The history of this project dates back to the early 80s. At the experimental machine-building plant named after V. M. Myasishchev, design and research work was carried out to develop the concept of a new heavy-duty aviation transport system.
In the early 80s of the last century, similar work was carried out in several aviation design bureaus and, of course, in the scientific center of domestic aviation TsAGI.
The concept of a heavy transport aircraft developed at TsAGI is quite well known in aviation circles; the author of the development was the head of design research, Yu. P. Zhurikhin.
The demonstration model of the TsAGI transport system has been repeatedly demonstrated at international aviation exhibitions.
Design developments of EMZ named after. V. M. Myasishchev were carried out within the framework of the topic, which received the index “52”. They were carried out under the leadership of the chief designer of the EMZ V. A. Fedotov, the theme leader at the initial stage was the deputy chief designer R. A. Izmailov. The leading designer on the topic and essentially the author of the concept was V. F. Spivak.
The concept of Project 52 provided for the creation of a unified transport aircraft with unique transport capabilities. The main task The project was to ensure the air launch of a reusable aerospace rapid response aircraft. It would not be economically feasible to create such a unique aircraft with a take-off weight of 800 tons for only one task. Therefore, from the very beginning, the concept of the “52” project provided for the use of this aircraft for unique transport operations, including transportation military equipment and military units, industrial cargo beyond large size and weight.
The design concept of “52” was based on the “external load” principle. Only this principle makes it possible to place loads that are completely different in shape and size. In this case, the aircraft fuselage practically degenerates as a means of accommodating the load, therefore, by maintaining the minimum required size of the fuselage, it would be possible to significantly reduce the weight of the aircraft structure. That's all, it would seem very simple idea on the basis of which the entire project is built.
In this article we will not consider the “52” project in detail. We will refer those interested to the multi-volume publication “Illustrated Encyclopedia of Aircraft EMZ named after. V.M. Myasishchev”, where the development of the project is described in sufficient detail.
The author of these lines had to directly participate in these works, and in this article I would like to talk about those projects, or more correctly, ideas that were also considered in the process of developing the concept, but were not developed and were not worked out in sufficient detail.
The very idea of creating a super-heavy transport aircraft did not arise on its own. Ministry aviation industry(MAP) was given the specific task of transporting large-sized cargo in the interests of the national economy of the country.
The USSR, with its vast territories and large industrial centers scattered throughout the country, needed a solution to this problem, because it is obvious that it is more economically profitable to transport ready-made and assembled units.
Nuclear reactors, metallurgical convectors, gas tanks and distillation columns chemical production and many other cargoes, all of them, when transported assembled “by air”, could be put into operation quite quickly, which means less time and correspondingly lower costs.
Any transport operation “on the ground” is a whole event for many transport services. Detailed study of the route, demolition of bridges and overpasses, power lines if they interfere with transportation, and so on... These are the timing, these are the costs, in some cases this is simply an insoluble problem.
Cargoes weighing from 200 to 500 tons, with overall dimensions ranging from 3 to 8 m in diameter and 12 m to 50 m in length were intended for transportation. It is clear that, of course, not all of the proposed cargo could be transported by air, but the project “52” could transport most of the cargo if it were implemented.
So the idea arose not only to reduce the size of the fuselage to the minimum possible, but to abandon it altogether. Why not make the transported cargo itself “work”? This idea was prompted by the fact that many cargoes intended for transportation looked like elongated cylindrical bodies, that is, they looked like a fragment of the fuselage.
Of course, the cargo itself, the material from which it was made and its design had to satisfy the strength conditions when installing it on an airplane. The inclusion of cargo in the aircraft's power circuit promised a significant gain in the aircraft's weight efficiency and, accordingly, increased its transport efficiency.
How can the transported cargo itself be included in the power scheme of a transport aircraft? It’s very simple, you need to make the transported cargo winged! There is such an aerodynamic design of the aircraft called “tandem”. In this scheme, the aircraft's supporting system consists of a pair of wings arranged tandemly behind each other with longitudinal spacing. The transported cargo is located between the wings precisely in the center of gravity of the entire supporting system of the aircraft, everything is very simple, although it is well known what a big problem solving the problem of centering a heavy cargo poses.
The tandem scheme has a slightly larger area of the aircraft's load-bearing system compared to the classical scheme, but this scheme turns out to be the most suitable for cargo transportation tasks.
