Feather variations

Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates,^[1][2] and indeed a premier example of a complex evolutionary novelty.^[3] They are among the characteristics that distinguish the extant Aves from other living groups. Feathers have also been noticed in those Theropoda which have been termed feathered dinosaurs. Although feathers cover most parts of the body of birds, they arise only from certain well-defined tracts on the skin. They aid in flight, thermal insulation, waterproofing and coloration that helps in communication and protection.^[4]

Structure and characteristics[link]

Parts of a feather:
1. Vane
2. Rachis
3. Barb
4. Afterfeather
5. Hollow shaft, calamus

Feather structure of a Blue-and-yellow Macaw

Feathers are among the most complex integumentary appendages found in vertebrates and are formed in tiny follicles in the epidermis, or outer skin layer, that produce keratin proteins. The β-keratins in feathers, beaks and claws — and the claws, scales and shells of reptiles — are composed of protein strands hydrogen-bonded into β-pleated sheets, which are then further twisted and crosslinked by disulfide bridges into structures even tougher than the α-keratins of mammalian hair, horns and hoof.^[5][6] The exact signals that induce the growth of feathers on the skin are not known but it has been found that the transcription factor cDermo-1 induces the growth of feathers on skin and scales on the leg.^[7]

Feather microstructure showing interlocking barbules.

Classification[link]

There are two basic types of feather: vaned feathers which cover the exterior of the body, and down feathers which are underneath the vaned feathers. The pennaceous feathers are vaned feathers. Also called contour feathers, pennaceous feathers arise from tracts and cover the whole body. A third rarer type of feathers, filoplumes, is hairlike and (if present in a bird) grows along the fluffy down feathers. In some passerines, filoplumes arise exposed beyond the contour feathers on the neck.^[1] The remiges, or flight feathers of the wing, and rectrices, the flight feathers of the tail are the most important feathers for flight. A typical vaned feather features a main shaft, called the rachis. Fused to the rachis are a series of branches, or barbs; the barbs themselves are also branched and form the barbules. These barbules have minute hooks called barbicels for cross-attachment. Down feathers are fluffy because they lack barbicels, so the barbules float free of each other, allowing the down to trap much air and provide excellent thermal insulation. At the base of the feather, the rachis expands to form the hollow tubular calamus (or quill) which inserts into a follicle in the skin. The basal part of the calamus is without vanes. This part is embedded within the skin follicle and has an opening at the base (proximal umbilicus) and a small opening on the side (distal umbilicus).^[8]

Hatchling birds of some species have a special kind of natal down (neossoptiles) and these are pushed out when the normal feathers (teleoptiles) emerge.^[1]

Flight feathers are stiffened so as to work against the air in the downstroke but yield in other directions. It is noted that the pattern of orientation of β-keratin fibers in the feathers of flying birds differs from that in flightless birds. The fibers are better aligned in the middle of the feather and less aligned towards the tips.^[9][10]

Functions[link]

Feathers insulate birds from water and cold temperatures. They may also be plucked to line the nest and provide insulation to the eggs and young. The individual feathers in the wings and tail play important roles in controlling flight. Some species have a crest of feathers on their heads. Although feathers are light, a bird's plumage weighs two or three times more than its skeleton, since many bones are hollow and contain air sacs. Color patterns serve as camouflage against predators for birds in their habitats, and by predators looking for a meal. As with fish, the top and bottom colors may be different to provide camouflage during flight. Striking differences in feather patterns and colors are part of the sexual dimorphism of many bird species and are particularly important in selection of mating pairs. In some cases there are differences in the UV reflectivity of feathers across sexes even though no differences in color are noted in the visible range.^[11] The wing feathers of male Club-winged Manakins Machaeropterus deliciosus have special structures that are used to produce sounds by stridulation.^[12]

A contour feather from a Guinea fowl

Some birds have a supply of powder down feathers which grow continuously, with small particles regularly breaking off from the ends of the barbules. These particles produce a powder that sifts through the feathers on the bird's body and acts as a waterproofing agent and a feather conditioner. Powder down has evolved independently in several taxa and can be found in down as well as pennaceous feathers. They may be scattered in plumage in the pigeons and parrots or in localized patches on the breast, belly or flanks as in herons and frogmouths. Herons use their bill to break the feathers and to spread them while cockatoos may use their head as a powder puff to apply the powder.^[13] Waterproofing can be lost by exposure to emulsifying agents due to human pollution. Feathers can become waterlogged and birds may sink. It is also very difficult to clean and rescue birds whose feathers have been fouled by oil spills. The feathers of cormorants soak up water and help in reducing buoyancy and thereby allowing the birds to swim submerged.^[14]

