Hovercraft
A hovercraft ( English hovercraft [ ˈhʌvəɹˌkɹæft ], German 'Schwebefahrzeug' ) is a vehicle that uses air to form a kind of cushion between itself and the surface of the earth so that it floats. Typically, a hovercraft is a hovercraft or amphibious vehicle . It is used to transport goods and people, as an expedition vehicle or as an auxiliary vehicle for rescue services and fire departments. As a watercraft, it requires a driving license for the corresponding vehicle size.
development
In 1877, the designer of the first torpedo boats , John Isaac Thornycroft , applied for a patent for an air cushion technology, but did not implement it in a design . Thornycroft's idea was to put a thin layer of air between the hull and the water.
Austria-Hungary
On September 2, 1915, the world's first test run of a fully functional side air cushion boat took place. The developer was Dagobert Müller von Thomamühl from the kuk Kriegsmarine . The “gliding boat” designed as a “fast torpedo carrier” reached more than 30 knots (56 km / h). It was propelled by five aircraft engines, only one of which created a draft under the hull; the others were connected to conventional propellers. The armament consisted of two torpedoes , a machine gun and three depth charges . A few test drives were organized, but the project was terminated as early as 1917 due to insufficient load-bearing capacity, seaworthiness and protective function; in addition, the aircraft engines borrowed from the air force had to be returned.
Soviet Union and successor states
In 1927, experiments with an air cushion apparatus were carried out at the Polytechnic Institute on the Don in the Soviet Union . It had a diameter of 80 cm and was driven by an electric motor. This model was developed by W. I. Lewkow . In 1934 Levkow was professor of applied aerodynamics at the Moscow Institute for Aircraft Construction and in the spring presented a significantly enlarged model to a special commission, which included the aerodynamicist Prof. B. N. Jurjew and the aircraft designer A. N. Tupolev . Then he received the order to build a test vehicle. This was realized in 1935 in the workshops of the Moscow Institute for Aircraft Construction and tested under the name L 1 in the summer of the same year. It had a water displacement of 1.5 tons, had three seats and was most recently equipped with 140 hp (103 kW) engines.
In 1937 the hovercraft L 5 was created. It was made of duralumin and was equipped with two 860 hp (633 kW) aircraft engines. The vehicle was 24 m long, 5.35 m wide and had a water displacement of 8.6 tons. When tested in the late autumn of 1937 in the Koporsk Bay of the Gulf of Finland, it reached a speed of over 70 knots (130 km / h). After that, up to 15 more vehicles are said to have been manufactured; There is evidence for the existence of vehicles L 9 and L 11. The L-series boats were all destroyed in World War II and further developments were discontinued during the war.
Despite the good amphibious properties on water and on land, these vehicles had too little load capacity due to the chosen catamaran construction, which was open at the front and rear , because the amount of air required for operation was very high and the overpressure required for floating could only be achieved to a small extent. After the war, Levkow worked as chief designer for hovercraft; he died in 1954.
From 1985 to 2004, 15 boats of the Zubr class developed in the 1980s were built in Saint Petersburg and Feodosia . After the end of the Soviet Union, two boats were scrapped before completion and three boats were handed over to Ukraine, which built another boat itself. As of 2001, three new boats were built for Greece. China bought 4 boats from Greece and 2 boats from Ukraine and the right to build two more in China, making it the largest active fleet in its class.
In 2009 Ukraine and China signed an agreement for the supply of four large hovercraft (known as the European Bison) and technology transfer .
Great Britain
In the west, the hovercraft was developed by the British engineer Christopher Cockerell in the 1950s . In his first experiments with empty tin cans, a hair dryer and kitchen scales, he demonstrated that the air cushion principle works. Later he had a 60 cm long working model built. In 1955 he patented the device and named it Hover Craft . The special technical trick was guiding the air flow on the outer edge of the vehicle in a double wall, so that it gained higher pressure than previously known and was therefore able to push the vehicle off the ground with greater efficiency . Cockerell's basic version was based on a completely rigid body.
The first drivable models of the concept proved to be consistently suitable. The ability to drive over water has also been successfully demonstrated. With the exception of the limited gradeability and the maximum obstacle size of (depending on the model) up to 25 cm, the vehicle turned out to be suitable for all surfaces, including ice and desert sand. The ground had hardly any influence on the maximum speed of typically around 60 km / h.
In 1957, Cockerell demonstrated his device to the British military. Although this was not immediately interested in it, the seaworthiness in high waves was called into question. However, it was classified as an object of national secrecy, so Cockerell was not allowed to demonstrate his invention anywhere else for a year.
After the release (declassification) in 1958 he was finally able to convince the National Research Development Corporation , an organization funded by the British government, to develop the device for commercial purposes.
