US2664666A - Acrobatic toy airplane - Google Patents

Description

Jan. 5, 1954 N. E. WALKER ACROBATIC TOY AIRPLANE Filed July 25, 1951 INVENTOR. Neville JiWcl k er m g r Patented Jan. 5, 1954 2,664,666 ACROBATIC TOY AIRPLANE Neville E. Walker, Portland, reg., assignor to American Junior Aircraft Company, Portland, 0reg., a corporation of Oregon Application July 23, 1951, Serial No. 238,115

6 Claims. (CI. 4679) This invention relates to a toy airplane of the type designed primarily for hand or catapult launching into a condition of free flight.

A particular object of the invention resides in the provision of a glider-type toy airplane capable of executing a wing-over, snap roll, or other preselected acrobatic maneuver during such free flight.

The basic examples of the ready-to-fiy toy airplane industry are the well-known balsa wood glider and dart. Either of these toys may be hand or catapult launched and a majority of these toys are sold to school age children. Experience has taught man parents that their school age children will, hour after hour, launch and ii'y these airplanes in play and fun. As is to be expected, such practice and concentration soon lead to a certain amount of skill and proficiency "in so directing the launching of the toy that the flight path will assume a particular pattern. In fact, the more practiced child soon accumulates sufficient knowledge to direct the execution of loops, sweeping turns, spirals, and many other acrobatics and maneuvers simulating those of actual aircraft.

Referring more particularly to the glider-type my airplane, in which classification I include the winged dart, certain aerial acrobatics and maneuvers appears to have defied execution even by the more skilled children. Among such maneuvers I would include the wing-over, the roll and the snap roll. Ina wing-over, the airplane is put into a climbing turn until it is nearly stalled, at which point the nose falls off while the turn continues. The airplane then returns to normal flight in a direction approximately 180 degrees from that of the start of the evolution. In the roll, a complete revolution is made about the longitudinal axis while the horizontal direction of flight approximately is maintained. A snap roll is similar, but differs in the speed of revolution and execution.

Having in mind the fact that such diflicult maneuvers hitherto have been executed, if at all, only by the most skilled and practiced of children, one object of my invention is to provide a novel toy airplane capable of executing these maneuvers at the will of the launcher. Furthermore, my inventive scope includes the provision of an airplane which is so balanced, :aerodynamically, that even a young or unskilled child can execute such maneuvers with a mini .mum of practice.

To this end, I have determined that the toy .airplanes of the prior art are deficient in those 2 structural provisions which are essential to cause a rotation about the longitudinal axis during free flight. In fact, a vast majority of these prior airplanes seek to suppress such revolution by including or building in lateral stability. Such lateral stability is evidenced by a symmetrical construction wherein the wings and tail surfaces on each Side of the fuselage are allochiral. In accord with my inventive scope, however, an entirely different structure is essential. Thus, I have determined that two prime factors forecast the flight characteristics of a toy aircraft. These factors, excluding drag, are lift and dead weight. If the lift and weight on both sides of the longitudinal axis are identical, the airplane generally will possess lateral stability. Such stability precludes the execution of any maneuver requiring a free flight rotation about this longitudinal axis since the forces on the fuselage and wings always are balanced.

For a moment, let it be assumed that the wing on one side of the fuselage is given more lift than its companion on the other side. This may be doneby increasing the angle of incidence, creating a wing of higher lift section, as by increasing the camber, increasing the wing area, or by warping one wing tip or washing in the other wing tip. Such an increased lift aerodynamically will unbalance the lateral forces acting upon the airplane. Accordingly, a continuous rotational couple will be impressed upon the lateral supporting surfaces of the airplane during flight. In short, the airplane will revolve or roll, side over side, from the moment it is launched. This maneuver is undesirable, to say theleast, since the airplane never can right itself to gain altitude. Thus,.the airplane will crash almost immediately after launching if this unbalanced lift per se is built into the wings.

Now, in accord with my inventive concept, let it be assumed that the increased lift on one side of the fuselage is offset and balanced by an increased weight placed on the same side. This may be done by clamping a weight to the wing having greater lift, by coating that wing with a paint or varnish, by building that wing from heavier material, or by otherwise weighing down the critical side of the airplane. If, in addition to weighing down one side, such a weight is selected and applied in a careful manner so as substantially to be equal to the increased lift on the same side, the toy airplane once more will be laterallv balanced during normal flight. However, since the lift on a wing section varies directly with the square of the flight velocity, the

airplane will be unbalanced during conditions of very high or near zero velocity. This is exactly in accord with the structure of my invention and with the objects thereof since the lateral balance, so essential to gain altitude and prevent a crash, now may be varied during free flight and after such altitude is gained. For example, if the airplane is launched to fly in a climb, it will first follow a substantially straight course, after which it will execute an automatic wing-over when the wings stall out or approach the critical angle of attack. That is to say, as the airplane stalls, the lift approximates zero force and the unbalanced dead weight pivots or rotates the entire structure about the longitudinal axis. Thereafter, as the falling airplane picks up speed, it once more is laterally balanced to execute a return flight in a direction approximately 180 degrees from the launching direction.

