US 1810693 A
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Description (OCR text may contain errors)
June 16, 1931.
H. ALFARO 1,810,693
AERolLANE Filed March 7, 1928 2 Sheets-Sheet 2 Patented June '16, 1931 UNITED STATE-sl PATENT oFFlcE l f HERACLIO ALFARO, F EAST CLEVELAND, OHIO 4 AEROPLANE Application med miren 7,
This invention relates toaeroplanes, and
more particularly to aeroplane wings and aeroplane control surfaces', and has for its object. to provide advantageous means for- 5 increasing the lift of aeroplane surfaces.
Aeroplane wings give vmore lift at higher angles. The geometric angle at Whlch most wings give their maximum lift yarles usually from 15 to 20 degrees. At higher angles,
the lift in some cases decreases graduallyand in others breaks down suddenly tov a smaller figure. In control surfaces, formed either by a rigid unit or by a plurality of articulated parts, the action is much the same, the lift decreasing with'any increase in the angle beyond that of maximum liftf Special wing constructions have been devised in which the angle of maximum lift is increased and in which a higher maximum lift is obtained than with the' usual type of wing. Some of these special Wings obtain the increase of lift by the use of a lapnear the trailing edge.` This result may also be obtained by the combined motion of rotation and translation of a Hap as described in my copending application Serial No. 236,342,`
filed Nov. 28, 1927. In some instances, an in'- crease of lift is obtained by the action of a slot near the leading edge with the resulting change Vof 'low around the airfoil, and in other instances, the combination of a leading edge slot and a trailing edge flap is used.
Nearly all of these devices require the operation of a controlling mechanism which demands a considerable physical effort on the dition, they necessitate a certain increase in the Weight of the lifting units. Furthermore, these devices offer a greater drag or head resistance tending to reduce speed even when the lift increasing mechanism is not in operation. Also, some ofthese mechanisms require, for the maximum lift, an angle of attack which ispdiiicult to obtain in'normal operation of the aeroplane, and especially in landing. y
In Wind tunneltests, great increase of lift has been obtained by releasing compressed air on the suction side or upper face of an airfoil. The possible objection of this 192s. serial No. 259,811.
wings efficiently and without additional apv paratus.
Another object is to provide the neces saryl means within a reasonable amount, if'
any, of additional Weight. Y
A third object of the invention'is to avoid early stalling of aeroplane wings, to provide a high maximum lift, and to maintain a high value of lift throughout a relatively wide range of angles of attack without sudden brcakages of said lift value.
Still another object of my invention is to provide a lift increasing means which is simple in operation and which requires little effort on the part 'of the operator.
Another obj ect is to provide said maximum lift at relatively low angles of attack which the flying machine can easily be brought into.
Other objects of the invention are to obtain better lateral control by providing better aileroncontrol at low speed and to obtain better rotational stability.
Other objects will be apparentto those skilled in the art from the vdescription of it hereinafter given. Y
Figs.'-1, 2, 3 yand 4 show in transverse section, 4different forms of airfoils embodying the invention.
Figs. 5,6, 7 and 8 are sectional views showing Wing structuresl embodying the invention in which means is provided for contro1 into the wings and out through openings in the suction Lside thereof.
Fig. 11 is a fragmentary section showing a modified form of the invention utilizing heated air.
Fig. 12- is a diagrammatic view illustrating a further modification of the invention in which both the inlet and outlet openings are in the upper or suction side of the aircrease the liftingcapacity of the wing.
Moreover, I have found that by combining the action of a. flap with that of the above mentioned passages, as illustrated in Figs. 2, 4, 6, 13 and 14 of the drawings, a greater amount of air can be released through the suction side exits and a lower angle of maximum lift can be obtained.
Also, I found it advantageous to locate the intake passages at the points on the wing where the air pressure is highest, so as to obtain a. maximum fiow of air.
