutely maximum attainable section lift coefficient of the fluid-foil series chosen, and if the thickness ratio of the third section} and.- l;lischosen'.edualzto/onsligl'it 1y greater than the saidioptimum"thicknessgratio; sothat the optimum thickness ratio occurseither atwthe third. section 2 and II or. at aspanwise location 2| near thepoint 22 of highest actually prevailing section lift coefiicient.

The; approximate maximum attainable lift c0.- efllcient of theentirelifting surface for. appropriategvalues. of the. Reynolds number is estimated.

for example by dividing the. maximum attain.- ablesection lift coefficient of the third" fluide foil. section (obtained from the aforementioned; wind-tunnel data for the selected values of thesection thickness ratio and the maximum permis sible-mean line camber) by the highestspanwisa value of the additional section lift coefficient (as. defined in Army-Navy-Commerce Manual ANC-1(1) entitled Spanwise Air-Load Distribution), as follows:

C; of interjacent section max lmu in hilhesr and byrepeating this operation with checks of the Reynolds number of the said most highly cambered interjacent section as. specified in the.

co-pending application, until the maximum at tainable lift coefficient of the lifting surface. is accurately determined.

The spanwise distribution 6 of the actually prevailing section lift coemcients is then calculated for the maximum liftcoefficient Cr of the entire lifting surface, following oneof the. conventional calculation methods.

For the Reynolds number and the pro-selected. thickness ratio of the tip section, the required. value of the mean-line camber is determined;

from the graph showing. the experimentally measured variation of the maximum. attainable.

section lift coefficient with varying. mean-line. camber, selecting that value ofv the mean-line camber that produces av maximum. attainable...

section lift coefiicient 8i substantially equal to. the highest actually prevailing section lift coefll; cient'l;

For the Reynolds number and the pre-selected. thickness ratio of the root section, the required. value ofthe. mean-line camber is determined from the graph showing the experimentally measured variation ofthe' maximum attainable. sectionlift coefiicient with varying mean-line. cam-- ber, selecting that value. of the mean-line, cam.-

ber that-produces a maximum attainable section, lift-coefficient 9 equal to or slightly superiorv to.

the section lift coeflicient actually prevailing" over the root' section.

From the foregoing, it will be readily seen.

that. the lifting surface obtained by the invention; and defined by the curvilinear polygon embodies the combination of a fluid-foil section.

I" or- 9 having the smallest mean-line camber at the root afiuid-foil section 3 or. 8 having a great-.

ermean-line camber at the tip, and one orv more interjacent controlled sections 2 or ll. having values of the mean-line camber at variance.

with the values 4 obtainable at the respective spanwise stations by meansof straightlinefai'ring between the root section and the tip section, wherein the mean-line camber of the third;

or an additional interjacent controlled section exceeds the mean-line camber of the morehighly cambered tip section, while avoiding the. uncle.-

sirablenefl'ects ofzany materlalaamountzofiaerodys.

namicawashin:

If; forgreasonszother than: those pertaining solelysto the.control-:of*stalling characteristics, wash I outx-is desired, aasmall' amount: of. effective" aerodynamiczwashout is.introduced, /2 to 1 in eachstep: of; the: application; of the method, wherein the itotalieffective. aerodynamic: washout is distributedp-in appropriate: fashion between the con trolled sections .andrwherea the. total: washout is.

lessithan the. maximum; permissible washout. as definedimthe aforesaid initial design assumptions; The entire. heretoforespecified' procedure.

including the establishment. of a curve 6' con fornringzto. the-washout; chosen is then repeated forrztl'ie selected: amount. of reflective aerodynamic washout; until the desired results as illustrated ilCh'FIglH-ES: 2 and; 3, are attained while satisfying.

the; aforesaid; requirementsaof difierent nature.

