What is the fuselage of an airplane? Scheme, device, structural elements

The fuselage of a passenger aircraft connects wings, tail surfaces and in some cases the chassis. It is intended for the accommodation of equipment, crew, cargo. A plane without a fuselage is called a flying wing. In its thickened compartment there is everything that is in the case of the usual apparatus. Let us consider in detail what the fuselage of an airplane is. A photo of this component will also be presented in the article.

General requirements

Explaining in two words what is the fuselage of an airplane, we can say that this is the body of the device. This component of the aircraft is subject to a number of requirements:

1. Rational use of all internal volumes.
2. Minimum drag.
3. Provide sufficient visibility from the cockpit and crew accommodation.
4. Reliable heat and sound insulation and tightness.
5. Easy unloading / loading.
6. Required ventilation, lighting and heating.

External shape

The geometry of the aircraft fuselage is represented by an axisymmetric body with a smooth narrowing to the tail and nose parts. With this form, a minimum surface area is provided for a given size. Accordingly, the weight of the skin decreases, the resistance decreases. Light weight gives certain advantages when exposed to excessive pressure in airtight cabins. However, for a number of reasons, such an ideal form is not observed. The smoothness of the contours is broken, in particular, by elements of the fuselage of the aircraft, such as cab lights, radar antennas. This, in turn, leads to increased resistance and increased mass. The same effect takes place when deviating from the smooth forms in the tail sections. In this case, an increase in the tilting angle or a shortening of the ramp and cargo hatch is provided.

Loads

Explaining what a fuselage aircraft (photo, presented in the article, illustrates its features), it is necessary to say about the effects that it experiences. When boarding and in flight, this component is operated by:

1. Forces transmitted from attached components. Among them, in particular, include wings, chassis, tail, power plant, etc.
2. Mass inertial impact of equipment, cargo, aggregates, which are directly in it.
3. Aerodynamic forces that are distributed over the surface.
4. Inertial effect of own mass. It has the very design of the fuselage of the aircraft.
5. Forces of excessive pressure in the equipment compartments, airtight cabins.

All these loads are fully balanced. Considering what the fuselage of an airplane is in the framework of structural mechanics, you can imagine it as a box-shaped beam. In any section, it is affected by horizontal and vertical forces, torque. In sealed compartments, excessive internal pressure is added to them.

Rationality of the module

The most optimal is the fuselage scheme of the aircraft, in which he can perceive all the above loads with a small enough weight. Thin-walled shell in this case is fixed on the power frame. Rationality is ensured by the full use of the skin. In the place where the fuselage is located near the aircraft, there are local aerodynamic forces, internal overpressure, general power work. Thin-walled shell, reinforced from the inside by a frame, maximally satisfies the requirements of the convenience of layout, provides technological simplicity, performance characteristics. Such a device of the aircraft fuselage is called a girder. Previously used truss modules. They significantly lost the beam by their weight. What is the fuselage of a farm type aircraft? The sheathing in this case is completely excluded from the power work. It perceives only local aerodynamic loads. If we talk about what a fuselage plane is in this case, then it can be defined as an additional module that increases the total mass of the device. The spatial truss significantly complicates the layout of the cargo. The drawbacks of such a module have led to the fact that in modern aircraft construction they are practically not used. Their use is advisable only on slow-moving light vehicles of small aircraft.

Classification

There are three types of aircraft fuselages:

1. Cladding.
2. Lateral.
3. Stringer.

The last two differ from each other in shape and area in cross section. Longitudinal set in the place where the fuselage is located near the aircraft consists of stringers and spars. The sheath module in cross section includes frames. They ensure the preservation of a given shape under shell deformations and the transfer of concentrated and distributed loads. In a place where the aircraft fuselage, there are areas in which there can be a greater concentration of forces. To prevent deformation in these cases, reinforced frames are installed. In beam modules, the effect of any direction is perceived to be completely skinned. A tangential flow of forces arises in it. Their distribution depends on the direction of the external action and the shape of the cross section of the module. The lining also fully takes in the torque. In this case, the tangential flow is evenly distributed around the perimeter. The shell, as a rule, has a single-ended contour in the cross section. On the areas where there are cutouts in the shell, install force edging. They ensure the transfer of all efforts in these areas.

Stringers and spars

Longitudinal parts of the fuselage of the aircraft pass usually along its entire length. Together with the plating they take normal bending effort. The manufacture of simple stringers and spars is carried out, as a rule, from bent or extruded profiles with a different cross-section. Longitudinal elements have great rigidity. For heavy loads, in some cases, multiple spars can be installed. They include several profiles connected to each other. When edging large-sized cuts, beams are used - longitudinal elements of box section. They are made of extruded profiles, which are joined together by skin and walls.

Frames

They can be reinforced or conventional. The latter ensure the safety of the cross-sectional shape of the module. The reinforced frames are used in areas of accumulation of large loads on the body. On them there are knots, joining units, fastening loads, large equipment, engines, etc. Strengthening is also established along the boundaries of large cutouts in the hull. Typical frames have, as a rule, a frame structure. They are made of a stamped or flexible sheet. The reinforced elements are made in the form of a closed frame of the channel or I-section. The tangential flow acts as a supporting reaction. The frame distributes the external impact along the entire perimeter. It itself acts on the bend. It defines its section. The construction of such a frame is monolithic or prefabricated. At the installation sites of the partitions, the reinforced frame is sewn completely with the wall. It is supported by horizontal and vertical profiles. The frame can also be provided with a spherical shell. The reinforcing elements are thus arranged radially.

Sheathing

It is made of metal sheets. They are formed along the profile of the surface of the shell and fixed. The joints of the sheets are arranged along the transverse and longitudinal parts of the module. Monolithic ribbed panels are used for casing frames. Recently, the use of composite materials is quite common.