Furthermore, by controlling the intake and exit openings, as illustrated in Figs. 5, 6, 7, 8, 9 and 13, the increase of lift provided thereby can be utilized when desirable and at other times, the drag or head resistance tending to reduce speed can be reducedv by shutting the openings. I have found, also, that the control of these openings may serve to in crease the efficiency of lateral control of the wings and to reduce rotational instability, usually referred to as spinning It is known that in the plainjtype of airv foil, theiflow becomes irregular and turbulent on the suction side of the airfoil as the angle of attack approaches that of maximum lift. Such irregular flow does not follow any more f the contour of the upper face of the wing but detaches itself from said surface so that increased downward deflection of the air cannot be obtained by further increase in the angle of attack of the wing and, therefore, the lift cannot be increased any further. l
,The purpose of transferring air from the pressure side to the suction side of an airfoil is, therefore, to maintain throughout a wider range of angles of attack, a smoother fiow'that will follow the contour of the airfoil. This is usually called boundary v layer control. The supply of air may also be ob-v tained, as illustrated in Figs. 7, 8 and 9, from scoops placed at suitable points, preferably on the pressure side of the wing. Said scoops can be rigged up when not needed thereby reducing the overall air resistance to motion. When radiators are used, the air past the radiators can be collected into the wing, as
illustrated in Fig. 10, for the purpose herein described. The heated air will serve at the same time to avoid ice or sleet formation on the wings. If one or more aircooled engines are used, it can be arranged to collect the heated air past the engine in such a way as to pour it into the wing structure, as illustrated in Fig. 11, for the duofold purpose also of increasing the lift and avoiding ice or sleet formation.
Any number vof intake openings or passages to pour or force the air into the wing may be used; and also any number of openings may be arranged in the-top. Preferably, these should 4be narrow slots extending spanwards of the wings.
As shown in Fig. l, a passage 1 is located on the under or prefsure side of the airfoil adjacent the forward edge at the point of maximum pressure on the airfoil and admits air to the chamber within the airfoil, which is indicated by the numeral 1a inthe drawings, and which is provided with exit openings 2, 3 and 4 to the upper or suction side of the airfoil. By placing the inlet opening l at the point of greatest pressure, a greater volulne of air will be forced into and through the Aairfoil than would b e the case if the. inlet opening were placed elsewhere. At steep angles, the difference of pressure between the under face and the upperfa-ce of the airfoil establishes a current of air through the outlet openings in the direction indicated by the arrows which tends to blow away the dead air or eddy region above the upper face, causing the air to follow closely the profile of the upper face so that the wing positioned at a steep angle imparts a greater downward impulse to the air with the result that a greater lift lis obtained.
In Fig. 2, a flap 5 is provided along the rear edge of the airfoil which may be moved backwards and swung downwardly to control the pressure on the under side of the wing, as described in my application No. 236,342, above referredto. In all flap and wing combinations, arelatively high ressure is built up in the vertex of the angle between the fiap and wing, and this excess pressure Will force air through openings 6 in the wing adjacent the flap and through the chamber 1a to the outlet slots 2, 3l and 4 and the flow of air will vary as the angle of the flap is varied. If def 'ing 6 when in its uppermost position.
In Fig. 3, the flap 5 is hinged at 7 and when pulled dowinfopens the inlet passage 6 to the chamber 1a tosupply air to the outlet passages 2, 3 and 4. An extra opening 8 between the flap 5 and the body of the airfoil can be provided, if desired. As shown in Fig. 3, a plurality of springs 9 in tension may be connected to the wing and flap to facilitate the operation otifthe flap. The point of attach.- ment 10 ofthe spring 9 to the lap is so located that the spring loads produce smaller torque loads about pin 7 when the flapv is up, said loads increasing gradually as the flap is brought down. The air loads in torque a out pin 7 increase also as the ap goes'down but with an opposite sign, withthe result that both loads tend to counteract each other, thus releasing the operator from a part or all the effort required to operate the flap.