Rictal bristles of a White-cheeked Barbet

Bristles are stiff, tapering feathers with a large rachis but few barbs. Rictal bristles are bristles found around the eyes and bill. They may serve a similar purpose to eyelashes and vibrissae in mammals. It has been suggested that they may aid insectivorous birds in prey capture or that it may have sensory functions, however there is no clear evidence.^[15] In one study, Willow Flycatchers (Empidonax traillii) were found to catch insects equally well before and after removal of the rictal bristles.^[16]

Grebes are peculiar in their habit of ingesting their own feathers and also feeding them to their young. Observations on the diet and feather eating frequency suggest that ingesting feathers particularly down from their flanks aids in forming easily ejectable pellets along with their diet of fish.^[17]

Distribution[link]

Feather tracts or pterylae and their naming

Contour feathers are not uniformly distributed on the skin of the bird except in some groups such as the Penguins, ratites and screamers.^[18] In most birds the feathers grow from specific tracts of skin called pterylae while there are regions which are free of feathers called apterylae. Filoplumes and down may arise from the apteriae, regions between the pterylae. The arrangement of these feather tracts, pterylosis or pterylography, varies across bird families and has been used in the past as a means for determining the evolutionary relationships of bird families.^[19][20]

Coloration[link]

Colors resulting from different feather pigments
Left: turacin (red) and turacoverdin (green, with some structural blue iridescence at lower end) on the wing of Tauraco bannermani
Right: carotenoids (red) and melanins (dark) on belly/wings of Ramphocelus bresilius

The colors of feathers are produced by the presence of pigments, or by microscopic refractive structures, or by a combination of both.

Most feather pigments are melanins (brown and beige pheomelanins, black and grey eumelanins) and carotenoids (red, yellow, orange); other pigments occur only in certain taxa – the yellow to red psittacofulvins^[21] (found in some parrots) and the red turacin and green turacoverdin (porphyrin pigments found only in turacos). Structural coloration^[4][22][23] is involved in the production of blue colors, iridescence, most ultraviolet reflectance and in the enhancement of pigmentary colors; structural iridescence has been reported^[24] in fossil feathers dating back 40 million years. White feathers lack pigment and scatter light diffusely; albinism in birds is caused by defective pigment production, though structural coloration will not be affected (as can be seen e.g. in blue-and-white budgerigars).

A feather with no pigment

For example, the blues and bright greens of many parrots are produced by constructive interference of light reflecting from different layers of the structures in feathers, in the case of green plumage in addition to the yellow pigments; the specific feather structure involved is sometimes called the Dyck texture.^[25][26] Melanin is often involved in the absorption of some of the light; in combination with yellow pigment it produces dull olive-greens.

In some birds, the feather colors may be created or altered by uropygial gland secretions. The yellow bill colors of many hornbills are produced by preen gland secretions. Other differences that may only be visible in the ultraviolet region have been suggested^[13] but studies have failed to find evidence.^[27] Uropygial oil secretion may also have an inhibitory effect on feather bacteria.^[28]

A bird's feathers undergo wear and tear and are replaced periodically during its life through molting. New feathers, known as blood, or pin feathers (depending on the stage of growth) when developing, are formed through the same follicle from which the old ones were fledged. The presence of melanin in feathers increases their resistance to abrasion.^[29] One study notes that melanin based feathers were observed to degrade more quickly under bacterial action, even compared to unpigmented feathers from the same species, than those unpigmented or with carotenoid pigments.^[30] However, another study the same year compared the action of bacteria on pigmentations of two song sparrow species and observed that the darker pigmented feathers were more resistant and they cited other research also published in 2004 that stated increased melanin provided greater resistance. They observed that the greater resistance of the darker birds confirmed Gloger's rule.^[31] The evolution of coloration is based on sexual selection and it has been suggested that carotenoid-based pigments may have evolved since they are likely to be more honest signals of fitness because they are derived from special diets,^[32][33] or because carotenoids are also required for immune function.^[34]

Parasites[link]

The feather surface is the home for some ectoparasites, notably feather lice (Phthiraptera) and feather mites. Feather lice typically live on a single host and can move only from parents to chicks or mating birds and occasionally by phoresy. This life history has resulted in most of the species being specific to the host and coevolving with the host, making them of interest in phylogenetic studies.^[35]

Feather holes are chewing traces of lice (most probably Brueelia spp. lice) on the wing and tail feathers. They were described on barn swallows, and because of easy countability, many evolutionary, ecological, and behavioral publications use them to quantify the intensity of infestation.

