What Makes An Airplane Fly

GENERAL

This is just the basic informations for the beginners which did not know any things about the aircraft or airplane before and wants to know some principles that why the airplane can fly but not in deep details. For the people that want to know more than what I have in here, please go to the text book which have many professors wrote them and the details about the airplane have so much to put it all in the WEB.

INTRODUCTION

It was , of couse, the birds who were responsible for the whole complicated story and business. A man with the brain of a scientist began to think seriouly about attainment of the dream. This was Leonado da Vinci (1452-1519), whose detail study of bird flight nevertheless led him to the erroneous conclusion that man’s muscular power, so superior to that of the birds, should enable him to fly in a properly constructed ornithopter,or flapping-wing aircraft.

In 1680, Giovanni Alphonso Borelli’s has a result of his detailed study of bird flight, man did not have the power output needed to lift himself and a machine into the air. This brought an end to practically all heavier-than-air experiments until nineteenth century.

On October 15, 1783, Jean-Francois had made a flight in a Mongolfier hot-air balloon tethered flight for 4 minutes 24 second. Lessthan two month later a hydrogen-filled balloon had completed a successful two-hours free flight.

German Otto Lilienthal(1848-1896), whose graceful and beautifully-constructed hang-gliders enable him to become the first man in the world to fly confidently and regularly, total more than 2000 flights.He did not develop control surfaces for his gliders, but rely on body movements to provide limited control in the three axes of pitch, yaw, and roll. He lost his life at age of 48 on 10 August 1896 due to one of his gliders stalled and crashed to the ground. The persons who pioneer of the gliders were Otto Lilienthal (German), Percy Pilcher (England) He also lost his life in a glider clashed three years after Lilienthal, and Octave Chanute (American)(1832-1910)

Wilbur (1867-1912) and Orville (1871-1948) Wright, had been interested in the possibility of mechanical flight in the early years. By 1900, they became freinds with Chanute . Chanute encouraged , providing information, and directly assisted the Wrights to achieve their goal of power flight later.First flight they flied the flyer was on 17 December 1903.This is generally accepted as the first man to accomplised the dream.Eventhrough there are some controversy over the first powered aircraft.

Alberto Santos-Dumont a little brazilian living in France. During 1906, with his No.14-bis which was power by a 50 horsepower Antoinette engine, he made a first flight of 60 meter at Bagattelle, Paris on 23 October 1906. Some people believed that Santos-Dumont really had made the first power flight in history.

NOMENCLATURE or TECHNICAL TERM

Although we will describe certain terms or parts of airplane more in the next sections as we go along, but we should familier with all of these terms in order to understand the airplane better.

ctrl surface

Aerodynamics : Aero is derived from the Greek word meaning AIR, and Dynamics comes from the Greek word meaning Power, or branch of physics which considers bodies in motion and the forces that produce or change such motion. When Aero is combined with Dynamics ,we have Aerodynamics,Meaning ” The science relating to the effects produced by air or other gases in motion”.

Air Currents : are movement of the air with respect to the earth. If the air is rising from the earth , it is called a Vertical Current

Relative Motion : Motion is a movement.If an object changes it position,it is in motion. Relative Motion defined as an object which has moved or has changed its position with Respect to some other object. An Airplane must have Relative motion between Airplane and the Air in order to fly.The velocity of this motion is called the True Airspeed

Bernoulli’principle : This principle states that as the air velocity increases, the pressure decreases; and as the velocity decreases, the pressure increases

Airfoil : is technically defined as any surface, such as an airplane aileron, elevator, rudder, or wing, designed to obtain reaction from the air through which it moves.

airfoil

Angle of Attack : is the acute angle measured between the chord of an airfoil and the relative wind.

Cockpit : is the pilot’s compartment which is seperated from the rest of the cabin.

Control Stick or Control Column : A vertical lever or column by mean of which the pilot operates the longitudinal and lateral control surfaces of the airplane. The elevator is operated by fore-and-aft movement of the stick or column, and ailerons are moved by sideways movement of the stick or turn the wheel to left or right.

ctrl.column

Aileron : One of a pair of movable control surfaces attached to the trailing edge of each wing tip, the purpose of which is to control the airplane in roll by creating unequal or opposing lifting forces on the opposite sides of the airplane.

Elevator : A movable auxiliary airfoil or control surface designed to impress a pitching movement on the airplane, that is, to cause rotation about the lateral axis.

Flap : A hinged, pivoted, or sliding airfoil or plate, normally located at the trailing edge of a wing, extended or deflected to increase the lift and/or drag, generally used at takeoff and landing.

Rudder : A hinged or movable auxiliary airfoil used to impress a yawing moment on the aircraft.

Rudder Pedal : Either one of a pair of cockpit pedals for operating a rudder or other directional control device. The pedals are on the floor and feet operated.

Stabilizer : A fixed or adjustable airfoil or vane that provides stability for an aircraft.

