外文翻译--飞机的介绍

南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 1 页 附录 外文资料及译文 1.外文资料 : An Introduction to the Airplane Airplanes come in many different shapes and sizes depending on the mission of the aircraft, but all modern airplanes have certain components in common. These are the fuselage, wing, tail assembly and control surfaces, landing gear, and powerplant(s). For any airplane to fly, it must be able to lift the weight of the airplane, its fuel, the passengers, and the cargo. The wings generate most of the lift to hold the plane in the air. To generate lift, the airplane must be pushed through the air. The engines, which are usually located beneath the wings, provide the thrust to push the airplane forward through the air. The fuselage is the body of the airplane that holds all the pieces of the aircraft together and many of the other large components are attached to it. The fuselage is generally streamlined as much as possible to reduce drag. Designs for fuselages vary widely. The fuselage houses the cockpit where the pilot and flight crew sit and it provides areas for passengers and cargo. It may also carry armaments of various sorts. Some aircraft carry fuel in the fuselage； others carry the fuel in the wings. In addition, an engine may be housed in the fuselage. The wing provides the principal lifting force of an airplane. Lift is obtained from the dynamic action of the wing with respect to the air. The cross-sectional shape of the wing as viewed from the side is known as the airfoil section. The planform shape of the wing (the shape of the wing as viewed from above) and placement of the wing on the fuselage (including the angle of incidence), as well as the airfoil section shape, depend upon the airplane mission and the best compromise necessary in the overall airplane design. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 2 页 The control surfaces include all those moving surfaces of an airplane used for attitude, lift, and drag control. They include the tail assembly, the structures at the rear of the airplane that serve to control and maneuver the aircraft and structures forming part of and attached to the wing. The tail usually has a fixed horizontal piece (called the horizontal stabilizer) and a fixed vertical piece (called the vertical stabilizer). The stabilizers provide stability for the aircraft they keep it flying straight. The vertical stabilizer keeps the nose of the plane from swinging from side to side (called yaw), while the horizontal stabilizer prevents an up-and-down motion of the nose (called pitch). (On the Wright brothers first successful aircraft, the horizontal stabilizer was placed in front of the wings. Such a configuration is called a canard after the French word for duck). The hinged part found on the trailing edge of the wing is called the aileron. It is used to roll the wings from side to side. Flaps are hinged or pivoted parts of the leading and/or trailing edges of the wing used to increase lift at reduced airspeeds, primarily at landing and takeoff. Spoilers are devices used to disrupt the airflow over the wing so as to reduce the lift on an airplane wing quickly. By operating independently on each wing, they may provide an alternate form of roll control. Slats at the front part of the wing are used at takeoff and landing to produce additional lift. At the rear of both the aileron surfaces and elevators and rudders are small moving sections called trim tabs that are attached by hinges. Their function is to (1) balance the airplane if it is too nose heavy, tail heavy, or wing heavy to fly in a stable cruise condition； (2) maintain the elevator, rudder, and ailerons at whatever setting the pilot wishes without the pilot maintaining pressure on the controls； and (3) help move the elevators, rudder, and ailerons and thus relieve the pilot of the effort necessary to move the surfaces. The landing gear, or undercarriage, supports the airplane when it is resting on the ground or in water and during the takeoff and landing. The gear may be fixed or retractable. The wheels of most airplanes are attached to shock-absorbing struts that use oil or air to cushion 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 3 页 the blow of landing. Special types of landing gear include skis for snow and floats for water. For carrier landings, arrester hooks are used. Forward motion, or thrust, is generated by a thrust-producing device or powerplant to sustain flight. The powerplant consists of the engine (and propeller, if present) and the related accessories. The main engine types are the reciprocating (or piston type), and the reaction, or jet, engine such as the ram jet, pulse jet, turbojet, turboprop, and rocket engine. The propeller converts the energy of a reciprocating engines rotating crankshaft into a thrust force. Usually the engines are located in cowled pods hung beneath the wings, but some aircraft, like fighter aircraft, will have the engines buried in the fuselage. Other configurations have sometime been used. For instance, the Wright brothers 1903 Flyer had pusher propellers (propellers at the rear of the plane) and the elevators at the front of the aircraft. Many fighter aircraft also combine the horizontal stabilizer and elevator into a single stabilator surface. There are many possible aircraft configurations, but any configuration must provide for the four forces needed for flight. Airfoil An airfoil is any part of an aircraft that is designed to produce lift. The wing is the primary airfoil but the propeller can also be an airfoil as well as the tail surfaces or sometimes even the fuselage itself. An airfoil has a leading edge, a trailing edge, a chord, and camber. The leading edge is the front of the airfoil the portion that meets the air first. The trailing edge is the back of the airfoil the place at which the airflow over the upper surface of the airfoil joins the airflow over the lower surface of the airfoil. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 4 页 The elements of an airfoil The chord of an airfoil is the imaginary straight line drawn through the airfoil from its leading edge to its trailing edge. The camber of an airfoil is the curve of its upper and lower surfaces. This curve is measured by how much it departs from the chord of the airfoil. Some airfoils have very little camber, i.e., the airfoil looks flat, while others have a higher degree of camber the airfoil has more curve. The term upper camber refers to the camber of the upper surface of the airfoil. The term lower camber refers to the camber of the lower surface of the airfoil. The camber of an airfoil affects its lift. The direction of the air that is flowing past an airfoil relative to the path of flight is called the relative wind. The relative wind is always parallel and opposite in direction to the path of flight. Landing Gear Landing gear is the structure under a planes fuselage that allows it to land safely. The earliest landing gear consisted of skids, but designers soon attached wheels to the skids. Landing gear must have some mechanism for absorbing the force of the landing in addition to the airplanes weight. Early gear used flexible material for landing gear struts (the structure that connected the airframe and the wheels). Some landing gear use a shock absorbing system called the oleo strut that cushions the landing and keeps the plane level while landing. There are several types of landing gear: Conventional landing gear consists of two wheels forward of the aircrafts center of gravity and a third, smaller wheel at the tail. This small wheel can turn in any direction. This configuration has the nickname the taildragger because, when the plane is on the ground, the tail of the plane is closer to the ground than the forward end. