US2104006A - Airplane - Google Patents

Description

Jan. 4, 1938 J. WK, BALLOU 2,104,006

AIRPLANE Filed June 30, 1933 3 Sheets-Sheet 1 VINVENTOR Jan. 4, 1938. J MCK. BALLOU 2,104,006

A I RPLANE Filed June 50, 1953 s Sheets-Sheet 2 IIG.5

3916.10 INVENTOR- WM ("101(- BQMML.

Jan. 4, 1938. ,1, McK. BALLOU 2,104,006

AIRPLANE Filed June 30, 1953 5 Sheets-Sheet 3 IT IS 84. 8

we! INVENTOR WAM 64mm :EI G- 1.4;

Patented Jan. 4, 1938 j UNITED STATES PATENT OFFICE,

AIRPLANE John McK. Ballou, Los Angeles, Calif. Application June 30, 1933, Serial No. 678,368

7 Claims.

This invention relates to airplanes in general,.

and more particularly to the class of airplanes equipped with lift increasing devices.

I am aware that others have constructed airplanes wherein devices have been incorporated for the purpose of increasing the maximum lift coefficient of the airplane, with varying degrees of success. Many devices have been suggested heretofore, which, when actively associated with the wings of airplanes, increase the combined will serve to familiarize anyone skilled in the art with the general nature of this class of device. There have been certain cases where airplanes have been constructed according to some of the above as well as other designs of like nature that have been well known for their excellent performance.

However, up to the present, the most satisfactory means for availing oneself of the full benefits to be derived from devices of this class had remained undiscovered, so far as applicant is aware, and will be revealed hereinafter.

I myself, as Well as others have heretofore constructed highly successful airplanes equipped with longitudinal control means, operative thru the agency of adjusting the angle of incidence of the primary sustentation members or wings; in other language, wherein variations in the angle between the longitudinal axis of the fuselage and the trace of the plane of the'wing chord on a vertical plane thru this longitudinal axis, are utilized for varying the lift coefficient of the wings, entirely independent of the presence or absence of any aerodynamic surfaces in the tailsof the air planes. Examples of such art have become known in United States Patents Numbers 1,856,093,

' 1,889,864 and 1,931,809.

However, all of the art up to, the present time lacks something that impairs its perfection. The criterion in judging wing profiles that is regarded as of paramount importance is a combination of high maximum lift coefficient with low minimum profile drag. There is no known profile, and it seems improbable at the present time that a profile will soon be discovered, of constant geometric properties capable of combining very high values of maximum lift coefficient with very low values of minimum profile drag. This places a limitation on airplanes designed with constant profile wings, even of the class wherein longitudinal control is accomplished by incidence adjustment, in spite of the otherwise excellent character of such airplanes,- combining asthey are well known to do, high efficiency, exceptional safety, and unusual ease of operation. Wings suitable for airplanes of this adjustable incidence nature, that are conducive to stable equilibrium of the airplane at any position of adjustment, have usually, by good fortune, a very low profile drag, but, unfortunately, none areknown at the present time whose maximum lift coefiicient attains very high values. On the other hand, there are known profiles having fairly high lift coefficients, but again, they are defective in having also a high value of minimum profile drag, as

' well as being impairedby possessing an excessive center of pressure travel between their low angle of attack condition and their high angle of attack condition, their centers of pressure being located far back away from the leading edge in the low angle condition, and fairly well forward in the high angle condition. This seriously handicaps them by requiring a heavy down load on the tail when an airplane employing a wing of such profile is in its cruising attitude, thereby inducing an unnecessary drag when it' is most detrimental, and directly detracting from the pay load for any specific wing area, besides requiring a heavy structure to support the excessive internal loads. Even the best of the commonly used high lift profiles have lower values of maximum lift coefficient than are to be found in profiles modified bylift augmenters.

Heretofore, airplanes employing lift augmenters have been handicapped both in their safety character, and in their full efliciency by constructions based on a lack of appreciation of certainaerodynamic facts, recognition of which has enabled the present invention to overcome the imperfections, inefficiencies, and limitations of airplanes wherein an endeavor has been made to gain the benefit of lift augmenters. 1

It is an object of this invention to construct an airplane employing a lift augmenter, maintainedmovable for roll control.

' lished angle of attack either with or without the liftaugmenter being in action, the airplane will fly in stable equilibrium.

Other objects will appear from consideration of the ensuing description and reference to theannexed drawings, wherein:

Fig. 1 is a side elevation of an embodiment of. theinvention.

Fig. 2 is a side elevation of a wing of profile adaptable to the exercise of this invention.

Fig. 3 is a side elevation of the wing of Fig. 2, but provided with a trailing edge flap deflected down.

Fig. 4 is a diagram showing an analysis of forces acting on a wing of the profile shown in Fig. 2.

Fig. 5 is a diagram showing an analysis of forces acting on the wing of Fig. 3.

Fig. 6 is a diagram showing an analysis of forces acting on the wing of Fig. 2, modified at high angle of attack by deflecting the flap down as in Fig. 3.

Fig. 7 is a diagram showing the contour of a median line suitable for wings used in this invention.

Fig. 8 is a diagram showing two positions of flight of an airplane built according to this invention.

