The Athenaeum was a literary magazine established in 1798 by August Wilhelm and Karl Wilhelm Friedrich Schlegel. It is considered to be the founding publication of German Romanticism. Only three volumes were published, in 1798, 1799, and 1800.

Contributors
 Karl Wilhelm Friedrich Schlegel
 August Wilhelm Schlegel
 Dorothea von Schlegel
 Karoline Schelling (then Schlegel)
 Novalis
 August Ferdinand Bernhardi
 Gustav Adolf Bergenroth
 Sophie Bernhardi
 Friedrich Daniel Ernst Schleiermacher
 August Ludwig Hülsen
 Carl Gustaf von Brinkman.

Contents
The following is a partial listing of articles in Athenaeum taken from Lacoue-Labarthe and Nancy's The Literary Absolute.

1798
Volume 1 (1):  Notice (Friedrich and August Schlegel), Languages:  A Dialogue on Klopstock's Grammatical Dialogues (August Schlegel), Grains of Pollen (Novalis), Elegies translated from the Greek (Friedrich and August Schlegel), Contributions to the Most Recent Criticism of Literature (A.W. Schlegel)

Volume 1 (2):  Fragments, On Goethe's Meister Wilhelm (Friedrich Schlegel)

1799
Volume 2 (1):  On Philosophy.  To Dorothea (Friedrich Schlegel), The Paintings.  A Dialogue (A.W. Schlegel with Caroline Schlegel), On the Natural Equality of Man (A.L. Hülsen)

Volume 2 (2):  The Art of the Greeks.  To Goethe.  An Elegy (A. W. Schlegel), On Drawings Based on Poems, and on the Silhouettes of John Flaxmann (A. W. Schlegel), The Eleventh Song of "Orlando Furioso" (A.W. Schlegel), Postscript of the Translator to Ludwig Tieck (A.W. Schlegel), Notes (A. W. Schlegel), Discourses on Religion (Friedrich Schlegel, review), Anthropology by Emmanuel Kant (F.D.E. Schleiermacher, review), Notes (K.G. Brinckmann), The Literary Indicator of the Empire, or Archives of the Epoch and its Taste (August Schlegel)

1800
Volume 3 (1):  To Heliodora (Friedrich Schlegel), Ideas (Friedrich Schlegel), Considerations of Nature during a Voyage in Sweden (A.L. Hulsen), Dialogue on Poetry I (Friedrich Schlegel), The Last Writings Published by Garve (F.D.E. Schleiermacher, review), (various reviews by August Schlegel), List of Reviews Published by A. W. Schlegel in the Universal Journal of Literature

Volume 3 (2):  To the Germans (Friedrich Schlegel), Dialogue on Poetry II (Friedrich Schlegel), Hymns to the Night (Novalis), Conception of Life (Sophie Bernhardi), Idylls translated from the Greek (August and Friedrich Schlegel), To Ludwig Tieck (August Schlegel, sonnet), Discourses on Religion --- The Soul of the World of Schelling (sonnets), The Athaneum --- Zebrino (Friedrich Schlegel, sonnet), The Moral Stories of Ramdohr (Dorothea Schlegel), (various reviews by August Schlegel, Schleiermacher, Bernhardi), On Incomprehensibility (Fridrich Schlegel)

References

External links
 Athenaeum, 1798 (German language)
 Caroline Schlegel and her friends, Chapter VII, By Mrs. Alfred Sidgwick, T. F. Unwin, 1889
 Lacoue-Labarthe, Philipe and Jean-Luc Nancy. The Literary Absolute. Albany: SUNY Press, 1978.

Defunct literary magazines published in Germany
German-language magazines
Magazines established in 1798
Magazines disestablished in 1800
Romanticism

Athenaeum (German magazine)


A tutor is a person who teaches or guides another person. Usually, the tutor is an older expert who teaches a younger learner. Early examples were Socrates, who taught philosophy by holding conversations with his students, and Aristotle, who was appointed the personal tutor of Alexander the Great when the latter was a youth.

The essence of a tutor's work is to adjust the teaching to the individual learner. The tutor has to take account of:
what the learner already knows and does not know
what the learner has incorrectly learnt
the personal interests and goals of the learner
the particular talents of the learner

The idea is that a tutor teaches, or 'moulds' the student as a whole. However, there is an obvious difference between the tutor's need for topical knowledge and his or her need for 'people skills'. The system operated at the older colleges of Oxford University recognises this by appointing two tutors to a student: a subject-matter tutor and a moral tutor. The latter helps the student with problems of a personal nature.

Education by a tutor is often thought to be an ideal kind of education, because the tutor can adjust the learning to suit one student. However, the word is often misused. If students are taught in groups larger than three or four, then much that makes a tutorial special is lacking.

Special cases
High achievers in fields like  music, mathematics and chess may be tutored when classroom methods do not meet their needs.

There are parallels in other walks of life. Sports people have coaches, and the job of a coach is very similar to that of a tutor. A guru might be regarded as a kind of tutor. A mentor is a kind of tutor. Parents with children do much that a tutor does.

Tutoring in mainstream education

Universities
In Australian, New Zealand, and some Canadian universities, a tutor is often but not always a postgraduate student or a lecturer who conducts a seminar for undergraduate students. These seminars are often known as a tutorial.

In the United States and the rest of Canada, a tutor is known as a teaching assistant.

Historically, the term "tutor" has assumed a simple relationship between an expert older person and a young learner. With the huge classes of a modern university the one-to-one relationship between tutor and learner is all but dead and buried. The tutor sets MCQs (multiple choice questions) and the mass of students learn a set text by rote learning. The tests are easy to mark, and the marking is done by a graduate student who gets paid for the work.

Secondary school form tutors
In English and Irish secondary schools, form tutors are similar to American home room teachers. They are in charge of a group of students in a particular year group.

Peer tutoring
In the United States, peer tutors are students teaching other students of the same or similar age or grade level. When peer tutors are trained how to tutor correctly, peer tutoring is both cost effective and academically effective.

Related pages
Learning by teaching

References

Other websites
National Tutoring Association A U.S. professional trade association dedicated exclusively to tutoring.

Learning

Tutor


Scouting in Kansas has a long history, from the 1910s to the present day, serving thousands of youth in programs that suit the environment in which they live.

Early history (1910−1950)

The Brewer Scout Cabin in Solomon is on the National Register of Historic Places.

Mrs. Fern E. Sears was the organizer of the first Kansas City, Kansas council of Girl Scouts and author of a book on Christian symbols, "Let Me Speak".  She trained Girl Scout leaders and established troops in Kansas City, Kansas in 1948 when the area qualified for a council, called the Santa Fe Trail council.  Mrs. Sears was named first president, and was an honorary life president at the time of her death on August 24, 1959.

Recent history (1950−present)
In 1958 the National Order of the Arrow Conference was held at the University of Kansas.

In the 1990s and 2000s, BTK killer, also known as Dennis Rader, was a part of the Cub Scouts. He was a leader.

Scouting in Kansas today
There are seven Boy Scouts of America (BSA) local councils in Kansas.

Coronado Area Council

Coronado Area Council serves north central and northwest Kansas, across 32 counties, with headquarters in Salina.

Heart of America Council

Heart of America Council serves Scouts in Missouri and Kansas.

Jayhawk Area Council

In 1928 the Topeka Council took over 39 counties across northern Kansas and became the Jayhawk Area Council.

Buffalo District
Pony Express District
Shunga District
Sojadi District
Sunflower District

Camps
The Jayhawk Area Council operates the 340 acre Falley Scout Reservation, which is divided into Camp Jayhawk (Scouts BSA Summer Camp) and Camp Delaware (Cub Scout Programs).

Ozark Trails Council

Ozark Trails Council serves Scouts in Missouri and Kansas.

Pony Express Council

The Pony Express Council is based in Saint Joseph, Missouri, and also serves Scouts in Kansas.

Quivira Council

Quivira Council serves youth in south central Kansas, with headquarters in Wichita. Kansa Lodge #198, Order of the Arrow serves local Arrowmen. They currently operate two camps: Camp Kanza (Cub Scouts and Webelos), which provides the name for their Lodge; and Quivira Scout Ranch (Scouts BSA and Venturers), at which they host their largest summer camp program each summer, and offer Black Jack Trail, an introduction to backpacking, twice a year.

High Plains District
Kanza District
Osage Nation District
Pawnee District
South Winds District
White Buffalo District

The Quivira Council website http://www.quivira.org/ has links to each district.

Santa Fe Trail Council
Santa Fe Trail Council includes nineteen counties in southwestern Kansas, with headquarters in Garden City.

Spanish Peaks Scout Ranch

The Spanish Peaks Scout Ranch (SPSR) is located near Walsenburg, Colorado and borders the Spanish Peaks Wilderness. It is a local council camp of the Santa Fe Trail Council based out of Garden City. The camp gives program geared toward outdoor education such as wilderness backpacking, climbing, and outdoor skills.

Spanish Peaks Staff Association

Spanish Peaks Staff Association (SPSA) is a non-profit organization dedicated to connecting current, former, and honorary staffers of Spanish Peaks Scout Ranch (SPSR). The organization was formed by like-minded staff alumni committed to the continued support of SPSR and the love of outdoor education for youth.  Although the Spanish Peaks Staff Association is not an alumni association the members have all worked with this Scout camp and are dedicated toward outdoor education for youth.

Purpose

The Spanish Peaks Staff Association, although still in their infant stages, has adapted the purposes of:

(a) Demonstrating support for Spanish Peaks Scout Ranch and its continued value in the future.
(b) Providing vision and leadership for Spanish Peaks Scout Ranch.
(c) Raising volunteer and financial support for Spanish Peaks Scout Ranch improvement endeavors.
(d) Establishing an endowment that will guarantee the future stability of the SPSR independently of Santa Fe Trail Council operations.
(e) Establishing an endowment that insures continued funding of a full-time ranger at Spanish Peaks Scout Ranch.
(f) Providing a forum for past, present, and future staffers to gather, share ideas, and stay in contact.

Structure
The Spanish Peaks Staff Association (SPSA) is independent of the Santa Fe Trail Council and Spanish Peaks Scout Ranch. They are, however, dedicated to the youth of southwest Kansas and promotion of outdoor education. The organization was chartered in 2006 as a response to a struggling economy and the Santa Fe Trail Council's Board deficit. The lack of the council's ability to secure funds for operating expenses led to SPSA's motivation and primary goal of securing funds separate of the council.

