1 WING

The wing is the principal structural unit of the . It has several functions beyond that of providing lift. For a wing to produce "lift", it must be oriented at a suitable angle of attack relative to the flow of air past the wing. In aerodynamics, angle of attack (AOA) specifies the angle between the chord line of the wing of a fixed-wing and the vector representing the relative motion between the aircraft and the atmosphere.

On larger the engines are mounted in either attached to the wing or mounted in the wing. The nacelles also provide a housing for the when it is retracted. The space within the wing is usually used for fuel storage.

The main geometrical features of a wing are its span; the area of the wing; its dihedral angle; its sweepback angle; and the wing section.

Dihedral angle is the upward angle of an aircraft's wing, from the to the . The amount of dihedral determines the amount of inherent stability along the roll axis. Although an increase of dihedral will increase inherent stability, it will also decrease lift, and increase drag.

The design of the wing depends on the size, weight, and use of the airplane. Generally, there are two kinds of wing design: cantilever and semi-cantilever. The semi-cantilever usually has one, or perhaps two, supporting wires or attached to each wing and the .

As far as the internal structure is concerned, there are three general types of conventional wings: monospar, two-, and multispar. Stringers are longitudinal members which are attached to the upper and lower skin to make it stiff. They are used in the design of a wing with . Ribs are the basic elements of the wing structure which give the wing section its shape and also transmit the air loads from the skin to the spars.

2 Many of the control functions are provided by special devices built into the wing. Most obvious are the and landing flaps.

Flaps are high lift devices. There are many different types of flaps used, with the specific choice depending on the size, speed and complexity of the aircraft on which they are to be used, as well as the era in which the aircraft was designed. Plain flaps, slotted flaps, and Fowler flaps are the most common. Krueger flaps are positioned on the of the wings and are used on many jet airliners.

The leading edge is the part of the wing that first contacts the air. The leading edge may be equipped with e.g. leading edge extensions, leading edge slats, leading edge slots, vortex generators. The of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge rejoins. Essential control surfaces are attached here to redirect the air flow and exert a controlling force by changing its momentum. Such control surfaces include ailerons on the wings for roll control, elevators on the controlling pitch and the on the fin controlling yaw. Elevators and ailerons may be combined as on tailless aircraft. Other surfaces and equipment that may be attached to the trailing edge of an aircraft's wing or on its control surfaces include: trim tabs, servo tabs, anti-servo tabs, and flaps.

Vocabulary structural konstrukční, strukturální to provide poskytovat, vytvářet aerodynamics aerodynamika angle of attack úhel náběhu chord line tětiva atmosphere atmosféra, prostředí to mount montovat, uložit gondola housing kryt landing gear podvozek to retract zatahovat fuel storage uložení paliva obvious zřejmý, jasný landing přistávací klapka křidélko 3 dihedral angle úhel vzepětí sweepback angle úhel šípu wing section profil křídla wing root kořen křídla wing tip špička/konec křídla inherent stability přirozená stabilita roll axis osa klonění weight hmotnost cantilever wing samonosné křídlo semicantilever wing polosamonosné křídlo spar nosník křídla, podélník monospar jednonosníkový multispar vícenosníkový stringer tvarový podélník, podélná výztuha member článek, konstrukční prvek skin potah stiff tuhý stressed skin nosný potah žebro to transmit přenášet load zatížení plain flap jednoduchá klapka slotted flap štěrbinová klapka Fowler flap Fowlerova klapka Kruegerova klapka leading edge náběžná hrana trailing edge odtoková hrana, zadní hrana extension nástavec, prodloužení slat slat, náběžná klapka slot slot, štěrbina turbulátor, vyvíječ vírů, vířič to rejoin opět se spojit to redirect přesměrovat air flow proud vzduchu to exert vyvinout, projevit, uplatnit momentum hybnost, impuls, kinetická energie aileron křidélko tailplane stabilizační plocha elevon vyvažovací klapka pomocná klapka

