Convertiplanes are special aircraft that combine the capabilities of a helicopter and an airplane. They are machines with rotary propulsors (most often screw ones), which act as lifting engines during takeoff and landing, and in flight begin to work as pulling ones. In this case, the lifting force necessary for horizontal flight is provided by an airplane-type wing. Most often, the engines on tiltrotors turn together with the propellers, but on some, only the propellers are turned.
Functionally, this design is close to a vertical take-off and landing aircraft (VTOL), but tiltrotors are usually classified as rotary-wing aircraft due to the design features of the propellers. Tilrotor aircraft use lightly loaded low-speed propellers, close to those of a helicopter and allowing the device to fly in helicopter mode - at a small angle of rotation of the propellers. The tiltrotor's large propellers, comparable to the wingspan, help it during vertical takeoff, but in horizontal flight they become less effective compared to the smaller diameter propellers of a traditional aircraft.
As already reported, Russian and American scientists are working on the creation of a new type of aircraft - a tiltrotor. However, such a device has already been created and its limited use has already begun.
What is this machine?
A tiltrotor is a cross between an airplane and a helicopter. An aircraft that can land and take off vertically, and then, thanks to the rotation of the propulsors, continue horizontal flight in an aircraft manner.
Traditionally, propeller-driven machines are classified as tiltrotors in order to somehow distinguish them from vertical take-off and landing aircraft. There are several types of tiltrotors. For some, when changing the flight mode, the entire wing rotates at once, for others, the nacelles with engines and propellers, and for others, only the propellers themselves.
The benefits of this concept are obvious:
Pole takeoff and landing is a valuable capability for both military and civilian aircraft;
In the air, a tiltrotor develops greater speed than a helicopter and is ahead of its rotorcraft counterparts in flight range.
But there are also disadvantages:
The speed and flight range, although greater than those of helicopters, are inferior to airplane performance. Propellers designed to provide lift during takeoff become ineffective in level flight;
The structure itself turns out to be heavier. It is not uncommon for aviation to have situations where, when creating a new machine, there is a struggle for every kilogram, and the engine turning mechanism weighs quite a bit;
In addition, this is an additional critical component that can also break;
And the most important thing is the difficulty of piloting. Tiltrotor aircraft require specially trained, experienced, high-class pilots who have the skills to pilot both airplanes and helicopters. “The Last Inch” cannot be played on a tiltrotor.
Thus, universal machines turn out to be more efficient than the original ones in a rather narrow segment of tasks. For example, if the point where the cargo needs to be delivered is located beyond the range of helicopters, and the equipment of a runway is not possible.
The United States Department of Defense considered that such situations would happen quite often, and ordered more than one and a half hundred Bell V-22 Osprey tiltrotor aircraft for the needs of the Marine Corps. The car turned out to be quite expensive (about $116 million) and not very reliable.
In just ten years of operation, 6 disasters occurred, which claimed the lives of seven people. The most recent occurred in 2016, when an Osprey carrying 22 people made a hard landing in Hawaii on May 17. And this is not counting the fifteen-year period of development and testing, during which 30 people died as a result of accidents of this highly complex machine.
But the United States has the right to be proud of its unique equipment, which is not in service with other armies of the planet.
But perhaps this situation will end after some time. Recently, information was received from the Russian concern "Russian Helicopters" that work on creating a domestic tiltrotor is already underway. Moreover, this was stated not by anyone, but by the director of the company
Andrey Shibitov:
“Together with our partners, we are developing a tiltrotor technology that is completely new for Russia with a hybrid power plant. We plan that such a design scheme will allow us to confidently reach speeds of up to 500 kilometers per hour.”
It is planned to first create an unmanned vehicle with a take-off weight of about 300 kilograms. A small copy is needed solely for demonstration purposes in order to assess the prospects of the project in advance.
Then the same one is planned, but for two tons. This vehicle can already be used as a separate unit with its own range of tasks befitting a heavy drone.
In the 30s of the last century, Soviet aircraft designers worked on various options for constructing a tiltrotor. But this matter did not progress beyond research. Designer Boris Yuryev was an enthusiast of the development of this type of aircraft.
In 1934, he proposed a design for the Falcon fighter, which was supposed to have a rotating wing and a pair of propellers in the nacelles. However, neither the Falcon nor Yuryev’s other helicopter-airplanes ever reached the stage of flight testing - the level of technology at that time was still insufficient.
Before the outbreak of World War II, research was also carried out in Germany. All of them stopped at the drawing stage: the tiltrotor P.1003 of the Wesserflug company, the wunderwaffe (“miracle weapon”) Fa-269 of the Focke and Ahgelis company, as well as projects of the Heinkel and Focke-Wulf companies.
