Pittsfield is the largest city and the historic county seat of Berkshire County, United States. It is the principal city of the Pittsfield, Massachusetts Metropolitan Statistical Area which encompasses all of Berkshire County; the population was 44,737 at the 2010 census. Although the population has declined in recent decades, Pittsfield remains the third largest municipality in western Massachusetts, behind only Springfield and Chicopee. In 2005, Farmers Insurance ranked Pittsfield 20th in the United States as "Most Secure Place To Live" among small towns with fewer than 150,000 residents. In 2006, Forbes ranked Pittsfield as number 61 in its list of Best Small Places for Business. In 2008, Country Home magazine ranked Pittsfield as #24 in a listing of "green cities" east of the Mississippi. In 2009, the City of Pittsfield was chosen to receive a 2009 Commonwealth Award, Massachusetts' highest award in the arts and sciences. In 2010, the Financial Times proclaimed Pittsfield the "Brooklyn of the Berkshires", in an article covering its recent renaissance.
In 2012, the city was listed among the 10 best places for single people to retire in the U. S. by U. S. News, due to the high number of single older residents and higher likelihood of finding companionship or a partner. In 2017, the Arts Vibrancy Index compiled by the National Center for Arts Research ranked Pittsfield and Berkshire County as the No. 1 medium-sized community in the nation for the arts. The Mahican Native American nation, an Algonquian people, inhabited Pittsfield and the surrounding area until the early 1700s, the population reduced by war and disease, many migrated westward or lived on the fringes of society. In 1738, a wealthy Bostonian named Col. Jacob Wendell bought 24,000 acres of lands known as Pontoosuck, a Mohican word meaning "a field or haven for winter deer", as a speculative investment, he planned to resell to others who would settle there. He formed a partnership with Philip Livingston, a wealthy kinsman from Albany, New York, Col. John Stoddard of Northampton, who had claim to 1,000 acres here.
A group of young men came and began to clear the land in 1743, but the threat of Indian raids around the time of King George's War soon forced them to leave, the land remained unoccupied by Englishmen for several more years. Soon, many others arrived from Westfield, a village began to grow, incorporated as Pontoosuck Plantation in 1753 by Solomon Deming, Simeon Crofoot, Stephen Crofoot, Charles Goodrich, Jacob Ensign, Samuel Taylor, Elias Woodward. Mrs. Deming was the first and the last of the original settlers, dying in March 1818 at the age of 92. Solomon Deming died in 1815 at the age of 96. Pittsfield was incorporated in 1761. Royal Governor Sir Francis Bernard named Pittsfield after British nobleman and politician William Pitt. By 1761 there were 200 residents, the plantation became the Township of Pittsfield. By the end of the Revolutionary War, Pittsfield had expanded to nearly 2,000 residents, including Colonel John Brown, who began accusing Benedict Arnold as a traitor in 1776, several years before Arnold defected to the British.
Brown wrote in his winter 1776-77 handbill, "Money is this man's God, to get enough of it he would sacrifice his country."Pittsfield was an agricultural area, because of the many brooks that flowed into the Housatonic River. With the introduction of Merino sheep from Spain in 1807, the area became the center of woolen manufacturing in the United States, an industry that would dominate the community's economy for a century; the town was a bustling metropolis by the late 19th century. In 1891, the City of Pittsfield was incorporated, William Stanley, Jr. who had relocated his Electric Manufacturing Company to Pittsfield from Great Barrington, produced the first electric transformer. Stanley's enterprise was the forerunner of the internationally known corporate giant, General Electric. Thanks to the success of GE, Pittsfield's population in 1930 had grown to more than 50,000. While GE Advanced Materials continues to be one of the city's largest employers, a workforce that once topped 13,000 was reduced to less than 700 with the demise and/or relocation of the transformer and aerospace portions of the General Electric empire.
