Aerial Maneuvers Research Articles

Decreased feeding ability of a minke whale (Balaenoptera acutorostrata) with entanglement‐like injuries

The effects of nonlethal injuries on the lives of whales are poorly understood. Such effects receive less attention than issues of entanglement frequency and acute mortality. Although fishing gear entanglements are thought to be the largest current threat to whales (Perrin et al. 1994) evidence is limited involving any significant effects that may persist beyond the entanglement period. Here we detail an unusual encounter with a lunge-feeding minke whale (Balaenoptera acutorostrata) with fresh entanglement-like injuries to its head and ventral pouch. Although we cannot be certain of the exact cause of these injuries the laceration strongly resembled a rope injury; it was linear with clean edges and had a width typical of most fishing gear ropes in our study area. We also discuss results from a short-term comparative study that tested whether the whale fed differently than five uninjured minke whales feeding in the same area. This information: (1) quantifies how much a rope-like injury can restrict the expansion of a minke’s ventral pouch while feeding, (2) provides the first minke whale lunge-feeding velocities from a photogrammetric method using digital video, and (3) describes a new lunge-feeding aerial maneuver for minke whales that is possibly associated with the injury.

Courtship dives of Anna's hummingbird offer insights into flight performance limits

Behavioural displays are a common feature of animal courtship. Just as female preferences can generate exaggerated male ornaments, female preferences for dynamic behaviours may cause males to perform courtship displays near intrinsic performance limits. I provide an example of an extreme display, the courtship dive of Anna's hummingbird (Calypte anna). Diving male Anna's hummingbirds were filmed with a combination of high-speed and conventional video cameras. After powering the initial stage of the dive by flapping, males folded their wings by their sides, at which point they reached an average maximum velocity of 385 body lengths s(-1) (27.3 m s(-1)). This is the highest known length-specific velocity attained by any vertebrate. This velocity suggests their body drag coefficient is less than 0.3. They then spread their wings to pull up, and experienced centripetal accelerations nearly nine times greater than gravitational acceleration. This acceleration is the highest reported for any vertebrate undergoing a voluntary aerial manoeuvre, except jet fighter pilots. Stereotyped courtship behaviours offer several advantages for the study of extreme locomotor performance, and can be assessed in a natural context.

Application of Flow Boiling for Thermal Management of Electronics in Microgravity and Reduced-Gravity Space Systems

Large density differences between liquid and vapor create buoyancy effects in the presence of a gravitational field. Such effects can play an important role in two-phase fluid flow and heat transfer, especially critical heat flux (CHF). CHF poses significant risk to electronic devices, and the ability to predict its magnitude is crucial to both the safety and reliability of these devices. Variations in the gravitational field perpendicular to a flow boiling surface can take several forms, from flows at different orientations at 1 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> to the microgravity environment of planetary orbit, to the reduced gravity on the Moon and Mars, and the high <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> 's encountered in fighter aircraft during fast aerial maneuvers. While high coolant velocities can combat the detrimental effects of reduced gravity, limited power budget in space systems imposes stringent constraints on coolant flow rate. Thus, the task of dissipating the heat must be accomplished with the lowest possible flow velocity while safely avoiding CHF. In this paper, flow-boiling CHF is investigated on Earth as well as in reduced gravity parabolic flight experiments using FC-72 as working fluid. CHF showed sensitivity to gravity at low velocities, with microgravity yielding significantly lower CHF values compared to those at 1 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> . Differences in CHF value decreased with increasing flow velocity until a velocity limit was reached above which the effects of gravity became inconsequential. This proves existing data, correlations, and models developed from 1 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e</sub> studies can be employed with confidence to design reduced gravity thermal management systems, provided the flow velocity is maintained above this limit. This paper discusses two powerful predictive tools. The first, which consist of three dimensionless criteria, centers on determination of the velocity limit. The second is a theoretically based model for flow boiling CHF in reduced gravity below this velocity limit.

A novel interacting multiple model algorithm

For maneuvering target tracking, the interacting multiple model (IMM) algorithm employs a fixed model set. The performance of this algorithm depends on the model set adopted. The result of using too many models is as bad as the case of too few models. Therefore, a variable structure IMM (VSIMM) was presented and applied to ground target tracking. This algorithm improves performance and reduces computational load with using auxiliary information. But it is difficult to extend the VSIMM to other scenario (for example, aerial target), where there is not auxiliary information such as a map. A novel interacting multiple model (Novel-IMM) algorithm was presented to solve the problem of model set adaptation without auxiliary information. The Novel-IMM algorithm consists of N independent IMM filters operating in parallel, and each independent IMM filter also consists of multiple sub-filters, which operate interactively. In every time index, only one IMM output of a certain model set is used; but for a long time, the algorithm will alternatively choose an output of the model set to be the optimum final output. The Novel-IMM approach was illustrated in detail with an aerial complex maneuvering target tracking example.