Interestingly, parasitic cuckoos which grow up in the nests of other species also have host specific feather lice and these seem to be transmitted only after they leave the host nest.^[36]

Birds maintain their feather condition by bathing in water, dust bathing and preening. A peculiar behavior of birds, anting, where ants are introduced into the plumage was suggested to help in reducing parasites but no supporting evidence has been found.^[37]

Human usage[link]

Part of Indian Peacock tail feather

Feathers have a number of utilitarian, cultural and religious uses.

Utilitarian functions[link]

Feathers are both soft and excellent at trapping heat; thus, they are sometimes used in high-class bedding, especially pillows, blankets, and mattresses. They are also used as filling for winter clothing, such as quilted coats and sleeping bags; goose and eider down have great loft, the ability to expand from a compressed, stored state to trap large amounts of compartmentalized, insulating air.^[38]

Bird feathers have long been used for fletching arrows. Colorful feathers such as those belonging to pheasants have been used to decorate fishing lures.

Feathers of large birds (most often geese) have been and are used to make quill pens. The word pen itself is derived from the Latin penna for feather.^[39] In French, plume can mean either feather or pen.

Feathers are also valuable in aiding the identification of species in forensic studies, particularly in bird strikes to aircraft. The ratios of hydrogen isotopes in feathers help in determining the geographic origins of birds.^[40] Feathers may also be useful in the non-destructive sampling of pollutants.^[41]

The poultry industry produces a large amount of feathers as waste, and like other forms of keratin, these are slow in their decomposition. Feather waste has been used in a number of industrial applications as a medium for culturing microbes,^[42] biodegradeable polymers,^[43] and production of enzymes.^[44] Feather proteins have been tried as an adhesive for wood board.^[45]

The hunting of birds for decorative and ornamentatal feathers (including in Victorian fashion) has endangered some species.^{[citation needed]}

In religion and culture[link]

Eagle feathers have great cultural and spiritual value to American Indians in the USA and First Nations peoples in Canada as religious objects. In the United States the religious use of eagle and hawk feathers are governed by the eagle feather law, a federal law limiting the possession of eagle feathers to certified and enrolled members of federally recognized Native American tribes.

In South America, brews made from the feathers of condors are used in traditional medications.^[46] In India, feathers of the Indian Peacock have been used in traditional medicine for snakebite, infertility and coughs.^[47][48]

During the 18th, 19th, and 20th centuries a booming international trade in plumes, to satisfy market demand in North America and Europe for extravagant head-dresses as adornment for fashionable women, caused so much destruction (for example, to egret breeding colonies) that a major campaign against it by conservationists led to the Lacey Act and caused the fashion to change and the market to finally collapse. Frank Chapman noted in 1886 that as many as 40 species of birds were used in about three-fourths of the 700 ladies' hats that he observed in New York City.^[49][50][51]

More recently, rooster plumage has become a popular trend as a hairstyle accessory, with feathers formerly used solely as fishing lures being now used to provide color and style to hair.^[52] Modern feather usage in fashion and also adorning military regimental headresses and cloths are derived as a waste product of farming of poultry birds, this includes chicken, geese, turkey, pheasant and ostrich. Feathers used for these purposes are deliberately modified through dyeing and manipulation to enhance the appearance of these poultry feathers, as they are naturally often dull in appearance compared to wild species which they are attempting to mimic. The number of feather products manufacturers in Europe has decreased enormously in the last 60 years mainly due to competition from Asia. One surviving company Jaffe et fils founded in 1946, formerly of London now based in Axminster, Devon is one of the last in Europe to dye and manufacture feather products for fashion, theatre and military regalia. Feathers have adorn hats at many prestigious events such as Weddings and Ladies day at Race courses(Royal Ascot). One milliner, Philip Treacy, has specialized in the use of feathers. He has created highly regarded hats notably for the Royal Family. One such as the hat was worn by the Camilla now the Duchess of Cornwall on her marriage to Prince Charles.

