45 thousands of settlements in which more than 12 million people live, are deprived of year-round access to transport infrastructure. In five regions, there is no railway connection, and in 14, only by plane or helicopter can you reach the mainland. At the same time, today there are half as many airports as at the end of the 80s. An analysis of the situation shows that regional airlines need an aircraft with a capacity of 50 – 60 passengers, capable of operating in difficult conditions and capable of landing and taking off from unpaved airfields.
Distances between the airports of the Far North, Siberia and the Far East average 1200 kilometers, and then the economy takes over: to use helicopters to transport people and goods with their speeds and range becomes very expensive. And airplanes on local airlines will not be able to provide the entire volume of air travel, because the airfield network has fallen into disrepair.
Heavenly slug
Helicopters - transport medium speed and short distances. One of the advantages over airplanes is use where the latter cannot land and take off. The level of excellence of both the helicopter and the aircraft to achieve the required values of speed and range in terms of economic feasibility can be estimated by aerodynamic quality (K). In modern transport and passenger helicopters, Kmax is reached at speeds of 230 – 240 kilometers per hour and is within 5 – 5,5 units. The subsonic IL-86 and Tu-154 Kmax is 15, and the IL-96-300 - 19.
Aerodynamic quality (the ratio of lift to frontal resistance in a continuous coordinate system at a given angle of attack) is about three times less for transport-passenger helicopters than for aircraft of similar purpose, and is achieved at lower (two to three times) speeds. The greater the cruising speed, the higher the fuel efficiency, the farther the flight distance and the lower the cost of the flight hour.
The weight of an empty helicopter is about 17 percent more than an airplane of the same category as it. This is because the transmission of torque from the engine to the rotor and balancing its reactive torque requires a relatively heavy, cumbersome and expensive transmission.
The overhead costs of engine power to ensure the operation of the transmission and its systems amount to about four percent, to balance the rotor torque of the rotor - up to 10 – 12 percent. Therefore, the weight of the payload and fuel by helicopter is significantly less than that of an airplane.
The main criterion for the profitability of air travel is the cost per ton and passenger-kilometer. It depends on the cruising speed and the corresponding values of aerodynamic quality and flight range. According to these indicators, the helicopter is significantly inferior. But it has significant advantages over the aircraft: to land and take off vertically, hover over the landing area, fly at low speeds.
The new domestic passenger Mi-38 develops 275 kilometers per hour. Exceeding the threshold in 300 kilometers per hour is accompanied by an intensive growth of the core and wave resistance of the rotor blades, to overcome which will require first a significant and then unacceptable increase in the power of the power plant. There are other factors that do not allow to achieve a significant increase in the speed of the helicopter.The range of the Mi-38 with the maximum number of passengers with standard reserve and aeronavigation fuel reserves per 30 minutes reaches approximately 500 kilometers. All possibilities for increasing the cruising speed and the corresponding indicators of aerodynamic quality and flight range are almost exhausted.
Hence a simple conclusion: existing both domestic and foreign helicopters are unable to provide air services in areas of the country with an undeveloped aerodrome network.
However, in aviation companies of the world do not give up hope to bring a high-speed helicopter to the light. Firms in the US and Europe are conducting expensive research trying to come up with the possibility of creating a car that can develop up to 500 kilometers per hour. Russian Helicopters JSC joined this race with the concept models of the promising Ka-92 and Mi-X1.
The outstanding domestic helicopter designer M. L. Mil and his colleagues back in 1966 year, justified the maximum speed capabilities of the helicopter ("Helicopters. Calculation and design. Aerodynamics"). Nevertheless, at two international exhibitions HeliRussia, representatives of domestic design bureaus demonstrated concept models of their promising passenger cars. It was decided that the Mil Design Bureau should concentrate on the development of the project of the classic single-rotor scheme of the average weight category B-37 with a cruising speed of 350 – 370 kilometers per hour. And the Kamov Design Bureau will continue research work on the creation of a flying laboratory for the development of technical solutions when creating a high-speed coaxial helicopter. It is planned to confirm the cruising speed of 350 – 370 kilometers per hour on the B-37 and acceptable values of aerodynamic quality and flight range on an experimental helicopter with a small wing, created on the basis of the Mi-24K.
A new generation of specialists - B-37 developers are advancing on the same rake as their predecessors on the Mi-6 helicopter, who were trying to achieve high values of cruising speed and flight range.
The wing of the Mi-6 is of small elongation, and in the presence of a wing that slightly relieved the rotor at high flight speeds, the level of vibrations was quite high. In this regard, on serial machines, in order to avoid exceeding the vibration norms, the cruising speed of flight was limited to 250 kilometers per hour. This is despite the fact that the world speed record was set on the Mi-6 - 340 kilometers per hour.
Therefore, achieving a cruising speed of 350 – 370 kilometers per hour on the B-37 is unrealizable. This helicopter can only repeat the achieved result.
Screw is preparing to jump
For the Far North, Siberia and the Far East, the high cruising speed of the helicopter itself is not a priority, but the practical flight range and reasonable airfare. The B-37 helicopter clearly does not have such characteristics. And will not possess.
But the transport problem needs to be solved, and it must be technically sound and economically viable. It is worth remembering the autogyro, which was the forerunner of a helicopter - the undeservedly forgotten creation of the Spanish engineer Juan de la Sierva.