Fig. 9 is a view of a mechanism for carrying out the invention.

Fig. 1015 a diagram of a controlsystem adaptable to this invention.

Fig. 11 is a fragmentary illustration of a fixedwing adaptation of the invention, wherein longitudinal control is obtained by shifting the location of the center of gravity.

Fig. 12 is a fragmentary illustration of a fixedwing adaptation wherein longitudinal control is obtained by an elevator in the tail.

Fig. 13 is a detail illustration of certain elements of Fig. 12, and

Fig. 14 is a detail of another element of Fig. 12.

In Fig. 1, an airplane is shown comprising, a fuselage or body I, upon which is secured by familiar means a chassis 2, a stabilizer 3, an elevator 4, a fin 5, a rudder 6, atail skid I, a power plant 8, and a propeller 9. A wing I ii is supported to body I by right and left front strut-s ii, equipped with pivotal supports I2 for angle of incidence adjustment. The wing I0 may be continuous across the body I, or may be in right and left panels, which may, if desired, be differentially Rear right and left struts I3 are vertically movable thru themedium of any suitable mechanism, such for example as that to be discussed hereinafter under Fig. 10.

These rear struts I3 pass thru elongated openings I4 in body I. The upper ends of struts I3 terminate in rock joints I5 in wing Ill; and thus, the angle of incidence of wing I I) is adjustable by raising and lowering rear struts I3. The rear section I6 of wing III is separate from, and swingably mounted on wing III by hinges II, thereby constituting what is commonly known as a trailing edge flap. It is at once apparent that in place of the trailing edge flap shown in Fig. 1, any one of a number of well known devices could as well be associated with wing I0. These devices come under the general classification of lift augmenters. Familiar examples in addition to those already suggested hereinbefore would include the Handley Page slots and flaps.

However, the common trailing edge flap as shown in Figs. 1, 2, 3, and 9 is readily constructed, and is useful in obtaining the results to be disclosed forthwith, but it should be clearly borne in mind that this invention is not restricted to any specific lift augmenter, and is adaptable to. the

operationof the generic device designated as the. lift augmenter. Flaps I! are swingably mounted on shafts II in hinges i1, and areactuated by cranks IO equipped with pins 20, constrained to follow a definite path, as will be explained later, by the contour of cam slots 2i on body I. In Fig. 1, stabilizer 3 is immovably secured to body i, and elevator 4 is swingably secured to stabilizer 3 by means of shaft 22 and hinges 23. This arrangement is entirely satisfactory for certain embodiments of the invention, whereas for others, it is preferable to separate the right and left panels of the elevator 4, interposing stabilizer 3 between the right and left panels of the elevator 4, and constructing the elevator 4 as a spanwise continuation of stabilizer 3 when in a neutral position of adjustment, but with the right and left panels of elevator 4 synchronously movable in the same direction independently of stabilizer 3,

which itself may be swingable under certain circumstances as will be disclosed hereinafter under Fig. 10. No drawing is offered here to illustrate the above described construction of the elevator spraddling the stabilizer, as it is not diflicult to visualize from the preceding description assisted by the drawings as they stand.

A very important fact now presents itself. It is well known that lift augmenters have what has heretofore been regarded'as detrimentalcharacteristics, namely, they have a tendency to move the center of pressure toward the rearat high angles of attack as well as at low angles of attack, and the lift/drag ratio is lower than. that ofthe corresponding profile when the lift augmenter is in its inactive position. Also, the center of presservice, and the last named is precluded as will be described 'i'orthwith. A mechanical device maintains the lift augmenter in its inactive position at low angles of attack. In Fig. 2, a wing Iii is flying at a low angle of attack WL, the wing chord 24 forming a relatively small acute angle W1. with the flight path P. The lift augmenter I6 is in its neutral or inactive position, and wing chord 24 is a continuous, unbroken line from leading edge 26 to trailing edge 38.

In Fig. 3 the same profile is shown at a larger angle of attack, that is, with the chord 24 forming a relatively large acute angle Wn with the flight path P. Lift augmenter I6 is here shown in its operative position, its chord 25 inclined at an angle F to the wing chord 24.

Before proceeding to describe the mechanical means for causing the lift augmenter I6 to assume its neutral position at low angles of attack and its active position at high angleof attack,

a discussion of the nature 'of the forces acting on the airplane will be offered.

The passage thru the air of an aerodynamic surface sets up certain reactions to its motion Ill) thru the air. An airfoil of a certain profile when 7 tion. For convenience in the study of aerody-- namics, this reaction is' commonly analyzed into two components, one perpendicular to the path relative'to' the air, and designated lift, the other i parallel to this path and designated drag. The

inclination'of the line of action of the resultant reaction to this path is equalto' tan- L/D, where L and D represent simultaneous values of lift and drag respectively. The inclination of this line of action to the wing chord is equal to tans- L/D+W, where W is the angle of attack.