The convertible English helicopter Fairey Rotodyne can also be classified as a convertible helicopter, which, with the help of two pulling turboprop engines, can switch to the main rotor autorotation mode (rotation using the oncoming air flow, like in a windmill), and when taking off, it operates like a helicopter. In 1958, this device was presented at the Farnborough Air Show. It reached a record speed for rotorcraft of 400 km/h.
In the 50s, a prototype of the XYF-1 Pogo tiltrotor was built. In 1954, the XFY-1 made its first horizontal flight followed by a vertical landing.
In 1972, Mil Design Bureau got down to business seriously, starting the development of the Mi-30 tiltrotor with two rotary propellers that change position along with the engines located in the nacelles.
After positive results were achieved - the carrying capacity of the designed vehicle was 5 tons, and the number of paratroopers transported was 32 - the production and testing of prototypes was planned for 1986-1995. However, this project, like dozens of others across the country, was closed due to perestroika and the subsequent collapse of industry.
Interesting is the only country that has tiltrotors in service, and the American Bell V-22 Osprey (“Osprey”) is the only mass-produced tiltrotor in the world.
The development of the V-22 Osprey began in the 1980s after the failure of Operation Eagle Claw (an attempt to free hostages in Iran on April 24, 1980), when there was a need to create a faster alternative to the helicopter. At that time, vertical take-off aircraft already existed, but they had a number of disadvantages related to instability during takeoff, difficulty in piloting, and worse payload and flight range compared to conventional aircraft. Also, during takeoff, the hot jet of exhaust gases from jet engines caused erosion of the surface of the runways.
Flight tests of the new aircraft began on March 19, 1989. Already in September, Osprey successfully demonstrated a change in flight from vertical to horizontal. In December 1990, the tiltrotor made its first landing on the deck of the aircraft carrier USS Wasp.
It was decided to equip the Marine Corps and Special Operations Forces with such vehicles. The Navy signed a contract to purchase four V-22s and upgrade two existing prototypes, which were supposed to be made lighter and cheaper. The price of one device was $71 million.
Now in Russia they have decided to return to the idea of creating an “airplane-helicopter”. But so far this is happening at the level of research conducted in Russian universities. Which, nevertheless, can give real results. Thus, at Ukhta University, with the participation of MIPT and TsAGI, research work was carried out “Determination of rational parameters of a new vehicle (convertiplane) for the northern regions and shelf fields.”
Based on the results of this research, it is quite possible to build a tiltrotor with a flight range of 2000 km with 14 passengers on board, including two pilots. The payload of the vehicle is 3 tons. But, naturally, to bring the matter to a victorious conclusion, substantial funding is required. At the same time, potential investors are well aware that, based on world experience, this is an extremely protracted and risky business.
The Russian Helicopters holding company plans to create by 2019 a prototype of the first electric tiltrotor in the Russian Federation weighing 1.5 tons. We are talking about the VRT30 unmanned aerial vehicle, which was presented at the MAKS-2017 forum. A tiltrotor is a hybrid of an airplane and a helicopter - a very expensive and high-tech machine. At the moment, convertiplanes are only mass-produced and used for military purposes. There are no such aircraft in the Russian army, despite the fact that the pioneer in the development of these miracle machines was the Soviet designer Boris Yuryev. What tasks can tiltrotors perform and whether they will appear in service with the Russian Armed Forces.
Projects to create a Russian tiltrotor are beginning to take on real features. The VR-Technologies design bureau (part of the Russian Helicopters holding) plans to present a prototype of the first electric unmanned tiltrotor VRT30 in two years.
A mock-up of the future device was presented at the MAKS-2017 aerospace salon, which was held in July 2017. A tiltrotor with a take-off weight of 1.5 tons will be able to reach high speeds and take off without accelerating along the runway.
“Today, together with our partners from the SuperOx company, we are developing a new flying tiltrotor laboratory, the on-board cable network of which will use high-temperature superconductivity technologies, which will have a positive effect on the weight, size and flight characteristics of the prototype,” said Andrey, General Director of the Russian Helicopters holding company. Boginsky.
All tiltrotors face a specific controllability problem that is not typical for airplanes. On airplanes moving at fairly high forward speeds, traditional controls (ailerons, rudders, and elevators) are in the airstream. The reaction of the air flow to the deflection of these controls provides control forces that change the aircraft's position in space. On tiltrotors, the use of such flight controls is possible only in horizontal (forward) flight mode, but they turn out to be useless in vertical takeoff and landing modes, as well as hovering (since in these modes there is no oncoming air flow).
