A kite is a tethered heavier-than-air craft with wing surfaces that react against the air to create lift and drag. A kite consists of wings and anchors. Kites have a bridle and tail to guide the face of the kite so the wind can lift it; some kite designs don’t need a bridle. A kite may have fixed or moving anchors. One technical definition is that a kite is “a collection of tether-coupled wing sets“; the lift that sustains the kite in flight is generated when air moves around the kite's surface, producing low pressure above and high pressure below the wings. The interaction with the wind generates horizontal drag along the direction of the wind; the resultant force vector from the lift and drag force components is opposed by the tension of one or more of the lines or tethers to which the kite is attached. The anchor point of the kite line may be moving; the same principles of fluid flow apply in liquids, so kites can be used in underwater currents, but there are no everyday uses as yet. Man-lifting kites were made for reconnaissance and during development of the first practical aircraft, the biplane.
Kites have a long and varied history and many different types are flown individually and at festivals worldwide. Kites may be flown for art or other practical uses. Sport kites can be flown in aerial ballet, sometimes as part of a competition. Power kites are multi-line steerable kites designed to generate large forces which can be used to power activities such as kite surfing, kite landboarding, kite fishing, kite buggying and snow kiting. Kites were invented in Asia. Many early sources point to China. In China, materials ideal for kite building were available including silk fabric for sail material; the kite has been claimed as the invention of the 5th-century BC Chinese philosophers Mozi and Lu Ban. By 549 AD paper kites were being flown, as it was recorded that in that year a paper kite was used as a message for a rescue mission. Ancient and medieval Chinese sources describe kites being used for measuring distances, testing the wind, lifting men and communication for military operations; the earliest known Chinese kites were flat and rectangular.
Tailless kites incorporated a stabilizing bowline. Kites were decorated with legendary figures. After its introduction into India, the kite further evolved into the fighter kite, known as the patang in India, where thousands are flown every year on festivals such as Makar Sankranti. Kites were known throughout Polynesia, as far as New Zealand, with the assumption being that the knowledge diffused from China along with the people. Anthropomorphic kites made from cloth and wood were used in religious ceremonies to send prayers to the gods. Polynesian kite traditions are used by anthropologists to get an idea of early "primitive" Asian traditions that are believed to have at one time existed in Asia. Kites were late to arrive in Europe, although windsock-like banners were known and used by the Romans. Stories of kites were first brought to Europe by Marco Polo towards the end of the 13th century, kites were brought back by sailors from Japan and Malaysia in the 16th and 17th centuries. Konrad Kyeser described dragon kites in Bellifortis about 1400 AD.
Although kites were regarded as mere curiosities, by the 18th and 19th centuries they were being used as vehicles for scientific research. In 1752 Benjamin Franklin published an account of a kite experiment to prove that lightning was caused by electricity. Kites were instrumental in the research of the Wright brothers, others, as they developed the first airplane in the late 1800s. Several different designs of man-lifting kites were developed; the period from 1860 to about 1910 became the "golden age of kiting". In the 20th century many new kite designs were developed; these included Eddy's tailless diamond, the tetrahedral kite, the Rogallo wing, the sled kite, the parafoil, power kites. Kites were used for scientific purposes in meteorology, wireless communications and photography; the Rogallo wing was adapted for stunt kites and hang gliding and the parafoil was adapted for parachuting and paragliding. The rapid development of mechanically powered aircraft diminished interest in kites. World War II saw a limited use of kites for military purposes.