The line of action, inclined thus, intersects thechord'of a wing at thecenter of pressure existent at the instant that the'sald simultaneous values oflift and drag are existent. In Fig. 4 a diagram is shown, indicating the various lines of action of aerodynamic reactions existing at various angles of attack; thus, the line designated 1 represents the direction and location of the line of action of the reaction existent when the wing is flying at 1 angle of attack. In 'Fig. 4, the chord 24 is shown.but the envelope profile, as shown in Figs. 2 and 3 is eliminatedfor the sake of avoiding confusion by the presence of too many lines. The intersection of any line of action, 1, 6, etc., with chord 24 is known as the center of pressure for the corresponding angle of attack. Such a diagram as that of Fig. 4 is best prepared by calculating the center of pressure location and the inclination of the corresponding line of action for each angle of attack that is to be investigated,

using data obtained from a, model, tested in the Wind tunnel, and then drawing a line, inclined at the calculated inclination thru the calculated point of location of the center of pressure. In view of the fact that the technique of operating the wind tunnel is 'well known to those skilled in the art, no discussion of it will be included here.

It will be noted that beginning a short distance below chord 24, and extending as far down as the diagram is shown in Fig. 4, these lines of action progress consecutively from front to rear as the angle of attack is increased. If the center of gravity of the airplane be located on any line of action, and within the said region or zone below chord 24 in Fig. 4, the airplane will be in stable equilibrium as is well known to those skilled in the art. A symmetrical profile having the character shown in Fig. 4 may be prepared by proportioning its ordinates according to the equation:

as is well known to those skilled in the art. The profile shown in Fig. 2, and having the diagram of Fig. 4 is constructed from the above equation, but scaled down in, thickness so that it has a maximum ordinate of 16%. or a 12% thi kness at its thickest point, which occurs at 30% of the chord back from the leading edge 26. In the diagrams of Figs. 4, 5, 6, and 8, the wing chord 24 is shown with its leading edge 26 indicated by arrow points. An airplane constructed with a wing profile of the class just described, pivotally mounted for incidence adjustment is fully controllable, and at any adjusted angle of incidence,

it will-persist in flying in stable equilibrium at a definite angle of attack, as is well known to those I shown at 25 in Fig. 5, then the diagram shown in Fig. 4 ceases to exist, and a diagram of entirely different nature shows the character of the so modified'profile. Here, the lines of action 0, 4,

etc.', for an appreciable distahce below the chord 24 progress from, rear to front as the angle of attack is 'increasedin the low'angle range, and

then, some distance below chord 24, they cross would not produce an airplane that could ever be in stable equilibrium, particularly with the center of gravity located on a line of action for less than 12, and especially if the center, of gravity were located up near the chord 24. Now, if the flap it of Fig. -3, deflected down at the angle F to the chord 24 were permitted to remain at the angle F, while the wing in attained av low angle of attack, such as W1. of Fig. 2. then such lines of action as -2, 0, 2, 4, etc., of Fig. '5 could come into existence. This is a serious imperfection in an airplane employing a lift augmenter, and wherein longitudinal control is effected thru the agency of deflecting a horizontal tail surface as the exclusive means, while the wing in such an airplane is of the rigid type with respect to the body of the airplane. This is especially true, if as has commonly been the case in prior constructions, the lift augmenter I 6 is controlled by means of an independent manual means, for, even tho a wing having a concentrated center of pressure location such as that augmenter and stabilizer, increasing the deflection of the lift augmenter gradually while at the same time gradually inclining the stabilizer from its minimum position to its maximum position, most of the valuable diagram of Fig. 4 is lost.

In Fig. 6 there is a diagram showing the combined nature of a wing of the character shown in Fig. 4 wherein a lift augmenter, represented by its chord line 25 is maintained in neutral relation to the wing, represented by its chord line 24, thruout the low and medium angle of attack range,

and yet is brought into positions of successively greater effectiveness as the maximum angle of attack is approached. Here, the chord 25 of the lift augmenter [6 of Fig. 2. hinged at l8 to the wing chord 24 is maintained in rectilinear relation to wing chord 24 while wing chord 24 is tipped about pivot [2 to vary its angle of attack from 1 to 14. The center of gravity of the airplane, C. G. lies on are 21 and can be located on any desired line of action such as 2 as shown, by adjusting the angle of incidence of the wing chord 24 about pivot l2. The center of gravity C. G., having been located by adjustment onany desired line of action, the airplane as a whole takes up'a posi-' tion relative to its path with reference to the air, such that the wing chord 24 is inclined to the path at the corresponding angle, for example, 2 as shown in Fig. 6. The airplane will now persist in fiying at the angle of attack selected, because, as hereinbeforc stated, the airplane is in stable equilibrium at that angle of attack. When the 14? incidence is exceeded, mechanism provided will automatically deflect flap chord 25. Thus, at 16 angle of incidence flap chord assumes position A, and the line of action for this combination is 16a. Further increase in incidence to 18 deflects flap chord 25 to position B, and at the same time shifts the relative position of the center of gravity C. G. along arc 21 to a position on the newly created line of action 1812. In designing this airplane, care is exercised to locate the fore and aft position of pivot I 2 on wing Ill, and the height of pivot l2 above the center of gravity C. G. of the complete airplane so that the angle of incidence change to move the center of gravity C. G. relative to the wing chord 24 is equal to, or at least nearly equal to the angle of attack change corresponding to the lines of action between which the center of gravity C. G. has been relatively moved. In Fig. 6, a combination is shown wherein further incidence change to 19 associated with the increased deflection of liftaugmenter 25 to position C, establishes line of action 19c, and the distance between line of action 18b and l9c along are 21 is practically zero, whereas the distance traversed by the center of gravity C. G. along are 21 while rotating wing chord 24 thru the difference in angle of attack in question, namely 1 would not be essentially zero. This would mean that the center of gravity would now lie to the right of line of action l9c on are 21. This brings up a new action. With the wing chord 24 and the flap chord 25 adjusted in combination to establish line of action 19c, the airplane will be out of balance, and a stalling moment will exist, because the relative location of the center of gravity C. G. will be to the right of line of action 19c. The construction that compensates for this will be discussed presently by the aid of Fig. 8.

