Aircraft upholstery. Cutting, stitching, stretching and fastening fabric sheathing of aircraft and glider elements

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airplane- an aircraft heavier than air with a wing on which aerodynamic lift is generated during movement, and a power plant that creates thrust for flight in the atmosphere. The main parts of the aircraft: wing (one or two), fuselage, plumage, landing gear ... Encyclopedia of technology

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sheathing Encyclopedia "Aviation"

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sheathing- And; pl. genus. wok, dat. vkam; and. 1. to sheathe. 2. What is sheathed, trimmed around the edges or something; border, rim. Sleeves with red lining. Coat with fur lining. Atlas Island hem. 3. What is covered, upholstered, sheathed on the surface of something. (boards, ... ... encyclopedic Dictionary

An airplane is an aircraft, without which it is impossible to imagine the movement of people and goods over long distances today. The development of the design of a modern aircraft, as well as the creation of its individual elements, is an important and responsible task. Only highly qualified engineers, specialized specialists are allowed to this work, since a small error in calculations or a manufacturing defect will lead to fatal consequences for pilots and passengers. It is no secret that any aircraft has a fuselage, carrying wings, a power unit, a multidirectional control system and take-off and landing devices.

The following information about the features of the design of aircraft components will be of interest to adults and children involved in the design development of aircraft models, as well as individual elements.

aircraft fuselage

The main part of the aircraft is the fuselage. The remaining structural elements are fixed on it: wings, tail with plumage, landing gear, and inside the control cabin, technical communications, passengers, cargo and aircraft crew are located. The body of the aircraft is assembled from longitudinal and transverse power elements, followed by metal sheathing (in light versions - plywood or plastic).

When designing an aircraft fuselage, requirements are imposed on the weight of the structure and maximum strength characteristics. This can be achieved using the following principles:

The body of the aircraft fuselage is made in a form that reduces drag on air masses and contributes to the emergence of lift. The volume, dimensions of the aircraft must be proportionally weighed;
When designing, they provide for the most dense layout of the skin and power elements of the hull to increase the usable volume of the fuselage;
They focus on the simplicity and reliability of fastening wing segments, takeoff and landing equipment, power plant;
Places for securing cargo, accommodating passengers, consumables must ensure reliable fastening and balance of the aircraft under various operating conditions;

The location of the crew should provide conditions for comfortable control of the aircraft, access to the main navigation and control devices in emergency situations;
During the maintenance of the aircraft, it is possible to freely carry out diagnostics and repair of failed components and assemblies.

The strength of the aircraft body must provide resistance to loads under various flight conditions, including:

loads at the attachment points of the main elements (wings, tail, landing gear) during takeoff and landing;
during the flight period, withstand the aerodynamic load, taking into account the inertial forces of the weight of the aircraft, the operation of the units, the functioning of the equipment;
pressure drops in hermetically limited sections of the aircraft, which constantly occur during flight overloads.

The main types of aircraft body construction include flat, one- and two-story, wide and narrow fuselages. Beam-type fuselages have proven themselves and are used, including layout options that are called:

Sheathing - the design excludes longitudinally located segments, reinforcement occurs due to frames;
Spar - the element has significant dimensions, and the direct load falls on it;
Stringer - have an original shape, area and cross section is less than in the spar version.

Important! The uniform distribution of the load on all parts of the aircraft is carried out due to the internal frame of the fuselage, which is represented by the connection of various power elements along the entire length of the structure.

Wing structure

The wing is one of the main structural elements of the aircraft, which provides the creation of lift for flight and maneuvering in air masses. Wings are used to accommodate take-off and landing devices, power unit, fuel and attachments. The operational and flight characteristics of the aircraft depend on the correct combination of weight, strength, structural rigidity, aerodynamics, and workmanship.

The main parts of the wing is called the following list of elements:

Hull formed from spars, stringers, ribs, skin;
Slats and flaps for smooth takeoff and landing;
Spoilers and ailerons - through them, the aircraft is controlled in the airspace;
Brake flaps designed to reduce the speed of movement during landing;
Pylons necessary for mounting power units.

The structural power scheme of the wing (the presence and location of parts under load) must provide a stable resistance to the forces of torsion, shear and bending of the product. It includes longitudinal, transverse elements, as well as external skin.