Both wings generate lift without losing lift to the longitudinal trim inherent in a classic aircraft design. Optimal profiling of both wings and degradation of their installation angles make it possible to minimize the negative impact of wing interference and therefore reduce aerodynamic losses.
One of the variants of the tandem aircraft consisted of two independent sections with a full-fledged wing with mechanization of the leading and trailing edges. The wing of the front section is made according to a low-wing design to reduce the effect of the flow bevel on the rear wing. The power plant engines are installed on vertical pylons on top of the front section wing. The pylon engine suspension is considered to be quite universal, allowing the required number of engines to be varied during the development process.
The location of the engines above the upper surface of the wing made it possible to use the effect of increasing the lifting force of the wing due to the jet blowing over the engines (Coanda effect). Due to the greater load on the front wing, the front wing was made with a slightly smaller area compared to the rear wing.
The front section is equipped with its own chassis - the main one, consisting of two four-wheeled main supports and two two-wheeled underwing supports. The spacing of the main and underwing landing gear along the longitudinal axis of the aircraft ensured the longitudinal stability of the front section at the airfield in the undocked position.
On top of the front section behind the cockpit there is a rear-facing glazed cabin for the load operators, who monitor the condition of the cargo and the load securing systems during the flight.
The rear section of the tandem aircraft is similar to the front. The wing of the rear section is overhead, with a slightly larger span. Vertical tail washers are installed on the rear wing. Due to the small effective shoulder, the vertical tail is made of a large area, with two fins.
The rear section of the tandem aircraft does not have engines; the landing gear is designed similarly to the front section. Due to the high location of the wing on the rear section, the underwing landing gear is attached to the vertical tail washers.
An important feature of the “tandem” scheme is also that when the aircraft takes off from the runway, the aircraft takes off flat-parallel, with virtually no pitch angle; this feature of the “tandem” is ideal for transporting long loads, since the explosion of an aircraft on takeoff with a long externally slung cargo becomes problematic for a classic aircraft.
To secure various loads, transitional ring trusses were provided, adapted to the specific load.
In order to increase the transport efficiency of the tandem aircraft, it was also planned to use a passenger module closed between the front and rear sections of the aircraft.
The open-loop design of the tandem aircraft made it possible to adapt the aircraft to loads of various lengths, this made the aircraft efficient vehicle. In the case of an empty aircraft, both sections were joined using connecting ring trusses.
The design of a tandem aircraft with a truss fuselage looked less radical.
Fundamentally, the idea of the concept remained the same, but the fuselage was still preserved, albeit in a somewhat exotic form - two fuselage beams in the form of spatial trusses. A special feature of this tandem aircraft design was that the rear wing with its landing gear and cargo fastening units could move along the trusses to the desired position, depending on the size of the cargo being transported and its alignment. In all other respects, the concept repeated the first scheme. The shortcomings of this scheme were clearly visible, but the only positive thing was that the search for further productive ideas lay through these schemes.
The “tandem” scheme has not yet exhausted itself, perhaps it will find a worthy application in the very near future, we’ll see.
Source. V. Pogodin Valery Pogodin. Tandem - a new word in aviation? Wings of the Motherland 5/2004
: forward control planes without a rear tail.
Advantages
Also, various variations of the canard design are used for many guided missiles.
see also
Write a review about the article "Duck (aerodynamic design)"
Literature
- Flight tests of aircraft, Moscow, Mechanical Engineering, 1996 (K. K. Vasilchenko, V. A. Leonov, I. M. Pashkovsky, B. K. Poplavsky)
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An excerpt characterizing the Duck (aerodynamic design)
The horses were brought in. Denisov became angry with the Cossack because the girths were weak, and, scolding him, sat down. Petya took hold of the stirrup. The horse, out of habit, wanted to bite his leg, but Petya, not feeling his weight, quickly jumped into the saddle and, looking back at the hussars who were moving behind in the darkness, rode up to Denisov.- Vasily Fedorovich, will you entrust me with something? Please... for God's sake... - he said. Denisov seemed to have forgotten about Petya’s existence. He looked back at him.
“I ask you about one thing,” he said sternly, “to obey me and not to interfere anywhere.”