Therefore, tiltrotors must have a second control system that is effective at low or zero airspeeds. Depending on the design and power plant of the aircraft, this role can be performed by:
jet (jet) control system, which includes nozzles and high-speed valves installed at the wingtips and other points of the aircraft;
a thrust vector control system consisting of several propellers to create and directly control lift;
control surfaces located in the wake of the main propellers or turbines.
According to their scheme, tiltrotors can be divided into two main classes, each of which is characterized by specific problems of transmission and conversion of thrust developed by the power plant.
The first class is tiltrotors with a horizontal position of the device during takeoff and landing modes. These devices remain in a horizontal position - both during takeoff and landing modes and in horizontal flight mode. In these tiltrotors, to implement transitional modes such as takeoff, the thrust of propellers, fans or jet engines is used, after which the direction of the thrust vector is changed so that the device begins to perform normal horizontal flight. In horizontal flight mode, the lifting force necessary for the movement of the vehicle is usually created due to the flow around rather traditional wings. In some of this class of aircraft, the thrust generating devices are deflected at a small angle to ensure level flight. In this position they also generate a significant portion of the lift.
The second class is tiltrotors with a vertical position of the vehicle during takeoff and landing modes. This class of devices includes tiltrotors, which take off and land in a vertical position, and make a 90° turn to transition to horizontal flight. Devices of this class have fundamental disadvantages that make them unsuitable for commercial use. Only a few devices of this type were built. As a rule, these are single-seat military vehicles such as fighter aircraft or purely experimental models.
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The factory crawler turned around and began to descend. So she slid down the dry strip at the foot of the ridge. Its caterpillars touched the sand. Gurney opened the cone cover and adjusted the safety straps. As soon as the factory landed, he jumped onto the sand and slammed the cone-shaped cap behind him. He was joined by five of his personal guards who jumped out of the bow compartment. The rest freed the factory's transport fastenings. Its wings trembled, spread and described the first semicircle, after which the huge crawler factory soared into the air and flew towards the dark strip. A thopter landed on the spot where she stood, then another and another. Having landed the people, they took to the air again.
Frank Herbert, Dune
A heavier-than-air VTOL aircraft that can hover motionlessly in place while moving quickly horizontally has always been a tasty morsel for the military. Of course, with the help of such a vehicle, the landing of troops and the evacuation of the wounded from the battlefield, the delivery of cargo and ammunition to soldiers are simplified; The device can be used to destroy individual targets, for reconnaissance and adjust artillery fire.
PROMOTION MACHINE
The first attempt to use unusual propeller-driven devices in war was the use of gyroplanes (from the Greek autos - itself and gyros - rotation). A gyroplane is a strange thing: in appearance it looks like an airplane without wings, but with a propeller similar to a helicopter. But, unlike the latter, the gyroplane propeller rotates freely, in autorotation mode, creating lift; The engine drives only the propeller, which pulls the car forward.
The idea to build an apparatus of this type first came to the mind of the Spanish aircraft designer Juan de la Sierva. Watching in 1919 how the three-engine biplane he designed fell, he noticed that the propellers, under the influence of the incoming air flow, began to autorotate, that is, to rotate spontaneously. Further reasoning was simple: if the biplane had a large main rotor-autorotator, then the test pilot could survive!
After a series of failures, Juan managed to construct a fairly decent flying gyroplane (model C-4, 1923), and a little later - a demonstration model C-8, which made a splash in Europe. The designer flew from Paris to London on the S-8. Soon after this, gyroplanes appeared in the USSR (1929, designed by engineers Kamov and Skrzhinsky), then in Great Britain, and later similar machines began to be designed by all other leading countries in the world.
THE FIRST STEPS OF CONVERTIOLANS
Years passed. Autogyros at the combat post were replaced by helicopters, but the latter had one serious drawback - a relatively low horizontal speed. The asymmetrical blowing of the main rotor blades (they moved either in the oncoming air flow or against it) led to the fact that the “ceiling” of a helicopter’s speed by the end of the 50s was approximately 300 km/h - and this despite the fact that airplanes could already fly at three times the speed of sound! Aerodynamics experts warned: it is impossible to endlessly increase the number of revolutions of the main rotor, as this may cause flutter (self-excited vibrations of parts of the aircraft), which will lead to loss of stability and controllability, or even complete destruction of the structure. What to do? Maybe it’s worth equipping the helicopter with airplane wings? Eureka!
However, the new is just a well-forgotten old, because the first experiments with aircraft of the combined design were undertaken back in the 1930s. And now, two decades later, attempts to create hybrids were again made by the USA, Great Britain, France, Canada and a number of other countries - almost simultaneously.