Atypical} example of:=the: application of the principles of. this-invention to one. well-known: type of lifting. surface. is as follows: Here we:

assume a planformtaperratio of-three to one, anuaspect. ratio of ten; a total. effective aerodynamic. washout: of zero. degree, a section thick ness ratio-tapering linearlyfrom 22'per centtat. the.:roo.t to: 15 per cent at thetip, the utiliza tion of 63- series NACA low-drag fluid-foil:

sections,..a; mean-line. camber of the. mosthighly cambereda. controlled section. .21: characterized by an:.idea11-lift coefficient C1 equal to. 0:4. The term. ideal lift'coefficient is to be interpreted 315;.(18fihfld bythe. National Advisory Committee for. Aeronautics nomenclature and is herein used? as:. a; parameter characteristic of the mean-line. camberzof a. fluid-foil section. Calculationsbased onconventionalmethods will indicate that a lift.- ing;-.surface= having: the above general designparameters .will; experience; at .its maximum result?- antzli-ft: coefficient; adistributi'onpf section lift-cm.

efficients as illustratedin. curveafi;

Following the procedures 'hereinbefore de-- scribed, we. achieve in the: above-outlined con-. struction the: desirablestalling= characteristics: taughta by this invention; by. placing; the most:

highlywambered. controlled sectionat a:. station approximately.- 70' per centof .the semi-span from the;ro.ot;andiwith an; effective'aero dynamic. wash-- out; ofczero; degree withrespect' to the root sec.-

tion and": through: the use. of mean-line. camber.-

ofgthelrootzsection'. I.. characterized by an "ideal lift coefficient C15 equal; to: 0:1,.and a mean-line camber of the tip section 3 characterized by an ideal lift coefficient C1 equal to 0.35.

In this structural example the mean-line camber of; theinterjacent controlled section 2 is bodiedin various devices wherein the thicknessgreater than that of the root sect-ion l and of" the tipsection 3; and hence greater than that of the interpolated section 4 obtainable at-the n per cent semi-span station: by -means" ofstraight-linefairingbetween'sections I and 3, and which accomplishesthe envelopment' of curvesfi by the I curvilinear polygon '5.

It will be" fully appreciated by those skilled in thisa'art that. the invention may bereadily emratio of-the interjacent section 2 is varied'from that obtainable through straight+line fairing be-..

tween root: section. Land-tip. section 31in. order to--facilitate the attainment. of: the objectives of thisainventionwith the smallest possible range of.v a1ues --of section mean-line camber.

The. second typical; configuration differs. from. the, first, in\, that twov interiacentg SBCtiODSl 2a may be.-z.;uti 1ized. Hence, the. following: design pas.

rameters are assumed tobe given: a priori: (a) The plan form of the lifting surface; (b)- the series of fluid-foil sections to be employed and their fluid-dynamic characteristics; the maximum permissible effective aerodynamic washout; (d) the thicknessratios of the fluidfoil section at the root and of the fluid-foil section at the tip, respectively; (e) the maximum mean-line camber to be assigned to any fluid foil section on the lifting surface.

The number of interjacent controlled fluidfoil. sections, in this case, is not limited. The following representative specification applies to the case of two interjacent' controlled fluid-foil sections; however, the reasonings specified therein are obviously usable in the design of lifting surfaces with a different number of interjacent controlled sections. Here it will be understood that the values of the mean-line camber. of one or more of the interjacent controlled sections 2 are greater than that of the more highly cambered tip section 3, while one or more of the remaining interjacent controlled sections 2 may be either greater or smaller thanthat of the aforementioned tip section 3, depending on the range of section thickness ratios encountered between the root and the tip of the lifting surface.

In this case the instant method teaches that the optimum spanwise location for the interjacent fluid-foil section having the greatest meanline camber is in the vicinity of the spanwise station carrying the highest actually prevailing section lift coefficient 1, and that the optimum spanwise location for the second interjacent' fluid-foil section is point IT, where the tangent. at the root to the curve of spanwise distribution of the actually prevailing section lift coefiicients l8 intersectsthe horizontal tangent [9 to the same curve, as shown in Figure 4. The instant method also teaches that best stalling characteristics are obtained by assigning to the two or more interjacent fluid-foil sections valuesof the'i section thickness ratio that, for the series of fluid-foil sections selected, yield the absolutelymaximum attainable section lift coefficients.