Exercises 1. Read and translate angle: dihedral angle, sweepback angle, aileron angle, angle of attack wing: cantilever wing, delta wing, dihedral wing, upper wing, stressed-skin wing, high-aspect-ratio wing, long chord wing, multispar wing, swept-back wing, fixed wing 4 edge: leading edge, fixed leading edge, movable leading edge, trailing edge, trailing edge flap, tip edge axis: longitudinal axis, axis of symmetry, rudder axis, axis, horizontal axis lift: tail lift, high-lift devices, wing lift, static lift ratio: lift-drag ratio, aspect ratio skin: double skin, stressed skin, upper skin, sandwich skin, fuselage top skin fin: two-spar fin, tapered fin, swept-back fin, fixed fin

2. Fill in The wing has several functions beyond that of ...... lift. On larger airplanes the engines are mounted in ...... either attached to the wing or mounted ...... it. The nacelles also provide a housing for the landing ...... when it is ...... The ...... within the wing is usually used for fuel ...... The main geometrical ...... of a wing are its ...... ; the area of the wing; its dihedral angle; its ...... angle; and the ...... section. Dihedral angle is the upward ...... of an aircraft's wing, from the wing ...... to the ...... tip. Generally, there are two kinds of wing design:...... and ...... Stringers are longitudinal members which are ...... to the upper and ...... skin to make it ...... Ribs transmit the air loads from the skin to the ...... There are many different types of flaps used, with the specific choice ...... on the size, ...... and complexity of the aircraft on which they are to be used. The leading ...... is the part of the wing that first contacts the air. The trailing edge of a wing is its rear edge, where the ...... separated ...... the leading edge ...... Elevators and ailerons may be combined as ………………………on tailless aircraft.

3. Put into plural The leading edge is the front edge of the wing. The airplane is moving around three axes. The horizontal tail consists of a and an elevator. On a large airplane the engine is mounted in a nacelle. This type of wing has no stringer. An automatic form of this device is also used. The elevator controls the angle of attack. A fin is fixed and a rudder is movable.

4. Find opposites To retract the landing gear, landing, horizontal, front, leading edge, movable, high, down, small, upper, similar, different, internal, monospar, maximum, conventional, single, civil, obvious, stiff, longitudinal, climb, low-wing, heavier-than-air, generally, assembly, anhedral angle

5 5. Answer 1. What is the main function of the wing? 2. Where are the engines mounted on larger airplanes? 3. What purpose is the space within the wing used for? 4. What are the main geometrical features of a wing? 5. How would you define the term “dihedral angle”? 6. What factors does the design of the wing depend on? 7. How many kinds of wing designs are there? 8. When are stringers used? 9. Which part of the wing structure gives the wing section its shape? 10. What types of flaps do you know? 11. What is the difference between the leading edge and the trailing edge? 12. Explain the term “elevon”.

6. Interpret Another method for increasing lift is to change the curvature, or camber, of the wing. In general, the greater the curvature, the lower the efficiency at higher speeds. The trailing edge flaps provide both high lift and high efficiency by making it possible for the pilot to change the curvature according to the flight conditions. The increase of lift in this way is about 10 percent.

7. Give a short description of a wing

Additional materials Elevons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence the name. They are frequently used on tailless aircraft. A leading edge slot is a fixed aerodynamic feature of the wing of some aircraft to reduce the stall speed and promote good low-speed handling qualities. A leading edge slot is a span-wise gap in each wing, allowing air to flow from below the wing to its upper surface.

Leading edge slats are aerodynamic surfaces on the leading edge of the wings of fixed-wing aircraft which, when deployed, allow the wing to operate at a higher angle of attack. A higher coefficient of lift is produced as a result of angle of attack and speed, so by deploying slats an aircraft can fly at slower speeds, or take off and land in shorter distances. They are usually used while landing or performing manoeuvres which take the aircraft close to the stall, but are usually retracted in normal flight to minimize drag.

