Air consists of 77% Nitrogen and 21% Oxygen, and other substances like water vapor and other gases. This mixture surrounds the earth’s atmosphere. You might be asking why this gas mixture doesn’t just float of into space. The answer is gravity. Gas is made up of matter, It has mass thus weight is a factor that holds it to Earth. Close to sea level the pressure is approx 14.7 pounds per sq inch. This is occurs because air has weight. Air in the atmosphere is stacked one on top another. If you stack one book on top another on a table you note that the wight on that table increases. A similar situation occurs in nature. When air is stacked on top another the effect of that action is weight. That weight shows up as pressure. Pressure is Force measured in terms of its distribution over an area of opposing force. The pressure decreases as altitude increases. This happens because when you get higher and higher in the atmosphere there is less and less air pushing on top of you.
We know for a fact that air has mass, density and weight. So what? Is there any way to use this to our advantage? The answer is yes, we can use density as an advantage in Hot air Balloon, and Pressure as an advantage using an airfoil (What is an airfoil? An airplane wing has a special shape called an airfoil. As a wing moves through air, the air is split and passes above and below the wing. The wing’s upper surface is shaped so the air rushing over the top speeds up and stretches out. This decreases the air pressure above the wing. The air flowing below the wing moves in a straighter line, so its speed and air pressure remains the same. Since high air pressure always moves toward low air pressure, the air below the wing pushes upward toward the air above the wing. The wing is in the middle, and the whole wing is “lifted.” The faster an airplane moves, the more lift there is. And when the force of lift is greater than the force of gravity, the airplane is able to fly.). It is known that air decreases in density as the temperature increases. The air expands and takes up more space Due to the increase in kinetic energy the molecules move further apart. When the air is expanded with the same amount of volume it is in fact lighter. This is where they come up with a name of lighter then air vehicles” This is the basis of Archimedes’ Principal.
Bernoulli’s Principal :
An airfoil uses Bernoulli’s Principal to create lift. This principal states as speed of the air increases the pressure decreases. If you have noticed, an airfoil has a special shape to it. The upper part of the shape is curved instead of flat. This curve increases the surface distance on top of the shape from front to back. When this foil travels air passes over the top and the bottom. The air when it travels over the top has more of a distance to travel, then the air on the bottom. For this reason the air on the top travels faster to “catch up” to the air on the bottom. According to Bernoulli’s Principal as air “speeds up” the pressure decreases. Now we got a low pressure area on top and a relatively high pressure area in the bottom. In effect the area on the bottom pushes up and creates lift.
The major sections of an aircraft include the Wings, Fuselage(The fuselage (from the French fuselé “spindle-shaped”) is an aircraft‘s main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull. The fuselage also serves to position control and stabilization surfaces in specific relationships to lifting surfaces, required for aircraft stability and maneuverability), and Engines.
The wings are used to create lift; Fuselage is one of the main structural components of the aircraft. It is used to hold cargo, or passengers. The engines are used to create thrust which actually moves the aircraft in a specific direction. This is a basic description of what each component does. Each component is going to be described in detail as follows.
The primary purpose of wings is to create lift. It opposes the force of weight on the aircraft. Wings are shaped like airfoils they create a low pressure area over the wing which makes the air below the wing to “push” the wing up. There are different shapes airfoils could be shaped. One is Symmetrical, and the other is semi-symmetrical. The semi-symmetrical creates lift at a relatively low angle of attack compared to the symmetrical. The advantage of using the symmetrical is that you can fly the aircraft right side up and upside down. The wing would not notice any difference. This kind of airfoil shape is used frequently in Acrobatic flying for air shows etc…
Engines are primarily used to produce one of the forces called thrust. There are two major types of engines, Reciprocating engines, and Gas Turbine engines commonly known as “Jets”. These two types of engines have advantages and disadvantages. Those will be discussed later on.. Reciprocating engines are basically piston engines. The inspiration of using piston engines on aircraft came from automobiles. The Wright Brothers used what was basically a modified automobile engine used on their first aircraft. It was a 4 cylinder gasoline engine that weighed a mere 180 pounds. It generated about 13 horse power. Piston engines were the first type of engines used widely in the early years of aviation. World War I and World War II greatly help improve engine technology. Because of the war many automobile manufactures like Rolls-Royce, Mercedes and Hispano- Suiza started producing aircraft engines of horsepower. By the end of WWII monstrous 28 Cylinders engines had and the ability to produce 3500 horse power.