Accordingly, one object of my invention is to provide a toy airplane in which the wings exert unequal lift forces and in which the reater lift is balanced out during normal flight by an unequal weight distribution, all to the end of promoting automatic acrobatics and aerial maneuvers in free flight.

A further object of my invention is to provide a curved weight for use with the conventional resilient wing of a toy aircraft so that such a wing may be deformed or bent to serve the dual functions of increasing the lift :force while, at the same time, increasing the weight thereon.

These and other objects and advantages of my invention will be set forth in the following detailed description, taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a top orplan view of a glider-type toy airplane having a first species weight detachably secured to one wing thereof;

Fig. 2 is a front view of the airplane of Fig. 1 better indicating the manner in which the weighted wing is twisted or bent .to define a greater angle of incidence so as to produce a greater lift during flight;

,Fig. 3 is a schematic diagram indicating the flight path of the airplane of Figs. 1 and ,2 during which flight path theairplane automatically executes a wing-over and returns much in the manner of a boomerang;

Fig. 4 is a partial detail view of a secondspecies of weight wherein one wing tip is coated with a paint or varnish of substantial weight in comparison to a light toy airplane;

Figs. 5 and 6 are related cross-sectional views taken across the two opposite wings of a toy airplane made in accord with another species of my invention, these cross-sections indicating the greater density and angle of incidence of one wing with respect to the other; and

Fig. 7 is a cross-sectionalview through a wing similar to that of Fig. 6, but indicating yet another species of my invention wherein a curved weight detachably grips and deforms this resilient wing to increase the lifting power thereof while, at the same time, increasing the dead weight thereof.

The lift of an airplane wing is that component of the total aerodynamic force acting .on the wing (or the airplane) perpendicular to the relative wind. conventionally, this .lift .is expressed in eguation .form as:

In this equation, C1. is the lift coefiicient ex-= pressed in absolute or dimensionless numbers, r is the air density, S is the wing area, and V is the relative wind velocity. If S is square feet, V is feet per minute, and the other factors are commensurate therewith, the lift will be expressed in pounds of force. The lift coefficient CL varies with the built-in characteristics of each particular airfoil and generally is calculated from wind'tunnel tests. In general, it is dependent upon the camber, the thickness, the angle of incidence, the taper, and the laminar or turbulent flow characteristics at different velocities.

In accord with my inventive objects, the lift of the wing on one side of the fuselage of a toy airplane must be increased over that of its companion on the other side. In accord with the above formula, this increased lift may be effected by increasing the camber, the angle of incidence, the thickness, or the area, or by warping or bending the tip of one wing. Further in accord with my inventive objects, that side of the airplane carryin the wing having the higher lift characteristics, must also be Weighted down or otherwise caused to weigh more. Accordingly, he drawings indicate a number of inventive species exemplary of those structures utilized to increase the lift and increase the weight upon one side of the fuselage .Of a toy airplane.

To this end, I have shown an elongated fuselage I having a nose 2 defining the longitudinal axis of the airplane. Preferably, this nose carries .a small weight to balance the airplane. If my invention is incorporated in a glider which has the general characteristics of an airplane, rather than in a winged dart partially devoid of ,such characteristics, a horizontal stabilizer 3 and a vertical tail .4 are provided. Additionally, either a dart or a conventional aircraft shape will be provided with one or more lateral win surfaces such as those shown at 5.

In Figs. .1 and 2, I have shown an integral or continuous type wing5 having a first lateral portion .6 and a second or companion lateral por tion 1. In general, these wing portions will be referred to as the right and left wings, respectively. Thus, Fig. 2 indicates the manner in which the right wingBis bent or deformed slightly to define an increased angle of incidence. The angle of incidence, in airplane parlance, is the acute angle betw en the plane of the wing cord, and the longitudinal axis of the airplane. In other words, the leading ,edge of a wing conventionally -is higher than the trailing edge so that the wing will exert .a lift in flight. This increase in height is expressed as an angle and the greater this angle, the greater the lift, within proper limits.