The transverse elements include ribs;
The longitudinal element is represented by spars, which can be in the form of a monolithic beam and represent a truss. They are located throughout the volume of the inner part of the wing. Participate in stiffening the structure, when exposed to bending and transverse forces at all stages of flight;
Stringer is also referred to as longitudinal elements. Its placement is along the wing along the entire span. Works as an axial stress compensator for wing bending loads;
Ribs - an element of transverse placement. The design is represented by trusses and thin beams. Gives a profile to the wing. Provides surface rigidity when distributing a uniform load during the creation of a flight air cushion, as well as fastening the power unit;
The skin gives shape to the wing, providing maximum aerodynamic lift. Together with other structural elements, it increases the rigidity of the wing and compensates for the effect of external loads.

The classification of aircraft wings is carried out depending on the design features and the degree of work of the outer skin, including:

Spar type. They are characterized by a slight thickness of the skin, forming a closed contour with the surface of the spars.
Monoblock type. The main external load is distributed over the surface of the thick skin, fixed by a massive set of stringers. Sheathing can be monolithic or consist of several layers.

Important! Docking parts of the wings, their subsequent fastening must ensure the transmission, distribution of bending and torque that occur during various operating modes.

Aircraft engines

Thanks to the constant improvement of aircraft power units, the development of modern aircraft construction continues. The first flights could not be long and were carried out exclusively with one pilot, precisely because there were no powerful engines capable of developing the necessary traction force. Over the entire past period, aviation has used the following types of aircraft engines:

Steam. The principle of operation was to convert the energy of steam into translational motion transmitted to the propeller of the aircraft. Due to the low efficiency, it was used for a short time on the first aircraft models;
Piston - standard engines with internal combustion of fuel and torque transmission to the propellers. The availability of manufacturing from modern materials allows their use to date on individual aircraft models. Efficiency is presented no more than 55.0%, but high reliability and unpretentiousness in maintenance make the engine attractive;

Reactive. The principle of operation is based on the conversion of the energy of intensive combustion of aviation fuel into thrust necessary for flight. Today, this type of engine is most in demand in the aircraft industry;
Gas turbine. They work on the principle of boundary heating and compression of the fuel combustion gas, directed to the rotation of the turbine unit. They are widely used in military aviation. Used in aircraft such as Su-27, MiG-29, F-22, F-35;
Turboprop. One of the variants of gas turbine engines. But the energy received during operation is converted into drive for the propeller of the aircraft. A small part of it is used to form a jet pusher jet. They are mainly used in civil aviation;
Turbofan. Characterized by high efficiency. The applied technology of injection of additional air for complete combustion of fuel ensures maximum efficiency and high environmental safety. Such engines have found their application in the creation of large airliners.

Important! The list of engines developed by aircraft designers is not limited to the above list. At different times, attempts were repeatedly made to create various variations of power units. In the last century, work was even carried out on the design of atomic engines in the interests of aviation. Prototypes were tested in the USSR (TU-95, AN-22) and the USA (Convair NB-36H), but were withdrawn from testing due to the high environmental hazard during aviation accidents.

Controls and signaling

The complex of on-board equipment, command and executive devices of the aircraft are called controls. Commands are given from the pilot cabin, and are carried out by elements of the wing plane, tail plumage. Different types of aircraft use different types of control systems: manual, semi-automatic and fully automated.

Controls, regardless of the type of control system, are divided as follows:

The main control, which includes actions responsible for adjusting flight modes, restoring the longitudinal balance of the aircraft in predetermined parameters, these include:

levers directly controlled by the pilot (steering wheel, elevators, horizon, command panels);
communications for connecting control levers with elements of actuators;
direct executing devices (ailerons, stabilizers, spoler systems, flaps, slats).

Additional control used during takeoff or landing.

When using manual or semi-automatic control of the aircraft, the pilot can be considered an integral part of the system. Only he can collect and analyze information about the position of the aircraft, load indicators, compliance of the flight direction with planned data, and make a decision appropriate to the situation.

