NationMaster - Encyclopedia: Ground effect

The term Ground effect (or Wing In Ground effect) refers to the increase in lift experienced by an aircraft as it approaches within roughly 1/4 of a wingspan's length of the ground or other level surface (such as the sea). It can present a hazard for inexperienced pilots who are not accustomed to correcting for it on their approach to landing, but it has also been used to effectively enhance the performance of certain kinds of aircraft whose planform has been adapted to take advantage of it, such as the Russian ekranoplans. The term is also sometimes used in motorsport to refer to aerodynamic techniques for increasing downforce, such as wings and venturi tunnels, but strictly speaking they are not exploiting the same aerodynamic phenomena as the ground effect in fixed and rotary wing aircraft. The lift force, lifting force or simply lift consists of the sum of all the fluid dynamic forces on a body perpendicular to the direction of the external flow approaching that body. ... An Airbus A380, currently the worlds largest airliner An aircraft is any vehicle or craft capable of atmospheric flight. ... A Laughing Gull on the beach in Atlantic City. ... Sea as seen from jetty in Frankston, Australia Look up Sea in Wiktionary, the free dictionary. ... Hazard is a term used in evaluating safety: A hazard is a potential unwanted event. ... An aviator is a person who flies aircraft for pleasure or as a profession. ... A planform or plan view is a vertical orthographic projection of an object on a horizontal plane, like a map. ... An ekranoplan (Russian: , literally screen plane) is a vehicle resembling an aircraft, but operating solely on the principle of ground effect. ... Auto racing (also known as automobile racing or autosport) is a sport involving racing automobiles. ... The term downforce describes the downward pressure created by the aerodynamic characteristics of a racing car that allow it to travel faster through a corner by holding the car to the track or road surface. ... A Laughing Gull on the beach in Atlantic City. ... A Venturi meter is shown in a diagram, the pressure in 1 conditions is higher than 2, and the relationship between the fluid speed in 2 and 1 respectively, is the same as for pressure. ...

Ground effect in aircraft

Wings create lift through the generation of a high(er) pressure area below the wing and a low(er) pressure area above the wing; this is what contributes to the lifting force. The air under the wing, since it is of higher relative pressure, tends to flow outwards towards the wing tip and wing root. The low-pressure air above the wing likewise tends to flow inwards from the wing tip and root towards the wing centre. At the wingtips, outward-flowing air from beneath the wing meets inward-flowing air from above the wing, resulting in wingtip vortices. Wingtip vortices cause major induced drag, which reduces the amount of lift produced by the wing - reducing its effective angle of attack and raising the stall speed of the aircraft. Image File history File links Information_icon. ... Image File history File links Ekranoplan. ... Image File history File links Ekranoplan. ... Soviet redirects here. ... The Caspian Sea is the largest lake on Earth by both area and volume,[1] with a surface area of 371,000 square kilometres (143,244 miÂ²) and a volume of 78,200 cubic kilometres (18,761 miÂ³).[2] It is a landlocked endorheic body of water and lies between... A Laughing Gull on the beach in Atlantic City. ... The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... The lift force, lifting force or simply lift consists of the sum of all the fluid dynamic forces on a body perpendicular to the direction of the external flow approaching that body. ... It has been suggested that this article or section be merged with Wake turbulence. ... In aerodynamics, lift-induced drag, or more simply, induced drag, is a drag force arising from the generation of lift by wings or a lifting body during flight. ... In this diagram, the black arrow represents the direction of the wind. ... Stall speed is an aerodynamic term. ...

It is thought that the phenomenon of ground effect is caused by the ground 'interrupting' the wingtip vortices. When a wing is flown very close to the ground, wingtip vortices are unable to form effectively due to the obstruction of the ground. The result is lower induced drag, which increases the performance of the aircraft while it is experiencing the ground effect. (Winglets, vertical surfaces on the wingtips of an aircraft, operate under the same principle. Use of winglets can decrease induced drag and thereby increase performance and fuel efficiency somewhat. Many modern large aircraft are now built with winglets). A winglet is a device used to improve the efficiency of aircraft by lowering the lift-induced drag caused by wingtip vortices. ...