In an attempt to achieve high speeds on convertible aircraft, designers took two paths. In the first case, the machine (rotorcraft) had a main rotor, like a helicopter, plus another propeller (or several screws) in the vertical plane, like an airplane. The second scheme turned out to be much more interesting: the helicopter was equipped with rotating motor groups on the wings, that is, right in flight it was possible to turn a helicopter into an airplane and vice versa. The latest design was called “convertiplane”.
HYBRID FOR SPECIAL FORCES
Back in October 1936, the defense of the Sokol project, an aircraft with a rotary wing, took place at the Moscow Aviation Institute. Student Kurochkin managed to anticipate the development of tiltrotors three decades in advance - only in 1964, after much research, after the hard work of designers, aerodynamicists and engineers of the American companies Vouht, Ryan and Hiller, the military transport rotorcraft XC-142A was created. It was equipped with a rotating wing with a span of 20.6 m with flaps and slats, attached to the fuselage on hinges.
A synchronous mechanism rotated the wing at an angle of up to 106°. Four turboprop engines were mounted on the plane, which produced 2850 hp during takeoff. and provided the tiltrotor with a maximum speed of 604 km/h. The nose housed a double cockpit with ejection seats. The XC-142A could be lifted into the air and landed either like a helicopter (from one place to another) or like an airplane, with a take-off run or run.
| VERTICULAR WINGS: IN THE CHASE OF PROFIT |
| The idea of crossing a helicopter with an airplane came to the minds of many designers immediately after World War II - engineers from the USA, France, Great Britain, Canada and a number of other countries, in pursuit of excess profits from the operation of a high-speed commercial helicopter, joined the race of designers. The appropriate amounts were spent on this matter: for example, the American airline McDonell allocated more than 50 million dollars for the development of a prototype, plus another 75 million paid for its modification. Soviet pilots were the first to fly such a device, which received the name “rotorcraft,” - it was TsAGI-11EA (1936). But the war stopped experimental developments, and quite little is known about TsAGI, so American aviation historians consider their brainchild the “firstborn” - the McDonnell XV-1 tiltrotor built in 1955. Not so long ago, by the way, the American magazine Aviation Week reprinted the editorial of an old newspaper, through which this “new, hitherto unprecedented type of aviation technology” famously flew by. Like any helicopter, the XV-1 was equipped with a main rotor, and from the aircraft it received wings and a pusher propeller. In horizontal flight, thrust was created by a rotating rotor and propeller. If the propeller was disconnected from the transmission, the lifting force of the car was created by the wing. The landing gear was replaced with steel skis, which was not surprising, since McDonnell took off like a helicopter. At the same time, the Continental engine gave all its power to the main rotor of the engine, which simultaneously worked on the air compressor. Compressed air and fuel were supplied to the ends of the blades - that is, the Americans actually used a jet drive. |
Canadian designers, in turn, to ensure stability and controllability of the tiltrotor in hovering mode, equipped their brainchild CL-84 with two coaxial tail rotors located behind the keel and stabilizer. After a vertical takeoff, they stopped, the rotors turned, the wing was fixed, and after 10 seconds the CL-84 was already rushing forward, picking up a speed of 500 km/h.
At the same time, a number of tiltrotors from various American companies appeared: the topic was fashionable, the US Air Force promised to buy everything that passed at least the initial tests, and the engineers happily plunged into work. One of the most original designs was the Bell X-22A with not two, but four YT58-GE-8D engines with a total power of 1250 hp. On this tiltrotor, for the first time in the short history of such machines, the propellers were placed in circular casings, which significantly increased efficiency during both vertical movement and horizontal flight. The first of the two Bells produced crashed (the pilot survived) while landing during early testing, but the second flew successfully from 1966 to 1988, although the model never went into mass production.
Europe was a little behind in this matter, but original developments also sometimes appeared. Perhaps the most famous European tiltrotor of the 1960s was the French Nord 500 Cadet - small, nimble, light (only 1300 kg when loaded). At the 1967 Paris Aviation and Space Show, the military liked the single-seat tiltrotor, and Nord was asked to produce several copies for reconnaissance and surveillance. True, the tests dragged on; The Nord 500 made its first flight only in 1968, a year later it was “blown out” in a wind tunnel, and then somehow the need for such a machine disappeared. Reconnaissance could also be carried out on a compact helicopter.
TAIL FORWARD
The Canadair CL-84 has already been briefly mentioned in this material, but it deserves a little more attention. Still, this model went beyond a simple test program: the Ministry of Defense ordered several vehicles from the manufacturer to be put into service.
