Distance is a numerical measurement of how far apart objects are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria. In most cases, "distance from A to B" is interchangeable with "distance from B to A". In mathematics, a distance function or metric is a generalization of the concept of physical distance. A metric is a function that behaves according to a specific set of rules, is a way of describing what it means for elements of some space to be "close to" or "far away from" each other. A physical distance can mean several different things: Distance Traveled: The length of a specific path traveled between two points, such as the distance walked while navigating a maze Straight-Line Distance: The length of the shortest possible path through space, between two points, that could be taken if there were no obstacles Geodesic Distance: The length of the shortest path between two points while remaining on some surface, such as the great-circle distance along the curve of the Earth The length of a specific path that returns to the starting point, such as a ball thrown straight up, or the Earth when it completes one orbit.
"Circular distance" is the distance traveled by a wheel, which can be useful when designing vehicles or mechanical gears. The circumference of the wheel is 2π × radius, assuming the radius to be 1 each revolution of the wheel is equivalent of the distance 2π radians. In engineering ω = 2πƒ is used, where ƒ is the frequency. Unusual definitions of distance can be helpful to model certain physical situations, but are used in theoretical mathematics: "Manhattan distance" is a rectilinear distance, named after the number of blocks north, east, or west a taxicab must travel on to reach its destination on the grid of streets in parts of New York City. "Chessboard distance", formalized as Chebyshev distance, is the minimum number of moves a king must make on a chessboard to travel between two squares. Distance measures in cosmology are complicated by the expansion of the universe, by effects described by the theory of relativity such as length contraction of moving objects; the term "distance" is used by analogy to measure non-physical entities in certain ways.
In computer science, there is the notion of the "edit distance" between two strings. For example, the words "dog" and "dot", which vary by only one letter, are closer than "dog" and "cat", which differ by three letters; this idea is used in spell checkers and in coding theory, is mathematically formalized in several different ways, such as: Levenshtein distance Hamming distance Lee distance Jaro–Winkler distanceIn mathematics, a metric space is a set for which distances between all members of the set are defined. In this way, many different types of "distances" can be calculated, such as for traversal of graphs, comparison of distributions and curves, using unusual definitions of "space"; the notion of distance in graph theory has been used to describe social networks, for example with the Erdős number or the Bacon number, the number of collaborative relationships away a person is from prolific mathematician Paul Erdős or actor Kevin Bacon, respectively. In psychology, human geography, the social sciences, distance is theorized not as an objective metric, but as a subjective experience.
Both distance and displacement measure the movement of an object. Distance cannot be negative, never decreases. Distance is a magnitude. Whereas displacement is a vector quantity with both direction, it can be zero, or positive. Directed distance does not measure movement, it measures the separation of two points, can be a positive, zero, or negative vector; the distance covered by a vehicle, animal, or object along a curved path from a point A to a point B should be distinguished from the straight-line distance from A to B. For example, whatever the distance covered during a round trip from A to B and back to A, the displacement is zero as start and end points coincide. In general the straight-line distance does not equal distance travelled, except for journeys in a straight line. Directed distances can be determined along curved lines. Directed distances along straight lines are vectors that give the distance and direction between a starting point and an ending point. A directed distance of a point C from point A in the direction of B on a line AB in a Euclidean vector space is the distance from A to C if C falls on the ray AB, but is the negative of that distance if C falls on the ray BA.
For example, the directed distance from the New York City Main Library flag pole to the Statue of Liberty flag pole has: a starting point: library flag pole an ending point: statue flag pole a direction: -38° a distance: 8.72 kmAnother kind of directed distance is that between two different particles or point masses at a given time. For instance, the distance from the center of gravity of the Earth A and the center of gravity of the Moon B falls into this category. A directed distance along a curved line is not a vector and is represented by a segment of that curved line defined by endpoints A and B, with some specific information indicating the sense of an ideal or real motion from one endpoint of the segment to the other. For instance, just labelling the two endpoints as A and B can indicate the sense, if the ordered sequence is assumed, which implies that A is the starting point. A displacement is a special kind of directed distance def
In everyday use and in kinematics, the speed of an object is the magnitude of its velocity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval. Speed has the dimensions of distance divided by time; the SI unit of speed is the metre per second, but the most common unit of speed in everyday usage is the kilometre per hour or, in the US and the UK, miles per hour. For air and marine travel the knot is used; the fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 299792458 metres per second. Matter can not quite reach the speed of light. In relativity physics, the concept of rapidity replaces the classical idea of speed. Italian physicist Galileo Galilei is credited with being the first to measure speed by considering the distance covered and the time it takes. Galileo defined speed as the distance covered per unit of time. In equation form, v = d t, where v is speed, d is distance, t is time.