Towards the end of WWII the new jet era was just beginning. The Germans introduced the Messerschmitt 262 thundered into combat at 540 miles per hour. This aircraft went 70 miles per hour faster then its propeller-driven opponent. The introduction of this plane was too late in the war to help the Germans win. However this aircraft brought jet technology to the modern age.
The actions of jet engines are as follows. Air surrounding the engine enters, it is compressed, mixed with Fuel, and ignited. When the fuel burns it expands and exits through the rear. This can be illustrated by the actions of a balloon.
The jet engine works on the principal of Action Reaction theory devised by Isaac Newton. It was set as a basic law of physics in the 17th Century. It States “For every action there is an equal and opposite reaction”
Jet technology improved the power and performance of an aircraft that used them. But in the early days it was at the cost of fuel. The early jet engines were not very fuel efficient. But later models improved in fuel efficiency greatly.
Propellers are similar in shape to an airfoil. The primary job of a propeller is to convert horse power (Usually Called “Brake Horse power
<< BHP = Flow(GPM) X TDH(FT) x SG /3960xEFFICIENCY(%)Example: BHP = (100 GPM) x (95 Ft) x (1.0) / 3960 x .6BHP = 4.0 >>”) from an engine crankshaft into thrust. Like an airfoil a propeller creates lift by using the curved area and flat area. While spinning the propeller creates lift forward similar to an airfoil creating lift upward. This action “pulls” the aircraft forward.
There are 3 different axes that an aircraft must be stable in order to fly. There has to be Directional, Lateral, and longitudinal stability. In order to keep all these axis in control there are different parts of aircraft that handle different axis.
Vertical: The vertical tail fin controls Directional Stability. This movement is called “yawing”.
Lateral : Lateral stability is controlled by a special wing shape called the dihedral. This is when the wings are slightly shaped upward similar to a slight “V” shape. This prevents the aircraft from rolling. If rolling occurs the angle of attack of the wing that is going down will increase, and the wing will be pushed upward until the aircraft is level. This is same with the other wing.
Longitudinal : Longitudinal stability prevents the aircraft from doing dips or nose-ups. The part of the airplane that holds longitudinal stability is the horizontal stabilizer.
Drag is a force opposing thrust. It attempts to pull the aircraft back in flight. When airflow is disrupted over an area it produces drag. All moving objects that move through air or water create drag, the bigger they are the more drag they produce. Scientists have been working on reducing drag as aircraft get bigger and faster. One way they found to reduce drag is to streamline the aircraft. The object of streamlining is to reduce the amount of air that has to be moved in order for the aircraft to pass through a column of air.
Lift is a force that is produced by the wings on the aircraft. This is produced by the action of the airfoil. This force fights a battle with gravity, the force pulling downwards. A wind produced less lift as the aircraft goes slower while landing. Different wing shapes produce different results. New wing designs are researched everyday in wind tunnel all across the United States. There is a way to increase the amount of lift a wing produces. The wing has to increase its surface area, by installing flaps into the design of the wing. While landing or slow flying these flaps come down to increase the wing area. The disadvantage to this method is an increase in drag.
Gravity is the force pulling the aircraft downward towards the ground. This force increases as weight increases. Weight is an important factor in the construction and loading of aircraft. There is a limit to how much lift an aircraft wing produces and it has to be greater than the weight or the aircraft would not take off.
Thrust is a force that is produced by the engine of the aircraft commonly called the power plant. This force fights a battle with drag, and propels the aircraft. Thrust can be produced by different types of engines. Jets, piston engines are the most common.
