An active differential sounds tempting, high-tech, and something you'll want to buy when shopping for a crossover or SUV, but what exactly is it, what does it do, and is it really necessary? These most important questions will be explored in a comparative test of Mitsubishi Outlander SUVs with two different transmissions: with a conventional differential and with the new active S-AWC differential.
For a comparative analysis of performance in different conditions, two completely identical Mitsubishi Outlander cars were taken, with the only difference being that one Outlander has a traditional open differential installed at the front, and the other has an S-AWC active differential system, which has been installed on these vehicles since the fall of 2014. crossovers equipped with a 3-liter six-cylinder gasoline engine.
S-AWC is a smart all-wheel drive system developed by Mitsubishi. Is an abbreviation of the phrase " Super All Wheel Control,” which can be translated as “Super-level control of all wheels.”
The S-AWC system is installed on cars in the “Sport” configuration, which is 20,000 rubles more expensive than the “Altimet” configuration. Almost this entire amount is the cost of the active differential.
Under normal conditions, it is very difficult to identify the difference in the behavior of these cars with different differentials, since it only appears when the crossover loses trajectory and directional stability, when it leaves the arc when turning or maneuvers on a road with a very uneven coefficient of adhesion (for example, ice - asphalt ).
Outlander takes turns
The first thing in line was a cornering test on a regular asphalt surface. At the beginning of this testing, it seems that the driving characteristics of the cars are the same, but this is for the time being - they were tested at different speeds! So, a Mitsubishi Outlander with a conventional differential, starting from a certain speed, and the higher it was, the more clearly its manner of straightening the turning trajectory was manifested. That is, the higher the speed at which a corner is entered, the more it deflects outward under the influence of centrifugal force.
Centrifugal force is a fictitious force that arises due to the inertia of a body in a rotating frame of reference. The body tends to move straight, therefore, when it is “turned” towards the center, it tends to “move away” from this center.
Moreover, this symptom does not depend on whether the crossover is moving without traction or with the gas pedal pressed. “Outlander” with an active differential S-AWC follows a given path much more willingly. The understeer that was pronounced in the regular Outlander has changed to neutral: now the crossover begins to smoothly slide sideways, but with all its four wheels. At the same time, it maintains both trajectory and directional stability. In fact, this will manifest itself in better preservation of the trajectory of movement as the speed increases when cornering, which means the driver will have a greater chance of staying in his lane rather than flying into the oncoming lane or into a ditch.
It should be noted that both crossovers also differ in the settings of the stabilizing electronics. The model without S-AWC simply cuts off the fuel supply if there is a sudden loss of traction, thereby preventing the vehicle from adjusting the vehicle's trajectory using traction. At the same time, the Outlander, equipped with the S-AWC active differential system, does not completely remove engine torque, but only limits it. And yet, it was noticed that the behavior of cars is different when coasting. In this case, the active differential is not engaged (that is, no traction is transmitted to the front wheels). Thus, it is obvious that the new version has received comprehensive improvements, and not just just a new part.
Circular movement
One of the stages of identifying differences between the “Outlanders” was moving in a circle with a diameter of 30 meters, marked with poles. In a regular Mitsubishi Outlander, equipped with electronically controlled all-wheel drive, there is a switch for three operating modes: all-wheel drive with intelligent traction distribution between the axles (4WD Auto), all-wheel drive with a locked clutch (4WD Lock) and front-wheel drive with the rear axle connected (4WD Eco). The switch is marked with the standard 4WD designation. Vehicles equipped with the S-AWC transmission have added a fourth mode called Snow, which electronically provides optimal traction on all wheels on slippery surfaces.
When driving in a circle, the average speed in both variants remained at about 50 km/h. We checked movement in different directions, with different pressure on the gas pedal, with different states of the stabilization system. As a result, the “active” Outlander constantly turned out to be a little faster - by a fraction of a second, but if you turn off the stabilization system, the time gap increases. Yes, the gap is small, but the driver sitting behind the wheel of the tested models experiences completely different sensations. When driving a regular Outlander, you need to set the steering wheel to the required steering angle, press the accelerator and not operate the steering wheel. They would return to the previous trajectory; when a skid occurred on a turn, only slowing down helped, and steering wheel actions led to nothing. And the stabilization system did not allow increasing speed. Completely different sensations arose when driving a crossover with an active differential, which returned the feeling of real control of a car, and not a gaming robot - a simulator. Here, when a skid occurs or a premonition of its occurrence, you just need to turn the steering wheel to the required degree, press the accelerator pedal a little, and that’s it - the car is already on its trajectory! Thus, Outlander with active S-AWC transmission becomes safer and more predictable to drive.
Sliding on basalt
The coefficient of wheel adhesion with wet basalt is approximately the same as with ice, and in such conditions the tested Mitsubishi Outlander models showed significant differences in their behavior. The “active” Mitsubishi, when driving like a snake, allows for slight swaying and is more susceptible to skidding.
A skid is a violation of the direction of movement of a vehicle along the longitudinal plane.
But this is not scary, because if something happens, the electronics will intervene: when approaching corners close to critical, it turns off the traction and partially takes over control, which makes driving such a crossover more interesting and at the same time safer.
When accelerating from a standstill on the same surface, the Outlander with an active differential was again ahead - it started more confidently with less wheel slip, while the crossover with a conventional differential intended to go to the side, but the stabilization system immediately corrected this. There was no difference in movement when the entire car or any part of it was on a slippery surface.
What is S-AWC for?
The test Mitsubishi Outlander is equipped with a fairly powerful engine developing 230 hp, but it cannot be considered a sports crossover and even the active differential installed in one of them does not actually add speed. The S-AWC transmission gives gains on the track only in a fraction of a second, so its main purpose is to increase active safety, which manifests itself not only when driving under traction, but also when sharply releasing the gas. An active differential can also help when driving off-road - in this case, the driver has an electronically controlled front lock. But this is still not an SUV, and on serious off-road conditions the active differential will not help - most likely the inter-axle coupling will overheat, and it may not come to the aid of a smart design.
In sports and during everyday driving, an active differential performs different tasks: the driver with it develops greater speed, and the ordinary driver receives greater car safety, since the car’s tendency to skid is reduced. And at the same time, in a difficult situation, an active differential allows a person who does not have deep driving skills to avoid many mistakes. For professionals, perhaps a car with a conventional differential will even be more interesting from a driving standpoint, since it makes it possible to remain one on one with the car without electronic intervention.