Kites are now used for recreation. Lightweight synthetic materials are used for kite making. Synthetic rope and cord are used as kite line. Designs emulate flying insects and other beasts, both real and mythical; the finest Chinese kites are made from split bamboo, covered with silk, hand painted. On larger kites, clever hinges and latches allow the kite to be disassembled and compactly folded for storage or transport. Cheaper mass-produced kites are made from printed polyester rather than silk. Tails are used for some single-line kite designs to keep the kite's nose pointing into the wind. Spinners and spinsocks can be attached to the flying line for visual effect. There are rotating wind socks. On large display kites these tai
Aircraft fabric covering
Aircraft fabric covering is a term used for both the material used and the process of covering aircraft open structures. It is used for reinforcing closed plywood structures, the de Havilland Mosquito being an example of this technique, on the pioneering all-wood monocoque fuselages of certain World War I German aircraft like the LFG Roland C. II, in its wrapped Wickelrumpf plywood strip and fabric covering. Early aircraft used organic materials such as cotton and cellulose nitrate dope, modern fabric-covered designs use synthetic materials such as Dacron and butyrate dope for adhesive, this method is used in the restoration of older types that were covered using traditional methods; the purposes of the fabric covering of an aircraft are: To provide a light airproof skin for lifting and control surfaces. To provide structural strength to otherwise weak structures. To cover other non-lifting parts of an aircraft to reduce drag, sometimes forming a fairing. To protect the structure from the elements.
Pioneering aviators such as George Cayley and Otto Lilienthal used cotton-covered flying surfaces for their manned glider designs. The Wright brothers used cotton to cover their Wright Flyer. Other early aircraft used a variety of fabrics and linen being used; some early aircraft, such as A. V. Roe's first machines used paper as a covering material; until the development of cellulose based dope in 1911 a variety of methods of finishing the fabric were used. The most popular was the use of rubberised fabrics such as those manufactured by the "Continental" company. Other methods included the use of sago starch; the advent of cellulose dopes such as "Emaillite" was a major step forward in the production of practical aircraft, producing a surface that remained taut The air battles of World War I were fought with fabric-covered biplanes that were vulnerable to fire due to the flammable properties of the cloth covering and nitrocellulose dope. National insignia painted on the fabric were cut from downed aircraft and used as war trophies.
The German aircraft designer Hugo Junkers is considered one of the pioneers of metal aircraft. The flammable mixture of fabric and hydrogen gas was a factor in the demise of the Hindenburg airship. By the World War II era many aircraft designs were using metal monocoque structures due to their higher operating airspeeds, although fabric-covered control surfaces were still used on early mark Spitfires and other types; the Hawker Hurricane had a fabric covered fuselage, they had fabric covered wings until 1939. Many transports and trainers still used fabric, although the flammable nitrate dope was replaced with butyrate dope instead, which burns less readily; the Mosquito is an example of a fabric-covered plywood aircraft. The Vickers Wellington used fabric over a geodesic airframe which offered good combat damage resistance. An interesting case of ingenuity under wartime adversity was the Colditz Cock glider; this homebuilt aircraft, intended as a means of escape, employed prison bedding as its covering material.
With the development of modern synthetic materials following World War II, cotton fabrics were replaced in civil aircraft applications by polyethylene terephthalate, known by the trade-name Dacron or Ceconite. This new fabric could be glued to the airframe instead of sewn and heat-shrunk to fit. Grade A cotton would last six to seven years when the aircraft was stored outside, whereas Ceconite, which does not rot like cotton, can last over 20 years. Early attempts to use these modern fabrics with butyrate dope proved that the dope did not adhere at all and peeled off in sheets. Nitrate dope was resurrected as the initial system of choice instead, although it was supplanted by new materials too. One fabric system, developed by Ray Stits in the USA and FAA-approved in 1965, is marketed under the brand name Poly-Fiber; this uses three weights of Dacron fabric sold as by the brand name Ceconite, plus fabric glue for attaching to the airframe, fabric preparation sealer resin and paint. This system instead uses vinyl-based chemicals.
