Despite the trouble in the competition for the creation of a new attack helicopter, capable of developing great speed, the company «Sikorsky» not done research on the topic vertibird. The main goal of the new research was the decision prepyadstviya motion of the helicopter at tremendous speeds. The fact is that when a certain flight speed of the last rotor blades begin to move at supersonic speed relative to the air motionless. Because of this dramatically reduces the carrier characteristics of the propeller, which could eventually lead to the loss of sufficient lifting force and even tragedy or disaster. Work in this direction has been called ABC (Advancing Blade Concept — Leading concept blades). With the passage of time to the ABC program there was connected to several other companies and organizations.
In 1972, ABC programm reached the stage of creation of the first flight of the layout. By this time, the company graduated from Sikorsky designing experimental aircraft S-69. In order to minimize the effects of the highest speed of the blades relative to the air when flying above the horizontal speed of 300-350 kilometers per hour and the company’s engineers found a comparable conventional and original solution. Vertibirds past, which were built in various countries, most are not equipped with its own vsepolnotsennym swash. It was assumed that such machines should change pitch of all the blades at once and uniform angle. This solution explained the possibility to simplify the design and the presence of additional thrusters providing horizontal flight. But in the course of numerous theoretical calculations and wind tunnel NASA and Sikorsky employees concluded that a similar scheme is outdated and hinders the achievement of large high-speed features. To reduce the effects of the highest speed of the blades had to constantly adjust the iterative step screw, regardless of the current horizontal velocity and, consequently, the disposition of the blades on the flow or another section of the sweeping drive. Because S-69 had quite a swash plate, capable of regulating and collective pitch, and repetitive.
BACKGROUND rotorcraft from «Sikorsky» — S-66 — had a complex system of rotation of the tail rotor, which in flight «helicopter-» offset the torque of the screw rotor, while the horizontal high-speed movement to push the car forward. After a series of detailed examinations, such a scheme has been recognized as a very complex and, as a consequence, hopeless. In addition, to simplify and increase the efficiency of the box of the power plant, it was decided to equip the new S-69 with 2 turbojet engines for horizontal movement. Once this structure was derived from the control screw, and bearing «doubled». As a result, S-69 began to represent a conventional helicopter pine circuit boards mounted with turbojet engines. So Makar, inside streamlined fuselage adapted to a huge flight speeds, located one turboshaft engine Pratt & Whitney Canada PT6T-3 power up to half thousand horsepower. Through a reduction gear he set in motion both rotors. Three-bladed screws were separated vertically by 762 mm (30 inches), and the gap between them was fairing. Along the edges of the fuselage nacelle installed two turbojet engines Pratt & Whitney J60-P-3A with a thrust of 1350 kgf.
Experimental rotorcraft S-69 came comparable small. Fuselage length of 12.4 meters, the diameter of the rotors slightly least 11 meters and a total height of just 4 meters. Noteworthy that S-69 in terms of aerodynamic seriously different from other vertibird: single carrier plane was the tail stabilizer. Effective screw, designed on the concept of ABC, not sought any unloading with additional wings. For this reason, almost ready aircraft was a helicopter ordinary pine scheme with installed additional turbojet engines. In addition, the lack of wings allowed to save some weight. The highest takeoff weight S-69 was equal 5 tons.
First layout S-69 first flew in the air July 26, 1973. Rotorcraft showed good maneuverability hovering and low-speed without the use of turbojet engines. First flight, during which test turbojet engines work, ended in tragedy. Less than a month after the first flight — August 24 — experienced S-69 crashed. Frame and trim rotorcraft were soon recovered, but his speech is no longer flight went. A couple of years later, during a follow-up programs from ABC, the first layout was used as a full-size model of the purge.