In July 1959, the first fully-fledged hovercraft, the SR.N1, crossed the English Channel for the first time .
An essential functional component of today's construction was later added by the British military during the trial: a rubber apron, which was able to seal the air cushion much better against uneven surfaces and thus contributed to lower leakage currents and a greater ground clearance. The successor models were successfully tested by the British armed forces in long-distance tests over a few hundred kilometers in the Libyan desert and the Canadian Arctic Ocean. The British now have one of the few battalions with hovercraft.
In 1962, the UK began its first regular hovercraft passenger service in North Wales . A little later there was a connection from Portsmouth to Ryde on the Isle of Wight , which is still served by the Hovertravel shipping company today. In 1966, connections across the English Channel from Ramsgate and Dover to Calais were offered as a pure passenger service for the first time.
Hovercraft construction in England reached its peak with the Saunders Roe Nautical 4 (SR.N4) hovercraft, which entered service in 1968 . They were the largest civil hovercraft in the world and at the same time the only hovercraft that carried cars and buses in addition to passengers. A total of six copies were built, which from 1968 replaced the pure passenger hovercraft on the English Channel. They were in use between Dover and Calais until 2000.
In the commercial hovercraft sector, numerous boats from Griffon hoverworks are in use today. These boats are used both as ferries (Portsmouth to the Isle of Wight) and as SAR vehicles. In addition, four boats of the type 2400 TD were sold to the British Navy, which replaced their four 2000 TDs from 1993 to 1995.
France
The French hovercraft, which was developed as a separate development line with the participation of the engineer Jean Bertin from the Société d'Etude et de Développement des Aéroglisseurs Marins (SEDAM) , are known as Naviplane . They went their own way, especially with the apron construction. Instead of a large chamber that was ultimately subdivided for stabilization, a number of smaller chambers were initially used. The working principle was finally abandoned in favor of the simpler and cheaper English construction. On the ferries, the aprons, which gradually wore out, were replaced by others.
The ferries were used for ferry services in the English Channel and on the Bay of Biscay. A total of three different types have been developed. The N.102 was a small naviplane for up to twelve passengers, the N.300 could carry 90 passengers. In 1977 the N.500 was built, which with 400 passengers and 60 cars had a similar capacity to the British SR.N4 Mk III . However, just two weeks after the first test drive, the first N.500 burned out after an explosion when it took off. Only one other example was built, which was in service from 1978 to 1983 for the British shipping company Seaspeed and its successor, Hoverspeed . However, due to frequent technical defects, it was retired after only five years and scrapped in 1985. The SEDAM shipyard went bankrupt in 1982. In total, only six N.102, two N.300 and two N.500 were built, none of which have survived today.
United States
The US Navy also operates several Hovercraft Squadrons ( LCAC ), with the vehicles essentially replacing conventional landing craft and thus being used as transporters. Gas turbines are used for propulsion . The vehicle is propelled by several swiveling air jets.
Japan
From 1971 to 2010 a ferry service was operated by Oita Hover Ferry Co., Ltd. on the route between Oita City or Beppu City and Oita Airport . operated. The last vehicle used had the designation MV-PP10.
technology
Full hovercraft
With these vehicles, the entire fuselage is provided with a flexible apron. A permanent air cushion is built up in the enclosed area by means of a fan. On this air cushion, the boat floats virtually without contact above the ground or water, only the skirts lie lightly on uneven ground.
Full hovercrafts can drive both in the water and on land, they are amphibious. The propulsion takes place with propellers or impellers in the air flow, the control with air rudders, similar to the tail unit in aircraft .
Well-known patterns are:
- SR.N4 of the English ferry service from Dover across the English Channel
- the Naviplanes as the French counterpart were also used in coastal transport
- American military hovercrafts and the sometimes much larger Russian-made landing craft
Related concepts
Rail vehicles
At the same time as the experiments with magnetic levitation technology, the Aérotrain hovercraft was developed under Jean Bertin , especially in France , between 1965 and 1974. After a few speed records, the project was discontinued and most of the vehicles were later destroyed by fire or scrapped. The elaborate elevated concrete driveway and the initial use of propeller or jet drives are cited as the reason why the technology did not catch on.
In addition to the high-speed variant, there were slower vehicles that were finally ready for practice and used. Mention should be made of the subway in Serfaus, Austria . The side rail only serves as a guide, the train runs on air cushions. The drive of the air-cushion track, which runs a few meters below the road, is taken over by a cable running sideways - like a funicular railway .