A cyclist who covers 30 metres in a time of 2 seconds, for example, has a speed of 15 metres per second. Objects in motion have variations in speed. Speed at some instant, or assumed constant during a short period of time, is called instantaneous speed. By looking at a speedometer, one can read the instantaneous speed of a car at any instant. A car travelling at 50 km/h goes for less than one hour at a constant speed, but if it did go at that speed for a full hour, it would travel 50 km. If the vehicle continued at that speed for half an hour, it would cover half that distance. If it continued for only one minute, it would cover about 833 m. In mathematical terms, the instantaneous speed v is defined as the magnitude of the instantaneous velocity v, that is, the derivative of the position r with respect to time: v = | v | = | r ˙ | = | d r d t |. If s is the length of the path travelled until time t, the speed equals the time derivative of s: v = d s d t. In the special case where the velocity is constant, this can be simplified to v = s / t.
The average speed over a finite time interval is the total distance travelled divided by the time duration. Different from instantaneous speed, average speed is defined as the total distance covered divided by the time interval. For example, if a distance of 80 kilometres is driven in 1 hour, the average speed is 80 kilometres per hour. If 320 kilometres are travelled in 4 hours, the average speed is 80 kilometres per hour; when a distance in kilometres is divided by a time in hours, the result is in kilometres per hour. Average speed does not describe the speed variations that may have taken place during shorter time intervals, so average speed is quite different from a value of instantaneous speed. If the average speed and the time of travel are known, the distance travelled can be calculated by rearranging the definition to d = v ¯ t. Using this equation for an average speed of 80 kilometres per hour on a 4-hour trip, the distance covered is found to be 320 kilometres. Expressed in graphical language, the slope of a tangent line at any point of a distance-time graph is the instantaneous speed at this point, while the slope of a chord line of the same graph is the average speed during the time interval covered by the chord.
Average speed of an object is Vav = s÷t Linear speed is the distance travelled per unit of time, while tangential speed is the linear speed of something moving along a circular path. A point on the outside edge of a merry-go-round or turntable travels a greater distance in one complete rotation than a point nearer the center. Travelling a greater distance in the same time means a greater speed, so linear speed is greater on the outer edge of a rotating object than it is closer to the axis; this speed along a circular path is known as tangential speed because the direction of motion is tangent to the circumference of the circle. For circular motion, the terms linear speed and tangential speed are used interchangeably, both use units of m/s, km/h, others. Rotational speed involves the number of revolutions per unit of time. All parts of a rigid merry-
In mechanics, an impact is a high force or shock applied over a short time period when two or more bodies collide. Such a force or acceleration has a greater effect than a lower force applied over a proportionally longer period; the effect depends critically on the relative velocity of the bodies to one another. At normal speeds, during a inelastic collision, an object struck by a projectile will deform, this deformation will absorb most or all of the force of the collision. Viewed from a conservation of energy perspective, the kinetic energy of the projectile is changed into heat and sound energy, as a result of the deformations and vibrations induced in the struck object. However, these deformations and vibrations cannot occur instantaneously. A high-velocity collision does not provide sufficient time for these deformations and vibrations to occur. Thus, the struck material behaves as if it were more brittle than it would otherwise be, the majority of the applied force goes into fracturing the material.
Or, another way to look at it is that materials are more brittle on short time scales than on long time scales: this is related to time-temperature superposition. Impact resistance decreases with an increase in the modulus of elasticity, which means that stiffer materials will have less impact resistance. Resilient materials will have better impact resistance. Different materials can behave in quite different ways in impact when compared with static loading conditions. Ductile materials like steel tend to become more brittle at high loading rates, spalling may occur on the reverse side to the impact if penetration doesn't occur; the way in which the kinetic energy is distributed through the section is important in determining its response. Projectiles apply a Hertzian contact stress at the point of impact to a solid body, with compression stresses under the point, but with bending loads a short distance away. Since most materials are weaker in tension than compression, this is the zone where cracks tend to form and grow.
