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Wing loading

About: Wing loading is a research topic. Over the lifetime, 1804 publications have been published within this topic receiving 35655 citations.

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01 Jan 1989
TL;DR: In this paper, the authors present an overview of the design process of an aircraft from a conceptual sketch, including sizing from a Conceptual Sketch and initial sizing of the aircraft.
Abstract: * Design - A Separate Discipline * Overview of the Design Process * Sizing from a Conceptual Sketch * Airfoil and Geometry Selection * Thrust-to-Weight Ratio and Wing Loading * Initial Sizing * Configuration Layout and Loft * Special Considerations in Configuration Layout * Crew Station, Passengers, and Payload * Propulsion and Fuel System Integration * Landing Gear and Subsystems * Intermission: Step-by-Step Development of a New Design * Aerodynamics * Propulsion * Structures and Loads * Weights * Stability, Control, and Handling Qualities * Performance and Flight Mechanics * Cost Analysis * Sizing and Trade Studies * Design of Unique Aircraft Concepts * Conceptual Design Examples * Appendix A: Unit Conversion * Appendix B: Standard Atmosphere.

2,374 citations

Journal ArticleDOI
TL;DR: Bat wing morphology is considered in relation to flight performance and flight behaviour to clarify the functional basis for eco-morphological correlations in flying animals, and adaptive trends in wing adaptations are predictably and closely paralleled by echolocation call structure.
Abstract: Bat wing morphology is considered in relation to flight performance and flight behaviour to clarify the functional basis for eco-morphological correlations in flying animals. Bivariate correlations are presented between wing dimensions and body mass for a range of bat families and feeding classes, and principal-components analysis is used to measure overall size, wing size and wing shape. The principal components representing wing size and wing shape (as opposed to overall size) are interpreted as being equivalent to wing loading and to aspect ratio. Relative length and area of the hand-wing or wingtip are determined independently of wing size, and are used to derive a wingtip shape index, which measures the degree of roundedness or pointedness of the wingtip. The optimal wing form for bats adapted for different modes of flight is predicted by means of mechanical and aerodynamic models. We identify and model aspects of performance likely to influence flight adaptation significantly; these include selective pressures for economic forward flight (low energy per unit time or per unit distance (equal to cost of transport)), for flight at high or low speeds, for hovering, and for turning. Turning performance is measured by two quantities: manoeuvrability, referring to the minimum space required for a turn at a given speed; and agility, relating to the rate at which a turn can be initiated. High flight speed correlates with high wing loading, good manoeuvrability is favoured by low wing loading, and turning agility should be associated with fast flight and with high wing loading. Other factors influencing wing adaptations, such as migration, flying with a foetus or young or carrying loads in flight (all of which favour large wing area), flight in cluttered environments (short wings) and modes of landing, are identified. The mechanical predictions are cast into a size-independent principal-components form, and are related to the morphology and the observed flight behaviour of different species and families of bats. In this way we provide a broadly based functional interpretation of the selective forces that influence wing morphology in bats. Measured flight speeds in bats permit testing of these predictions. Comparison of open-field free-flight speeds with morphology confirms that speed correlates with mass, wing loading and wingtip proportions as expected; there is no direct relation between speed and aspect ratio. Some adaptive trends in bat wing morphology are clear from this analysis. Insectivores hunt in a range of different ways, which are reflected in their morphology. Bats hawking high-flying insects have small, pointed wings which give good agility, high flight speeds and low cost of transport. Bats hunting for insects among vegetation, and perhaps gleaning, have very short and rounded wingtips, and often relatively short, broad wings, giving good manoeuvrability at low flight speeds. Many insectivorous species forage by `flycatching' (perching while seeking prey) and have somewhat similar morphology to gleaners. Insectivorous species foraging in more open habitats usually have slightly longer wings, and hence lower cost of transport. Piscivores forage over open stretches of water, and have very long wings giving low flight power and cost of transport, and unusually long, rounded tips for control and stability in flight. Carnivores must carry heavy loads, and thus have relatively large wing areas; their foraging strategies consist of perching, hunting and gleaning, and wing structure is similar to that of insectivorous species with similar behaviour. Perching and hovering nectarivores both have a relatively small wing area: this surprising result may result from environmental pressure for a short wingspan or from the advantage of high speed during commuting flights; the large wingtips of these bats are valuable for lift generation in slow flight. The relation between flight morphology (as an indicator of flight behaviour) and echolocation is considered. It is demonstrated that adaptive trends in wing adaptations are predictably and closely paralleled by echolocation call structure, owing to the joint constraints of flying and locating food in different ways. Pressures on flight morphology depend also on size, with most aspects of performance favouring smaller animals. Power rises rapidly as mass increases; in smaller bats the available energy margin is greater than in larger species, and they may have a more generalized repertoire of flight behaviour. Trophic pressures related to feeding strategy and behaviour are also important, and may restrict the size ranges of different feeding classes: insectivores and primary nectarivores must be relatively small, carnivores and frugivores somewhat larger. The relation of these results to bat community ecology is considered, as our predictions may be tested through comparisons between comparable, sympatric species. Our mechanical predictions apply to all bats and to all kinds of bat communities, but other factors (for example echolocation) may also contribute to specialization in feeding or behaviour, and species separation may not be determined solely by wing morphology or flight behaviour. None the less, we believe that our approach, of identifying functional correlates of bat flight behaviour and identifying these with morphological adaptations, clarifies the eco-morphological relationships of bats.