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Tail unit () The tail unit is the assembly of the vertical tail (), the horizontal tail (horizontal stabilizer, tailplane), and the small section of the rear of the fuselage. Its purpose is to stabilize the airplane in flight, i.e. to make sure that the resultant of all the air forces on the airplane passes through the centre of gravity. The vertical tail consists of a fin which is fixed to the fuselage and gives directional stability to the aircraft, and the rudder which is movable and by means of which the direction of flight can be controlled. It is used to control turns in conjunction with the ailerons. The horizontal tail lies in a horizontal plane and usually consists of a stabilizer and an elevator. The elevator controls the angle of attack of the wings by moving the tail up and down. The internal structure of the tail unit is similar to that of the wings. It is usually of all metal construction of the cantilever type. There are many shapes and different arrangements, however, that can be used in the design of the tail unit.

Fuselage mounted Cruciform T-tail Flying tailplane

Pelikan tail V-tail Inverted V-tail X-tail

In some aircraft trim devices are provided to eliminate the need for the pilot to maintain constant pressure on the elevator or rudder controls. The trim device may be:  a trim tab on the rear of the elevators or rudder which acts to change the aerodynamic load on the surface.  an adjustable stabilizer into which the stabilizer may be hinged at its spar and adjustably jacked a few degrees in incidence either up or down. Usually controlled by a cockpit crank. Multi-engined aircraft often have trim tabs on the rudder to reduce the pilot effort required to keep the aircraft straight in situations of asymmetrical thrust, such as single engine operations. 7 A design (French for "duck") is a wing configuration of fixed-wing aircraft in which the forward horizontal surface is smaller than the rearward one, the former sometimes being known as the "canard" or foreplane, while the latter is the main wing. It tends to be less controllable than a conventional design because ailerons on the main wing may be subject to turbulence from the canards. Canards are often said to have poor stealth characteristics because they present large, angular surfaces that tend to reflect radar signals.

Vocabulary tail unit ocasní plochy assembly sestava, soubor, skupina vertical tail svislé ocasní plochy horizontal tail vodorovné ocasní plochy section část, díl rear záď, zadní část to stabilize stabilizovat resultant výslednice centre of gravity těžiště fin kýlová plocha, kýlovka fixed pevný, připevněný rudder směrové kormidlo, směrovka stabilizer stabilizátor, stabilizační plocha elevator výškové kormidlo all-metal celokovový cruciform křížovitý T-tail ocasní plochy tvaru T flying tailplane plovoucí ocasní plochy inverted obrácený adjustable stavitelný, nastavitelný, regulovatelný jacked zvednutý incidence náběh crank klika, rukojeť canard uspořádání s vodorovnými plochami kormidel vpředu rerward zadní, dozadu foreplane přední ocasní plochy, příďová plocha, přední plocha 8 to be subject být vystaven, podléhat turbulence turbulence stealth technologie “stealth”, nezachytitelný radarem angular zakřivený, zalomený, hranatý to tend to mít tendenci k to reflect odrážet

Exercises 1. Fill in the prepositions The tail unit is the assembly ...... the vertical tail, the horizontal tail, and the small section ...... the rear ...... the fuselage. Its purpose is to stabilize the airplane...... flight. The vertical tail consists ...... a fin which is fixed ...... the fuselage and gives directional stability ...... the aircraft. The rudder is used to control turns ...... conjunction ...... the ailerons. The horizontal tail lies ...... a horizontal plane. The elevator controls the angle ...... attack ...... the wings ...... moving the tail up and down. The internal structure ...... the tail unit is similar ...... that ...... the wings. A trim tab ...... the rear ...... the elevators or rudder acts to change the aerodynamic load...... the surface. A canard design is a wing configuration ...... fixed-wing aircraft ...... which the forward horizontal surface is smaller than the rearward one.