A nail is pounded with a series of impacts, each by a single hammer blow. These high velocity impacts overcome the static friction between the substrate. A pile driver achieves the same end, although on a much larger scale, the method being used during civil construction projects to make building and bridge foundations. An impact wrench is a device designed to impart torque impacts to bolts to loosen them. At normal speeds, the forces applied to the bolt would be dispersed, via friction, to the mating threads. However, at impact speeds, the forces act on the bolt to move it. In ballistics, bullets utilize impact forces to puncture surfaces that could otherwise resist substantial forces. A rubber sheet, for example, behaves more like glass at typical bullet speeds; that is, it fractures, does not stretch or vibrate. Road traffic accidents involve impact loading, such as when a car hits a traffic bollard, water hydrant or tree, the damage being localized to the impact zone; when vehicles collide, the damage increases with the relative velocity of the vehicles, the damage increasing as the square of the velocity since it is the impact kinetic energy, the variable of importance.
Much design effort is made to improve the impact resistance of cars so as to minimize user injury. It can be achieved in several ways: by enclosing the driver and passengers in a safety cell for example; the cell is reinforced so it will survive in high speed crashes, so protect the users. Parts of the body shell outside the cell are designed to crumple progressively, absorbing most of the kinetic energy which must be dissipated by the impact. Various impact test are used to assess the effects of high loading, both on products and standard slabs of material; the Charpy test and Izod test are two examples of standardized methods which are used for testing materials. Ball or projectile drop tests are used for assessing product impacts; the Columbia disaster was caused by impact damage when a chunk of polyurethane foam impacted the carbon fibre composite wing of the space shuttle. Although tests had been conducted before the disaster, the test chunks were much smaller than the chunk that fell away from the booster rocket and hit the exposed wing.
When fragile items are shipped and drops can cause product damage. Protective packaging and cushioning help reduce the peak acceleration by extending the duration of the shock or impact. Coefficient of restitution Fall factor Compression Tension Impulse Charpy impact test Cushioning Izod impact strength test Shock Impact sensor Shock data logger Jerk Write-off Road traffic accident Goldsmith, W.. Impact: The Theory and Physical Behaviour of Colliding Solids Dover Publications, ISBN 0-486-42004-3 Poursartip, A.. Instrumented Impact Testing at High Velocities, Journal of Composites Technology and Research, 15. Toropov, AI.. Dynamic Calibration of Impact Test Instruments, Journal of Testing and Evaluation, 24
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag. Parachutes are made out of light, strong fabric silk, now most nylon, they are dome-shaped, but vary, with rectangles, inverted domes, others found. A variety of loads are attached to parachutes, including people, equipment, space capsules, bombs. A drogue chute is used to aid horizontal deceleration of a vehicle including fixed-wing aircraft and drag racers, provide stability, as to assist certain types of light aircraft in distress, tandem free-fall; the earliest fictional account of a parachute type of device was made some 4,000 years ago when the Chinese noticed that air resistance would slow a person's fall from a height. The Western Han Dynasty writer Sima Qian in his book Historical Records recounts the story of Shun, a legendary Chinese emperor who ran away from his murderous father by climbing onto the top of a high granary; as there was nowhere to go, Shun grabbed two bamboo hats and leaped off and glided downward to safety.
The earliest evidence for the modern parachute dates back to the Renaissance period. The oldest parachute design appears in an anonymous manuscript from 1470s Renaissance Italy, showing a free-hanging man clutching a crossbar frame attached to a conical canopy; as a safety measure, four straps ran from the ends of the rods to a waist belt, marked improvement over another folio, which depicts a man trying to break the force of his fall by the means of two long cloth streamers fastened to two bars which he grips with his hands. Although the surface area of the first design appears to be too small to be effective and the wooden frame is superfluous and harmful, the basic concept of a working parachute is apparent. Shortly after, a more sophisticated parachute was sketched by the polymath Leonardo da Vinci in his Codex Atlanticus dated to ca. 1485. Here, the scale of the parachute is in a more favorable proportion to the weight of the jumper. Leonardo's canopy was held open by a square wooden frame, which alters the shape of the parachute from conical to pyramidal.