On October 8, 2015, SABIC announced it would relocate its headquarters from Pittsfield to Houston, Texas. General Dynamics occupies many of the old GE buildings, its workforce is expanding. Much of General Dynamics' local success is based on the awarding of government contracts related to its advanced information systems. On September 3, 1902, at 10:15 AM, during a two-week tour through New England campaigning for Republican congressmen, the barouche transporting President Theodore Roosevelt from downtown Pittsfield to the Pittsfield Country Club collided head-on with a trolley. Roosevelt, Massachusetts Governor Winthrop Murray Crane, secretary to the president George Bruce Cortelyou, bodyguard William Craig were thrown into the street. Craig was killed. Roosevelt, whose face and left shin were badly bruised, nearly came to blows with the trolley motorman, Euclid Madden. Madden was charged with manslaughter, to which he pleaded guilty, he was sentenced to six months in a heavy fine. In 2004, historian John Thorn discovered a reference to a 1791 by-law prohibiting anyone from playing "baseball" within 80 yards of the new meeting house in Pittsfield.
A reference librarian, AnnMarie Harris
Carillon Historical Park
Carillon Historical Park is a 65-acre park and museum in Dayton, which contains historic buildings and exhibits concerning the history of technology and the history of Dayton and its residents from 1796 to the present. The historical elements of the park were the brainchild of Colonel Edward Deeds; the major sections include settlement, transportation and industry. The park contains the Carillon Park Railroad, a 7 1⁄2 in gauge miniature railway. In 2005, Carillon Historical Park merged with the Montgomery County Historical Society to form Dayton History; the Kettering Family Education Center anchors the park and features changing exhibits in the National City Exhibit Gallery, a video about the park, gift and snack shops. There are rooms for education presentations; the John W. Berry Sr. Wright Brothers Aviation Center houses the 1905 Wright Flyer III, the world's first practical airplane; the airplane, a unit of Dayton Aviation Heritage National Historical Park, was restored from 1948 to 1950 with the initial consultation of Orville Wright before his 1948 death.
Newcom Tavern - 1796 home of Col. George Newcom and family, oldest building in Dayton William Morris House - 1815 stone cottage Locust Grove School - 1896 one-room schoolhouse used for over 30 years An original lock of the Miami and Erie Canal is located on the grounds, as is a canal toll office; the transportation center vehicles include the John Quincy Adams steam locomotive, a Barney and Smith passenger car built in Dayton, a Conestoga wagon, a 1908 Stoddard-Dayton automobile, a 1915 Xenia cyclecar, an interurban railcar, other vehicles associated with Dayton. Among the latter, added to the collection in 1988, is a 1949-built Marmon-Herrington trolley bus, number 515 in the fleet of the City Transit Company and provided service on the Dayton trolley bus system from 1949 until about 1982, it arrived at the museum in August 1988 and replaced a similar Marmon-Herrington trolley bus, ex-Dayton 501, on display there since April 1988 but was donated to the Cincinnati Transit Historical Association under an agreement in which Carillon Park received No. 515 from the Miami Valley Regional Transit Authority in exchange.
The center displays the final SUV made at the former General Motors Moraine Assembly, next to the first windshield made by Fuyao Glass America, which redeveloped the factory. Deeds Barn - features such inventions as a Liberty aircraft engine, early Frigidaire refrigerator, 1912 Cadillac with the Delco automobile electric system. Print Shop - working 1930s print shop Corliss Engine Building - houses the Corliss Engine that provided both electrical power and steam heat for the National Cash Register Company from 1902 to 1948; the park is named for the 151-foot-tall Deeds Carillon. Colonel Edward Deeds, in whose name the tower was built, was innovator; the art moderne-style carillon tower was built in 1942 and designed by New York architects Reinhard & Hofmeister. It was funded by Edward Deeds' wife Edith Walton Deeds and was designed to commemorate the Deeds family; when the tower was built, each of 23 bells was inscribed with the name of a family member, with the “silent” bells bearing the names of deceased family members and ringing bells cast with the names of family members living.
