In 1996, a closed joint-stock company "KOMETEL" was organized for the development of ekranoplanes. The result of the joint work with the Central Research Institute "Kometa" and the leading enterprises of the aviation industry of Russia was the experimental EL-7 "Ivolga" ekranolet. It should be clarified here that, unlike an ekranoplan, ekranoplanes (this classification was first introduced by R. L. Bartini) are capable of flying not only near the interface between two media, but also outside the zone of action of the underlying surface.
Factory flight tests of EL-7 took place from September 1998 to December 2000 in the waters of the Moskva River and Irkutsk Reservoir. The following year, the Verkhne-Lenskoye River Shipping Company began operational tests of the vehicle at the Angara River and Lake Baikal.
For the first time, information about the EL-7 aerial vehicle was presented at the International Exhibition "Rescue Means-2000". The prototype of the aircraft was publicly demonstrated at the international exhibition "Transport of Siberia-2000", held in Irkutsk (awarded with a diploma of the exhibition), and then at the international aviation and space salon "MAKS-2001". At the exhibitions, the unusual car was of great interest to visitors, including specialists, heads of transport enterprises of various departments and law enforcement agencies.
The ekranolet is designed to carry 8-11 passengers or small cargoes mainly over the water surface of rivers, lakes and seas, including those covered with ice in regions with an undeveloped road network. It can be used over snowy plains and wetlands. The use of the device for tourist and excursion walks, solving patrol, rescue and other tasks is provided.
The main flight modes of the Ivolga are realized at altitudes from 0.2 to 2 m. Due to the use of the effect of proximity to the ground, the device is a highly economical vehicle.
The screen effect is manifested in the formation of a dynamic air cushion between the wing and the underlying surface. As a result, the aerodynamic lift increases, the aerodynamic resistance decreases when moving at heights below the average aerodynamic chord of the wing, and, as a consequence, the aerodynamic quality increases.
"Ivolga" is made according to the "composite wing" scheme with a single-fin T-shaped tail unit. The wing consists of a center section of a very small aspect ratio with a swept trailing edge and folding consoles of large aspect ratio attached to it (borrowed from the Yak-18T aircraft). This made it possible not only to reduce the size of the hangar rooms, but also to use the existing berthing facilities on water bodies, to moor close to ships and make the apparatus more maneuverable in narrow and loaded waters.
In the middle part of the all-metal center section, there are upper and lower aerodynamic flaps, which, together with displacement floats, form a reversible brake chamber that allows you to regulate the mileage of the machine.
The power plant is located in the center section, and in the fuselage, made in one piece with it, there is the pilot's cabin and the cargo-passenger compartment. The latter are closed with a common streamlined lantern.
On the bow of the hull there is a pylon with two propellers in annular channels. Connected by cardan shafts with engines, they, depending on the mode of movement, can change the direction of the thrust vector.
Against the background of solving the most complex issues of stability and controllability, the creators of an aerospace aircraft are always faced with the task of choosing a takeoff and landing device. The amphibiousness of the vehicle and its thrust-to-weight ratio also depend on this. After all, it is no secret that the peak of the required thrust of the power plant falls on overcoming the hydrodynamic resistance during the takeoff run.
In this regard, the EL-7 used blowing from propellers into the space bounded by the wing center section, the rear center section flap and floats. In this case, the propellers are deflected synchronously with the flaps, but in other modes, their independent deflection is possible.
The static air cushion created in this way ensures non-contact movement with the underlying surface at heights of up to 0.3 m at a speed of up to 80 km / h.
With further acceleration, due to an increase in the velocity head, the direction of the thrust vector of the propellers changes, and the apparatus switches to the dynamic air cushion mode.
Thanks to a similar take-off and landing device, EL-7 acquired amphibious properties with the ability to independently go ashore and launch. When taxiing on an air cushion, the front sub-center flap is released, and the machine can literally turn on the spot.
As you can see from the illustrations, the ekranolet is made according to the catamaran scheme. In this case, the floats are divided into several waterproof compartments, which provide the necessary buoyancy in the event of damage to one or more of them. Easily removable floats allow operation not only from water, but also from ground, swampy and ice areas.
Easily detachable connections of the airframe units allow transporting the ekranolet without dismantling the power plant by Il-76, An-12 aircraft, on railway platforms and trailer vehicles.
Aluminum alloy AMG6 and fiberglass were used as the main structural materials, allowing long-term and year-round operation of the Ivolga in river and sea conditions.
The frame of the canopy and saloon is plastic. The triplex windshield is equipped with a mechanical wiper (such as car wipers) and an electric heating device.
The propeller ring nozzles increase their thrust at low speeds, protect from foreign objects and prevent others from falling into the rotating propellers, and reduce the noise level on the ground. The propeller rings are made of plastic, with metal load-bearing elements for fastening them to the swing beam. As already noted, in the starting position, the air jets from the propellers are directed under the center section, in cruising - above the center section.
The ekranolet is equipped with two automobile engines, which are placed separately in the right and left center section compartments. Each of the engine blocks, in addition to the engine with clutch, gearbox, muffler-resonator and other units, includes a fuel tank. The volumes of the engine compartments allow the placement in them of other types of engines, including diesel and aviation, with sufficient power. Moreover, their dimensions will not distort the outer surface of the center section.
