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Ekranoplan — big mover flying fast and low

1 July 2015

55° 51′ 06″ N / 37° 27′ 22′ E

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) nose beaching gear — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) — copyright and photo by Макс Климов (Max Klimov)

Макс Климов (Max Klimov) from Moscow is a contributed significantly to this post. The text below is his as are the copyrighted images presented in this post. Here are the thoughts and perspective of Russian citizen about this remarkable Russian craft:

The ground effect is known to the aviators from the very beginning of the aeronautics era. It results in the increased lift force and decreased aerodynamic drag that an aircraft’s wings generate when they are near the surface. Early pilots encountered difficulties on landing due to ground effect, since airplane control became complicated in the proximity of the Earth—controls often crossed. Generally, the better was the aerodynamic quality of the airplane, the stronger was the influence of the “air cushion” between wings and ground or water surface. From the aviators’ point of view the effect was often considered harmful and was just taken into consideration in the landing sequence and was initially not researched well.

In USSR interest for ground effect returned after WW II in the construction bureau headed by Rostislav Alexeyev that was developing high speed marine vessels. A floating vessel’s speed is significantly affected by viscous friction with the water. In order to minimize friction it was necessary to minimize hull to fluid contact. First came hydrogliders with only aft part of the body immersed into water. Then followed the hydrofoil vessels that had only foils in contact with liquid when the vessel was at speed. But their top speed was still limited: cavitation disturbed the lift created by the foils as they moved through the water at speed above 70 mph, bending or even destroying the foil. And so there came an idea to create a boat that had no contact with water at all! Alexeyev with his team performed profound research of the “harmful” ground effect and found it to be really useful. The scale models were able to glide on a low altitude for a long distance over a relatively flat surface, no matter was it water or ground. After long sequence of experiments several experimental full sized crafts were produced which were presented to the state commission.

These impressed Khrushchev as well as the military authority so the bureau achieved state funding for further research and development. There were numerous problems to solve. One of the hardest was to create the construction as light as an aircraft, but as durable as a ship — and able to withstand wave impacts at speeds of 300 mph. Finally in late 60-s the huge prototype ship “KM” was built. It was about 100 meters long with a 40 meter wingspan. Spotted by US military satellites it became known in western press as the “Caspian Sea Monster.” The KM was determined to have an optimum (fuel efficient) cruising speed of 267 mph, and a maximum operational speed of 311 mph. Maximum speed achieved was 404 mph, although some sources claim up to 460 mph. KM was tested at the Caspian Sea for 15 years until it was lost in 1980 due to pilot error. In parallel there were developed two branches of military purpose ground effect vehicles (or GEVs): naval missile-carrier called “Lun” and amphibious personnel-carrier “Orlyonok” (Eaglet).

[Thank you Max]

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) forward fuselage showing radar dome, cupola (originally a dorsal gun turret) and exhaust from the starboard Kuznetsov turbofan — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) forward fuselage showing radar dome, cupola (originally a dorsal gun turret) and exhaust from the starboard Kuznetsov turbofan — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hull view — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hull view (note the large air intake for the starboard turbofan) — copyright and photo by Макс Климов (Max Klimov)

Designer Rostislav Evgenievich Alexeyev specializes in ground effect vehicles (ekrnoplan) in the Central Hydrofoil Design Bureau. This class of vehicles are generally considered maritime, not aircraft, but they follow aerodynamic principles quite closely nonetheless. This A-90 Orlyonok (Eaglet) is Alexeyev’s medium sized vehicle entry into ground effects vehicle military transport as well as assault vehicle. Large enough to carry 150 troops or 28,000kg/61,730 pound of cargo is impressive — being able to surprise assault from over the horizon at over 400kph/~250 mph is terrifying to shore installation defense commanders since reaction time once seen would be a matter of a few minutes.

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) cockpit windscreen — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) cockpit windscreen — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) view forward — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) view forward — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hull form detail — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hull form detail — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hull swinging joint detail — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hull swinging joint detail — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) inboard starboard wing flap detail — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) inboard starboard wing flap detail — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) wing flap hinge — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) wing flap hinge — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hatch — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) hatch — copyright and photo by Макс Климов (Max Klimov)

Flight power is handles by an immense single Kuznetsov NK-12MK (152kN/~34,000 lbs thrust) turboprop driving contra-rotating propellers while ground effects power is augmented with a pair of Kuznetsov NK-8-4K turbofans (103kN/~23,000 lbs thrust each). The turbofans direct thrust downward underneath the wings and full-span flaps. This is termed power augmented thrust in the industry. The turboprop is the most powerful one available in the world and cannot only propel the A-90 to medium speeds but up to a height of 3000 meters (~9800 feet). The Orlyonok’s range is equally impressive at 1500km (~930 miles).

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) huge Kuznetsov turboprop — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) huge Kuznetsov turboprop — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) profile of the contra-rotating propellers — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) profile of the contra-rotating propellers — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) starboard Kuznetsov turbofan exhaust — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) starboard Kuznetsov turbofan exhaust — copyright and photo by Макс Климов (Max Klimov)

Crewed by six the A-90 could bring cargo such as a platoon or an armored personnel carrier to a remote shore or recently captured airfield, swing the A-90’s nose to the starboard (right) side and be on its way — noisily perhaps but speedily.

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) vertical stabilizer and rudder assembly — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) vertical stabilizer and rudder assembly — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) starboard wing sponson — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) starboard wing sponson — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) swinging nose-fuselage hull joint hinges — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) swinging nose-fuselage hull joint hinges — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) main beaching gear — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) main (L) and nose (R) beaching gear — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) nose beaching gear — copyright and photo by Макс Климов (Max Klimov)

Central Hydrofoil Design Bureau A-90 Orlyonok (Eaglet) nose beaching gear — copyright and photo by Макс Климов (Max Klimov)

[Thanks again Max]

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