2. Form verbs from the following nouns Assembly, stabilizer, flight, stability, move, direction, control, construction, arrangement, design, elimination, need, maintenance, pressure, elevator, load, reduction, requirement, operation, configuration, tendency, reflection

3. True or false (if so, correct it) The horizontal tail consists of a fin which is fixed to the fuselage and gives vertical stability to the aircraft. The rudder is movable and by means of the rudder the direction of flight can be controlled. The horizontal tail lies in a horizontal plane and usually consists of a stabilizer and a rudder. The elevator controls the angle of attack of the wings by moving the tail up and down. The internal structure of the tail unit is different from that of the wings. The internal structure of the tail unit is usually of wooden construction of the semicantilever type. 9

Multi-engined aircraft often have trim tabs on the fin to reduce the pilot effort required to keep the aircraft straight. Canards are often said to have poor stealth characteristics.

4. Turn into passive The tail unit stabilizes the airplane in flight. The rudder controls turns in conjunction with the ailerons. The elevator controls the angle of attack of the wings by moving the tail up and down. Trim devices eliminate the need to maintain constant pressure on the elevator. A trim tab on the rear of the elevators or rudder changes the aerodynamic load on the surface. Trim tabs on the rudder reduce the pilot effort required to keep the aircraft straight. The pilot is changing the direction of flight.

5. Match the expressions and their definitions 1. airplane a. plane, helicopter, or other vehicle that flies 2. aircraft b. a part on the back edge of an aircraft's wing that is used in making one side of the aircraft move higher than the other 3. horizontal c. an aircraft with wings and at least one engine 4. rudder d. an aircraft control surface that combines the functions of an elevator and a horizontal stabilizer. 5. aileron e. straight and parallel to the ground 6. stability f. flat piece of wood or other material at the back of a boat or plane that is moved to change the direction of travel 7. flying tailplane g. the ability of something to remain balanced and not fall or shake

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Landing gear

The landing gear serves for supporting an airplane when it is not in the air and for providing its movement on the ground in the take-off, landing and taxiing. A classification of different types of landing gear built and flown over the years is very difficult. Considering only the most frequently used, and therefore probably the most successful, we have: 1. Conventional landing gear, also known as a tail-wheel type. The main landing gear wheels are located each side of the centreline ahead the centre of gravity, with a steerable tail wheel located aft near the rudder. This arrangement is usually light, but it has the increased problems with vision, ground manoeuvring, and braking. 2. known as nose-wheel type. The main wheels are located each side of centreline behind the centre of gravity, with a steerable nose wheel mounted on centreline forward. This configuration is noted for ease of ground handling and it does not nose over when brakes are applied. Originally developed by Glen Gurtiss back in 1908, it is the most widely accepted arrangement. 3. Tandem-wheel landing gear, two wheels mounted one behind the other on the airplane centreline. The larger wheel is usually located just behind the centre of gravity, with a smaller wheel forward. Tandem gear is difficult to taxi in a crosswind, even with a steerable front wheel. The landing gear must withstand severe impacts which are absorbed by some type of shock absorbers. Also known as shock struts, they use one of the following energy absorption control methods: shock cord, air and oil (also called oleo ), fluid alone, springs. Modern aircraft are fitted with hydraulic disc brakes. Wheel braking action may be applied to both wheels at the same time, or to either of both wheels. Landing gears may be either fixed or retractable. A fixed landing gear creates a considerable amount of drag; high-speed airplanes must retract their landing gear to realize maximum performance. Retraction may be accomplished by electrical or hydraulic systems, and the landing gear may be folded into the wings, fuselage or pods.