HISTORY of FLIGHT
Ornithopters (Flapping- wing)

The beauty and freedom of birds has always drawn our admiration and envy. The freedom to move in any direction over all obstacles is a capability that all of us would enjoy. early attempts to defy gravity involved the invention of machines, such as Ornithopters.

frosts

This type of flying machine utilizes the flapping of the wings in order to achieve flight. Needless, is to say that all attempts to fly using this type of machine failed.

Machine lighter-than-air

In the year between 1650 and 1900 , there was a second attempt at flying with a less sophisticated but more efficient generation of flying machines, the lighter-than-air craft. The idea of filling a closed container with a substance that normally rises through the atmosphere was known as early as the thirteen century. Over a five hundred year span, different substances came to be known as being lighter-than-air. The most common gas proposed was water vapor, helium and hydrogen. The first successful attempts at achiveing flight using his type of crafts were made by the Montgolfier brothers in France. Their most successful attempt was in 1783.

The most successful builder of this type of lighter-than-air craft was Count Ferdinand von Zeppelin (picture above) . In the early 1930’s the German Graft Zeppelin machine was able to make a Trans-Atlantic flight to the United States. The large Hidenburg was equally successful until it was destroyed by fire while attempting a landing in 1937 at Lakehurst,New Jersey.

Orville and Wilbur Wright

In the early 1900s two American brothers, Orville and Wilbur Wright from Dayton, Ohio began to experiment with gliders. The gliders were built using data from Otto Lilienthal in Europe. Most of these flights turn out to be a failure. In 1901, they decided to gather their own wing data by conducting systematic experiment on different type of wing configurations. In 1902, Glider has wingtip to wingtip measurement of 32 ft. and wing width of 5 ft. This was the first aircraft with three-axis control. This mean that the aircraft could go up or down, left or right, and could also roll about its longitudinal axis. At Kitty Hawk, they perform over 800 flights, the early problem of aircraft were solved .

The Wright brothers, now confident about their ability to flight, decided to turn their attention to power. In 1903, after redesigning the airframe of their 1902 glider, the Kitty Hawk Flyer was born. In December 17 , 1903 , with this aircraft, Orville and Wilbur Wright demanstrated the flight of self powered aircraft.
Following the Wright Brothers success, the aeronautical activity took place basically everywhere in the world.

Bleriot XI Monoplane
bleriot

The future potential of the airplane was realized when Louis Bleriot (France) flew his XI monoplane across the Einglish Channel in 1909. This was made Britain could no longer feel secure because England rely only on the royal navy.

Henri Fabre Seaplane

The first Seaplane was built and flown by Henri Fabre (France) in 1910 at Martigues, France. The great pioneer of marine flying was Glen Curtiss of the United States. In 1911 he fitted floats to his pusher biplanes and flow it off the water.

fabre5

First flight of a seaplane called a Hydravion was created by Frenchman Henri Fabre. Using a 50 horsepower Gnome rotary engine, Fabre flew 1650 feet on water (March 28, 1910).

Vikers Gunbus:
gunbus

Until 1914 , As the war progressed, the manufacturers were pressed to equip airplanes with guns, bombs and torpedos. This Vicker Gunbus (England) had been accomplished by 1914.

F.X. Trimotor:
trimotor

From the United States, Ford Trimotor is the world’s first airline services were in 1910. With the advances in aircraft designed brought about by war, the enclosed cabin airplane became the standard for commercial airline travel by the early 1920’s.

As the time went by, the speed of airplanes began to increase. From the famous 12 mph top-speed of Wright Brithers Kitty Hawk Flyer , until in 1947, a test pilot named Chuck Yeager flied exceeded the speed of sound. From that point on a series of experimental supersonic aircraft took to the sky breaking speed record after speed record. Today we still can see some of supersonic aircrafts that were built in the 1960’s like Concorde(mach 2), TU-144 (mach 2.2), SR-71 Blackbird (mach 3).

PRINCIPLES
Forces Acting on An Airplane

There are four forces acting on the airplane all the time during airplane is flying.The four forces are
(1) Lift, (2) Gravity force or Weight, (3) Thrust, and (4) Drag.
Lift and Drag are considered aerodynamics forces because they exist due to the movement of the Airplane through the Air.

four forces

Lift: is produced by a lower pressure created on the upper surface of an airplane’s wings compared to the pressure on the wing’s lower surfaces,causing the wing to be LIFTED upward. The special shape of the airplane wing (airfoil) is designed so that air flowing over it will have to travel a greater distance and faster resulting in a lower pressure area (see illustration) thus lifting the wing upward. Lift is that force which opposes the force of gravity (or weight).

lift

Lift depends upon (1) shape of the airfoil (2) the angle of attack (3) the area of the surface exposed to the airstream (4) the square of the air speed (5) the air density.

lift equation

Weight: The weight acts vertically downward from the center of gravity (CG) of the airplane.

