1. Airplanes 1 Airplanes

2. Airplanes 2 Introductory Question As you ride in a jet airplane, the clouds are passing you at 600 mph. The air just in front of one of the huge jet engine intake ducts is traveling As you ride in a jet airplane, the clouds are passing you at 600 mph. The air just in front of one of the huge jet engine intake ducts is traveling A. much faster than 600 mph. B. much slower than 600 mph. C. about 600 mph.

3. Airplanes 3 Observations about Airplanes Airplanes support themselves in the air Airplanes support themselves in the air Airplanes seem to follow their tilt, up or down Airplanes seem to follow their tilt, up or down Airplanes need airspeed to fly Airplanes need airspeed to fly Airplanes can rise only so quickly Airplanes can rise only so quickly Airplane wings often change shape in flight Airplane wings often change shape in flight Airplanes have various propulsion systems Airplanes have various propulsion systems

4. Airplanes 4 5 Questions about Airplanes How does an airplane support itself in the air? How does an airplane support itself in the air? How does the airplane “lift off” the runway? How does the airplane “lift off” the runway? Why does plane tilt up to rise, down to descend? Why does plane tilt up to rise, down to descend? Why are there different wing shapes? Why are there different wing shapes? How does a plane propel itself through the air? How does a plane propel itself through the air?

5. Airplanes 5 Question 1 How does an airplane support itself in the air? How does an airplane support itself in the air? What pushes up on airplane to balance its weight? What pushes up on airplane to balance its weight? What does it do with the momentum gravity gives it? What does it do with the momentum gravity gives it?

6. Airplanes 6 Using a Wing to Obtain Lift (part 1) As air flows under a wing, As air flows under a wing, air bends away from the wing air bends away from the wing air’s pressure rises, speed drops air’s pressure rises, speed drops As air flows over the wing, As air flows over the wing, air bends toward the wing air bends toward the wing air’s pressure drops, speed rises air’s pressure drops, speed rises

7. Airplanes 7 Using a Wing to Obtain Lift (part 2) The wing experiences The wing experiences a strong upward lift force a strong upward lift force a small downstream drag force a small downstream drag force Wing pushes air down, air pushes wing up! Wing pushes air down, air pushes wing up! Downward momentum is transferred from Downward momentum is transferred from the earth to the airplane by gravity the earth to the airplane by gravity the airplane to the air by lift forces the airplane to the air by lift forces from the air to the earth by pressure on the ground from the air to the earth by pressure on the ground

8. Airplanes 8 Question 2 How does the airplane “lift off” the runway? How does the airplane “lift off” the runway? How does the pilot initiate the rise? How does the pilot initiate the rise? How is landing different from takeoff? How is landing different from takeoff?

9. Airplanes 9 At Take-Off As a wing starts moving in air As a wing starts moving in air the airflow is symmetric the airflow is symmetric and the wing experiences no lift and the wing experiences no lift However, this airflow is However, this airflow is unstable at trailing edge bend unstable at trailing edge bend and the wing sheds a vortex and the wing sheds a vortex After the vortex leaves, the wing has lift After the vortex leaves, the wing has lift

10. Airplanes 10 Question 3 Why does plane tilt up to rise, down to descend? Why does plane tilt up to rise, down to descend? Does a plane always go in the direction it’s pointed? Does a plane always go in the direction it’s pointed? How can plane land if its nose is higher than its tail? How can plane land if its nose is higher than its tail?

11. Airplanes 11 Angle of Attack A wing’s lift depends on A wing’s lift depends on the shape of its airfoil the shape of its airfoil and on its angle of attack–its tilt relative to the wind and on its angle of attack–its tilt relative to the wind Tilting an airplane’s wings Tilting an airplane’s wings changes the net force on the airplane changes the net force on the airplane and can make the airplane accelerate up or down and can make the airplane accelerate up or down but usually requires tilting the airplane’s fuselage but usually requires tilting the airplane’s fuselage Plane’s tilt controls lift, not direction of travel Plane’s tilt controls lift, not direction of travel