As previously discussed, an unbalanced lift per se creates a .fiight characteristic synonomous with a continuous roll. .Such a characteristic is undesirable in a toy airplane. Accordingly, I have fastened to the right wing 6, a small weight 8. This weight serves tobalance the airplane during normal flight since the magnitude thereof is calculatedsubstantially to equal the difference between the lifting forces on the wings. Furthermore, itis .best if the weight 8 frictional- .ly engages the-right wing .Gso that it canbe adjusted or moved laterally along the wing in accord with the-,fiight velocityto be obtained ,upon launching. Thus, ificrent children will launch the airplane at different velocities, and it is only when a catapultis used-or when the same child .launchessuccessive .fiightsthat the setting 5 for the weight 8 can be determined accurately ahead of time. Said weight 8 thus adds to the mass of the wing 6 and adds extrinsic weight to the mass or weight of said wing.

In Fig. 3, I have shown a typical flight pattern in accord with the accepted definition of a wingover. Initially, the airplane is launched, as at 9, at a normal flight speed. At this normal flight speed, the unbalanced lift force created by the increased angle of incidence built into the right wing substantially is balanced by the excess weight added thereto as at 8. Accordingly, the flight path is in accord with that of a laterally stable toy airplane. Continuing along the flight path, the airplane will climb and, as it does so, the flight velocity falls off. Eventually, as at Hi, the airplane will begin to stall as the wings approach their critical angle of attack. The critical angle of attack for any wing is that angle of attack at which the flow about the airfoil changes abruptly from laminar t turbulent flow. At this angle, the streamline flow breaks down and a burble is evidenced. Furthermore, the lift and drag characteristics of the wing change radically at this an le and the lift force quickly approaches zero. Accordingly, as the lift force approaches zero. the airplane will tend to rotate about its longitudinal axis due to the unbalanced force exerted by the weight 8. This rotation flips the airplane over, as at l I, and it enters a steep dive. In the dive, the airplane picks up speed and once more becomes aerodynamically and laterally balanced due to the increased lift on the right wing 6. Thereafter, the airplane returns in normal flight and in a direction approximately 180 degrees from that of the launching. This maneuver, then, is a wing-over.

In essence, the execution of a wing-over or snap roll by a toy airplane depends upon an increased lift and an increased weight disposed to the same side of the longitudinal axis. Accordingly, in Figs. 4, 5, 6, and 7, I have shown other species of my invention wherein other structures are utilized to increase these critical factors. In Fig. 7, for example, I have shown a U-shaped weight i 2 which is curved and which frictionally engages the right wing 6. Since the wings of most toy airplanes are resilient, the weight 12 deforms the wing 6 to induce therein an increased angle of incidence as shown at A. That is to say, most toy gliders and darts are made of balsa wood or thin plastic or sheet metal. Such materials readily are deformed under sli ht pressure. The weight l2, which may be either a bent paper clip or a weight of special design, serves to exert such a pressure and such a bend ing force upon a wing which otherwise would be balanced and normal. Thus, a toy airplane equipped with this wei ht will execute the same maneuvers as the airplane shown in Figs. 1, 2, and 3. Furthermore, by moving the weight back and forth along the wing, the amount of bend and the wei ht location can be varied to adjust the fli ht characteristics, as desired.

In Figs. 5 and 6, I have shown a further species of my invention. This species is shown as it would appear in a cross-sectional view taken through the right and the left wings 6 and 1, respectively. If, for example, the airplane is made of balsa wood, the right wing 6 may be weighted by forming this portion from a more dense section of balsa wood material. This is practical since usable balsa wood varies in density from seven to ten pounds per cubic foot. A variation of one pound per cubic foot is not untogether.

common in a single log or piece of wood. Thus,

if such varying densities are taken into account, it is possible to form an integral wing in which the density will vary from tip to tip sufficiently to overcome the increased lift incorporated in the heavier wing section. Optionally, of course, wing sections of varying density may be glued In Fig. 5, the angle A indicates an angle of incidence for the right wing 6 which is greater than the angle of incidence B for the left wing 1. in Fig. 5 indicates a more dense section of balsa wood or other material to compensate for the increased angle of incidence A. As a further option, a wood or material of uniform density may be employed, and the right wing it may be made thicker as shown by the dashed lines M in Fig. 5. This thickening both will increase the weight of that wing and will increase the lift thereof since the coefliciency of lift is directly proportional to the thickness of the airfoil section. In any event, a toy airplane constructed in accord with Figs. 5 and 6 will execute maneuvers or acrobatics similar to those of my other species.

