George Files

Ground Effect Vehicles, Ekranoplans and GEVs of the past.

The Cold War and its accompanying arms race between the United States and the USSR have left us a world of military development history to follow, and the subsequent abandonment of many projects by the USSR after its collapse leaves me, at least, with this rather sad feeling. In any case, one of the most interesting projects (and my personal favourite) was the ekranoplan which was a type of aircraft that utilised an aerodynamic phenomenon called “Ground Effect”.

What is Ground Effect?

Basically, what Ground Effect does is it increases the lift to drag ratio of the aircraft when it is within a certain distance of any plane surface. Most sources quote this distance to be somewhere around a fourth of the wingspan of the aircraft. It occurs when the wing’s close proximity to the ground causes an increase of pressure (sometimes called a ‘ram effect’) underneath the wing which acts similiar to an ‘air cushion’. In addition, in usual flight at higher altitudes, trailing vortices are formed at the wing tips of an aircraft which reduce lift. As the aircraft gets nearer the ground these vortices have less space to develop and are less well formed. At ground effect heights the formation of these vortices is constricted and so lift is increased.

To sum up, Ground Effect is caused by:

• High pressure between the Wing and plane surface.
• Trailing vortices at the wingtip being blocked from forming fully.

Usage in the Past:

During the Second World War, pilots who found that they were running low on fuel or who had lost engine power partially flew very close to the ground to economise on fuel. It is unlikely that they knew of the Ground Effect though.

Back in the 1930s, the Dornier Do-X, the largest aircraft of the time was touted as a flying boat (flugschiff) and claimed to be a massive seaplane. However, the only way the Do-X could cross the Atlantic all the way in the air was if the pilots kept the hull just above the wavecrests. It is likely that they were taking advantage of Ground Effect at that height. This is a perfect example of how Ground Effect could be used.

In 1947, the massive (largest wingspan of all time) Hughes H-4 Hercules only ever flew once, at a height of 20 m. At this height (less than a fourth of its 97 m wingspan), the Hercules would have been experiencing Ground Effect and many critics say that it did not indeed have the power to accomplish normal flight. It also featured in the movie The Aviator which had more people actually checking out the real Spruce Goose.

And then there were

The Ekranoplans

Ah, lovely things, positively beautiful and with a fascinating story to tell involving top-secret plans, failed designs, rare sightings and development stalled by halted funding. The ekranoplans were planned as Wing-in-Ground-Effect aircraft (WIGs) and there was a whole set of them. A couple of them were:

The KM

The KM is probably the best known ekranoplan and is nearly always mentioned when the topic comes up.
Dubbed the Caspian Sea Monster by Western Intelligence (who could never figure out what it was) when they saw it there, and shaped like some clipped-off model plane, this titanic craft (more than 300 feet long) came into being some time in the 60s. That’s 540 tons of metal travelling at more than 400 km/h at a height just a few multiples that of a human. Unfortunately, the last of this kind crashed in 1980, the same year that R.A Alexeev, their designer, died.

The Lun

Ah, the Lun, fearsome anti-ship cruise missile bearing defender of the ‘motherland’. Only one Lun was ever made, because funding was cut after the first was produced. Marshall Ustinov’s (he was the Defence Minister) death was the end of the golden run for the ekranoplanes and even though the Alexiev Design Bureau still proposes designs for civilian use, none of them has been put into use. It entered into service back in 1987 and you can still see one docked in Kaspiysk at 42°52′54″N, 47°39′24″E (try Google Earth). Faster than any ship, they were intended to counter American missile cruisers but they never did participate in a conflict.

A-90 Orlyonok

The Orlyonok was not quite in the league of those other two size-wise (only 110 tonnes to the others’ 500 tonnes) but it had a useful purpose, troop transport and naval assault and it probably could have served this well. It could carry a payload 15 tonnes, 2000 km at more than 400 km/h and would probably have been quite the ultimate troop transport. Originally, there were supposed to be 120 of these produced, though eventually when the funding problem hit there were only 4 made. Of these, atleast two are at Kaspiysk now with no attempt made to keep them serviceable. They can be seen at 42°52′50″N, 47°39′57″E in Google Earth. You can also see more photographs of these here.

If that was interesting, you should visit the following pages which talk about these planes in detail:

• Alexeev’s Ekranoplans
• Some Russian ekranoplans
• SE Technology’s WIG page
• Ekranoplans, in Russian

Perhaps I’ll post about WIG craft currently in use next, and ones planned in the future, after that.

And marc: So there!

Posted by roshan.george under Musings, Tech |