The Flight of the Treagle : The Origins

History of flight

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Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Walter James Boyne Tom D. Dec 3, See Article History. Those which relate to the generation and application of the power required to drive the machine through the air.

Page 1 of Next page Construction of the sustaining wings: Learn More in these related Britannica articles: Military aircraft , any type of aircraft that has been adapted for military use. Aircraft have been a fundamental part of military power since the midth century.

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Generally speaking, all military aircraft fall into one of the following categories: Airship , a self-propelled lighter-than-air craft. All three types have four principal parts: Airplane , any of a class of fixed-wing aircraft that is heavier than air, propelled by a screw propeller or a high-velocity jet, and supported by the dynamic reaction of the air against its wings. For instance, a cursorial flight model would be energetically less favorable when compared to the alternative hypotheses.

In order to achieve liftoff , Archaeopteryx would have to run faster than modern birds by a factor of three, due to its weight.

Furthermore, the mass of Archaeopteryx versus the distance needed for minimum velocity to obtain liftoff speed is proportional, therefore, as mass increases, the energy required for takeoff increases. Other research has shown that the physics involved in cursorial flight would not make this a likely answer to the origin of avian flight.

Once flight speed is obtained and Archaeopteryx is in the air, drag would cause the velocity to instantaneously decrease; balance could not be maintained due to this immediate reduction in velocity. Hence, Archaeopteryx would have a very short and ineffective flight. In order to effectively trap insects with the wings, Archaeopteryx would require a mechanism such as holes in the wings to reduce air resistance. The decrease in efficiency when looking at the cursorial model is caused by the flapping stroke needed to achieve flight. This stroke motion needs both wings to move in a symmetrical motion, or together.

This is opposed to an asymmetrical motion like that in humans' arms while running. The symmetrical motion would be costly in the cursorial model because it would be difficult while running on the ground, compared to the arboreal model where it is natural for an animal to move both arms together when falling. There is also a large fitness reduction between the two extremes of asymmetrical and symmetrical flapping motion so the theropods would have evolved to one of the extremes. The WAIR hypothesis , a version of the "cursorial model" of the evolution of avian flight, in which birds' wings originated from forelimb modifications that provided downforce, enabling the proto-birds to run up extremely steep slopes such as the trunks of trees, was prompted by observation of young chukar chicks, and proposes that wings developed their aerodynamic functions as a result of the need to run quickly up very steep slopes such as tree trunks, for example to escape from predators.

Note that in this scenario birds need downforce to give their feet increased grip. This provides a model for an evolutionary transition from terrestrial to aerial locomotion as transitional forms incrementally adapted to meet the work and power requirements to scale steeper and steeper inclines using WAIR and the incremental increases from WAIR to flight.

Origin of avian flight

Birds use wing-assisted inclined running from the day they hatch to increase locomotion. This can also be said for birds or feathered theropods whose wing muscles cannot generate enough force to fly, and shows how this behavior could have evolved to help these theropods then eventually led to flight. They begin with wing-assisted incline running and slowly alter their wing strokes for flight as they grow and are able to make enough force.

These transitional stages that lead to flight are both physical and behavioral. The transitions over a hatchling's life can be correlated with the evolution of flight on a macro scale. If protobirds are compared to hatchlings their physical traits such as wing size and behavior may have been similar. Flapping flight is limited by the size and muscle force of a wing.

Even while using the correct model of arboreal or cursorial, protobirds' wings were not able to sustain flight, but they did most likely gain the behaviors needed for the arboreal or cursorial model like today's birds do when hatched. There are similar steps between the two. This lift was found responsible for body acceleration when going up an incline and leads to flight as the bird grows. This model was originally proposed in by Othniel C. The theory states Archaeopteryx was a reptilian bird that soared from tree to tree. After the leap, Archaeopteryx would then use its wings as a balancing mechanism.

According to this model, Archaeopteryx developed a gliding method to conserve energy. Even though an arboreal Archaeopteryx exerts energy climbing the tree, it is able to achieve higher velocities and cover greater distances during the gliding phase, which conserves more energy in the long run than a cursorial bipedal runner.

Conserving energy during the gliding phase makes this a more energy-efficient model. Therefore, the benefits gained by gliding outweigh the energy used in climbing the tree. A modern behavior model to compare against would be that of the flying squirrel. In addition to energy conservation, arboreality is generally associated positively with survival, at least in mammals.

The evolutionary path between arboreality and flight has been proposed through a number of hypotheses. Dudley and Yanoviak proposed that animals that live in trees generally end up high enough that a fall, purposeful or otherwise, would generate enough speed for aerodynamic forces to have an effect on the body. Many animals, even those which do not fly, demonstrate the ability to right themselves and face the ground ventrally, then exhibiting behaviors that act against aerodynamic forces to slow their rate of descent in a process known as parachuting.

Researchers in support of this model have suggested that Archaeopteryx possessed skeletal features similar to those of modern birds. The first such feature to be noted was the supposed similarity between the foot of Archaeopteryx and that of modern perching birds. The hallux , or modified of the first digit of the foot, was long thought to have pointed posterior to the remaining digits, as in perching birds.

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Therefore, researchers once concluded that Archaeopteryx used the hallux as a balancing mechanism on tree limbs. However, study of the Thermopolis specimen of Archeopteryx , which has the most complete foot of any known, showed that the hallux was not in fact reversed, limiting the creature's ability to perch on branches and implying a terrestrial or trunk-climbing lifestyle. In Sweden there is a light and a dark golden syrup, beet based. Golden syrup is a Newtonian fluid. From Wikipedia, the free encyclopedia. Golden syrup Golden syrup's characteristic amber colour.

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Golden syrup's characteristic amber colour.

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