PROBLEMS FACING FLIGHT:
Drag is one of the biggest problems facing aircraft. As Aircraft get bigger and faster they tend to produce more drag as they move through the air. Engineers today are researching new shapes that reduce the amounts of drag on an aircraft. One way is to reduce skin friction, is to have a smooth and polished surface in which air can pass over. The more smoother and more polished the craft’s surface is the more easily the air can flow past it.
Weight and balance is an important factor in today aircraft. If you try to balance a ruler in your hand you notice that you have to place your finger somewhere in the center because that is where the center of gravity is. The center of gravity is a point where the weight of both sides is equal. If you hold something at the center of gravity, it will be totally balanced. Well the center of gravity is used similarly with aircraft.
The center of gravity on an aircraft is located close to the wing area. At this point everything is balanced. There is a range marked on aircraft where the center of gravity has to lie in. It is usually specified using the datum line as a reference. The Datum line is a set point where all measurements are taken from. If the center of gravity is out of range the aircraft becomes more and more difficult to control. It reaches the point where the aircraft can not stay in air. Balancing the aircraft takes place when there is an alteration on the craft. For example if a seat is taken out or if new radio equipment is installed.
MANEUVERING USING MECHANICAL POWER
Mechanical power is mostly used on small aircraft. It uses steel cables that run from the control surface to the control device. When the pilot moves the controls the force is directly converted from the control device into movement on the control surface. Because of the weight of the control surface or the resistance of the air, faster larger aircraft require a little more power to move their control surfaces. This is where the use of the hydraulic power or Fly by wire technology helps.
MANEUVERING USING HYDRAULIC POWER
Mechanical links similar to the ones used on smaller aircraft run into a hydraulic control device. This device is known as a selector valve. This valve controls fluid going in and out of actuators. These actuators are simply a piston inside a cylinder. The movement of the piston controls the movement of the flight surface of the aircraft.
FLY BY WIRE TECHNOLOGY
Fly by wire technology is the recent development in technology. This is the most advanced control system being used currently. This system uses electronic impulses to convey the pilot’s commands. From there the commands are then sent to an onboard flight computer which converts the digital information to the hydraulic system or electric motors which move the control surface. This system is used in some of the military aircraft like the [[F-16, A320, X-29]]
Before an airplane can take off there are things that have to be done for flight preparation. For a big airliner this means flight planning, Weather, fuel load, [[weight and balance]]. After that is done there is a checklist in which the pilot has to complete in order to be airborne. Such things as Electronic, hydraulic, pneumatic, pressurization, control, instrument, radio, navigational systems all have to be checked. Soon after checklists for engine starting are followed. All this goes on until the aircraft finally reaches the runway where it is going to take off.
An artificial horizon is kept horizontal by the gyroscope to which it is mounted. A fixed bar represents the plane’s wings. As the plane climbs or dives, the bar rises above or below the horizon line. When the plane banks, the bar banks accordingly.
This gauge is connected to a pressure sensing tube and a flexible diaphragm with in the instrument case. The diaphragm compares the difference between the static air pressure on the tube and the oncoming air, called ram pressure. An internal lever system translates this into airspeed, expressed in nautical miles per hour, or knots.
Vertical Speed indicator :
The vertical speed indicator shows the rate at which the airplane is climbing or descending. The instrument case contains an airtight compartment housing a diaphragm. The case and the diaphragm compartment each connect to the plane’s static pressure system, and it can register two different pressures. In level flight, the two pressures are equal and the needle points to zero. As the plane ascends, the diaphragm pressure drops faster than the case pressure and the relative difference translates into the aircraft’s rate of climb.
Turn and bank Indicator :
This is an instrument that has a ball which is in a sealed glass tube filled with kerosene. When an aircraft turns the ball inside the tube will move towards the direction of the turn. If the ball is centered that means the plane is balanced. if the ball rolls away from the turn that means the aircraft is yawing.
This instrument is similar to a compass. The compass remains steady in relation to the earth.
The altimeter works similar to a barometer, it senses the decrease in air pressure that accompanies an increase in altitude. The needle indicates the altitude over sea or wherever the aircraft is flying over ground. This instrument has to adjusted almost every flight because of changes in weather.