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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 (92106m) 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 takeoff 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