To obtain objective information about the flight situation, the state of the aircraft components, the pilot uses groups of instruments, let's name the main ones:

Aerobatic and used for navigational purposes. Determine the coordinates, horizontal and vertical position, speed, linear deviations. They control the angle of attack in relation to the oncoming air flow, the operation of gyroscopic devices and many equally important flight parameters. On modern aircraft models, they are combined into a single flight and navigation complex;
To control the operation of the power unit. Provide the pilot with information about the temperature and pressure of oil and aviation fuel, the flow rate of the working mixture, the number of revolutions of the crankshafts, the vibration indicator (tachometers, sensors, thermometers, etc.);
To monitor the operation of additional equipment and aircraft systems. They include a complex of measuring instruments, the elements of which are located in almost all structural parts of the aircraft (pressure gauges, air consumption indicator, pressure drop in hermetically closed cabins, flap positions, stabilizing devices, etc.);
To assess the state of the surrounding atmosphere. The main measured parameters are the outdoor air temperature, the state of atmospheric pressure, humidity, and the speed indicators of the movement of air masses. Special barometers and other adapted measuring instruments are used.

Important! The measuring instruments used to monitor the state of the machine and the environment are specially designed and adapted for difficult operating conditions.

Takeoff and landing systems 2280

Takeoff and landing are considered critical periods in the operation of the aircraft. During this period, there are maximum loads on the entire structure. Only a well-designed landing gear can guarantee an acceptable take-off acceleration and a soft touch on the runway surface. In flight, they serve as an additional element to stiffen the wings.

The design of the most common chassis models is represented by the following elements:

folding strut, compensating lot loads;
shock absorber (group), ensures the smoothness of the aircraft when moving along the runway, compensates for shocks during contact with the ground, can be installed in a set with stabilizer dampers;
braces that act as a structural stiffener, can be called rods, are located diagonally with respect to the rack;
traverses attached to the fuselage structure and landing gear wings;
orientation mechanism - to control the direction of movement on the lane;
locking systems that secure the rack in the required position;
cylinders designed to extend and retract the landing gear.

How many wheels are on an airplane? The number of wheels is determined depending on the model, weight and purpose of the aircraft. The most common is the placement of two main racks with two wheels. Heavier models - three rack (placed under the nose and wings), four rack - two main and two additional support.

Video

The described device of the aircraft gives only a general idea of the main structural components, allows you to determine the degree of importance of each element in the operation of the aircraft. Further study requires deep engineering training, special knowledge of aerodynamics, strength of materials, hydraulics and electrical equipment. At aircraft manufacturing enterprises, these issues are dealt with by people who have undergone training and special training. You can independently study all the stages of creating an aircraft, only for this you should be patient and be ready to gain new knowledge.

Aircraft fuselage design has evolved from early wood truss structures through the monocoque shell to the modern semi-monocoque shell.

farm structure. The main disadvantage of the truss structure is the lack of a streamlined shape. The design is based on pipe segments called spars. Welded together, they form a well-reinforced frame. Vertical and horizontal brackets are welded to the spars, due to which such a structure acquires a square or rectangular section. Additional brackets are added to the structure to provide resistance to external pressure that can occur from either side of the structure. Stringers and frames (or accessory ribs) create the shape of the fuselage and support the skin.

As technology progressed, designers began to cover the trusses to give the fuselage a more streamlined shape and improve its aerodynamic performance. This was originally done with cloth. Subsequently, light metals (aluminum) began to be used. In some cases, the outer skin can carry all or a significant part of the flight load. Most modern aircraft use a load-bearing skin structure known as a monocoque or semi-monocoque (Figure 2-14).

Monocoque. The monocoque design uses a load-bearing skin, which, like the wall of an aluminum can, takes almost all the load. Being sufficiently rigid, such a design does not respond very well to the deformation of its surface. For example, an aluminum can can withstand a significant load if this load falls on the edges. But if the side surface of the can is even slightly deformed, even slight pressure can crush the can.