Factors affecting ground effect are numerous, and may include the wing's area, its chord length, and its angle-of-attack as it nears the surface in a landing attitude, as well as the weight, speed, and configuration of the aircraft, and wing loading(aircraft weight per unit-area of wing). In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. ...

Consider a heavy, high-speed fighter jet, with a comparatively small wing area. The wing is highly loaded, and twenty-thousand pounds landing at one hundred and twenty knots will probably not experience much ground effect. A light, slow Piper Cub however, will likely be much affected. A low-wing airplane of the same size even more so. A sailplane may be less affected due to the short chord and very long wingspan (in other words, high aspect ratio) for weight, which minimizes the salience of induced drag caused by wingtip vortices. Gliders are un-powered heavier-than-air aircraft. ... The aspect ratio of a two-dimensional shape is the ratio of its longer dimension to its shorter dimension. ... In aerodynamics, lift-induced drag, or more simply, induced drag, is a drag force arising from the generation of lift by wings or a lifting body during flight. ...

On the other hand, since sailplanes generally are built to minimize all form drag and parasite drag as well, the reduction in the induced drag caused by ground effect can in fact effectively increase flight performance, resulting in an enhanced glide ratio. Pilots of sailplanes who seek to exploit this phenomenon on landing are said to be performing a "penetration approach." A successful penetration approach would involve diving at a speed higher than the usual optimal glide speed for a given sailplane (which would result in a sub-optimal glide ratio on the descent), and then flaring and holding the lowest possible altitude above the ground, at this relatively high speed. Theoretically the positive effect of ground effect - decreased drag - could result in a final stopping place farther than would have been achieved, had the pilot simply flown the speed resulting in the best glide ratio. Obviously, a penetration approach is fraught with risks, and it is not a sure bet that performance will be increased; thus it is not a generally recommended means of improving glide distance. In aerodynamics, form drag, profile drag, or pressure drag, is a component of parasitic drag. ... Parasitic drag (also called parasite drag) is drag caused by moving a solid object through a fluid. ... In aerodynamics, lift-induced drag, or more simply, induced drag, is a drag force arising from the generation of lift by wings or a lifting body during flight. ... Glide ratio is an aviation term that refers to the distance an aircraft will move forward for any given amount of lost altitude (the cotangent of the downward angle). ...

Ground effect during take-off is thought to be a cause of many aircraft accidents. A small plane loaded beyond gross weight capabilities may be able to take off under ground effect, thanks to the 'artifically' low stall speed due to the decreased induced drag. But it may not be able to climb beyond a certain point. Once the pilot climbs out of ground effect wingtip vortices will form, the wings will stall, and the aircraft will suddenly descend - usually resulting in a crash.

Some critics of Howard Hughes's massive Spruce Goose claim that the famous flying boat's first (and only) flight was due entirely to ground effect and that the craft was incapable of sustaining flight above a very low altitude. It's probably true the the Spruce Goose was underpowered in its current configuration - development of the engines the plane was designed to carry was canceled before completion, and as a result, the goose was running at probably 60% of its designed power. Nevertheless the power necessary to bring a seaplane to flight speeds is greater than land-planes, and the height the goose reached was probably well beyond the ground effect for such a heavy-lifter. Howard Robard Hughes, Jr. ... Hughes H-4 Hercules The Spruce Goose is the nickname commonly given to the Hughes H-4 Hercules, an aircraft designed and built by the Hughes Aircraft company, owned by Howard Hughes. ... Boeing 314 A flying boat is an aircraft that is designed to take off and land on water, in particular a type of seaplane which uses its fuselage as a floating hull (instead of pontoons mounted below the fuselage). ...

Ground effect is much misunderstood. During landing, a small plane may 'float' some distance down the runway beyond the pilot's intended touch-down point, but this is mostly due to the airplane's change in attitude as the pilot 'flares' for landing. During the flare, the pilot is arresting the steady rate of descent he/she has maintained during the final approach by rotating the aircraft about its pitch axis. This increases the wing's angle of attack and increases lift, ideally resulting in a smooth landing. Flight dynamics is the study of orientation of air and space vehicles and how to control the critical flight parameters, typically named pitch, roll and yaw. ... In this diagram, the black arrow represents the direction of the wind. ...