So far, the profiles shown herein are of thesymmetrical class. Expressed otherwise, their median lines havebeen rectilinear. This is not essential, as there are many assymetrical forms that have excellent properties. An example of these could be prepared by forming a median line according to the equation:

as is well known to those skilled in the art. Figure 7 shows such a median line with the coefllcient h adjusted to bring the maximum ordinate to a value of 6% of the chord. Here, the chord 24 is used as the axis of abscissae, and the median line 28 is derived from the above equation. It will be noted that median line 28 crosses chord 24 at point 29, which is located 87.5% back from leading edge 26. To construct a wing profile according to this form, the envelope, which may be one derived from the equation on page 3, line 55, is superposed on the median line just described in a manner well understood by those skilled in the art. This invention does not necessarily feature the specific profiles just described. They are offered as definite examples to illustrate the nature of one of the features of the invention. Any profile showing a diagram similar to that of. Fig. 4 will serve as a basis for this invention, and if a test in the wind tunnel shows a profile of unknown contour to have the character of the diagram of Fig. 4, then the unknown profile would be entirely satisfactory as a nucleus for the exercise of this invention. Also, in a diagram like that of Fig. 4, the wing chord 24, and the pivot 12 of Fig. 1 may be located relative to the center of gravity C. G. of the airplane such that the center of gravity C. G. lies constantly at or approximately at Q, or a constant distance from leading edge 26 in Fig. 4, and with the assistance of the stabilizer 3 of Fig. 1, incidence variation is feasible. and yet the airplane can be maintained in stable equilibrium, because it would be in neutral equilibrium or else in a state of unbalance with a constant upsetting moment without the assistance of the stabilizer, whereas the stabilizer 3 comes into action here, not merely to restore balance as is commonly understood by those skilled in the art, but to offer a righting moment whenever the airplane departs from the angle of attack for which it has been adjusted. So long as the progression of the lines of action is not definitely from rear to front with increasing angles of attack, a practicable airplane may be constructed using variable incidence for longitudinal control.

In Fig. 8 a diagram is shown analyzing two conditions of flight of an airplane embodying this invention, namely medium angle of attack with a lift augmenter in its neutral or inactive position, and high angle of attack with the lift augmenter fully effective. In this figure, the lift augmenter 30 is a thin plate, depending from the trailing edge 3|, and perpendicular to the chord 24. The nature of a lift augmenter of this class is well known to those skilled in the art. Assume that the airplane being analyzed in Fig. 8 is flying at M angle of attack, M being well above the angle of zero lift and somewhat below the stall. Under these conditions, the airplane is following path PM relative to the air. The airplane of Fig. 8 is provided with a fixed or non-adjustable stabilizer, represented by its chord 3, its envelope being omitted from the figure. The elevator 4 of Fig. 1 is absent. When flying thus at M angle of attack, with the parts of the airplane so proportioned that the sum total of moments extraneous to those induced by the wing 24 is zero, the line of action 32 of the reaction corresponding to M then passes thru the center of gravity C. G. of the airplane. The stabilizer 3 in this case is set at its angle of attack for zero lift relative to the path Pu. The stabilizer 3, then, while the airplane is following path PM is ineffective and has little if any influence on the attitude of the airplane. Its reaction is directed parallel to path PM and backward inits direction. It could as well be absent, as the airplane is in stable equilibrium at M angle of attack as explained hereinbefore in discussing Figs. 4 and 6. The pilot now adjusts lift augmenter 30 into its effective position as shown by the dotted line 30. It should be noted here that when the airplane was flying at M angle of attack, only such lines as appear full were to be considered. Dotted line 30 was to be disregarded as though it were absent. Now, with dotted line 30 present, representing the effective presence of the lift augmenter, line of action 32 ceases to exist, and instead line of action 33 is created. Line of action 33, passing forward of center of gravity C. G. induces a stalling moment, and the airplane is momentarily out "of balance, and as a result rotates about its center of gravity C. G. until its relative path is the dotted line PH, inclined at angle 34 to old relative path PM. It may be that I PM- and PH both lie on the same line relative to the earth, or it may be that they do not. That depends upon determining factors that need not be considered here, such as engine thrust. PM might represent level flight and PH climb, or various other combinations. The stabilizer 3 has a positive angle of attack because it is positively inclined toward new path PH, and therefore its newly established reaction has a newline ofaction 35 with "tipliedby the magnitude of reaction 35. Thus,