Buffalo Range District
Cimarron District
High Plains District

Girl Scouting in Kansas

There are three Girl Scout councils in Kansas.

Girl Scouts of Kansas Heartland

The Girl Scouts of Kansas Heartland serves more than 16,000 girls and nearly 5,000 adult volunteers in 80 counties in Kansas.

It was formed by the merger of six councils in 2008:
Girl Scouts of Central Kansas,
Girl Scout Council of The Flint Hills,
Girl Scouts of Sunflower Council,
Girl Scouts Wheatbelt Council,
Girl Scouts of Tumbleweed Council, and
Girl Scouts of The Golden Plains Council

Headquarters: Wichita, Kansas

Website: http://www.girlscoutskansasheartland.org

Camps:
Starwoods Outdoor Center is  in Clearwater, Kansas
Camp Four Winds near Leon, Kansas.  It has a  lake.
Camp Double E is  northwest of Emporia, Kansas

Girl Scouts Missouri Heartland

Girl Scouts of Missouri Heartland is mostly based in Missouri but serves girls in southeastern Kansas (Bourbon, Cherokee, and Crawford counties) and northeastern Oklahoma.  See Scouting in Missouri for more information.

Headquarters: Springfield, Missouri

Website: http://www.girlscoutsrscmo.org

One of its camps is located in Kansas:
Camp Friendship Fields in Crawford County

Girl Scouts of Northeast Kansas and Northwest Missouri

Girl Scouts of Northeast Kansas and Northwest Missouri supports girls in many Kansas counties: Atchison, Anderson, Brown, Clay, Doniphan, Douglas, Geary, Franklin, Jackson, Jefferson, Johnson, Leavenworth, Linn, Marshall, Miami, Nemaha, Pottawatomie, Riley, Shawnee, Wabaunsee, Washington and Wyandotte.

It was established on August 1, 2007, with a merger of several other councils including Girl Scouts of Kaw Valley Council headquartered in Kansas.

See Scouting in Missouri for full information.

Headquarters: Kansas City, Missouri

Website: http://www.girlscoutsksmo.org

Camps in Kansas include:
Camp Daisy Hindman, founded in 1929, is  in Dover, Kansas near Topeka
Camp Cutteru is near Junction City, Kansas
Camp Timberlake was  near Stilwell, Kansas, but was sold to private owners in the mid-2010s.  It is still used as a scouting camp by reservation with the new owners.
Tongawood Program center is  near Tonganoxie, Kansas

Scouting museums in Kansas
Central States Scout Museum, Larned, Kansas

See also

Roy Williams (Scouting)
Tribe of Mic-O-Say

References

External links

 Spanish Peaks Staff Association
 Spanish Peaks Scout Ranch
 Coronado Area Council
 Jayhawk Area Council
 Quivira Council
 Santa Fe Trail Council

Youth organizations based in Kansas
Kansas
Central Region (Boy Scouts of America)

Scouting in Kansas


Bright's disease is a historical classification of kidney diseases that are now called acute or chronic nephritis. The main symptom is  the presence of serum albumin (blood plasma protein) in the urine, and frequently accompanied by oedema and hypertension.

The term is no longer used, as the disease is now classified by its better known causes.

References

Diseases

Bright's disease


John Philip Falter (February 28, 1910 – May 20, 1982) was an American artist best known for his many cover paintings for The Saturday Evening Post.

Early life
Born in Plattsmouth, Nebraska, Falter moved at an early age with his family to Falls City in 1916, where his father, George H. Falter, established a clothing store. As a high school student, Falter created a comic strip, Down Thru the Ages, which was published in the Falls City Journal. J. N. "Ding" Darling, Pulitzer Prize-winning cartoonist of the Des Moines Register, saw some of Falter's cartoons and said he should become an illustrator.

Pulp dreams
After graduating from high school in 1928, Falter studied at the Kansas City Art Institute where he met and became friends with R. G. Harris, Emery Clarke, and Richard E. Lyon. He won a scholarship to the Art Students League of New York City, but lasted only one month there due to his fear of his fellow students, many of whom were avowed Communists.  This was all too new for the small-town Falter, who fled and immediately looked for work as an illustrator.  In the evenings, he took courses at the Grand Central School of Art above Grand Central Terminal. At this time in the Great Depression, when most young artists had difficulty finding work, Falter began illustrating covers for pulp magazines.

He opened a studio in New Rochelle, New York, which had long been a colony for illustrators, including such artists as Frederic Remington and Norman Rockwell. Within a few years, his three Kansas City Art Institute friends Harris, Clarke and Lyon had moved to New Rochelle to share a studio with Falter and launch their careers as freelance illustrators. Falter recalled, "Rockwell was our inspiration then. I didn't meet him until years later. We would hear that Rockwell had been out on the street. and we'd all rush out and hunt for him. If they'd tell us that he had looked in a shop window, we'd look in the same window trying to absorb what he looked at by osmosis."

Ad art

Falter received a major break with his first commission from Liberty Magazine to do three illustrations a week in 1933. "They paid me $75 a week," Falter said, "just like a steelworker. But my expenses for models and costumes were running $35 a week during one 16-week serial I was illustrating." Falter soon discovered that there was much more money to be made in advertising than in other fields of illustration. By 1938, he had acquired several advertising clients including Gulf Oil, Four Roses Whiskey, Arrow Shirts and Pall Mall. Falter's work appeared in major national magazines. "This was high pay for less work," Falter said, "and it gave me a chance to experiment in the field of easel painting."

World War II
In 1943, he enlisted in the Navy and was rapidly promoted from chief boatswain's mate to lieutenant on special assignment as an artist. His final rank was Chief Petty Officer. His talents were applied to the American war effort to spur on recruiting drives. Falter designed over 300 recruiting posters. One popular Falter poster dealt with the loose-lips-sink-ships theme. It showed a broad-shouldered Navy man with the caption, "If you tell where he's going, he may never get there." During this period, he also completed a series of recruiting posters for the women's Navy (WAVES), and a series of 12 Medal of Honor winners for Esquire.

The Saturday Evening Post
Falter's first Saturday Evening Post cover, a portrait of the magazine's founder, Benjamin Franklin, is dated January 10, 1943. It began a 25-year relationship with the magazine, for whom Falter produced over 120 covers until the editors changed its cover format to photographs. Falter commented, "There were plenty of Rockwell imitators and J. C. Leyendecker imitators. My main concern in doing Post covers was trying to do something based on my own experiences. I found my niche as a painter of Americana with an accent of the Middle West. I brought out some of the homeliness and humor of Middle Western town life and home life. I used humor whenever possible." Nearly all of Falter's 120-odd covers were his own ideas. "Four didn't make it, [and] probably 12 ideas were supplied by the Post," he said.  Many of his friends acted as models for his covers; four of them depict his close friend, the actor J. Scott Smart.

Falter said that he tried "to put down on canvas a piece of America, a stage set, a framework for the imagination to travel around in." His panoramic covers with long views of people were a major departure from the Post's customary close-up designs. Norman Rockwell himself adjusted to the newer style for a time, which he later referred to as his "Falter Period."

Falter once thought that The Saturday Evening Post would provide him with lifetime employment. "I was sort of going along on a ship that would never sink," he said. "It seemed that nothing could possibly happen to the Post. Then suddenly, in my middle life, I had to retool and give up my horse for a car." Falter was forced to spend much of his savings in the months that followed the demise of the Post.

Portraits and book covers

Although best known for his Saturday Evening Post covers, of which he produced 129, Falter also provided illustrations for numerous other publications, including Esquire, Good Housekeeping, Cosmopolitan, McCall's, Life Magazine and Look.

Falter was a prolific artist who depicted a wide range of subject matter in a variety of media. As television eliminated many national magazines in the 1950s and 1960s, he turned to portrait painting and book illustration. He illustrated over 40 books. One of his favorite projects was illustrating a special edition of Carl Sandburg's Abraham Lincoln—The Prairie Years. Other favorite book projects included Houghton-Mifflin's Mark Twain series and illustrations for The Scarlet Pimpernel. His stepson, Jay Wiley, posed for a book Falter illustrated, Me 'n Steve. A final favorite was humorist Corey Ford's The Horse of a  Different Color.

Falter produced a body of work impressive in volume and variety. Reflecting a lifelong interest in jazz, he did scenes of Harlem nightclub life in the 1930s, and later, portraits of famous jazz musicians. An excellent portrait painter, Falter had Clark Gable, James Cagney, Olivia de Havilland and Admiral "Bull" Halsey among his sitters. He was an accomplished jazz clarinet player, entirely self-taught. He took great pleasure in visiting jazz friends at clubs such as Eddie Condon's in New York City, where he would sketch the musicians live, then sit in on clarinet.

1970s and 1980s
As the age of illustrated magazines ended during the 1970s and 1980s, Falter turned to his passions for historical and American Western themes. The 3M Company commissioned him for a series of six paintings in celebration of the American Bicentennial, titled From Sea to Shining Sea. Falter completed over 200 paintings in the field of Western art, with emphasis on the migration of 1843 to 1880 from the Missouri River to the Rocky Mountains. His peers honored him with election to the Illustrators Hall of Fame] in 1976, and membership in the National Academy of Western Art in June 1978.

When Falter was asked to look back over his career, he commented that he had never created a painting that he wouldn't like to do over; he always saw something he thought he could improve on. His output was prodigious, and by his own reckoning included over 5,000 paintings, many of which hang in museums and eminent collections.

In 1980, a documentary video, "A View from the Standpipe: John Falter's World," was released by Nebraska Educational Television. It features one-on-one interviews with people who knew the artist in his Philadelphia location, and shows a number of his paintings, including some of Falter's personal paintings not often seen by the general public. These paintings are different from his usual subjects, and often contain humorous touches not obvious on first viewing. One example, "The Big Spender," is a beautiful Vermeer-like still life of a dinner plate, crystal glass and linen napkin, where a huge fly is just visible as it heads for the plate.

Death and legacy
John Falter died in May, 1982, at the age of 72, at the University of Pennsylvania Hospital in Philadelphia after suffering a stroke. He was living in the Chestnut Hill section of Philadelphia.  After his death, Falter's widow, Mary Elizabeth Falter, donated several paintings, personal papers, and memorabilia from his studio to the Nebraska State Historical Society. The material reflects Falter's career from 1930 to 1982.

