Ground-effect vehicle

The term Ground-Effect Vehicle originally referred to any craft utilizing ground effect, including what is known later as hovercraft, in descriptions of patents during the 1950s.

A ground-effect vehicle needs some forward velocity to produce lift dynamically, and the principal benefit of operating a wing in ground effect is to reduce its lift-dependent drag.

The high and low pressures are maintained until they flow off the ends of the wings, where they form vortices which in turn are the major cause of lift-induced drag—normally a significant portion of the drag affecting an aircraft.

Once sufficient speed has built up, some GEVs may be capable of leaving ground effect and functioning as normal aircraft until they approach their destination.

The distinguishing characteristic is that they are unable to land or take off without a significant amount of help from the ground effect cushion, and cannot climb until they have reached a much higher speed.

The wings are significantly shorter than those of comparable aircraft, and this configuration requires a high aft-placed horizontal tail to maintain stability.

Hanno Fischer later developed WIG craft based on the configuration, which were then transferred to multiple companies in Asia, thus becoming one of the "standards" in GEV design.

Since most GEVs are designed to operate from water, accidents and engine failure typically are less hazardous than in a land-based aircraft, but the lack of altitude control leaves the pilot with fewer options for avoiding collision, and to some extent that negates such benefits.

Low altitude brings high-speed craft into conflict with ships, buildings and rising land, which may not be sufficiently visible in poor conditions to avoid.

[5] GEVs may be unable to climb over or turn sharply enough to avoid collisions, while drastic, low-level maneuvers risk contact with solid or water hazards beneath.

Like conventional aircraft, greater power is needed for takeoff, and, like seaplanes, ground-effect vehicles must get on the step before they can accelerate to flight speed.

The bottom of the vehicle must be formed to avoid excessive pressures on landing and taking off without sacrificing too much lateral stability, and it must not create too much spray, which damages the airframe and the engines.

Finally, limited utility has kept production levels low enough that it has been impossible to amortize development costs sufficiently to make GEVs competitive with conventional aircraft.

A 2014 study by students at NASA's Ames Research Center claims that use of GEVs for passenger travel could lead to cheaper flights, increased accessibility and less pollution.

[8] The International Maritime Organization recognizes three types of GEVs:[8] At the time of writing, those classes only applied to craft carrying 12 passengers or more,[8] and (as of 2019) there was disagreement between national regulatory agencies about whether these vehicles should be classified, and regulated, as aircraft or as boats.

[9] By the 1920s, the ground effect phenomenon was well-known, as pilots found that their airplanes appeared to become more efficient as they neared the runway surface during landing.

In 1934 the US National Advisory Committee for Aeronautics issued Technical Memorandum 771, Ground Effect on the Takeoff and Landing of Airplanes, which was a translation into English of a summary of French research on the subject.

The French author Maurice Le Sueur had added a suggestion based on this phenomenon: "Here the imagination of inventors is offered a vast field.

The ground interference reduces the power required for level flight in large proportions, so here is a means of rapid and at the same time economic locomotion: Design an airplane which is always within the ground-interference zone.

But on large-sized aircraft, over water, the question may be attempted ..."[10] By the 1960s, the technology started maturing, in large part due to the independent contributions of Rostislav Alexeyev in the Soviet Union[11] and German Alexander Lippisch, working in the United States.

It is said that the research hydrofoil HD-4 by Alexander Graham Bell had part of its dynamic lift contributed by its pair of wings operating in ground effect.

[13] Led by Alexeyev, the Soviet Central Hydrofoil Design Bureau (Russian: ЦКБ СПК) was the center of ground-effect craft development in the USSR.

The military potential for such a craft was soon recognized, and Alexeyev received support and financial resources from Soviet leader Nikita Khrushchev.

Several other projects were proposed throughout the early Cold War, some using a similar mix of wings and lift engines while others are more akin to Russian types.

This design proved to be stable and efficient in ground effect, and even though it was successfully tested, Collins decided to stop the project and sold the patents to the German company Rhein Flugzeugbau (RFB), which further developed the inverse delta concept into the X-113 and the six-seat X-114.

[27] With Russian consultation, the United States Defense Advanced Research Projects Agency (DARPA) studied the Aerocon Dash 1.6 wingship.

in 2013[38] Estonian transport company Sea Wolf Express planned to launch passenger service in 2019 between Helsinki and Tallinn, a distance of 87 km taking only half an hour, using a Russian-built ekranoplan.

The program aims to carry 90 tons over 6,500 nautical miles (12,000 km), operate at sea without ground-based maintenance, all using low-cost materials.