Canadair showed interest in tiltrotors in 1956, and by 1965 produced its own hybrid, the CL-84 Dynavert. The aircraft, which could seat 12 people (plus 2 crew members), had a traditional round fuselage. A very interesting point in the design of the CL-84: the wings of the device were capable of turning at an angle of up to 100°, which provided the ability not only to hover in place, but also to fly tail first at a speed of 56 km/h!
The first demonstration of a tiltrotor hovering in the air took place on May 7, 1965. After 145 flight hours, the aircraft crashed (September 12, 1967), but the Canadian Department of Defense had already ordered three copies of the improved CL-84-1 aircraft, giving it the army designation CX-84. The changes affected turboprop engines, the power of which was increased, as was the volume of fuel tanks. There are also two additional external suspension points. The army version was armed with a 7.62 mm machine gun, a 20 mm cannon and 19 missiles.
The first CX-84 took off on February 19, 1970, made several landings on the Guam underwater surveillance system control ship in February 1972, but also crashed in August 1973. The second aircraft participated in the sea testing program for an underwater surveillance system as part of the air wing of the Guadalcanal ship in March 1974, but the Canadian military did not dare to adopt the aircraft.
ROTORPROOF FOR KHRUSHCHEV
In the USSR, with its vast expanses and the lack of a developed airfield network, the prospect of using heavy-duty rotary-wing vehicles seemed life-saving - both for military and civilian missions. In the mid-50s, the design bureau of the famous aircraft designer Kamov made a revolutionary decision: to build a transverse aircraft with two tractor rotors and two main rotors at the ends of the wings. For domestic aviation, this type of aircraft was new and combined the advantages of a helicopter capable of vertical takeoff and landing, and an airplane with its large payload, range and flight speed. But first of all, the tiltrotor was created to transport paratroopers, military equipment and large cargo.
In 1961, OKB test pilots set eight world records on the Ka-22, including speed (356.3 km/h) and maximum weight of cargo lifted to a height of 2000 m (16,485 kg). The characteristics of the rotorcraft are also interesting: maximum take-off weight - 42,500 kg; the dimensions of the cargo compartment are 17.9 x 2.8 x 3.1 m. For comparison: the maximum take-off weight of the largest Ka-25 helicopter at that time was 7000 kg. However, the rotorcraft never went into production. Two crashes of experimental aircraft played an important role in this, after which the Air Force leadership began to treat the rotorcraft with distrust.
The first disaster occurred at Dzhuzala airport, where rotorcraft 01-01 was landing. At the same time, a regular IL-14 plane landed on the emergency runway, the pilot of which later wrote in an explanatory note about the disaster: “10-15 seconds before the disaster, I was on a straight line, landing at heading 240 to the emergency runway. The rotorcraft was ahead of me at a distance of 300–400 meters and 50–80 m below. No deviations from the rotorcraft's normal gliding trajectory were observed. At an altitude of 50–70 m, the rotorcraft slightly scraped (I saw this by the change in the projection of the rotorcraft when viewed from behind and from above), then began to turn to the left while simultaneously turning onto its back. The nature of the turn is slow at first, then energetic with the transition to a steep negative dive. The rotorcraft collided with the ground, fell apart and burst into flames. Two or three large parts flew away from the source of the flame in a southern direction, leaving a trail of dust on the ground.” None of the seven tiltrotor crew members survived. The hand of pilot Efremov was found at the helm of the destroyed vehicle, which they were able to open with great difficulty...
For non-pilots, it is worth explaining that pitching is the movement of an aircraft when its nose is slightly “lifted” relative to the local horizon.
The second incident was just as tragic. “There were a lot of witnesses to the disaster - people were walking and going to work at that time,” wrote one of the members of the Kamov Design Bureau. - Rogov and Brovtsev died. The remaining crew members spoke about the beginning and development of the disaster. Takeoff “like an airplane”, a calm flight at an altitude of 1000 meters for 15 minutes. Speed up to 310 km/h. While gliding and reducing the speed to 220–230 km/h, a spontaneous right turn suddenly began, which could not be countered with the left pedal and steering wheel. The machine turned almost 180° when Garnaev intervened in the control and, thinking that the turn was a consequence of the different pitches of the main rotors, unloaded them, sharply increasing the overall pitch angles of the main rotors by 7–8°. The rotorcraft slowed down the right turn, rolled over onto its nose and began to dive steeply. Having lost 300–400 m of altitude, the vehicle reduced its dive angle to 10–12°, but at this time the flight mechanic dropped the canopy flap, it hit the right propeller blade, which broke off, and unbalanced centrifugal forces tore off the entire right engine nacelle...”