Evolution[link]

Fossil feather of Archaeopteryx

The functional view on the evolution of feathers has traditionally focused on insulation, flight and display. Discoveries of non-flying Late Cretaceous feathered dinosaurs in China however suggest that flight could not have been the original primary function.^[53] There have been suggestions that feathers may have had their original function in thermoregulation, waterproofing or even as sinks for metabolic wastes such as sulphur.^[54] Recent discoveries are claimed to support a thermoregulatory function, at least in smaller dinosaurs.^[55][56] While feathers have been suggested as having evolved from reptilian scales, there are numerous objections, and more recent explanations have arisen from the paradigm of evolutionary developmental biology.^[2] Theories of the scale-based origins of feathers suggest that the planar scale structure was modified for their development into feathers by splitting to form the webbing; however, the developmental process involves a tubular structure arising from a follicle and the tube splitting longitudinally to form the webbing.^[1][2] The number of feathers per unit area of skin is higher in smaller birds than in larger birds, and this trend indicates their important role in thermal insulation, since smaller birds lose more heat due to the relatively larger surface area in proportion to their body weight.^[4] The miniaturization of birds also played a role in the evolution of powered flight.^[57] The coloration of feathers is believed to be primarily evolved in response to sexual selection. In many cases the physiological condition of the birds (especially males) is indicated by the quality of their feathers and this is used (by the females) in mate choice.^[58][59]

Feathered dinosaurs[link]

Archaeopteryx lithographica (Berlin specimen)

Several non-avian dinosaurs had feathers on their limbs that would not have functioned for flight.^[2] One theory is that feathers originally evolved on dinosaurs as a result of insulation properties; those small dinosaurs that then grew longer feathers may have found them helpful in gliding, leading to the evolution of proto-birds like Archaeopteryx and Microraptor zhaoianus. Dinosaurs that had feathers or protofeathers include Pedopenna daohugouensis,^[60] and Dilong paradoxus, a tyrannosauroid which is 60 to 70 million years older than Tyrannosaurus rex.^[61]

The majority of dinosaurs known to have had feathers or protofeathers are saurischians, however featherlike "filamentous integumentary structures" are also known from the ornithischians Tianyulong and Psittacosaurus.^[62] The exact nature of these structures is still under study. However, it is believed that the stage 1 feathers such as those seen in these two ornithischians likely functioned in display.^[63]

Since the 1990s, dozens of feathered dinosaurs have been discovered in the clade Maniraptora, which includes the clade Avialae and the recent common ancestors of birds, Oviraptorosauria and Deinonychosauria. In 1998, the discovery of a feathered oviraptorosaurian, Caudipteryx zoui, challenged the notion that feathers were an exclusive structure of Avialae.^[64] Buried in the Yixian Formation in Liaoning, China, C. zoui lived during the Early Cretaceous Period. Present on the forelimbs and tails, their integumentary structure has been accepted as pennaceous vaned feathers based on the rachis and herringbone pattern of the barbs. In the clade Deinonychosauria, the continued divergence of feathers is also apparent in the families Troodontidae and Dromaeosauridae. Branched feathers with ranchis, barbs, and barbules were discovered in many members including Sinornithosaurus millenii, a dromaeosaurid found in the Yixian formation (124.6 MYA).^[65]

Previously, a temporal paradox existed in the evolution of feathers—theropods with highly derived bird-like characteristics occurred at a later time than Archaeopteryx—suggesting that the descendants of birds arose before the ancestor. However, this paradox was resolved in 2009 with the discovery of Anchiornis huxleyi, found in the Late Jurassic Tiaojishan Formation (160 MYA) in western Liaoning.^[66][67] By predating Archaeopteryx, Anchornis proves the existence of a modernly feathered theropod ancestor, providing insight into the dinosaur-bird transition. The specimen shows distribution of large pennaceous feathers on the forelimbs and tail, implying that pennaceous feathers spread to the rest of the body at an earlier stage in theropod evolution.^[68] The discovery, in 2011, of feathers preserved in amber, within samples dating to 80 mya, suggests the coexistence of theropods and birds, with both theropod and avian feather types commingled in the samples.^[69]

Evolutionary stages[link]

Diagram illustrating stages of evolution

Several studies of feather development in the embryos of modern birds, coupled with the distribution of feather types among various prehistoric bird precursors, have allowed scientists to attempt a reconstruction of the sequence in which feathers first evolved and developed into the types found on modern birds.