So, it’s definitely worth overpaying 20,000 rubles for such a smart active differential when the car costs one and a half million!
Scheme of operation of the active differential on the Outlander
The principle of operation of the S-AWC active differential is based on the implementation of thrust vector control, but the scheme of its operation on the Lancer Evolution and on the Mitsubishi Outlander is significantly different. So, on the Evolution, the active differential is located on the rear axle and adds traction to the outer wheel in relation to the turn being performed, eliminating understeer. This is accomplished by two clutches, each of which directs torque to its own wheel.
But the way S-AWC works on the Outlander is completely different, if only because it is installed on the front axle. The main role is played here by the multi-disc clutch, which acts as a soft lock. To compress the clutches, the electronics sends a leading signal at the right moment, and a mechanical self-block would act with a slight delay. The active electric power steering on the tested Mitsubishi compensates for the differential, eliminating sharp steering due to the difference in torque on the right and left front wheels, which prevents the steering wheel from being pulled out of your hands. Naturally, any emergency situation does not occur without the intervention of the crossover's electronic stabilization system, which limits engine power and brake mechanisms that grab the wheels.
S-AWC: history of creation
The Japanese were the first to create it and introduce this concept into use. So, back in 1996, Mitsubishi installed the first active differential on the rear axle of the Lancer Evo IV with all-wheel drive, and in 1997, Honda installed a torque vectoring system on the Prelude coupe with front-wheel drive. Oddly enough, the Germans, who are always among the first to, if not create, then install high-tech things, this time began to introduce a new product only in 2007 (although what a new product it is already!). Such units became available as an option on the BMW X6 and Audi S4, but the active differential became truly widespread only for the Lancer Evolution. Today we can say with confidence that about half of the automakers offer the torque distribution function between the wheels. However, we should not forget that this is not a special mechanic, but just an electronic imitation of it.
Video Mitsubishi Outlander overcomes off-road and snow
Today, vertical take-off and landing aircraft are no longer a novelty. Work in this direction mainly began in the mid-50s and went in a variety of directions. During the development work, aircraft with rotating installations and a number of others were developed. But among all the developments that ensured vertical takeoff and landing, only one received worthy development - a system for changing the thrust vector using rotary nozzles of a jet engine. At the same time, the engine remained stationary. The Harrier and Yak-38 fighters, equipped with similar power plants, were brought to full production.
However, the idea of using rotary nozzles to ensure vertical takeoff and landing has its roots in the mid-40s, when within the walls of OKB-155, headed by chief designer A.I. Mikoyan, on his own initiative, developed a project for such an aircraft. Its author was Konstantin Vladimirovich Pelenberg (Shulikov), who worked at the OKB from the day of its foundation.
It is worth noting that back in 1943 K.E. Pelenberg also proactively developed a project for a fighter with a short takeoff and landing. The idea of creating such a machine was caused by the designer’s desire to reduce the take-off distance in order to ensure combat work from front-line airfields damaged by German aircraft.
At the turn of the 30s - 40s, many aircraft designers paid attention to the problem of reducing the takeoff and landing distance of an aircraft. However, in their projects they tried to solve it by increasing the lift of the wing using various technical innovations. As a result, a wide variety of designs appeared, some of which reached prototypes. Biplanes with a lower wing retractable in flight (IS fighters designed by V.V. Nikitin and V.V. Shevchenko) and monoplanes with a wing retractable in flight (RK aircraft designed by G.I. Bakshaev) were built and tested. In addition, a wide variety of wing mechanization was submitted for testing - retractable and flapping slats, various types of flaps, split wings and much more. However, these innovations could not significantly reduce the take-off and running distance.
In his project, K.V. Pelenberg focused his attention not on the wing, but on the power plant. During the period 1942-1943. he developed and carefully analyzed several fighter designs that used a change in the thrust sector due to deflectable propellers to shorten takeoff and travel. The wing and tail in these cases only helped achieve the main task.
The fighter that was eventually developed was a two-boom monoplane with a three-wheeled landing gear with a front support. Spaced beams connected the wing to the tail, which had an all-moving stabilizer. The main landing gear supports were located on the beams. Small arms and cannon weapons were located in the forward part of the fuselage.
The power plant was located at the rear of the fuselage behind the cockpit. The power was transmitted through a gearbox and elongated shafts to paired pusher screws that had counter-rotation. The latter eliminated the reaction torque and increased the efficiency of the propeller-motor group.
During takeoff and landing modes, the twin propellers, using a hydraulic drive, could be rotated down relative to the gearbox axis, thereby creating a vertical lift force. The two-beam design fully facilitated the free movement of the propellers, while in the deflected position they were slightly shaded by the fuselage and wing. When approaching the ground or when flying near it, the propellers were supposed to form an area of densified air under the aircraft, creating the effect of an air cushion. At the same time, their efficiency also increased.
Naturally, when the propellers turned down from the longitudinal axis, a diving moment arose, but it was countered in two ways. On the one hand, the deflection of the all-moving stabilizer, operating in the zone of active blowing of the propellers, to a negative angle. On the other hand, the deflection of the wing console in the chord plane forward by an angle corresponding to the balancing conditions for a given direction of the thrust vector. When the aircraft was transferred to horizontal flight after rising to a safe altitude, the propellers turned to their original position.
If this project were implemented, the proposed fighter could have a very short take-off distance, but for vertical take-off the power of the engines that existed at that time was clearly not enough. Therefore, for such a project, in order to reduce takeoff and landing distances, as well as takeoff and landing along a steep trajectory close to vertical, one or two high-power motors were required, operating synchronously on the same shaft.
Designed by K.B. Pelenberg's fighter project is interesting in that it used propeller thrust with great efficiency to create additional lift for the aircraft and aerodynamic balancing means that were unusual for that time - a movable wing or, as it is now called, a variable geometry wing, as well as a controlled stabilizer. It is interesting to note that these and some other technical innovations proposed by the designer in this project were significantly ahead of their time. However, later they found worthy application in aircraft construction.