In general, we can say that the work on aircraft with the possibility of helicopter launch and flight “like an airplane” did not cause a revolution in aircraft construction. But the knowledge acquired by test pilots, who controlled unusual machines in two flight modes at once, was useful to their colleagues very soon - a few years later, vertical take-off and landing jet aircraft appeared.
Science fiction writers also did not pass by such aircraft - machines with rotating engine nacelles can be found in many science fiction books, films and computer games.
| In What play? |
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Today, many have seen on TV or on the Internet stories about such an interesting aircraft as a tiltrotor, someone has read about them in magazines. What are these interesting machines? Tiltrotors are aircraft that are capable of performing vertical takeoff and landing (like conventional helicopters), but are also able to carry out long-term horizontal high-speed flight, which is characteristic of airplanes. Since such aircraft are neither airplanes nor helicopters, this affects their appearance. In addition to the fact that these aircraft are characterized by different flight modes, during their creation and design it is often necessary to make compromise solutions.
It is worth noting that dreams of building an aircraft that would be capable of vertical takeoff and landing, simultaneously with high-speed horizontal flight, have as long a history as dreams of flight in general. The first projects of something similar were proposed at one time by Leonardo da Vinci. The very idea of “crossing” a fairly fast aircraft, but limited in flight modes and basing conditions, and a much slower helicopter, but unpretentious in its take-off and landing locations, occupied the minds of designers and military personnel for many years. However, such devices have been able to achieve any noticeable development only recently.
Work on tiltrotors - aircraft that could be transformed from a helicopter to an airplane and back by turning the propellers - was carried out in many countries around the world. Designers from almost all countries with a developed aviation industry have been working on such machines for more than half a century. The first work in this area can be dated back to the 1920-1930s of the last century. They worked on the creation of a tiltrotor in pre-war Europe; during the war they worked on a project for such machines in Germany. In the 1970s in the USSR, the Mil Design Bureau carried out work on the Mi-30 tiltrotor project, which never took off. As a result, some success in their creation was achieved only in the USA. The only tiltrotor aircraft in production today, the Bell V-22 Osprey, is in service with the US Marine Corps. Its development by Boeing and Bell took more than 30 years.
American tiltrotor project VZ-2
According to their scheme, tiltrotors can be divided into 2 main classes, each of which is characterized by its own specifics and its characteristic problems of converting and transmitting thrust developed by the machine’s power plant. We are talking about tiltrotors with a rotating wing and tiltrotors with rotary propellers.
Rotary-wing aircraft combine the characteristics of multi-engine aircraft, in which the engines are located on the wing consoles in a fixed position, with the capabilities of vertically taking off and landing helicopters. This technical solution makes it possible to achieve flight ranges and speeds characteristic of aircraft (also the ability to transport cargo), along with the ability to perform vertical takeoff and landing. During takeoff, the wing of the vehicle is set to a vertical position, and the propellers create the thrust necessary for the vehicle to take off. During transitional flight, the wing gradually returns to a horizontal position. After returning to a horizontal position, all the lifting force is created by the wing, and the propellers provide the thrust necessary for horizontal movement of the device.
At one time, a number of American aircraft manufacturing companies, as well as one Canadian company, experimented with similar devices, some of their experiments can be considered quite successful. For example, the American tiltrotor X-18 with a rotary wing. The X-18 tiltrotor had a rectangular fuselage and a high wing of small span. In the middle part of the wing, 2 powerful Allison T40-A-14 turboprop engines were mounted, developing a power of 5,500 hp. every. These engines were equipped with three-bladed counter-rotating turboelectric propellers “Curtis-Wright” (the diameter of the propellers was 4.8 meters).
X-18 tiltrotor with rotary wing
During the helicopter takeoff, the entire tiltrotor wing rotated along with the engines (90 degrees around its longitudinal axis). At the same time, a standard airplane takeoff was used to take off the device with maximum load. In addition, in the tail section of the aircraft there was an additional Westinghouse J-34-WE turbojet engine, which developed a thrust of 1530 kgf. Its jet stream could change its direction in the vertical plane, which significantly improved the tiltrotor's controllability at low flight speeds.
In 1958, the first and, as it turned out later, the only prototype of the X-18 was manufactured. This tiltrotor underwent a fairly intensive cycle of ground tests, after which in 1959 it was transferred to the Research Center named after. Langley, where it first took to the air on November 24, 1959. Before the completion of flight tests in July 1961, the X-18 tiltrotor managed to complete about 20 flights. The main reason for the end of its testing and the subsequent curtailment of the program was a malfunction in the mechanism for changing the pitch of the propeller, which occurred in the last flight of the device, as well as the fact that its engines “were not interconnected.” During one of its further ground tests, the X-18 tiltrotor was destroyed and ended its life in a landfill. However, it is worth noting that this tiltrotor made it possible to collect a sufficient amount of data that was necessary for the construction of a heavier and more advanced tiltrotor XC-142, which has 4 engines.
