WIGs Wing in Ground-effect

WIG VT-01 In Extreme Ground Effect

Two Russian Orlyonok WIG Boats

What is a WIG? WIG is an abbreviation of Wing In Ground-effect. A WIG boat can be seen as a crossover between a hovercraft and an aircraft. It flies just above the surface, usually the water surface; therefore others use the term WISE or WISES (Wing In Surface Effect Ship). The Russians use the word Ekranoplan (Ekran = screen, plan = plane), which is also commonly used in other languages nowadays.

How WIGs Work! A hovercraft is floating on a cushion of air that is created by a fan that blows in a cavity under its hull. The cavity is bounded by so called skirts, rubber balloons that restrict air leakage and more or less seal the cavity. The air cushion reduces the friction drag of the hovercraft with the water which would make it a very efficient vehicle if is wasn't for the fan that creates the cushion. A WIG craft also sits on a cushion of air, but this cushion is created by aerodynamics rather than by an engine.

How WIGs Work, continued… This means that it only exists when the WIG craft has sufficient forward speed. This is called a dynamic air cushion as opposed to the hovercrafts static air cushion. You can compare this to the relation aircraft-helicopter, the aircrafts wings generate lift because of their forward speed, whereas the helicopters rotor has work continuously for generating lift. A more in depth explanation of ground effect aerodynamics can be found at the URL: http://www.se-technology.com/wig/index.php

Soviet WIGs Rocket Launchers 4 Engines per Side

Rocket Away!

The Largest! JSC R.E. Alexeiev Central Hydrofoil Design Bureau

Caspian Sea Monster This largest, ever-built ground effect vehicle was designed in 1963-1964. Construction was completed in 1965. The KM's maiden flight was on 18 October 1966; at that time it had manual controls! The KM provided lots of useful data on large-scale WIG vehicles. Although only one KM has been built, there are many photos of the KM with different tail numbers (1 to 8). The numbers indicate the different test phases; some of the changes to the craft were quite big, like wing span (32-40m) and length (92-106m) variations. The max weight varied from 495 to 540 ton.

Caspian Sea Monster The KM (Russian abbreviation for prototype ship) has a large T-tail with dihedral and surprisingly a mid wing. Eight large turbojets are mounted at the front of the fuselage; the exhausts of these engines could be deflected in order to create an air cushion under the wing (PAR). Two extra turbojets were mounted on the fin in order to provide extra thrust for acceleration. These engines are equipped with spray deflectors. These engines were relocated from the fin to the top of the flight deck in 1979 in order to reduce spray ingestion. All of the engines are Dobryin VD-7 turbojets. The maximum wave height at take-off was 3.5 meters.

Caspian Sea Monster In December 1980 the KM crashed in the Caspian Sea during take off. The pilot tried to lift-off without having 100% take-off power. They tried to recover the KM, but it broke during lift operations. The KM weighed 540 ton (at that time twice the heaviest aircraft). The Americans who saw the secret KM on satellite photo's named it the Caspian Sea Monster (or Casp A).

Caspian Sea Monster

Civilian Application

Line Schematic – Casp-A