The general thing that an autogyro has to do with a helicopter is a bearing screw. The difference lies in the fact that the rotor at the helicopter is driven from the engine through a gearbox and creates both lifting and pulling force during flight, which provides it with forward movement. Necessary for the flight of the gyroplane creates a propeller-driven installation with a pushing (pulling) propeller, and the lifting force is a mooring rotor driven by the energy of the oncoming air flow.
Autogyro compared to the helicopter best uses the power of the power plant to create lift and thrust. He has no power losses on the rotor drive in flight and balancing its reactive moment.
All autogyros can be attributed to three types: winged, wingless and with a jump take-off. Over time, the designers preferred the second type. At low flight speeds, the main rotor was not inferior to the wing in creating lift. Consequently, it complicated the construction of the autogyro, increased its harmful resistance and the weight of the empty vehicle.
In the third type, the main rotor at the minimum pitch was unwound to the specified rotational speed using a mechanical transmission coupled with the engine. The required torque is about 40 times less than that of a helicopter of the same weight category at hover. Therefore, the weight of the transmission on the autogyro is about two percent of the empty vehicle. The helicopter, we recall, 17 percent. After promotion of the rotor of the autogyro at the start, before the take-off, this transmission is turned off.
Attention is drawn to the simplicity of the design of the autogyro and its technical operation. Unlike a helicopter, there is no gearbox and other units and transmission elements for transmitting torque in flight from the engine to the rotor. The listed units are highly loaded in flight, have a limited resource, require constant monitoring, maintenance, and periodic replacement during operation.
Having flashed a number of unsurpassed qualities, autogyros gave way to airplanes and helicopters, which had other capabilities that were primarily demanded by the military.
Now there is a certain interest in autogyros. The modern level of scientific knowledge and mastered technologies allows us to take the next step towards the creation of a combined aircraft (CLA) with an autorizing rotor and wing having increased cruising speed and flight range compared to a helicopter. The autogyro with jump take-off can be considered as a prototype of the passenger KLAH. It provides take-off and landing without run.
Attempts to create a passenger combined-wing rotary-wing aircraft with vertical takeoff and landing on the basis of the helicopter rotor and the wing of the aircraft (rotary-wing) did not succeed. The combination of a helicopter rotor + wing was practically unrealizable due to its structural complexity and high cost.
The idea of creating a passenger spacecraft with a takeoff-landing without run-up on the basis of an auto-rotor rotor-type propeller type and an airplane wing hitherto remained unclaimed.
The high-speed, long-range KLA differs from all existing vehicles and numerous projects using a number of key ideas. Its carrier system includes an aircraft wing, thrusters, and a gyro-type rotor. For its rotation uses the energy of the incoming air flow.
Recall that the aerodynamic quality of the wing of the aircraft at cruising speed is significantly higher than that of the rotor. That is why in the forward-looking KLA, preference for creating lift at high speeds should be given to the wing. To do this, it is enough to unload the rotor by reducing the overall pitch and frequency of its rotation.
When designing, the main rotor SC is optimized for take-off and landing without run-up, and the wing is designed to create the necessary lift that balances the weight of the aircraft and to achieve the maximum aerodynamic quality. The implementation of these ideas will provide twice the cruising speed and tripled range when transporting the same cargo compared to modern helicopters of the same purpose and weight.
Of particular note is the high flight safety of spacecraft. Such a device, like a gyroplane, has good stability and controllability; its piloting technique is simple. It is much more reliable on take-offs, landings and maneuvering in the air, it is insured against such critical flight modes as stalling or spin.
Attention should be paid to the high reliability of the autograting rotor. It operates in more favorable conditions for variable loads and vibrations than in a helicopter. The rotor of the combined aircraft is maximally loaded during takeoff and landing. At speeds over 100 – 120 kilometers per hour, his work is greatly facilitated.
Main rotor blades, made of polymer composite materials, and their bearingless attachment to the hub provide the rotor with a resource comparable to an aircraft wing.
The high reliability and safety of using autograting rotors on autogyros shows statistics. So, by 1933, the 130 autogyro transported tens of thousands of passengers over a distance of more than 4 000 000 kilometers, their total flight time was 35 000 hours. For ten years of operation of serial machines there was not a single catastrophe, which is a record flight safety.
Combination of merits
Helicopters and airplanes do not compete, but complement each other's capabilities. But there are areas where the use of both is either economically unprofitable, or it is impossible to practically purely. Consequently, a KLA is needed, which has all the advantages of a helicopter and an airplane. He will not compete with them, and replace these machines where they are unable to perform long-overdue tasks.
The combined aircraft is distinguished by a carrier system, which includes an aircraft wing and an autotizing rotor-bearing autogyro type propeller. In essence, it is a hybrid of an airplane and an autogyro, which uses a new way to take off without a takeoff. After the launch of the main rotor at the start, a vertical lift of the vehicle is carried out until the landing gear wheels leave the platform by increasing its overall pitch. At the same time, the pilot moves the engines to the take-off position in order to create the maximum thrust force of the propellers (screws of variable pitch) so that the run on the take-off is short. The aerodynamic qualities of the spacecraft and the short take-off / landing aircraft are commensurate.
Unlike helicopters, KLA's are able to provide communication with a maximum passenger load at a distance of up to 1400 kilometers, and in regions with poor transportation infrastructure, up to 700 kilometers from the base aerodromes, without refueling.