Flights second prototype began in July 1975. Following an investigation of the tragedy of the first prototype was substantially modified flight test programm. Until March 77th, the second layout is not only flew only «helicopter-style», and not equipped with turbojet engines. Instead of them to the end of the first step test «incomplete» rotorcraft drove the desired weight of the load. With only one rotor S-69 in flight without turbojet engines was able to reach a speed of 296 km per hour. Upcoming crackdown was dangerous, and in addition, is not necessary in view of the separate propulsion system for the creation of a horizontal thrust. By the end of the 70s, set a new speed record: using turbojet engines second layout S-69 overclocked to 488 km per hour. With all this cruising speed rotorcraft does not even reach 200 km / h, which was justified by the huge consumption of fuel 3 engines running at once.
Usefulness of the ABC system was evident. At the same time, tests revealed a number of shortcomings assist constructive nature. Namely, during test flights prirekany caused many structural vibrations occurred at tremendous speeds flight. The study showed the difficulties that the elimination of this shaking required finishing screws, also some design changes all rotorcraft. In the late ’70s began work on creating a refreshed rotorcraft S-69B. First option, in turn, added to his own name the letter «A».
In the S-69B was converted second layout rotorcraft. During rework with his shot turboprop engine nacelle, installed two new turboshaft engine General Electric T700s 1500 hp each new rotors with new blades and a huge diameter, also seriously pererablotali box. Rotorcraft got refreshed rotor gearbox. In addition, in the boxes introduced separate shaft that went into the rear fuselage. There arranged pusher propeller Ducted. With the new pusher S-69B was able to even closer to the plate speed of 500 km / h But the main premise of the project configuration was still improving the design and development of the latest version of the concept of ABC. Because of the new rotor vibration when flying at certain speeds disappeared in general, and on the other — a significant decline.
In 1982, all tests rotorcraft S-69B completed. Sikorsky, NASA and other organizations have received all the necessary information and the remaining flying layout has been sent to the Aviation Museum Fort Rucker base. First layout injured in testing and used as a purge model stored in Ames Research Center (NASA). Production acquired in the development and testing vertibird S-69, used in the upcoming new projects of similar purpose.
After closing the project S-69 a couple of years left on the next study on ABC and only in the second half of the two-thousand years old and the new generation reached the stage of construction of a new rotary-wing aircraft. Sikorsky X2 project in some measure resembles previous rotorcraft the same office, but the similarity ends in a few details appearance. In developing the new rotorcraft engineers «Sikorsky» repelled by technical form S-69B. For this reason, X2 received coaxial rotor «uzhaty» streamlined fuselage and a pusher propeller tail.
It should be noted that in the development of new rotorcraft, it was decided to make it smallest little than S-69. A prerequisite of this solution was a necessity to work technology without introducing any difficult decisions related to the airframe. As a result, the rotors have X2 diameter of about 10 meters, and the highest takeoff weight does not exceed 3600 kg. With such a small weight new turboshaft engine rotorcraft equipped LHTEC T800-LHT-801 power up to 1800 hp Through an unusual box torque is distributed to the two four-bladed rotor and tail pusher (6 blades). X2 has become the world’s first rotary-wing, gear-wire control system. Through the use of such electronics, machine control has become much easier. After preparatory study and management options Automatic assumes most of the tasks to stabilize flight. The pilot can only submit proper commands and watch the state systems.
Recent achievements coupled with programs from ABC-wire control system have allowed significantly lower vibration, including flying at tremendous speeds. With regard to the aerodynamic form, then X2 has elliptical spinner; shaft between the screws not covered, which is compensated by proper placement rods and other parts. Immediately this rotorcraft got stretched fuselage comparable small section. General assembly of the fuselage went from ordinary X2 helicopter pine scheme. In the front part is a double cabin with jobs pilots arranged one after the other. In the middle part, under the hub, located engine and main gearbox. Up from it go rotor shafts, reverse — drive shaft screw pushing. Fascinating applied system chassis. In the middle of the fuselage, there are two main stands, retractable in flight. Tail wheel retracts into the keel on the bottom of the rear fuselage. Not counting the tail fin of the X2 consists of a stabilizer and 2-endplates. Any wings on the edges of the fuselage missing.