Today, with 57 bells, the carillon is Ohio's largest. The National Park Service listed the Deeds Carillon on the National Register of Historic Places in 2005. Carillon Park refurbished the carillon in 1988, converting it from an electric keyboard controlled instrument to a traditional, baton-keyboard mechanical carillon; the Park's carillonneur, Larry Weinstein performs live carillon concerts every Sunday at 3:00 from May to October. The Henry Ford Carillon Historical Park Dayton Aviation Heritage National Historical Park
Ohio is a Midwestern state in the Great Lakes region of the United States. Of the fifty states, it is the 34th largest by area, the seventh most populous, the tenth most densely populated; the state's capital and largest city is Columbus. The state takes its name from the Ohio River, whose name in turn originated from the Seneca word ohiːyo', meaning "good river", "great river" or "large creek". Partitioned from the Northwest Territory, Ohio was the 17th state admitted to the Union on March 1, 1803, the first under the Northwest Ordinance. Ohio is known as the "Buckeye State" after its Ohio buckeye trees, Ohioans are known as "Buckeyes". Ohio rose from the wilderness of Ohio Country west of Appalachia in colonial times through the Northwest Indian Wars as part of the Northwest Territory in the early frontier, to become the first non-colonial free state admitted to the union, to an industrial powerhouse in the 20th century before transmogrifying to a more information and service based economy in the 21st.
The government of Ohio is composed of the executive branch, led by the Governor. Ohio occupies 16 seats in the United States House of Representatives. Ohio is known for its status as both a bellwether in national elections. Six Presidents of the United States have been elected. Ohio is an industrial state, ranking 8th out of 50 states in GDP, is the second largest producer of automobiles behind Michigan. Ohio's geographic location has proven to be an asset for economic expansion; because Ohio links the Northeast to the Midwest, much cargo and business traffic passes through its borders along its well-developed highways. Ohio has the nation's 10th largest highway network and is within a one-day drive of 50% of North America's population and 70% of North America's manufacturing capacity. To the north, Lake Erie gives Ohio 312 miles of coastline. Ohio's southern border is defined by the Ohio River, much of the northern border is defined by Lake Erie. Ohio's neighbors are Pennsylvania to the east, Michigan to the northwest, Lake Erie to the north, Indiana to the west, Kentucky on the south, West Virginia on the southeast.
Ohio's borders were defined by metes and bounds in the Enabling Act of 1802 as follows: Bounded on the east by the Pennsylvania line, on the south by the Ohio River, to the mouth of the Great Miami River, on the west by the line drawn due north from the mouth of the Great Miami aforesaid, on the north by an east and west line drawn through the southerly extreme of Lake Michigan, running east after intersecting the due north line aforesaid, from the mouth of the Great Miami until it shall intersect Lake Erie or the territorial line, thence with the same through Lake Erie to the Pennsylvania line aforesaid. Ohio is bounded by the Ohio River, but nearly all of the river itself belongs to Kentucky and West Virginia. In 1980, the U. S. Supreme Court held that, based on the wording of the cessation of territory by Virginia, the boundary between Ohio and Kentucky is the northern low-water mark of the river as it existed in 1792. Ohio has only that portion of the river between the river's 1792 low-water mark and the present high-water mark.
The border with Michigan has changed, as a result of the Toledo War, to angle northeast to the north shore of the mouth of the Maumee River. Much of Ohio features glaciated till plains, with an exceptionally flat area in the northwest being known as the Great Black Swamp; this glaciated region in the northwest and central state is bordered to the east and southeast first by a belt known as the glaciated Allegheny Plateau, by another belt known as the unglaciated Allegheny Plateau. Most of Ohio is of low relief, but the unglaciated Allegheny Plateau features rugged hills and forests; the rugged southeastern quadrant of Ohio, stretching in an outward bow-like arc along the Ohio River from the West Virginia Panhandle to the outskirts of Cincinnati, forms a distinct socio-economic unit. Geologically similar to parts of West Virginia and southwestern Pennsylvania, this area's coal mining legacy, dependence on small pockets of old manufacturing establishments, distinctive regional dialect set this section off from the rest of the state.