The short take-off and landing fighter project remained a project, but it only strengthened the author’s desire to create a vertical take-off and landing aircraft. Konstantin Vladimirovich understood that the possibility of vertical takeoff opened up invaluable tactical opportunities for military aviation. In this case, aircraft could be based on unpaved airfields, using areas of limited size, and on the decks of ships. The relevance of this problem was clear even then. In addition, with the increase in the maximum flight speeds of fighters, their landing speeds inevitably increased, which made landing difficult and unsafe; in addition, the required length of the runways increased.
At the end of the Great Patriotic War, with the appearance in our country of captured German jet engines YuMO-004 and BMW-003 and then the Derwent-V, Nin-I and Nin-II engines purchased from the English company Rolls-Royce ", it was possible to successfully resolve many problems in the domestic jet aircraft industry. True, their power was still insufficient to solve the task, but this did not stop the work of the aircraft designer. At this time, Konstantin Vladimirovich not only worked in the design bureau of chief designer A.I. Mikoyan, but also taught at the Moscow Aviation Institute.
To the development of a fighter with vertical take-off and landing, which used a turbojet engine (TRD) as a power plant, K.V. Pelenberg started at the beginning of 1946 on his own initiative, and by the middle of the year the machine project was generally completed. As in the previous project, he chose a design with a fixed power plant, and vertical takeoff was provided by a variable thrust vector.
A feature of the proposed scheme was that the cylindrical nozzle of the jet engine ended in two symmetrically diverging channels, at the end of which nozzles rotating in a vertical plane were installed.
A significant advantage of the proposed device was the simplicity of the design, the absence of the need to alter the nozzle of the engine itself, and the comparative ease of control. At the same time, turning the nozzles did not require more effort and complex devices, as, for example, in the case of changing the thrust vector by turning the entire power plant.
The fighter developed by Konstantin Vladimirovich was a monoplane with a modified engine layout. The most powerful English turbojet engine “Nin-II” with a thrust of 2270 kgf was to serve as a power plant at that time. The air supply to it was carried out through the frontal air intake. When configuring the machine, one of the main requirements was that the axis of the thrust vector, when deflecting the nozzles, should pass near the center of gravity of the aircraft. Depending on the flight mode, the nozzles had to be rotated to the most favorable angles ranging from 0 to 70°. The greatest deflection of the nozzle corresponded to the landing, which was planned to be carried out at maximum engine operating mode. Changing the thrust vector was also supposed to be used to brake the aircraft.
Meanwhile, due to the placement of the power plant at an angle of 10-15° relative to the horizontal plane of the fighter, the range of deviation of the nozzles from the engine axis ranged from +15° to -50°. The proposed design fit well into the fuselage. The corresponding rotation and tilt of the plane of rotation of the nozzles made it possible not to space them too far from each other. In turn, this made it possible to increase the diameter of the channels - this rather critical parameter was optimized taking into account the midsection of the fuselage so that the channels fit into its dimensions.
Technologically, both channels connected to the fixed part, together with the rotation control mechanism, constituted one unit, which was connected to the cylindrical engine nozzle using a flange. The nozzles were attached to the ends of the channels using thrust bearings. In order to protect the movable joint from the effects of hot gases, the edges of the nozzle blocked the gap in the plane of rotation. Forced cooling of the bearings was organized by drawing air from the atmosphere.
To deflect the nozzles, it was planned to use a hydraulic or electromechanical drive mounted on the stationary part of the nozzle, and a worm gear with a gear sector mounted on the nozzle. The power drive was controlled either by the pilot remotely or automatically. Equality of rotation angles was achieved by simultaneous activation of the drives. Their control was synchronized, and the maximum deflection angle was fixed by a limiter. The nozzle was also equipped with guide vanes and a casing designed to cool it.
Thus, the gas jet has become a fairly powerful means of ensuring vertical takeoff and landing. Its use as a landing gear for a fighter with an engine thrust of about 2000 kgf reduced the wing area so much that it could actually be turned into a control element. A significant reduction in the dimensions of the wing, which at high Mach numbers, as is known, constitutes the main drag of the aircraft, made it possible to significantly increase the flight speed.
After getting acquainted with the project. A.I. Mikoyan advised K.V. Pelenberg to register it as an invention. The relevant documents were sent to the Bureau of Inventions of the Ministry of Aviation Industry on December 14, 1946. In the application, sent along with an explanatory note and drawings entitled “Rotary nozzle of a turbojet engine,” the author asked to register this proposal as an invention “to secure priority.”
Already in January 1947, a meeting of the expert commission at the technical department of the MAP was held under the chairmanship of Candidate of Technical Sciences V.P. Gorsky. The commission also included A.N. Volokov, B.I. Cheranovsky and L.S. Kamennomostsky. In its decision of January 28, the commission noted that this proposal was correct in principle and recommended that the author continue to work in this direction. Along with this, she noted that reducing the wing area is inappropriate, since in the event of a power plant failure, landing the aircraft would be problematic.
Soon, the aircraft project received constructive elaboration to such an extent that this gave the author the basis for its consideration in TsAGI, CIAM, OKB of Plant No. 300 and other organizations, where the project also received a positive assessment. As a result, on December 9, 1950, Application by K.V. Pelenberg was accepted for consideration by the Office of Inventions and Discoveries under the State Committee for the Introduction of Advanced Technology into the National Economy. At the same time, publication of the proposed invention was prohibited.
Of course, the project has not yet covered and could not immediately cover all the subtleties associated with the creation of a vertically taking off aircraft. Moreover, I had to work alone. But although many technical difficulties and new problems arose, even then it became clear that the project was real, that it was the beginning of a new direction in modern aviation.
The rotating nozzle alone did not solve all the problems that arise during vertical takeoff. As stated in the decision of the MAP expert commission,
“...when the direction of the gas jet changes, the stability and balance of the aircraft will change, which will cause difficulties in control during takeoff and landing.”
Therefore, in addition to changing the thrust vector, it was necessary to solve the issue of stabilizing the vehicle, since in the absence of air flow around the wing and tail, they no longer played the role of stabilizers.
In order to solve this problem, Konstantin Vladimirovich worked out several stabilization options. Firstly, the imbalance of the aircraft when the thrust vector is deflected in flight can be countered by changing the angles of attack of the stabilizer. Secondly, at low flight speeds, he proposed the use of an additional jet device (autonomous or using gas exhaust from the post-compressor part of the engine). Working on the second method was a daunting task, since without research and purging in a wind tunnel it was impossible to judge the behavior of the aircraft with a deflected gas jet near the ground.