Automated hull reconstruction motion tracking (HRMT) applied to sideways maneuvers of free-flying insects

Flying insects perform aerial maneuvers through slight manipulations of their wing motions. Because such manipulations in wing kinematics are subtle, a reliable method is needed to properly discern consistent kinematic strategies used by the insect from inconsistent variations and measurement error. Here, we introduce a novel automated method that accurately extracts full, 3D body and wing kinematics from high-resolution films of free-flying insects. This method combines visual hull reconstruction, principal components analysis, and geometric information about the insect to recover time series data of positions and orientations. The technique has small, well-characterized errors of under 3 pixels for positions and 5 deg. for orientations. To show its utility, we apply this motion tracking to the flight of fruit flies, Drosophila melanogaster. We find that fruit flies generate sideways forces during some maneuvers and that strong lateral acceleration is associated with differences between the left and right wing angles of attack. Remarkably, this asymmetry can be induced by simply altering the relative timing of flips between the right and left wings, and we observe that fruit flies employ timing differences as high as 10% of a wing beat period while accelerating sideways at 40% g.

Bio-inspired motion detection in an FPGA-based smart camera module

Flying insects, despite their relatively coarse vision and tiny nervous system, are capable of carrying out elegant and fast aerial manoeuvres. Studies of the fly visual system have shown that this is accomplished by the integration of signals from a large number of elementary motion detectors (EMDs) in just a few global flow detector cells. We developed an FPGA-based smart camera module with more than 10 000 single EMDs, which is closely modelled after insect motion-detection circuits with respect to overall architecture, resolution and inter-receptor spacing. Input to the EMD array is provided by a CMOS camera with a high frame rate. Designed as an adaptable solution for different engineering applications and as a testbed for biological models, the EMD detector type and parameters such as the EMD time constants, the motion-detection directions and the angle between correlated receptors are reconfigurable online. This allows a flexible and simultaneous detection of complex motion fields such as translation, rotation and looming, such that various tasks, e.g., obstacle avoidance, height/distance control or speed regulation can be performed by the same compact device.

Wing–wake interaction reduces power consumption in insect tandem wings

Insects are capable of a remarkable diversity of flight techniques. Dragonflies, in particular, are notable for their powerful aerial manoeuvres and endurance during prey catching or territory flights. While most insects such as flies, bees and wasps either reduced their hinds wings or mechanically coupled fore and hind wings, dragonflies have maintained two independent-controlled pairs of wings throughout their evolution. An extraordinary feature of dragonfly wing kinematics is wing phasing, the shift in flapping phase between the fore and hind wing periods. Wing phasing has previously been associated with an increase in thrust production, readiness for manoeuvrability and hunting performance. Recent studies have shown that wing phasing in tandem wings produces a twofold modulation in hind wing lift, but slightly reduces the maximum combined lift of fore and hind wings, compared to two wings flapping in isolation. Despite this disadvantage, however, wing phasing is effective in improving aerodynamic efficiency during flight by the removal of kinetic energy from the wake. Computational analyses demonstrate that this increase in flight efficiency may save up to 22% aerodynamic power expenditure compared to insects flapping only two wings. In terms of engineering, energetic benefits in four-wing flapping are of substantial interest in the field of biomimetic aircraft design, because the performance of man-made air vehicles is often limited by high-power expenditure rather than by lift production. This manuscript provides a summary on power expenditures and aerodynamic efficiency in flapping tandem wings by investigating wing phasing in a dynamically scaled robotic model of a hovering dragonfly.

Inertial Guidance Systems in Insects: From the Neurobiology to the Structural Mechanics of Biological Gyroscopes

ABSTRACT: Flying insects employ a vast array of sensory modalities to coordinate complex aerial maneuvers with incredible speed and acuity. One central feature underlying this is their ability to rapidly acquire and process information about rotational motion. In Diptera (flies), gyroscopic sensing is accomplished with halteres, organs that are derived from hindwings. In Lepidoptera (moths and butterflies), a recent study has suggested that antennae serve this critical function. Here, we review the biomechanical and sensory aspects of these biological gyroscopes. We focus on past and ongoing research to understand how the physical and physiological aspects of these inertial guidance units interact to determine their functional performance.