August 27, 2007 hour flight began a four-stage test programm. Like all other vertibirds, X2 first started flying «helicopter-style.» During such operations checked the general properties of the machine. With all of this, in contrast to the same S-69 pilots could not turn horizontal thrust propulsion: control the tail rotor configuration was carried out by his step. This solution was adopted to simplify the structure of the box, which did not introduce divisive clutch. Nevertheless, and without disconnecting the tail rotor pushing X2 showed excellent properties characteristic of helicopters. Since May 2010, there have been reports on the achievement of X2 rotorcraft speed record. First brand new car also achieved the mark of 335 km / h In September of the same year pilot K. Bredenbek X2 sped up to speed of 480 km per hour. It was little lower than S-69, but substantially greater than the greatest rate of at least some of the existing helicopters.
Middle of July 2011 it was officially announced that the project is completed X2. For a total duration of 23 flight about 22 hours were collected unlimited number of disk imaging systems work all rotorcraft, as its aerodynamic parameters. Despite the comparable small program of flight tests, control and recording equipment experimental aircraft has allowed to significantly reduce the time needed to collect all the necessary data. Rotorcraft Sikorsky X2, being first flying laboratory, eventually became the basis for the new project, the same firm that already has a certain practical perspective.
In 2010, the European company Eurocopter announced his own project rotorcraft having experimental purpose. In the course of the project X3 (X3 and other names X-Cube) planned to check their own ideas for acceleration of the aircraft with the rotor to high speeds. Interest is the kind of project X3, in which hardly felt the impact of the American and Russian programs. Practically, Eurocopter X3 is a significantly modified helicopter traditional scheme.
For the base for the new rotorcraft was taken multipurpose helicopter Eurocopter EC155. Holding design of this machine has allowed as soon as possible to design X3 and converted into a serial EC155. During rework native helicopter engines were modified with 2 turboshaft engines Rolls-Royce Turbomeca RTM322 capacity of 2270 horsepower. Engines transmit torque to the unique gear that spreads it to drive 3 screws. Skyward out rotor drive shaft with coupling of separation. Another two shaft crawl to the side and set in motion the two five-bladed propeller pulling placed on special gondolas on the edges of the middle part of the fuselage. These nacelle mounted on small wings. Unlike ordinary EC155, X3 rotorcraft tail rotor not resettled in the annular channel, which resulted in the removal of the structure of the respective actuators. Due to lack of control screw parry reactive moment while the drive rotor by means of the 1st of pulling propellers.
Withdrawal from the construction of the tail rotor drive in terms of weight was offset by new stabilizer with 2 washers and keels units pulling screws. As a result, take-off weight X3 remained approximately the same as in the initial EC155. At the highest loading fuel and instrumentation 4900-5000 X3 weighs less than a kilogram. With all this change in the system screws affected the ceiling fly — during testing only managed to climb to 3800 meters.
September 6, 2010 began mock test rotorcraft X3. In contrast to the general type of construction, the course of the tests were identical to those tested as Russian and South American vertibirds. First test pilots inspected the ability of the aircraft in the vertical takeoff and landing, as maneuverability and stability in flight «helicopter-style.» The next months were found to eliminate problems and gradual acceleration flight with disabled drive rotor and included pulling units. May 12, 2011 X3 layout set «personal record»: in a few minutes he confidently held a speed of about 430 kilometers per hour. Over the next 18 months there was no news of the conquest of new markers speed, but it seems to be caused by the need to find good flight modes. Tests Eucopter X3 rotorcraft go so far. Emergence of the first aircraft at its base applicable for mass practical use, it is expected beyond 2020.