The fact is that when initial transverse disturbances occur near the ground, the angular accelerations of the wing quickly increase, which lead to critical roll angles of the aircraft. When manually controlling lateral stabilization, the pilot, for subjective reasons, does not have time to react in time to the appearance of the initial roll. As a result of the delay in control input, as well as a certain inertia of the system, manual control cannot guarantee a quick and reliable restoration of the damaged lateral balancing. In addition, the gas flow coming down from the jet engine, capturing adjacent air masses, causes air to flow from the upper surface of the wing to the lower one, causing the pressure on top of the wing to increase and decrease below it. This reduces the wing's lift, reduces damping and makes it difficult to stabilize the aircraft in roll. Therefore, in particular, roll control required twice as much sensitivity as pitch control.
In this regard, in 1953 K.V. Pelenberg developed a lateral stabilization system for his VTOL fighter project. Its peculiarity was the use of two roll gyrostabilizers on the aircraft, which were placed on the wing (one in each console) at the maximum distance from the longitudinal axis of the machine. For their operation, part of the energy of the gas jet of the turbojet engine was used. The system was put into operation with the help of gyroscopes, which are sensors of the stabilized position of the aircraft in roll and at the same time distributors of the direction of restoring reactive forces.
When the aircraft rolled, the gyrostabilizers created two equal reactive moments applied to the consoles and acting in the direction opposite to the roll. As the aircraft's roll increased, the restoring moments increased and reached their maximum value when the maximum permissible roll angle was reached under safety conditions. Such a system had the advantage that it was put into operation automatically, without the participation of the pilot and without intermediate connections, was inertia-free, had high sensitivity and constant readiness for work, and also created conditions for aerodynamic damping of the wing.
Gyro-gas stabilizers were put into operation during takeoff and landing modes simultaneously with the rotation of the main nozzles of the turbojet engine and the transfer of the engines to vertical thrust. In order to stabilize the aircraft in all three axes, the pitch stabilization system was also put into operation at this moment. To turn on the roll stabilizers, the pilot opened the dampers located in the turbine part of the jet engine. Part of the gas flow, which had a speed of about 450 m/s in this place, rushed into the gas pipeline, and from there into the gyroblock, which directed it in the direction necessary for the roll to rise. When the flaps were opened, the upper and lower flaps automatically opened, covering the cutouts in the wing.
In the event that the aircraft wing occupied a strictly horizontal position relative to the longitudinal and transverse axes, the upper and lower windows of the right and left gyroblocks were open to half their size. Gas flows came out at equal speeds up and down, creating equal reaction forces. At the same time, the upward outflow of gas from the gyroblock prevented the flow of air from the upper surface of the wing to the lower one, and, consequently, the vacuum above the wing decreased when the engine thrust vector was deviated.
When a roll appeared, the gyro-gas stabilizer damper on the lowered wing console reduced the gas output upward and increased the gas output downward, and the opposite happened on the raised console. As a result, the reactive force directed upward on the lowered console increased and a restoring moment was created. On the rising wing console, on the contrary, the reactive force acting downward increased, and an equal restoring moment arose, acting in the same direction. When the roll was close to the maximum safe one, the gyroblock dampers opened completely - on the lowered console to allow gas to flow downwards, and on the raised console to allow gas to flow upwards, as a result of which two equal moments arose, creating a total restoring moment.
The main part of the developed stabilizer was the gyroscopic unit. Its front axle shaft was rigidly attached to the outer box, and the rear axle shaft was rigidly attached to the gas receiver. The axle shafts provided the gyroblock with free rotation relative to the axis, which, when installing the roll stabilizer in the wing, had to be positioned strictly parallel to the longitudinal axis of the aircraft. In the plane of connection of the gas receiver with the hyroblock there was a shaped window, partially closed at the bottom and top with a damper. In this plane, the gyroblock and the receiver approached each other with a minimum gap, ensuring free rotation of the gyroblock. To avoid unnecessary gas leakage, the joining plane had a labyrinth seal.
The receiver housed a gas distribution mechanism. Its role was to direct the gas flow from the main line to the upper or lower chambers of the gyroblock, which then flowed out through the windows between the blades of the gyroblock disks. Depending on which direction the block was turned, the damper closed either the upper window or the lower one, transferring gas from the main line into one of the chambers. When the gyroscope was operating, the block constantly maintained a horizontal position, and the rotation of the damper and the bypass of gas into the chambers occurred as a result of the rotation of the gas receiver relative to the transverse axis caused by the tilt of the wing. The greater the roll angle, the more one gyroblock window opened and the other closed.
The gyroblock was installed in a rigid box, onto which two pairs of shields were attached using hinges, covering the cutouts in the wing at the top and bottom. In the closed position, the flaps fit snugly to the slats and the rest of the wing surface, without disturbing its contour. They were also opened by the pilot simultaneously with the gas valve of the jet engine.
The gyrostabilizers were mounted in the wing consoles in such a way that the planes of the gyroscopes lay in the plane of the longitudinal and transverse axes of the aircraft. For aircraft of relatively small sizes, which can have significant angles of oscillation in pitch, in order to avoid the phenomenon of gyroscope precession, it was planned to introduce a parallelogram connection between the transverse axes of the right and left gyroblocks to hold them together.
According to calculations, lateral stabilization of a vertical take-off fighter weighing 8000 kg with an aircraft thrust-to-weight ratio equal to one and power taken from the turbojet engine of 3-4% could be provided by gyrostabilizers located 2.25 m from the longitudinal axis. In this case, they were sufficient diameter 330 mm, height - 220 mm, length of the outer box - 350 mm, width of the inner box - 420 mm, gas pipeline diameter - 142 mm, distance between the axes of the block and the gas pipeline - 295 mm. Such wing installations could create righting moments of 100 kgm each at a roll angle of 10°, and 220 kgm at a roll angle of 25-30°.
However, this vertical take-off and landing fighter project was not destined to come true at that time - it was also far ahead of the technical capabilities of that time. And official circles were very skeptical about him. Since in the USSR the planned economy, which was elevated to an absolute level, apparently also implied planned inventions, there was always a lack of free working capital in design bureaus for their own large-scale R&D. Thus, the initiative project for a domestic vertical take-off and travel aircraft remained on paper in the future.