It is not known whether the Italian inventor was influenced by the earlier design, but he may have learned about the idea through the intensive oral communication among artist-engineers of the time. The feasibility of Leonardo's pyramidal design was tested in 2000 by Briton Adrian Nicholas and again in 2008 by the Swiss skydiver Olivier Vietti-Teppa. According to the historian of technology Lynn White, these conical and pyramidal designs, much more elaborate than early artistic jumps with rigid parasols in Asia, mark the origin of "the parachute as we know it." The Dalmatian polymath and inventor Fausto Veranzio examined da Vinci's parachute sketch and kept the square frame but replaced the canopy with a bulging sail-like piece of cloth that he came to realize decelerates a fall more effectively. A now-famous depiction of a parachute that he dubbed Homo Volans, showing a man parachuting from a tower St Mark's Campanile in Venice, appeared in his book on mechanics, Machinae Novae, alongside a number of other devices and technical concepts.
It was once believed that in 1617, Veranzio aged 65 and ill, implemented his design and tested the parachute by jumping from St Mark's Campanile, from a bridge nearby, or from St Martin's Cathedral in Bratislava. In various publications it was incorrectly claimed the event was documented some thirty years by John Wilkins and secretary of the Royal Society in London, in his book Mathematical Magick or, the Wonders that may be Performed by Mechanical Geometry, published in London in 1648. However, Wilkins wrote about flying, not parachutes, does not mention Veranzio, a parachute jump, or any event in 1617. Doubts about this test, which include a lack of written evidence, suggest it never occurred, was instead a misreading of historical notes; the modern parachute was invented in the late 18th century by Louis-Sébastien Lenormand in France, who made the first recorded public jump in 1783. Lenormand sketched his device beforehand. Two years in 1785, Lenormand coined the word "parachute" by hybridizing an Italian prefix para, an imperative form of parare = to avert, resist, shield or shroud, from paro = to parry, chute, the French word for fall, to describe the aeronautical device's real function.
In 1785, Jean-Pierre Blanchard demonstrated it as a means of safely disembarking from a hot-air balloon. While Blanchard's first parachute demonstrations were conducted with a dog as the passenger, he claimed to have had the opportunity to try it himself in 1793 when his hot air balloon ruptured and he used a parachute to descend. Subsequent development of the parachute focused on it becoming more compact. While the early parachutes were made of linen stretched over a wooden frame, in the late 1790s, Blanchard began making parachutes from folded silk, taking advantage of silk's strength and light weight. In 1797, André Garnerin made the first descent of a "frameless" parachute covered in silk. In 1804 Jérôme Lalande introduced a vent in the canopy to eliminate violent oscillations. In 1907 Charles Broadwick demonstrated two key advances in the parachute he used to jump from hot air balloons at fairs: he folded his parachute into a pack he wore on his back and the parachute was pulled from the pack by a static line attached to the balloon.
When Broadwick jumped from the balloon, the static line became taut, pulled th
An aircraft pilot or aviator is a person who controls the flight of an aircraft by operating its directional flight controls. Some other aircrew members, such as navigators or flight engineers, are considered aviators, because they are involved in operating the aircraft's navigation and engine systems. Other aircrew members, such as flight attendants and ground crew, are not classified as aviators. In recognition of the pilots' qualifications and responsibilities, most militaries and many airlines worldwide award aviator badges to their pilots; the first recorded use of the term aviator was in 1887, as a variation of "aviation", from the Latin avis, coined in 1863 by G. de la Landelle in Aviation Ou Navigation Aérienne. The term aviatrix, now archaic, was used for a female aviator; these terms were used more in the early days of aviation, when airplanes were rare, connoted bravery and adventure. For example, a 1905 reference work described the Wright brothers' first airplane: "The weight, including the body of the aviator, is a little more than 700 pounds".
To ensure the safety of people in the air and on the ground, early aviation soon required that aircraft be under the operational control of a properly trained, certified pilot at all times, responsible for the safe and legal completion of the flight. The Aéro-Club de France delivered the first certificate to Louis Blériot in 1908—followed by Glenn Curtiss, Léon Delagrange, Robert Esnault-Pelterie; the British Royal Aero Club followed in 1910 and the Aero Club of America in 1911. Civilian pilots fly aircraft of all types for pleasure, charity, or in pursuance of a business, or commercially for non-scheduled and scheduled passenger and cargo air carriers, corporate aviation, forest fire control, law enforcement, etc; when flying for an airline, pilots are referred to as airline pilots, with the pilot in command referred to as the captain. There are 290,000 airline pilots in the world in 2017 and aircraft simulator manufacturer CAE Inc. forecasts a need for 255,000 new ones for a population of 440,000 by 2027, 150,000 for growth and 105,000 to offset retirement and attrition: 90,000 in Asia-Pacific, 85,000 in Americas, 50,000 in Europe and 30,000 in Middle East & Africa.