In 1965 the United States Congress passed the Appalachian Regional Development Act, an attempt to "address the persistent poverty and growing economic despair of the Appalachian Region." This act defines 29 Ohio counties as part of Appalachia. While 1/3 of Ohio's land mass is part of the federally defined Appalachian region, only 12.8% of Ohioans live there Significant rivers within the state include the Cuyahoga River, Great Miami River, Maumee River, Muskingum River, Scioto River. The rivers in the northern part of the state drain into the northern Atlantic Ocean via Lake Erie and the St. Lawrence River, the rivers in the southern part of the state drain into the Gulf of Mexico via the Ohio River and the Mississippi; the worst weather disaster in Ohio history occurred along the Great Miami River in 1913. Known as the Great Dayton Flood, the entire Miami River watershed flooded, including the downtown business district of Dayton; as a result, the Miami Conservancy District was created as the first major flood plain engineering project in Ohio and the United States.
Grand Lake St. Marys in the west-central part of the state was constructed as a supply of water for ca
Dayton Aviation Heritage National Historical Park
Dayton Aviation Heritage National Historical Park is a United States National Historical Park in Dayton, United States that commemorates three important historical figures—Wilbur Wright, Orville Wright, poet Paul Laurence Dunbar—and their work in the Miami Valley. The idea for the present-day Dayton Aviation Heritage National Historical Park was first conceived by Jerry Sharkey. Much of the Dayton neighborhood where Orville and Wilbur Wright had lived and worked had been destroyed by the 1970s. Neglect, riots during the 1960s, a highway project through the city had leveled much of the neighborhood. Decades earlier, Henry Ford had relocated one of the Wrights' bicycle shops from Dayton to its present location in Greenfield Village, for display. Sharkey's quest to preserve the Wright brothers' legacy began when he purchased their last surviving bicycle shop in Dayton for just $10,000, which saved the building from demolition, he founded the Aviation Trail Inc. a nonprofit group dedicated to the creation of a potential national park or historic district encompassing the Wright brothers' buildings.
Sharkey enlisted the help of local political and media figures to lobby for the creation of the park. Notable figures who supported its creation included the descendants of the Wright brothers, aviation historian Tom Crouch, U. S. District Judge Walter H. Rice, then-U. S. Rep. Dave Hobson, Dayton Daily News publisher Brad Tillson, Michael Gessel, an aide to former U. S. Rep. Tony P. Hall; the group lobbied federal officials and the National Park Service to incorporate the landmarks related to the Wright brothers, which are scattered throughout the city, into a new historic trail. The U. S. Congress passed legislation to establish the new park. In 1992, President George H. W. Bush signed the bill which created the Dayton Aviation Heritage National Historical Park into law. In addition to the Wright brothers' sites, the new park preserved the home of Paul Laurence Dunbar, an acclaimed African-American poet and friend of the Wright brothers. Jerry Sharkey donated the Wright brothers' bicycle shop, which he had saved from demolition, to the National Park Service as part of the agreement to create the park.
A new visitor center was constructed in 2003 in time for the centennial of the Wright brothers' first flight. Jerry Sharkey, who had first conceived of the future historic park, died in April 2014. Through the invention of powered flight and Orville Wright made significant contributions to human history. In their Dayton, bicycle shops, the Wright brothers, who self-trained in the science and art of aviation and built the world's first power-driven, heavier-than-air machine capable of free and sustained flight; the Wrights perfected their invention during 1904 and 1905 at the Huffman Prairie Flying Field near their hometown of Dayton. Paul Laurence Dunbar achieved national and international acclaim in a literary world, exclusively reserved for whites, producing a body of work that included novels, short stories and over 400 published poems, his work, which reflected much of the African American experience in the United States, contributed to a growing social consciousness and cultural identity for African Americans.