Meanwhile, in the UK the idea of developing a vertical take-off and ride (VTOL) jet aircraft was taken more seriously. In 1957, the company "Hauker Siddley" proactively began to develop such an aircraft, and although they also had no experience in creating machines of this class, after only three years the experimental fighter R. 1127 "Kestrel" took off. And six years later, an experimental Harrier attack aircraft was built on its basis - a prototype of vehicles of the same name, now adopted not only by the British Royal Air Force but also by other countries of the world.
In the Soviet Union, perhaps only the LII actually studied the possibility of creating a vertical take-off and landing jet aircraft. In 1958, a group led by A.H. Rafaelians, developed and built an experimental device called the “Turbolet”.
His flights proved the fundamental possibility of creating an aircraft with jet control in vertical take-off, hovering and landing modes, as well as during the transition to horizontal flight. However, the idea of creating a vertical take-off and landing aircraft had not yet captured the minds of the official authorities, although the “portfolio” of domestic designers included a project for such an aircraft and the experience accumulated during testing of the “Turbolet”.
It was only at the end of 1960, when the R. 1127 Kestrel aircraft was already flying, and the first detailed publications about it appeared that it seemed to “break through” in official circles. The Central Committee of the CPSU and the Council of Ministers of the USSR thought seriously and decided once again to “catch up and overtake the decaying West.” As a result, after almost a year of correspondence between all interested organizations, work on the design and construction of a vertical take-off and landing aircraft, on the basis of their joint Resolution of October 30, 1961, was entrusted to OKB-115 by chief designer A.S. Yakovleva. The development of the power plant was entrusted to OKB-300, chief designer S.K. Tumansky. True, it is worth noting that back in 1959, Deputy Chairman of the Council of Ministers of the USSR D.F. Ustinov, Chairman of the State Committee on Aviation Technology P.V. Dementiev and Commander-in-Chief of the Air Force SA K, A. Vershinin prepared a draft Resolution, in which they planned to entrust the creation of an experimental fighter with vertical takeoff and landing to the Design Bureau of Chief Designer G.M. Berneva.
In the fall of 1962, the first of three prototypes of the aircraft, named Yak-Zb, intended for laboratory bench tests, left the assembly shop; on January 9, 1963, test pilot Yu.A. Garnaev performed the first tethered hanging on the second copy of the Yak-Z6, and on June 23 - free. During the tests Yu.A. Garnaev was replaced by test pilot V.G. Mukhin, who on March 24, 1966 performed the first vertical takeoff and landing flight on the third experimental machine. The Yak-Zb power plant was powered by two R-27-300 turbojet engines equipped with rotating nozzles. Subsequently, the experience of building and testing the experimental Yak-36 aircraft served as the basis for the creation of the combat VTOL aircraft Yak-38 (Yak-ZbM), which was put into serial production and was used by the Navy aviation.
Meanwhile, on August 29, 1964 (18 years later!) the State Committee for Inventions and Discoveries issued K.V. Shulikov (Pelenberg) copyright certificate No. 166244 for the invention of a rotating jet engine nozzle with priority dated December 18, 1946. However, at that time the USSR was not a member of the international organization for inventions and discoveries, and therefore this project could not receive worldwide recognition, since as copyright applied only to the territory of the USSR. By this time, the rotary nozzle design had found practical application in aircraft engineering, and the idea of a vertically taking off aircraft was becoming widespread in world aviation. For example, the aforementioned English R.1127 Kestrel was equipped with a Pegasus turbojet engine with four rotary nozzles.
In October 1968, P. O. Sukhoi, in whose design bureau Konstantin Vladimirovich worked by this time, sent a petition to S. K. Tumansky to pay the author a remuneration, since the enterprise headed by the latter had mastered the serial production of jet engines with a nozzle device made according to the proposed K.V. Shulikov scheme. As Pavel Osipovich noted in his address, in terms of its technical significance, this invention was one of the largest that have been made in the field of aviation technology.
And on May 16, 1969, P. O. Sukhoi’s appeal was supported by A. A. Mikulin, who emphasized that the invention of K.V. Shulikov was reviewed by him back in 1947, and “regarded as a new, interesting technical solution that promises in the future a real prospect of using engine thrust to facilitate takeoff and landing of aircraft.” In addition, by this time, positive conclusions had been received on the 1946 VTOL project from CIAM (No. 09-05 dated April 12, 1963, signed by V.V. Yakovlevsky), TsAGI (No. 4508-49 dated January 16, 1966, signed G.S. Byushgens), technical council of OKB-424, as well as the decision of BRIZ MAP (dated July 22, 1968).
The application for payment of remuneration for the invention of the rotary nozzle was considered at a meeting of the OKB-300 technical council held on October 10, 1969. During the discussion, it was noted that the proposed K.V. Shulikov’s rotary nozzle scheme was first introduced in the USSR on the R-27-300 engine (edition 27), that is, its use made it possible to create the first domestic design of this class. In addition, this scheme was also developed three times by the development of the P-27B-300 engine (ed. 49). In confirmation of this, the technical council 0KB-ZO0 was presented with an act on the implementation of the invention under copyright certificate No. 166244, which was drawn up by the head of the OKB M.I. Markov and the responsible representative of BRIZ OKB I.I. Motin, The act noted that
Since the engines created according to this scheme were a new promising direction in the development of technology, the royalty was set at 5,000 rubles. Thus, the technical council of OKB-300 recognized that the work of K.V. Shulikova formed the basis for the creation of the first domestic aircraft with vertical take-off and landing.
Taking this into account, the scientific and technical council of the MAP Technical Directorate, chaired by IT. Zagainova in October 1969 considered it legitimate
“recognize the priority in the technical development of the project for the first vertically taking off aircraft to domestic aviation technology.”
Based on the great technical significance and prospects that this invention had, which anticipated the advent of vertical take-off and landing aviation for many years to come, and the resulting primacy of domestic aviation in the development of this field of technology, the scientific and technical council assessed it as a technical improvement close to in terms of its significance to the technical discovery, and recommended that the author be paid the due remuneration.