11 Vocabulary landing gear přistávací zařízení, podvozek landing přistání taxiing pojíždění tailwheel landing gear záďový podvozek wheel kolo centreline střednice, osa, osová čára centre of gravity těžiště steerable řiditelný tail wheel ostruhové kolo rudder směrové kormidlo vision výhled, rozhled braking brzdění tricycle landing gear tříkolový podvozek nosewheel landing gear příďový podvozek main wheel hlavní podvozek to be noted for vyznačovat se (čím), být známý (čím) handling ovládání, řízení, obsluha to nose over převrátit (se), převrhnout letoun to apply brakes brzdit to accept přijmout tandem-wheel landing gear tandemový podvozek crosswind boční vítr severe prudký, silný impact náraz to absorb absorbovat, pohltit tlumič shock strut tlumicí vzpěra shock cord tlumicí kabel/lano/šňůra vzpěra s olejovým tlumičem fluid kapalina spring pružina hydraulic hydraulický disc brake kotoučová brzda fixed pevný retractable zatahovací considerable značný amount množství to retract zatahovat performance výkon retraction zatahování to accomplish provádět, dosáhnout electrical elektrický 12 to fold skládat, zasunout

Exercises 1. Read and translate Landing gear: forward-retracting landing gear, main gear, tricycle landing gear, tail-wheel landing gear, steerable gear, tandem gear, retractable landing gear, fixed landing gear, lowered landing gear strut: shock absorber strut, nose-wheel strut, main-wheel strut, oleo strut, oleopneumatic strut, spring strut retraction: automatic retraction, manual retraction, too-early retraction, hydraulic retraction, electrical retraction brake: brakes off, brakes on, to apply the brakes, landing brakes, disc brake, retractable air brakes

2. Fill in the missing words A classification of different types of landing gears...... and ...... over the years is very difficult. Conventional landing gear is also ...... as a tail-wheel type. The main landing gear wheels are ...... each side of the centreline ahead the centre of ...... This arrangement is usually light, but it has the increased ...... with vision, ground...... , and braking. With tricycle landing gear, the main wheels are located each side of ...... behind the centre of...... , with a ...... nose wheel mounted on centreline forward. This configuration is ...... for ease of ground handling and it does not nose over when brakes are ...... It was originally ...... by Glen Gurtiss, and it is the most widely ...... arrangement. Severe impacts are ...... by shock absorbers. Modern aircraft are ...... with hydraulic disc brakes. Maximum performance must be ...... Retraction may be ...... by electrical or hydraulic systems, and the landing gear may be ...... into the wings.

3. Form adjectives by means of the suffix -able or –ive To retract, to accept, to steer, to manoeuvre, to use, to transport, to move, to control, to suit, to change, to allow, to observe, to consider, to compress

13 4. Read 1st pilot, 28%, 155 miles, 3rd wheel, 2x, Mach 2.5, 33 seconds, 4th engine, 48 degrees, 1,000 km/h, 30,000 ft, the 1960s, ¼, DC 10, Boeing 727, 1,576m, 55 hours, 2nd axis, 1/3, 13,000,000 passengers, 1,328m runway, 89.6 MPa, 3.6 by 9.8, 327.000lb, 44 tons, 325-365 m.p.h., TU 104, 25 sec., 120 h.p., 15,000 gallons

5. Give the correct form of the verb The landing gear serves for (to support) an airplane on the ground. The nose gear prevents the airplane from (to nose over). The world largest aircraft are capable of (to move) large quantities of cargo. The elevator controls the angle of attack by (to move) the tail up and down. The power plant is a means of (to create) thrust. After (to taxi) the airplane got to the runway. In addition to (to be) more efficient, device is easily operated.

6. Answer 1) What is the purpose of the landing gear? 2) Which types of the landing gear are the most successful? 3) Where are the main landing gear wheels located in case of tailwheel landing gear? 4) When was the tricycle landing gear developed? 5) What does the nose wheel prevent? 6) Why is the nosewheel steerable? 7) Describe the third arrangement of the landing gear. 8) What are its advantages and disadvantages? 9) What must the landing gear withstand? 10) Name some energy absorption control methods. 11) What kinds of brakes are used in modern aircraft? 12) Why is it impossible for high-speed airplanes to have a fixed landing gear? 13) How is the landing gear retraction accomplished?

