US2503585A - Lift control for aircraft - Google Patents

Description

April 1950 A. c. LOEDDING 1 2,503,585

LIFT CONTROL FOR AIRCRAFT Filed April 18, 1945 c NORM/9L LIFT M/B 7/;- f L w I MVGLE or ATTACK -w Patented Apr. 11, 1950 Z,5t3.5t

UNITED STATES PATENT OFFICE LIFT CONTROL FOR AIRCRAFT Alfred C. Loedding, Dayton, Ohio Application April 18, 1945, Serial No. 588,938

2 Claims. (Cl. 244-42) This invention relates to a lift control for an airfoil and more particularly to a device that may be adjusted to change the effective lift of an airfoil.

An object of this invention is to provide an attachment for an airfoil, which attachment is adjustably mounted to thereby control the effectiveness of the airfoil by spoiling in various degrees the smooth flow of the air currents in the proximity of an airfoil.

Another object of this invention is to provide an adjustable lift control device extending along at least a portion of the leading edge of an airfoil, such as the wing of an airplane, which device may be adjusted into position so as to lengthen the effective size of the airfoil to increase the lift or it may be adjusted into a position to stabilize the lift for use while cruising or it may be adjusted into a position to stall the effectiveness of the lift.

Another object of this invention is to provide a device whereby the characteristic of the liftangle attack curve may be altered at the will of the pilot.

Another object of this invention is to provide a lift control that may be attached to the airfoil of now existing aircraft so that the lift characteristic of the aircraft may be adjusted at the will of the pilot to satisfy various conditions of flight.

Other objects and advantages reside in the construction of parts, the combination thereof and the mode of operation, as will become more apparent from the following description.

Referring to the drawings, Figure 1 is a schematic top plan view of an airplane showing the lift control device.

Figure 2 is a fragmentary cross sectional view of an airfoil and a cross sectional view of the lift control attachment taken substantially on the line 2-2 of Figure 1.

Figure 3 is a cross sectional view of an airfoil showing a lift control built into the airfoil.

Figure 4 is another cross sectional View of an airfoil showin another modification of a lift control device built into the leading edge of the airfoil.

Figure, 5 is another modification, showing a lift control device that may be projected out through th leading edge of an airfoil, to thereby control the lift of the airfoil.

Figure 6 is a lift angle of attack curve, showing the characteristic of the lift of an airfoil as influenced by the lift control device.

Figure '7 is another fragmentary cross sectional view taken substantially on the line l'! of Fi ure 1 to show the control mechanism for actuating the lift control device.

Figure 8 is another fragmentary cross sectional view disclosing another modification of a lift control device.

It seems that according to the theory of aerodynamics as now understood, there are at least two factors influencing the lift of an airfoil. On of these is the pressure created on the underside of the airfoil, which may account for twenty-five to thirty-three percent of the lift of the aircraft, this being a relative value and is influenced by various factors influencing the operation of the airfoil. Another factor that influences the lift of an airfoil is the flow of the air parallel to the upper surface of the airfoil. If the airfoil is properly designed and the flow of air is not spoiled, this force may account for sixty-seven to seventy-five percent of the lift of the airfoil. This lift is generally referred to as resulting from Bernoullis Theorem. This may be put into the following very general equation PV=Q, where P represents the pressure, V the velocity of the airstream and Q the energy. This equation omits a number of factors that are not deemed necessary to be set forth at this time. The energy, according to Bernoullis Theorem, remains the same. If the energy remains the same and the velocity increases, obviously the pressure must decrease. By obtaining a high velocity air stream flowing parallel to the wing surface without turbulence and Without eddy currents, the air pressure upon the upper side of the wing can be made to approach zero. As soon as the smooth air fiow over the top of the airfoil is disturbed, the velocity parallel to the airfoil is reduced, thereby increasin the air pressure resulting in a reduction in the airfoil lift. This theory is utilized in the device disclosed herein to control the lift of the airfoil.

