Typical Wing Research Articles

Locomotion in the Fossil Vulture Teratornis

Various parts of the skeleton of the large Pleistocene vulture, Teratornis merriami, have been found in deposits in the southern United States, from California to Florida, and in Mexico. Nowhere are the remains as numerous or as well preserved as in the asphalt deposits of Rancho La Brea in southern California. It was this abundance and preservation of entire bones that made possible this study of its locomotor apparatus. I am grateful to the Los Angeles County Museum, Los Angeles, California, for the use of its facilities and specimens. Teratornist merriami has been placed in a family distinct from, and yet closely related to, the family Cathartidae, the New World vultures. Many of the bony parts, the synsacrum, tibiotarsus, tarsometatarsus, coracoid, ulna and metacarpus are typically cathartid with little except size to distinguish them from the Recent condors, Vultur gryphus and Gymnogyps californianus. The skull and sternum are not cathartid in character although there are points of resemblance. The humerus has several peculiarities not found in the New World vultures. The gross similarities of certain wing elements of the tertatorn to those in the cathartids have led to the suggestion that Teratornis was similar in its flight pattern, that is, that it was chiefly a soaring bird. There are few specific features to uphold this contention. It is known that Gymnogyps californianus, the California Condor, on level ground must run or hop for several yards to gain enough momentum to lift its weight into the air. It also needs to flap several times as it leaves the ground. If Teratornis had a similar type of wing, its run for the takeoff must have been even longer because of its greater weight. However, we find that its wing was shorter in relation to its body weight (Table 1), and its legs were much shorter than in Gymnogyps (Table 9). Its leg bones are more delicate distally. With such poor adaptations for running, a long run for the takeoff would have been an arduous, if not impossible, task. It seems likely that Teratornis was able to leave the ground by use of its wings more easily than can the present California Condor. Miller (The Birds of Rancho La Brea, Publ. 349, Carnegie Inst., Washington, 1925) has wondered how Teratornis with its weak legs, soaring wings and great weight took off from a level surface. Such a combination of characters and terrain would seem to make the takeoff almost impossible. One possibility is that Teratornis lived exclusively in areas of cliffs and slopes where easy travel downhill would be sufficient to gain speed for soaring flight; this appears unlikely. I think it more probable that Teratornis rose from the ground by vigorous flapping of its wings. The body weight of the teratorn compared with that of any other flying bird must have been enormous. An attempt to get a gross estimate was made by determining the areas of the sternum and synsacrum in Haliaeetus and 725

Tailless Aircraft and Flying Wings

Even in these days of long development periods of conventional metal structures and of huge production orders for orthodox aeroplanes the interest in the Flying Wing type and in tailless designs is by no means asleep.

SUBDIVISION OF INSECTA PTERYGOTA INTO SUBORDINATE GROUPS

THE acquisition of wings is the most important factor upon which the unparalleled progressive evolution of insects depends. The development of liquid food feeding, though of great moment, plays only a subordinate part as compared with flight. Every order of the Insecta Pterygota shows its own type of wing, and the wing venation serves as a well-established systematic criterion, yet the functional significance of the almost endless variations in venation is as yet scarcely perceived. On the other hand, the musculature of wings shows considerable constancy in the majority of Pterygote orders, its principal modifications being few and functionally comprehensible. Therefore an attempt seems desirable to use 'the muscular motor of the wing' as a taxonomic criterion, especially for the much-needed grouping of insect orders into larger units.

Elliptic Tunnel-Wall Corrections on Drag and Stall

The tunnel-wall effects on drag and stall, given by the usual simple corrections, are not adequate when the span-diameter ratio is high or when the spanwise lift distribution varies considerably from elliptical. In order to determine more exact interference corrections, especially for elliptic throat tunnels of closed section, the up wash induced by the tunnel walls on the major axis, due first to the presence of lifting lines of different span lengths and then to the presence of typical wing distributions built up from these lifting lines to simulate actual wings, is computed for a number of wing distributions and spans. All the calculations are for wings whose aspect ratio is eight, and all are based on the constants of the Wright Brothers elliptic throat wind tunnel at the Massachusetts Institute of Technology. The magnitude of these corrections is found to vary inversely with the taper ratio of the wing, the corrections being less for a highly tapered wing and more for a rectangular wing of the same span and aspect ratio. For those cases where the wing tips lie outside the foci of the throat section, the variation of the induced angle of attack along the span is no longer negligible at high lift coefficients. I ts geometric effect is to cause an apparent washin angle toward the wing tip. The induced drag corrections have minimum values when the wing tips are at or near the foci of the tunnel for all usual lift distributions along the span. As the wing tips approach the tunnel wall, both the induced drag corrections and the angles of apparent washin or of apparent twist increase rapidly.

The Pupal Contraction as an Epigenetic Crisis in Drosophila.