Floor effect device
Ground effect devices are only similar to hovercraft because of the physical principle. They use the ground effect , which creates higher lift close to the ground compared to free-flying aircraft, due to the air roll that moves under the wing profile of the ground-effect vehicle. Basically, the distinction applies here between single-wing ground effect vehicles, which can leave the ground effect and have aircraft characteristics, and the damming wing vehicles with tandem wing constructions, which as pure ground effect vehicles cannot leave the area close to the ground. The single-wing ground-effect planes include the Russian Ekranoplane , the designs by Alexander Lippisch , Hanno Fischer and the simple stowage wings.
The ground effect vehicles based on the damper wing principle by Günther W. Jörg , also called Tandem Airfoil Flairboat , are of great technical importance.The arrangement of two pairs of wings with fuselage and rear propeller ensures safe inherent stability and reliable operation within the ground effect.
In contrast to other hovercraft such as hovercraft, the air cushion is not generated by additional aids (blower), but is created solely by the special wing shape and arrangement as a result of the forward thrust. These tandem Airfoil Flairboats cannot leave the ground effect and are therefore classified and approved as ships or watercraft .
SES (Surface Effect Ships)
A SES is a vessel in catamaran construction method with two hulls, wherein the gap between the two hulls at the bow and stern is sealed by a flexible skirt depending from rubber material. With powerful fans, air is constantly blown into the space between the hulls and the aprons. As a result, the boat is partially lifted out of the water and begins to glide at faster speeds. An SES is propelled by conventional ship propellers and controlled by conventional rudder blades. SES can reach speeds of up to 60 knots, but they are not amphibious. This concept is also occasionally used on warships, for example in the Norwegian Skjold and Russian Bora classes . In 1989 Blohm + Voss built the air-cushion catamaran Corsair , which was used as a test vehicle .
Hover platforms
A hover platform is used to transport loads, whereby the air cushion enables even the most bulky and heaviest loads to be transported on a very flat surface with almost no friction.
Terraplane
This is a French variant of an all-terrain, partly amphibious vehicle on wheels or chains with air cushion support. The air cushions are generated directly by turbines or blowers, nozzles support the effect. The aprons are located between the chains or wheels.
The concept turned out to be workable. Technically, the development can be seen as the predecessor of today's hover platforms with external traction devices.
Sports
Hovercrafts are also used for sports and competitions. They are usually around 3 meters long and reach more than 100 km / h; there are six formula classes in Germany .
| Formula class | Restrictions |
|---|---|
| formula 1 | no restrictions on cubic capacity and number of engines |
| Formula 2 | no restrictions on the number of engines, total displacement limited to max. 600 cc 2T / 750 cc 4T |
| Formula 3 | no restrictions on the number of engines, total displacement limited to max. 250 cm³ (discontinued with the 2008 racing season, as there was only one driver in Europe (except in the UK series)) |
| Formula 50 | only one motor for drive and buoyancy, restrictions on motor type (Rotax 503 with 500 cm³) and original Rotax exhaust system. Engine power 54 hp |
| Formula 35 | Total output of all engines maximum 35 HP (is mainly driven in Great Britain ) |
| Formula 25 | Total output of all engines maximum 25 hp (last driven at the 2008 World Cup in Sweden, replaced by Formula 35 at the 2010 World Cup) |
| Formula S | only one motor for drive and buoyancy, otherwise no restrictions |
| Formula J | Juniors from 11 years of age, limited performance |
| Formula N | Collection group for all newbies, no restrictions, but under constant supervision of the race management |
Accidents
In the course of history, there have been only a few significant accidents involving hovercraft worldwide. In the larger one, the hull of a Saunders Roe Nautical 4 hovercraft was pressed against a quay wall, causing four people to die through a hole in the outer skin. In the second case, a hovercraft capsized in rough seas, so the rescuers decided to split the hull. As a result of this action, the hull filled with water, killing five people.
In September 2012, on the occasion of the Hovercraft World Championship in the Formula 2 class in Thuringia , a 54-year-old pilot was killed and two other drivers were injured after several boats collided.
See also
Web links
swell
- ^ A b Liang Yun, Alan Bliault: Theory & Design of Air Cushion Craft . 2nd Edition. Elsevier , 2005, ISBN 0-340-67650-7 , pp. 2, 7 ( books.google.de - reading sample).
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- ↑ MV-PP10 Hovercraft Oita-Beppu-Airport ferry in Kunisaki, Japan (# 2). June 27, 2006, accessed May 24, 2020 .
- ↑ Transport without borders. DELU GmbH, accessed on May 24, 2020 .
- ↑ The air cushion grandstand. Retrieved May 24, 2020 .
- ↑ Air cushion train - idea. Retrieved May 24, 2020 .
- ↑ Aérotrain et Naviplanes - Le Terraplane BC4. Retrieved May 24, 2020 .
- ^ Fatal accident in Thuringia. Police are investigating. In: Berliner Morgenpost -online , accessed on September 15, 2012.