The approximate maximum attainable lift coefficient of the entire lifting surface is estimated by dividing the maximum attainable section lift coefficient of the most highly cambered fluid-foil section by the highest spanwise value of the additional section lift coefficient in a, manner substantially similar to that previously outlined. s

,The spanwise distribution of the actually pre-, vailing section lift coefficients 23 is then calcu lated for the maximum lift coefficient of the en-. tire lifting surface as previously outlined.

For the Reynolds number of the additional interjacent fluid-foil section, preferably located at the spanwise station ll abovedefined, the required value of the mean-line camber and if neeessary the thickness ratio is determined substan-. tially as outlined for the fluid-foil section II in the co-pending application.

The value of the mean-line camber of the fluid foil section located at the tip of the lifting surface is not of consequence in the application of the subject method of this invention, pro-- vided that the maximum attainable section lift coefficients represented by the curved segment connecting 1.points 2 2 and 20 Figure remains POL subst'antiallyabove the curve of actually 'p'r'e vailing section lift coeflicients 23; 5 c If the designer intends to achieve positivestall' inception in ace'rtain spanwise panel of the lifting surface, the subject method of this invention specifies that in either of the aforedescribed design procedures the mean-line camber and thickness'ratios, as well as the spanwise location, of the sections comprised within or adjacent to the panel forwhich stall inception is desired be so selected that within the stall inception panel the curve of maximum attainable section lift coefficients lies slightly below the curve of actually prevailing section lift coefficients, without modifying the aforedescribed relationship of the maximum attainable section lift coefiicients and the actually prevailing section lift coefficients on the remainder of the semispan of the lifting surface outside of the stall-inception panel proper.

"If, 'in any of the aforedescribed cases, the lift-, ing surface under consideration is modified by"- excrescences such as, for example, power-plant nacelles, or flaps that modify the local zero-lift angle and the local maximum attainable section lift coefficient, the calculation of the maximum attainable section lift coefiicients and of the effective washout at the various spanwise stations takes due account of the effects of these modifica-f tions by introducing equivalent values of the effective washout and section mean-line camber into the subject method of this invention.

Uponcompletion of the procedure outlined for the subject method of this invention, the zero-. lift angles of the fluid-foil sections selected thus-f" 1y are determined for their respective mean-line stalling characteristics of lifting surfaces designed and constructed according to the subject method of this invention are directly attributable to the.

u'se of three (or more) controlled fluid-foil sections selected according to the hereinbefore speci fled method of this invention, and to the afore-.; described method employed in the design of such:

lifting surfaces.

This invention accomplishes an important im provement in the art, and the discoveries herein disclosed are of great value to all types of aircraft (as well as to craft operating in other fluids), throughout their entire operating range, and especially in the critical low-speed operation where steadiness of lift and lift variation, stability of the craft, control effectiveness, and smooths,

ness and stability of control forces are of vital importance for the safety and efliciency of the craft; also in violent maneuvers at high speeds.

when high liftingsurface lift coefficients coml A lifting surface with three or more 76 ti'olled fluid-foil section's, in'which the first sec tion with a small mean line' camber is'located at the root, the second section with greater meanline camber is located at the fluid-dynamically effective tip, and the third or additional fluidfoil sections arelocated at stations interjacent between the root and the tip, wherein the values of the mean-line camber of the interjacent fluidfoil sections are at variance with the values of the mean-line camber obtainable at the respective'spanwise stations by means of straight-line fairing'between the fluid-foil section located at the root of the lifting surface and the fluid-foil section located at the tip of the'lifting surface, and wherein the mean-line camber of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered 'tip section, said three or more controlled fluid-foil sections having values of the mean-line camber selected in such manner that the resulting spanwise distribution of maximum attainable section lift coefficients of the three or more controlled sections forms a curvilinear polygon enveloping a curve representing the spanwise distribution of section lift coefficients prevailing at the maximum attainable lift coefiicient of the lifting surface, for a given planform and discarding the effect of any material amount of aerodynamic washin.