During the entire journey, Denisov did not speak a word to Petya and rode in silence. When we arrived at the edge of the forest, the field was noticeably getting lighter. Denisov spoke in a whisper with the esaul, and the Cossacks began to drive past Petya and Denisov. When they had all passed, Denisov started his horse and rode downhill. Sitting on their hindquarters and sliding, the horses descended with their riders into the ravine. Petya rode next to Denisov. The trembling throughout his body intensified. It became lighter and lighter, only the fog hid distant objects. Moving down and looking back, Denisov nodded his head to the Cossack standing next to him.
- Signal! - he said.
The Cossack raised his hand and a shot rang out. And at the same instant, the tramp of galloping horses was heard in front, screams from different sides and more shots.
At the same instant as the first sounds of stomping and screaming were heard, Petya, hitting his horse and releasing the reins, not listening to Denisov, who was shouting at him, galloped forward. It seemed to Petya that it suddenly dawned as brightly as the middle of the day at that moment when the shot was heard. He galloped towards the bridge. Cossacks galloped along the road ahead. On the bridge he encountered a lagging Cossack and rode on. Some people ahead - they must have been French - were running from the right side of the road to the left. One fell into the mud under the feet of Petya's horse.
Cossacks crowded around one hut, doing something. A terrible scream was heard from the middle of the crowd. Petya galloped up to this crowd, and the first thing he saw was the pale face of a Frenchman with a shaking lower jaw, holding onto the shaft of a lance pointed at him.
“Hurray!.. Guys... ours...” Petya shouted and, giving the reins to the overheated horse, galloped forward down the street.
Shots were heard ahead. Cossacks, hussars and ragged Russian prisoners, running from both sides of the road, were all shouting something loudly and awkwardly. A handsome Frenchman, without a hat, with a red, frowning face, in a blue overcoat, fought off the hussars with a bayonet. When Petya galloped up, the Frenchman had already fallen. I was late again, Petya flashed in his head, and he galloped to where frequent shots were heard. Shots rang out in the courtyard of the manor house where he was with Dolokhov last night. The French sat down there behind a fence in a dense garden overgrown with bushes and fired at the Cossacks crowded at the gate. Approaching the gate, Petya, in the powder smoke, saw Dolokhov with a pale, greenish face, shouting something to the people. “Take a detour! Wait for the infantry!” - he shouted, while Petya drove up to him.
“Wait?.. Hurray!..” Petya shouted and, without hesitating a single minute, galloped to the place from where the shots were heard and where the powder smoke was thicker. A volley was heard, empty bullets squealed and hit something. The Cossacks and Dolokhov galloped after Petya through the gates of the house. The French, in the swaying thick smoke, some threw down their weapons and ran out of the bushes to meet the Cossacks, others ran downhill to the pond. Petya galloped on his horse along the manor's yard and, instead of holding the reins, strangely and quickly waved both arms and fell further and further out of the saddle to one side. The horse, running into the fire smoldering in the morning light, rested, and Petya fell heavily onto the wet ground. The Cossacks saw how quickly his arms and legs twitched, despite the fact that his head did not move. The bullet pierced his head.
After talking with the senior French officer, who came out to him from behind the house with a scarf on his sword and announced that they were surrendering, Dolokhov got off his horse and approached Petya, who was lying motionless, with his arms outstretched.
“Ready,” he said, frowning, and went through the gate to meet Denisov, who was coming towards him.
- Killed?! - Denisov cried out, seeing from afar the familiar, undoubtedly lifeless position in which Petya’s body lay.
“Ready,” Dolokhov repeated, as if pronouncing this word gave him pleasure, and quickly went to the prisoners, who were surrounded by dismounted Cossacks. - We won’t take it! – he shouted to Denisov.
Denisov did not answer; he rode up to Petya, got off his horse and with trembling hands turned Petya’s already pale face, stained with blood and dirt, towards him.
“I’m used to something sweet. Excellent raisins, take them all,” he remembered. And the Cossacks looked back in surprise at the sounds similar to the barking of a dog, with which Denisov quickly turned away, walked up to the fence and grabbed it.
Among the Russian prisoners recaptured by Denisov and Dolokhov was Pierre Bezukhov.
There was no new order from the French authorities about the party of prisoners in which Pierre was, during his entire movement from Moscow. This party on October 22 was no longer with the same troops and convoys with which it left Moscow. Half of the convoy with breadcrumbs, which followed them during the first marches, was repulsed by the Cossacks, the other half went ahead; there were no more foot cavalrymen who walked in front; they all disappeared. The artillery, which had been visible ahead during the first marches, was now replaced by a huge convoy of Marshal Junot, escorted by the Westphalians. Behind the prisoners was a convoy of cavalry equipment.