The formation of ice on the leading edge of an airplane quickly -destroys the lift of the aircraft by disturbing the air stream over'the top of the "wing or airfoil. It is not: the weight of the ice that causesthe airplane to fail. It is the disturbance of the air flow that causes a crack-up. Airplanes have been equipped with what is sometimes referred to as spoilers on the leading edge of the wing; but these spoilers have been fixed. They have not been adjustably mounted. The device disclosed herein utilizes an adjustable lift control extending along at least a portion of the leading edge of the airfoil, as will airfoil. each of the ,modifications, the lift control :has

3 appear more fully from the detailed description that follows.

Attempts have been made to adjust the lift on thin airfoils by providing an airfoil wherein the entire forward portion is adjustable. The length of the airfoil, as measured along the line of intersection of a transverse plane intersecting the airfoil, greatly exceeds the thickness of the airfoil. The effective lift of the adjustable portion of the prior. adjustable airfoils constitutes .a large percentage of the total lift of the entire airfoil. The adjustment of such an airfoil presents numerous problems in that the forces required to adjust such an airfoil are extremelygreahresulting in numerous mechanical difhculties.

In the preferred embodiment andin each of the modifications the lift control :is. confined to the leading edge of the airfoil. This lift control is located in the area of the airfoil that'develops a small percentage of the total lift of the entire In the 1 preferred embodiment zand in been limited to a zone .thatisvery small. The

-length1of the airfoil, as measuredialongthe line of intersection-of atransverse plane intersecting the air foil, is much less thanthe anaximum thickness ofq-the airfoil. This. results ,in-easy control of the airfoil.

If it is foundadesir-ableto spoil thelift. of the airfoil, only a slightupward movementpfthe ..lift control will cause eddy currentsdeveloping at the leading edge. of .the airfoil. -Itis acharacteristic of .airfoils that ,if. eddy. currentsstart at the leading edge, the .airpassing. overthe airfoil will .be turbulent along the entire .top.edge-of -the, airfoil. For examplait hasbeen-foundthat a small rivet head. .on the. surface. of the. airfoil will start eddy .currents, resulting in. irregular flow of air tolthe rear of the, rivet. over theentire surface located .to .the rear of the .rivet .head. 'This clearly demonstrates that a small adjustable spoiler will greatlyi'educe'the..lift on theupper side of an airfoil. It is.not.necessary to adjust or change the contourof a larger portion .or zone along the leading edge of the airfoil.

Referring to the drawings, the reference character indicates the fuselage of an airplanehaving a pair of wings if provided along the leading edge thereof with a lift control l4.

As may best be seen by referring to Figure 2.; the wing i2 is provided with anextension 16 along the leading edge that may support-a-tubular-member 18 having fixedly attached thereto a pair of deflecting plates 29 and '22 T that '00- "operate to form a-sharpedged lift controlassembly. The tubular-member 18 is adjustably mounted in an arcuateportion formed by:mem-

.ber 16, which-may be attached to .the..leading :edge of a conventional airfoil.

.As clearlyshown in Figure.2, this'lift control wassembly-mayzbe in;the'position A or adjusted into the position B or adjustedinto theposition C or. in'aanyzgnumber of :other :positions': between trolisadjusted into; a. positionrsuitable .for cruising. -When vthe lift .controlassembly is .in .the

.position .3, the lift of the wing or :air'foil is slightly more than .sufiicient-tomaintain the aircraft ataconstantaltitude. TUnder this-condition, assudden.changeofangle of. attack would cause a rise. In ascending and at any other time more lift than what is required. This setting B would tend to reduce serious increase in loads on the air frame and vertical displacements of the aircraft that may cause serious discomfort onthe partof the occupants and heavy concentrated cargo loads of freight on cargo airplanes.

By adjusting the lift control so that the lift is merely sufiicient to sustain the load, maximum efficiency as far as power is concerned is then obtained. If the lift of the airfoil is excessive, other forces are required to counteract the ex- ICSSSlVGtllfl), thereby reducing the efficiency of the aircraft. The shifting'of thezairplane from one level tolanother eventually results in aloss of energy and thereby loss of efliciency. -\When 1 the lift. control=is1in the. positionmB; itpresents a sharp leading' edge that:increases efficiency of the airfoil over a similar. airfoilihaving a blunt leading edge. Due .to thesharpnesathe effect of drag, due to compressibilityat-high speeds,

is reduced.

