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Aerodynamics. The Atmosphere. 78% Nitrogen and 21% Oxygen Remaining 1% consists of other gases primarily Argon and Carbon Dioxide. Standard Atmosphere. Standard Atmospheric Conditions (Standard Day Conditions). All data considered to be at “sea level” or zero feet altitude.
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The Atmosphere • 78% Nitrogen and 21% Oxygen • Remaining 1% consists of other gases primarily Argon and Carbon Dioxide
Standard Atmospheric Conditions(Standard Day Conditions) • All data considered to be at “sea level” or zero feet altitude. • Temperature is 15 Celsius or 59 Fahrenheit • Barometric pressure of 29.92 inches of mercury or 1013.2 milibars. • Every 1000 feet of altitude change is considered to have a decrease of 1 inch of mercury pressure and temperature drop of 2 degrees Celsius or 3.5 degrees Fahrenheit
Pressure • Everything on the earths surface is under pressure due to the weight of the atmosphere. • Think of it the same way as the pressure you feel under water.
Pounds Per Square Inch • The force in pounds that the air exerts on each square inch of area. Atmospheric=14.7 PSI
Inches of Mercury • Standard atmospheric pressure can support a column of mercury 29.9 inches tall.
Millibar • The metric unit of measure for barometric pressure is millibars. One millibar is approximately equivalent to .0295 In Hg. Therefore standard sea level pressure equals 1013.2 millibars.
Temperature • Celsius Scale- Has 100 divisions between boiling points of water. • Fahrenheit- Water freezes at 32 degrees and water boils at 212 degrees. Standard Day Conditions= • 15 Celsius or 59 Fahrenheit
Air Density • Pressure and Temperature determine density. • Density Altitude On a day where when atmospheric pressure is higher than a standard and the temperature is lower than standard, the standard air density at 10 000 feet might occur at 12 000 feet.
Humidity • Air is seldom completely dry and will always contain some water or moisture. • Fog and Humidity both affect performance of an aircraft. Since humid air is less dense than dry air the allowable weight of an aircraft is generally reduced. • Humid Air is lighter than Dry Air
Absolute Humidity • Is the actual amount of water vapor in a mixture of air and water. • The higher the air temperature the more water vapor the air can hold.
Relative Humidity • The ratio between the amount of moisture in the air to the amount that would be present if the air was saturated (dewpoint).
Dewpoint • Is the temperature at which air reaches a state where is can hold no more water. • When the dewpoint is reached the air contains 100% of the water it can hold.
The Fuselage • Common attaching point (wings etc.) • Houses the cockpit, flight crew, passengers, cargo.
The Wing • Used to produce lift. • The wings usually have ailerons and flaps.
Ailerons • Ailerons move in opposite directions. Ailerons control roll of the aircraft.
Flaps • Flaps control the wings chord line and camber. It is used to increase or decrease a wings surface area for take off or landing.
The Empennage • The Empennage consists of the vertical stabilizer (fin), horizontal stabilizer, elevator and rudder.
Stabilator • This type of design requires no elevator. This design pivots up and down to control the aircrafts pitch.
Ruddervators • Combination of a rudder and elevator.
Trim Controls • Used to provide small moveable portions of the trailing edge of a control surface and used to create an aerodynamic force that deflects the control surface. They can be controlled by the pilot or fixed.
Four Forces of Flight • Lift-Force that opposes flight. • Weight-Force that opposes lift (gravity). • Thrust-Forward force which propels the aircraft. • Drag-Force that opposes thrust.
Lift Theory Newton's laws: lift and the deflection of the flow Deflection • Airstreams around an airfoil in a wind tunnel. Note the curved streamlines above and below the foil, and the overall downward deflection of the air. • One way to understand the generation of lift is to observe that the air is deflected as it passes the airfoil. Since the foil must exert a force on the air to change its direction, the air must exert a force of equal magnitude but opposite direction on the foil. In the case of an airplane wing, the wing exerts a downward force on the air and the air exerts an upward force on the wing. • This explanation relies on the second and third of Newton's laws of motion: The net force on an object is equal to its rate of momentum change, and: To every action there is an equal and opposite reaction. • Another way to describe deflection is to say that the air "turns" as it passes the airfoil and follows a path that is curved. When airflow changes direction, a force is generated. Pressure differences • Lift may also be described in terms of air pressure: pressure is the normal force per unit area. Wherever there is net force there is also a pressure difference, thus deflection/flow turning indicates the presence of a net force and a pressure difference. This pressure difference implies the average pressure on the upper surface of the wing is lower than the average pressure on the underside
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
Bernoulli’s Principle • As the velocity of a fluid increases, its internal pressure decreases. • As velocity of a fluid decreases, its internal pressure increases. Convergent Passage V- P- Divergent Passage V- P-
Wingtip Vortices • Cause by the air beneath the wing rolling up and around the wingtip.
Winglets • A device added to the wing tips to smooth the out and remove that turbulence or vortices.
The Airfoil • Is any surface, such as a wing, propeller, compressor blade that provides an aerodynamic force when it interacts with a moving stream of air.