From Vyazma, the French troops, previously marching in three columns, now marched in one heap. Those signs of disorder that Pierre noticed at the first stop from Moscow have now reached the last degree.
How to avoid balancing losses? The answer is simple: the aerodynamic configuration of a statically stable aircraft must exclude balancing with negative lift on the horizontal tail. In principle, this can be achieved using the classical scheme, but the simplest solution is to arrange the aircraft according to the “canard” scheme, which provides pitch control without loss of lift for trim (Fig. 3). However, canards are practically not used in transport aviation, and, by the way, quite rightly so. Let's explain why.
As theory and practice show, canard aircraft have one serious drawback - a small range of flight speeds. The canard design is chosen for an aircraft that must have more high speed flight compared to an aircraft configured according to the classical design, provided that the power power plants these planes are equal. This effect is achieved due to the fact that on the canard it is possible to reduce air friction resistance to the limit by reducing the area of the aircraft's washed surface.
On the other hand, during landing the “duck” does not realize the maximum lift coefficient of its wing. This is explained by the fact that, in comparison with the classical aerodynamic design, with the same interfocal distances of the wing and the main body, the relative area of the main part, as well as with equal absolute values of the margins of longitudinal static stability, the “canard” scheme has a smaller balancing arm of the main part. It is this circumstance that does not allow the canard to compete with the classical aerodynamic design in takeoff and landing modes.
This problem can be solved in one way: increase the maximum lift coefficient of the PGO ( ) to values that ensure canard balancing at landing speeds of classic aircraft. Modern aerodynamics has already given “ducks” high-load profiles with values Su max = 2, which made it possible to create a PGO with
. But, despite this, all modern canards have higher landing speeds compared to classic designs.
The disruptive characteristics of the “ducks” also do not stand up to criticism. When landing in conditions of high thermal activity, turbulence or wind shear, the PGO, providing balancing at the maximum permissible Su aircraft, may have . Under these conditions, with a sudden increase in the angle of attack of the aircraft, the PGO will reach supercritical flow, which will lead to a drop in its lift, and the angle of attack of the aircraft will begin to decrease. The resulting deep disruption of the flow from the PGO puts the aircraft into a mode of sharp uncontrolled dive, which in most cases leads to disaster. This behavior of the “ducks” at critical angles of attack does not allow the use of this aerodynamic design in ultra-light and transport aircraft.
I belong to that category of modellers who are interested in designing and building an airplane themselves, and then enjoying flying it. But the main pleasure comes from the result of creative search.
After flying for several seasons on a homemade Diamant with OS MAX 50, it became a little boring. It was clear what the plane could do and what I could do. Of course, I could have honed my 3D aerobatics skills, but my soul was asking for something unusual. I wanted to build an airplane that no one else has, and which would have unique aerobatic capabilities unique to it.
Attempt 1
I watched how radio fighters fly, and the idea came up to build a “flying wing” type fanfly. No sooner said than done. The drawing was drawn, the layout worked out, and now the plane is ready.
- Swing: 1450 mm
- Length: 1000 mm
- Weight: 2000 g
- Engine: OS MAX 50
I drive out onto the field and realize that I haven’t built anything interesting. Yes, it flies, yes, it spins some figures. But nothing interesting, everything is as usual, even a little boring.
Having analyzed the situation, I understand that this was how it should have been... The classic scheme and the “flying wing” scheme have been worked out to the smallest detail, and cannot offer anything new. Creative stagnation has begun...
Being in a crisis, I leaf through old magazines and come across a model of the “Duck” scheme. This is starting to get interesting.
Idea
The weft pattern has one interesting feature. The steering surfaces are located in front of and behind the center of gravity. Accordingly, if you mix the elevator with the ailerons and do it like in line aerobatics, then the turning moment from the elevators will be applied in front and behind the center of gravity. This in turn will allow you to make loops of a very small radius. It was also known from large aviation that this scheme behaves very stably in stall modes. But the pushing propeller located at the rear did not contribute to the performance of 3D aerobatics.