1,641 citations

Journal ArticleDOI
TL;DR: In this article, the average lift coefficient, Reynolds number, the aerodynamic power, the moment of inertia of the wing mass and the dynamic efficiency in animals which perform normal hovering with horizontally beating wings are derived.
Abstract: 1. On the assumption that steady-state aerodynamics applies, simple analytical expressions are derived for the average lift coefficient, Reynolds number, the aerodynamic power, the moment of inertia of the wing mass and the dynamic efficiency in animals which perform normal hovering with horizontally beating wings. 2. The majority of hovering animals, including large lamellicorn beetles and sphingid moths, depend mainly on normal aerofoil action. However, in some groups with wing loading less than 10 N m -2 (1 kgf m -2 ), non-steady aerodynamics must play a major role, namely in very small insects at low Reynolds number, in true hover-flies (Syrphinae), in large dragonflies (Odonata) and in many butterflies (Lepidoptera Rhopalocera). 3. The specific aerodynamic power ranges between 1.3 and 4.7 WN -1 (11-40 cal h -1 gf -1 ) but power output does not vary systematically with size, inter alia because the lift/drag ratio deteriorates at low Reynolds number. 4. Comparisons between metabolic rate, aerodynamic power and dynamic efficiency show that the majority of insects require and depend upon an effective elastic system in the thorax which counteracts the bending moments caused by wing inertia. 5. The free flight of a very small chalcid wasp Encarsia formosa has been analysed by means of slow-motion films. At this low Reynolds number (10-20), the high lift co-efficient of 2 or 3 is not possible with steady-state aerodynamics and the wasp must depend almost entirely on non-steady flow patterns. 6. The wings of Encarsia are moved almost horizontally during hovering, the body being vertical, and there are three unusual phases in the wing stroke: the clap , the fling and the flip . In the clap the wings are brought together at the top of the morphological upstroke. In the fling, which is a pronation at the beginning of the morphological downstroke, the opposed wings are flung open like a book, hinging about their posterior margins. In the flip, which is a supination at the beginning of the morphological upstroke, the wings are rapidly twisted through about 180°. 7. The fling is a hitherto undescribed mechanism for creating lift and for setting up the appropriate circulation over the wing in anticipation of the downstroke. In the case of Encarsia the calculated and observed wing velocities at which lift equals body weight are in agreement, and lift is produced almost instantaneously from the beginning of the downstroke and without any Wagner effect. The fling mechanism seems to be involved in the normal flight of butterflies and possibly of Drosophila and other small insects. Dimensional and other considerations show that it could be a useful mechanism in birds and bats during take-off and in emergencies. 8. The flip is also believed to be a means of setting up an appropriate circulation around the wing, which has hitherto escaped attention; but its operation is less well understood. It is not confined to Encarsia but operates in other insects, not only at the beginning of the upstroke (supination) but also at the beginning of the downstroke where a flip (pronation) replaces the clap and fling of Encarsia . A study of freely flying hover-flies strongly indicates that the Syrphinae (and Odonata) depend almost entirely upon the flip mechanism when hovering. In the case of these insects a transient circulation is presumed to be set up before the translation of the wing through the air, by the rapid pronation (or supination) which affects the stiff anterior margin before the soft posterior portions of the wing. In the flip mechanism vortices of opposite sense must be shed, and a Wagner effect must be present. 9. In some hovering insects the wing twistings occur so rapidly that the speed of propagation of the elastic torsional wave from base to tip plays a significant role and appears to introduce beneficial effects. 10. Non-steady periods, particularly flip effects, are present in all flapping animals and they will modify and become superimposed upon the steady-state pattern as described by the mathematical model presented here. However, the accumulated evidence indicates that the majority of hovering animals conform reasonably well with that model. 11. Many new types of analysis are indicated in the text and are now open for future theoretical and experimental research.