Ground effect, often described as a 'cushion', is thought to be an INCREASE in air pressure which occurs below a wing when it comes into close proximity with the ground. Generally this is imagined to occur during the flare for landing. But while apparently a real phenomenon, ground effect is probably much more subtle than is commonly imagined. What is typically thought of as ground effect is probably created when the pilot misjudges the flare maneuver and floats before landing. This can be compounded by varying winds and unpredictable airflows as they interact with local structures and topography. Real ground effect probably occurs only within a few feet of the ground in a small airplane, or perhaps within a quarter of the wingspan for a large airliner.

Ground effect in cars

In racing cars, a designer's aim is not for increased lift but for increased downforce, allowing greater cornering speeds. (By the 1970s 'wings', or inverted aerofoils, were routinely used in the design of racing cars to increase downforce, but this is not ground effect.) This kind of ground effect is easily illustrated by taking a tarpaulin out on a windy day and holding it close to the ground, it can be observed that when close enough to the ground the tarp will suddenly be sucked towards the ground. The term downforce describes the downward pressure created by the aerodynamic characteristics of a racing car that allow it to travel faster through a corner by holding the car to the track or road surface. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ... An airfoil (or aerofoil in British English) is a specially shaped cross-section of a wing or blade, used to provide lift or downforce, depending on its application. ... A tarpaulin or tarp (also known as hootchie) is a large sheet of strong, flexible, water resistant or waterproof material, often cloth such as canvas coated with plastic or latex. ...

However, substantial further downforce is available by understanding the ground to be part of the aerodynamic system in question. The basic idea is to create an area of low pressure underneath the car, so that the higher pressure above the car will apply a downward force. Naturally, to maximize the force one wants the maximal area at the minimal pressure. Racing car designers have achieved low pressure in two ways: first, by using a fan to push air out of the cavity; second, to design the underside of the car so that large amounts of incoming air are accelerated through a narrow slot between the car and the ground, lowering pressure by Bernoulli's principle. Official regulations as of 2006 disallow ground effects in many types of racing, such as Formula One although it is still permitted in Champ cars. The use of water pressure - the Captain Cook Memorial Jet in Lake Burley Griffin, Canberra. ... Bernoullis principle states that in an ideal fluid (low speed air is a good approximation), with no work being performed on the fluid, an increase in velocity occurs simultaneously with decrease in pressure or gravitational energy. ... 2006 is a common year starting on Sunday of the Gregorian calendar. ... Formula One - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Champcar has been the name for the class of cars used in the United States premier open wheel auto racing series for decades. ...

Jim Hall, the first car aerodynamicist to harness downforce, built Chaparral cars to both these principles. His 1961 car attempted to use the shaped underside method but there were too many other aerodynamic problems with the car for it to work properly. His 1966 cars used a dramatic high wing for their downforce. His Chaparral 2J "sucker car" of 1970 was revolutionary. It had two fans at the rear of the car driven by a dedicated two-stroke engine; it also had "skirts", which left only a minimal gap between car and ground, so as to seal the cavity from the atmosphere. Although it did not quite win a race, the competition lobbied for its ban, which came into place at the end of that year. Movable aerodynamic devices were banned from most branches of the sport. Jim Hall is a programmer for the FreeDOS project and the original developer of the GNU Robots program. ... Chaparral Cars was a United States automotive company which built cars in the 1960s. ... The two-stroke cycle of an internal combustion engine differs from the more common four-stroke cycle by having only two strokes (linear movements of the piston) instead of four, although the same four operations (intake, compression, power, exhaust) still occur. ...