The second most common type of tiltrotor is the model with rotary propellers. They have become more widespread, at least among experimental aircraft for sure. The disadvantage of such models in comparison with classic helicopters is the need for wings of a fairly large span. This is due to the fact that on such devices, 2 screws of sufficiently large diameter are most often mounted next to each other. This requires an increase in the area used for takeoff and landing. Since the design of many tiltrotors uses power plants consisting of several engines, which drive the propellers, the failure of one or several of them at once can have catastrophic consequences for the aircraft. Taking this into account, in order to prevent disaster in the design of multi-engine tiltrotor aircraft, one can often find cross-over transmissions, which make it possible to drive several propellers from just 1 engine, which in turn leads to an increase in the mass of such devices.
Bell V-22 Osprey with rotating nacelles
It is worth noting that it is usually not the propellers themselves that are rotatable, but the nacelles with them, as is implemented on the only mass-produced tiltrotor Bell V-22 Osprey. This aircraft, which is in service with the US Marine Corps, is equipped with 2 Rolls-Royce T406 engines with a power of 6150 hp. every. The engines are located in special nacelles at the ends of the wing and can be rotated up to 98 degrees. Three-bladed propellers with trapezoidal blades are interconnected by a synchronizing shaft, which is laid inside the tiltrotor wing. This shaft also allows the Bell V-22 Osprey to land with only one engine running. In order to reduce the weight of the tiltrotor structure, about 70% of the device is made of composite materials based on glass and carbon fiber reinforced plastics with an epoxy binder, which makes its structure 25% lighter than its metal counterpart.
Since this tiltrotor must be based on sites of limited size, it is equipped with folding wings and propellers, which makes it possible to reduce its width on the ground to 5.51 meters. The crew of the convertiplane consists of 2 people, and its cargo compartment can accommodate 24 paratroopers with their weapons. The propellers of the convertiplane with a diameter of 11.6 meters are also made of fiberglass in order to reduce weight
With the wing deployed, the Bell V-22 Osprey is 25.78 meters wide at the tips of the blades. The length of its fuselage is 17.48 meters. The height of the vehicle is 5.38 meters; with vertically installed engines it increases to 6.73 meters. The maximum take-off weight is just over 27 tons, while the payload weight when using vertical take-off is 5,445 kg. The weight of the load on the external sling is 6,147 kg when using 2 hooks. The maximum speed of the tiltrotor in airplane flight mode is 483 km/h, in helicopter mode - 185 km/h. Practical flight range - 1627 km.
In the early 1950s. The French company SNECMA began experiments with aircraft with an annular wing. After experiments with unmanned models, testing of the S-400 Atar Volant began in 1956. Three years later, an experimental convertible toplane with a ring wing, the S-450-01 Coleoptere, was created. The power plant was an Atar 101E turbojet engine with a thrust of 34.32 kN. Coleoptere made its first free vertical flight on May 6, 1959. However, on July 25, during the transition from vertical to horizontal flight, the plane crashed; pilot August Morel managed to eject.
By order of the American Air Force in 1955, the Ryan company built two aircraft with a vertical hull position for takeoff and landing modes. These delta-wing aircraft were powered by Rolls-Royce jet engines with a thrust of 45.4 kN. The vehicle, called Vertijet, received the designation X-13 according to the US classification. Since the surfaces of the control elements on these jet aircraft were not blown by air flows coming from the propeller, they were not very effective at low speeds. Therefore, control in such modes was provided by means of a rotary nozzle. The pilot also had, as it were, two sets of control instruments. In December 1955, flight tests began, but at the first stage the aircraft was equipped with a temporary three-wheeled landing gear, which allowed it to take off and land like an airplane.
The Vertijet used what is undoubtedly the most unusual airfield in the world to carry out vertical takeoff and landing. This plane did not fall to the ground, but settled on the wall like a fly.
The airfield was an ordinary heavy-duty trailer, the transport platform of which could be raised hydraulically to a vertical position. On the top of the trailer, a massive, strong cable was stretched between two powerful masts. The Vertijet clung to the cable using a special hook installed under the nose of the aircraft. Since the hook was out of sight of the pilot, guidance of the aircraft during landing was carried out with the help of an operator located on top of the trailer. In addition, on the upper part of the “landing wall” there was a special beam 6 m long, along which the pilot could at least slightly orient the plane in space (this beam was marked with white and black stripes, allowing the pilot to determine how far he was from the landing cable).