with the assistance of stabilizer 3, the airplane is again in equilibrium. It is in stable equilibrium, because, any disturbance that causes an angular displacement of the whole airplane relative to its path will in so doing cause a new reaction on the stabilizer '3, which not only compensates for the movement of the line of action of the wing, but

overbalances it, and tends to return the airplane to the established angleof attack, as is Well known to those skilled in the art. We have in effect, with the construction disclosed in Fig. 8, at any established value of angle of attack in the high angle range, with the lift augmenter 30 in action, a conventional airplane with its stabilizer set at an excessively high-degree of decalage. With lift augmenter 30 in action, the diagram of wing reactions'is similar, to that of Fig. 5, but, as just explained, it is corrected by stabilizer 3, producing a diagram for the whole airplane that bears a resemblance to the diagramof Fig. 4. Thus, in such a construction, the lift augmenter is ineffective at'low angles of attack which are established for the airplane, and, the airplane being in stable equilibrium from the action of the wing alone,

stabilizer 3 is unessential, and merely rides in a neutral and ineffective position; but when the lift augmenter 30 is brought into use at high angles eraliy for maintaining level flight at a minimum speed, or to secure a favorable landing condition. In an ordinary airplane controlled by an elevator, in order to secure a minimum speed along the path, high angle of attack is attained by reducing or even reversing the direction of the tail load, so that it is either low, or else negative relative to that of thewing Therefore, any assistance that might be desired from the empennage in assisting in sustaining the airplane, at the time when such sustentation is most needed, must be sacrificed.

' This sacrifice may be regarded as a serious defect.

In the airplane analyzed in Fig. 8, the horizontal tail surface 31s at its most effective lifting condition at maximum established angle of attack, assisting in the attainment of extremely; low speeds for landing. This results from the greatly reduced L/D ratio with the lift augmenter in action at high angles of attack, which more than compensates for the rearward location of the.

center of pressure by causing the inclination-of the line ofaction to possess 'a relatively large forward component. This forward component becomes increasingly effective as greater distances are selected below the pivot point I2, of Figs. 1, 2, 3, and '6, for the locus of the center of gravity of the airplane. Thus, it' is clear that in the airplane analyzed in Fig. 8, not only are theadvantages hereinbefore described retained, but in addition, valuable assistance is offered by the tail to increasing the maximum lift on the airplane at high angle of attack, and at low angle of attack there is no sacrifice in the form of a down load on the tail.

In Fig. 9 two positions of a wing with a lift augmenter are shown to'elucidate the operation of one form of mechanism for the exercise of this invention. A low angle position is shown in full lines, and a high angle position is shown in dot and dash lines. A support II, such as a strutof Fig. 1, or other suitable element in a fuselage I, swingably supports a wing III about a shaft I2,

permitting it to move from a low angle position IIIL to a high angle position IOH. A mechanism, not shown here, but which might very well be that which will be explained later under Fig. 10, enables the pilot to move the wing I from IOL to IOH at will. At a suitable position forward of the trailing edge 38 of wing Ill hinges I! are provided, to support shaft I8 for swingably supporting lift augmenter I6. A crank I9-is secured to lift augmenter iii in a manner such that a constant angular relation between crank I9 and lift augmenter I6 always prevails. Crank I9 is secured preferably in rigid relation to shaft I! for this purpose, shaft I8 being an integral part of lift augmenter I6. Crank I9 terminates in pin 20, or other suitable cam follower, the design'of which is well understood by those skilled in the art. A rigid member 58 is secured to any suitable part of the structure of fuselage I in Fig. 1. Member 58 is provided with a slot 2| engaging cam follower 20. Slot 2| is formed with its center line 39 a circular are having the center of shaft I2 as its center thruout the low and medium angle of attaek range for wing I0; and departing from this circular are 39 with an increasing component of deviation toward shaft I2. The action of this device is as follows: Assume wing Ill at low angle adjustment IOL. Lift augmenter IBL,

supported by hinges "L and shaft I8L is in its neutral position, and is constrained to remain so by crank I9L, positioned by cam' follower 20L,

engaged by slot 2|. The pilot increases the angle of attack until wing I0 is at IIIH. This pushes shaft I8 down, carrying with it crank I9. Slot 2|, by its contour, constrains-follower 20 to move from 20L to 20H, bringing crank I9 to I9H, shaft I8 to 18H, and lift augmenter I6 to IBH as shown in the dot and dash lines. Thus, by a proper proportioning of slot 2|, any desired progression of lift augmenter I6, from its neutral position I6L to its fullyactive position IBH may be'obtained. For example, if it were desired to retain lift augmenter I6 in neutral until the maximum angle of attack for wing III was nearly attained, the departure from the circular arc 39 with shaft 2| as its center, would be delayed, and perhaps departing along a radius toward center 2|. When the axis of crank I9 lies near or coincident with a line joining the centers of shafts I 2 and I8, small changes in angular movement of wing III cause large angular changes in lift augmenter I6.