Although he died in 1906, his writings contributed to developments in African American history, such as the Harlem Renaissance and the early Civil Rights Movement. He was a neighbor and lifelong friend of Orville Wright; the park is a cooperative effort between several partners. The sites are: The Wright Cycle Company Complex in Dayton, which includes the Wright Cycle Company building, the Wright-Dunbar Interpretive Center and the Aviation Trail Visitor Center and Museum Huffman Prairie Flying Field and the Huffman Prairie Flying Field Interpretive Center, both located within Wright-Patterson Air Force Base just northeast of Dayton in Fairborn, but operated by the National Park Service and open to the public; the Wright Brothers Aviation Center at Carillon Historical Park in Dayton, operated by Dayton History The Paul Laurence Dunbar State Memorial in Dayton, operated by Dayton History on behalf of the Ohio Historical Society Hawthorn Hill, the 1914-1948 residence of Orville Wright, located just south of Dayton in Oakwood, Ohio.
Dayton Aviation Heritage National Historical Park is located within the National Aviation Heritage Area, an eight-county region in Ohio established as a National Heritage Area by Congress in 2004. The U. S. Department of the Interior listed three units of the park on the 2008 U. S. World Heritage Tentative List as part of the Dayton Aviation Sites listing; the park is a central component of the National Aviation Heritage Area. Wright Brothers National Memorial in Kitty Hawk, North Carolina Official NPS Site 2008 U. S. World Heritage Tentative List Report, with section on the Dayton Aviation Sites Dayton Aviation Heritage National Historical Park: Where the Wright Brothers Conquered the Air, a National Park Service Teaching with Historic Places lesson plan Aviation: From Sand Dunes to Sonic Booms, a National Park Service Discover Our Shared Heritage Travel Itinerary Carillon Park - home of the 1905 Wright Flyer III Ohio Historical Society site for the Paul Laurence Dunbar State Memorial
In aerodynamics, wing loading is the total weight of an aircraft divided by the area of its wing. The stalling speed of an aircraft in straight, level flight is determined by its wing loading. An aircraft with a low wing loading has a larger wing area relative to its mass, as compared to an aircraft with a high wing loading; the faster an aircraft flies, the more lift can be produced by each unit of wing area, so a smaller wing can carry the same mass in level flight. Faster aircraft have higher wing loadings than slower aircraft; this increased wing loading increases takeoff and landing distances. A higher wing loading decreases maneuverability; the same constraints apply to winged biological organisms. Wing loading is a useful measure of the stalling speed of an aircraft. Wings generate lift owing to the motion of air around the wing. Larger wings move more air, so an aircraft with a large wing area relative to its mass will have a lower stalling speed. Therefore, an aircraft with lower wing loading will be able to land at a lower speed.
It will be able to turn at a greater rate. The lift force L on a wing of area A, traveling at true airspeed v is given by L = 1 2 ρ v 2 A C L, where ρ is the density of air and CL is the lift coefficient; the lift coefficient is a dimensionless number which depends on the wing cross-sectional profile and the angle of attack. At take-off or in steady flight, neither climbing nor diving, the lift force and the weight are equal. With L/A = Mg/A =WSg, where M is the aircraft mass, WS = M/A the wing loading and g the acceleration due to gravity, that equation gives the speed v through v 2 = 2 g W S ρ C L; as a consequence, aircraft with the same CL at takeoff under the same atmospheric conditions will have takeoff speeds proportional to W S. So if an aircraft's wing area is increased by 10% and nothing else is changed, the takeoff speed will fall by about 5%. If an aircraft designed to take off at 150 mph grows in weight during development by 40%, its takeoff speed increases to 150 1.4 = 177 mph. Some flyers rely on their muscle power to gain speed for takeoff over water.
Ground nesting and water birds have to be able to run or paddle at their takeoff speed before they can take off. The same is true for a hang glider pilot. For all these, a low WS is critical, whereas passerines and cliff dwelling birds can get airborne with higher wing loadings. To turn, an aircraft must roll in the direction of the turn. Turning flight hence causes a descent. To compensate, the lift force must be increased by increasing the angle of attack by use of up elevator deflection which increases drag. Turning can be described as'climbing around a circle' so the increase in wing angle of attack creates more drag; the tighter the turn radius attempted, the more drag induced, this requires that power be added to overcome the drag. The maximum rate of turn possible for a given aircraft design is limited by its wing size and available engine power: the maximum turn the aircraft can achieve and hold is its sustained turn performance; as the bank angle increases so does the g-force applied to the aircraft, this having the effect of increasing the wing loading and the stalling speed.