Ceconite 101 is a certified 3.5 oz/yd ² fabric. There is an uncertified light Ceconite of 1.87 oz/yd² intended for ultralight aircraft. This method requires physical attachment of the fabric to the airframe in the form of rib-stitching, rivets or capstrips, which are usually covered with fabric tapes. In addition to Poly-Fiber, a number of other companies produce covering processes for certified and homebuilt aircraft. Randolph Products and Certified Coatings Products both make butyrate and nitrate-based dopes for use with Dacron fabric. Superflite and Air-Tech systems use a similar fabric, but the finishes are polyurethane-based products with flex agents added; these finishes produce high gloss results. Falconar Avia of Edmonton, Canada developed the Hipec system in 1964 for use with Dacron fabric, it uses a special Hipec Sun Barrier that adheres fabric directly to the aircraft structure in one step, eliminating the need for the riveting, rib-stitching and taping used in traditional fabric processes.
The final paint is applied over the sun barrier to complete the process. Newer systems were developed and distributed by Stewart Systems of Cashmere and Blue River; these two systems use the same certified dacron materials as other systems, but do not use high volatile organic compounds, using water as a carrier i
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
Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered with synthetic sailcloth to form a wing; the pilot is in a harness suspended from the airframe, controls the aircraft by shifting body weight in opposition to a control frame. Early hang gliders had a low lift-to-drag ratio, so pilots were restricted to gliding down small hills. By the 1980s this ratio improved, since pilots can soar for hours, gain thousands of feet of altitude in thermal updrafts, perform aerobatics, glide cross-country for hundreds of kilometers; the Fédération Aéronautique Internationale and national airspace governing organisations control some regulatory aspects of hang gliding. Obtaining the safety benefits of being instructed is recommended. By the end of the sixth century A. D. the Chinese had managed to build kites large and aerodynamic enough to sustain the weight of an average-sized person.
It was only a matter of time before someone decided to remove the kite strings and see what happened. Most early glider designs did not ensure safe flight. Starting in the 1880s technical and scientific advancements were made that led to the first practical gliders, such as those developed in the United States by John Joseph Montgomery. Otto Lilienthal built controllable gliders in the 1890s, his rigorously documented work influenced designers, making Lilienthal one of the most influential early aviation pioneers. His aircraft is similar to a modern hang glider. Hang gliding saw a stiffened flexible wing hang glider in 1904, when Jan Lavezzari flew a double lateen sail hang glider off Berck Beach, France. In 1910 in Breslau, the triangle control frame with hang glider pilot hung behind the triangle in a hang glider, was evident in a gliding club's activity; the biplane hang glider was widely publicized in public magazines with plans for building. In April 1909, a how-to article by Carl S. Bates proved to be a seminal hang glider article that affected builders of contemporary times, as several builders would have their first hang glider made by following the plan in his article.
Volmer Jensen with a biplane hang glider in 1940 called VJ-11 allowed safe three-axis control of a foot-launched hang glider. On November 23, 1948, Francis Rogallo and Gertrude Rogallo applied for a kite patent for a flexible kited wing with approved claims for its stiffenings and gliding uses; the various stiffening formats and the wing's simplicity of design and ease of construction, along with its capability of slow flight and its gentle landing characteristics, did not go unnoticed by hang glider enthusiasts. In 1960–1962 Barry Hill Palmer adapted the flexible wing concept to make foot-launched hang gliders with four different control arrangements. In 1963 Mike Burns adapted the flexible wing to build a towable kite-hang glider. In 1963, John W. Dickenson adapted the flexible wing airfoil concept to make another water-ski kite glider. Since the Rogallo wing has been the most used airfoil of hang gliders. There are two types of sail materials used in hang glider sails: woven polyester fabrics, composite laminated fabrics made of some combinations.
Woven polyester sailcloth is a tight weave of small diameter polyester fibers, stabilized by the hot-press impregnation of a polyester resin. The resin impregnation is required to provide resistance to stretch; this resistance is important in maintaining the aerodynamic shape of the sail. Woven polyester provides the best combination of light weight and durability in a sail with the best overall handling qualities. Laminated sail materials using polyester film achieve superior performance by using a lower stretch material, better at maintaining sail shape but is still light in weight; the disadvantages of polyester film fabrics is that the reduced elasticity under load results in stiffer and less responsive handling, polyester laminated fabrics are not as durable or long lasting as the woven fabrics. In most hang gliders, the pilot is ensconced in a harness suspended from the airframe, exercises control by shifting body weight in opposition to a stationary control frame known as triangle control frame, control bar or base bar.