Feather evolution was broken down into the following stages by Xu and Guo in 2009:^[63]

1. Single filament
2. Multiple filaments joined at their base
3. Multiple filaments joined at their base to a central filament
4. Multiple filaments along the length of a central filament
5. Multiple filaments arising from the edge of a membranous structure
6. Pennaceous feather with vane of barbs and barbules and central rachis
7. Pennaceous feather with an asymmetrical rachis
8. Undifferentiated vane with central rachis

However, Foth (2011) showed that some of these purported stages (stages 2 and 5 in particular) are likely simply artifacts of preservation caused by the way fossil feathers are crushed and the feather remains or imprints are preserved. Foth re-interpreted stage 2 feathers as crushed or misidentified feathers of at least stage 3, and stage 5 feathers as crushed stage 6 feathers.^[70]

The following simplified diagram of dinosaur relationships follows these results, and shows the likely distribution of plumaceous (downy) and pennaceous (vaned) feathers among dinosaurs and prehistoric birds. The diagram follows one presented by Xu and Guo (2009) modified with the findings of Foth (2011).^[63] The numbers accompanying each name refer to the presence of specific feather stages. Note that 's' indicates the known presence of scales on the body.

See also[link]

• Pinioning

References[link]

External links[link]

Wikimedia Commons has media related to: Feather

• Chandler, Asa C. (1916). "A study of the structure of feathers, with reference to their taxonomic significance". University of Caliornia Publications in Zoology 13 (1): 243-446. http://archive.org/stream/cu31924000147953#page/n41/mode/1up/. </ref>
• McGraw, K. J. 2005. Polly want a pigment? Cracking the chemical code to red coloration in parrots. Australian Birdkeeper Magazine 18:608-611.
• DeMeo, Antonia M. Access to Eagles and Eagle Parts: Environmental Protection v. Native American Free Exercise of Religion (1995)
• Electronic Code of Federal Regulations (e-CFR), Title 50: Wildlife and Fisheries PART 22—EAGLE PERMITS
• U.S. v. Thirty Eight Golden Eagles (1986)
• Mechanical structure of feathers
• Documentary on the evolution of feathers
• Lecture notes on the avian integument
• U.S. National Fish and Wildlife Forensics Laboratory's Feather Atlas
• Federn.org

U.S. Navy F/A-18 breaking the sound barrier. The white halo formed by condensed water droplets is thought to result from a drop in air pressure around the aircraft at transonic speeds (see Prandtl-Glauert Singularity).^[1][2]

1. Subsonic
2. Mach 1
3. Supersonic
4. Shock wave

The sound barrier, in aerodynamics, is the point at which an aircraft moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several unrelated aerodynamic effects that "struck" their planes like an impediment to further acceleration. By the 1950s, new aircraft designs routinely "broke" the sound barrier.^{[N 1]}

History[link]

Some common whips such as the bullwhip or sparewhip are able to move faster than sound: the tip of the whip breaks the sound barrier and causes a sharp crack—literally a sonic boom.^[3] Firearms since the 19th century have generally had a supersonic muzzle velocity.

The sound barrier may have been first breached in nature some 150 million years ago. Some paleobiologists report that, based on computer models of their biomechanical capabilities, certain long-tailed dinosaurs such as Apatosaurus and Diplodocus may have possessed the ability to flick their tails at supersonic velocities, possibly used to generate an intimidating booming sound. This finding is theoretical and disputed by others in the field.^[4] Meteorites entering the Earth's atmosphere usually, if not always, descend faster than sound.

Early problems[link]

The tip of the propeller on many early aircraft may reach supersonic speeds, producing a noticeable buzz that differentiates such aircraft. This is particularly noticeable on the Stearman, and noticeable on the T-6 Texan when it enters a sharp-breaking turn. This is undesirable, as the transonic air movement creates disruptive shock waves and turbulence. It is due to these effects that propellers are known to suffer from dramatically decreased performance as they approach the speed of sound. It is easy to demonstrate that the power needed to improve performance is so great that the weight of the required engine grows faster than the power output of the propeller. This problem was one of the issues that led to early research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany, who were led to their research specifically in order to avoid these problems in high-speed flight.

Nevertheless, propeller aircraft were able to approach the speed of sound in a dive. Unfortunately, doing so led to numerous crashes for a variety of reasons. For instance, pilots flew full power into terrain because the rapidly increasing forces acting on the control surfaces of their aircraft- most infamously, the Mitsubishi Zero^{[citation needed]}- overpowered them. In its case, several attempts to fix it only made the problem worse. Likewise, the flexing caused by the low torsional stiffness of the Supermarine Spitfire's wings caused them, in turn, to counteract aileron control inputs, leading to a condition known as control reversal. This was solved in later models with changes to the wing. Worse still, a particularly dangerous interaction of the airflow between the wings and tail surfaces of diving P-38 Lightning's made "pulling out" of dives difficult; however, the problem was later solved by the addition of a "dive flap" that upset the airflow under these circumstances. Flutter due to the formation of shock waves on curved surfaces was another major problem, which led most famously to the breakup of de Havilland Swallow and death of its pilot, Geoffrey de Havilland, Jr.