Falter's daughter, author Suzanne Falter, maintains a web-based business coaching others to fulfill their creative dreams. His stepson, Jay Wiley, is a freelance photographer specializing in restaurant and hospital photography. His stepdaughters Lisa Waitneight and Sarah Johansen are homemakers.

See also
Museum of Nebraska Art
John Philip Falter Museum

References

External links

Museum of Nebraska Art, Kearney, Nebraska
John Falter Original: Attempted Assassination of Theodore Roosevelt Shapell Manuscript Foundation
John Philip Falter tear sheets in the Charles Craver Collection at the Modern Graphic History Library
The Museum of Nebraska Art

1910 births
1982 deaths
20th-century American painters
American male painters
Artists from Nebraska
Painters from Nebraska
Artists from New Rochelle, New York
Art Students League of New York alumni
Kansas City Art Institute alumni
The Saturday Evening Post people
American magazine illustrators
People from Plattsmouth, Nebraska
People from Falls City, Nebraska
WAVES (Navy)
20th-century American male artists

John Philip Falter


The Calico Early Man Site is an archaeological site in an ancient Pleistocene lake located near Barstow in San Bernardino County in the  central Mojave Desert of Southern California. This site is on and in late middle-Pleistocene fanglomerates (now-cemented alluvial debris flow deposits) known variously as the Calico Hills, the Yermo Hills, or the Yermo formation. Holocene evidence includes petroglyphs and trail segments that are probably related to outcrops of local high-quality siliceous rock (primarily chalcedony in freshwater limestone).

The Calico Early Man Site includes:
 Artifacts of the Lake Manix Lithic Industry (LMLI) found on and just below the surface at elevations greater than , the shoreline elevation of a  freshwater Pleistocene lake which emptied approximately 18,000 years ago.
 Material recovered from nested Pleistocene alluvial deposits stratigraphically beneath a 100,000-year-old soil profile: a 'rock ring' (not a fire hearth) dated to 135,000 years by thermoluminescence (TL), about 200,000 years by uranium-series analysis, and about 197,000+/- 20,000 years by surface beryllium-10 (10Be) dating.
 The Rock Wren Biface, a large well-formed biface tool recovered from a younger nested-inset alluvial deposit at Calico: dated by sediment thermoluminescence (sediment TL) to 14,400 ±2,200 years ago.  A test pit located near the discovery location is currently being excavated and is yielding artifactual material.

The tools and flakes of LMLI and those found in the nested inset known as the Rock Wren Locality were probably made by modern man (Homo sapiens sapiens).

Introduction
The stone tools of these industries, along with preforms, lithic core, technical flakes, and pieces of angular debitage, mainly of chalcedony, are found on and in late middle Pleistocene-age fanglomerates and younger inset alluvial terraces in the Calico Hills (also known as the Yermo Hills) east of the Calico Peaks and the Calico Mountains.  The location is in the central portion of southern California's Mojave Desert. Historically, this archaeological project has also been known as "The Calico Mountains Archaeological Site" and "The Calico Hills Archaeological Site".  Today, it is called "The Calico Early Man Site".

Manix Basin
In most of the Great Basin region, Late Pleistocene and Holocene alluviation has effectively buried and sealed earlier Pleistocene sediments and possible evidence of pre-Clovis cultures. In the Manix Basin (Lower Mojave Valley) of San Bernardino County, California a fortuitous ensemble of environmental factors relating to mountain building, climatically controlled conditions for lake formation, alluviation, and erosion, faulting and folding and significant erosion of ancient lacustrine plain sediments by the modern drainage have rendered relatively accessible for archaeological investigation a series of deposits that represent more than 350,000 years of Quaternary history.

The Manix Basin, a structural basin in the central Mojave Desert, is the third and lowest major valley of the Mojave River, presently an exotic stream with episodic flow, which has its source in the San Bernardino Mountains, some  to the southeast.

A freshwater lake developed in the basin about 400,000 – 500,000 years ago near the Calico Archaeological Site. The lake was present until the late Pleistocene.  The last high stand of Lake Manix was at  and had a surface area of approximately . This lake drained, probably catastrophically, approximately 18,100 years ago, probably as a result of a major increase in river inflow or tectonic movement on the Manix fault.

Fossils
The lacustrine, fluvial, and alluvial sediments of the Pleistocene Manix Formation contain remains of numerous Rancholabrean animals ranging in age from approximately 20,000 years to well in excess of 350,000 years before present. Fossils recovered from the section include: camel, horse, mammoth, saber-tooth cat, dire wolf, short-faced bear, coyote, flamingo, pelican, eagle, swan, geese, mallard duck, ruddy duck, canvas backed duck, double-crested cormorant, grebe, crane, seagull and stork.

Prehistoric tools
Thousands of rocks that bear a strong resemblance to prehistoric tools have been found at the site, both on the surface, and up to  below the surface. A stone from the Master Pit had been dated to over 200,000 BP. This date could have been the result of contamination from other elements in the soil, so currently there is an effort to date verified lithics through thermoluminescence dating. While the results are still pending, the styles suggest 20,000 to 30,000 BP.

The debate centers on whether the "tools" were made by humans (i.e., artifacts), or through typical geological processes (i.e. geofacts). The general scientific consensus is that the subsurface items are geofacts.

Artifacts or geofacts?
The artifactual character of the Calico lithic assemblage has been questioned (Haynes 1973; Payen 1982a, 1982b; Taylor and Payen 1979; Duvall and Venner 1979).  Haynes (1973) postulated that rock fracturing by tectonic stresses, weather, rock-on-rock percussion in streams and mudflows, pressure retouch of buried cobbles, and successive generations of flake removal and separation from cores through cycles of erosion and redeposition could have occurred during deposition of the alluvial deposits at Calico and produced specimens indistinguishable from artifacts.

Specimens collected from earlier excavations up to the present are under analysis by archaeologists volunteering at the Calico site. Many have been confirmed to be geofacts, but some are believed to be potential artifacts and have been cataloged and submitted for thermoluminescent dating. Currently work is being done on compiling and publishing the most recent finds at the site to be submitted to the local tribes, community and journals for peer review.

Flake scar angles
Payen (1982) studied flake scar angles as traits for distinguishing artifacts from geofacts.  He tested a method developed by Barnes (1939) who had compared frequency of obtuse angles on eoliths, natural fractures, and artifacts.  Barnes found obtuse angles on 72% of eoliths, 75% of natural fractures, and 18% of artifacts and concluded that "The flaked tools of an industry…may be considered to be of human origin if not more than 25% of the angles scar-platform are obtuse (90° and over)" (Barnes 1939:111).  Payen measured all flake angles on each Calico specimen in his sample.  It is conceivable that flake scars were confused for striking platforms.  Flaking from one side of a specimen can often remove earlier platform areas on the other side.  Angles between two flake scars are different from angles between platforms and derivative flake scars.

Payen compared mean angle values for Calico specimens with those on specimens selected as representing controlled and uncontrolled fracture.  He found that "Statistically, there is no significant difference between the sample of alleged tools and the uncontrolled fracture series."  (Payen 1982:200).

Duvall and Venner (1979:462) examined a sample of Calico artifacts and concluded they were form-selected examples of naturally flaked rocks.  Their assessment was based on variances in seven attributes (length, width, thickness, flake angle, medial axis angle, lateral edge angle, and distal edge angle) and comparison with comparable attributes on specimens in eight Paleoindian collections reported by Wilmsen (1970).

Current consensus
Both the Duvall/Venner and the Payen papers have been criticized on a number of levels, and analyses supporting the pro-artifact argument have been published. The present consensus is that there is no evidence of human activity at the Calico Early Man site. This consensus developed based on a number of factors, including:

The lack of other evidence of human activity (e.g. human or animal remains, or non-tool artifacts).
The deep antiquity of the site (the next oldest date for human artifacts in the Americas is 30,000 BP, and that date itself is controversial).
The sheer number of possible tools, up to 60,000 by one account.
The research by Duvall/Venner, Payen, and others providing possible natural explanations for the stone objects.

History of excavations

In 1959 Louis Leakey, while at the British Museum of Natural History in London, received a visit from Ruth DeEtte Simpson, an archaeologist from California. Simpson had acquired what looked like ancient scrapers from a site in the Calico Hills and showed it to Leakey.

Leakey viewed it as important to study the Calico Hills site, as he was convinced that the number and distribution of native languages in the Americas required more time than 12,000 years to evolve and acquire their current distribution. In 1963, Leakey obtained funds from the National Geographic Society and commenced archaeological excavations with Simpson. Excavations in an area stratigraphically separate from a verified 10,000-year-old Paleoindian site were carried out by Leakey and Simpson, who believed that they had located stone artifacts that were dated 100,000 years or older, suggesting a human presence in North America much earlier than estimated.  George F. Carter discusses this work and its background and context at length in Older Than You Think.

The archaeologist Jeffrey Goodman who worked at the site with Leakey had also claimed the stone artifacts to be human made. Goodman has also made controversial statements that the artifacts found at Calico Hills may be as old as 500,000 years and if proven would be the oldest human artifacts in the world, which would place human origins in the Americas. However, the majority of scientists have rejected these claims. According to Kenneth Feder, "Goodman's claims were not backed up with even a shred of evidence."

The geologist Vance Haynes had made three visits to the site in 1973 and had claimed that the artifacts of Leakey were naturally formed geofacts. According to Haynes, the geofacts were formed by stones becoming fractured in an ancient river on the site.

In her autobiography, Louis' wife Mary Leakey wrote that because of his involvement with the Calico Hills site she had lost academic respect for him, and that the Calico excavations was "catastrophic to his professional career and was largely responsible for the parting of our ways". She did not share his visionary views about the Calico site. She regarded Louis as often slipping into incompetence and often publicized that opinion. Louis Leakey continued to visit the site several times a year and was connected with the project until his death in 1972. The site was taken over by the Bureau of Land Management and was opened to the public.

