An ekranoplan (Russian: экранопла́н, literally "screen plane") is a vehicle resembling an aircraft but that operates solely on the principle of ground effect (in Russian эффект экрана effekt ekrana - from which the name derived). Ground effect vehicles (GEV) fly above any flat surface, with the height above ground dependent upon the size of the vehicle.
The "Caspian Sea Monster" model KM ekranoplan
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 US intelligence operatives who had spotted 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 one of several Soviet military designs meant to fly only a few meters above water, saving energy and staying below enemy radar.
The KM, as the Caspian Sea Monster was known in the top secret Soviet military development program, was over 100 m long (330 ft), weighed 540 tonnes fully loaded, and could travel over 400 km/h (250 mi/h), mere meters above the surface of the water. Another model was the Lun-class. The ekranoplan has a lifting power of 1,0 tonnes, among the largest ever achieved.
The important design principle is that wing lift is reduced as operating altitude of the ekranoplan is increased (see ground effect). Thus it is dynamically stable in the vertical dimension. 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, though flight over land would have involved extreme risks unless the surface were very dependably flat.
These craft were originally developed by the Soviet Union as very high-speed 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. The development of ekranoplans was supported by Dmitri Ustinov, Minister of Defence of the USSR. About 120 ekranoplans (A-90 Orlyonok class) were initially planned to enter military service in the Soviet Navy. The figure was later reduced to fewer than thirty vehicles, planned to be deployed mainly for the Black and the Baltic Soviet navies. Marshal Ustinov died in 1985, and the new Minister of Defence Marshal Sokolov effectively stopped the funding for the program. The only three operational A-90 Orlyonok ekranoplans built (with renewed hull design) and one Lun-class ekranoplan remained at a naval base near Kaspiysk.
Since the fall of the Soviet Union, ekranoplans have been produced by the Volga Shipyard in Nizhni Novgorod located at 56°21′58.08″N, 43°52′14.26″E.
As of 2006-09-06, two ekranoplans could be seen on Google Earth at Kaspiysk, The Lun, located at 42°52′54″N, 47°39′24″E and an Orlyonok at 42°52′50″N, 47°39′57″E. A structure on a nearby beach may be a third disassembled ekranoplan.