Since most of the bending load is on the skin and not on the exposed truss frame, there is no need to reinforce the structure internally. This reduces its weight and increases interior space. One of the original methods of using a monocoque was first proposed by American engineer Jack Northrop. In 1918, he developed a new method for manufacturing a monocoque fuselage, which was later applied to the creation of the Lockheed S-1 Racer aircraft. The design consisted of two plywood halves of the shell, which were glued to wooden hoops-stringers. In order to get the halves, the designer used three large pieces of spruce plywood, which were soaked in glue and placed in a semi-circular concrete mold resembling a bathtub. Then the form was covered with a tight-fitting lid, and a rubber ball was inflated inside it, which pressed the plywood against the surface of the form. A day later, a smooth and even half of the shell was ready. Both halves had a thickness of no more than 6 millimeters.

Due to the difficulties in industrial production, the monocoque did not become widespread until a few decades later. Today, monocoque construction is widely used in the automotive industry, where the monocoque body is the de facto industry standard.

Semi-monocoque. The semi-monocoque design (partial or half) uses an additional structure to which the aircraft skin is attached. Consisting of frames and/or ribs of various sizes, as well as stringers, this structure reinforces the load-bearing skin, partially removing the bending load from the fuselage. On the main section of the fuselage there are also places for fastening the wings and a heat-shielding casing.

On single-engine aircraft, the engine is usually mounted at the front of the fuselage. A fireproof partition is installed between the rear wall of the engine and the cockpit, which serves to protect the pilot and passengers in the event of a sudden fire in the engine. It is usually made of heat-resistant material (eg stainless steel). Recently, however, composite materials have been increasingly used in aircraft construction. Some aircraft are completely made from them.

Composite construction. Story. The use of composite materials in aircraft construction began during World War II. It was then that fiberglass began to be used in the production of the fuselages of the B-29 strategic bombers. In the late 50s, this material began to be widely used in the manufacture of gliders. In 1965, the first aircraft made entirely of fiberglass was certified. It was a Swiss-made Diamond HBV glider. Four years later, the all-fiberglass, four-seat, single-engine Windaker Eagle aircraft was certified in the United States. Currently, more than a third of all aircraft in the world are made from composite materials.

Composite material is a broad concept. These materials include fiberglass, carbon fiber, bulletproof fiber "Kevlar", as well as their combinations. Composite construction has two important advantages: an extremely smooth surface and the ability to fabricate complex curved or streamlined structures (Figure 2-15).

Airplanes made of composite materials. Composite material is an artificially created heterogeneous material consisting of a filler and reinforcing elements (fibers). The filler acts as a kind of “glue”, fastening the fibers and (during vulcanization) giving the product a shape, and the fibers take on the bulk of the load.

There are many different types of fibers and fillers. In the manufacture of aircraft, epoxy resin is most often used, which is a type of thermosetting plastic. Compared to other similar materials (such as polyester resin), epoxy resin is significantly stronger. In addition, it is better able to withstand high temperatures. There are many varieties of epoxy resins that vary in performance, curing time and temperature, and cost.

Fiberglass and carbon fiber are most often used as reinforcing fibers in the production of aircraft. Fiberglass has good tensile and compressive strength, high impact resistance. It is an easy-to-work, relatively inexpensive and widespread material. Its main disadvantage is its relatively large weight. Because of this, it is difficult to make a load-bearing body from fiberglass, which could compete with similar aluminum in lightness.

Carbon fiber is generally stronger in tension and compression than fiberglass, and much more rigid in bending. It is also significantly lighter than fiberglass. However, its resistance to impact loads is somewhat lower, the fibers are quite brittle and break with a sharp impact. These characteristics are greatly improved in the "reinforced" epoxy type of carbon fiber used in the horizontal and vertical stabilizers of the Boeing 787.

Carbon fiber has a higher cost than fiberglass. Prices have fallen somewhat since the innovations of the B-2 bomber (during the 1980s) and the Boeing 777 (during the 1990s). Well-designed carbon fiber structures can be significantly lighter, than similar aluminum ones, sometimes by more than 30%.

Advantages of composite materials. Composite materials have several significant advantages over metals, wood or fabric. Most often, lighter weight is cited as the main advantage. However, it should be understood that an aircraft body made of a composite material will not necessarily be lighter than a metal one. It depends on the characteristics of the case, as well as on the material used.

A more important advantage is the ability to create a very smooth and complexly curved airfoil using composite materials, which can significantly reduce air resistance. It is for this reason that in the 60s of the last century, glider designers switched from metal and wood to composite materials.