Sexual Dimorphism in the Hoverfly Motion Vision Pathway

Many insects perform high-speed aerial maneuvers in which they navigate through visually complex surrounds. Among insects, hoverflies stand out, with males switching from stationary hovering to high-speed pursuit at extreme angular velocities [1]. In dipterans, 50-60 large interneurons -- the lobula-plate tangential cells (LPTCs) -- detect changes in optic flow experienced during flight [2-5]. It has been predicted that large LPTC receptive fields are a requirement of accurate "matched filters" of optic flow [6]. Whereas many fly taxa have three horizontal system (HS) LPTC neurons in each hemisphere, hoverflies have four [7], possibly reflecting the more sophisticated flight behavior. We here show that the most dorsal hoverfly neuron (HS north [HSN]) is sexually dimorphic, with the male receptive field substantially smaller than in females or in either sex of blowflies. The (hoverfly-specific) HSN equatorial (HSNE) is, however, sexually isomorphic. Using complex optic flow, we show that HSN, despite its smaller receptive field, codes yaw velocity as well as HSNE. Responses to a target moving against a plain or textured background suggest that the male HSN could potentially play a role in target pursuit under some conditions.

Antennal Mechanosensors Mediate Flight Control in Moths

Flying insects have evolved sophisticated sensory capabilities to achieve rapid course control during aerial maneuvers. Among two-winged insects such as houseflies and their relatives, the hind wings are modified into club-shaped, mechanosensory halteres, which detect Coriolis forces and thereby mediate flight stability during maneuvers. Here, we show that mechanosensory input from the antennae serves a similar role during flight in hawk moths, which are four-winged insects. The antennae of flying moths vibrate and experience Coriolis forces during aerial maneuvers. The antennal vibrations are transduced by individual units of Johnston's organs at the base of their antennae in a frequency range characteristic of the Coriolis input. Reduction of the mechanical input to Johnston's organs by removing the antennal flagellum of these moths severely disrupted their flight stability, but reattachment of the flagellum restored their flight control. The antennae thus play a crucial role in maintaining flight stability of moths.

How Females Keep Male Hoverfly Visual Neurons from Distraction

Legendary athletes like running back Gale Sayers and center fielder Willie Mays earned fame and fortune by pursuing a target traveling at high speeds against a moving, chaotic background. But most animals rely on this evolutionarily honed skill for more fundamental needs. Peregrine falcons snag prey while flying at speeds approaching 100 miles per hour. Males from several fly species chase females during dazzling courtship dances with impressive aerial maneuvers. How the brain accomplishes visual pursuit has been a longstanding question, which becomes even more fascinating when one considers how the tiny nervous system of the male fly executes the visual precision and flight control necessary during courtship chase behavior.

Dynamics of the aerial maneuvers of spinner dolphins

The spinner dolphin (Stenella longirostris) performs spectacular leaps from the water while rotating around its longitudinal axis up to seven times. Although twisting of the body while airborne has been proposed as the mechanism to effect the spin, the morphology of the dolphin precludes this mechanism for the spinning maneuver. A mathematical model was developed that demonstrates that angular momentum to induce the spin was generated underwater, prior to the leap. Subsurface corkscrewing motion represents a balance between drive torques generated by the flukes and by hydrodynamic forces at the pectoral fins, and resistive torques, induced by the drag forces acting on the rotating control surfaces. As the dolphin leaps clear of the water, this balance is no longer maintained as the density of the air is essentially negligible, and a net drive torque remains, which permits the dolphin's rotation speed to increase by as much as a factor of three for a typical specimen. The model indicates that the high rotation rates and orientation of the dolphin's body during re-entry into the water could produce enough force to hydrodynamically dislodge unwanted remoras.

Bats Have a Feel for Flight

Even in total darkness, bats can execute complex aerial maneuvers to capture prey, thanks to their famed sonarlike skill of echolocation. At the Society for Neuroscience meeting in Washington, D.C., however, a researcher suggested that a long-ignored feature of bats' wings also helps the creatures perform midair acrobatics and catch insects.