1,279 citations

Journal ArticleDOI
TL;DR: In this paper, a projection analysis technique is described that solves for the orientation of the animal with respect to a cam era-based coordinate system, giving full kinematic details for the longitudinal wing and body axes from single-view films.
Abstract: Insects in free flight were filmed at 5000 frames per second to determine the motion of their wings and bodies. General comments are offered on flight behaviour and manoeuvrability. Changes in the tilt of the stroke plane with respect to the horizontal provides kinematic control of manoeuvres, analogous to the type of control used for helicopters. A projection analysis technique is described that solves for the orientation of the animal with respect to a cam era-based coordinate system, giving full kinematic details for the longitudinal wing and body axes from single-view films. The technique can be applied to all types of flight where the wing motions are bilaterally symmetrical: forward, backward and hovering flight, as well as properly banked turns. An analysis of the errors of the technique is presented, and shows that the reconstructed angles for wing position should be accurate to within 1-2° in general. Although measurement of the angles of attack was not possible, visual estimations are given. Only 11 film sequences show flight velocities and accelerations that are small enough for the flight to be considered as ‘hovering’. Two sequences are presented for a hover-fly using an inclined stroke plane, and nine sequences of hovering with a horizontal stroke plane by another hover-fly, two crane-flies, a drone-fly, a ladybird beetle, a honey bee, and two bumble bees. In general, oscillations in the body position from its mean motion are within measurement error, about 1-2 % of the wing length. The amplitudes of oscillation for the body angle are only a few degrees, but the phase relation of this oscillation to the wingbeat cycle could be determined for a few sequences. The phase indicates that the pitching moments governing the oscillations result from the wing lift at the ends of the wingbeat, and not from the wing drag or inertial forces. The mean pitching moment of the wings, which determines the mean body angle, is controlled by shifting the centre of lift over the cycle by changing the mean positional angle of the flapping wings. Deviations of the wing tip path from the stroke plane are never large, and no consistent pattern could be found for the wing paths of different insects; indeed, variations in the path were even observed for individual insects. The wing motion is not greatly different from simple harmonic motion, but does show a general trend towards higher accelerations and decelerations at either end of the wingbeat, with constant velocities during the middle of half-strokes. Root mean square and cube root mean cube angular velocities are on average about 4 and 9% lower than simple harmonic motion. Angles of attack are nearly constant during the middle of half-strokes, typically 35° at a position 70 % along the wing length. The wing is twisted along its length, with angles of attack at the wing base some 10-20° greater than at the tip. The wings rotate through about 110° at either end of the wingbeat during 10-20 % of the cycle period. The mean velocity of the wing edges during rotation is similar to the mean flapping velocity of the wing tip and greater than the flapping velocity for more proximal wing regions, which indicates that vortex shedding during rotation is com parable with that during flapping. The wings tend to rotate as a flat plate during the first half of rotation, which ends just before, or at, the end of the half-stroke. The hover-fly using an inclined stroke plane provides a notable exception to this general pattern : pronation is delayed and overlaps the beginning of the downstroke. The wing profile flexes along a more or less localized longitudinal axis during the second half of rotation, generating the ‘flip’ profile postulated by Weis-Fogh for the hover-flies. This profile occurs to some extent for all of the insects, and is not exceptionally pronounced for the hover-fly. By the end of rotation the wings are nearly flat again, although a slight camber can sometimes be seen. Weis-Fogh showed that beneficial aerodynamic interference can result when the left and right wings come into contact during rotation at the end of the wingbeat. His ‘fling’ mechanism creates the circulation required for wing lift on the subsequent half-stroke, and can be seen on my films of the Large Cabbage White butterfly, a plum e moth, and the Mediterranean flour moth. However, their wings ‘peel’ apart like two pieces of paper being separated, rather than fling open rigidly about the trailing edges. A ‘partial fling’ was found for some insects, with the wings touching only along posterior wing areas. A ‘ near fling ’ with the wings separated by a fraction of the chord was also observed for m any insects. There is a continuous spectrum for the separation distance between the wings, in fact, and the separation can vary for a given insect during different manoeuvres. It is suggested that these variants on Weis-Fogh’s fling mechanism also generate circulation for wing lift, although less effectively than a complete fling, and that changes in the separation distance may provide a fine control over the amount of lift produced.

735 citations

Journal ArticleDOI
TL;DR: In this paper, the scaling laws of biological and micro-air vehicles involving wing span, wing loading, vehicle mass, cruising speed, flapping frequency, and power are summarized and discussed.
Abstract: Micro air vehicles (MAVs) with wing spans of 15 cm or less, and flight speed of 30–60 kph are of interest for military and civilian applications. There are two prominent features of MAV flight: (i) low Reynolds number (10 4 –10 5 ), resulting in unfavorable aerodynamic conditions to support controlled flight, and (ii) small physical dimensions, resulting in certain favorable scaling characteristics including structural strength, reduced stall speed, and low inertia. Based on observations of biological flight vehicles, it appears that wing motion and flexible airfoils are two key attributes for flight at low Reynolds number. The small size of MAVs corresponds in nature to small birds, which do not glide like large birds, but instead flap with considerable change of wing shape during a single flapping cycle. With flapping and flexible wings, birds overcome the deteriorating aerodynamic performance under steady flow conditions by employing unsteady mechanisms. In this article, we review both biological and aeronautical literatures to present salient features relevant to MAVs. We first summarize scaling laws of biological and micro air vehicles involving wing span, wing loading, vehicle mass, cruising speed, flapping frequency, and power. Next we discuss kinematics of flapping wings and aerodynamic models for analyzing lift, drag and power. Then we present issues related to low Reynolds number flows and airfoil shape selection. Recent work on flexible structures capable of adjusting the airfoil shape in response to freestream variations is also discussed.

704 citations

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