Composite materials are widely used by aircraft manufacturers such as Cirrus and Columbia. Due to the reduction of air resistance, the aircraft of these companies are distinguished by high flight characteristics, despite the presence of a fixed landing gear. Composite materials also help mask radar signatures in stealth designs (in aircraft such as the B-2 strategic bomber and the F-22 multirole fighter). Today, composite materials are used in the manufacture of any aircraft - from gliders to helicopters.

The third advantage of composite materials is the absence of corrosion. Thus, the fuselage of the Boeing 787 is made entirely of composite materials, which allows this aircraft to withstand a greater pressure drop and greater humidity in the cabin than previous generations of airliners allowed. Engineers are no longer concerned about the problem of corrosion due to moisture condensation on hidden parts of the fuselage skin (for example, under an insulating coating). As a result, the long-term operating costs of airlines can be substantially reduced.

Another advantage of composite materials is good performance in a bending environment (for example, when used in helicopter rotor blades). Unlike most metals, composite materials do not suffer from metal fatigue and cracking. With proper design, rotor blades made of composite material have a significantly higher standard operating time than metal ones. Because of this, most modern large helicopters have fully composite blades, and sometimes a composite rotor hub.

Disadvantages of composite materials. Composite structures have their drawbacks, the most important of which is the absence of visual signs of damage. Composite materials react differently to impact than other materials, and damage is often invisible to the naked eye.

For example, if a car crashes into an aluminum fuselage, a dent will be left on the fuselage. If there is no dent, there is no damage. If a dent is present, the damage is determined visually and repaired. In composite structures, low-impact impact (for example, from a collision or a dropped tool) often leaves no visible damage on the surface. In this case, a wide delamination zone can occur in the impact zone, which spreads funnel-shaped from the impact point. Damage to the posterior surface of a structure can be significant—and yet completely invisible. As soon as there are reasons to believe that an impact (even of a minor force) has occurred, it becomes necessary to invite a specialist to inspect the structure and look for internal damage. A good sign of delamination of the fiber structure when using fiberglass is the appearance of "whitish" areas on the surface of the case.

A moderate impact (for example, in a collision with a car) leads to local damage to the surface, which is visible to the naked eye. The damage zone is larger than the damage on the surface and needs to be repaired. A high-impact impact (for example, a bird or hailstone hitting the aircraft body during flight) results in a hole and significant structural damage. In the case of impacts of medium and high strength, the damage is visible to the eye, but the impact of low strength is difficult to determine visually (Fig. 2-16).

If the impact caused delamination, surface destruction or a hole, it is imperative to carry out repairs. Pending repair, the damaged area should be covered and protected from rain. Parts made of composite material often consist of a thin shell with a porous inner layer underneath (the so-called “sandwich” construction). Excellent in terms of structural rigidity, this structure is susceptible to moisture penetration, which can later lead to serious problems. Putting a piece of "duct tape" over the hole is a good way to temporarily protect against water, but it's not a structural repair. Nor is it a repair to use paste to fill holes, although this method can be used for cosmetic purposes.

Another disadvantage of composite materials is their relatively low heat resistance. While the temperature limits of use vary with different resins, most resins begin to lose strength at temperatures above 65°C. To reduce temperature exposure, the composite body is often painted white. For example, the underside of a wing painted black and located above a hot asphalt pavement on a sunny day can heat up to more than 100°C. The same structure painted white rarely warms up to more than 60°C.

Composite aircraft manufacturers often give specific recommendations on acceptable hull colors. When repainting the aircraft, these guidelines must be followed exactly.

The cause of thermal damage can often be a fire on board. Even a quickly extinguished fire in the brake system can damage the lower wing skins, struts or landing gear wheels. Composite materials are also easily damaged by various solvents, so composite structures cannot be treated with such chemicals. To remove paint from composite parts, only mechanical methods are used, such as metal powder blasting or sandblasting. Solvent damage to high-value composite parts is relatively uncommon and such damage is usually beyond repair.