Fig. 4 shows a hollow airfoil having a top wall in the form of a plate which has a number of small passages v11 tending to direct outgoing air toward the trailing edge. The clearances between the flap and wing forming the passage at 8 may be such as to increase gradually the size of the passage as the iap moves down or, if desired, they may be such as to provide a passage of substantially unvarying size for any position of flap 5. As shown in dotted lines indicated at 12 in Fig. 4, the flap 5 may be adjusted to a negative angle so that it may be used as an aileron for lateral f control. 'I he passage 6 is closed upon upward adjustment of the iap or aileron and opened upon downward adjustment which results in a lateral control of greater effectiveness due to the aggregated effect of the ailerons themselves,`as in the usual aileron control, plus the effect due to the boundary layer control, as previously explained. The inner end of the aileron, when the aileron is'adj usted to a negative position, protrudes past the lower face of the airfoil and causes a greater drag whichreduces the total yawing moment due to both ailerons. ln case the boundary layer control` provided bythe present invention is used for improving aileron control only, the extent in which openings 11` should extend spanwards on the Wing should not be more than what may be required for obtaining the desired improved aileron control. l
' Fig.' 5 shows a front opening in the lower face of the airfoil corresponding to the openl ing 1` in the modification shown in Fig. 1 and this opening is provided with a shutter 13 mounted to pivot about a pin 14 to control the passage of air to the chamber 1a. The exit openings 2, 3 and 4 are also provided with pivoting shutters 15,16 and 17. Alliot said shutters are connected by linkages 18, 19 and 20 to an operating lever 21 by which the shutters may be adjusted to the desired position. This arrangement has the advantage of providing smooth wing surfaces for normaliying with the resultingreduction in profile drag.
yloWer angle of attack than and 17, which are connected by linkages- 18, 19
and 20 to the adjustable flap* 5, so that the movements of the shutters are simu taneous with the movements of theiap. When flap 5 is moved down about its pivot 7,'the shutters 15,16 and 17 are simultaneously moved downwardly to open the outlet passages 2, 3 and 4, the shutters moving gradually to increase the size of the outlet passages as the flap is moved down. The passage 6 is opened at the same time so that the flow of air into the chamber 1a and through the outlet pasages is dependent on the angle of theliap. The advantage of this arrangement is to provide a smooth surface when the high lift mechanism is operated and to obtain higher lift values and a p with the openings and shutters alone.
Fig. 7 shows exit openings 2 and 3 provided with shutters 15 and 16 which'are linked by a rod 19 and controlled by lever 121 such as previously described in connection with Fig. 5. Inlet openings to the chamber 1a are provided on the under side of the wing adjacent the forward edge and a scoop 23 is connected by a hinge 24 to the rearedge of the opening to increase the volume of air delivered into the chamber 1a. The opening and closing movements of the scoop occur simultaneously With those of the shutters 15 and 16 by reasonl of the' linkageI 25 connecting the scoop to the shutters, 1these movements being controlled by the vlever 21 yso that when the shutters are closed, the scoop is' also closed and vice versa.
The width of the scoop spanwards may be limited to a small portion.. of the span and also a plurality of scoopscan be placed along the span. The sides 26 ofthe scoop are moved into the wing as the scoop is closed, occupying, in the closed position of the scoop, the4 2, 3 and4 and adjustable louverfplates 27, 28
and 29 that serve as shutters for the exit open'- ings. The louver plates are pivoted at the forwardedges of the openings and are linked together by rods 18 and 119 so that they can .be Loperated by a lever 21,- corresponding to the operating lever shown in Figs. 5 and 7.
The air is admitted to the chamber 1a through openings 30` and 31 inthe under side of the `airfoil. These openings can be shut at will bylouver plates 32 and 33 hinged to the body of the airfoil adjacent the rear edges ofthe openings. The movements of the louver plates 32 and 33vare caused to be simultaneous with each other and with those of shutters 27 28 and 29 by means of linkages 34 and 35.
This arrangement provides a positive intake of air when required and provides a smooth airfoll contour when the openings are closed.
If desired, the operation may be made automatic by connecting the level.` 21 to the air i foil througha spring 88, which tends to hold` matic operation, which can be applied to any type of shutter, has obvious advantages.
T Vprefer to surround the openings with fairings rounding the edges so as to obtain a smoother fiow in and out of the airfoil.
These' fairings are shown by 36, 37, 38 and 39 in Fig. 8. Fair-ings of other suitable shapes can be used.
Fig. 9 representsanother form of intake opening located at the forward edge of the airfoil in which cover plates 41 and 42 are pivoted attheir rear edges and connected for simultaneous movements in opposite directions by linkage 43, a lever 21 serving to adjust the position of the cover plates. Plate 41, when open, serves to deflect the air into the chamber la of the wing. This double cover plate arrangement can be placed along the whole spa-n of the airfoil as well as along a part only of it, or, if preferred, a plurality of such assemblies can be placed in a single wing. The plates 41 and 42 are preferably so designed that when in engagement with each other, they yclose the wing practicallyK airtight so as not to allow air leakages, and to let escape air only when and where desired. This form of control mayI be used with or without the flap or aileron.