'2. A lifting surface with three or more controlled fluid-foil sections adapted to provide stall inception within a predetermined interval of spanwise stations, in which the first section with asmall mean line camber is located at the root, the secondsection with greater mean-line camber 'is located at the fluid-dynamically effective tip,-and the thirdor'additional fluid-foil sections are located at stations interjacen't between the root and the tip, wherein the values of the meanllne camber of the interjacent fluid-foil sections are at variance With'the values of'the mean-line camber obtainable at therespectivespanwise sta tions by means of straight-line fairing between the fluid-foil section located at the root of the lifting surface and'thefiu'id-foil'section'located at the tip of the lifting surface, and wherein the meanline camber of one or more of the interjacent fluid-foil sections exceeds themean-line camber of the more'hi'ghly cambered tip section, said' three or more controlled fluid-foil sections having values of the mean-*ilne camber selected in such manner that the resulting spanwise :distribution of maximum attainable section lift coe'fiicien'ts' of the-three or more controlled sections form-s acurvilinearpolygon enveloping a curve representing the spanwise distribution of section lift coefli'cien'ts prevailing at the'maximum attainable lift coefficient of the lifting surface, *for a given planform and discardingthe efiectof any material amount of aerodynamic washin, and thatthe said'polygon representing the resulting spanwise distribution of maximum attainable section lift coefficients be so shaped that the first intersection with the curve representing the span- Wisewdistribution of'sprevailing section lift coefficients'occurs inithatinterval of spanwise stationsifor which r'stall inception is ':to be obtained.

A ilifting surface with-three or "more controlledfluid foilisections, in which the first section withra small mean-"line camber and greatest thickness ratio isilocated at the root, the second section with greater meanlinecamber: and smallesttthicknessratio is located at the fluid-dynamically'iieffective tip,'rand the third or additional values ofithe thickness .ratio of the interjacent fluid-foil sections are greater than the values or tionilocated at the tipof'thelifting surface, and

wherein the mean-line camber of one or more -01 the interjacent fluid-foil sections exceeds the mean-"line camber of the morehighlycambered tip section.

4. A lifting surface with three or more controlled fluid-foil sections, in which the first'section W'ith'asmall mean-line camber is located at the root,the second section with greater meanline 'camber is "located at the fluid-dynamically effective tip, and the third or additional fluidfoil sections are located at stations interja'cen't between the root and the tip, wherein the values of the thickness ratio of the interjacent fluidfoil sections are at variance with the values er the thickness ratio obtainable at the respective spanwise stations 'by means of straight-linefairin'g between the "fluid-foil section located at= the root' o'f the lifting'surface and the fluid-foil section located -at the tip o'f'the lifting surface, and

planform -andxdiscarding the effect o'f'any mate-' rial amount of aerodynamic washin.

*A liftingsurface with three or more *controlled fluid-"foil L sections adapted to provide stall inception within a predetermined interval of spanwise' stations, in which the first section with a:small-mean-line camber is located at the=root. the .second section with greater mean-line camber'is'located'at the fluid-dynamically effective tip, and-the third or additional fluid-foil sections are located at 'I'station's interjacent between the root -an'dthe tip, wherein the values of the thickness 'ratio of the interjacent fluid-foil sections are at varian-ce with the values of the thickness ratio obtainable at the respective spanwise stations Eby "means of straight-line fairing between the "fluid-foil' section'located at the root of the lifting surface aridthe fluid-foil section located at' thetip of the lifting surface, and whereinthe mean-line camber of one or more of the interjacent fluid-"foil sections exceeds the 'mean-line camber of the more 'higlilycam'beredtip section, saidthree or more controlled fluid-foil sections having' valuesof themean-line camber and the thicknessratio selected'in such manner thatthe resulting spanwise distribution of maximum attainabl-e section lift coefficients of the'three "or more-controlled sections forms'a curvilinearpolygon enveloping a curve representing the spanwise distribution -of section lift coefficients prevailing at themaximum attainable lift coefficient of the lifting surface, for a given planforrn and discarding the effect of ,any material amount'of aerodynamic washin, andthat thesai'd resultingintersection with the spanwise distribution "ofprevailing section lift coefficients occurs in that interval of spanwise stations for which stall inception is to be obtained.