7. Interpret The landing gear with the nosewheel is called the tricycle landing gear, and most modern airliners have the tricycle landing gear. This design has some advantages, namely better visibility during taxiing, and makes the airplane more stable during landing. It retracts forward or backward into the fuselage. The main landing gear includes wheels to taxi, disc wheel brakes to slow up the motion of the airplane in the landing, retracting mechanism to retract it during the flight and structural members for the attachment of the landing gear to the primary structure. The shock absorbers must take up the effect of violent impact.

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Fuselage

The fuselage is the structure to which the wings and the tail unit of an airplane are attached and which provides space for the crew, passengers, cargo, controls and other items, depending upon the size and the design of the airplane. The fuselage must be strong enough to withstand different loads acting on it and have a streamlined shape to reduce the drag. Fuselage are varied to suit the aerodynamic geometry and to support much of the equipment. The principal types of fuselage construction are the truss, the semimonocoque, and the . A truss is a group of members forming a rigid framework which may consist of beams, tubes, wires, etc. The members are subjected to compressive and tensile stresses only. The truss is used in sporting and agriculture airplanes and as a part of helicopter airframes. A semimonocoque fuselage consists of longitudinal members (stringers) riveted to the skin and transverse members called frames (formers) which run circumferentially around the insides of the fuselage. The stringers (or or stiffeners) take bending loads from the tail surfaces and the aft fuselage. The frames receive point loads and distribute them into the skin. This type of fuselage is widely used in all kinds of aircraft. A monocoque fuselage is the structure made in a form of a shell and the skin of this shell is sufficient to provide the necessary strength and stiffness. The skin of sandwich construction is especially suitable for the monocoque, but this design is not feasible for many practical aircraft. The fuselage must include related items of structure, such as doors, windows, and floors. Doors and windows are subjected to high pressures because of the external loads and cabin environment. In supersonic airplanes pressurized cabins are used to provide life conditions for the crew and passengers at high altitudes.

Sectioned fuselage showing frames, stringers and skin all made out of aluminium

Vocabulary space prostor crew posádka passenger cestující 15 cargo náklad controls, pl. systém řízení, řízení item položka, součástka to withstand vydržet, odolat load zatížení streamlined proudnicový, aerodynamický drak (letadla) to suit vyhovovat truss příhradový nosník semimonocoque poloskořepinový monocoque skořepinový, skořepina rigid tuhý framework kostra beam nosník tube trubka wire drát compressive stress tlakové namáhání, namáhání v tlaku tensile stress tahové namáhání, namáhání tahem sporting airplane sportovní letoun agriculture airplane zemědělský letoun stringer podélník, tvarový podélník, podélná výztuha to rivet (při)nýtovat transverse příčný frame/former přepážka, rám circumferential obvodový, po obvodu bending load ohybové zatížení aft zadní point load bodové/soustředěné zatížení to distribute rozkládat, rozvádět shell skořepina sufficient dostatečný, postačitelný strength pevnost stiffness tuhost sandwich sendvičový feasible proveditelný, možný environment prostředí supersonic nadzvukový pressurized cabin přetlaková kabina juncture spojení, připojení sectioned v průřezu, v profilu aluminium hliník 16

Exercises 1. Fill in the prepositions The fuselage is the structure ...... which the wings and the tail unit of an airplane are attached and which provides space ...... the crew, passengers, cargo, controls and other items, depending...... the size and the design ...... the airplane. Different loads act ...... the fuselage. Members are subjected ...... compressive and tensile stresses. Longitudinal members are riveted ...... the skin and transverse members called frames run circumferentially ...... the insides ...... the fuselage. Stringers take bending loads ...... the tail surfaces. Frames receive point loads and distribute them ...... the skin. It is not feasible ...... many types ...... aircraft.

2. Interpret Heavy frames and stringers are commonly found near the juncture of the wing and fuselage because this is where the maximum fuselage loads are found. In most cases, the main wing structure passes through, under, or above the main fuselage structure and continues to carry all the wing loads. The pressurised are also loaded internally, as the pressure inside them is higher than the outside air pressure.