Fig. 10 shows a. boundary layer` control syst-em employing heated air in which the engine is the source of heat. The engine, in this case, may be of the water cooled or steam cooled type suitably connected to a radiator 53. The radiator 53 is exposed in front and the air heated in; passing through the radiator can be permitted either to pass straight backwards through an opening controlled by a louver 54l or when the louver 54 is closed, to pass downwards into the chamber l@ of a wing 46 to supply the necessary air to openings of any of the types described.
Louver 54 is hinged at'55 and is linked to' pivoted louver plates 56 and 57 through rods 58 and 59. A handle 21 controls the motions of thc` three louvers described so that when louver 54 is open, louver` plates 56 and 57 close .he passage of ai r into the wing and vice versa.. Dotted lilies show the motiolrdescribed by the three louvers. This arrangement, in addition to providing the boundary layer control serves to prevent ice or sleet formation on the wing when/iying Iin cold weather.
F ig. 11 shows `a modification having -two -exit openings 2 and 3 with shutters 27 and 28 and intake shutter 32 linked together and operated byl handle 21, as previously described in connection with Fig. 8. Passages 61 and 62 are provided within the airfoil` lengthwise thereof through which hot air obtained from the engine or any other source is circulated. Several holes of any shape may be provided along the length of these passages, as shown at 63 and 64 to permit the hot air, to mingle with the incoming air. The hot air circulated through 61' and 62 can be replaced by exhaust gases from the engine or engines or by a mixture of air and eX- haust gases.
The air allowed through opening 30 to chamber la is thusv heated and ice or sleet formation is avoided.
Fig. 12 shows a` modification in'wllich a hollow airfoil section 65 is provided with openings 66, 67 and 68 in the upper wall of the airfoil communicating with the chamber 1a. The pressure distribution on the suction side of an airfoil at high angles is approXimately as shown by arrows 69 and envelope curve 70. Greater. depression is therefore found in the neighborhood of the opening 66 than around the openings 67 and 68. The opening 66 is formed to favor an outgoing flow while the openings 67 and 68 are formed fto favor an ingoing flow. Thus, a circulating flow will be established tending to ncrease the lift on the one hand by reason of 'the fact mentioned above, that blowing air ,lout as well as sucking it in produces a smoother flow above the wing with a resultings such as previously `described maybe Fig. 13 shows a modification in which movable vanes 71 and 72 are connected to the in such a manner that when the flap 5 is lowered, as shown in the figure,l the vanes 71 and 72 are opened' to permit Jair exit through 2, 3 and 4. The vanes 71 and,72 are mounted on pivots 73 and 74 respectively, and through a lever 75 and a Vrod 76, the motions of the Hap are transmitted to a lever 77 which swings about a pivot 78 on the body of the airfoil. The lever 77 controls the -motion of the vane 72 through a'link 79, also it acts on a bell crank 80 pivoted at 82 through a rod 81, which controls the motion of the vane 71. When the iap 5 is brought shutter control of substantial construction and positive operation. j
Fig. `14 shows an airfoil section similar to that shown in Fig. 1, provided with a flap 5 of the sliding type, as previously mentioned in connection with Fig. 2. This combines the advantages of the boundary layer control` with those of rflap control with the resulting increase of lift. l
The flap arrangements shown in Figs. 3, 4, 6 and 13, or other. types of flap may be used for lateral control and, when so used, the
flaps are. preferably so connected that thel movementslof the flap or iiaps on the starboard side are reverse to that of the flap or flaps on the port side. Any of the usual types of control may be used, a suitable con'- trol being illustrated in Fig. 15 of the drawings in which theflaps 5 are connected to torsion tubes 90 and 91, which carry bevel gears 92 and 93 at their inner ends which mesh with a'bevel gear 94 to which an operatinglever 95 it attached, so that movement of the lever`95 causes one flap to swing upwardly and the other downwardly.
`In Fig. 3 of the drawings, there is illustrated a further means of lateral control which may be usedindependently of the Hap or aileron control, or in addition to the flap or aileron control to increase the responsive ness. This lateral control device comprises a buttery shutter 85A pivoted at 86 and o erated by means of a suitable handle 8 to regulate the flow of air through the body of the airfoil. As the shutter 85 of a wing is moved toward closed position, the lift o n the wing is reduced so thaft lateral control may be obtained without adjusting the -angle of the aileron or flap.