6. A lifting surface with three or more controlled fluid-foil sections, and having a highest actually prevailing section lift coefficient at a pre determined spanwise station, in which the first section with a small mean-line camber is located at the root, the second section with greater meanline camber is located at the fluid-dynamically effective tip, and one of the interjacent fluidfoil sections is located near a spanwise point where a tangent to the inboard portion of the curve representing the spanwise distribution of actually prevailing section lift coeificients, for a given planform and discarding the effect of any material amount of aerodynamic washin, intersects a substantially horizontal tangent to the highest point of the same curve, wherein the values of the mean-line camber of the interjacent fluid-foil sections are greater than the values of the mean-line camber obtainable at the respective spanwise stations by means of straightline fairing between the fluid-foil section located at the root of the lifting surface and the fluidfoil section located at the tip of the lifting sur-- face, and wherein the mean-line camber of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered tip section.

'7. A lifting surface with three or more controlled fluid-foil sections, and having a highest actually prevailing section lift coeificient at a predetermined spanwise station, in which the first section with a small mean-line camber and greatest thickness ratio is located at the root, the second section with greater mean-line camber and smallest thickness ratio is located at the fluid-dynamically effective tip, and one of the interjacent fluid-foil sections is located near a spanwise point where a tangent to the inboard portion of a curve representing the spanwise distribution of actually prevailing section life coefii-' cients, for a given planform, and discarding the effect of any material amount of aerodynamic washin, intersects a substantially horizontal tan-' gent to the highest point of the same curve,

wherein the values of the thickness ratio of the interjacent fluid-foil sections are greater than the values of the thickness ratio obtainable at the respective spanwise stations by means of straight-line fairing between the fluid-foil section located at the root of the lifting surface and the fluid-foil section located at the tip of the lifting surface, and wherein the mean-line camber of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered tip section.

8. A lifting surface with three or more controlled fiuid-foil sections, and having ahighest actually prevailing section lift coeflicient at a predetermined spanwise station, in which the first section with a small mean-line camber is located at the root, the second section with greater mean-line camber is located at the fluiddynamically effective tip, and two of the interjacent fluid-foil sections are located respectively near the spanwise station of highest actually prevailing section lift coefilcient and near a spanwise point where a tangent to the inboard portion of a curve representing the spanwise distribution of actually prevailing section lift coefih cients, for a given planform and discarding the effect of any material amount of aerodynamic washin, intersects the horizontal tangent to the highest point of a substantially same curve, wherein the values of the mean-line camber of the interjacent fluid-foil sections are greater than the values of the mean-line camber obtain able at the respective spanwise stations by means of straight-line fairing between the fluid-foil section located at the root of the lifting surface and the fluid-foil section located at the tip of the lifting surface, and wherein the mean-line camber of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered tip section.

9. A lifting surface with three or more con-- trolled fluid-foil sections, and having a highest actually prevailing section lift coeflicient at a predetermined spanwise station, in which the first section with a small mean-line camber and greathorizontal tangent to the highest point of the same curve, wherein the values of the thickness ratio of the interjacent fluid-foil sections are greater than the values of the thickness ratio obtainable at the respective spanwise stations by means of straight-line fairing between the fluidfoil section located at the root of the lifting surface and the fluid-foil section located at the tip of the lifting surface, and wherein the meanline camber of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered tip section.