Summary.1. In flies homozygous for thick there is a partial failure of the contraction of the leg from the highly inflated condition characteristic of the beginning of the true prepupal period; the same is true, to a lesser degree, of the wings.2. This is preceded, and probably caused by, an over‐contraction of the longitudinal larval muscles at the time of puparium formation, which is such as to give rise to an increased fluid pressure inside the body of the animal.3. In humpy flies there is an over‐contraction of the epidermis of the wings and thorax, which is responsible for the shortening of the wings and the formation of grooves and “vortices” on the thorax.4. At the time of puparium formation, the larval muscles of humpy contract irregularly, and a similar irregular muscular contraction plays a part in producing the deformations during the beginning of the true pupal period‐ The abnormal larval contractions sometimes cause modification of the normal internal anatomy, which in their turn result in irregular eversion of the legs, leading to abnormalities in their later contraction during the pupal period.5. It is pointed out that such a mechanism reduces the difficulty of understanding the apparently dissimilar effects of the different dumpy allelomorphs, some of which produce the humpy type of wing while others produce the humpy type of thorax.6. The relevance of the data for the general theory of development is briefly mentioned.

Control Surface and Wing Stability Problems

SummaryThis paper seeks to draw from current research work on flutter and related problems results of general design significance; and, avoiding mathematics, endeavours to set these results out in relation to past and present problems.A preliminary section of the paper indicates the main stability and allied troubles concerned and draws attention to the general similarity between wings and tailplanes in relation to these troubles. The remainder of the paper is then devoted to a discussion of the problems involved in terms of wings and ailerons.For this purpose a “ stiffness diagram ” is constructed for a typical wing, indicating the relative stiffnesses, etc., required to prevent wing-aileron flutter, wing flutter, aileron reversal, and wing divergence. By means of this diagram the course of recent history in relation to wing-aileron flutter and aileron reversal is illustrated, and attention is then given to present and future tendencies and problems. The current tendency to employ wings of high density—arisingly largely from high wing loadings—is making wing flutter the problem of immediate importance, and ways of avoiding the provision of increased stiffness as usually adopted to prevent this trouble, as well as to prevent aileron reversal and wing divergence, are discussed.Appendices are given commenting on the variation of wing flutter speed with altitude and on the modern tendency to usa wings of low flexural stiffness.

The Ancestors of the Diptera

IN a previous communication to NATURE some years ago (May 18, 1929) I gave a short description of a remarkable genus Permotipula, represented by a complete forewing from Warner's Bay, N.S.W., and of Upper Permian Age. Although very primitive by comparison with existing types of Diptera, this wing was regarded by me as being definitely Tipuloid and lying well within the order. I added the following remarks: ” The wing is of the greatest interest, because any student of venation would classify it as dipterous and nothing else, and yet we do not know whether the insect to which it belonged had four wings or only two! Also, it is the oldest known dipterous type of wing by many millions of years.”

On the Separation of Turbulent Boundary Layers

S T U D E N T S of fluid mechanics agree now rather generally that the separation of the boundary layer from a wing surface is the cause of burbling and is responsible, therefore, for the complicated phenomena near the stall. There is consequently a great practical as well as scientific interest in obtaining an analytical method of predicting such separation. One method of analyzing flow separation in the case of a turbulent boundary layer was proposed by Gruschwitz and seemed to offer a practical solution. The limited experimental evidence in favor of this method, however, was not sufficient to command confidence in its general application. In the present research an attempt was made to verify the Gruschwitz method by an extended experimental examination of the turbulent boundary layer over a typical wing profile at high Reynolds Numbers. The data here presented lead to the conclusion that the Gruschwitz method does not describe the actual phenomena and is, therefore, not the general solution hoped for. The evidence now seems to point to a dependence of flow separation upon several other variables besides the pressure gradient and the thickness of the boundary layer which need further experimental examination. Such investigation is now under way at the Massachusetts Institute of Technology and a further report will be made in a subsequent paper. The mechanics of flow separation depends upon the motion of the air within the boundary layer. The particles within the boundary layer are retarded by the surface friction and are usually carried against a rising pressure by the momentum transferred to them from outside of the boundary. If the pressure rise is sufficient the particles lose energy, come to rest, and separation occurs. If the momentum is transferred from the exterior stream by molecular exchange purely, the motion is defined as laminar, while the motion is defined as turbulent if the exchange is molar. All boundary layers begin at a stagnation point and remain laminar for a certain distance downstream whatever may be the character of the exterior flow or of the surface. If the prevailing velocity is sufficiently high and the surface sufficiently large, however, the layer will become turbulent and continue so throughout the remainder of its length. The chief characteristic which distinguishes the turbulent flow from the laminar is its much greater ability to transport momentum laterally. This gives it a correspondingly greater ability to proceed against a rising pressure. The separation of laminar boundary layers has recently been studied by von Karman and Millikan who explained the variation of the maximum lift coefficient with low Reynolds numbers in the case of certain wing profiles. The separation of the turbulent boundary layer, however, is of greater importance at the higher Reynolds numbers used in engineering since it is responsible for most of the burbling phenomena met in practice. The studies presented here are an outgrowth of a recent investigation by Gruschwitz on the behavior of turbulent boundary layers for various pressure gradients. Since this method is used for comparison with the experimental data here reported, it will be well to review it briefly.