Formula One in the late 1970s was the next setting for ground effect in racing cars. In 1977 Lotus brought out their "Wing Car", the Lotus 78, designed by Peter Wright, Colin Chapman, and Tony Rudd. Its sidepods, bulky constructions between front and rear wheels, were shaped as inverted aerofoils and sealed with flexible "skirts" to the ground. The team won 5 races that year, and 2 in 1978 while they developed the much improved Lotus 79. The most notable contender in 1978 was the Brabham BT46B Fancar, designed by Gordon Murray. Its fan, spinning on a horizontal, longitudinal axis at the back of the car, took its power from the main gearbox. The car avoided the sporting ban by claims that the fan's main purpose was for engine cooling as less than 50% of the airflow was used to create a depression under the car . It raced just once, with Niki Lauda winning at the Swedish Grand Prix. However, the team, led by Bernie Ecclestone who had recently become president of the Formula One Constructors Association, withdrew the car before it had a chance to be banned. The Lotus 79, on the other hand, went on to win 6 races and the world championship for Mario Andretti. In following years other teams copied and improved on the Lotus until cornering speeds became dangerously high, resulting in several severe accidents in 1982 (most notably the death of Gilles Villeneuve), flat undersides became mandatory for 1983. Part of the danger of relying on ground effects to corner at high speeds is the possibility of the sudden removal of this force; if the belly of the car contacts the ground, the flow is constricted too much, resulting in almost total loss of any ground effects. If this occurs in a corner where the driver is relying on this force to stay on the track, its sudden removal can cause the car to abruptly lose most of its traction and skid off the track. Formula One - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Lotus Cars is a British manufacturer of sports cars and racing cars based in Hethel, Norfolk, formed as Lotus Engineering Ltd. ... The Lotus 78 wing car was the car that started the ground effect revolution in Formula 1, in the 1977 racing season. ... See also Peter Wright (rugby player) and Pete Wright (musician) Peter Wright (born on August 9, 1916 in Chesterfield, Derbyshire, United Kingdom - died April 27, 1995 in Tasmania, Australia) was a former MI5 counterintelligence officer noted for writing the controversial book Spycatcher (ISBN 0670820555), which was part memoir, part expos... Wikiquote has a collection of quotations related to: Colin Chapman Anthony Colin Bruce Chapman (born 9 May 1928 in London - died 16 December 1982) was an influential designer, inventor, and builder in the automotive industry. ... Lotus 79 at the 2006 Goodwood Festival of Speed The Lotus 79 was a Formula 1 car designed in late 1977 by Colin Chapman, Martin Ogilvie, Tony Rudd and Peter Wright of Lotus. ... Brabham - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... The Brabham BT46 was a Formula One racing car, designed by Gordon Murray for the Brabham team owned by Bernie Ecclestone for the 1978 Formula One season. ... Gordon Murray (born 1946 in Durban, South Africa) is a renowned designer of Formula 1 race cars and the McLaren F1 roadcar. ... Andreas Nikolaus Niki Lauda (born February 22, 1949 in Vienna) is an Austrian entrepreneur, former Formula One (F1) racing driver and three-time F1 World Champion. ... Bernard Charles Bernie Ecclestone (born October 29, 1930 in Ipswich, Suffolk, United Kingdom) is the president and CEO of Formula One Management and Formula One Administration, and owns a stake in Alpha Prema, the parent company of the Formula One Group of companies. ... The Formula One Constructors Association (FOCA) is an organization of the chassis builders (constructors) who design and build the cars that race in the Formula One Grands Prix. ... Mario Gabriele Andretti (born February 28, 1940 in Montona dIstria, Italy, now Motovun, Croatia) is an Italian American racing driver, and one of the most successful Americans in the history of auto racing. ... For other members of the family, see Jacques Villeneuve and Jacques Villeneuve (elder). ...

Note that while such downforce-producing aerodynamic techniques are often referred to with the catch-all term "ground effect", they are not strictly speaking a result of the same aerodynamic phenomenon as the ground effect which is apparent in aircraft at very low altitudes. The term downforce describes the downward pressure created by the aerodynamic characteristics of a racing car that allow it to travel faster through a corner by holding the car to the track or road surface. ... Altitude is the elevation of an object from a known level or datum. ...

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Ground effect in cars

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Ground effect in aircraft