See also

 Archaeology of the Americas
 Arlington Springs Man - (Human remains)
 Buhl woman - (Human remains)
 Calico Ghost Town
 Cerutti Mastodon site
 Cueva de las Manos  - (Cave paintings)
 Fort Rock Cave - (Archeological site)
 Kennewick Man - (Human remains)
 Kwäday Dän Ts'ìnchi - (Human remains)
 Marmes Rockshelter - (Archeological site)
 Paisley Caves  - (Archeological site)

References

Sources and further reading
 Bischoff, J.L., R.J. Shlemon, T.L. Ku, R.D. Simpson, R.J. Rosenbauer, & F.E. Budinger, Jr., "1981 Uranium-series and Soils-geomorphic Dating of the Calico Archaeological Site, California", Geology V9 (12), pp. 576–582.
 Budinger Jr., Fred E., Oberlander, Theodore Calicodig.org "This web site describes and analyzes the Calico Archaeological Site and the Calico Lithic Industry". With many stone object photos.
 Carter, George F., Older Than You Think, College Station, Texas, Texas A&M University Press, 1980.
 Debenham, N., (1998) Thermoluminescence Dating of Sediment from the Calico Site (California) (CAL1), Quaternary TL Surveys, Nottingham, United Kingdom, 1998.
 Duvall, James G., and Venner, William Thomas, "A Statistical Analysis of the Lithics from the Calico Site (SBCM 1500A), California", Journal of Field Archaeology, Winter 1979: Vol. 6, No. 4, pp. 455–462.
Haynes, Vance (1973) "The Calico Site: Artifacts or Geofacts?", Science, vol. 181, no. 4097, July 27, 1973, pp. 305–310.
Morell, Virginia (1995) Ancestral Passions: The Leakey Family and the Quest for Humankind's Beginnings, Simon & Schuster, pp. 266–267.
 Payen, L., "Artifacts or geofacts at Calico: Application of the Barnes test," in Peopling of the New World, Ericson J., Taylor, R., and Berger, R., eds. Los Altos, California: Ballena Press, 1982, pp. 193–201.
Patterson, Leland W.; Hoffman, Louis V.; Higginbotham, Rose Marie; Simpson, Ruth D. (1987) "Analysis of Lithic Flakes at the Calico Site, California", in Journal of Field Archaeology, Vol. 14, No. 1 (Spring, 1987), pp. 91–106.
 AmericanWest's North American Archaeology Section, Calico Site Update. ". . .over 60,000 tools and flakes have been collected".
Friends of Calico Early Man Site; 2024 Orange Tree Lane, Redlands, CA 93474. (accessed 6/2010)
Calico Mountains Archaeological Site. (2015). ""...Current Consensus.

External links
Calico Mountains Archaeological Site from the Friends of Calico

Archaeological museums in California
Archaeological sites in California
Archaeological sites on the National Register of Historic Places in California
Bureau of Land Management areas in California
Historic districts on the National Register of Historic Places in California
History of San Bernardino County, California
History of the Mojave Desert region
Museums in San Bernardino County, California
National Register of Historic Places in San Bernardino County, California
Native American history of California
Paleo-Indian archaeological sites in the United States
Pre-Clovis archaeological sites in the Americas
Pre-Columbian cultures
Pre-statehood history of California
Protected areas of the Mojave Desert
Protected areas of San Bernardino County, California
Stone age sites

Calico Early Man Site


Spoonface Steinberg is a play by British playwright Lee Hall, first broadcast as a dramatic monologue on BBC Radio 4 on Monday 27 January 1997. Such was the popular acclaim that the BBC repeated it on Radio 4 the following Saturday afternoon.

It began life as the fourth and final play in the God's Country series of linked radio dramas broadcast in 1997 on BBC Radio 4. However, due to its success  (it went on to sell thousands of copies on cassette) it has come to overshadow the other plays in the sequence somewhat, and is commonly thought of as a standalone piece.

Spoken by a 7 year old autistic girl who is dying from cancer, the original recording was performed by Becky Simpson who won two awards for her performance  The play was subsequently published as part of the anthology Spoonface Steinberg and Other Plays in October 1997.

On 30 March 1998 the play was rebroadcast, this time on BBC TV and with images (including that of Ella Jones as Spoonface) added to the original.

A stage version, adapted by Hall himself as well the play's directors Marcello Magni and Annie Castledine, was first performed in 2000. The play featured Kathryn Hunter, at the time 42 years of age, in the title role.

The Scottish professional premiere was produced by Nomad at the Tron Theatre in 2002.  Kirstin McLean played Spoonface and Mark Westbrook directed. The play has also been produced by the Nuffield Theatre Southampton, directed by Russ Tunney, starring Julie Rose Smith as Spoonface. Beggars and Kings' production directed by Michael Fentiman was performed at Theatre Clwyd 26 March 2009, starring Zoe Thorne and toured until 30 April 2009. A production by the Freerange Theatre Company, directed by Hugo Chandor and starring Rebecca Fenwick, toured the north of England and Scotland in 2013, gaining nominations for best production and best actress at the Buxton Festival fringe. together with a nomination for Best Fringe Performance at the Manchester Theatre Awards.

References

External links
Details and reviews of the original theatre staging at Abermarle of London
The TV adaptation at IMDB
Mark Westbrook - The first director of Spoonface in Scotland
Freerange Theatre Company, whose production of Spoonface toured in 2013

British radio dramas
1997 audio plays
British television films
BBC television dramas
Television shows based on plays
Plays by Lee Hall (playwright)
Autism in the arts

Spoonface Steinberg


The Spanish treasure fleet, or West Indies Fleet from Spanish Flota de Indias, was a convoy system adopted by the Spanish Empire from 1566 to 1790. It linked Spain with its territories in America across the Atlantic. The convoys were general purpose cargo fleets used for transporting a wide variety of items. These included agricultural goods, lumber, various metal resources, luxuries, silver, gold, gems, pearls, spices, sugar, tobacco, silk, and other exotic goods from the Spanish Empire. They were sent to the Spanish mainland. Passengers and goods such as textiles, books and tools were transported in the opposite direction. The West Indies fleet was the first permanent transatlantic trade route in history. Similarly, the Manila galleons were the first permanent trade route across the Pacific.

References

16th century in Spain
17th century in Spain
18th century in Spain

Spanish treasure fleet


Sokker Manager is a realistic, browser-based online football manager game (MMOG) with an exclusive 3D match engine and a 2D match engine. The game, developed in Poland, began in early 2004 and currently has 98 FIFA countries which users can register to, and as of February 2012, there were over 52,000 registered users world-wide. Each month, Sokker is voted one of the best sports game on the internet, out of the top 50 sports game.

The game is free to play, however there is an optional "Plus" service which will give users access to additional in-game tools that can help them progress as a manager. As a manager, you are in complete control of a team, where you must select players and use strategic tactics in order to defeat the opponent.

Gameplay
The basic idea of Sokker is to manage your own football team, trying to promote yourself without going financially bankrupt. To do this, you must buy and sell players, optimizing your teams performance while making money to improve the club. You will also have to be able to use the tactical editor to take advantage of your players skills. However, this all depends on the playing style of a user, each have their own. Whether you play to train up players, or to try to beat your friend, you will encounter many economical and tactical barriers that will force you to expand your knowledge as a manager. Sokker is different to many other soccer management games, due to it having a 2D Flash match viewer and as from 2012, a new exclusive 3D Flash Match Viewer. This enables users to watch their managerial skills in action through the comfort of an animated football match.

Players
Each player has 8 main skills, which will define them where they play on the pitch. These are;

Stamina - This skill indicates how long a player can play before becoming fatigued.
Pace - Determines how fast the player is.
Technique - This skill affects the technical ability a player will have, such as skill of controlling a pass, chance of mis-kicking, pace of dribbling, skill of passing a defender. Technique is highly valued in most positions on the field.
Passing - This skill determines the accuracy of player's passes (both kicks and headers). The accuracy means both the right direction and power, so that the team-mate will be able to receive the ball as easily as possible.
Keeper - This skill is only useful for keepers. It determines effectiveness of saves and their quality. The higher the skill, the more often the keepers catch the ball or clears it cleverly (away from the strikers).
Defender - The higher the defending skill, the greater the chance of tackling an opponent, and the greater the distance from the opponent that a defender will be able to make a tackle. This is the skill most desirable for defenders but can be helpful for midfielders and attackers. Also, technique effects the defending skills, the greater their technique, the more chance they have of dribbling past the player.
Playmaking - Players with high playmaking skill make their decisions who to pass to quicker, as well as choosing the best positioned player to pass the ball to.
Striker - Determines the accuracy and the force of kicks.

There are also several other parameters that will affect a player during a game and their career;

Form - Determines whether the player can take advantage of his skills in full. Players that are out of form will perform worse than they would if they were in a higher level of form.
Team Discipline - It reflects how accurately the player will follow the tactic during the match. Tactical Discipline is based on two subskills: Experience and Team-work.
Talent - Hidden ability of the player to enhance his skills. Determines the efficiency of training for both a first team player and a junior training in the sub junior school.
Age - After each season your players get older by one year. Younger players enhance their skills faster. As a player approaches his 30's, his skills may begin to gradually deteriorate. The older a player the faster the deterioration.
Height - Taller players will have better chances to win aerial duels when heading the ball. However, shorter players will be quicker in speeding up from a standing start..
Weight - If a player is too light, they will speed up slower, as they have a lower muscle mass. In addition a player with a high weight will speed up slower, as they are too heavy. Heavy players will tire more quickly, compared to lighter players.

Juniors System

On Sokker, you can choose whether your club will have a youth school or not. This is where young players are coached. The juniors are young players with too little experience or skills to play in official matches. In a youth school, you can occupy up to a maximum of 30 occupants to train. The juniors will stay in the youth school for a set number of weeks, during that time, they will increase in skills as they are coached. For your youths to train however, you will need to assign a Junior Coach. His general appraisal will determine how quickly the juniors will improve their skills. He will also decide when a player is ready for testing in the first team line-up. Your junior coach's general skill decides on how accurately the general skill of each junior is estimated. The higher the coach level, the more exact the junior level determined. Also, the more matches your junior plays, the more adequately the coach knows his total skill and shows it to you. You are only shown an overall skill of the junior and will not see their individual skills until you contract them when they leave the youth school. However, by playing them in youth matches, managers can use that to estimate their skills and positions.