The first flight with vertical takeoff and landing was carried out only on April 11, 1957. The thrust-to-weight ratio of the device was 1.3, so the takeoff and landing were quite successful. No further testing was carried out; one of the aircraft was demonstrated as a static exhibit at international air shows. However, the military quickly became disillusioned with tiltrotors with a vertical hull position and, for reasons of “philanthropy,” stopped all research on them: even the most experienced test pilots, according to contemporaries, turned pale at the mere memory of a vertical landing on such a machine. However, in the late 1970s. nevertheless, a project of an absolutely fantastic “transforming aircraft” appeared - Nutcracker (Grumman company). When performing vertical takeoff and landing, it “broke” in half so that the cabin maintained a horizontal position, but the project did not go further.
Convertiplane is a twin-rotor aircraft that combines the advantages of a helicopter and an airplane at the same time. On such a device, both screws are located on the wings of the device. For vertical takeoff or landing, the propellers are parallel to the ground. After lifting to the required height, the screws turn at an angle of approximately 90 degrees and become pulling screws.
The evolution of these devices began with gyroplanes. The first gyroplane was the British Fairey Rotodyne (1950), from the Fairey company (this is a play on words - the gyroplane was created by the Fairey company). It is mistakenly called a rotorcraft. However, the development of the world's first classic rotorcraft can safely be considered Kamova- KA-22 (1960). By the way, according to Wikipedia, only one sample survived KA-22 And if anyone knows where he is now, please share the information. Already in the early 60s, KA-22 removed from mass production after a number of disasters. Later in the USSR they did not even intend to return to devices of this class.
However, US leaders had a different opinion and continued the development of rotorcraft, allowing the propellers to change the angle of thrust, thereby creating a new type of aircraft - tiltrotor. In 1989, the first tiltrotor was tested, on which the best US developers worked 30 years. This is how the Bell V-22 Osprey saw the light. But he was not appreciated either. Already in the early 90s, it was decided to give this toy to the Marines. U V-22(like all tiltrotor developments) I see one drawback - loss of traction due to the resistance of the wings, which are located under the propellers. A short discussion among helicopter pilots in the forum suggests that V-22 really good.
I think that it was with the appearance of information about V-22, as a new type of aircraft, we also started developing an analogue. Already in 1972, specialists from the Moscow Helicopter Plant named after. M.L.Mil, began developing a tiltrotor Mi-30. The first flight of this device was expected in 1991. More about development Mi-30 read . But due to the difficult economic situation in the country, Mi-30 it remained on paper.
Here I also want to note that the fastest helicopter in the world for 2008 (by the way, made more like gyroplane) does not reach the speed and 500 km/h. A V-22 has reached its maximum speed since 1990 638 km/h. In addition, it can accommodate 24 paratroopers.
The fact that VA-22, which turned out to have excellent technical characteristics was discarded without argument to the Marine Corps, and even in a “reduced edition”, as well as the not very clear incompleteness of development Mi-30, tells me that most likely this type of aircraft (convertiplanes) is still being developed, but is not advertised.
AND NOW THE MOST IMPORTANT THING! In the movie "Avatar", in my opinion, it is demonstrated an almost ideal aircraft, made on the principle of a tiltrotor. In all the reviews of the film, they correctly call it that - a tiltrotor.
The screws of this unit can rotate in almost any direction, not even in sync what allows him to be super-maneuverable. It has the ability to reach enormous speeds or remain motionless in the air, even in strong winds, compensating for wind correction using the optimal angle of rotation of the propellers. The presence of safety rings helps protect the propellers from breakage during maneuvers in extreme conditions. This ideal general purpose aircraft. It is not at all necessary to talk about the military sphere here.
Such aircraft would become indispensable assistants in the service of the police, ambulance, and rescue services. I also foresee the emergence of a new sport - convertoplaning. Tiltrotor races would attract crowds of spectators all over the world, where the main competitive aspect was not only the speed of this device, but also its super-maneuverability.
Of course, in the future, to improve performance, tiltrotors will use rocket launchers instead of propellers. A propeller is just an example of a source of thrust for a tiltrotor. The photo next to it is just an example of a jet tiltrotor.
I am not a mega-specialist in the aviation technical environment and was guided in this article mainly by logic, so I will be glad if a competent specialist corrects my assumptions about the future of tiltrotors.
On video, a trailer for the game "Avatar". Watch only the first minutes of the video, which demonstrates the player's flight on a tiltrotor. Just pay attention to how maneuverable this thing would be in reality.