Fluid leakage on composite structures. Concerns are sometimes expressed about fuel, oil or hydraulic fluid getting on composite structures. It should be said that with modern epoxy resins this is usually not a problem. As a rule, if the leaking liquid does not corrode the paint, it cannot damage the composite material underneath. For example, some aircraft use fiberglass fuel tanks, in which the fuel is in direct contact with the composite surface without the use of a sealant. Some inexpensive polyester resins can be damaged if they come into contact with a mixture of motor gasoline and ethyl alcohol. More expensive resins, like epoxy, can safely come into contact with automotive gasoline, as well as aviation gasoline (100 octane) and jet fuel.

Lightning strike protection. An important factor in aircraft design is protection against lightning strikes. When lightning strikes an aircraft, its structure is exposed to enormous power. Whether you are flying a general purpose aircraft or a large airliner, the basic principles of lightning protection are the same. Regardless of the size of the aircraft, the energy from the impact must be distributed over a large surface area - this allows you to reduce the current per unit area of \u200b\u200bthe skin to an acceptable level.

When lightning strikes an aircraft made of aluminum (due to its electrical conductivity), electrical energy is naturally distributed throughout the aluminum structure. In this case, the main task of designers is to protect electronic equipment, fuel system, etc. The outer skin of the aircraft must provide a path of least resistance for electrical discharge.

In the case of an aircraft made of composite materials, the situation is different. Fiberglass is an excellent electrical insulator. Carbon fiber conducts electricity, but not as well as aluminum. Therefore, the outer layer of the composite skin must have additional electrical conductivity. This is usually achieved with a metal mesh embedded in the skin. The most commonly used meshes are aluminum or copper - aluminum for fiberglass, copper for carbon fiber. Any structural repair of lightning protected surfaces must include the restoration of the metal mesh.

In the event that the design of a composite aircraft requires the presence of an internal radio antenna, special “windows” must be left in the lightning protection grid. Internal radio antennas are sometimes used in composite aircraft because fiberglass is transparent to radio waves (whereas carbon fiber is not).

The future of composite materials. In the decades since the end of World War II, composite materials have taken an important place in the aviation industry. Thanks to their versatility and corrosion resistance, as well as their good strength-to-weight ratio, composite materials allow the most daring and innovative design ideas to be realized. Used in aircraft ranging from the Cirrus SR-20 light monoplane to the Boeing 787 airliner, composite materials play a significant role in the aviation industry and their use will only expand (Figure 2-17).

Monocoque

(fr. monocoque) type of hull, aircraft structure, characterized by a rigid skin, reinforced with transverse and longitudinal sets - a frame.

New dictionary of foreign words.- by EdwART,, 2009 .

Monocoque

[fr. monocoque] - one of the main parts of the aircraft structure - a well-streamlined hollow beam with a rigid wooden or metal sheathing, to which the wings, tail, engine, landing gear, etc. are attached.

A large dictionary of foreign words. - Publishing house "IDDK", 2007 .

Monocoque

A, m. (fr. monocoque Greek monos one + fr. coque body).
av. A type of aircraft body characterized by a rigid skin using transverse and longitudinal fasteners forming a frame.

Explanatory Dictionary of Foreign Words L. P. Krysina.- M: Russian language, 1998 .

Synonyms:

See what "monocoque" is in other dictionaries:

monocoque- a, m. monocoque adj. Monocoque. A type of aircraft, which is a monolithic (one-piece), constituting, as it were, a single shell, glued together from strips of plywood in the form of a cigar. 1925. Weigelin Sl. avia. What is a monocoque fuselage? Fuselage (body... Historical Dictionary of Gallicisms of the Russian Language

- (English, French monocoque, from Greek monos one, single and French coque, literally shell, shell) the design of the fuselage or its tail boom, engine nacelle, etc. round, oval or other section, consisting of a thick ... Encyclopedia of technology

Exist., Number of synonyms: 1 bar (55) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

LFG Roland C.II, Germany, 1916 one of the first aircraft with a pure monocoque fuselage ... Wikipedia

monocoque- monok ok, a (air) ... Russian spelling dictionary

monocoque- (2 m); pl. monoko / ki, R. monoko / kov ... Spelling Dictionary of the Russian Language

Aircraft skin - a shell that forms the empennage and the outer surface of the aircraft body. It is necessary to give the aircraft a streamlined shape. The aerodynamic performance of the aircraft largely depends on how high-quality the skin will be.