Training
In order for player's skills to increase, players must be properly trained. Most types of training demand that the player played in the selected position during the week, in the friendly/cup game and/or the league game. A player who played in the same position (i.e., as a def) twice during the week will train better than one who played in only one game. Similarly, a player who played in an official match will train better than one who just played in a friendly. If a player played in two different positions during the week, the last match counts. Each player will train at different speeds based up to their hidden individual talent and the coach training them. If a player has a high talent, he is more likely to train faster than a player with a lower talent. When selecting a coach, the feature that counts most is his individual skills; his general appraisal does not influence the effectiveness of training. Select a head coach who has a high ability in training the skill you have chosen for the individual training.

Tactical Editor
The Tactics Editor is used to create your tactics and formations for future matches. You can find it by going to the match orders page of any future match and then clicking on the [Edit] link underneath the pitch image. Or alternatively, you can go to the training page, then at the top, click on "Tactics". There are default tactics that can be used during the match, however users are able to create their own tactic. It is the Tactical Editor, that for many users, defines Sokker from all other online soccer manager games. There are 35 squares in the tactics editor, making the number of tactics you could create limitless, and allowing the user to select where they would like to put a player. However, there is a maximum of 100 tactics you could save. The tactics you create and choose could ultimately be the decider whether a football match is won or lost.

Stadium
Every team has a stadium to host their home games. Optimizing the stadium size, stand types and ticket prices is very important to keep the team's financial health, as revenue coming from tickets is one of the main sources of income of every team.

There are four stand types:
Grass (standing): In each sector with grass, only 100 standing spectators are allowed by the sideline.
Terraces: Standing places made of concrete. It is the second cheapest type of stand. There are certain regulations imposed by the Football Association, restricting the size of stands with terraces. Your stadium cannot be solely made up of terraces.
Benches: A stand with sitting places but not as comfortable as seats.
Seats: The more expensive and luxurious stand. Building seats is more expensive than building benches, but they can bring more spectators to see the matches as some of them expect seats to sit in when watching their team.

There are many factors which will affect the attendance at a match, some of these include supporter mood, match type, size of supporters club, ticket prices, weather and stand preferences. It is possible to change the ticket prices from a range of 1 £ to 150 £. However, there are also a default price for stand types:

Grass and Field
In June 2012, Sokker introduced a new modification to grass the playing field. A new aspect, implemented in 2012, includes modifications and implementations around Grass and the Field. These features include;

"Grass Type - This feature allows you to choose what type of grass you would like to have in your stadium. There are different qualities of grass, each will have a different optimum condition depending on the quality of the grass. (see below).
Grass Mow - You can customise what you would like your field to look like. There are many options for you to choose from, for example you could choose to have a field with no specific mow, or you might want the grass to be mowed diagonally to produce diagonal lines of different colour gradient. Plus users will also be able to place their team logos with selected position and size.
Grass Condition - The condition of the grass will gradually get weaker each match and will need time to recover. The recovery rate of the grass will depend on the weather; it will grow best when it is not too hot and not too wet. There is though, a new feature that allows for a quicker recovery, through spending money on pitch maintenance. This will be available in the arena section. The other solution of pitch recovery is to lay new grass of the selected type. Also, different types of grass will have a different maximum condition. For example, garden grass will not reach much more than 50% of condition, so it will not be as good. On the pitch, in an area of weak condition, the ball may bounce in an unpredictable direction due to the unevenness of the grass, and also may jump in a direction a player didn't want when dribbling. The probability of injury will be higher on a pitch with poor condition and lower on a pitch with better condition (higher than 50% condition).
Pitch Size - On Sokker, you have the ability to change the size of your pitch, to how big (or small), you desire. This new feature may benefit how you use your tactics. The pitch modification will cost depending on the type of grass you have, and which grass mow you have."

Plus features
Although Sokker is entirely free to play, the game also has a premium feature called Plus. The purchase of Plus unlocks additional features that helps managers with their career, it does not however, give any unfair advantage over other users; "They just get more fun from the game - if you are not a subscriber, you have the same chance to achieve your goals in Sokker, as those with Plus." Match kits, Training effects monitoring, graphs, unlimited access to watch all matches, are just few of the features gained when you subscribe to plus.

Community
The community of Sokker has expanded the enjoyment far beyond the Sokker.org website. There are many supplemented websites and third party add-ons that enhance the Sokker experience.
Also, forum exists in many formats. There are international forums, national forums, division forums, friendly league forums, association forums, private forums and many more that enhance the communication between the Sokker users, enhancing the game enjoyment.

Third Party Tools
Programs and scripts, both standalone and browser-based are welcomed by Sokker as they enhance the experience of Sokker users. Sokker data can be downloaded through XML-files provided on the sokker.org website. Applications and programs take many forms. Managers Assistants such as oSokker and Android Application for Androids and Blackberry playbook generally help managers by organizing various team data and displaying it graphically and/or archiving it. There are also other tools, such as NT Database, designed specifically for NT managers that help NT managers organize the NT players.

References

Other websites
 Sokker Official Website
 Sokker Italian Website and Forum
 NT Database

Association football
Online games
Sports video games
2004 video games

Sokker


Dos Equis ("Two X's") is a Mexican beer made by the Cuauhtémoc Moctezuma Brewery. It was originally called "Twentieth Century" (Siglo XX).

There are several types of Dos Equis beer. The original is an amber lager packaged in brown bottles. Then came a Special Pale lager in green bottles. In 2014 came "Azul". It has a more robust taste, made from blue agave nectar and some new spices.

Dos Equis is well known in Mexico and the United States. This is partly because of advertisements called "The Most Interesting Man in the World". These ads have actor Jonathan Goldsmith and a narrator telling of his amazing exploits.

Beer
Mexican food
1897 establishments
19th-century establishments in Mexico

Dos Equis


Formal is a word used to describe anything that has form or structure. So it is something which is used or done in accordance with rules or ceremonies.

Formal  events have rules. 'Formal clothes' or 'formal attire' is a way of dressing to meet the rules for an event, such as a party or wedding. 'Formal attire' can be a suit, a tuxedo or a dress. People from all over the world have their own ideas about 'formal attire'. Most of the time formal attire clothes are the most beautiful or the best clothes a person owns. The opposite of "formal" is informal.  Informal clothes are comfortable clothes for general use, e.g. T shirt and jeans.  An informal ceremony might be a ceremony which is very relaxed instead of following an exact plan.  An informal way to greet a friend might be: "Hi, John!"

Examples:
Formal can be the way a person speaks or acts. To act in a formal way a person will follow the social rules of their culture or country. For example, they might greet each other by bowing, and they might address one another by their family name and their title (e.g. "Professor Smith").

A formal agreement is one which is explicit (written down) and reached by a formal discussion or negotiation. That means the negotiation is also done by set rules or procedures.

In mathematics, formal logic is a way of thinking about mathematics questions using strict rules.

Characteristics

Formal


Jet engine performance is the understanding of how, in jet engines, a particular fuel flow produces a definite amount of thrust at a particular point in the flight envelope. The behaviour of a jet engine and its effect both on the aircraft and the environment is categorized into many different engineering areas. These areas include combustion which relates to emissions, and rotor dynamics which is the area relating to the origin of vibrations transmitted to the airframe. Performance is the subject of a specialized discipline within aero-engine design and development.

In fixed-wing aircraft driven by one or more jet engines, certain aspects of performance such as thrust relate directly to the safe operation of the aircraft whereas other aspects of the engine operation such as noise and engine emissions affect the environment. The thrust, noise and emission elements of the operation of a jet engine are of vital importance in the takeoff phase of operation of the aircraft. The thrust and fuel consumption elements, and their variation with altitude, are of vital importance in the climb and cruise phases of the operation of the aircraft.

The fundamental performance task for a single-shaft turbojet is to match the operation of the compressor, turbine and propelling nozzle. For example, the way the compressor operates is determined by the flow resistances behind it, which occur in the combustor, turbine, tailpipe, and propelling nozzle.

Matching may be defined as designing, sizing, and manipulating the operating characteristics of the compressor, turbine and propelling nozzle.

Three fundamental observations are built upon as outlined below to develop the required understanding to match the components efficiently. The flow through the compressor is the same as that through the turbine. The speeds are the same. The power produced by the turbine equals that absorbed by the compressor. In addition, the flow resistance seen by the compressor is determined by the two restrictors downstream, namely the turbine nozzle area and the propelling nozzle exit area.

The above three ties between the compressor and turbine are adjusted and refined to account for the flows and powers not being equal due to, for example, compressor flow and electric and hydraulic power being diverted to the airframe. Thus the performance is understood and defined by using the practical engineering application of thermodynamics and aerodynamics.

This article covers a wide scope of the discipline of jet engine performance.

Navigating this article
Specific values of thrust and fuel consumption are promised to a prospective aircraft customer, and these are derived using procedures detailed in sections "Design point performance equations" and "Simple off-design calculation". An explanation for "off-design" is given in "General".

An aircraft receives pneumatic, electric and hydraulic power in return for some of the fuel it supplies. This is mentioned in Installation Effects. These effects define the difference between the performance of an uninstalled engine (as measured on a test bed) and one installed on an aircraft.

When air is taken from the compressor and used to cool the turbine it has an adverse effect on the amount of fuel required to give the required thrust. This is covered in "Cooling Bleeds".

The effect of fundamental design changes to the engine, such as increased pressure ratio and turbine inlet temperature, is covered in "Cycle improvements'. Ways to increase the pressure ratio are also covered.

The effects of over-fueling and under-fueling which occur with changes in thrust demand are covered in the "Transient model".

There is an explanation of the Husk plot which is a concise way of summarizing the performance of the engine.

The thrust available is restricted by the turbine temperature limit at high ambient temperatures as explained in the "Rated performance" sections.

Design point

TS diagram
 Temperature vs. entropy (TS) diagrams (see example RHS) are usually used to illustrate the cycle of gas turbine engines. Entropy represents the degree of disorder of the molecules in the fluid and tends to increase as energy is converted between different forms, e.g. chemical and mechanical.

The TS diagram shown on the RHS is for a single spool turbojet, where a single drive shaft connects the turbine unit with the compressor unit.

Apart from stations 0 and 8s, stagnation pressure and stagnation temperature are used. Station 0 is ambient. Stagnation quantities are frequently used in gas turbine cycle studies, because no knowledge of the flow velocity is required.