Contest behaviour in the speckled wood butterfly (Pararge aegeria): seasonal phenotypic plasticity and the functional significance of flight performance

Although contemporary animal contest theory emphasises the importance of physical asymmetries in resolving disputes, such asymmetries do not obviously settle fights in all groups. Territorial male butterflies, for example, compete via elaborate non-contact aerial interactions in which success is determined by relative persistence. Prior research suggests that the resolution of these contests is not clearly related to physical variables such as body size or energy reserves. However, given that the contests involve elaborate aerial manoeuvres, one long-standing suggestion is that asymmetries in flight performance, and thus flight morphology, may be important. We addressed this hypothesis via a manipulative investigation into the biophysical correlates of contest success in the speckled wood butterfly, Pararge aegeria. This species possesses the ability for significant adaptive phenotypic plasticity in relevant flight morphological parameters. We took advantage of this plasticity to rear 90 individuals of markedly varying flight morphologies, which we then pitted against each other in a semi-controlled experimental fashion. Multiple logistic and lognormal analyses provided little evidence for the relevance of morphological parameters, including relative flight musculature, wing loading and wing aspect ratio (wing length relative to area), to the outcome and/or duration of experimental contests. Instead, we found a positive effect of age upon contest success. Given that ability for high acceleration is strongly linked to variation in these morphological parameters, our findings suggest that flight performance is not a strong determinant of resource-holding potential in this notably territorial butterfly.

The influence of livestock grazing and weed invasion on habitat use by birds in grassy woodland remnants

Remnants of native vegetation in regions dominated by agriculture are subject to degradation, especially by livestock grazing and weed invasion. Ground-foraging birds are amongst the most threatened bird groups in Australia, and these agents of degradation might be contributing to their decline by causing a reduction in food availability. We studied the foraging behaviour and microhabitat use of seven species of ground-foraging insectivores in south-eastern Australian buloke woodland remnants with native, grazed and weedy ground-layers. If birds must resort to using more energetically expensive prey-attack manoeuvres, or selectively use substrates and microhabitats that are less available in degraded habitats, then such degradation is likely to be negatively impacting on these species. We found evidence of a negative impact of one or both of these types of degradation on five of the seven bird species. Three species that employ a range of foraging manoeuvres to attack prey used potentially more energetically expensive aerial manoeuvres significantly more frequently in weedy remnants than in remnants with a native or grazed ground layer. Red-capped robins Petroica goodenovii and brown treecreepers Climacteris picumnus both selectively foraged near trees in grazed sites, and hooded robins Melanodryas cucullata, red-capped robins and willie wagtails Rhipidura leucophrys avoided foraging in microhabitats with a high percentage cover of exotic grasses in weedy sites. Brown treecreepers were also less likely to be present in weedy sites that had been protected from grazing than in either grazed or native sites. These results suggest that although grazing appears to have a detrimental impact on foraging habitat of ground-foraging birds, the exclusion of livestock grazing from previously disturbed buloke remnants alone is not adequate to restore habitat values for ground-foraging birds. A conservation strategy for this habitat type should consider the exclusion of heavy grazing from sites with an intact cryptogamic crust and the management of weeds in disturbed remnants, potentially through the use of carefully controlled light grazing.

Edward H. Lambert, MD, PhD (1915–2003)

Dr. Edward H. Lambert, one of the icons of neurology in the United States, died July 27, 2003 in Rochester, Minnesota at the age of 88 years. He was a major force in developing many of our current concepts of nerve and muscle disorders. His work in neuromuscular clinical neurophysiology—EMG—established it as one of the important subspecialty areas of neurology. As a teacher, he influenced generations of neurologists, many who have become leaders in the arena of neuromuscular diseases. Dr. Lambert was born in Minneapolis on August 30, 1915. After 2 years at Morton Junior College, he was accepted to medical school at the University of Illinois in 1934, completed his MD degree in 1938, and was awarded BS and MS degrees for research studies done during that period. After an internship at Michael Reese Hospital, he commenced his PhD in physiology at the University of Illinois. His thesis dealt with the effects of oxygen and carbon dioxide concentrations on blood pressure and the vasomotor system. He joined the Mayo Clinic in 1943 and devoted his creative energies to finding the cause and a means for preventing the catastrophic occurrence of syncope in aviators experiencing high G-forces during aerial maneuvers. His role as a principal investigator, initially using the Mayo human centrifuge, included the development of the G-suit for aviators and resulted in his receipt of the Presidential Certificate of Merit in 1947. He served as one of his own research subjects on numerous …

Insect behaviour: Motion camouflage in dragonflies.

Most animals can skilfully conceal themselves when stationary1, but they may become apparent as soon as they move. Here we use stereo cameras to reconstruct the movements in three dimensions of dragonflies (Hemianax papuensis), and show that these insects actively use motion camouflage to disguise themselves as stationary during territorial aerial manoeuvres. Deployment of this sophisticated technique by the oldest airborne predator tricks the victim's retina into perceiving the stalker as stationary even while it darts about in pursuit.