Boeing expects 790,000 new pilots in 20 years from 2018, 635,000 for commercial aviation, 96,000 for business aviation and 59,000 for helicopters: 33% in Asia Pacific, 26% in North America, 18% in Europe, 8% in the Middle East, 7% in Latin America, 4% in Africa and 3% in Russia/ Central Asia. By November 2017, due a shortage of qualified pilots, some pilots are leaving corporate aviation to return to airlines. In one example a Global 6000 pilot, making $250,000 a year for 10 to 15 flight hours a month, returned to American Airlines with full seniority. A Gulfstream G650 or Global 6000 pilot might earn between $245,000 and $265,000, recruiting one may require up to $300,000. At the other end of the spectrum, constrained by the available pilots, some small carriers hire new pilots who need 300 hours to jump to airlines in a year, they may recruit non-career pilots who have other jobs or airline retirees who want to continue to fly. The number of airline pilots could decrease as automation replaces copilots and pilots as well.
In January 2017 Rhett Ross, CEO of Continental Motors said "my concern is that in the next two decades—if not sooner—automated and autonomous flight will have developed sufficiently to put downward pressure on both wages and the number and kind of flying jobs available. So if a kid asks the question now and he or she is 18, 20 years from now will be 2037 and our would-be careerist will be 38—not mid-career. Who among us thinks aviation and for-hire flying will look like it does now?" Christian Dries, owner of Diamond Aircraft Austria said "Behind the curtain, aircraft manufacturers are working on a single-pilot cockpit where the airplane can be controlled from the ground and only in case of malfunction does the pilot of the plane interfere. The flight will be autonomous and I expect this to happen in the next five to six years for freighters."In August 2017 financial company UBS predicted pilotless airliners are technically feasible and could appear around 2025, offering around $35bn of savings in pilot costs: $26bn for airlines, $3bn for business jets and $2.1bn for civil helicopters.
Regulations have to adapt with air cargo at the forefront, but pilotless flights could be limited by consumer behaviour: 54% of 8,000 people surveyed are defiant while 17% are supportive, with acceptation progressively forecast. AVweb reporter Geoff Rapoport stated, "pilotless aircraft are an appealing prospect for airlines bracing for the need to hire several hundred thousand new pilots in the next decade. Wages and training costs have been rising at regional U. S. airlines over the last several years as the major airlines have hired pilots from the regionals at unprecedented rates to cover increased air travel demand from economic expansion and a wave of retirements". Going to pilotless airliners could be done in one bold step or in gradual improvements like by reducing the cockpit crew for long haul missions or allowing single pilot cargo aircraft; the industry has not decided
In navigation, the course of a vessel or aircraft is the cardinal direction in which the craft is to be steered. The course is to be distinguished from the heading, the compass direction in which the craft's bow or nose is pointed; the path that a vessel follows over the ground is called a ground track, course made good or course over the ground. For an aircraft it is its track; the intended track is a route. For ships and aircraft, routes are straight-line segments between waypoints. A navigator determines the bearing of the next waypoint; because water currents or wind can cause a craft to drift off course, a navigator sets a course to steer that compensates for drift. The helmsman or pilot points the craft on a heading. If the predicted drift is correct the craft's track will correspond to the planned course to the next waypoint. Course directions are specified in degrees from north, either magnetic. In aviation, north is expressed as 360°. Navigators used ordinal directions, instead of compass degrees, e.g. "northeast" instead of 45° until the mid-20th century when the use of degrees became prevalent.