Thurston Wing-Tip Rotors Control Beyond the Stall

Summary and DeductionsThe accompanying Report No. B.A. 1083 of the Royal Aircraft Establishment demonstrates generally that a moving body or rider plane can be associated with a fixed body or plane for altering the aerodynamic properties of the combination for various useful purposes, and in particular, that rotating cambered rider planes, when associated with the front edge of a fixed wing of standard section (see Fig. 11) “are definitely advantageous” in improving the gliding conditions, and that “by increasing the size of the rotors relatively to the size of the wings, this superiority is increased.”Previous experiments at the N.P.L. with various types of wings fitted alternately—with optimum wing-tip slots and with rotors—have shown that rotors can give about the same degree of lateral stability as tip slots, but over a much wider angular range. Other experiments with better rotors than used at the N.P.L. have shown that a more powerful stabilising effect over a wider annular range is to be obtained with rotors than with slots.

“ Wapiti ” Steel Wings

With the present-day normal type of wing the spars are the principal members, and I propose to start by tracing very briefly the evolution of the spars which are used in the Wapiti wings to-day.The personnel of the Steel Wing Company have been designing and making spars ever since 1912. I shall start from the time when we first began to use what might be described as the box type of spar, which was composed of four strip steel sections.The first spar that we made of the box type had channel webs with flat flanges, which had only shallow corrugations, and the rivetted joint was flat. This spar was not very efficient in steel, so we deepened the corrugations and curved the rivetted joint, and this gave a better result.

XXVII.—The Inheritance of Long and Short Wings in the Weevil,Sitona hispidula, with a Discussion of Wing Reduction among Beetles

It is well known that in many orders of typically winged insects species occur which in the adult stage are apterous or have the wings so reduced in size that flight is impossible. Sometimes the reduction of wings affects one sex only, as in the case of the females of certain moths, but in the majority of cases it is exhibited by both sexes. In many instances wing dimorphism occurs irrespective of sex, one form of the species having fully developed wings and the other greatly reduced wings. In some species the wings are polymorphic. The problem of the origin of reduced wings and of other functionless organs is one of great interest from the evolutionary point of view. Various theories have been advanced in explanation, but in the majority of cases the various aspects of the subject are too little known to warrant discussion. More experimental work is required to show how far environmental conditions on the one hand, and hereditary factors on the other, are responsible for this phenomenon. Those species which exhibit alary dimorphism afford material for the study of the inheritance of the two types of wings, but only in a few cases has this method of research been utilized.

A PROCHLORITE BANNERSTONE WORKSHOP

O NE and a half miles below the aboriginal workshop on Mt. Johnson Island in the Susquehanna River, described in the October-December, 1921, number of the American Anthropologist, is another bannerstone workshop. This one is located on the east bank of the Susquehanna below Peach Bottom, Lancaster County, Pa. It does not compare in size with the one formerly described, where hundreds of slate bannerstones were shaped; neither was the same material used nor did the same shape of bannerstone prevail. While at the island workshop almost all of the unfinished specimens found were of slate and of the winged type with well-defined centrums; those found at the lower workshop were made of prochlorite and usually of a doubleconvex form truncated at top and bottom or bottom only and without any pronounced centrum. Prochlorite is a soft green stone containing crystals of magnetite. When found in situ it usually occurs contiguous to steatite and is sometimes wrongly called green soapstone. While this material was chosen for making bannerstones, partly because of the ease and safety with which it was worked, the magnetite crystals it contains were a factor that entered into the choice. The shining black crystals added materially to the beauty of the finished bannerstone. The nearest source of this material is about five miles down the river, at Bald Friars, Md. No positively aboriginal prochlorite quarry had thus far been identified here; and it is a question whether the Indian needed to quarry the material since there is such an abundance of it found along a small stream which enters the Susquehanna at this point. However, some of the numerous pits covering the side of Bald Hill may have been made by the Indian in search of prochlorite containing the larger crystals of magnetite. We know from unfinished and broken vessels found that he quarried steatite here

The Pupal Wings of Hepialus Thule

The adult wings of the different species of the genus Hepialus are of particular interest because they show such a generalized condition. They approximate the closest to the hypothetical wing type of Comstock and Needham of any insect’s wings with which I am acquainted. This hypothetical type is supposed to show the number and arrangement of the longitudinal veins as they existed in the primitive insect’s wing. These authors have shown that a study of the arrangement of the tracheae preceding the formation of the veins in developing wings throws much light on the homology of the veins of the adult wing. Many developing wings of Lepidoptera have been studied and figured, but so far as I am aware no investigator has studied and figured the developing wing veins of a species of Hepialus . It was my good fortune, through the kindness of Professor J. M. Swaine of MacDonald College, Quebec, Canada, to obtain pupae of Hepialus thule hardened in formol in the right stage for a study of the developing wing veins. These specimens showed not only the tracheae, which are represented as black lines on the accompanying figure, but also the veins, which are represented as white bands. Unfortunately nothing could be determined as to the arrangement of the tracheae after they left the veins and entered the body. The various veins will be taken up in order.