An ekranoplan (Russian: экранопла́н, literally 'screen plane') is a ground effect vehicle resembling an aircraft. They operate on the principle of the ground effect. This effect can be felt when landing in a commercial air liner; just before touchdown, the angle of descent can be felt to decrease. Ground effect vehicles skim just above a flat surface, with the height being dependent upon the size of the vehicle.

During the Cold War, ekranoplans were sighted for years on the Caspian Sea as huge, fast-moving objects. The name Caspian Sea Monster was given by confused U.S. intelligence operatives who were puzzled by the huge vehicle, which looked like an airplane with the outer halves of the wings removed. After the end of the Cold War, the "monster" was revealed to be a secret airplane of the Russian military, designed to fly only a few meters above water, thus saving energy and staying below enemy radar.

The KM, as one model was known in the top secret Soviet military development program, was over 100 m long, weighed 540 tons fully loaded, and could travel over 400 km/h mere meters above the surface of the water. Once moving at speed, the ekranoplan was no longer in contact with the water, and could move over ice, snow, or level land with equal ease.

The important design principle is that the wing lift reduces the further above the surface (land or sea) the ekranoplan "flies" (see ground effect). Thus it is dynamically stable in the vertical dimension.

These craft were originally developed by the Soviet Union as very high-speed (several hundred km/hour) military transports, and were mostly based on the shores of the Caspian Sea and Black Sea. The largest could transport over 100 tonnes of cargo.

Since the collapse of the Soviet Union, commercial development has occurred mostly in the United States.

External links

• WIG boats - application of Wing-In-Ground effect
• [1] - A short overview of Soviet ekranoplan creation and development
• [2] - Rostislav Evgenievich Alexeev. An outstanding designer of highspeed ships
• [3] - Check "Ekranoplane" on the left bar. Lots of pics, several videos. (in German)