This is a brief history of the world's first vertical take-off aircraft project. And although the brainchild of an outstanding engineer and designer K.V., passionate about the technical concept. Shulikov in the Soviet Union was not embodied in metal; this does not detract from the rights of the author and domestic aviation science and technology to priority in the creation of vertical take-off aviation.
Documentary materials kindly provided by K.V. were used in preparing the publication. Shulikov from his personal archive, as well as documents from the Russian State Archive of Economics.
Curriculum Vitae
SHULIKOV (PELENBERG) Konstantin Vladimirovich
Konstantin Vladimirovich Shulikov (Pelenberg) was born on December 2, 1911, in the city of Pskov in the family of a military man. In 1939, he graduated with honors from the aircraft engineering department of the Moscow Aviation Institute with the qualification of a mechanical engineer. His practical activities in the aviation industry K.V. Shulikov started in 1937, combining work with studies at the institute. As an employee of the Design Bureau of Chief Designer N.N. Polikarpov, he went from a design engineer to the head of the KB-1 wing sector. Participated in the design and construction of the I-153 Chaika and I-180 fighters.
From December 1939 to 1951 K.V. Shulikov worked in the Design Bureau of Chief Designer A.I. Mikoyan, where he took an active part in the development and construction of MiG-1, MiG-3, I-250, I-270, MiG-9, MiG-15, MiG-17 fighters, the experimental MiG-8 “Duck” and other aircraft. In the spring of 1941, he was sent as part of the brigade of plant No. 1 named after. Aviakhim is at the disposal of the Air Forces of the Western Special and Baltic Special Military Districts to assist the flight technical personnel of combat units in mastering the MiG-1 and MiG-3 fighters. The team’s task also included eliminating deficiencies identified during operation and refining the equipment according to the manufacturer’s bulletins. During the Great Patriotic War, Konstantin Vladimirovich took part in the restoration of MiG-3 fighters, which were in service with the aviation regiments of the Western Front Air Force and the 6th IAK Air Defense of Moscow. In 1943, he developed a technology for manufacturing soft fuel tanks.
In parallel with his work at OKB-155, from 1943 to 1951, K. V. Shulikov did a lot of part-time teaching at the Moscow Aviation Institute, where he was a member of the Aircraft Design department. He gave about 600 hours of lectures on aircraft design for 5th year students, he was also the supervisor of diploma projects, a reviewer and took part in the development of teaching aids for students and graduates.
In 1951, in accordance with the order of the MAP, Konstantin Vladimirovich was transferred to work at Aviastroyspetstrust No. 5, and in 1955 - at the disposal of OKB-424 of plant No. 81 of the MAP. In 1959, he moved to the Design Bureau of General Designer S.A. Lavochkin, where he led the development and organization of an automatic guidance point for the Dal missile system at the Saryshagan training ground in the area of Lake Balkhash. Since 1968 K.V. Shulikov continued his career in the Design Bureau of General Designer P.O. Sukhoi. He was an active participant in the development and construction of the T-4 supersonic missile-carrying aircraft.
From 1976 to 2003, Konstantin Vladimirovich worked at the Molniya Research and Production Association, headed by G. E. Lozino-Lozinsky. He took part in the design and creation of the reusable spacecraft "Buran", its analogue and experimental samples. Many of the technical solutions he proposed were accepted for development and production.
K.V. Shulikov owns a number of scientific works and more than 30 inventions in the field of aviation and astronautics. With his participation (joint TsAGI, TsNII-30 MO, NII-2 MAP), research work was carried out on the “Research of the aerospace complex for air launch of missiles,” including “Study of the appearance of the aircraft booster of the product “100” V.N. Chelomeya based on the T-4 supersonic aircraft." He developed a project for a vertical take-off and landing aircraft, projects for various systems in the field of stabilization and controllability of aircraft, a project for a stabilizing platform for a high-altitude astronomical station of the USSR Academy of Sciences for lifting a large telescope weighing 7.5 tons into the stratosphere, a project for an inflatable ladder for cosmonauts to work in outer space and other.
Ladoga-9 UV
Recently, he has developed projects for twin-engine multi-purpose amphibious aircraft “Ladoga-bA” with 6 seats and “Ladoga-9I” with 9-11 seats. In 1997, the Ladoga-bA amphibious aircraft project was awarded the Gold Medal at the Brussels-Eureka-97 world exhibition.
Or parts of it.
Encyclopedic YouTube
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The first experiments related to the practical implementation of variable thrust vectoring on aircraft date back to 1957 and were carried out in the UK as part of a program to create a combat aircraft with vertical take-off and landing. The prototype, designated P.1127, was equipped with two 90° rotating nozzles located on the sides of the aircraft at the center of gravity, which provided movement in vertical, transitional and horizontal flight modes. The first flight of the R.1127 took place in 1960, and in 1967, the first production VTOL aircraft, the Harrier, was created on its basis.
A significant step forward in the development of engines with variable thrust vectoring within the framework of VTOL programs was the creation in 1987 of the Soviet supersonic VTOL Yak-41. The fundamental distinguishing feature of this aircraft was the presence of three engines: two lifting and one lifting-propulsion with a rotating nozzle located between the tail booms. The three-section design of the lift-propulsion engine nozzle made it possible to rotate downwards from a horizontal position by 95°. \
Expansion of maneuverability characteristics
Even during the work on the R.1127, testers noticed that the use of a deflected thrust vector in flight somewhat facilitates the maneuvering of the aircraft. However, due to the insufficient level of technology development and the priority of VTOL programs, serious work in the field of increasing maneuverability through high-tech aircraft was not carried out until the end of the 1980s.
In 1988, based on the F-15 B fighter, an experimental aircraft was created with engines with flat nozzles and thrust vector deflection in the vertical plane. The results of test flights showed the high efficiency of OVT for increasing aircraft controllability at medium and high angles of attack.
At approximately the same time, an engine with an axisymmetric deflection of a circular cross-section nozzle was developed in the Soviet Union, work on which was carried out in parallel with work on a flat nozzle with a deflection in the vertical plane. Since installing a flat nozzle on a jet engine is associated with a loss of 10-15% of thrust, preference was given to a round nozzle with axisymmetric deflection, and in 1989 the first flight of the Su-27 fighter with an experimental engine took place.