Mechanisms and Implications of Animal Flight Maneuverability

Accelerations and directional changes of flying animals derive from interactions between aerodynamic force production and the inertial resistance of the body to translation and rotation. Anatomical and allometric features of body design thus mediate the rapidity of aerial maneuvers. Both translational and rotational responsiveness of the body to applied force decrease with increased total mass. For flying vertebrates, contributions of the relatively heavy wings to whole-body rotational inertia are substantial, whereas the relatively light wings of many insect taxa suggest that rotational inertia is dominated by the contributions of body segments. In some circumstances, inertial features of wing design may be as significant as are their aerodynamic properties in influencing the rapidity of body rotations. Stability in flight requires force and moment balances that are usually attained via bilateral symmetry in wingbeat kinematics, whereas body roll and yaw derive from bilaterally asymmetric movements of both axial and appendicular structures. In many flying vertebrates, use of the tail facilitates the generation of aerodynamic torques and substantially enhances quickness of body rotation. Geometrical constraints on wingbeat kinematics may limit total force production and thus accelerational capacity in certain behavioral circumstances. Unitary limits to animal flight performance and maneuverability are unlikely, however, given varied and context-specific interactions among anatomical, biomechanical, and energetic features of design.

What are the health hazards of snowboarding?

First introduced in the 1920s with little success, snowboarding is now one of the fastest growing winter sports in the world. In the 1999-2000 season, 3.3 million snowboarders contributed about 13.5 million visits to US ski resorts, representing 27% of total days on the snow. Many resorts now have special areas set aside just for snowboarding. These areas, called pipelines, are wide semicylindrical “shoots” carved out of snow. They are up to several hundred feet long with high vertical walls that allow snowboarders to ride from side to side. They are designed for “jumps and bumps” (aerial maneuvers and acrobatics). The typical snowboarder is a male adolescent, although the age range is widening and the proportion of female snowboarders is increasing.1 ​,​, Table 1 Shoulder injuries associated with snowboarding9 Dislocation Acromioclavicular separation Fracture of the clavicle Rotator cuff strain Fracture of the proximal humerus View it in a separate window Table 2 Management of shoulder and elbow injuries associated with snowboarding7 Refer to an orthopedist if fracture involves the growth plate (Salter-Harris type III or higher) Perform a neurovascular examination before and after reduction of a dislocation Assess reduction of dislocation radiographically Consider surgical stabilization of dislocations in young patients involved in collision sports10 View it in a separate window HOW COMMON ARE INJURIES? With the increasing popularity of snowboarding, injuries—the predominant health hazard associated with the sport—are seen more often than in the past. About 27,000 injuries related to the sport occurred in the United States in 1994. While most injuries are treated by health care personnel close to ski resorts, primary care physicians often provide follow-up care and can be instrumental in the primary prevention of injuries. The reported injury rate varies from 3.5 per 1,000 snowboard days to more than 40 per 1,000 snowboard days.2,3 Mortality rates are low (0.2 per million snowboarding days).1 Recent cohort studies suggest that the rate4 and severity3 of injuries among snowboarders are higher than among alpine skiers of similar levels of ability. Forty-two percent of snowboard injuries, compared with only 16% of ski injuries, were considered emergent (defined as necessitating immediate medical intervention, including fractures, concussions with any loss of consciousness, dislocations, and lost teeth). Concussions and wrist fractures accounted for most of the difference in emergent injuries between the 2 groups.3

Deployment of biosonar in diverse tasks by FM echolocating bats

Using an infrared body-heat-imaging video camera and a microphone array, we made field recordings of FM echolocating bats (Eptesicus, Myotis, Pipistrellus) while they deployed their sonar alone or in company with other bats. We observed cruising flights of bats in transit from roosts to feeding areas, bats flying low over water for drinking or hunting, and aerial interception maneuvers in open areas (larger insects were visible, too). However, we also recorded frequent captures of insects on or near the ground, flights into vegetation to capture beetles, and groups of bats flying in close proximity while drinking or making aerial captures of insects. Bat-to-bat dogfights were common, some involving two or more bats diving and violently maneuvering close to the ground or near vegetation. For single bats or several bats not very close to each other, we recorded typical interception maneuvers with pursuit sequences consisting of search-, approach- (tracking-), and terminal-stage signals. By reconstruction of flight and emission patterns, we found that bats flying in close proximity alternated their broadcasts, and large aggregations of bats feeding close together perpetually emitted sounds characteristic of the mid-approach stage, with short durations, high repetition rates, and no discernible terminal stages.