It is to be understood that the butterfly sh utters for lateral control may be employed in connection with an intake such as shown in F ig. 1 and other modifications herein shown, the position of the'shutte'rs in each case determining the amount of lift on the particular wing in which the shutter is mounted. l
It will thus be seen that I have provided advantageous and simple means to control the How of air surrounding airfoils whereby greater lift can be obtained with a given wing area without the assistance lof an accessory pumping plant to provide compressed air j or to draw air froml the suction side of air.-
Furthermore, it is to be 'understood that the various modifications shown andy described, and the particular procedure set forth, are presented for purposes of explanation and lillustration and that various modif fications of said apparatus and procedure can be made without departing from my 1nvention as dened inthe appended claims.
-VVhatIclaimis: .A j V 1. An airfoil having a flap adjacent its rear edge and adaptedzto be positioned at an angle to the ai'rfoil, and means for transferring air from a point on the airfoil surface adjacent the vertex of the angle between said airfoil Itending forwardly through the airfoil and connecting the high pressure side near the vertex of the angle betweenthe airfoil and flap to low pressure regions on the upper side of the airfoil.
3. A hollow airfoil having amovable flap along its rear edge, and means controlled by movements of the flap for establishing communication through the interior of the airfoil between the high pressure region of the pressure side of said airfoil adj acentthe flap to the low pressure regions on the suction side of the airfoil forwardly of said high pressure region. f
4. An airfoil having an angularly movable Hap extending. along the span adjacent the rear edge thereof, a passage extending forwardly through the airfoil connecting the high pressure region on the pressure side of said airfoil adjacent the flap to the low pressure regions on the suc-tion side of the airfoil, means connected to the flap for simultaneous V4movement therewith for controlling said passage.
5. An aeroplane having hollow wings provided with independently movable aps extending lengthwise thereof along their rear ledges, and means vc-ontrolled by'movements ysides of said wings adj acentthe flaps and the A low pressure regions on lthe suction sides of` the wingsu v t 6. A hollowl airfoil, meansfor collecting air within the airfoil, andparallel longitudinally extending shutters arranged one in advance of anotherand forming a part of the airfoil on the suction -side thereof. 7 A hollow airfoil having a flap connected Lthereto and adapted to project downwardly and rearwardlyat an' angle to the airfoil, an
air passage connecting the interior of the airfoil tothe pressure side of the airfoil forwardly of the flap adjacent the vertex of the angle between the airfoil and flap and an outlet passage connecting the interior of the air foil to the suction side thereof forwardly of the first mentioned passage.
8. A hollow airfoil having af flap adapted to project downwardly and rearwardly at Y an angle thereto, a Ipassage connecting the interior of the air foil to the-pressure side of 'theairfoil forwardly of the ap adjacent the vertex, of the anglev between the airfoil and flap, an outlet passage connecting the interior of the airfoil to the suction side thereof for-- wardlyof the irst mentionedipassage, and adjustable shutters controlling the iow of air through the airfeil.
9. A hollow airfoil having an adjust-able flap extending alongtherear edge thereoz and adapted to be positioned at a downward inclination with respect to the airfoil, an
inlet passage leading from the pressure side of the airfoil to the interior thereof adjacent the flap and forwardly thereof, outlet passages from the interior of the airfoil to the suction side thereof forwardly ot the first mentioned passage, and shutters for controlling the flow of air through said passages.y
10. A. hollow airfoil having a flap extending along its rear edge and adjustable to a downwardly7 inclined position with respect to the air foil and means including air passages in the air foil for transferring air Jforwardly through the interior of the 'airfoil 'from the part of the airoil surface adjacent the vertex of the angle between said airfoil and iap to the suction side of the airfoil.
1l. An aeroplane having hollow port and starboard wings, said wings having perforated wall-s on the suction sides thereof, a flap at the rear edge of each wing, and inlet openings to the pressure sides of the wings along the rear edges thereof adjacent said flaps.
12.4 An aeroplane having hollow port and starboard wings provided with perforated v walls on the suction sides thereof, each wing having an adjustable Hap extending along the rear edge thereof, means for adjusting the flaps with the movement of one flap reverse to that of the other, and inlet openings to the pressure sides of the wings along the rear edges thereof adj acent] the flaps.
In testimony whereof I aiix my signature.