This bar is pulled to allow for greater speed. Either end of the control bar is attached to an upright pipe, where both extend and are connected to the main body of the glider; this creates the shape of a triangle or'A-frame'. In many of these configurations additional wheels or other equipment can be suspended from the bottom bar or rod ends. Images showing a triangle control frame on Otto Lilienthal's 1892 hang glider shows that the technology of such frames has existed since the early design of gliders, but he did not mention it in his patents. A control frame for body weight shift was shown in Octave Chanute's designs, it was a major part of the now commo
Ultralight aviation is the flying of lightweight, 1- or 2-seat fixed-wing aircraft. Some countries differentiate between weight-shift control and conventional 3-axis control aircraft with ailerons and rudder, calling the former "microlight" and the latter "ultralight". During the late 1970s and early 1980s stimulated by the hang gliding movement, many people sought affordable powered flight; as a result, many aviation authorities set up definitions of lightweight, slow-flying aeroplanes that could be subject to minimum regulations. The resulting aeroplanes are called "ultralight aircraft" or "microlights", although the weight and speed limits differ from country to country. In Europe, the sporting definition limits the maximum take-off weight to 450 kg and a maximum stalling speed of 65 km/h; the definition means that the aircraft has a slow landing speed and short landing roll in the event of an engine failure. In most affluent countries, microlights or ultralight aircraft now account for a significant percentage of the global civilian-owned aircraft.
For instance in Canada in February 2018, the ultralight aircraft fleet made up to 20.4% of the total civilian aircraft registered. In other countries that do not register ultralight aircraft, like the United States, it is unknown what proportion of the total fleet they make up. In countries where there is no specific extra regulation, ultralights are considered regular aircraft and subject to certification requirements for both aircraft and pilot. In Australia, ultralight aircraft and their pilots can either be registered with the Hang Gliding Federation of Australia or Recreational Aviation Australia. In all cases, except for built single seat ultralight aeroplanes, microlight aircraft or trikes are regulated by the Civil Aviation Regulations. Paramotor and powered hang-glider pilots do not need a licence, provided the weight of the aircraft is not more than 75 kg, but they must obey the rules of the air. For heavier microlights the current UK regulations match the European ones, except that helicopters and gyroplanes are not included.
Earlier UK microlight definitions described an aeroplane with a maximum weight of 390 kg, a maximum wing loading of 25 kg per square metre. Other than the earliest aircraft, all two-seat UK microlights have been required to meet an airworthiness standard. In 2007, Single Seat DeRegulated, a sub-category of single seat aircraft was introduced, allowing owners more freedom for modification and experiments. By 2017 the airworthiness of all single seat microlights became the responsibility of the user, but pilots must hold a microlight licence. Ultralights in New Zealand are subject to NZCAA General Aviation regulations with microlight specific variations as described in Part 103 and AC103; the United States FAA's definition of an ultralight is different from that in most other countries and can lead to some confusion when discussing the topic. The governing regulation in the United States is FAR 103 Ultralight Vehicles. In 2004, the FAA introduced the "Light-sport aircraft" category, which resembles some other countries' microlight categories.
Ultralight aviation is represented by the United States Ultralight Association, which acts as the US aeroclub representative to the Fédération Aéronautique Internationale. There are several categories of aircraft which qualify as ultralights in some countries: Fixed-wing aircraft: traditional airplane-style designs. Weight-shift control trike: use a hang glider-style wing, below, suspended a three-wheeled carriage which carries the engine and aviators; these aircraft are controlled by pushing against a horizontal control bar in the same way as a hang glider pilot flies. Powered parachute: fuselage-mounted engines with parafoil wings, which are wheeled aircraft. Powered paraglider: backpack engines with parafoil wings, which are foot-launched. Powered hang glider: motorized foot-launched hang glider harness. Autogyro: rotary wing with fuselage-mounted engine, a gyrocopter is different from a helicopter in that the rotating wing is not powered, the engine provides forward thrust and the airflow through the rotary blades causes them to autorotate or "spin up" thereby creating lift.