All of these effects, although unrelated in most ways, led to the concept of a "barrier" that makes it difficult for an aircraft to break the speed of sound. ^{[N 2]}

Early claims[link]

There are, however, several claims that the sound barrier was broken during World War II. Hans Guido Mutke claimed to have broken the sound barrier on 9 April 1945 in a Messerschmitt Me 262. Mutke reported not just transonic buffeting but the resumption of normal control once a certain speed was exceeded, then a resumption of severe buffeting once the Me 262 slowed again. He also reported engine flame out. However, this claim is widely disputed by various experts believing the Me 262's structure could not support high transonic, let alone supersonic flight.^[6] The lack of area ruled fuselage and 10 percent thick wings did not prevent other aircraft from exceeding Mach 1 in dives. Chuck Yeager's Bell X-1, the North American F-86 Sabre (with Me-262 profile ^[7][8]) and the Convair Sea Dart seaplane exceeded Mach 1 without area rule fuselages. Computational tests carried out by Professor Otto Wagner of the Munich Technical University in 1999 suggest the Me 262 was capable of supersonic flight during steep dives. Recovering from the dive and the resumption of severe buffeting once subsonic flight was resumed would have been very likely to damage the craft terminally.

On page 13 of the "Me 262 A-1 Pilot's Handbook" issued by Headquarters Air Materiel Command, Wright Field, Dayton, Ohio as Report No. F-SU-1111-ND on January 10, 1946:

Speeds of 950 km/h (590 mph) are reported to have been attained in a shallow dive 20° to 30° from the horizontal. No vertical dives were made. At speeds of 950 to 1,000 km/h (590 to 620 mph) the air flow around the aircraft reaches the speed of sound, and it is reported that the control surfaces no longer affect the direction of flight. The results vary with different airplanes: some wing over and dive while others dive gradually. It is also reported that once the speed of sound is exceeded, this condition disappears and normal control is restored.

The comments about restoration of flight control and cessation of buffeting above Mach 1 are very significant in a 1946 document.

In his book Me-163, former Messerschmitt Me 163 "Komet" pilot Mano Ziegler claims that his friend, test pilot Heini Dittmar, broke the sound barrier when steep diving the rocket plane and that several people on the ground heard the sonic booms. Heini Dittmar had been accurately and officially recorded at 1,004.5 km/h (623.8 mph) in level flight on 2 October 1941 in the prototype Me 163 V4. He reached this speed at less than full throttle, as he was concerned by the transonic buffeting. The craft's Walter RII-203 cold rocket engine produced 7.34 kN (750 kgp / 1,650 lbf) thrust. The flight was made after a drop launch from a carrier plane to conserve fuel, a record that was kept secret until the war's end. The craft's potential performance in a powered dive is unknown, but the Me 163B test version of the series rocket plane had an even more powerful engine (HWK 109-509 A-2) and a greater wing sweep than the Me 163A. Ziegler claims that on 6 July 1944, Heini Dittmar, flying a test Me 163 B V18 VA + SP, was measured traveling at a speed of 1,130 km/h.^[9]

Similar claims for the Spitfire and other propeller aircraft are more suspect. It is now known that traditional airspeed gauges using a pitot tube give inaccurately high readings in the transonic regime, apparently due to shock waves interacting with the tube or the static source. This led to problems then known as "Mach jump^[10]

Attempts to break the sound barrier[link]

The first powered flight faster than sound may have been the Soviet ramjet experiments of Yuri Pobedonostsev in 1933. Phosphorus-powered ramjets achieved speeds of 600–680 meters/second (Mach 2).^[11] Another early vehicle to break the sound barrier was probably the first successful test launch of the German V-2 ballistic missile on 3 October 1942, at Peenemünde in Germany. By September 1944, the V-2s routinely achieved Mach 4 (1,200 m/s) during terminal descent.

In 1942 the United Kingdom's Ministry of Aviation began a top secret project with Miles Aircraft to develop the world's first aircraft capable of breaking the sound barrier. The project resulted in the development of the prototype Miles M.52 jet aircraft, which was designed to reach 1,000 mph (417 m/s; 1,600 km/h) at 36,000 ft (11 km) in 1 minute 30 sec.