Acronyms and abbreviations in avionics Bearing Breton plotter E6B Ground track Navigation Navigation room Rhumb line Pilot's Handbook of Aeronautical Knowledge glossary
Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure. The pilot sits in a harness suspended below a fabric wing. Wing shape is maintained by the suspension lines, the pressure of air entering vents in the front of the wing, the aerodynamic forces of the air flowing over the outside. Despite not using an engine, paraglider flights can last many hours and cover many hundreds of kilometres, though flights of one to two hours and covering some tens of kilometres are more the norm. By skillful exploitation of sources of lift, the pilot may gain height climbing to altitudes of a few thousand metres. In 1952 Canadian Domina Jalbert patented a governable gliding parachute with multi-cells and controls for lateral glide. In 1954, Walter Neumark predicted a time when a glider pilot would be "able to launch himself by running over the edge of a cliff or down a slope... whether on a rock-climbing holiday in Skye or ski-ing in the Alps."In 1961, the French engineer Pierre Lemongine produced improved parachute designs that led to the Para-Commander.
The PC had cutouts at the rear and sides that enabled it to be towed into the air and steered, leading to parasailing/parascending. Domina Jalbert invented the Parafoil, he filed US Patent 3131894 on January 10, 1963. About that time, David Barish was developing the "sail wing" for recovery of NASA space capsules – "slope soaring was a way of testing out... the Sail Wing." After tests on Hunter Mountain, New York, in September 1965, he went on to promote slope soaring as a summer activity for ski resorts. Author Walter Neumark wrote Operating Procedures for Ascending Parachutes, in 1973 he and a group of enthusiasts with a passion for tow-launching PCs and ram-air parachutes broke away from the British Parachute Association to form the British Association of Parascending Clubs. In 1997, Neumark was awarded the Gold Medal of the Royal Aero Club of the UK. Authors Patrick Gilligan and Bertrand Dubuis wrote the first flight manual, The Paragliding Manual in 1985, coining the word paragliding; these developments were combined in June 1978 by three friends, Jean-Claude Bétemps, André Bohn and Gérard Bosson, from Mieussy, Haute-Savoie, France.
After inspiration from an article on slope soaring in the Parachute Manual magazine by parachutist and publisher Dan Poynter, they calculated that on a suitable slope, a "square" ram-air parachute could be inflated by running down the slope. Bohn glided down to the football pitch in the valley 1000 metres below. "Parapente" was born. From the 1980s, equipment has continued to improve, the number of paragliding pilots and established sites has continued to increase; the first Paragliding World Championship was held in Verbier, Switzerland, in 1987, though the first sanctioned FAI World Paragliding Championship was held in Kössen, Austria, in 1989. Europe has seen the greatest growth in paragliding, with France alone registering in 2011 over 25,000 active pilots; the paraglider wing or canopy is what is known in engineering as a "ram-air airfoil". Such wings comprise two layers of fabric that are connected to internal supporting material in such a way as to form a row of cells. By leaving most of the cells open only at the leading edge, incoming air keeps the wing inflated, thus maintaining its shape.
When inflated, the wing's cross-section has the typical teardrop aerofoil shape. Modern paraglider wings are made of high-performance non-porous materials such as ripstop polyester or nylon fabric. In some modern paragliders higher-performance wings, some of the cells of the leading edge are closed to form a cleaner aerodynamic profile. Holes in the internal ribs allow a free flow of air from the open cells to these closed cells to inflate them, to the wingtips, which are closed; the pilot is supported underneath the wing by a network of suspension lines. These start with two sets of risers made of short lengths of strong webbing; each set is attached to the harness by a carabiner, one on each side of the pilot, each riser of a set is attached to lines from only one row of its side of wing. At the end of each riser of the set, there is a small delta maillon with a number of lines attached, forming a fan; these are 4 – 5 metres long, with the end attached to 2 − 4 further lines of around 2 m, which are again joined to a group of smaller, thinner lines.
In some cases this is repeated for a fourth cascade. The top of each line is attached to small fabric loops sewn into the structure of the wing, which are arranged in rows running span-wise; the row of lines nearest the front are known as the A lines, the next row back the B lines, so on. A typical wing will have A, B, C and D lines, but there has been a tendency to reduce the rows of lines to three, or two, to reduce drag. Paraglider lines are made from Dyneema/Spectra or Kevlar/Aramid. Although they look rather slender, these materials are immensely strong. For example, a single 0.66 mm-diameter line can have a breaking strength of 56 kg. Paraglider wings have an area of 20–35 square metres with a span of 8–12 metres and weigh 3–7 kilograms