Sikorsky S-97 Raider
At a time when European aircraft manufacturers were already in full swing tests rotorcraft X3, staff offices «Sikorsky» continued study on ABC with the aim of creating a new rotary-wing aircraft that can be used in real-world criteria. In October 2010, it was officially announced the beginning of the project S-97 Raider. Prior to the development of a new concept of rotorcraft ABC endured little configuration. According to the results of research in the process of applets X2 revealed that for the effective maintenance of rotary-wing aircraft in the air at tremendous speeds flight can not only change the repeating pitch of the rotor, and slow rotation. With the correct calculation of rotor deceleration tangible move into the direction of growth of the horizontal velocity threshold at which prepyadstviya start with a lifting force. Calculations have shown that retains the desired rotorcraft rotor lift, even when deceleration is 20%. Specifically, such an idea in Sikorsky decided to check in subsequent research and practical tests.
The rest of the rotorcraft S-97 to a large extent similar to the previous X2. According to currently available data, the brand new machine will have a relatively small dimensions: length less than 11 meters and rotor diameter of 10. Preserved general concept of placing screws. Thus, S-97 Raider will be equipped with 2 coaxial rotors with painstakingly closed spinner. At the rear of the fuselage will be located streamlined five-blade pusher propeller. With all this already on the earliest drawings to the intended promising compound helicopter was noticeable change fuselage and empennage design change.
Until a certain time on a «raider» could be judged only by the fragmentary information that became available to the public, as the numerically small drawings. But even before the technical details of the project it became clear that he’d take the role in the program of the Pentagon AAS (Armed Aerial Scout — Armed aerial scout). Favorite competition in the coming years will be the main aircraft of the U.S. Army created for aerial reconnaissance on small distances from the band edge. In addition, the Pentagon spy lusts provide the opportunity not only to identify targets, and hit them without the help of others. Precise composition of required equipment has not yet announced, but on the basis of figures provided by promising S-97, you can make approximate conclusions. On small wings on the edges of the fuselage can be installed two units with weapons. Perhaps it will be blocks rockets or anti-tank guided munitions. Also, in some sources mention the possibility of installation on rotorcraft mobile gun turret mnogokalibernym Browning M2HB.
At last this year saloon EAA AirVenture Oshkosh company «Sikorsky» for the first time presented to the public a new full-scale model of its own S-97 rotorcraft. This layout, except for a few minor details, the same form of the aircraft shown in more earliest drawings. In addition, this year were refined alleged technical details of the machine. Thus, it became clear that the first S-97 models will be equipped with turboshaft engines to family General Electric T700. But in the upcoming follow-seasoned standards, and right behind them and serial vertibirds get new engines developed in the current time to programmke AATE. With the new engine S-97 during takeoff weight of about 5 tons will be able to accelerate to 440-450 km per hour. With all of this range will exceed 500 km.
Some questions causes build new rotorcraft. Turboshaft engine vozduhopoglotitelya separate requests. In the S-97 has two such openings. For all this they are both located in the middle of the fuselage, closer to the tail. This fact and the fuselage can hint at the accommodation in the aft engine rotorcraft. But in this case is not entirely clear exactly how divorced drive shafts and bearing pusher. Other elements of the form a promising S-97 are fully understood and they say the creators of the intention of the project to provide him the highest speed. Among other mentioned elongated teardrop-shaped fuselage and cautious spinners rotor.
Also interest is internal equipment rotorcraft. Existing photo layout S-97 cockpit equipment can be seen. Thanks to the huge windshield, two pilots have a good forward visibility to the side. On the dashboard of rotorcraft there are two functional color monitor and some panel keys. Perhaps part of cabin equipment can be extended other control panels placed, for example, on the ceiling or between the pilot seats. Constructors office Sikorsky decided curious problem of placement of controls. On the model S-97, as seen in the photo, absolutely no pedals, and in their place put small footrest. Flight control, apparently planned to make with the help of 2-handles on the pilot’s seat armrest. Most likely, the right stick controls the repeating step rotor, and the left is responsible for its overall pitch and engine power. While not entirely clear how you plan to adjust the speed of horizontal flight. Due to the fact that while only the layout presents all have reason to believe repeated change of cabin equipment, including controls.