Fig. 10 shows a mechanical device suitable for the exercise of this invention in certain of its features. The wing I ll, pivoted at a suitable point on shaft I2 hung in support II, which may The other end of strut I3 is pivoted at 40 to hell wheel 48, rotatably retained in bracket 49,- which crank 4|, which is fulcrumed at 42 to a bracket 43 secured to any suitable portion of the structure of fuselage I, Fig. 1. The other leg of bell crank 4i is provided with slot 44 in which pin 45 is engaged. Pin 46 is secured to push-pull rod 46, threaded on one end 41 to receive threaded hand idly secured to shaft 55, articulated in bracket 56.

- on established speed. A

Bracket 56 is secured to a suitable member in the tail of fuselage I, Fig. l. Shaft 55 is an integral part of a horizontal tail surface 51. The operation is as follows: The pilot turns hand wheel 48 in a certain direction, which pulls rod 46 and pin 45, pin 45 thereby moving bell crank 4I. Slot 44 accommodates the relative vertical movement between bell crank 42 and pin 45, avoiding jamming of the parts. Forward movement of slot 44 induces upward movement of pin 49, thereby pushing strut I3 upward, and resulting in an upward shifting of the trailing edge 38 of wing III. By virtue of being pivoted at I2, the said upward movement of pivot I decreases the angle of incidence of wing Iii. Simultaneously with this action, the forward movement of rod 46 pulls fork 52 out of engagement with pin 53, allowing full free floating of flipper 51, to assume a zero lift angle of attack at all times. Key 50 sliding in slide 5| permits free axial movement of rod 46 but prevents rotation. Movement of hand wheel 49 in the opposite direction induces movement of the various parts in counterdirection, increasing the angle of incidence of wing I0, and locking flipper 51 in a fixed position. If desired, instead of such a fork as that shown at 52, some other shape could as well be made, for example, instead of the inner faces being straight lines as shown, they could be straight converging lines for a certain distance, and then their direction change so that they terminate in parallel lines of just suflicient distance of separation to constrain pin 53 against swinging movement, thus maintaining flipper 51 as a flxed surface thruout a range of angular movement of wing I0. Various contours could also be applied to the constraining member in substitution for fork 52, causing flipper 51 to assume a certain angle of attack for a certain wing setting, and other angles for other settings of wing I 0.

While nothing is shown in Fig. in the way of a lift augmenter, or operating means therefor,

it is evident that such a device as that of Fig. 9 or any other desirable device of such nature could readily be associated with the device of Fig. 10.

V In view of the fact that angle of attack variation is a means of speed control, the locking oftail surface 51 may be regarded as dependent on established speed; and also lift augmenter, ad-.

justment may be'regarded as beingdependent Many mechanical devices are useful for operating the airplane, according to this invention, and the incidence variation as well as the operation of the lift augmenter and the locking of the tail surface may be as well accomplished by pneumatic, hydraulic, or electrical means rather than by linkages or gears.

The mechanical means, however, are. immaterial, or, at least, are not meant to be stressed in detail claims, as long as it is understood that a maximum lift coefficient at a high angle of attack is the result to be obtained, and when stressing the high angle of attack it should at the same time also be clear. and understood that this is not at all necessarily to include a high angle of -incidence of the general conception.

This is perhaps best made clear by referring to a variation of general construction over what has been set forth above with reference to the illustrations of Figs. 1, 2, 3, 9 and 10.

It should be clear from what has been explained above with reference to the illustrations in Figs. 4 and 5 in particular, but also with reference to the illustrations in Figs. 6, '1, and 8 in general, that the principal feature of this invention is equally well applicable to various and distinct forms of airplane constructions.

One of such different or distinct constructions is outlined in Fig. 11, involving the well known general principle of shifting the location of the center of gravity.

In this illustration of Fig. 11, however, this otherwise well understood principle is made applicable to the principal feature of the present invention by operatively connecting the variable gravity feature to the lift augmenter control feature of the present invention.

As illustrated, the wing III of the generalcharacter of Figs. 4, 5, and 6 is here rigidly mounted on the body I of an airplane, while the augmenter being tumable by the motor 64, whereby the shifting movement of the weight is procured in such a manner as to vary the location of the center of gravity of the whole airplane on which this mechanism is provided. v

For operating this gravity control, leads 65 and 66'with the terminal contacts 61 and 68 can be brought into ,a circuit by means of the switch 69 through the leads 10, H, and 12, a battery 13 being indicated as a motive force grounded by meansof the lead 14 to the supporting member 60. Distinct and independently operating solenoids and 16 are provided to act on a common member 82, connected by link 83 to the lift augmenter I6 at 64.

While the lead 12, coming from the battery 13, connects to both solenoids 15 and 16, a separate lead 11 connects with the one solenoid 15 and another separate lead 18 connects with the other solenoid 16. The opposite end of the lead 11 connects with the contact bar 19, and the opposite endof the lead 18 connects with'the contact bar 80, a contact-making piece 8| being provided on the weight I I9 whereby the circuit is closed as the weight moves along the member. II8 through either the bar 19 or the bar 80.