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 5 页 Tricycle landing gear consists of a forward (nose) wheel and a pair of wheels located midway on the fuselage. The nose gear is steerable by means of the rudder pedals. Tandem landing gear (also called bicycle landing gear) consists of a main gear of two sets of wheels set one behind the other. Landing gear can be either fixed or retractable. Often, smaller, less expensive planes have fixed landing gear-landing gear that remains exposed when the plane is flying-because it is less costly to build and maintain. Retractable landing gear can be retracted into the body of the plane. This feature gets the structure out of the airflow and reduces drag. Aircraft that have to land on water are fitted with pontoons rather than wheels. Some planes had interchangeable pontoons and wheels so that the plane could be used to land both on land and on water. Four Forces of Flight The four forces of flight are lift, drag, thrust, and weight. Lift is the upward force created by the wings moving through the air that sustains the airplane in flight. Lift operates to overcome weight. It must be equal to or greater than the weight of the object in flight and acting in the opposite direction. Lift can be increased by increasing the forward speed of the aircraft or by increasing the angle of attack Drag is the resistance of the airplane to forward motion. It is directly opposed to thrust and is caused by the resistance of air. Thrust is the force exerted by the engine and its propeller(s). It pushes the air backward with the object of causing movement of the airplane in the forward direction. Weight is the downward force due to the weight of the airplane and its load. It is directly opposed to lift 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 6 页 An aircraft is in a state of equilibrium when the thrust and drag are equal and opposite. It will continue to move forward at the same uniform speed. If thrust or drag becomes greater than the opposite force, the aircraft loses its state of equilibrium. If thrust is greater than drag, the aircraft will accelerate. If drag is greater than thrust, the aircraft will lose speed and eventually descend. When lift and weight are equal and opposite, the airplane is in a state of equilibrium. If lift is greater than weight, the aircraft will climb. If weight is greater than lift, the airplane will descend. The four forces of flight Streamlining Streamlining is the shaping of an object, such as an aircraft body or wing, to reduce the amount of drag or resistance to motion through a stream of air. A curved shape allows air to flow smoothly around it. A flat shape fights air flow and causes more drag or resistance. Streamlining reduces the amount of resistance and increases lift. To produce less resistance, the front of the object should be well rounded and the body should gradually curve back from the midsection to a tapered rear section. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 7 页 Streamlining reduces the amount of resistance experienced by an airfoil Angle of Incidence The angle of incidence is the angle between the aircrafts longitudinal axis and the chord of the wing. The angle of incidence is the angle at which the wing is fixed to the aircrafts fuselage. It is the angle formed by the chord of the airfoil and the longitudinal axis of the aircraft.This longitudinal axis of the aircraft is the imaginary line drawn through the fuselage from the front of the aircraft to the rear of the aircraft. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 8 页 Usually, the angle of incidence is the angle formed between the wing and the longitudinal axis of the aircraft body. Flight Control Surfaces The rudder, elevator, and aileron are the primary control surfaces on an airplane. The rudder controls the airplanes yaw, the elevator controls its pitch, and the aileron controls its roll (see the individual dictionary entries for each of these.) Others are addressed below. Wing flaps are a movable part of the wing, normally hinged to the trailing edge (rear edge) of each wing closest to the airplane body. The pilot extends and retracts the flaps. Extending the flaps increases the wing camber and the angle of attack of the wing. This increases wing lift and also increases drag. Flaps enable the pilot to make a steeper descent when landing without increasing airspeed. They also help the airplane get off the ground in a short distance. There are many different types of flaps. Some hinge, some slide, some open with slots, and some help smooth the air over the wing even when high angles of attack are flown during landing. Slats are protrusions from the leading edge (front edge) of a wing. They add to the lift of a wing. Slats and flaps work together to maintain laminar flow (a smooth airflow) over the top of the wing. Spoilers reduce lift. Spoilers are found along the top of the wing. When they arent being used, they fit into or flush with the wings surface. When they are used, they protrude from the wings surface 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 9 页 into the airflow and destroy the laminar flow for a portion of the wing. The size of the spoiler varies according to how much lift is to be spoiled. Different spoiler designs are found on different types of planes, but their function is the same. Some devices only produce drag without affecting the wings lift. These include speed brakes, air brakes, dive flaps, or drag parachutes. They may be located on the wings trailing edge or may protrude from the fuselage. These devices allow very steep descents and rapid changes in airspeed. The pilot can stop their effect almost instantaneously by retracting the devices Axes of Rotation An aircraft has three axes of rotation: vertical, lateral, and longitudinal. Credits - Civil Air Patrol 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 10页 In addition to moving forward, aircraft move about three axes in response to three forces: lift, drag, and side force. These axes can be visualized as three rods that pass through the aircraft so that each intersects the other two. The point of intersection is called the center of gravity. Each of these axes is also perpendicular to the other two. The axis that extends lengthwise through the nose and tail is called the longitudinal axis. Rotation about this axis is called roll. Drag is the force that acts along this axis, but in the opposite direction of the flight path. The axis that extends crosswise from wingtip to wingtip is called the lateral axis. Rotation about this axis is called pitch. Side force acts along this axis. The axis that passes vertically through the center of gravity when the aircraft is in level flight is called the vertical axis. Rotation about this axis is called yaw. Lift acts along this axis. Movement of the ailerons produces changes in roll. Movements of the rudder produce changes in yaw. Movements of the elevator cause changes in pitch. Ailerons The ailerons are one of three primary flight control surfaces found on aircraft. They are movable surfaces that control movement about the longitudinal axis-called roll. The ailerons are used along with the rudder to make turns 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 11 页 . Movement of the ailerons controls movement of the aircraft around its longitudinal axis. One aileron is found at the outer trailing edge of each wing. They impart a rolling motion to the aircraft, making banking possible. Lowering the aileron on one wing raises the aileron on the other. The wing with the lowered aileron rises because of its increase lift, and the wing with the raised aileron moves downward because of its decreased lift. Thus, the effect of moving either aileron is aided by the simultaneous and opposite movement of the aileron on the other wing. Rods or cables connect the ailerons to each other and to the control stick in the cockpit of the plane. Pushing the control stick to the right moves the right aileron up and the left aileron down. This causes the right wing to dip and helps turn the plane to the right. A downward motion of the aileron increases the camber, thus increasing lift and raising the wing. The right aileron moves upward and decreases the camber on the right wing, resulting in reduced lift. Decreased left on the right wing and increased lift on the left wing cause a roll and bank to the right. Trim and Balance Trim refers to balancing an aircraft in flight around its center of gravity. The center of gravity is the point at which an airplane would balance if it were suspended at that point. Balance is important to airplane stability and safety in flight. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 12页 The prime concern of airplane balancing is the fore and aft (front and rear) location of the center of gravity along the longitudinal axis. Location of the center of gravity with reference to the lateral axis is also important. For each item of weight existing to the left of the fuselage centerline, there is an equal weight existing at a corresponding location on the right. This may be upset, however, by unbalanced lateral loading and adverse effects will arise from a laterally unbalanced condition. The pilot can compensate for the resulting wing-heavy condition by adjusting the aileron trim tab or by holding a constant aileron control pressure. However, this places the airplane controls in an out-of-streamline condition, increases drag, and results in decreased operating efficiency. Trim tabs are small surfaces that mechanically or electronically manipulate the rudder, elevator, and ailerons to help stabilize the plane. Trim tabs free the pilot from constantly adjusting the controls. The center of gravity depends on the distribution of weight in the airplane and changes as load items (such as fuel) are shifted or expended. If the center of gravity is displaced too far forward on the longitudinal axis, a nose-heavy condition will result. Conversely, if the center of gravity is displaced too far aft, a tail-heavy condition will result. An unfavorable location of the center of gravity could produce such an unstable condition that the pilot could not control the airplane. The airplane manufacturer sets the fore and aft limits for the location of the airplanes center gravity. Elevators Elevators are one of three primary flight control surfaces found on an airplane. The elevators control the movement of the airplane about its lateral axis. This motion is called pitch. The elevators form the rear part of the horizontal tail assembly and are free to swing up and down. They are hinged to a fixed surface the horizontal stabilizer. Together the horizontal stabilizer and the elevators form a single airfoil. A change in the elevators position modifies the camber of the airfoil, increasing or decreasing lift. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 13页 The elevators are connected to the control stick by control cables. Pushing the stick forward moves the elevators downward. This increases the lift produced by the horizontal tail surfaces and causes the nose to drop. Pulling back on the stick causes the elevators to move upward, decreasing the lift produced by the horizontal tail surfaces and forcing the nose upward. The elevator on an aircraft controls the movement of the aircrafts tail. Rudder The rudder is one of three primary flight control surfaces found on an airplane. It is a movable surface hinged to the fixed surface that is located at the rear of the aircraft called the vertical stabilizer, or fin. The rudder controls movement of the airplane about its vertical axis and causes the airplanes nose to move to the right or left and point in a different direction. This motion is called yaw. Control cables connect the rudder to the rudder pedals. Pushing down the right rudder pedal moves the rudder to the right and causes the plane to turn to the right. Pushing down the left rudder pedal turns the plane to the left. The rudder controls the movement of the aircraft around its vertical 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 14页 axis. Internal Combustion or Reciprocating Engine Another name for a reciprocating engine is an internal-combustion engine. It has this name because the fuel burns inside the engine. It is also often called a piston engine because it has pistons as one of its parts. The major parts of an internal combustion engine are (1) the cylinders, (2) the pistons, (3) the connecting rods, (4) the crankshaft, (5), intake and exhaust valves, (6), the spark plugs, and (7) a valve operating mechanism-also called a cam. Reciprocating engines require fuel, air, compression, and a source of combustion to function. In a modern airplane engine, air mixed with gasoline is drawn into a cylinder, then compressed by a piston moving up and down inside a chamber called a cylinder. A spark from a spark plug ignites the mixture of fuel and air. This causes an explosion that drives the piston downward, creating power. Then the exhaust valve opens and the burned-up gases are pushed past the valve into an exhaust pipe by the piston. Then the process starts over again. This happens hundreds of times a minute. This process is called a four-stroke operating cycle. Parts of a reciprocating engine. Four-stroke five-event cycle. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 15页 Jet Engines Jet engines operate on the application of Newtons third law of motion: for every action there is an equal and opposite reaction. The most common type of jet engine is the turbojet engine. Air from the atmosphere enters the fan section at the front of the engine where it is compressed in the compressor section. Then it is forced into combustion chambers where fuel is sprayed into it and ignited. Gases that form expand rapidly and are exhausted out the rear of the combustion chambers. The energy from these gases spins the fan-like set of blades called a turbine, which rotates the turbine shaft. This shaft, in turn, rotates the compressor, thereby bringing in a fresh supply of air through the intake at the front of the engine. The rest of the energy is expelled out the tail pipe, providing forward thrust. Adding an afterburner section, where extra fuel is sprayed into the gases as they are exhausted and the fuel burns, adds thrust. In a turboprop engine, the exhaust gases rotate a propeller that is attached to the turbine shaft. The propeller provides increased fuel economy at lower altitudes. Another type of turbine engine, called a turbofan or bypass engine, uses a fan to produce additional thrust. This is most efficient at high altitudes. The fourth type of jet engine is the ramjet. The ramjet is a simple engine that lacks a turbine and compression chambers. Ramjets do not function at speeds below the speed of sound, although there are new variations of these called SCRAMjets that are designed to generate supersonic speeds. The engine must be on an aircraft already traveling above the speed of sound (supersonic speed) before it can be used. Supersonic air enters the front of the ramjet and is automatically compressed due to the shape of the engines opening. This compressed air is mixed with fuel in the combustion chamber and ignited, causing the resulting gases and energy to be expelled out of the back and providing forward thrust. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 16页 A rocket engine operates on the same principle as a jet engine but carries its oxygen with it rather than using oxygen from the atmosphere. Engine Cowling The engine cowling is a removable metal covering that houses the engine and sometimes also a portion of the fuselage of an aircraft. It enables the aircraft to fly more efficiently because it reduces the amount of drag it creates. The NACA low-drag engine cowling was invented by Fred Weick, an engineer from the National Advisory Committee for Aeronautics, in 1928. Cowlings are sometimes also used to enclose landing gear. Propeller Configurations Aircraft have had two types of propeller configurations: pusher propellers and tractor propellers. Aircraft with pusher propellers place the propeller assembly behind the engine. The thrust produced by the propeller pushes the airplane forward. Most of the Wrights planes used this type of configuration. The U.S. Army banned this type of propeller configuration in late 1914 after several pilots died in crashes of planes of this type. The Vultee XP-54 is an example of an aircraft with a pusher propeller. Notice that the propeller is located behind the fuselage. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 17页 Credits - U.S Air Force The concept was revived briefly during World War II when the Army Air Corps received designs for a pusher-type aircraft as part of a design competition. In these planes, the propeller was mounted behind the pilot. They appeared to offer better visibility, less drag, and the opportunity to carry more guns in the nose. Three such pusher designs were actually flight tested the Vultee XP-re, Curtiss XP-5, and Northrop XP-56. None went into production. The Blriot monoplane was an early aircraft with a tractor propeller Tractor aircraft have the engine and propeller at the front of the aircraft where the thrust draws or pulls the airplane. Modern aircraft use this type of configuration. the History of Flight The invention of the airplane was a fundamental turning point in history. It redefined the way we fought our wars； revolutionized travel and commerce； fueled the process of technological change； and helped to shape a world in which the very survival of a nation would depend on its scientific and technical prowess. Flight is, and will continue to be, one of humankinds most significant accomplishments. This section features brief essays that describe significant events in aviation history, arranged chronologically on a timeline. Visitors to our Web site will be able to access hundreds of essays on aerospace topics； a rich collection of images； a timeline of significant aviation events； and a dictionary of persons, places, and things that are important to understanding the history of aviation and aerospace. 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 18页 2.译文 飞机的介绍 由于飞机的使命而使它有 许多的形状和尺寸，但是所有的现代飞机有共同的特定成份。这些是机身，机翼 , 尾翼和舵面，起落架和动力装置 . 对于任何的飞机要飞起来 , 它一定要能够克服飞机自身的重量，及它的燃料，乘客 , 和货物。机翼产生大部份的升力在空气中支撑飞机。 为了产生升力，飞机与空气有相对运动。 通常在位于机翼下方的引擎提供推力推动飞机通过空气。 机身是把飞机的所有块以及其他一些大的部件结合在一起，它是飞机的身体。机身通常尽可能多被设计 成流线型减少阻力。 对于机身的设计变化多。机身包括驾驶员座舱那里飞行员和机组人坐的，而且它提供分布区给乘客和货物。 它也可能携带各种不同种类的武器。 有些飞机在机身中携带燃料 ； 其它燃料则在机翼中。 