3. Make adverbs and use them in sentences Principal, usual, longitudinal, circumferential, short, strong, vertical, high, rigid, complete, stiff, rapid, visual, aerodynamic, sufficient, constant, normal, proper, practical, relative, chief, main, general

4. Find the opposites Compressive stress, longitudinal, external, inside, high pressure, to distribute, thin air, curved, relative, to move, smooth, top surface, vertical, simple, hot and humid, to mount, landing, monospar, fixed, leading edge, upper

5. Answer 1. How is the fuselage defined? 2. What is required of the fuselage? 3. Why are the fuselage airframes varied? 4. What are the principal types of the fuselage construction? 5. What kinds of stress are the truss members subjected to? 6. Where is the truss used? 7. What does a semimonocoque fuselage consist of ?

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8. How are the stringers attached to the skin? 9. How do the frames run? What is their function? 10. Which type of skin is especially suitable for the monocoque? 11. Why are the doors and windows subjected to high pressures? 12. What is the purpose of the pressurized cabin?

6. Interpret The central structure of an airplane connecting the wings and the tail unit is called the fuselage. The fuselage contains the crew, passengers or cargo, and sometimes the power plant.

7. Give a short description of the fuselage

Additional text Sometimes the terms "" and "stringer" are used interchangeably. Historically, though, there is a subtle difference between the two terms. If the longitudinal members in a fuselage are few in number and run all along the fuselage length (usually 4 to 8), then they are called "longerons". Generally, longerons are of larger cross-section when compared to stringers. On large modern aircraft the stringer system is more common because it is more weight-efficient, despite being more complex to construct and analyze. Some aircraft use a combination of both stringers and longerons.

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Turbojet engine

The turbojet engines are further divided into the centrifugal flow and axial flow types. The turbojet engine consists basically of five major sections: an inlet duct, a compressor, a combustion chamber, a gas turbine mounted on a common shaft with the compressor, and an exhaust duct. In the turbojet engine, the compressor draws in atmospheric air and compresses it. At this point the compressed air is divided. Part of it, called primary air, goes directly through the combustion chamber where it is used to support combustion. The remainder, called secondary air, surrounds the combustion chamber, mixing with and cooling the hot gases before they enter the turbine. As the gases pass through the turbine stage, about 75 to 80 percent of their energy is absorbed by the turbine to turn the compressor and accessory gears. Then the gases further expand through the tailpipe to atmospheric conditions. This reaction on the engine, caused by the acceleration of the gases to the extremely high outlet velocity, provides the thrust. The compressor of a centrifugal flow jet engine consists of a rotary impeller which compresses air by centrifugal acceleration. Air is picked up by the radial blades of the rotating impeller and discharged into a diffuser. This annular chamber is provided with a number of vanes forming a series of divergent passages. Then the air passes from the diffuser into the compressor manifolds. The axial flow jet engine has a compressor consisting of a series of airfoil-bladed discs, one behind the other with stator vanes between each disc. These rotors compress the air by accelerating it in a direction along the axis of the engine. Each combination of disc and stator constitutes a stage. The axial flow jet engine is superior to the centrifugal flow jet engine in some respects. Substantial increases in thrust can be obtained by employing an afterburner. It is a second combustion chamber positioned after the turbine and before the nozzle. The afterburner increases the temperature of the gas ahead of the nozzle. The result of this increase in temperature is an increase of about 40 percent in thrust at takeoff and a much larger percentage at high speeds once the plane is in the air. The disadvantage is its very high fuel consumption and inefficiency, though this is often regarded as acceptable for the short periods during which it is usually used.