The conclusion suggested itself: the engine should be placed in front, but then problems arose with alignment. Since the main wing is located at the rear (unlike the classical design, where the stabilizer does not bear the weight of the aircraft, in the canard design it creates lift), and the center of gravity is within 10-20% of the MAR, it was not possible to balance this design. Again a dead end... Leafing through further magazines, I find an old issue of "Wings of the Motherland", which talks about aircraft of special designs, and among them is the "Tandem" design. And the most interesting thing is that there are formulas for calculating the position of the center of gravity. I present an excerpt from this article.
Excerpt from an article in the magazine "Wings of the Motherland" for February 1989.
When flying at high angles of attack before stalling, stall should occur first on the front wing. Otherwise, when stalling, the plane will sharply lift its nose and go into a tailspin. This phenomenon is called “pickup” and is considered completely unacceptable. A way to combat “pickup” on canards and tandems was found a long time ago: it is necessary to increase the installation angle of the front wing relative to the rear, and the difference in installation angles should be 2-3 degrees.
A properly designed aircraft automatically lowers its nose, moves to lower angles of attack and picks up speed, thereby realizing the idea of creating a non-stall aircraft. For a “standard duck” (the horizontal tail area is 15-20% of the wing area and the tail shoulder is equal to 2.5-3 MAR), the center of gravity should be located in the range from 10 to 20% of MAR. For a tandem, the centering should be within 15-20% V eq (chord of an equivalent wing), see figure. The equivalent wing chord is defined as follows:
V eq = (S p +S h)/(l p 2 +l h 2) 1/2
In this case, the distance to the nose of the equivalent chord is equal to:
X eq = L/(1+S p /S z *K)-(S p +S z)/(4*(l p 2 +l z 2) 1/2)
Where K is a coefficient that takes into account the difference in wing installation angles, bevels and flow deceleration behind the front wing, equals:
K = (1+0.07*Q)/((0.9+0.2*(H/L))*(1-0.02*(S p /S h)))
In the given formulas:
- S p - area of the front wing.
- S z - area of the rear wing.
- L - tandem aerodynamic arm.
- l p - the span of the front wing.
- l z - the span of the rear wing.
- Q - excess of the installation angle of the front wing over the rear.
- H is the height distance between the axis of the front and rear wings.
Final version
Now the general idea has formed. We put the engine in front, make the wings the same, and move the receiver and battery to the tail of the plane.
The aileron drive on the front and rear wings is separate. A total of 6 steering gears are used.
It was scary to immediately build a plane for the 50th engine. A whole range of questions remained unclear: on which wing to make ailerons, and on which elevator, or both; what angles of attack should the wings have; how far the wings should be spaced apart from each other; and, in general, will it fly?
But the creative itch took over the mind, and all doubts were cast aside. I am building a "Tandem" for the 25th engine. I’ll use it to check how it flies...
Attempt 2
The model is drawn, drawn and built. The following happened.
- Both wingspan: 1000 mm
- Length: 1150 mm
- Wing chord with aileron: 220 mm
- Distance between wings: 200 mm
The front wing was placed 20 mm lower than the engine axis, the rear wing 20 mm higher. The wings were absolutely identical and mutually interchangeable, only on one wing there were ailerons, and on the other an elevator.
Flight
The first flight only added confidence in the correct direction of the search. The model was absolutely predictable and adequate in the air, stable at low speeds and did not spontaneously fall into a tailspin. The scheme with the elevator on the front wing showed better results compared to the scheme when the elevator was on the rear wing. This is due to the fact that at low speeds it acted as flaps, increasing the lift on the front wing.
It's decided! I am studying the behavior of this model in the air and starting to build a model for 61 engines. While the big plane is being built, we fly on the small one. During the flights we find another interesting feature of the model. She could stop and stand in the air against the wind. When pulling the stick toward itself at low throttle, it showed a tendency to parachute.
The result is the following:
- Swing: 1400 mm
- Length: 1570 mm
- Chord with aileron: 300 mm
- Distance between wings: 275 mm
The first flight is carried out with ailerons on the rear wing and elevator at the front.
Impression:
Steady, stable at all speeds, very predictable. However, the flight of the large model revealed one peculiarity. The plane reacts very sensitively to the elevator. That is, I brought it into horizontal flight, trimmed it at medium throttle - it flies smoothly and steadily, but as soon as you touch the altitude control, it abruptly, but at a small angle, changes the direction of flight. It’s not that it’s annoying or dangerous, you just need to take into account that the model reacts very sensitively to the elevator.
