ME 480 Introduction To
Aerospace: Chapter 2
Prof. Doug Cairns
Forces On a Body
Spatial Quantities
pressure, density, temperature, velocity
Supersonic flow
(oil streak used for visualization)
Smoke Injectors to Visualize
Streamlines
Particles follow Streamlines
Basic Parts on an Airplane
Basic Controls of an Airplane
For the Next Few Slides
• Basic Physics of Flight
• What’s happening during a flight
• Rule of Thumb airplane design
2-9
Basic Forces
Lift
Drag
Trim
Thrust
Weight
2-10
What’s in Weight? Lift
Drag
Payload
Paying Passengers
and Cargo
Trim
Thrust
Fuel
Reserves
Operating items
Airplane
Operating
Empty
Weight (OEW)
Systems
Navigate, control and support life
Propulsion
Generate force to move airplane
Landing Gear
Support airplane on the ground
Body
Wing & Tails
2-11
Food, Supplies
Enclose the payload
Provide lift
Weight
Weight changes during the flight.
End of flight Start of Flight
Burn off fuel
Payload
Fuel
Payload
Fuel
Reserves
Operating items
Operating
empty weight
Systems
Navigate, control & support life
Propulsion
Generate force to move airplane
Landing Gear
Support airplane on the ground
Body
Wing & Tails
2-12
Food, Supplies
Enclose the payload
Provide lift
How do you make Lift?
Lift
Drag
Bernoulli:
“The faster the air flows over the
surface, the lower the pressure air
exerts on the surface.”
2-13
Trim
Thrust
Weight
How to Change Lift
• Since Lift is about the same as weight and
weight changes, then must be able to change
lift.
– Increase lift by
• increasing the tilt of the wing
• increasing the speed of the airplane (actually speed
squared)
• decreasing the altitude of the airplane above the
ground.
2-14
But there are Limits to Lift
“Stall”
The flow no longer
can stay attached
to the upper
surface.
Lift
Airfoil Tilt Angle
2-15
Ways around the Limits to Lift
“Slats & Flaps”
“Slats”
Lift
Airfoil Tilt Angle
2-16
Wings are made up of airfoils
Airfoil
2-17
Wing
How to create Thrust
Lift
Drag
Trim
Thrust
Weight
•A propeller produces thrust like a wing
produces lift except:
• The propeller is a wing rotated 90 degrees
• The speed over the airfoil comes from rotating
the prop.
2-18
How does a jet engine produce thrust?
Propeller (“compressors”)
Propeller (“turbines”)
Fuel Burned
(Generates
high speed air)
A jet engine “sucks, squeezes, burns and blows.”
2-19
Thrust
What is “Drag”?
Lift
Drag
Trim
Thrust
Weight
Lift and Span
Aerodynamic
details
Smoothness
Outside surface
area
2-20
Induced
“Pressure”
Excrescence
Skin Friction
Due to the influence of an airfoil on those outboard
of it
Due to the rapid growth of the boundary layer
Due to roughness, gaps & antennas
Due to the friction in the boundary layer next to the
skin to the air flowing over the skin.
What & Why Trim?Lift
Drag
Trim
Thrust
Weight
• Trim comes from a wing like surface
mounted on the back of the airplane
• To change the tilt of the airplane
– increase down load - airplane nose goes up
– decrease down load - airplane nose goes down
2-21
Airplane Controls
Fin
Rudder
Aileron
Elevators
Flaps
Slats
Stabilizer (Tail)
Spoilers
2-22
Airplane Stability
A stable system
A stable airplane
Lift
Move the ball away
from the bottom and it
returns to the bottom
Because ball’s center of
gravity is above the
bottom of the bucket
2-23
Weight
Move the nose of the airplane up
and the airplane’s nose will come
back down.
Because airplane’s center of lift is
aft of the center of weight
How does an airplane turn?
It banks.
Lift
Weight
2-24
Why do airplanes have rudders?
To balance an inoperative engine and crosswinds.
2-25
Design Envelope
Engine out
takeoff
Stall Margins
Pressurization
System
redundancy
Brake
Capability
Fatigue
Takeoff and
Landing
Distances
2-26
Flutter
Situation
Awareness
Structural
Strength
margins
Speed
margins
The Plane that Taught America to Fly
Note: Dr. Cairns has around 100 hrs in this make and type, over 200 hours in
similar type aircraft
We will have an opportunity to crawl
around one of These!
The Greatest Fighter Aircraft Ever
(according to the Military Channel)
The Funny Looking X29
(forward swept wing for better maneuverability)
Spacecraft
More Spacecraft
The Road Map