12. Airplanes 12 Limits to Lift: Stalling At too great an angle of attack, At too great an angle of attack, Upper boundary layer stalls Upper boundary layer stalls Airstream detaches from wing Airstream detaches from wing Lift nearly vanishes Lift nearly vanishes Pressure drag appear Pressure drag appear Wing can’t support plane Wing can’t support plane Plane plummets abruptly Plane plummets abruptly

13. Airplanes 13 Question 4 Why are there different wing shapes? Why are there different wing shapes?

14. Airplanes 14 Wing Shape Asymmetric airfoils produce large lifts Asymmetric airfoils produce large lifts well suited to low-speed flight well suited to low-speed flight Symmetric airfoils produce small lifts Symmetric airfoils produce small lifts well suited to high-speed flight well suited to high-speed flight can fly inverted easily can fly inverted easily High-speed planes often change wing shape in flight High-speed planes often change wing shape in flight

15. Airplanes 15 Question 5 How does a plane turn? How does a plane turn?

16. Airplanes 16 Turning and Orientation Airplanes also use lift to accelerate to the side Airplanes also use lift to accelerate to the side Three orientation controls: Three orientation controls: Angle of attack controlled by elevators Angle of attack controlled by elevators Left-right tilt controlled by ailerons Left-right tilt controlled by ailerons Left-right rotation controlled by rudder Left-right rotation controlled by rudder Steering involves ailerons and rudder Steering involves ailerons and rudder Elevation involves elevators and engine Elevation involves elevators and engine

17. Airplanes 17 Question 5 How does a plane propel itself through the air? How does a plane propel itself through the air? How does a plane maintain its forward momentum? How does a plane maintain its forward momentum?

18. Airplanes 18 Propellers Propellers are spinning wings Propellers are spinning wings They deflect air backward They deflect air backward Do work on air (add energy) Do work on air (add energy) Pump air toward rear of plane Pump air toward rear of plane Action-Reaction Action-Reaction They push the air backward They push the air backward Air pushes them forward Air pushes them forward

19. Airplanes 19 Jet Engines (Part 1) Jet engines pump air toward rear of plane Jet engines pump air toward rear of plane Engine consists of an oval “ball” with a complicated duct or passageway through it Engine consists of an oval “ball” with a complicated duct or passageway through it Air inside the duct exchanges pressure and speed repeatedly Air inside the duct exchanges pressure and speed repeatedly Engine adds energy to air inside the duct Engine adds energy to air inside the duct

20. Airplanes 20 Jet Engines (Part 2) Air entering diffuser slows and its pressure rises Air entering diffuser slows and its pressure rises Compressor does work on air Compressor does work on air Fuel is added to air and that mixture is burned Fuel is added to air and that mixture is burned Expanding exhaust gas does work on turbine Expanding exhaust gas does work on turbine As exhaust leaves nozzle it speeds up and pressure drops As exhaust leaves nozzle it speeds up and pressure drops

21. Airplanes 21 Jet Engines (Part 3) Turbojet obtains forward momentum by Turbojet obtains forward momentum by moving relatively little air moving relatively little air giving that air too much energy giving that air too much energy Turbofan obtains forward momentum by Turbofan obtains forward momentum by moving much more air moving much more air giving that air less energy giving that air less energy

22. Airplanes 22 Introductory Question As you ride in a jet airplane, the clouds are passing you at 600 mph. The air just in front of one of the huge jet engine intake ducts is traveling As you ride in a jet airplane, the clouds are passing you at 600 mph. The air just in front of one of the huge jet engine intake ducts is traveling A. much faster than 600 mph. B. much slower than 600 mph. C. about 600 mph.

23. Airplanes 23 Summary about Airplanes Airplanes use lift to support themselves Airplanes use lift to support themselves Propulsion overcomes induced drag Propulsion overcomes induced drag Speed and angle of attack affect altitude Speed and angle of attack affect altitude Extreme angle of attack causes stalling Extreme angle of attack causes stalling Propellers do work on passing airstream Propellers do work on passing airstream Jet engines do work on slowed airstream Jet engines do work on slowed airstream