This is of course unacceptable for a training aircraft, but our FAN is designed for an advanced pilot.
Now I'm trying to mix the elevator and ailerons. That is, when I pull the handle towards myself on the front wing, both ailerons go down, and on the rear wing they go up. But when I roll, the ailerons work in parallel on both wings.
The model's unstable behavior in horizontal flight was most likely due to incorrect wing angles. Unfortunately, it was not possible to change them without significant alteration.
The model is finally set up, I’m trying out what it can do in the air.
- I'm taking off the gas. I pull the handle towards myself (squeezed expenses). The model slows down almost to a stop, then smoothly nods, accelerates and repeats the same thing. No tendency to spin. That is, if you do not deliberately disrupt the flow from the wing, then the stall occurs very smoothly and is immediately restored with a set of speed.
- I'm taking off the gas. I pull the handle on myself (full expenses). The model stops in the air and, maintaining a horizontal position, begins to descend like a parachute. Parachute figure. I give the handle from myself - she turns over on her back and continues her descent vertically downwards (it’s just some kind of plague). "Shifter" figure. That is, the model is capable of being controlled by rudders in the mode of 100% flow separation from the load-bearing planes!
- Expenses to the maximum - I'm twisting the loop. True, this cannot be called a loop. Rather, it is a classic “waterfall” from a 3D complex. The model spins around the lantern, while slowly descending. Moreover, there is no need to work with gas. And it is very easy to change the direction of rotation when shifting the rudders. Shaker figure.
- I make a “parachute” and deflect the rudder. I get a very slow flat corkscrew - a "dry leaf" figure.
- Such a figure as the “harier” goes into the category of children’s.
- A “square loop” turns out to be exactly square, since the turning radii at the corners are almost unreadable.
It would take a very long time to describe the figures. I'll just say one thing. This plane can do more than I can, and is capable of teaching an advanced pilot several more new maneuvers that are inaccessible on conventional aircraft. And I especially want to note the predictability and stability of the aircraft, no matter what you do with it.
Looks like I got what I WANTED!
Attempt 4
Although the second and third planes showed excellent flight performance, there was one more very important question: What are the optimal angles of attack for wings? To solve this problem, it was decided to build a model for the 50th engine, with the ability to change the angle of attack of the wings on the ground. In addition, model No. 3 was destroyed due to hardware failure.
It was also decided to place the front wing above the engine axis, and the rear below (on the previous model it was the other way around, I just wanted to check - I’ll say right away that I didn’t notice any changes in the behavior of the model.) and make a slight bevel along the leading edge, the front wing received an implicit the pronounced positive "V" and the posterior negative "V". This was supposed to give stability at low speeds in forward and reverse aerobatics, respectively.
I will not dwell in detail on the description of the design and manufacturing process. She is no different from the usual Fanfly and is clear from the photographs.
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AIRCRAFT "DUCK" PATTERN
Since the first heavier-than-air aircraft to take off, the Wright brothers' Flyer (1903), was built according to a design that is today known as a "duck," it seems logical to begin the story about aircraft of unconventional designs with aircraft of this class.
MISTAKEN TERM
First of all, the term "duck" is a misnomer. In aviation, a “duck” is generally understood to mean an aircraft whose horizontal tail—the stabilizer and elevators—are located in front of the wing and not behind it. This term can be applied with equal success to airships and gliders. In particular, the first models of Zeppelin rigid airships were equipped with forward horizontal control surfaces in addition to the traditional tail ones.
Typically, the term "canard" refers to the location at the front of the aircraft of the main, rather than auxiliary, aerodynamic control means.
This term first appeared in France; its origin is probably due to the fact that the wing of a flying duck is closer to its tail than to its head, and not at all because this bird controls its flight with the help of a special organ located in front of the wing. Aircrafts This scheme has become quite widespread.
Many canard aircraft can be thought of as tandem wing aircraft, with the front wing being relatively small. In this case, the front horizontal tail (FH), usually consisting of fixed (stabilizers) and moving (elevators) surfaces, bears a significant part of the aerodynamic load.