The EL-7 is equipped with the necessary set of flight and navigation equipment, including a JPS-type satellite navigator. In addition, there are power supply, lighting and external alarm systems, ventilation and heating systems for the passenger compartment and engine compartments, and fire extinguishing systems. Marine equipment and life-saving appliances have also been installed.
The radio equipment meets the requirements of the River Register of Russia for ships with small displacement and provides reliable radio communication with ships and ground points using shortwave and VHF radio stations.
The deflections of the elevator and ailerons are carried out, as on airplanes, using the steering column, and the rudder - using the pedals. Trims on the elevator and left aileron and a rudder trimmer-servo compensator are used to relieve loads from the steering wheel and pedals.
In addition to the rudder, you can control the device along the course by changing the speed of the engines or the pitch of the propellers, disabling one of the propellers by means of the clutch, as well as deflecting the sections of the rear shield with electric deflectors on the pedals.
The length of the run, if necessary, can be changed by releasing the flaps of the reverse brake chamber.
Tests of the EL-7 began in Moscow in September 1998 with the development of the control system when driving on the water, including the air pressure mode. At the same time, the available thrust and aerodynamic unloading of the vehicle were determined using the blowing and blowing of the center section in the parking lot.
In January 1999, the ekranolet was loaded into the Il-76 and relocated to Irkutsk, where it was tested in the conditions of the Siberian winter. The first flight using pressurization was performed at the Irkutsk reservoir on February 16. Four days later, V. V. Kolganov on EL-7 with ZMZ-4062 automobile engines with a capacity of 150 hp each. tested the screen mode in a cruising configuration (shields removed, propellers in cruising position) at a speed of 80-110 km / h.
Having made sure that the ZMZ-4064.10 turbocharged engines (210 hp each) are not expected in the near future, and the power of the ZMZ-4062.10 is not enough for flights with a load, BMW S38 automobile engines were installed on the ekranolet.
With BMW 20 (or S38) engines, in August 1999, V. V. Kolganov demonstrated the descent of the car into the water using airflow, flight near the screen in a cruising configuration, followed by going ashore.
Since December 1999, D. G. Scheblyakov has mastered the piloting of the ekranolet, who soon demonstrated flight at an altitude of up to 4 m with maneuvering along the course. Five days later, the device rose to a height of over 15 m and demonstrated its capabilities in flight outside the coverage area of the underlying surface.
The tests were quite successful, and in February 2000 the first long-range flight took place. Flying over the waters of the Angara (at a distance of 10-12 km from the source from Lake Baikal, the Angara does not freeze) and the ice of Lake Baikal in screen and airplane modes, EL-7 successfully demonstrated its capabilities. In the fall of 2000, the device confidently took off from the water and landed on waves more than a meter high (3 points).
The test results of the prototype confirmed the efficiency of the technical solutions incorporated in the Ivolga. Possessing good stability in the entire range of flight altitudes, including 5-10 m, where the ground has almost no effect on the aerodynamics of the machine, the EL-7 proved to be easy to control and forgave even gross errors in piloting.
During the tests, it was possible to work out the technique of piloting when maneuvering along the course, speed and altitude in flight both with the use of blowing and in the screen mode. "Airplane" flight modes have been tested.
The turns near the ground were carried out with a roll of up to 15╟ at heights starting from three meters and until the exit from the ground effect zone (more than 10 m) with a roll of up to 30-50╟. The thrust of the power plant with BMW S38 engines was enough to continue the screen flight in the event of a single engine failure. When moving near the interface between two media, the aerodynamic quality of the EL-7 "Ivolga" aerodynamic aircraft reached 25, which is more than two times higher than the analogous parameter of aircraft of this class.
In turn, this significantly increases the range when flying at low altitudes with the same take-off weight and fuel reserve. The average fuel consumption when flying at a speed of 150-180 km / h on a route with a variable profile and maneuvering along the course and altitude did not exceed 25-35 liters of AI-95 gasoline per 100 km of track with a take-off weight of 3700 kg and 8 passengers. In the "airplane" mode, the consumption reached 75-90 liters.
Flying at heights of up to three meters, the EL-7 ekranolet is certified in the River and Marine Registers. The good flight characteristics of the device allow, when equipped with aircraft engines, equipment and flight and navigation systems, to certify it according to the aviation register, including aircraft flight modes. In this case, the ekranolet will have flight data at the level of aircraft of a similar dimension. It will retain the ability to operate from unprepared ground areas, ice, deep snow, water, including wetlands.
The ekranolet is highly environmentally friendly - when basing it practically does not violate the top layer of soil and grass cover, in the process of movement it does not touch water and does not leave waves, and in terms of noise and toxicity it is comparable to a car. The absence of heaving and bumping due to the temperature uniformity of the underlying surface and the absence of vertical gusts of wind, low noise level in the cockpit and on the ground, good visibility make the flight comfortable and enjoyable.
At present, the employees of CJSC "COMETEP", Verkhne-Lensky river shipping company and other organizations are united into CJSC "Scientific and production complex" TREC ". test results of the predecessor At the same time, the production of EK-25 ekranoplanes, designed for 27 passengers, is being prepared.
These safe, highly economical and environmentally friendly amphibious vehicles, capable of moving at altitudes from 0.2 to 3 m at a speed of up to 210 km / h with a range of up to 1500 km, are designed for year-round operation with a high economic effect on rivers and reservoirs, including and covered with ice and snow, over wetlands. High seaworthiness (3-4 points) will make them irreplaceable on coastal shipping lines.