Sheathing material

Modern aircraft skins are made from panels or individual sheets of aluminum alloys (or titanium and stainless steel) molded to the surface of the wings or fuselage. Fixed panels or sheets are most often attached to the frame with countersunk riveting, while removable ones are connected with flush-head screws. Sheathing sheets are joined end-to-end. Quite often, large-monolithic finned panels and a skin layer with honeycomb core are used for sheathing fuselages. Antenna fairings (radio-transparent skin elements) are made of honeycomb or monolithic composite material. Recently, composites have also been used as sheathing panels and power units.

Depending on the material used for the construction of the aircraft, the aircraft skin can be:

metal: steel, aluminum alloys, titanium;
wood (veneer or plywood);
percale (linen);
composite materials;
laminated film.

Aircraft skin history

The first aircraft had a skin made of linen, which was impregnated with varnish (hence, in fact, the name itself appeared), the fuselages quite often had no skin at all. Later, sheathing began to be made of wood - plywood and veneer, which were also impregnated with varnish.

With the development of technology, the skin was made of aluminum, smooth and corrugated. To date, exclusively smooth metal skin is used. True, on light aircraft you can still find linen sheathing. This is an extremely rare phenomenon, since it is effectively replaced by polymer films.

Types of skins

In aviation, there are two types of skin - soft "non-working" and hard "working". Nowadays, rigid metal skin has an advantage, as it fully meets the requirements of strength, aerodynamics, weight and rigidity. It perceives loads in the form of twisting and bending moments, external aerodynamic loads and loads of shear forces acting on the aircraft frame. Materials for the production of working skin: titanium, aluminum and steel alloys, aircraft plywood, composite materials. Titanium and steel are most commonly found in supersonic aircraft designs.

The non-powered sheathing is not included in the power circuit, since the load from the sheathing is immediately transferred to the frame. The material for its manufacture can be percale (canvas).

Wing skin

Depending on the type of construction, the empennage and wing skin can be thick, consisting of a monolithic milled or pressed panel, three-layer or thin, reinforced with a special stringer set. At the same time, a special filler is located in the inter-sheathing space (honeycombs made of foam, foil or special corrugation). It is important that the wing skin retains its predetermined shape and is rigid. The formation of folds on it provokes aerodynamic resistance.

The upper skin of the wing under the action of a bending moment is loaded with cyclic compressive forces, and the lower skin, respectively, with tensile forces. For this reason, high-strength materials that perform well in compression are typically used for top compression panels. In turn, materials with high fatigue characteristics are used for the lower tensioned skin. The skin material for supersonic aircraft is selected taking into account the heating in flight - conventional aluminum alloys, heat-resistant aluminum alloys, steel or titanium.

To increase the strength and survivability of the skin along the length of the wing of the aircraft, the number of joints that have a smaller resource compared to the main skin is sought to be minimized. The weight of the wing skin is 25-50% of the total mass.

fuselage skin

It should be noted right away that it is selected taking into account the current load. The lower area of the skin perceives compressive loads by the part that is attached to the stringers, and the upper area perceives tensile forces with absolutely the entire area of the skin. The thickness of the skin in the pressurized fuselage is selected depending on the internal overpressure. To improve the survivability of the fuselage on the skin, stopper tapes are often used to prevent the spread of cracks.

The connection of the skin and frame elements

There are three ways to connect the frame with the skin:

the skin is attached to the frames;
the skin is attached to the stringers;
the skin is attached to both frames and stringers.

In the second case, only longitudinal rivet seams are formed, while there are no transverse ones, which has a positive effect on the aerodynamics of the fuselage. Loose skin on the frames loses stability at lower loads, which increases the mass of the structure. In order to avoid this, the skin is connected with an additional pad (compensator) to the frame. The first method of fastening is used exclusively in stringerless (skinned) fuselages.

A honeycomb skin is attached to the frames. It includes a core and two metal panels. Honeycomb construction is a hexagonal type material consisting of metal. There is glue in the core, which allows you to not use rivets at all. This design is capable of transmitting stress over the entire surface and is characterized by high resistance to deformation.