除此之外，一个引擎可能也被安置在机身中。 机翼提供拖起飞机的重要升力。 升力从由重要的机翼的和空气相对运动而被获得。 机翼的代表性形状同样地从翼剖面看到的。机翼的平面形状(如上方所看的翼形状 )和它在机身上的布局 (包括影响它的角度 ) ，还有机身的形状，在飞机的总体设计中考虑飞机的使命和必要的妥协处理是很必要的 . 操纵面（舵面）包括作为姿态，升起和阻力控制那些可动翼面。 他们包括在后面的集群 , 飞机后面的结构是用来控制和操纵飞机它连接在机翼的上面。 尾部通常有固定的水平线块 (叫做水平的安定装置 ) 和固定的垂直块。 (被称为垂直的安定装置 )安定装置提供安定给飞机 -他们保持它飞的直线。 垂直的安定装置使机头不从边到边 (被称为首摇 ) 摇摆而水平的安定装置避免机头 (被称为纵摇 ) 的一个上上下下运动。 (在莱特兄弟第一架飞机南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 19页 上，水平的安定装置在机翼之前。 如此的一个结构让人惊奇。 它装铰链 , 在机翼的边缘上部份叫做副翼 。它用来从一边到另一边转动翼。在飞机失速的时候拍打被装铰链或者转动副翼可以增加升力。主要在着路和起飞的时候用到。扰流板是为了要很快地在一个飞机翼上减少升力 ,来打乱在翼上气流的装置。 通过在每个翼上独立地操作，他们可能提供一种横滚控制替代形式。边条翼的前面部份在起飞着路是产生另外的升力。在副翼表面和升降舵后面，方向舵是很小的移动部件称为调整片。它通过铰链连接。他们的功能平衡飞机如果它头重了 , 附于其后重的 , 或装以翼重在稳定的巡航情况下飞行 ； 在控制方面的压力的飞行员的任何的设定飞行员希望维持升降舵，方向 舵和副翼 ； 而且帮助移动升降舵，方向舵和副翼来减轻飞行员移动翼面的困难。 着陆装置 或 起落架 ，是支撑飞机在 地面 停放 ,或在水中起飞和降落 。 该装置可固定或收放 。大多数飞机的轮子被装减震支柱上，减震支柱是用油气填充到柱桶中。 特殊用途的起落装置包括在雪地上可以滑行在水面上可以漂浮。为了能在航空母舰着陆，着陆阻拦钩被应用了。 向前运动或推进是由一个产生推力的装置也就是发动机产生的。动力装置包括引擎和相关的配件。 主要的引擎类型是往复的 (或活塞类型 ), 和喷气的 , 或喷气式飞机引擎 , 像是冲压式喷气发动机，脉膊式喷气 发动机，涡轮喷气发动机和火箭引擎。 螺旋桨把活塞式发动机的旋转曲轴的能量转换成推力。 通常引擎被安装在整流罩中铰接在机翼下方 , 但是一些飞机如战斗机被安装在机身中。 其他结构的那时也被使用过。举例来说，莱特兄弟的 1903年飞行者在飞机的前面有了推力螺旋桨 (螺旋桨在飞机的后面 ) ，升降舵在前面。 许多战斗机也结合水平的安定装置和升降舵变成一个装置面。 有许多可能的飞机结构，但是任何的结构要提供飞行所需的动力。 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 20页 机翼 机翼是飞机被设计产生升力的 那些部份。机翼是主要的翼面 ，但是螺旋桨和尾翼或有时甚至机身本身也可能是翼面。翼面有一个前缘，一个后缘，一根弦和曲面。前缘是机翼的 前面 -首先碰到空气的部分。 后缘是机翼的背面 -在那个地方气流通过机翼的上表面和机翼下表面的气流相碰。 机翼的要素 机翼的弦长是机翼的前缘到后缘 的假想直线。它的曲面是她上下表面的曲线。这一条曲线以它离弦的多少来计算的。有时机翼有一点点弧度，看起来很平坦。 而有时它有很大的弧度 有很大的曲线。上弧是根据机翼的上表面的曲面。下弧是根据机翼的下表面的曲面。机翼的曲面影响它的升力。气流流过机翼的方向相对于飞行轨迹被称作为相对气流。她方向总是和飞行轨迹相平行但相反。 起落架 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 21页 起落架是在让它安全地着陆的一个飞机的机身下面的结构。 最早的起落架有滑橇构成 , 但是设计者很快在它上面装上了轮子。 起落架除 了吸收飞机的重量之外一定还要有吸收着陆的力量的一些机构。早的起落架用柔性的材料作为起落架支柱。 (这个机构连接机身和机轮 ) 当着陆的时候，一些起落架使用一个吸震系统叫做减震支柱，有了这样的减震器可使飞机平稳着陆。 有许多形式的起落架：传统的起落架有在飞机重心前面安装两个轮子再在尾部装第三个小轮子。这个小的轮能在任何的方向转。这一个结构有绰号 尾拖 因为 , 当飞机在地面上的时候，飞机的尾部比前部更接近地面。 前三点式起落架有一个前轮和在机身中部的一对后轮。 前轮利用方向舵脚蹬是可操纵的。 纵排的起落架 (也叫做自行车式起落架 ) 它是由两个轮子组成的主起落架，旁边还有两个辅助轮组成。 起落架有固定的或可收缩的。 通常，比较小又比较便宜的飞机的起落架是固定的，在飞行时也是暴露在外的，因为它的制造和维护比较便宜。 可收缩的起落架能缩回机身之内。 这一个特征使机构避开气流而且减少了阻力。 在水上着陆的飞机配备有浮桶而不是轮子。 一些飞机有了可互换的浮桶和轮子，以便飞机即可在土地有可在水上着陆。 飞行过程中的四种载荷 飞行过程中的四种载荷是升力，阻力，推力和重力。 升力是机翼相对气流的 运动而产生的力。 升力克服了飞机的重力。 它一定相等或大于对象的重力并该力的作用方向相反。升力可由增加飞机的向前速度或增加仰角而增加。 阻力是阻碍飞机向前运动的力。 它和推力相反由空气的阻碍产生。 推力是由引擎和它的螺旋桨的作用产生的。 它通过推动空气向后运动南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 22页 产生推动飞机向前的力。 重力是由于飞机的自身的重量和它的负荷产生的，重力是向下的力。 它和升力相反。 当推力和阻力是大小相等方向相反的时候，一架飞机处于平衡的状态。 它将会作等速直线飞行。 如果推力或阻力变成比相反的力大 ,飞机失去它的平衡的状态。 如果 推进比累赘棒 ,飞机将会加速。 如果阻力比推力大 ,飞机将会失去速度最后下降。 飞行过程中的四种载荷 流线型化 流线型是物体个一个形状 , 像是一个飞机机身或者机翼 ,通过这条空气的流线来减小阻力或阻碍运动。曲线形状让空气平滑地流过它。 平坦的形状抵抗空气流动而且引起较多的阻力或抵抗。 流线型化减少大量抵抗力和增加升力。 为了产生比较小的抵抗力，物体的前面应该做圆一点，而且身体应该逐渐地从中央部分逐渐变小地往后弯。 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 23页 流线型化减小了大量由机翼产生的阻力 迎角 迎角是飞机的纵轴和翼弦线之间的夹角。 迎角是按照一定的角度把机翼固定在机身上。 它是飞机的弦和飞机的纵轴形成的角度。飞机的这条纵轴是通过从飞机的前面到飞机的后面的机身想像的线。 通常，迎角是在机翼和飞机纵轴之角度。 飞机舵面 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 24页 方向舵，升降舵和副翼在一架飞机上是主要的控制面。 方向舵控制飞机的首摇 ,升降舵控制它的纵摇 ,副翼控制它的滚动。其它在下面被说明。 襟翼是机翼可动的部分，通常铰接在每个机翼靠近机身的后缘。 飞行员扩展而且缩回襟翼。 扩展 襟翼增加翼弧形和翼的攻击的角度。 这可以增加机翼的升力也可以增加阻力。襟翼使飞行员能够作较险竣的降落当着陆时没有增加的气流速度。 他们也帮助飞机短距离起飞。 有许多不同类型的襟翼。一些铰链式，一些下滑式 , 一些开缝式 , 和即使在大的攻击角度被试飞时也能使一些气流平稳流过机翼。 前缘缝翼是机翼前缘的凸起部分。 他们增加翼的升力。前缘缝翼和襟翼一起运作维持机翼上面的层流 (一个平滑的气流 )。 扰流板减小升力。扰流板沿着翼的顶端的。 当他们没有在被用的时候 , 他们适宜的装进或埋在机翼的表面。 当他们被用的时候 ，他们从翼的表面伸到气流中破坏层流。扰流板的大小不同取决于要干扰多少的升力 ,不同的扰流板的设计是依照不同类型的飞机，但它们的功能是相同的。 有些装置只减小阻力而不影响机翼的升力。 这些包括减速板 , 空气动力减速装置，俯冲减速板或减速伞。 他们可能位于后缘或者可能从机身凸出。 这些装置允许非常险峻的降落和气流速度的迅速改变。 飞行员能用缩回装置即时停止他们的作用。 南昌航院 2006 届毕业设计 飞机前起落架机构设计 共 30 页 第 25页 一架飞机有旋转的三个轴 : 垂直的 , 横向的 , 和纵向的。 除了飞机向前运动外，飞机用三个力（升力，阻力和边的力量）可以作绕三个轴的运动。这三根轴能被看成穿国飞机的三根杆，每根与另外二根相交。 交点就是飞机的重心。 每一个轴与另外二根又垂直。 经过头和尾部纵向扩充的线叫做纵轴。 绕着这根轴旋转叫做横滚。 阻力是沿着这跟轴的力 , 但是在航线的相反方向。 从一边翼尖到另一翼尖轴被称为横轴。 绕着这