The aircraft's design introduced many innovations which are still used on today's supersonic aircraft. The single most important development was the all-moving tailplane, giving extra control to counteract the Mach tuck which allowed control to be maintained to and beyond supersonic speeds. This was wind-tunnel tested at Mach 0.86 in 1944 in the UK.^[12] In the immediate postwar era new data from captured German records suggested that major savings in drag could be had through a variety of means such as swept wings, and Director of Scientific Research, Sir Ben Lockspeiser, decided to cancel the project in light of this new information. Later experimentation with the Miles M.52 design proved that the aircraft would indeed have broken the sound barrier, with an unpiloted 3/10 scale replica of the M.52 achieving Mach 1.5 in October 1948.^[13] By that time, the sound barrier had been broken by the Americans, and also by the British De Havilland DH 108.

Sound barrier officially broken[link]

U.S. efforts progressed apace soon after Britain had disclosed all its research and designs to the U.S. government on the promise that U.S. information would be shared the other way - a promise that the Americans did not keep.^[14] They utilized the information to initiate work on the Bell XS-1. The final version of the Bell XS-1 has many design similarities to the original Miles M.52 version. Also featuring the all-moving tail, the XS-1 was later known as the X-1. It was in the X-1 that Chuck Yeager was credited with being the first man to break the sound barrier in level flight on 14 October 1947, flying at an altitude of 45,000 ft (13.7 km). George Welch made a plausible but officially unverified claim to have broken the sound barrier on 1 October 1947, while flying an XP-86 Sabre. He also claimed to have repeated his supersonic flight on 14 October 1947, 30 minutes before Yeager broke the sound barrier in the Bell X-1. Although evidence from witnesses and instruments strongly imply that Welch achieved supersonic speed, the flights were not properly monitored and are not officially recognized. The XP-86 officially achieved supersonic speed on 26 April 1948.^[15]

On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first manned supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062, which he had christened Glamorous Glennis. The rocket-powered aircraft was launched from the bomb bay of a specially modified B-29 and glided to a landing on a runway. XS-1 flight number 50 is the first one where the X-1 recorded supersonic flight, at Mach 1.06 (361 m/s, 1,299 km/h, 807.2 mph) peak speed; however, Yeager and many other personnel believe Flight #49 (also with Yeager piloting), which reached a top recorded speed of Mach 0.997 (339 m/s, 1,221 km/h), may have, in fact, exceeded Mach 1.^{[citation needed]} (The measurements were not accurate to three significant figures and no sonic boom was recorded for that flight.)

As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1948 Collier Trophy to be shared by the three main participants in the program. Honored at the White House by President Harry S. Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the NACA contributions.

Jackie Cochran was the first woman to break the sound barrier on May 18, 1953, in a Canadair Sabre, with Yeager as her wingman.

The sound barrier fades[link]

Chuck Yeager broke the sound barrier on October 14, 1947 in the Bell X-1, as shown in this newsreel.

As the science of high-speed flight became more widely understood, a number of changes led to the eventual disappearance of the "sound barrier". Among these were the introduction of swept wings, the area rule, and engines of ever-increasing performance. By the 1950s many combat aircraft could routinely break the sound barrier in level flight, although they often suffered from control problems when doing so, such as Mach tuck. Modern aircraft can transit the "barrier" without it even being noticeable.^{[citation needed]}

By the late 1950s the issue was so well understood that many companies started investing in the development of supersonic airliners, or SSTs, believing that to be the next "natural" step in airliner evolution. History has proven this not to be the case, at least yet, but Concorde and the Tupolev Tu-144 both entered service in the 1970s regardless.

Although Concorde and the Tu-144 were the first aircraft to carry commercial passengers at supersonic speeds, they were not the first or only commercial airliners to break the sound barrier. On 21 August 1961, a Douglas DC-8 broke the sound barrier at Mach 1.012 or 1,240 km/h (776.2 mph) while in a controlled dive through 41,088 feet (12,510 m). The purpose of the flight was to collect data on a new leading-edge design for the wing.^[16] A China Airlines 747 may have broken the sound barrier in an unplanned descent from 41,000 ft (12,500 m) to 9,500 ft (2,900 m) after an in-flight upset on 19 February 1985. It also reached over 5g.^[17]

Breaking the sound barrier in a land vehicle[link]

On 12 January 1948, a Northrop unmanned rocket sled became the first land vehicle to break the sound barrier. At a military test facility at Muroc Air Force Base (now Edwards AFB), California, it reached a peak speed of 1,019 mph (1,640 km/h) before jumping the rails. ^[18][19]

On 15 October 1997, in a vehicle designed and built by a team led by Richard Noble, British driver (and Royal Air Force pilot) Andy Green became the first person to break the sound barrier in a land vehicle in compliance with Fédération Internationale de l'Automobile rules. The vehicle, called the ThrustSSC ("Super Sonic Car"), captured the record exactly 50 years and one day after Yeager's flight.