Operating principle
A scheme with flow deflection in the subsonic part is characterized by the coincidence of the mechanical deflection angle with the gas-dynamic one. For a circuit with deflection only in the supersonic part, the gas-dynamic angle differs from the mechanical one.
The design of the nozzle diagram shown in rice. 1a, must have an additional unit that ensures deflection of the entire nozzle. Nozzle diagram with flow deflection only in the supersonic part on rice. 1b in fact, it does not have any special elements to ensure deviation of the thrust vector. The differences in the operation of these two schemes are expressed in the fact that to ensure the same effective angle of deflection of the thrust vector, the scheme with deflection in the supersonic part requires large control torques.
The presented schemes also require solving the problems of ensuring acceptable weight-dimensional characteristics, reliability, service life and speed.
There are two thrust vector control schemes:
- with control in one plane;
- with control in all planes (with all-angle deflection).
Gas-dynamic thrust vector control (GUVT)
High efficiency of thrust vector control can be achieved using gas-dynamic thrust vector control (GUVT) due to the asymmetric supply of control air into the nozzle path.
A gas-dynamic nozzle uses a “jet” technique to change the effective area of the nozzle and deflect the thrust vector, while the nozzle is not mechanically adjustable. This nozzle has no hot, highly loaded moving parts; it fits well with the aircraft structure, which reduces the weight of the latter.
The outer contours of the fixed nozzle can blend seamlessly with the contours of the aircraft, improving the design's low-observability characteristics. In this nozzle, air from the compressor can be directed to the injectors in the critical section and in the expanding part to change the critical section and control the thrust vector, respectively.
The formation of control forces is ensured by the following order of operations.
- In the first phase of nozzle operation (Fig. 5) increase the angle of deflection of the flaps of the diverging part of the nozzle - angle α installation of exit flaps of the expanding part 3 nozzles
- In the second phase (Fig. 6), in the mode of generating control forces on part of the nozzle surface, the dampers open 8 for atmospheric air to enter parts of the side surface of the expanding part of the nozzle 3 . On Fig.6 view shown A and the direction of atmospheric air flow through open holes with dampers on part of the side surface. Switching dampers 8 on the opposite half of the lateral expanding part of the nozzle leads to deflection of the jet and the engine thrust vector at an angle β in the opposite direction.
To create control forces in an engine with a supersonic nozzle, you can slightly change the supersonic part of an existing nozzle. This relatively simple upgrade requires minimal changes to the main parts and assemblies of the original, standard nozzle.
During design, most (up to 70%) of the components and parts of the nozzle module may not be changed: the mounting flange to the engine body, the main body, the main hydraulic drives with fastening units, levers and brackets, as well as the critical section flaps. The designs of the flaps and spacers of the expanding part of the nozzle are changing, the length of which increases, and in which holes were made with rotary dampers and hydraulic actuators. In addition, the design of the external flaps is changed, and the pneumatic cylinders for them are replaced with hydraulic cylinders, with a working pressure of up to 10 MPa (100 kg/cm2).
Deflectable thrust vector
Deflectable thrust vector (OVT) - function of the nozzle, changing the direction of the jet stream. Designed to improve the tactical and technical characteristics of the aircraft. An adjustable jet nozzle with a deflectable thrust vector is a device with variable critical and outlet cross-section sizes depending on the engine operating modes, in the channel of which the gas flow is accelerated in order to create jet thrust and the ability to deflect the thrust vector in all directions.
Application on modern aircraft
Currently, the thrust vector deflection system is considered as one of the mandatory elements of a modern combat aircraft due to the significant improvement in flight and combat qualities caused by its use. Issues of modernizing the existing fleet of combat aircraft that do not have OVT are also being actively studied by replacing engines or installing OVT units on standard engines. The second option was developed by one of the leading Russian manufacturers of turbojet engines - the Klimov company, which also produces the world's only serial nozzle with all-angle thrust vector deflection for installation on the RD-33 engines (family of MiG-29 fighters) and AL-31F (brand fighters Su).
Combat aircraft with thrust vectoring:
With axisymmetric thrust vector deviation
- Su-27SM2 (AL-31F-M1 engine, Product 117S)
- Su-30 (AL-31FP engine)
- PAK FA (prototype)
- F-15 S (experimental)
In slalom, the rolls are identical, that is, they are also high, but there is no trace of understeer! At the same speed where the “unsystematic” version was sliding its front end with all its might, the Outlander Sport simply turns and goes on. The contrast is especially striking on an arc with a decreasing radius, where the car’s behavior seemed completely unrealistic. If the regular version could hardly complete this exercise at a speed of 30 km/h, then the new modification, which has S-AWC, easily completed it at 40 km/h.
The car behaves much more confidently both on the circle (sliding begins later) and during the “rearrangement”, which can also be completed at a higher speed and, unlike the regular version, with almost no drift. In short, the behavior of the Outlander Sport in extreme modes cannot be called anything other than miraculous - the crossover seems to ignore the laws of physics. Now let's see if the difference will be noticeable when driving on public roads.
Almost an athlete
First, let's remember the sensations of driving a regular Outlander, without the Sport prefix in the name, that is, without S-AWC. The crossover stands perfectly on a straight line, ignores bumps and ruts, but when quickly entering corners, the driver has a feeling of uncertainty due to large rolls and a lack of reactive force on the steering wheel. But if you drive calmly, everything returns to normal. The smoothness of the ride is excellent, although the chassis can no longer cope with frankly broken asphalt. However, in the vicinity of St. Petersburg, where the test took place, the roads are so bad in some places that it’s time to drive a tank rather than a car. Among the shortcomings, I note a clear deterioration in the smoothness of the ride on the rear sofa compared to the front seats. In addition, second-row passengers hardly hear those sitting in front due to the strong tire noise.
It is worth saying that this car was produced in 2013. And in 2014, the crossover received very significant improvements. So I have the opportunity not only to find out how the Outlander Sport modification drives, but also to evaluate other innovations in practice. First of all, I note a more assembled suspension, which began to replicate the microprofile of the asphalt in a little more detail. But the updated chassis better withstands serious impacts and is more resistant to roll under normal driving conditions. Since 2014, all Outlander modifications have received this suspension.
But the tighter steering wheel is the exclusive prerogative of the Outlander Sport version. And the feeling of the car has become completely different: it feels like it has tensed its muscles, and I no longer feel insecure when taking turns quickly. Moreover, the behavior of the crossover has sporty notes! I like this car much better.