Helicopter: there are a number of single-seat and two-place helicopters which fall under the microlight categories in countries such as New Zealand. However, few helicopter designs fall within the more restrictive ultralight category defined in the United States of America. Hot air balloon: there are numerous ultralight hot air balloons in the US, several more have been built and flown in France and Australia in recent years; some ultralight hot air balloons are hopper balloons, while others are regular hot air balloons that carry passengers in a basket. Advancements in batteries and motor controllers has led to some practical production electric propulsion systems for some ultralight applications. In many ways, ultralights are a good application for electric power as some models are capable of flying with low power, which allows longer duration flights on battery power. In 2007, the first pioneering company in this field, the Electric Aircraft Corporation, began offering engine kits to convert ultralight weight shift trikes to electric power.
The 18 hp motor weighs an efficiency of 90 % is claimed by designer Randall Fishman. The battery consists of a lithium-polymer battery pack of 5.6kWh which provides 1.5 hours of flying in the trike applicat
Fly-by-wire is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires, flight control computers determine how to move the actuators at each control surface to provide the ordered response, it can use mechanical flight control backup systems or use fly-by-wire controls. Improved fly-by-wire systems interpret the pilot's control input as a desired outcome and calculates the control surface activities required to deliver that outcome; the pilot may not be aware of all the control outputs needed to affect a command, only that the aircraft is acting as expected. The fly-by-wire computers continually act to stabilise the aircraft and adjust its flying characteristics without the pilot's input and to prevent the pilot operating outside of the aircraft's safe performance envelope. Mechanical and hydro-mechanical flight control systems are heavy and require careful routing of flight control cables through the aircraft by systems of pulleys, tension cables and hydraulic pipes.
Both systems require redundant backup to deal with failures, which increases weight. Both have limited ability to compensate for changing aerodynamic conditions. Dangerous characteristics such as stalling and pilot-induced oscillation, which depend on the stability and structure of the aircraft concerned rather than the control system itself, are depending on pilot's action; the term "fly-by-wire" implies. It is used in the general sense of computer-configured controls, where a computer system is interposed between the operator and the final control actuators or surfaces; this modifies the manual inputs of the pilot in accordance with control parameters. Side-sticks, centre sticks. A pilot commands the flight control computer to make the aircraft perform a certain action, such as pitch the aircraft up, or roll to one side, by moving the control column or sidestick; the flight control computer calculates what control surface movements will cause the plane to perform that action and issues those commands to the electronic controllers for each surface.
The controllers at each surface receive these commands and move actuators attached to the control surface until it has moved to where the flight control computer commanded it to. The controllers measure the position of the flight control surface with sensors such as LVDTs. Fly-by-wire control systems allow aircraft computers to perform tasks without pilot input. Automatic stability systems operate in this way. Gyroscopes fitted with sensors are mounted in an aircraft to sense rotation on the pitch and yaw axes. Any movement results in signals to the computer, which can automatically move control actuators to stabilize the aircraft. While traditional mechanical or hydraulic control systems fail the loss of all flight control computers renders the aircraft uncontrollable. For this reason, most fly-by-wire systems incorporate either redundant computers, some kind of mechanical or hydraulic backup or a combination of both. A "mixed" control system with mechanical backup feedbacks any rudder elevation directly to the pilot and therefore makes closed loop systems senseless.