This effect is experienced during level pitching maneuvers. As stalling is due to wing loading and maximum lift coefficient at a given altitude and speed, this limits the turning radius due to maximum load factor. At Mach 0.85 and 0.7 lift coefficient, a wing loading of 50 lb/sq ft can reach a structural limit of 7.33 g up to 15,000 feet and decreases to 2.3 g at 40,000 feet while with a wing loading of 100 lb/sq ft the load factor is twice smaller and reach 1g at 40,000 feet. Aircraft with low wing loadings tend to have superior sustained turn performance because they can generate more lift for a given quantity of engine thrust; the immediate bank angle an aircraft can achieve before drag bleeds off airspeed is known as its instantaneous turn performance. An aircraft with a small loaded wing may have superior instantaneous turn performance, but poor sustained turn performance: it reacts to control input, but its ability to sustain a tight turn is limited. A classic example is the F-104 Starfighter, which has a small wing and high 723 kg/m2 wing loading.
At the opposite end of the spectrum was the large Convair B-36: its large wings resulted in a low 269 kg/m2 wing loading that could make it sustain tighter turns at high altitude than contemporary jet fighters, while the later Hawker Hunter had a similar wing loading of 344 kg/m2. The Boeing 367-80 airliner prototype could be rolled at low altitudes with a wing loading of 387 kg/m2 at maximum weight. Like any body in circular motion, an aircraft, fast and strong enough to maintain level flight at speed v in a circle of radius R accelerates towards the center
United States Secretary of War
The Secretary of War was a member of the United States President's Cabinet, beginning with George Washington's administration. A similar position, called either "Secretary at War" or "Secretary of War", had been appointed to serve the Congress of the Confederation under the Articles of Confederation between 1781 and 1789. Benjamin Lincoln and Henry Knox held the position; when Washington was inaugurated as the first president under the Constitution, he appointed Knox to continue serving as Secretary of War. The Secretary of War was the head of the War Department. At first, he was responsible including naval affairs. In 1798, the Secretary of the Navy was created by statute, the scope of responsibility for this office was reduced to the affairs of the United States Army. From 1886 onward, the Secretary of War was in the line of succession to the presidency, after the Vice President of the United States, the Speaker of the House of Representatives, the President pro tem of the Senate and the Secretary of State.
In 1947, with the passing of the National Security Act of 1947, the Secretary of War was replaced by the Secretary of the Army and the Secretary of the Air Force, along with the Secretary of the Navy, have since 1949 been non-Cabinet subordinates under the Secretary of Defense. The Secretary of the Army's office is considered the direct successor to the Secretary of War's office although the Secretary of Defense took the Secretary of War's position in the Cabinet, the line of succession to the presidency; the office of Secretary at War was modelled upon Great Britain's Secretary at War, William Barrington, 2nd Viscount Barrington, at the time of the American Revolution. The office of Secretary at War was meant to replace both the Commander-in-Chief and the Board of War, like the President of the Board, the Secretary wore no special insignia; the Inspector General, Quartermaster General, Commissary General, Adjutant General served on the Secretary's staff. However, the Army itself under Secretary Henry Knox only consisted of 700 men.
Parties No party Federalist Democratic-Republican Democratic Whig Republican Confederate States Secretary of War Bell, William Gardner. Commanding Generals and Chiefs of Staff 1775-2005: Portraits and Biographical Sketches. Washington, D. C.: United States Army Center of Military History. Grossman, Mark. Encyclopedia of the United States Cabinet 1789-2010. Armenia, New York: Greyhouse Publishing. King, Archibald. Command of the Army. Military Affairs. Charlottesville, Virginia: The Judge Advocate General's School, U. S. Army
A wing is a type of fin that produces lift, while moving through air or some other fluid. As such, wings have streamlined cross-sections that are subject to aerodynamic forces and act as an airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio; the lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a smaller thrust to propel the wings through the air at sufficient lift. Lifting structures include various foils, including hydrofoils. Hydrodynamics is the governing science, rather than aerodynamics. Applications of underwater foils occur in hydroplanes and submarines; the word "wing" from the Old Norse vængr for many centuries referred to the foremost limbs of birds. But in recent centuries the word's meaning has extended to include lift producing appendages of insects, pterosaurs, some sail boats and aircraft, or the inverted airfoil on a race car that generates a downward force to increase traction.
