Even a person who had never seen the sea, surely knows parting words: “safe ride". And the issues does not occur here. The keel of the ship – the most important structural part, on which are mounted many of the parts of his body. But does anybody know about where it is located and what is the keel of the aircraft?
This is the "on" resistance, which allows to maintain the aircraft desired course. In contrast to ships, the keel of the aircraft is an integral part of the vertical stabilizer of the tail. At the bottom of the fuselage keel have no flying machines, no! But there is one subtlety. The fact that this part is tightly connected with the power elements of the fuselage, and therefore something in common sea and air term. So where is the keel of the plane? Simply put, it is the vertical part of the tail.
It Is motionless, fixed in three points symmetric to the centerline of the aircraft. To view this part has the shape of a perfect trapezoid. Typically, the keel of the aircraft consists of spars, ribs and skin. This scheme is classic, have changed little since the introduction of the first aircraft. The front spar is inclined (as a rule).
Most Often, the keel is single, but in some cases doing double and even triple (for propeller driven bombers). In the latter case, it is required to ensure a high directional stability of heavy vehicles. By the way, all the planes at the location of the keel are divided into three types:
Of Course, the last two varieties more characteristic of “community” of military aircraft, such as the placement of the keel is necessary to make an aircraft very high maneuverability.
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In some cases use even more complex designs. For example, podkrovie ridges (they are the same – ventral keels). They are used on some supersonic aircraft, where maintaining perfect stability during the flight is vital. Thus, under the keel of the aircraft (this is where we have already found out) there is an additional and a massive influx. More common situation is when the horizontal tail the tail does have to move to the top of the keel. This happens if the engines are mounted aft of the aircraft. Such a scheme, for example, can be seen on domestic passenger aircraft "Il".
As you know, windless weather – an incredibly rare that it happens no more a couple times a year. In most cases, if there is wind, and its strength and direction can be vastly different. When the plane is flying, the wind can strongly influence the direction and course. The aircraft should be designed so that their own to return to a stable position. Only in this case it is possible to safe flight.
The cardinal rule of construction of the keel – place it so that it is under no circumstances not got in the slipstream of the wing. Otherwise, severe disturbance of exchange rate stability, and in the most extreme situations – a physical deformity and destruction of the entire tail. So, the main purpose of the keel – keeping directional stability.
The Design of many aircraft is such that the detail of this – agile. By adjusting the amount of deflection of the keel, the crew controls the course direction. The exception – military aircraft, which for changing the direction of flight answer engines with controlled thrust vector. In their case, to make a movable keel of the aircraft (photo it is in the article) is silly, since overload when maneuvering such that he will simply collapse.
There are three types of stability, for the sake of which the aircraft design includes a keel:
Let's Deal with all these kinds in detail. So directional stability. It should be remembered that in case of loss of longitudinal stability of the fuselage in flight, the plane will still continue for some time to fly forward due to inertia forces. Then the air flow starts coming up on the rear part of the aircraft, which lies behind the center of gravity. The keel in this case prevents the rotating effort, forcing the plane to rotate around its axis.
Longitudinal stability. Suppose the plane is flying in normal mode, the center of gravity coincides with the center of application of pressure to its fuselage. At this moment on the fuselage are also opposing forces that seek to deploy airframe. Lift and gravity act at the same time. The keel of the aircraft (photo this part you will see in the article) provides equilibrium, which in this case is very fragile. Normal flight without the tail, keel and stabilizers impossible.
Lateral stability. In General, this factor is a logical continuation of the previous properties. When on the wing and the lateral stabilizers of the keel are opposing forces, they are “trying” tilting the plane. Counteracts the shape of the wings: if you look at them from afar, they resemble the letter “U”, with very diluted top “horns”. This shape provides a self-correction of the position of the aircraft in space. The keel helps to preserve lateral stability.
Note that aircraft with forward-swept wings need in Kiel is not as big… at high speeds. If it crashes, then increase counter forces occurs exponentially. And because these machines are very important the most durable and lightweight keel which can resist such high loads. And how is it? We'll tell about it.
At present the specialists of the Federal air transport Agency and their foreign counterparts focus on the creation of aircraft parts (including keel) of large parts made of modern composite materials.
The Proportion of these compounds in the design of modern aircrafts is steadily growing. According to information from the experts, their volume fraction reaches 25% to 50%, and small non-commercial planes can and do consist of plastic and composites at 75%. Why this approach is so widely spread in aviation? The fact that the keel of the aircraft «Boeing», made from a polymer called "alloys", has a very low weight, very high strength and a resource, which, using standard materials, to achieve just unreal.
The Most justified the use of composites in design is not only the tail but also wings and the power elements of the fuselage, which needs to be not only very strong but also quite flexible. Otherwise there is a possibility of structural collapse under the influence of flight loads.
But it was not always so. So, the pride of the Soviet aircraft industry, the aircraft «Tu-160" aka "White Swan” or “black Jack”, has a keel of… titanium alloys. Such a specific and extremely expensive material was chosen because of the huge loads on the design of this machine, which to this day retains the title of heavy bombers, standing on the arms. But such a radical approach to the creation of the keel – rare, but because today, designers more often have to deal with simple and composite materials.
In the process of developing domestic designers had to solve a range of complex tasks:
In the production process was introduced the latest software (FiberSim), which allows to achieve the highest possible degree of automation. Also, now the keel of the aircraft, the design of which is described in the article can be manufactured on such technologies, where virtually no drawings. Manufacture this parts with this approach are as follows:
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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."
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