Immediately placed in the cockpit volume created for the carriage of passengers or cargo. On the layout of the cockpit set up three seats for the landing and some iron box, perhaps to accommodate any small loads. Access to the cargo cabin via two sliding doors on the edges of the fuselage. Maybe in the future, new engines or other technical solutions will increment the volume and cargo cabin, for example, set it down for more fighters. In addition, the experience of multi-purpose helicopters of similar class-duty rear cabin can be armed with devices for securing any weapons for firing at ground targets.
We should not forget that at AirVenture Oshkosh was only shown the layout. First flight layout rotorcraft S-97 Raider is scheduled for 2014, because some aspects of construction and equipment are subject to change. As for speed records, they appear much later, around the end of 2014 or even in 2015.
Promising Russian projects
In our country most actively engaged vertibird theme of «Kamov». The greatest prospects in the current time are its Ka-92 project. This multi-purpose rotorcraft is modified helicopter with coaxial-rotor and coaxial screws to pushing. According to preliminary calculations, the two turboshaft engine (approximate capacity is not made public) will be able to accelerate the car to a speed of about 500 km / h With such speed rotorcraft Ka-92 is capable of carrying up to 30 passengers at a distance of about 1,400 km. Ka-92 project in its aims recalls British Fairey Rotodyne: it must be rotary-wing vehicle with low requirements to the size of sites for take-off and landing. Go with this, he must have the flight data that will be able to compete with short-range passenger aircraft.
Another project office «Kamov» — Ka-90 — does not have such huge practical perspectives and practical work is experimental. Introduced in 2008, the concept can assist helicopters dispersed not only to 450-500 km per hour, and to take the bar in the 700-800 km / h To do this, create a proposed horizontal thrust turbojet engine, also change the design of the blades and rotor head. Ka According to the draft 90, the two rotor blades must have a width comparable to an enormous and small thickness. Such rotorcraft soars vertically or with a small run-up, further by a turbojet engine accelerated to a speed of 400 km / h After reaching a speed rotorcraft rotor stops and fixes it in a perpendicular position to clot. Now screw the wing makes functions. When overclocking the upcoming special mechanism in the hub rotor increases uniformly sweep such «wing» until such time as the propeller blades are not stacked along the fuselage. Interestingly, in the fantastic movie «The 6th Day» (2000, directed by R. Spottiswoode) featured aircraft specifically with this method of combining the best features of the aircraft and helicopter. At the same time, Whispercraft soundtrack is not quite folded blades and producing high-flying configuration swept «wing». Prospects for the Ka-90 is not completely clear. Even if you work on this project until this last time, a couple of years there have been no new information. Can be very bold and up to a certain time just useless project was shelved, what is called, to the best times.
Immediately with the Ka-92 and Ka-90 IOB them. ML Mile presented his project, which belongs to the same class of vehicles. Mi-X1 project involves the creation of multi-compound helicopter with a takeoff weight of 10-12 tons. Aircraft, filled with 2 VK-2500 engines must carry up to 25 passengers, or up to 4 tons of cargo. The aim of the project is to achieve a cruise speed of more than 450-470 km per hour. The highest rate characteristics, in turn, must exceed 500km / h Design range — 1500 km. Rotorcraft Mi-X1 to a large extent similar to the Ka-92, but has only one rotor. The main difficulty is to ensure the proper flow of the rotor blades. To address this issue at the time the study began and development work over the oppression of flow separation on the retreating blade. Blowing in the wind tunnels, theoretical calculations and other scientific research project of the Mi-X1 is quite complicated, because even in 2008, the first flight of the new layout rotorcraft attributed to the 2014-15 data.