The design and analysis of the wings of aircraft is one of the principal applications of the science of aerodynamics, a branch of fluid mechanics. The properties of the airflow around any moving object can – in principle – be found by solving the Navier-Stokes equations of fluid dynamics. However, except for simple geometries these equations are notoriously difficult to solve. However, simpler explanations can be described. For a wing to produce "lift", it must be oriented at a suitable angle of attack relative to the flow of air past the wing; when this occurs the wing deflects the airflow downwards. Since the wing exerts a force on the air to change its direction, the air must exert a force on the wing, equal in size but opposite in direction; this force manifests itself as differing air pressures at different points on the surface of the wing. A region of lower-than-normal air pressure is generated over the top surface of the wing, with a higher pressure on the bottom of the wing; these air pressure differences can be either measured directly using instrumentation, or can be calculated from the airspeed distribution using basic physical principles—including Bernoulli's principle, which relates changes in air speed to changes in air pressure.
The lower air pressure on the top of the wing generates a smaller downward force on the top of the wing than the upward force generated by the higher air pressure on the bottom of the wing. Hence, a net upward force acts on the wing; this force is called the "lift" generated by the wing. The different velocities of the air passing by the wing, the air pressure differences, the change in direction of the airflow, the lift on the wing are intrinsically one phenomenon, it is, possible to calculate lift from any of the other three. For example, the lift can be calculated from the pressure differences, or from different velocities of the air above and below the wing, or from the total momentum change of the deflected air. Fluid dynamics offers other approaches to solving these problems—and all produce the same answers if done correctly. Given a particular wing and its velocity through the air, debates over which mathematical approach is the most convenient to use can be mistaken by novices as differences of opinion about the basic principles of flight.
An airfoil or aerofoil is the shape of blade, or sail. Wings with an asymmetrical cross section are the norm in subsonic flight. Wings with a symmetrical cross section can generate lift by using a positive angle of attack to deflect air downward. Symmetrical airfoils have higher stalling speeds than cambered airfoils of the same wing area but are used in aerobatic aircraft as they provide practical performance whether the aircraft is upright or inverted. Another example comes from sailboats, where the sail is a thin membrane with no path-length difference between one side and the other. For flight speeds near the speed of sound, airfoils with complex asymmetrical shapes are used to minimize the drastic increase in drag associated with airflow near the speed of sound; such airfoils, called supercritical airfoils, are flat on top and curved on the bottom. Aircraft wings may feature some of the following: A rounded leading edge cross-section A sharp trailing edge cross-section Leading-edge devices such as slats, slots, or extensions Trailing-edge devices such as flaps or flaperons Winglets to keep wingtip vortices from increasing drag and decreasing lift Dihedral, or a positive wing angle to the horizontal, increases spiral stability around the roll axis, whereas anhedral, or a negative wing angle to the horizontal, decreases spiral stability.
Aircraft wings may have various devices, such as flaps or slats that the pilot uses to modify the shape and surface area of the wing to change its operating characteristics in flight. Ailerons to roll the aircraft clockwise or counterclockwise about its long axis Spoilers on the upper surface to disrupt the lift and to provide additional traction to an aircraft that has just landed but is still moving. Vortex generators to help prevent flow separation in transonic flow Wing fences to keep flow attached to the wing by stopping boundary layer separation from spreading roll direction. Folding wings allow more aircraft storage in the confined space of the hangar deck of an aircraft carrier Variable-sweep wing or "swing wings" that allow outstretched wings during low-speed flight and swept back wings for high-speed flight (includin