.In landing, the lift control is adjustedrinto the position C. The lift control remains-in thisposi- .tion until the pilotlevels off, when thelift control should be adjusted into the'position A. This should take placewhen the .elevatorsrare brought unto full up position, that is, the stick isbrought to the rear. Asa matter -of.;fact,:themaximum couldbe provided whereby the raislngof-the'ele- 'vators to the full "up position automatically raises the lift control into'the A position. LBy

. raising the lift rcontrol into lthene position-- while the airplaneisroff the'groundpalarge increased drag is :created 'due to the stall. This will'cause a very short run effecting a spot landingy-whic'h would be necessary with aircraft carriers, et

cetera. The descriptionof the adjustment of the 'lif-tcontrol in the C position for'landing takes care of normal atmospheric landing conditions.

If the air conditions aregusty or bumpy-the lift control would remain in position B, adjusted *so as to provide :just sufficient liftso as to'get a very high degree of lateral stability. The overall lift in this position will be less; but due to the high wind velocities under such conditions, the relative ground speed will still be low. Again,

when the pilot levels off and'raises the elevators to the full up position, the lift controlis raised into the A position, was to create'a stall, thereby shortening the run.

The lift control assembly may be provided with .an arm or extension .30, as shown;in Figure 7, connected to:.a link ,32, having its 1 opposite end connected toa lever 34. .Thislever'34.is pivotally attached to a; suitable isupportlat' 36. fTheihandle "38 is.lov.zered,:.the. lift controllis. raised so as to reduce the lift of the wing or airfoil. ;If .the handle 38 is raised, .the .lift of the wing .is in- .From this ,curveit can bereadilyseenthat when the lift control. assembly is in the .positionJB, the curvelevels off,..as.indicated hy.thehorizontal lineB in'Figure 6. Whenthe lift control is in weather.

Furthermore, the cylindrical or tubular member l8 may be used as a passage for exhaust gases and thereby the lift control assembly may be used as a defroster. The exhaust gases need not necessarily be confined to the tubular member. The

exhaust gases may also flow between members '20 and 22, so as to supply heat to a tip of the lift control assembly, thereby melting the ice where it would first form, in the absence of a defrosting device. Furthermore, the lift control assembly, if exhaust gases are not used, may house an electrical heating element for supplying heat to the lift control assembly, which heater element functions as a defroster.

As clearly seen in Figure 1, the lift control device does not extend throughout the entire length of the leading edge of the wing or airfoil. The length of the lift control depends upon the design of the wing or airfoil. It depends upon the effectiveness of the design. It depends upon the purpose for which the aircraft is to be used, the type of load, flying conditions, of, oetera. The length of the lift control is a matter of choice, depending upon the purpose of the aircraft. Likewise, the size is a matter of choice. It need not be very large. Rivet heads have been found to reduce the lift by creating eddy currents across the upper surface of an airplane wing. Thus, it is readily seen that the lift control may be quite small.

In the modification disclosed in Figure 3, the lift control has been built into the leading edge of the wing or airfoil 40. The leading edge of the wing 40 has been provided with an arcuate a cavity 42 that receives a tubular member 44. Member 44 is adjustably mounted in the cavity 42, so as to prevent oscillation of member 44 about the longitudinal axis thereof. A pair of members 46 and 48 extend forwardly from the tubular member 44, so as to provide a sharp edge extending along at least a portion of the leading edge of the airfoil. The lift control assembly may be raised or lowered in a manner similar to that described in connection with Figure 2.

In the modification disclosed in Figure 4, the airfoil 50 has been provided with a longitudinally extending recess 52. One side 52a of this recess is arcuate and the other side 52b is straight. A lift control member is provided with a curved surface 6211, that has a radius of curvature compatible to the radius of curvature of the adjacent airfoil, a curved surface 52b and a straight surface 620. Member 60 is pivotally mounted at $4 to the airfoil 5E] and may be oscillated about the pivot 64 so as to be in the full line position B shown in Figure 4 or raised into the dotted position A, or the dot-dash position C.

The full line position B may be referred to as the cruising lift control position. The dotted position A may be referred to as the stalling position and the dot-dash position C may be referred to as the ascending or lifting position.