In recent years, the term "canard" has come to be used to describe aircraft equipped with auxiliary aerodynamic control surfaces mounted on the nose of, generally speaking, fairly conventional aircraft (as well as some delta-wing aircraft), to provide trim or flow control to the aircraft. flow, and not to exercise basic control or create part of the total lifting force, as is the case on a classic “duck”.
WHY FRONT HORIZONTAL TERMINATION?
Before the Wright brothers actually began building the airplane, they
Firstly, the Wright brothers perfectly understood the functions of the “horizontal rudder” in controlling the position of the aircraft in space and believed that the front empennage would perform such functions more effectively than the tail one. In this they turned out to be right, but, of course, they did not know the shortcomings of such a technical solution.
The second main reason for their choice was the location of the first flights, which were carried out from a sandy site, and therefore there was no possibility of using a wheeled landing gear. Both the previously created gliders and the first Flyer were equipped with a skid landing gear, in which the fuselage of the aircraft was located very close to the ground. At the same time, the Wright brothers understood the need for a high angle of attack during takeoff and landing. A low-slung vehicle like the Flyer would certainly have had its tail surface hooked to the ground if it had been chosen; therefore, the designers abandoned this solution. They installed a vertical fin at the tail of their aircraft. The beams supporting the keel were equipped with hinges and, with the help of cable wiring, could be deflected upward without affecting the controllability of the aircraft, since the keel did not deflect relative to the oncoming flow.
ADVANTAGES
In the modern understanding, the main advantage of the canard aerodynamic design is considered to be increased maneuverability of the aircraft, which attracts creators of military equipment to this design. The higher maneuverability of aircraft of this design turned out to be very useful in improving the characteristics of some of those created in Lately ultralight aircraft.
Another advantage of aircraft with a canard design is that it is almost always possible to build such an aircraft with natural anti-spin protection: the stall of the air flow on the PGO occurs earlier than on the wing, which creates most of the lift, so the nose of the aircraft in this case is slightly lowers and the machine returns to normal flight.
FLAWS
A significant disadvantage of the canard design is that aircraft of this design are characterized by longitudinal instability. Instead of damping the aircraft's movements relative to the transverse axis (pitch), as, for example, the fin of an arrow does, the effect of air flow on the front horizontal tail increases the corresponding disturbances.
In his notes, O. Wright noted that the pitch stability of the "duck" is determined by the skill of the pilot. The experience of the first flights showed that in the case when a significant lifting force is created on the front horizontal tail, it has a significant impact on the balancing of the aircraft.
A flow disruption at the PGO causes approximately the same effect on the balancing of the aircraft as, for example, folding a pair of table legs; the other two legs continue to support the opposite end, and the table falls in the direction where there is no support.
Therefore, the anti-spin advantages of canard aircraft quickly faded.
Aircraft of this design almost completely disappeared from aircraft manufacturing practice until, at the beginning of the Second World War, in-depth studies of the “duck” began to be carried out, aimed at finding possible ways improving aircraft maneuverability characteristics.
However, even during this period of aviation development, it was not possible to realize the advantages of this scheme. Only in recent years have several very successful canard aircraft been created, which have demonstrated the advantages of this design in some specific application conditions aviation technology.
However, these aircraft have already used special means to prevent a powerful flow stall from the PGO. This is achieved by increasing the critical angle of attack by blowing the flow onto the PGO, using aerodynamic profiles with different load-bearing properties, or using the PGO as only a balancing surface (in this case, the PGO does not create any noticeable contribution to the lift force), for example, on airplanes with a large area close to a delta wing or “tailless” airplanes with a forward-swept wing.
Some modern rockets are built using the canard design, but the control systems of these rockets usually operate using on-board computers and automatic stability enhancements that generate and implement balancing commands that prevent the build-up of disturbances in the pitch channel.
It should be noted that all canard aircraft, implemented in accordance with the technical level achieved before the 1960s, were a complete disaster. As if anticipating this, the Wright brothers already in 1909 (when they began to use a wheeled landing gear, which made it possible to lift the aircraft from the ground and ensure a set angle of attack at acceleration) abandoned the PGO and installed elevators in the tail of the device near the rudder.
The "duck" design is most widely used in the field of ultra-light aircraft. This class of modern aircraft has made its way back to the type of flight performed by the Wright brothers, which is characterized by a very limited speed range, limited maneuverability and a relatively small payload.
More aircraft of this design were probably designed and built between 1980 and 1983 than in all previous aviation history.
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