Connecting components

Sheathing can be fastened to frames or stringers, or both at the same time. The first option is used in the skin modules. When fastening only to stringer, riveted longitudinal seams are used. In this case there is no transverse connection. This improves the aerodynamic properties of the module. But in this case, with less load, the sheath loses its stability. This leads to an increase in the weight of the structure. To prevent this, the sheath is often connected to the frame by a compensator - an additional pad.

Joints

With a beam-and-spar fuselage scheme, they are performed with the help of assemblies that are located exclusively on the longitudinal parts. Such joints are called point junctions. Contour connections are used in the beam-stringer fuselage. Joints are placed along the entire perimeter of the frame with the obligatory reinforced binding of the skin and stringer. Connections in such fuselages, as a rule, are carried out with the help of flanges. Such a joint provides a force connection with the parts contiguous to the contour.

Fastening of units

The connection nodes are installed on reinforced frames. They perform the function of the hard disk. Due to them, the distribution of concentrated longitudinal loads is realized. Butt joints should be connected with power spars. To reduce the weight of the entire structure of the fuselage, it is advisable to reduce the number of reinforced frames. Each of these elements can accommodate several assembly units.

Wings

As a specific feature of fastening these parts, balancing of the bending moments in this joint of the wing consoles serves. Rational will be considered the balancing of the right and left elements on the center wing, passing through the fuselage. For the spar type of the module, it is sufficient to skip the longitudinal elements - they will be used to balance the fold. To connect monoblock and caisson wings through the body, all power panels must pass. If, for some reason, the passage of elements through the fuselage can not be carried out, the bending moments on the right and left must be closed on the power frames. Such a solution, however, can be used for spar wings, since the number of parts in them is small. Monoblock and caisson components will require more reinforced frames. This is quite difficult to perform on the design. In such cases it is advisable to use the spar.

Keel

Its attachment requires the obligatory transfer of the bending moment to the fuselage. To do this, each longitudinal element of the keel is connected to the reinforced frame. If possible, you can use the mast type of the spar insert in two points. They have the height of the frame. The arrow-shaped longitudinal element has a fracture in the section of intersection with it. This requires mandatory installation of additional amplification. It can be discarded if the frame is positioned obliquely relative to the fuselage axis, so that the plane becomes an extension of the side member wall. But the embodiment of this option will be accompanied by certain difficulties.

Cutouts

The central part of the fuselage of the aircraft includes holes for windows, doors, hatches, lights, chassis niches. All these cutouts violate the closed contour of the skin. Accordingly, the stability and strength of the carcass significantly decrease. To compensate for losses on the contours of the holes, a rigid frame rim is passed through. With small cutouts, it is a monolithic design. It is carried out from a sheet made by stamping or otherwise. Large holes are edged along the ends of reinforced frames. In the longitudinal direction, beams are installed. In this case, they do not end within the cut-out, but go beyond the reinforced frames. This ensures a rigid laying of longitudinal parts. Chassis niches are fixed on reinforced frames and spars in the lower part of the hull.

Sealed cabin

When flying at high altitude, excessive pressure is maintained in them. To ensure a minimum mass of sealed cabins they are made in the form of a sphere or cylinder with spherical bottoms. It is necessary to strengthen the frame, located at the junction of the segments. This is required because it takes a rather large compressive load. In hermetically sealed cabins, sheathing under excessive pressure does not undergo bending deformations. It works exclusively on stretching. In some cases, this form has to be retreated. This, in turn, leads to an increase in the weight of the entire structure. To ensure the necessary rigidity for bending, flat panels are used. Being under the influence of excessive pressure, they are supported by transverse and longitudinal beams (ribs). To strengthen the rigidity of the panels are made in the form of three-layer structures. The cabins should be provided with a reliable seal on all bolt and riveted seams. For this purpose, special tapes are used. They are impregnated with a sealant, they are blotted with a non-drying mastic, covered with special compounds, followed by drying. On the joints of the sheathing sheets, riveted multi-row seams with a small step are used. Particularly carefully treated with hermetic hatches, windows, lights, doors. Sealing is ensured by the use of special sealing means. It can be rubber bands, tapes, inflatable tubes, gaskets.

Required Activities

To ensure compliance with the requirements that are imposed on the fuselage of the aircraft, certain actions must be performed. They include:

1. The choice of such values of parameters and external forms of the housing, in which the drag is reduced to a minimum, and the useful volume, respectively, will be optimal.
2. Use of bearing fuselages. Due to them a considerable lift is created . Due to this, it is possible to reduce the mass and the wing area.
3. Rational use of useful volumes. This is achieved by increasing the density of the layout, compact placement of cargo in the center of mass. In this case, the mass moments of inertia will decrease and the maneuverability characteristics will improve. The narrowing of the range of the centering changes with fuel burn-up, different loading options provides greater stability and better controllability.
4. Harmonization of the power circuits of the fuselage and the units attached to it. At the same time, reliable fastening, balancing and transfer of loads from the power parts of the wing, chassis, feathers, installations to the hull must be ensured.
5. Ensuring the convenience of the entry / exit crew, passengers, mooring, loading / unloading items, equipment, things intended for transportation.
6. Providing a convenient approach to different units. This is mainly necessary for inspection and repair.

For the crew and passengers, the necessary conditions must be created, as well as an appropriate level of comfort during the flight at high altitudes. A mandatory requirement is to provide sound and heat insulation of cabins, the possibility of safe and rapid emergency exit from the cabin. For the crew should also be created comfortable conditions. In particular, pilots should be provided with a good overview, convenience in flight and aircraft management.