References[link]

Notes

Citations

Bibliography

External links[link]

Wikimedia Commons has media related to: Sound barrier

• Fluid Mechanics, a collection of tutorials by Dr. Mark S. Cramer, Ph.D
• Breaking the Sound Barrier with an Aircraft by Carl Rod Nave, Ph.D
• a video of a Concorde reaching Mach 1 at intersection TESGO taken from below
• An interactive Java applet, illustrating the sound barrier.
• F-18 breaks the sound barrier

Katy B
Katy B performing in 2011
Background information
Birth name	Kathleen Anne Brien[1]
Also known as	Baby Katy
Born	8 May 1989 (1989-05-08) (age 23) Peckham, South London
Genres	R&B, house, garage, dubstep, UK funky
Occupations	Singer-songwriter
Instruments	Vocals
Years active	2009-present
Labels	Columbia[2]
Website	katyonamission.com

Kathleen Anne "Katy" Brien^[1][3] (born 8 May 1989 in Peckham, South London^[4]), better known as Katy B, is an English singer-songwriter and a graduate of the BRIT School.^[5] She is a dubstep, R&B, funky, house and UK garage singer^[5] and has also performed under the name Baby Katy.^[6] She released her first single with the label Rinse in 2010. The same year, she completed a degree in Popular Music at Goldsmiths, University of London. She was nominated for the 2011 Mercury Prize.^[7]

Life and career[link]

Katy was born in Peckham, South London in 1989, and attended Lyndhurst Primary school, Haberdashers' Aske's Hatcham College^{[citation needed]} and the BRIT School.

Katy featured on many tracks before and during the release of her album, DJ NG's song "Tell Me", on which she featured as Baby Katy,^[6] was released on a white label and later signed to Ministry of Sound.^[8][9] Katy B has collaborated with Geeneus to cover the Kevin Saunderson produced "Good Life"^[10] and the track "As I".^[11] She also provides vocals on the track "Hold Me" for The Count & Sinden's debut album Mega Mega Mega^[12] and features on Magnetic Man's tracks "Perfect Stranger" and "Crossover".^[13]

Geeneus, with whom Katy B collaborated, works for Rinse FM.^[14] Following the official recognition of the station in June 2010 (formerly a pirate radio station),^[15] Rinse presented Katy B's first single, "Katy on a Mission", which was produced by Benga and was released on 22 August 2010.^[16][17] The single reached number 5 on the UK Singles Chart and number 1 on the UK Indie Chart. Katy B performed at the London Jazz Festival in 2009 with Ms Dynamite,^[18] who also featured on Katy's second single, "Lights On" which was released in the UK on 19 December 2010, where it debuted at number 4 on the UK Singles Chart. Her third single "Broken Record" was released in March 2011, and peaked at number 8 in the UK. The fourth single "Easy Please Me" was released on 3 June 2011. Her fifth single "Witches' Brew" was released on 28 August 2011. Katy's debut album On a Mission was released on 4 April 2011, and peaked at number 2 on the UK Albums Chart.

Katy B supported Tinie Tempah on his tour during Spring of 2011. On 30 April 2011, Katy embarked on her debut concert tour throughout Europe until September, then the UK in October.^[19] In September 2011, it was announced Katy B and Mark Ronson would be teaming up to create an advert for the Coca-Cola and the 2012 Summer Olympics. A promo for the song was released on 15 February 2012. A leaked unfinished version of the track for the Coca-Cola advert was also released the same day.^{[citation needed][clarification needed]}

Discography[link]

Studio albums

• 2011: On a Mission

Tours[link]

• Lights On Tour

Awards and nominations[link]

Katy B has received two nominations at both the BT Digital Music Awards and the MOBO Awards. She was nominated for Best Push Act at the MTV Europe Music Awards 2011. She has received six nominations at the Virgin Media Music Awards and one nomination for the ITunes Rewind 2011.