Rotary-wing vehicles of civilian and military purposes are capable of solving tasks inaccessible to any other type of aircraft and modern technology in general. Their main and almost the only drawback is the relatively low speed. The average speed of the helicopter does not exceed 220 km / h. Today, many helicopter builders claim that the time for records has arrived!
Why do helicopters need high speeds?
Both in the performance of military operations and in the implementation of many tasks of a peaceful nature, there are situations where the success of the mission is entirely dependent on the helicopter speed performance. These include:
- Evacuation of seriously wounded and sick from the centers of military operations and inaccessible places to large medical institutions.
- Urgent delivery of specialists (doctors, epidemiologists, law enforcement officers) to the areas of emergency.
- Express delivery of vital (medicines, food, special equipment) and bulky goods to places far from developed infrastructure.
Despite the many advantages of rotorcraft (minimum requirements for landing surface, maneuverability, the possibility of hovering in the air), the speed of an airplane and a helicopter until recently were not comparable.
Helicopter maximum speed
Until recent years, the official speed record for classic rotary-wing aircraft was an indicator of 400.9 km / h, recorded in 1986 by a modified version of the British Westland Lynx multipurpose vehicle. The fact is that, even theoretically, the maximum speed of the helicopter cannot exceed this threshold.
This state of affairs is explained by the fact that at higher speeds, the range of oscillatory movements of the main rotor blades dangerously increases. which in turn leads to a stall of the flow from their extremities. The phenomenon is especially characteristic for azimuths of 270-300 ° (the angle of the blade relative to the longitudinal axis of the machine), i.e. for retreating blades. What design and technological innovations will allow developers to overcome the treasured milestone?
First records
One of the ideas for increasing the speed of a helicopter is to use an additional “pushing” propulsion. This design feature is by no means new. Back in 1967, the creators of the American Lockheed AH-56 "Cheyenne" apparatus installed a three-blade screw in the rear of the machine to increase speed characteristics.
The figure of 407 km / h demonstrated during test flights at that time looked very impressive. For the US Air Force, it was planned to manufacture 375 helicopters, but due to numerous difficulties in serial implementation, the project was closed after the release of only ten aircraft.
Of course, it is one thing to come close to the cherished figure, but quite another - to significantly exceed it.
European hybrid
The next record holder is the X3 Hybrid, developed by the European corporation Eurocopter. First flew up from the site of the military base Istres - Le Tube (France) in 2010. After a year of test flights, the creators managed to bring the helicopter's cruising speed to 430 km / h.
Further improvement of the design and flight performance allowed the European aircraft to set an unofficial speed record for helicopters - 472 km / h for horizontal flight and 487 km / h for dive. Why unofficial? Yes, because the Eurocopter X3 is not exactly a helicopter.
The basis for the creation of the machine was the production model EC155 Dauphin. The designers supplemented the "source" with two gas turbine aircraft engines with pulling screws located on small wings. Thus, the Eurocopter X3 is rather a hybrid of a helicopter and an airplane. The project is in the phase of final test tests and the developers claim that serial production will soon begin.
Some more theory
The use of pulling or pushing screws frees the main rotor from the need to create horizontal traction for the translational movement of the aircraft. Specialists of the American aircraft and helicopter manufacturing company Sikorsky developed the advanced ABC technology (Advancing Blade Concept), in the Russian translation called the concept of the approaching blade.
The essence of the development is that the angle of inclination of the advancing and retreating rotor blades should always provide maximum lifting force. Thus, the rotor can maintain the required flight altitude at a much lower rotational speed. And this is almost the determining factor in increasing the speed of the helicopter.
ABC technology allows the aircraft, even after the disappearance of the lifting rod on the retreating blades, to continue acceleration.
Competition as an incentive
The validity of the concept has already been proven. An experimental helicopter of the Sikorsky-69 concern, equipped with two pushing turbojet engines, showed a maximum speed of 518 km / h.
Helicopter builders on both sides of the ocean are well aware that, ceteris paribus, the manufacturer will be the winner, whose characteristics will have higher speed characteristics.
In addition to the emergence of new technological solutions, modern materials science provides broad opportunities for improving flight performance. Many serial models are already equipped with screws made of composite materials. To reduce aerodynamic drag, the hubs of the screws are covered with fairings.
What speed do helicopters demonstrate today?
Industry leaders
The logical development of the concept of the Sikorsky-69 model was the concern's apparatus, implemented as part of the Sikorsky X2 project. The helicopter significantly increased speed and efficiency, but retained all the advantages inherent in rotorcraft: remarkable maneuverability at low speeds, the possibility of motionless hovering, vertical take-off and landing, and autorotation. Coaxial helicopter cruising speed with one pushing propeller 460 km / h (maximum -474 km / h), range - 1300 km.
The proven technologies were continued in the new generation S-97 Raider helicopter, the model of which with the calculated flight characteristics was presented to the public by the company's designers. The developers claim that the cruising speed of the helicopter will be at least 500 km / h. Units and assemblies of the future leader pass ground test tests. There is no reliable information on the date of the first flight of the American Ryder.
And what about Russian Helicopters?
But what about domestic helicopter builders? We can say that the plans of the Kamov and Mil design bureau employees are no less ambitious. Back in 2013, the leaders of the Russian Helicopters holding initiated a PSV program to develop a promising high-speed helicopter. As part of this project, the specialists of the Plant named after Mile in 2015 presented a demo model of a Rachel helicopter. The speed of the helicopter, according to the assurances of the developers, is not a priority for this model, here for another promising Mi-1X machine it can reach 520 km / h.
“Kamovtsy” nearly a decade ago presented the concept of a very fantastic Ka-90 aircraft. According to the idea of the designers, the helicopter, having reached a speed of 400 km / h with the help of the rotor, folds the blades into a streamlined case, and then the acceleration continues with jet engines. Moreover, the developers do not consider the parameter of 700-800 km / h to be the limit.