The solenoid 15 is designed so that the augmenter I6 is held steadily in-neutral or inoperative position, as far as any undue lift-augmenting is concerned, as long as the circuit is closed through the bar 19; while the solenoid 16 is designed to cause a downward tilting of the'augmenter I6 whenever the circuit'is closed through bar 86. a

no. other effect than to come tobalance with A changing of the location of the center. of

gravity in the whole airplane by means of the- Another of such different and distinct con-' structions is outlined in Fig. 12, with details in Figs. 13 and 14, the illustration in Fig. 12 involving the well known general principle of longitudinal control by means of an elevator at the tail end of'the airplane, particularly involving the Handley Page slots and flaps arrangement, re- 'ferred to in lines 74 and 75, page 2-.

In Fig. 12, wing I0 is not necessarily of the specific character repeatedly described, but may be of any character, the wing being, nevertheless, rigidly mounted on the body I'. Augmenter I6 is mounted similarly as in the other forms, but in this case provided with an extension or lever portion I00 with a pin IOI,'con'nected by the rod I02 with the piston H1 in the cylinder I03, mounted on the support I04, the rod having collars H0 and III for actuating the shutter I08 by means of the portion I09. The shutter I08 serves to control a leading-edge slot-I01 in the wing I0. A spring H6 is inserted in the cylinder to counteract on the piston when the pressure is released for returning the piston to neutral position.

.An elevator 4 is swingably mounted in the tail end of the airplane on a shaft 22,-which is in this case provided with a hollow 05. Thiselevator is provided with a device, variously designated as pilot vane, or "flettner flap 86, mounted by means of pin 81 and support 88.

Tab 06 is provided with an extension or lever portion 89 with a pin 90, connected by rod 9I to piston I I4 in the cylinder 92, having a spring I I3 inserted to counteract the pressure in this cylinder, the cylinder being mountedon the sup port 93. I

'A two way valve 96 is provided with a handle 91, located within easy access of the pilot of ders, the portion 94 being extended into the shaft 22, which, of course, must be free to turn, and terminates by way of the Ol'lfiCG II5. I

When pressure is thus applied, spring I I3 offering less resistance than spring I I6, being particularly proportioned in this manner, rod 9I moves out, tipping tab 89 down, which acts aerodynamically in a well known manner to establish the angle of incidence of elevator 4, which in turn reacts aerodynamically to establish the angle of attack of the wing I0, or, in this case of the whole airplane, relative toits path until for any particular setting of tabf 86 stable equilibrium is established at a definite angle of attack at which the airplane persists in flying until tab 86 is again adjusted.

Throughout a predetermined incidence range for the elevator 4, spring li3and the pressure from the reservoir 98, controlled by valve 96, have the description with reference piston H4 somewhat between its two extremes of movements. I

However, when spring H3 .has been fully compressed by the'pressure upon the piston II4, it

acts as a stop to prevent further movement and.

lets the pressure build up as the handle 91 is further actuateduntil the pressure is sufficient to overcome the resistance of spring H6, there: by actuating rod I02, causing augmenter I6 to assume an active position, as well as opening shutter I08, bringing slot I01 into action.

Of course, either slot I01 oraugmenter I6 could be eliminated without interfering with the action of one or the other as will be clear to those skilled in the art,- but the combined actionof the slot the described means, and this combined actionis well known to be veryefiicacious as a lift augmenting means referred to in the beginning of to Handley Page From the above it should be understood that v a lift augmenting-device designed and arranged according to this invention can be made to raise the value of the lift coefficient above a maximum at a high angle of attack of a wing. On the other hand, a hydraulic cylinder and piston could be substitutedv for the bell crank 4| of Fig. .10, which, when a predetermined value of angle of incidence is attained, comes to the end of its stroke, and at The mechanical device shown in Fig. '10, but,

with members 52, 53, 54, and 56 eliminated, and

stabilizer 5'I immovably secured to anchor-56 b'y any well known means, is adaptable to another feature of the invention. If a wing of the character of Fig. 4 were mounted with point 59, where the lines of action 1, 8, 14 etc. all converge and substantially all intersect each other on the center. of gravity of the airplane, and if thepivot I2 were also located at or substantially at this'same, point, 59,. then variations in the incidence. of Wing chord 24 would not disturb the balance of the airplane, and variations in angle of attack dueto changes in the attitude of the airplane relative to its-path would likewise not disturb the balance of the airplane. The airplanewould be .in equilibrium at any-position of incidence adtail could be made, and yet accomplish the same results as the specific devices. shown and described hereinbefore. Therefore, the spirit tion. I

It shouldfinally be understood that, when the principles of this invention are applied to various distinct forms of airplanes or airplane construcrather than any specific details as shown should be construed as constituting the present inven- .tions, it is most positively not so much concerned 7 about any change of incidence, though incidentally a change of incidence may become involved, but rather the change of angle of attack controllable by and causing control of other action before the airplane has been operated through a considerable movement from a low angle of attack to a certain acute point of the whole range of movements towards a high angle of attack, involving that a plane must be operated from a low angle of attack, regardless of the direction, whether in level flight, rising, or landing direction, to a suitable higher angle of attack beyond the danger or acute point, or beyond the danger zone of the movements for changing from a low to a high angle of attack up to the acute point, before the augmenting device can be brought into action.