19 Vocabulary centrifugal flow engine proudový motor s radiálním kompresorem axial flow engine proudový motor s axiálním kompresorem inlet duct vstupní kanál, vstupní ústrojí gas turbine plynová turbina exhaust duct výfukový kanál, výstupní kanál to draw in nasávat primary air primární vzduch remainder zbytek secondary air sekundární vzduch to mix mísit se to cool ochladit stage stupeň accessory pomocný, přídavný, vedlejší gear ústrojí, zařízení, převod to expand rozpínat (se) tailpipe výfuková roura, prodlužovací roura s hnací tryskou to cause způsobit, zapříčinit acceleration zrychlení outlet výstup, výtok outlet velocity výtoková/výfuková rychlost impeller oběžné kolo (dmychadla) centrifugal odstředivý to pick up zachytit radial paprskovitý blade lopatka (turbiny) to discharge vypustit, vytlačit diffuser difuzér annular prstencovitý, kruhový annular chamber kruhová komora vane lopatka (statická) divergent rozbíhavý, divergentní passage průchod, kanál manifold soustava potrubí, koleno trubky, vzduchovod airfoil/aerofoil nosná plocha , profil křídla, plocha, na jejímž povrchu se dosahuje reakce s pohybujícím se vzduchem disc disk, kotouč stator vanes rozváděcí lopatky respect ohled, zřetel fuel nozzle/jet (vstřikovací) palivová tryska injection nozzle/jet vstřikovací (palivová) tryska to atomize rozprašovat 20 lubrication mazání to convert přeměnit to direct nasměrovat to spray rozstřikovat, rozprašovat accessory gears pomocné náhony afterburner přídavné spalování, hořák přídavného spalování ahead před once jakmile consumption spotřeba inefficiency neefektivnost, malá účinnost to regard as považovat za acceptable přijatelný

Exercises

1. Read and translate The centrifugal flow type, an inlet duct, a gas turbine, compressed air, to support combustion, the turbine stage, acceleration of gases, high outlet velocity, a rotary impeller, centrifugal acceleration, radial blades, airfoil-bladed discs, the direction along the axis of the engine, to constitute a stage

2. Read and translate The fuel nozzle supplies the combustion chamber with atomized fuel. The function of the fuel nozzle is to spray finely atomized fuel into the combustion chamber for rapid burning. The spraying effect also prevents an accumulation of fuel. All turbojet engines have also an accessory section and fuel control, starting, cooling, and lubrication systems. The axial flow compressor has two main functional elements: the rotor (blades), and the stator, which consists of rows of blades between the rotor stages. The rotor turns at high speed, picks up air from the stator blades and accelerates it rearward through the next stator stage. The stator blades act as diffusers at each stage. They partially convert high velocity to pressure and direct air flow to each following rotor stage.

3. Form questions The turbojet engine consists of five major sections. The compressor draws in atmospheric air and compresses it. 80 % of the energy of hot gases is absorbed by the turbine to turn the compressor. The gases expand through the tailpipe to atmospheric conditions. Air is picked up by the radial blades of the rotating impeller and discharged into a diffuser. The axial flow jet engine is superior to the centrifugal flow jet engine.

21 4. Fill in the missing words In the turbojet engine, the compressor ...... atmospheric air and ...... it. A part of the compressed ...... goes directly through the ...... chamber where it is used to support combustion. The second part ...... the combustion chamber, mixing with and ...... the hot gases before they ...... the turbine. The reaction on the engine, ...... by the acceleration of the gases to the extremely high ...... velocity, provides the ...... The axial flow jet engine has a compressor...... of a series of airfoil- bladed ...... , one behind the other with stator ...... between each disc. These rotors...... the air by accelerating it in a direction along the ...... of the ...... Each combination of disc and stator constitutes a ......

5. Match the expressions and their definitions 1.consumption a. additional objects, equipment, decorations etc. that make something more useful or attractive 2.shaft b. a compressor achieving a pressure rise by adding kinetic velocity to a continuous flow of fluid through the rotor or impeller 3.accessory c. air kept under a pressure that is greater than atmospheric pressure

4.to convert d. a metal bar in an engine that causes a part to move when another part moves 5.axial compressor e. to change from one system, use, or method to another, or to make something do this 6.compressed air f. the use of something such as fuel or energy, or the amount that people use 7.centrifugal compressor g. a compressor in which the working fluid principally flows parallel to the axis of rotation