Thrust: is defined as the forward direction pushing or pulling force developed by aircraft engine . This includes reciprocating engines , turbojet engines, turboprop engines.

thrust equation

Drag: is the force which opposes the forward motion of airplane. specifically, drag is a retarding force acting upon a body in motion through a fluid, parallel to the direction of motion of a body. It is the friction of the air as it meets and passes over an airplane and its components. Drag is created by air impact force, skin friction, and displacement of the air.

drag equation
Aircraft Flight Control

An airplane is equipped with certain fixed and movable surfaces or airfoil which provide for stability and control during flight. These are illustrated in the picture.

Flight Control

Each of the named of the airfoil is designed to perform a specific function in the flight of the airplane. The fixed airfoils are the wings, the vertical stabilizer, and the horizontal stabilizer. The movable airfiols called control surfaces, are the ailerons, elevators, rudders and flaps.The ailerons, elevators, and rudders are used to “steer” the airplane in flight to make it go where the pilot wishes it to go. The flaps are normally used only during landings and extends some during takeoff.

Aileron: may be defined as a movable control surface attached to the trailing edge of a wing to control an airplane in the roll, that is , rotation about the longitudinal axis.

Elevator: is defined as a horizontal control surface, usually attached to the trailing edge of horizontal stabilizer of an airplane, designed to apply a pitching movement to the airplane. A pitching movement is a force tending to rotate the airplane about the lateral axis,that is nose up or nose down.

Rudder: is a vertical control surface usually hinged to the tail post aft of the vertical stabilizer and designed to apply yawing movement to the airplane, that is to make it turn to the right or left about the vertical axis.

flap

Wing Flaps: are hinged or sliding surfaces mounted at the trailing edge of wings and designed to increase the camber of the wings. The effect is to increase the lift of the wings.

FLIGHT DIRECTIONAL CONTROL
THE AXES OF ROTATION

An airplane has three axes of rotation, namely , the longitudinal axis, the vertical axis, and the lateral axis. see figure below and you will understand what we mean. The simplest way to understand the axes is to think of them as long rods passing through the aircraft where each will intersect the other two. At this point of intersection, called the center of gravity.

axis

The Axis that extends lengthwise (nose through tail) is call the longitudinal axis, and the rotation about this axis is called “Roll”

The axis that extends crosswise (wing tip through wing tip) is called the lateral axis, and rotation about this axis is called “Pitch”

The axis that passes vertically through the center of gravity (when the aircraft is in level flight ) is called the vertical axis, and rotation about this axis is called “Yaw”

The Longitudinal Axis:
roll

The Axis Running from the nose to the tail of an aircraft is the longitudinal axis (see picture above). The movement around the longitudinal axis is called roll. The cause of movement or roll about the axis is the action of the ailerons. Ailerons are attached to the wing and control through the control column in a manner that ensures one aileron will deflect downward when the other is deflected upward.

When an aileron is not in perfect alignment with the total wing, it changes the wing’s lift characteristics.To make a wing move upward, the aileron on that wing must move downward. The wing that has aileron downward produce more lift on that wing. the wing that has the aileron upward will reduce lift on that wing . This cause the aircraft to roll.

The ailerons are attached to the cockpit control column by mechanical linkage. When the control wheel is turned to the right (or the stick is move to the right ), the aileron on the right wing is raised and the aileron on the left wing is lowered. This action increases the lift on the left wing and decreases the lift on the right wing, thus causing the aircraft to roll to the right. Moving the control wheel or stick to the left reverses this and causes the aircraft to roll to the left. See Roll Action Animation Click Here

The Lateral Axis
pitch

The lateral axis runs from wingtip to wingtip.The movement around the lateral axis is called pitch.What causes this pitching movement ?. It is the elevator which is attached to the horizontal stabilizer. The elevator can be deflected up or down as the pilot moves the control column (or stick) backward or foreward.

Movement backward on the control column moves the elevator upward. (see picture above) The relative wind (RW) striking the top surface of the raised elevator pushes the tail downward. This motion is around the lateral axis, as the tail moves (pitches) downward, the nose moves (pitches) upward and the aircraft climbs.

Movement forward on the control column moves the elevator downward . The relative wind (RW) striking the lower surface of the elevator causes the tail to pitch up and the nose of the aircraft downward causing the airplane to dives. See Pitch Action Animation Click Here

The Vertical Axis:
yaw

The third axis which passes through from the top of the aircraft to the bottom is called the vertical or yaw axis. The aircraft’s nose moves about this axis in a side-to-side direction. The airplane’s rudder, which is moved by pressing on the rudder pedals which are on the floor. The airplane’s rudder is responsible for movement about this axis.The rudder is a movable control surface attached to the vertical fin of the tail assembly. By pressing the proper rudder pedal, right pedal moves the rudder to the right, and left pedal moves the rudder to the left, when pilot press the left rudder pedal, that mean the pilot sets the rudder so that it defects the relative wind to the left. This then creates a force on the tail, causing it to move to the right and the nose of the aircraft to yaw to the left.

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