Aircraft systems may be quadruplexed to prevent loss of signals in the case of failure of one or two channels. High performance aircraft that have fly-by-wire controls may be deliberately designed to have low or negative stability in some flight regimes – rapid-reacting CCV controls can electronically stabilize the lack of natural stability. Pre-flight safety checks of a fly-by-wire system are performed using built-in test equipment. A number of control movement steps can automatically performed, reducing workload of the pilot or groundcrew and speeding up flight-checks; some aircraft, the Panavia Tornado for example, retain a basic hydro-mechanical backup system for limited flight control capability on losing electrical power. A FBW aircraft can be lighter than a similar design with conventional controls; this is due to the lower overall weight of the system components, because the natural stability of the aircraft can be relaxed for a transport aircraft and more for a maneuverable fighter, which means that the stability surfaces that are part of the aircraft structure can therefore be made smaller.
These include the horizontal stabilizers that are at the rear of the fuselage. If these structures can be reduced in size, airframe weight is reduced; the advantages of FBW controls were first exploited by the military and in the commercial airline market. The Airbus series of airliners used full-authority FBW controls beginning with their A320 series, see A320 flight control. Boeing followed with their 777 and designs. Servo-electrically operated control surfaces were first tested in the 1930s on the Soviet Tupolev ANT-20. Long runs of mechanical and hydraulic connections were replaced with electric servos; the first pure electronic fly-by-wire aircraft with no mechanical or hydraulic backup was the Apollo Lunar Landi
A wing tip is the part of the wing, most distant from the fuselage of a fixed-wing aircraft. Because the wing tip shape influences the size and drag of the wingtip vortices, tip design has produced a diversity of shapes, including: Squared-off Aluminium tube bow Rounded Hoerner style Winglets Drooped tips Raked wingtips Tip tanks Sails Fences End platesWinglets have become popular additions to high speed aircraft to increase fuel efficiency by reducing drag from wingtip vortices. In lower speed aircraft, the effect of the wingtip shape is less apparent, with only a marginal performance difference between round and Hoerner style tips The slowest speed aircraft, STOL aircraft, may use wingtips to shape airflow for controlability at low airspeeds. Wing tips are an expression of aircraft design style, so their shape may be influenced by marketing considerations as well as by aerodynamic requirements. Wing tips are used by aircraft designers to mount navigation lights, anti-collision strobe lights, landing lights and identification markings.
Wing tip tanks can distribute weight more evenly across the wing spar. On fighter aircraft, they may be fitted with hardpoints, for mounting drop tanks and weapons systems, such as missiles and electronic countermeasures. Wingtip mounted. Aerobatic aircraft use wingtip mounted crosses for visual attitude reference. Wingtip mounted smoke fireworks highlight rolling aerobatic maneuvers; some airshow acts feature the pilot dragging the wingtip along the ground. Aircraft with a single main landing gear or high aspect ratio wings such as gliders, may place small landing gear in the wingtips; some uncommon designs,like the Rutan Quickie, Convair XFY placed the main landing gear in the wingtips. Some early World War I aircraft used wooded skids on the wingtips to minimize damage on ground looping incidents. Several amphibious aircraft such as the Consolidated PBY Catalina, use retractable wingtips as floats. Moveable wingtips can affect the controlability of a wing. Wing warping the ends of the wing, produced roll control on the earliest of aircraft such as the Wright Flyer.
The North American XB-70 Valkyrie raised and lowered its wingtips in flight to adjust its stability in supersonic and subsonic flight. Wingtips can house the power plant or thrust of an aircraft; the EWR VJ 101 used tip mounted jets, the V-22 uses tilting wingtip mounted engines, the Harrier uses wingtip thrust for stability while hovering. Rotary wing aircraft wingtips may be curved to reduce noise and vibration; some rotary wing aircraft place their propulsion in wingtip tip jets. The Boeing 777X will feature 3.5 m folding wingtips supplied by Liebherr Aerospace from Lindenberg. The mechanism was demonstrated for Aviation Week at the Boeing Everett Factory in October 2016; the folding takes 20 seconds to complete. Wingtip device