Having described my invention, I claim:

1. In an aircraft having a body, a wing pivotally mounted on said body about a pivot in the forward part of the wing and comprising a main wing section and a trailing edge flap pivoted on said main section for movement with respect thereto, mechanism to positively swing said wing about its pivotal mounting, a control member secured to said flap, said body having guide means comprising one portion concentric with the pivot of the wing and another portion nonconcentric therewith, said portions cooperating with said control member whereby the flap is held in alignment with the said main section during the first portion of the downward pivotal movement of the wing from its normal setting on the body and is displaced downwardly relative to the main section throughout the remainder of the downward pivotal movement of the wing.

2. In an aircraft with a wing operative by means for changing the angle of attack throughout distinct primary and secondary ranges during a normal flight designed and arranged to create a normally maximum lift coeflicient at an effective high angle of attack and including a lift augmenting device movably mounted on the wing, the primary range including all positions between the lowermost up to the highest low angle of attack, and the secondary range including all positions above said highest low up to the highest high angle of attack in which a normally maximum lift' coeflicient is effective; a control device disposed on the aircraft and in operative connection with the lift augmenting device having control-means for the primary range whereby the lift-augmenting device is maintained inoperative and including distinct other control-means for the secondary range whereby the lift-augmenting device is brought into action with an increase above said normal maximum lift coefficient.

3. In an aircraft with a wing operative by means for changing the angle of attack throughout distinct primary and secondary ranges with respect to a normal flight direction designed and arranged to create a normally maximum lift coefficient at an effective high angle of attack and including a lift augmenting device swingably mounted on the wing, the primary range including all positions from the lowest angle up to a point in which the lift coefllcient has values between 40% and 99% of said maximum, and the secondary range including all positions above said point up to the highest high angle of attack in which a normally maximum lift coefficient is effective; a control device disposed on the aircraft and in operative connection with the lift augmenting device having control-means designed for continuance-positioning for the primary range whereby the lift augmenting device is automatically maintained inoperative by the operation of the wing during said primary range and including distinct other control-means designed for variable-positioning whereby the lift augmenting device is automatically brought into.

action by the operation of the wing during said secondary range with an increase above said normal maximum lift coeflicient.

4. In an aircraft embodying a wing with a lift augmenting device and including operating means by which the angle of the wing chord to the path of the air stream can be changed to the extent of distinct primary and secondary ranges during the normal flight of the aircraft, the primary range including all positions between the lowermost up to the highest low angle, and the secondary range including all positions above said highest low up to the highest high angle; a control device disposed on the aircraft and in operative connection with the lift augmenting device having distinct control means for the primary range whereby the lift augmenting device is maintained inoperative and including other distinct control means for the secondary range whereby the lift augmenting device is brought into action with an increase of the lift coefficient of the aircraft.

5. In an aircraft with a center of gravity and a wing of the class described wherein the lines of action of aerodynamic reactions progress consecutively from front to rear throughout the flying range at a level of the center of gravity of the aircraft and including a lift agumenting device whose action modifies the progression of said lines of action, said range constituting distinct primary and secondary portions, the primary portion including all positions between the lowermost up to the highest low angle, and the secondary portion including all positions above said highest low up to-the highest high ,angle: a control device disposed on the aircraft and in operative connection with the lift augmenting device having distinct control means for the primary portion whereby the lift augmenting device is maintained inoperative and including other distinct control means for the secondary portion whereby the lift augmenting device is brought into action, and an auxiliary aerodynamic surface secured to the aircraft in longitudinal spaced relation to the wing designed and arranged to exert a moment about said center of gravity while said augmenting device is in action and to exert no moment about said center of gravity when said lift augmenting device is maintained inoperative.

6. In an aircraft with a wing operative by means for changing, the angle of incidence during a normal flight in such a manner as to also change the angle. of attack in form of distinct primary and secondary ranges and arranged to create a normally maximum lift coefllcient at an effective high angle of attack, the primary range including all positions between the lowermost up to the highest low angle, and the secondary range including all positions above said highest low up to the highest high angle; an auxiliary aerodynamic surface in longitudinally spaced 75 the aircraft and having a control means, and a mechanism in operative connection with the means operating the wing including a locking member so designed and arranged as to leave said control means and therewith the auxiliary surface free to swing while the aircraft is within said primary range and to firmly engage the control means for holding said surface in predetermined fixed relation to the aircraft within said secondary range.

7. In an aircraft with a wing operative by means for changing the angle of incidence during a normal flight in such a manner as to also change the angle of attack in formof distinct primary and secondary ranges serving as a speed controlling means and arranged to create a normaliy maximum lift 'coeflicient at an effective high angle of attack, the primary range including all positions between the lowermost up to the highest low angle suitable for high speed,

and the secondary range including all positions abovesaid highest low up to the highest high angle appropriate for low'speed; an auxiliary aerodynamic surface in longitudinally spaced relation to said wing mounted to swing freely on the aircraft and having a control means, and a mechanism in operative connection with the means operating the wing including a'locking member so designed and arranged as to leave said control means and therewith the auxiliary surface free to swing while the aircraft is within said primary range and furthermore so designed and arranged as to firmly engage the control means for holding said surface in predetermined range.

JOHN McK. BALLOU.

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