As yet another example or species, I have shown the right wing 6 coated with paint or varnish, as at I3, in Fig. 4. Such a coating, of course, must be combined with-an increased lift in the same wing. However, it is interesting to note that the light weight of a balsa wood or sheet metal toy airplane is such that even this small additional weight suificiently will unbalance the airplane adjacent the critical angle. Thus, this species will execute the same maneuvers as the other species of my invention.

Recalling once more the equation for computing the lift on an airplane wing, it will be noted that the lift force varies directly as the square of the velocity. Accordingly, my inventive structure is also suited to the execution of a snap roll. For example, if the airplane is launched with a catapult, the initial take-oif velocity will be quite high. This high velocity may be suflicient to build up an unbalanced lift capable of overcoming the added weight placed on or built into the critical wing. Accordingly, as the airplane leaves the catapult, it will execute a complete revolution about the longitudinal axis (a snap roll) before assuming the flight path shown in Fig. 3. Such a snap roll is almost impossible to execute with the laterally stable toy airplanes of the prior art.

In accord with my inventive objects, I have disclosed numerous species of an acrobatic toy airplane, each of which is stable laterally in normal flight yet each of which is unbalanced in a stall or adjacent the critical angle of attack. These various structures allow even a young or unskilled child to execute a variety of acrobatics or aerial maneuvers with a minimum of practice. Furthermore, I have shown an adjustable curved weight which may be used with a resilient wing section to serve the dual functions of increasing the lift thereof while, at the same time, increasing the weight thereon. This weight, when properly placed, provides a toy airplane capable of executing the aforementioned maneuvers at the will of the launcher.

I claim:

1. A propellerless type toy airplane, compris ing an elongated fuselage defining a longitudinal axis, a wing means mounted upon said fuselage to exert lifting forces thereupon during flight, one side of said wing projecting laterally out Furthermore, the close cross-hatching from each side of said longitudinal axis, the lifting force on :oneside of saidaxis exceeding face carried at one side of ,said fuselage and having a first lift characteristic, a second lateral wing surface carried at the opposite side of said fuselage and havingasecond lift characteristic, said first lift characteristic exceeding said second lift characteristictoexert a greater lift upon said one side during normal flight of said airplane, and extrinsic weight means effective upon said one side of said fuselage ,to balance and stabilize .said airplane during normal flight.

:3. In a propellerless type toy airplane, an elongated fuselage defining a longitudinal axis, a

first wing projecting to one side of said axis and a second wing projecting to the opposite side of said axis, said first wing having a camber and angle of incidence defining means for producing a first lifting force in flight, said second wing having-a camber and angle of incidence defining means for producing a second lifting force in flight, said first lifting force being greater than said second lifting force, and unbalanced extrinsic weight means acting upon said airplane to said one side of said axis, said unbalanced weight means being substantially equal to the difference between said lifting forces laterally to balance said airplane during normal flight but laterally to unbalance said airplane at other .times.

4. A miniature airplane, comprising an elongated fuselage having supporting surface means projecting laterally from each side thereof to exert ,a lifting force upon said airplane proportional to the square of the flight velocity, the

surface means on oneside of-said fuselage having greater lift than those on the other side, an extrinsic weight mass, said greater lift being onset and balanced at normal flight velocities by said extrinsic weight mass which is carried by said one side of said fuselage whereby the airplane will become laterally unbalanced when said flight velocity varies from normal flight velocities.

5. In a propellerless type toy airplane, a twosided longitudinal fuselage, a pair of resilient lateral wings, one of said wings projecting laterally from each side of said fuselage, said wings being carried'at a positive angle of incidenceto define complementary lifting surfaces, and a curved weight means detachably gripping and deforming one of said resilient wings to induce a greater angle of incidence therein.

6. In a propellerless type toy airplane, a twosided longitudinal fuselage, a pair of resilient lateral wings, one of said wings projecting laterally from each side of said fuselage, said wings having a camber and being carried at a positive angle of incidence to define complementary lifting surfaces, anda curved weight means detachably gripping and deforming one of said resilient wings to increase the lifting power thereof.

NEVILLE E. WALKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 996,061 Clarke June 27, 1911 1,507,710 Pohlman Sept. 9, l924 1,549,073 Dwyer Aug. 11, 1925 1,792,779 Tarr Feb. 17, 1931 2,303,965 Walker Dec. 1, 1942 FOREIGN PATENTS Number Country Date 17,935 Great Britain 1905

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