The processes depicted are:

Freestream (stations 0 to 1)

In the example, the aircraft is stationary, so stations 0 and 1 are coincident. Station 1 is not depicted on the diagram.

Intake (stations 1 to 2)

In the example, a 100% intake pressure recovery is assumed, so stations 1 and 2 are coincident.

Compression (stations 2 to 3)

The ideal process would appear vertically on a TS diagram. In the real process, there is friction, turbulence, and, possibly, shock losses, making the exit temperature, for a given pressure ratio, higher than ideal. The shallower the positive slope on the TS diagram, the less efficient the compression process.

Combustion (stations 3 to 4)

Heat (usually by burning fuel) is added, raising the temperature of the fluid.  There is an associated pressure loss, some of which is unavoidable.

Turbine (stations 4 to 5)

The temperature rise in the compressor dictates that there will be an associated temperature drop across the turbine. Ideally, the process would be vertical on a TS diagram. However, in the real process, friction and turbulence cause the pressure drop to be greater than ideal. The shallower the negative slope on the TS diagram, the less efficient the expansion process.

Jetpipe (stations 5 to 8)

In the example the jetpipe is very short, so there is no pressure loss. Consequently, stations 5 and 8 are coincident with the TS diagram.

Nozzle (stations 8 to 8s)

These two stations are both at the throat of the (convergent) nozzle. Station 8s represents static conditions. Not shown on the example TS diagram is the expansion process, external to the nozzle, down to ambient pressure.

Design point performance equations

In theory, any combination of flight condition/throttle setting can be nominated as the engine performance Design Point. Usually, however, the Design Point corresponds to the highest corrected flow at the inlet to the compression system (e.g. Top-of-Climb, Mach 0.85, 35,000 ft, ISA).

The design point net thrust of any jet engine can be estimated by working through the engine cycle, step by step. Below are the equations for a single spool turbojet.

Freestream

The stagnation (or total) temperature in the freestream approaching the engine can be estimated using the following equation, derived from the Steady Flow Energy Equation:

The corresponding freestream stagnation (or total) pressure is:

Intake

Since there is no work or heat loss in the intake under steady-state conditions:

However, friction and shock losses in the intake system must be accounted for:

Where RR is the ram recovery factor, corresponding to the loss of total pressure in the inlet.

Compressor

The actual discharge temperature of the compressor, assuming a polytropic efficiency is given by:

Normally a compressor pressure ratio is assumed, so:

Combustor

A turbine rotor inlet temperature is usually assumed:

The pressure loss in the combustor reduces the pressure at turbine entry:

Turbine

Equating the turbine and compressor powers and ignoring any power offtake (e.g. to drive an alternator, pump, etc.), we have:

A simplifying assumption sometimes made is for the addition of fuel flow to be exactly offset by an overboard compressor bleed, so mass flow remains constant throughout the cycle.

The pressure ratio across the turbine can be calculated, assuming a turbine polytropic efficiency:

Obviously:

Jetpipe

Since, under Steady-State conditions, there is no work or heat loss in the jetpipe:

However, the jetpipe pressure loss must be accounted for:

Nozzle

Is the nozzle choked? The nozzle is choked when the throat Mach number = 1.0. This occurs when the nozzle pressure ratio reaches or exceeds a critical level:

If  then the nozzle is CHOKED.

If  then the nozzle is UNCHOKED.

Choked Nozzle

The following calculation method is only suitable for choked nozzles.

Assuming the nozzle is choked, the nozzle static temperature is calculated as follows:

Similarly for the nozzle static pressure:

The nozzle throat velocity (squared) is calculated using the Steady Flow Energy Equation:

The density of the gases at the nozzle throat is given by:

Nozzle throat effective area is estimated as follows:

Gross thrust

There are two terms in the nozzle gross thrust equation; ideal momentum thrust and ideal pressure thrust. The latter term is only non-zero if the nozzle is choked:

Unchoked nozzle

The following special calculation is required if the nozzle happens to be unchoked.

Once unchoked, the nozzle static pressure is equal to ambient pressure:

The nozzle static temperature is calculated from the nozzle total/static pressure ratio:

The nozzle throat velocity (squared) is calculated, as before, using the steady flow energy equation:

Gross thrust

The nozzle pressure thrust term is zero if the nozzle is unchoked, so only the Momentum Thrust needs to be calculated:

Ram drag

In general, there is a ram drag penalty for taking air onboard via the intake:

Net thrust

The ram drag must be deducted from the nozzle gross thrust:

The calculation of the combustor fuel flow is beyond the scope of this text but is proportional to the combustor entry airflow and a function of the combustor temperature rise.

Note that mass flow is the sizing parameter: doubling the airflow, doubles the thrust and the fuel flow. However, the specific fuel consumption (fuel flow/net thrust) is unaffected, assuming scale effects are neglected.

Similar design point calculations can be done for other types of jet engine e.g. turbofan, turboprop, ramjet, etc.

The method of the calculation shown above is fairly crude but is useful for gaining a basic understanding of aeroengine performance. Most engine manufacturers use a more exact method, known as True Specific Heat. High pressures and temperatures at elevated levels of supersonic speeds would invoke the use of even more exotic calculations: i.e. Frozen Chemistry and Equilibrium Chemistry.

Worked example

Calculate the net thrust of the following single spool turbojet cycle at Sea Level Static, ISA, using Imperial units for illustration purposes:

Key design parameters:

Intake air mass flow,

(45.359 kg/s in SI units)

Assume the gas flow is constant throughout the engine.

Overall pressure ratio,

Turbine rotor inlet temperature,

(factor-up by 1.8, if working with degrees Rankine)

Design component performance assumptions:

Intake pressure recovery factor,

Compressor polytropic efficiency,

Turbine polytropic efficiency,

Combustor pressure loss is 5%, so the combustor pressure ratio

Jetpipe pressure loss is 1%, so the jetpipe pressure ratio

Nozzle thrust coefficient,

Constants:

The ratio of specific heats for air,

The ratio of specific heats for combustion products,

Specific heat at constant pressure for air,

(use 1.004646 kW·s/(kg·K) when working with SI units
and use 0.3395 hp·s/(lb·°R) if working with American units)

Specific heat at constant pressure for combustion products,
(use 1.1462 kW·s/(kg·K) when working with SI units
and use 0.387363889 hp·s/(lb·°R) if working with American units)

Acceleration of gravity,
(use 10.00 when working with SI units)

Mechanical equivalent of heat,
(use 1 when working with SI units)

Gas constant,
(use 0.287052 kN·m/(kg·K) when working with SI units
and use 53.3522222 ft·lbf/(lb·°R) if working with American units including degrees Rankine)

Ambient conditions

A sea level pressure altitude implies the following:

Ambient pressure,  (assume 101.325 kN/m² if working in SI units)

Sea level, ISA conditions (i.e. Standard Day) imply the following:

Ambient temperature,

(Note: this is an absolute temperature i.e. )

(Use 518.67 °R, if working with American units)

Freestream

Since the engine is static, both the flight velocity,
and the flight Mach number, are zero

So:

Intake

Compressor

Combustor

Turbine

Jetpipe

Nozzle

Since , the nozzle is CHOKED

Choked Nozzle

NOTE: inclusion of 144 in²/ft² to obtain density in lb/ft³.

NOTE: inclusion of 144 in²/ft² to obtain an area in in².

Gross Thrust

The first term is the momentum thrust which contributes most of the nozzle gross thrust. Because the nozzle is choked (which is the norm on a turbojet), the second term, the pressure thrust, is non-zero.

Ram Drag

The ram drag in this particular example is zero, because the engine is stationary and the flight velocity is therefore zero.

Net thrust

To retain accuracy, only the final answer should be rounded off.

Cooling Bleeds
The above calculations assume that the fuel flow added in the combustor completely offsets the bleed air extracted at compressor delivery to cool the turbine system. This is pessimistic, since the bleed air is assumed to be dumped directly overboard (thereby bypassing the propulsion nozzle) and unable to contribute to the thrust of the engine.

In a more sophisticated performance model, the cooling air for the first row of (static) turbine nozzle guide vanes (immediately downstream of the combustor) can be safely disregarded, since for a given (HP) rotor inlet temperature it does not affect either the combustor fuel flow or the net thrust of the engine. However, the turbine rotor cooling air must be included in such a model. The rotor cooling bleed air is extracted from compressor delivery and passes along narrow passageways before being injected into the base of the rotating blades. The bleed air negotiates a complex set of passageways within the aerofoil extracting heat before being dumped into the gas stream adjacent to the blade surface. In a sophisticated model, the turbine rotor cooling air is assumed to quench the main gas stream emerging from turbine, reducing its temperature, but also increasing its mass flow:

i.e.

The bleed air cooling the turbine discs is treated in a similar manner. The usual assumption is that the low-energy disc cooling air cannot contribute to the engine cycle until it has passed through one row of blades or vanes.

Naturally, any bleed air returned to the cycle (or dumped overboard) must also be deducted from the main airflow at the point it is bled from the compressor. If some of the cooling air is bled from part way along the compressor (i.e. interstage), the power absorbed by the unit must be adjusted accordingly.

Cycle improvements
Increasing the design overall pressure ratio of the compression system raises the combustor entry temperature. Therefore, at a fixed fuel flow and airflow, there is an increase in turbine inlet temperature. Although the higher temperature rise across the compression system implies a larger temperature drop over the turbine system, the nozzle temperature is unaffected, because the same amount of heat is being added to the total system. There is, however, a rise in nozzle pressure, because the turbine expansion ratio increases more slowly than the overall pressure ratio (which is inferred by the divergence of the constant pressure lines on the TS diagram). Consequently, net thrust increases, implying a specific fuel consumption (fuel flow/net thrust) decrease. Therefore, turbojets can be made more fuel-efficient by raising the overall pressure ratio and turbine inlet temperature in unison.

However, better turbine materials and/or improved vane/blade cooling are required to cope with increases in both turbine inlet temperature and compressor delivery temperature. Increasing the latter may also require better compressor materials. Also, higher combustion temperatures can potentially lead to greater emissions of nitrogen oxides, associated with acid rain.

Adding a rear stage to the compressor, to raise the overall pressure ratio, does not require a shaft speed increase, but it reduces core size and requires a smaller flow size turbine, which is expensive to change.

