The Airfoil Top Leading edge Trailing edge Bottom Airfoil Characteristics Rounded Leading Edge – to split the air Sharp Trailing Edge – to reduce turbulence Flat Bottom Declining Top
Air Flow Air flow is caused by both: 1. the motion of the wing moving forward and 2. natural wind The air is split in half where it meets the leading edge The air recombines at the trailing edge Air on top of the airfoil moves faster than air on the bottom , but why?
Venturi Effect The effect of compressing fluids As a fluid (air) is compressed it moves faster
Half a Venturi So the air on top of the air foil moves FASTER The asymetric shape of the air foil causes the air on top to be compressed while the air on the bottom is hardly moved
Why is this important? Bernoulli’s Principle: The pressure air exerts as it moves decreases as the speed of the air increases
The faster I make my airfoil go, the more I decrease the air pressure on top of my airfoil
How does this help? Pressure on top and bottom are equal Aircraft on the ground Pressure on top is less than pressure on bottom Aircraft moving forward Lift
Calculating Lift L = (1/2) d v2 s CL • L = Lift, which must equal the airplane's weight in pounds • d = density of the air. This will change due to altitude. These values can be found in a I.C.A.O. Standard Atmosphere Table. • v = velocity of an aircraft expressed in feet per second • s = the wing area of an aircraft in square feet • CL = Coefficient of lift , which is determined by the type of airfoil and angle of attack. Which parts does the pilot control??? Velocity (speed) and Density (altitude)
How can I use this when flying? Imagine you are flying and you are having trouble keeping the aircraft from losing altitude. What should you do?
Things to know Lift is always perpendicular to the wing (airfoil) Ground
Things to know • Lift must equal aircraft total weight for aircraft to fly level • Weight exceeds Lift will cause aircraft to descend • Lift exceeds weight will cause aircraft to climb
Explore • If you were an aircraft designer how would you design an airfoil for: • A passenger airliner • A fighter
Memory Check What is the Venturi effect?
Memory Check Where does the Venturi effect occur on the Airfoil?
Memory Check Describe the sequence of events that leads to lift using a thinking map
How lift is created Bernoulli Venturi Aircraft moves forward Air moves around wing Air on top compresses Air on top moves faster Air pressure on top decreases Pressure differences create lift