It is a transition between a hovercraft and an aircraft.
It is a vehicle that attains level flight close to the surface of the earth which is possible by the cushion of high pressure air created by the aerodynamic interaction between the wings and the surface of the earth generated by its forward movement called as ground effect. It is also known as a flarecraft, sea skimmer, wing in surface effect ship etc.
In the 1970's when this vehicle was first photographed by the American satellite, it was believed to be a normal Jumbo jet sized aircraft under construction but when the vessel was later photographed sitting in water the American’s were puzzled! These crafts are big, fast and were kept secret from the west until the fall of communism in the early 1990's, when information about them was slowly revealed.
It can quite easily be envisaged that a hundred of such crafts zooming across the ocean, flying undetected by the radar as they fly underneath it and invading a country! By the time that country realized what was going on, it would have been too late. The front of the fuselage would have opened to allow soldiers, tanks, trucks, jeeps, and armoured cars to deploy and invade. You have to imagine several hundred of these craft, all flying at over 290 knots, all under radar in a mass invasion. We could then fully realise the element of surprise that they would have had.
It’s one hell of a ship, fast, manoeuvrable, and heavily armed but maybe not so well protected. Unlike a warship that has armor plating, the Ekranoplan would be susceptible to enemy firepower, a couple of rocket or bazooka hits could seriously damage or render the Ekranoplan inoperable. As the Ekranoplan picks up speed, the air is compressed under its short stabilizing wings until enough pressure produces lift and this supports the craft. Ekranoplan's as they are bigger, have more power and travel just a few feet over the water surface. Infinitely faster than any sea vessel ever designed the Ekranoplan is a marvel to behold. The terrific speed that these crafts can reach is mainly due to the fact that there is no friction between the hull of the craft and the water. This of course is a factor that keeps normal ships at such a comparatively slow speed, as they must push themselves through the water and not over it. They have better fuel efficiency than an equivalent aircraft flying at low level due to the close proximity of the ground, reducinglift-induced drag. There are also safety benefits for the people travelling in the craft in flying close to the water as an engine failure will not result in severe ditching. However, this particular configuration is difficult to fly even with computer assistance. Flying at very low altitudes, just above the sea, is dangerous if the craft banks too far to one side while making a small radius turn.
All Ekranoplan's are amphibious and will easily fly over land just as well as the sea, and at high speed, just as long as the surface is relatively flat. The last Ekranoplan from the former Soviet Union was the 400 ton LUN. It was built in 1987 with 100% military application in mind as a missile launcher and troop carrying ship. It was equipped with six large missiles on top of the fuselage, and could carry tanks and trucks in its large cargo hold. Also it must be reiterated here that it would not have been detected by radar as it would have travelled under the radar waves but the modern radar now has the ability to scan vessels on the surface of the sea so the surprise element of the Ekranoplan can be negated.
At the time when the Soviet Union fell apart, there was a second LUN under construction, it was about 90 percent finished when the military funding stopped. This was because of Russia's poor financial situation and also the end of the cold war. Later the eventual collapse of communism was enough to create further financial upheavals in much of Russia's economy. Most countries have now built prototypes of the Ekranoplan design as it has very useful application both in the military and commercial fields. As yet no commercial flights have been instigated but there are reports that a lot of private ventures are being developed, mostly in the USA.