Alternatively, adding a zero (i.e. front) stage to the compressor, to increase the overall pressure ratio, will require an increase in shaft speed (to maintain the same blade tip Mach number on each of the original compressor stages, since the delivery temperature of each of these stages will be higher than datum). The increase in shaft speed raises the centrifugal stresses in both the turbine blade and disc. This together with increases in the hot gas and cooling air (from the compressor) temperatures implies a decrease in component lives and/or an upgrade in component materials. Adding a zero stage also induces more airflow into the engine, thereby increasing net thrust.

If the increased overall pressure ratio is obtained aerodynamically (i.e. without adding stage/s), an increase in shaft speed will still probably be required, which affects blade/disc stresses and component lives/material.

Other gas turbine engine types
Design point calculations for other gas turbine engine types are similar in format to that given above for a single spool turbojet.

The design point calculation for a two spool turbojet has two compression calculations: one for the Low Pressure (LP) Compressor and one for the High Pressure (HP) Compressor. There are also two turbine calculations: one for the HP Turbine and one for the LP Turbine.

In a two-spool unmixed turbofan, the LP Compressor calculation is usually replaced by Fan Inner (i.e. hub) and Fan Outer (i.e. tip) compression calculations. The power absorbed by these two "components" is taken as the load on the LP turbine. After the Fan Outer compression calculation, there is a Bypass Duct pressure loss/Bypass Nozzle expansion calculation. Net thrust is obtained by deducting the intake ram drag from the sum of the Core Nozzle and Bypass Nozzle gross thrusts.

A two-spool mixed turbofan design point calculation is very similar to that for an unmixed engine, except the Bypass Nozzle calculation is replaced by a Mixer calculation, where the static pressures of the core and bypass streams at the mixing plane are usually assumed to be equal.

Off-design

General

An engine is said to be running off-design if any of the following apply:

a) change of throttle setting
b) change of altitude
c) change of flight speed
d) change of climate
e) change of installation (e.g. customer bleed or power off-take or intake pressure recovery)
f) change in geometry

Although each off-design point is effectively a design point calculation, the resulting cycle (normally) has the same turbine and nozzle geometry as that at the engine design point. The final nozzle cannot be over or underfilled with the flow. This rule also applies to the turbine nozzle guide vanes, which act like small nozzles.

Simple Off-design Calculation

Design point calculations are normally done by a computer program. By the addition of an iterative loop, such a program can also be used to create a simple off-design model.

In an iteration, a calculation is undertaken using guessed values for the variables. At the end of the calculation, the constraint values are analyzed, and an attempt is made to improve the guessed values of the variables. The calculation is then repeated using the new guesses. This procedure is repeated until the constraints are within the desired tolerance (e.g. 0.1%).

Iteration variables

The three variables required for a single spool turbojet iteration are the key design variables:

1) some function of combustor fuel flow e.g. turbine rotor inlet temperature

2) corrected engine mass flow i.e.

3) compressor pressure ratio i.e.

Iteration constraints (or matching quantities)

The three constraints imposed would typically be:

1) engine match e.g.  or  or , etc.

2) nozzle area e.g.  vs

3) turbine flow capacity e.g.  vs

The latter two are the physical constraints that must be met, whilst the former is some measure of throttle setting.

Note: Corrected flow is the flow that would pass through a device, if the entry pressure and temperature corresponded to ambient conditions at sea level on a Standard Day.

Results

Plotted above are the results of several off-design calculations, showing the effect of throttling a jet engine from its design point condition.  This line is known as the compressor steady state (as opposed to transient) working line. Over most of the throttle range, the turbine system on a turbojet operates between choked planes. All the turbine throats are choked, as well as the final nozzle. Consequently, the turbine pressure ratio stays essentially constant. This implies a fixed. Since turbine rotor entry temperature, usually falls with throttling, the temperature drop across the turbine system, , must also decrease. However, the temperature rise across the compression system, is proportional to .Consequently, the ratio  must also fall, implying a decrease in the compression system pressure ratio. The non-dimensional (or corrected flow) at the compressor exit tends to stay constant, because it 'sees', beyond the combustor, the constant corrected flow of the choked turbine. Consequently, there must be a decrease in compressor entry corrected flow, as the compressor pressure ratio falls. Therefore, the compressor steady state working line has a positive slope, as shown above, on the RHS.

The ratio  is the quantity that determines the throttle setting of the engine. So, for instance, raising intake stagnation temperature by increasing flight speed, at a constant, will cause the engine to throttle back to a lower corrected flow/pressure ratio.

Fairly obviously, when an engine is throttled-back, it will lose net thrust. This drop-in thrust is mainly caused by the reduction in air mass flow, but the reduction in turbine rotor inlet temperature and degradations in component performance will also contribute.

The simple off-design calculation outlined above is somewhat crude since it assumes:

1) no variation in compressor and turbine efficiency with throttle setting

2) no change in pressure losses with component entry flow

3) no variation in turbine flow capacity or nozzle discharge coefficient with throttle setting

Furthermore, there is no indication of relative shaft speed or compressor surge margin.

Complex Off-design Calculation

A more refined off-design model can be created using compressor maps and turbine maps to predict off-design corrected mass flows, pressure ratios, efficiencies, relative shaft speeds, etc. A further refinement is to allow the component off-design pressure losses to vary with corrected mass flow, Mach number, etc.

The iteration scheme is similar to that of the Simple Off-design Calculation.

Iteration variables

Again, three variables are required for a single spool turbojet iteration, typically:

1) some function of combustor fuel flow e.g.

2) compressor corrected speed e.g.

3) an independent variable indicative of the compressor operating point up a speed line e.g.

Therefore, compressor corrected speed replaces corrected engine mass flow and Beta replaces compressor pressure ratio.

Iteration constraints (or matching quantities)

The three constraints imposed would typically be similar to before:

1) engine match e.g.  or or , etc.

2) nozzle area e.g.  vs

3) turbine flow capacity e.g.  vs

During the Complex Off-design calculation, the operating point on the compressor map is constantly being guessed (in terms of  and ) to obtain an estimate of the compressor mass flow, pressure ratio and efficiency. After the combustion calculation is completed, the implied compressor mechanical shaft speed is used to estimate the turbine corrected speed (i.e. ). Typically, the turbine load (power demanded) and entry flow and temperature are used to estimate the turbine enthalpy drop/inlet temperature (i.e. ). The estimated turbine corrected speed and enthalpy drop/inlet temperature parameters are used to obtain, from the turbine map, an estimate of the turbine corrected flow ()
and efficiency (i.e. ). The calculation then continues, in the usual way, through the turbine, jetpipe and nozzle. If the constraints are not within tolerance, the iteration engine makes another guess at the iteration variables and the iterative loop is restarted.

Plotted on the LHS are the results of several off-design calculations, showing the effect of throttling a jet engine from its design point condition. The line produced is similar to the working line shown above, but it is now superimposed on the compressor map and gives an indication of corrected shaft speed and compressor surge margin.

Performance model
Whatever it's sophistication, the off-design program is not only used to predict the off-design performance of the engine, but also assist in the design process (e.g. estimating maximum shaft speeds, pressures, temperatures, etc. to support component stressing). Other models will be constructed to simulate the behavior (in some detail) of the various individual components (e.g. rotor 2 of the compressor).

Installation effects

More often than not, the design point calculation is for an uninstalled engine. Installation effects are normally introduced at off-design conditions and will depend on the engine application.

A partially installed engine includes the effect of:

a) the real intake having a pressure recovery of less than 100%

b) air being bled from the compression system for cabin/cockpit conditioning and to cool the avionics

c) oil and fuel pump loads on the HP shaft

In addition, in a fully installed engine, various drags erode the effective net thrust of the engine:

1) an air intake spilling air creates drag

2) exhaust gases, exiting the hot nozzle, can scrub the external part of the nozzle plug (where applicable) and create drag

3) if the jet engine is a civil turbofan, bypass air, exiting the cold nozzle, can scrub the gas generator cowl and the submerged portion of the pylon (where applicable) and create drag

Deducting these throttle-dependent drags (where applicable) from the net thrust calculated above gives the streamtube net thrust.

There is, however, another installation effect: freestream air scrubbing an exposed fan cowl and its associated pylon (where applicable) will create drag. Deducting this term from the streamtube net thrust yields the force applied by the engine to the airframe proper.

In a typical military installation, where the engine is buried within the airframe, only some of the above installation effects apply.

Transient model

So far, we have examined steady state performance modelling.

A crude transient performance model can be developed by relatively minor adjustments to the off-design calculation. A transient acceleration (or deceleration) is assumed to cover a large number of small-time steps of, say, 0.01 s duration. During each time step, the shaft speed is assumed to be momentarily constant. In the modified off-design iteration,  is frozen and a new variable, the excess turbine power , allowed to float instead. After the iteration has converged, the excess power is used to estimate the change in shaft speed:

Now:

Acceleration torque = spool inertia * shaft angular acceleration

   =     /

Rearranging:

 = ( /(    ))

But:

  =       /

So:

 = ( / (     ))

Or approximating:

 = (  / (  ))

This change in shaft speed is used to calculate a new (frozen) shaft speed for the next time interval:

  =    +

The whole process, described above, is then repeated for the new time:

 =   +

The starting point for the transient is some steady state point (e.g. Ground Idle, Sea Level Static, ISA). A ramp of fuel flow versus time is, for instance, fed into the model to simulate, say, a slam acceleration (or deceleration). The transient calculation is first undertaken for time zero, with the steady state fuel flow as the engine match, which should result in zero excess turbine power. By definition, the first transient calculation should reproduce the datum steady state point. The fuel flow for    is calculated from the fuel flow ramp and is used as the revised engine match in the next transient iterative calculation. This process is repeated until the transient simulation is completed.

The transient model described above is pretty crude, since it only takes into account inertia effects, other effects being ignored. For instance, under transient conditions the entry mass flow to a volume (e.g. jetpipe) needn't be the same as the exit mass flow; i.e. the volume could be acting as an accumulator, storing or discharging gas. Similarly, part of the engine structure (e.g. nozzle wall) could be extracting or adding heat to the gas flow, which would affect that component's discharge temperature.