In addition, comfort for rear passengers has been significantly improved, primarily acoustic. All modifications of the 2014 Outlander received additional sound insulation, and this is noticeable to the naked ear - now I can calmly talk with the driver while sitting on the back seat. And the stiffer suspension, surprisingly, turned out to be less shaking. Yes, yes, this happens when the chassis is configured correctly.
As for S-AWC, its operation is not felt at all during normal driving. This is to be expected. The system does its job unnoticed, for which honor and praise be given to it. In short, the Mitsubishi Outlander is getting better every year. In 2015, the crossover will undergo a global update. So, we are waiting for a new meeting.
Technical characteristics of Mitsubishi Outlander Sport 3.0
Differential equation
How does the thrust vector control system work?
Differential equation
How does the thrust vector control system work?
Pavel Mikhailov, published May 02, 2017Photo: Manufacturing companies
There is a differential in any car, but why is it needed? What is an “active differential” with torque vectoring function - and why does it help turn? Let's find out!
When driving, all the wheels of a car rotate at different speeds. If only because the road is uneven, and if one of the wheels hits a bump, then it travels a greater distance than all the others driving on a flat road. But when turning, everything is really bad: each of the four wheels travels along its own radius (pay attention to the tracks left by cars in the snow).
And if this is not a problem for non-driving wheels, then with drive wheels everything is not so simple. When two drive wheels are connected by a rigid shaft, the tires will constantly slip or slip, which means they will wear out quickly. At the same time, fuel consumption will increase, and the car will handle worse. To avoid these problems, cars are equipped with differentials.
The inventor of the differential is considered to be the French mathematician Onesiphore Peccoeur, and the event itself dates back to 1825. Although, according to some sources, a similar device existed in Ancient Rome, let’s leave the question of history to the specialists. In this article we will pay more attention to a relatively young system known as torque vectoring, which translated from English means “thrust vector control”.
First, it’s worth understanding how a differential works in general. It consists of four main elements: the housing, the satellites, the satellite axis and the axle gears. The principle of its operation is simple: the differential housing is rigidly connected to the driven gear of the main gear, the axis of the satellites is rigidly connected to the housing. Torque is transmitted to the body, from it to the axis of the satellites and, accordingly, to the satellites themselves - and they, in turn, transmit force to the gears of the axle shafts.
Remember how, as a child, you balanced a friend of the same build on a swing - you could hang in the air without touching the ground. In a differential, the axle shaft gears are the same, so the force arm for the left and right axle shafts is also the same, which means the torque on the left and right wheels is the same.
The differential allows the wheels to spin in different directions relative to each other. Try turning one drive wheel on the lift - the second one will rotate in the opposite direction. However, relative to the car, these wheels rotate in one direction - after all, the differential housing also rotates! It's like walking backwards on a bus and still moving away from the person remaining at the stop. So, it turns out that the two wheels rotate with the same force and have the ability to do this at different speeds. This is shown as clearly as possible in the video:
This design has a disadvantage: both wheels receive the same torque, and to make the car turn better, it would be nice to supply more torque to the outer wheel. Then, when you press the gas, the car will literally spin into the turn - and the effect will be much more pronounced than on a car with a single-axle drive and a free differential. But how to implement such a system in a real design?
Today, such systems are becoming increasingly popular. The phrase “torque vectoring” itself was first heard in 2006, but a similar system, called Active yaw control, appeared on rally tracks in the nineties: it was equipped with the Mitsubishi Lancer Evolution IV, which debuted in 1996. But before we look in detail at the design of a full-fledged differential with a torque vectoring system, let's first take a look at its simplified analogue used in the Ford Focus RS. A similar system is used in the transmission of Land Rover Discovery Sport and Cadillac XT5.
The system is quite simple - it's even a little simpler than traditional all-wheel drive, because it doesn't have a rear differential. There are only two couplings, each of which connects its own axle shaft. When driving in a straight line without slipping, the car remains front-wheel drive, the rear wheels are engaged only when slipping and turning (in a left turn - the right rear wheel, and vice versa). The wheel can receive up to 100% of the torque going to the rear axle, thereby the system compensates for the resulting understeer, as if turning the car.
But what if there is only one drive axle, and in quiet modes a differential is required, and an open one at that, but in a turn you want to supply more torque to the outer wheel in order to more effectively control the car with gas, and also reduce understeer?
Such solutions also exist in the modern automotive industry. For example, the latest generation Lexus RC F and GS F are equipped with a rear differential that can distribute torque between the left and right wheels. In such a unit in the rear gearbox, the main gear rotates the housing of the most ordinary differential; there are also two overdrive planetary gears, which, with the help of a clutch pack, can connect the differential housing to the axle shaft. Thus, additional torque is supplied to the outer wheel through a planetary gear, due to which the effect of screwing into a turn occurs.
A similar solution was applied to the rear axle of the all-wheel drive BMW X6 M and X5 M - for both BMW and Lexus, and for Cadillac and Land Rover, the system was developed and manufactured by GKN. The difference, by and large, is only in the final drive housing: for example, BMW has it in aluminum, while Lexus has it in cast iron. The drive of friction clutches from both manufacturers is mechanical, it is carried out by identical GKN clutches.
Audi cars with an optional sports differential also have a similar system, but instead of planetary gears, these are simple internal gears. But the principle of operation is absolutely the same: using a clutch pack, two gears are connected, and the axle shaft is connected to the differential housing through an overdrive. For a more complete understanding, you can watch this video:
How big is the effect of using advanced differentials? The American magazine Car and Driver conducted a comparative test of two Lexus RC Fs, one of which was equipped with a torque vectoring differential system, and the second with a conventional “self-block”. As a result of higher maximum accelerations, lower steering angles and better lap times for the car with the active differential, the car's character has changed towards oversteer. And I’m glad that it is available not only for sports cars, but also for the compact crossover Nissan Juke - albeit in a somewhat simplified version.
For now, don’t expect that such systems will replace traditional differentials - after all, they are more complex, more expensive and more needed by active drivers. However, with the advent of the era of electric vehicles, the broadest opportunities for controlling thrust vectoring will appear: after all, if each drive wheel has its own electric motor, then the implementation of the torque vectoring effect will only be a matter of software.