In the modification disclosed in Figure 5, a lift control 10 is mounted in a suitable slot 12 in the leading edge of the airfoil and is mounted for reciprocatory movement. When member 10 is withdrawn into the airfoil, the airfoil operates as a normal airfoil without a lift control. When member 10 is projected through the slot 72 so as to extend beyond the airfoil, member if! functions as a spoiler to reduce the lift of the airfoil.

Member in may be controlled in any suitable manner. I

Although the control shown in Figure 7 and described in connection with the preferred embodiment shown in Figures 1 and 2 is manually controlled, the lift control may be automatically controlled, especially when flying through stormy weather. For example, a sudden increase in temperature along the leading edge may operate a suitable thermostatic control mechanism to raise the lift control soas to reduce the lifting power of the airfoil. Such warm air currents are in all probability the result of upwardly directed air streams intersecting the path of the airplane. In order to counteract the rising air currents, the lift of the airfoil is reduced, so as to maintain the course of the airplane on an even level.

In Figure 8 another lift control mechanism has been shown. The airfoil has been shown in dotted lines and has attached thereto an adjustable fiap 82 adjustably attached to the airfoil 80 by a hinge 84. Member 82 carries at its leading edge a second flap 86 pivoted at 88 and slidingly engaging the airfoil 88. Members 82 and 86 cooperate to form a lift control. This lift con trol may be adjusted into the A position, when it functions as a spoiler, and into the 0 position, both shown in dotted lines.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention, I claim:

1. A lift control assembly for use on an airplane having wings provided with a leading edge that is curved, said lift control assembly including an extension having an arcuate recess extending parallel to the front edge of the wing, said extension being mounted along the leading edge of the wing and being provided with a curvature merging into the curvature of the wing, a tubular member rotatably supported in the arcuate recess, and a pair of deflecting plates fixedly attached to the tubular member, said deflecting plates cooperating to form a sharp lift control edge so that when the tubular member is rotated so as to adjust the deflecting plates into a position whereby the effective length of the upper surface of the wing is increased, the lift of the wing is increased; when the tubular member is adjusted into a position whereby the edge formed by the deflecting plates is directed slightly upwardly so that the upper plate forms a well defined angle with the upper surface of the wing, a drag is created; and when the tubular member is adjusted into a selected position between the aforementioned .pOSltiOliS, the lift of the wing may be such that its lift is slightly more than sufficient to maintain the airplane at a constant altitude.

2. A lift control assembly for use on an airplane having wings provided with a leading edge that is curved, said lift control assembly including an extension having an arcuate recess extending 'parallelito thefront edgecf the wing-said extension beingmounted alongg theleading: edge of: the

wing" and being provided" witha curvature-merging into the curvature off the-wing, a cylindrical memberrotatably supported in:.the:arcuate recess, a :pair of deflecting platesfixedly' attached to: the cylindrical member;v saiddeflecting platescooperating: to form asharpliftcontrol edge, and .means for adjusting the cylindrical member so that the deflecting plates may bexadjustedinto'position whereby the effective length of the-iupper surfaceof the wing is increasedito thereby'increase the lift ofthe wing; the'deflecting plates may be adjusted by said adjusting means into another position whereby the edge formed by the deflecting platesis directed slightly upwardlyso that theupper plate forms a-well definedangle with the upper surface of the" wing to thereby create a drag; and the deflecting plates may be adjusted into position by said adjustable means 0 intermediate theaforementionedmositions; which position is selectedto-create a lift-of. thawing suchathat theeliftiiswslightly more than sufficient to-maintain the airplane at aconstant altitude.

ALFRED C. LOEDDING;

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

UNITED STATES PATENTS Number- Name Date 1,631,259 Gilmore June 7,1927 1,775,757- Gay Sept-16, .1930 1,815,489 Alberset al. vJu1y 21, 1931 1,856,219 Langel- May 3, 1932 1,858,259 Alfaro .May 17, 1932 1,880,019 Harper Sept. 27,1932 2,026,482 Mattioli Dec. 31, 1935 2,037,626 Hall. .Apr. 14, 1936 FOREIGN PATENTS Numhen Country, Datev 446,094 Great.Britain. oApr. 20; .1936

Images