During a Slam Acceleration on a single spool turbojet, the working line of the compressor tends to deviate from the steady state working line and adopt a curved path, initially going towards surge, but slowly returning to the steady state line, as the fuel flow reaches a new higher steady state value. During the initial overfuelling, the inertia of the spool tends to prevent the shaft speed from accelerating rapidly. Naturally, the extra fuel flow increases the turbine rotor entry temperature,   . Since the turbine operates between two choked planes (i.e. the turbine and nozzle throats), the turbine pressure ratio and the corresponding temperature drop/entry temperature, ,  remain approximately constant. Since  increases, so must the temperature drop across the turbine and the turbine power output.  This extra turbine power increases the temperature rise across the compressor and, therefore, the compressor pressure ratio. Since the corrected speed of the compressor has hardly changed, the working point tends to move upwards, along a line of roughly constant corrected speed. As time progresses the shaft begins to accelerate and the effect just described diminishes.

During a Slam Deceleration, the opposite trend is observed; the transient compressor working line goes below the steady state line.

The transient behavior of the high pressure (HP) compressor of a turbofan is similar to that described above for a single spool turbojet.

Performance software

Over the years a number of software packages have been developed to estimate the design, off-design and transient performance of various types of gas turbine engine. Most are used in-house by the various aero-engine manufacturers, but several software packages are available to the general public (e.g. NPSS http://www.npssconsortium.org, GasTurb http://www.gasturb.de, EngineSim http://www.grc.nasa.gov/WWW/K-12//airplane/ngnsim.html, GSP https://www.gspteam.com/, PROOSIS http://www.proosis.com).

Husk plot

A Husk Plot is a concise way of summarizing the performance of a jet engine. The following sections describe how the plot is generated and can be used.

Thrust/SFC loops

Specific Fuel Consumption (i.e. SFC), defined as fuel flow/net thrust, is an important parameter reflecting the overall thermal (or fuel) efficiency of an engine.

As an engine is throttled back there will be a variation of SFC with net thrust, because of changes in the engine cycle (e.g. lower overall pressure ratio) and variations in component performance (e.g. compressor efficiency). When plotted, the resultant curve is known as a thrust/SFC loop. A family of these curves can be generated at Sea Level, Standard Day, conditions over a range of flight speeds. A Husk Plot (RHS) can be developed using this family of curves. The net thrust scale is simply relabeled , where  is relative ambient pressure, whilst the SFC scale is relabeled , where  is relative ambient temperature. The resulting plot can be used to estimate engine net thrust and SFC at any altitude, flight speed and climate for a range of throttle setting.

Selecting a point on the plot, net thrust is calculated as follows:

Clearly, net thrust falls with altitude, because of the decrease in ambient pressure.

The corresponding SFC is calculated as follows:

At a given point on the Husk Plot, SFC falls with decreasing ambient temperature (e.g. increasing altitude or colder climate). The basic reason why SFC increases with flight speed is the implied increase in ram drag.

Although a Husk Plot is a concise way of summarizing the performance of a jet engine, the predictions obtained at altitude will be slightly
optimistic. For instance, because ambient temperature remains constant above 11,000 m (36,089 ft) altitude, at a fixed non-dimensional point the Husk plot would yield no change in SFC with increasing altitude. In reality, there would be a small, steady, increase in SFC, owing to the falling Reynolds number.

Thrust lapse

The nominal net thrust quoted for a jet engine usually refers to the Sea Level Static (SLS) condition, either for the International Standard Atmosphere (ISA) or a hot day condition (e.g. ISA+10 °C). As an example, the GE90-76B has a take-off static thrust of 76,000 lbf (360 kN) at SLS, ISA+15 °C.

Naturally, net thrust will decrease with altitude, because of the lower air density. There is also, however, a flight speed effect.

Initially as the aircraft gains speed down the runway, there will be little increase in nozzle pressure and temperature, because the ram rise in the intake is very small. There will also be little change in mass flow. Consequently, nozzle gross thrust initially only increases marginally with flight speed. However, being an air breathing engine (unlike a conventional rocket) there is a penalty for taking on-board air from the atmosphere. This is known as ram drag. Although the penalty is zero at static conditions, it rapidly increases with flight speed causing the net thrust to be eroded.

As flight speed builds up after take-off, the ram rise in the intake starts to have a significant effect upon nozzle pressure/temperature and intake airflow, causing nozzle gross thrust to climb more rapidly. This term now starts to offset the still increasing ram drag, eventually causing net thrust to start to increase. In some engines, the net thrust at say Mach 1.0, sea level can even be slightly greater than the static thrust. Above Mach 1.0, with a subsonic inlet design, shock losses tend to decrease net thrust, however a suitably designed supersonic inlet can give a lower reduction in intake pressure recovery, allowing net thrust to continue to climb in the supersonic regime.

The thrust lapse described above depends on the design specific thrust and, to a certain extent, on how the engine is rated with intake temperature. Three possible ways of rating an engine are depicted on the above Husk Plot. The engine could be rated at constant turbine entry temperature, shown on the plot as . Alternatively, a constant mechanical shaft speed could be assumed, depicted as . A further alternative is a constant compressor corrected speed, shown as . The variation of net thrust with flight Mach number can be clearly seen on the Husk Plot.

Other trends

The Husk Plot can also be used to indicate trends in the following parameters:

1) turbine entry temperature

So as ambient temperature falls (through increasing altitude or a cooler climate), turbine entry temperature must also fall to stay at the same non-dimensional
point on the Husk Plot. All the other non-dimensional groups (e.g. corrected flow, axial and peripheral Mach numbers, pressure ratios, efficiencies, etc. will also stay constant).

2) mechanical shaft speed

As ambient temperature falls (through increasing altitude or a cooler climate), mechanical shaft speed must also decrease to remain at the same non-dimensional point.

By definition, compressor corrected speed, , must remain constant at a given non-dimensional point.

Rated Performance

Civil

 Nowadays, civil engines are usually flat-rated on net thrust up to a 'kink-point' climate. So at a given flight condition, net thrust is held approximately constant over a very wide range of ambient temperature, by increasing (HP) turbine rotor inlet temperature (RIT or SOT). However, beyond the kink-point, SOT is held constant and net thrust starts to fall for further increases in ambient temperature. Consequently, aircraft fuel load and/or payload must be decreased.

Usually, for a given rating, the kink-point SOT is held constant, regardless of altitude or flight speed.

Some engines have a special rating, known as the 'Denver Bump'. This invokes a higher RIT than normal, to enable fully laden aircraft to Take-off safely from Denver, CO in the summer months. Denver Airport is extremely hot in the summer and the runways are over a mile above sea level. Both of these factors affect engine thrust.

Military

 The rating systems used on military engines vary from engine to engine. A typical military rating structure is shown on the left. Such a rating system maximizes the thrust available from the engine cycle chosen, whilst respecting the aerodynamic and mechanical limits imposed on the turbomachinery. If there is adequate thrust to meet the aircraft's mission in a particular range of intake temperature, the engine designer may elect to truncate the schedule shown, to lower the turbine rotor inlet temperature and, thereby, improve engine life.

At low intake temperatures, the engine tends to operate at maximum corrected speed or corrected flow. As intake temperature rises, a limit on (HP) turbine rotor inlet temperature (SOT) takes effect, progressively reducing corrected flow. At even higher intake temperatures, a limit on compressor delivery temperature (T3) is invoked, which decreases both SOT and corrected flow.

 The effect of design intake temperature is shown on the right-hand side.

An engine with a low design T1 combines high corrected flow with high rotor turbine temperature (SOT), maximizing net thrust at low T1 conditions (e.g. Mach 0.9, 30000 ft, ISA). However, although turbine rotor inlet temperature stays constant as T1 increases, there is a steady decrease in corrected flow, resulting in poor net thrust at high T1 conditions (e.g. Mach 0.9, sea level, ISA).

Although an engine with a high design T1 has a high corrected flow at low T1 conditions, the SOT is low, resulting in a poor net thrust. Only at high T1 conditions is there the combination of a high corrected flow and a high SOT, to give good thrust characteristics.

A compromise between these two extremes would be to design for a medium intake temperature (say 290 K).

As T1 increases along the SOT plateau, the engines will throttle back, causing both a decrease in corrected airflow and overall pressure ratio. As shown, the chart implies a common T3 limit for both the low and high design T1 cycles. Roughly speaking, the T3 limit will correspond to a common overall pressure ratio at the T3 breakpoint. Although both cycles will increase throttle setting as T1 decreases, the low design T1 cycle has a greater 'spool-up' before hitting the corrected speed limit. Consequently, the low design T1 cycle has a higher design overall pressure ratio.

Nomenclature

   flow area
  calculated nozzle effective throat area
 design point nozzle effective throat area
 nozzle geometric throat area
 shaft angular acceleration
 arbitrary lines which dissect the corrected speed lines on a compressor characteristic
 specific heat at constant pressure for air
  specific heat at constant pressure for combustion products
 calculated nozzle discharge coefficient
 thrust coefficient
 ambient pressure/Sea Level ambient pressure
 turbine enthalpy drop/inlet temperature
  change in mechanical shaft speed
 excess shaft power
  excess shaft torque
 compressor polytropic efficiency
  turbine polytropic efficiency
   acceleration of gravity
  gross thrust
  net thrust
  ram drag
  ratio of specific heats for air
  ratio of specific heats for combustion products
   spool inertia
   mechanical equivalent of heat
   constant
   constant
   constant
   flight Mach number
 compressor mechanical shaft speed
 compressor corrected shaft speed
 turbine corrected shaft speed
   static pressure
   stagnation (or total) pressure
 compressor pressure ratio
  intake pressure recovery factor
   gas constant
 density
 specific fuel consumption
 stator outlet temperature
 (turbine) rotor inlet temperature
   static temperature or time
  stagnation (or total) temperature
  intake stagnation temperature
  compressor delivery total temperature
 ambient temperature/Sea Level, Standard Day, ambient temperature
 total temperature/Sea Level, Standard Day, ambient temperature
  velocity
 mass flow
 calculated turbine entry corrected flow
 compressor corrected inlet flow
 design point turbine entry corrected flow
 corrected entry flow from turbine characteristic (or map)
 combustor fuel flow

See also
 Index of aviation articles
 Aircraft engine performance

Notes

References
 Kerrebrock, Jack L. (1992), Aircraft Engines and Gas Turbines, The MIT Press, Cambridge, Massachusetts USA.

Jet engines
Aircraft performance

Jet engine performance