10. A lifting surface with three or more controlled fluid-foil sections, in which the first section with a small mean-line camber and greatest thickness ratio is located at the root, the second section with greater mean-line camber and smallest thickness ratio is located at the fluid-dynamically effective tip, and the third or additional fluid-foil sections are located at stations interjacent between the root and the tip, wherein the values of the thickness ratio of the interjacent fluid-foil sections are smaller than the values of. the thickness ratio obtainable at the respective spanwise stations by means of straight-line fairing between the fluid-foil section located at the root of the lifting surface and the fluid-foil section located at the tip of the lifting surface, and wherein the mean-line camber of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered tip section.

11. A lifting surface with three or more controlled fluid-foil sections, and having a highest actually prevailing section lift coemcient at a predetermined spanwise station, in which the first section with a small mean-line camber and greatest thickness ratio is located at the root, the second section with greater mean-line camber and smallest thickness ratio is located at the fluid-dynamically effective tip, and one of the interjacent fluid-foil sections is located near aspanwise point where a tangent to the inboard portion of a curve representing the spanwise dis--v tribution of actually prevailing section'lift co-l eflicients, for a given planform and discarding the effect of any material amount of aerodynamic washin, intersects a substantially horizontal tangent to the highest point of the same curve, wherein the Values of the thickness ratio of the interjacent fluid-foil sections are smaller than the values of the thickness ratio obtainable at the respective spanwise stations by means of straight-line fairing between the fluid-foil section located at the root of the lifting surface and the fluid-foil section located at the tip of the lifting surface, and wherein the mean-line camher of one or more of the interjacent fluid-foil sections exceeds the mean-line camber of the more highly cambered tip section.

12. A lifting surface with three or more controlled fiuid-foil sections, and having a highest actually prevailing section lift coefiicient at a predetermined spanwise station, in which the first section with a small mean-line camber and greatest thickness ratio is located at the root, the second section with greater mean-line camber and smallest thickness ratio is located at the fluid-dynamically effective tip, and two of the interjacent fluid-foil sections are located respectively near the spanwise station of highest actually prevailing section lift coefficient and near a spanwise point where a tangent to the inboard portion of a curve representing the spanwise dis- 14 tribution of actually prevailing section lift coefficients, for a given planform and discarding the efiect of any material amount of aerodynamic washin, intersects a substantially horizontal tangent to the highest point of the same curve, wherein the values of the thickness ratio of the interjacent fluid-foil sections are smaller than the values of the thickness ratio obtainable at the respective spanwise stations by means of straight-line fairing between the fluid-foil section located at the root of the lifting surface and the fluid-foil section located at the tip of the lifting surface, and wherein the mean-line camber of one or more of the interjacent fluidfoil sections exceeds the mean-line camber of the more highly cambered tip section.

MAURICE A. GARBELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,547,644 Cronstedt July 28, 1925 1,817,275 Soldenhoif Aug. 4, 1931 1,890,079 Focke Dec. 6, 1932 2,441,758 Garbell May 18, 1948

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1547644 *Oct 31, 1921Jul 28, 1925Fed Engineering CompanyAerofoil
US1817275 *Mar 8, 1929Aug 4, 1931Alexander SoldenhoffWing for aeroplanes
US1890079 *May 14, 1930Dec 6, 1932Henrich FockeAircraft wing
US2441758 *Jul 16, 1946May 18, 1948Maurice A Garbell IncFluid-foil lifting surface
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4611773 *Dec 27, 1984Sep 16, 1986The Boeing CompanyTapered thickness-chord ratio wing
US4711597 *Jul 18, 1986Dec 8, 1987University Of Iowa Research FoundationVanes for bank protection and sediment control in rivers
US5056741 *Sep 29, 1989Oct 15, 1991The Boeing CompanyApparatus and method for aircraft wing stall control
Classifications
U.S. Classification244/35.00R
International ClassificationB64C3/14
Cooperative ClassificationB64C3/14, Y02T50/12
European ClassificationB64C3/14