Welcome
What is
Aeronautical Engineering?
 Physics of atmospheric
flight
 Several sub-disciplines:
+ Aerodynamics
+ Propulsion
+ Stability and Control
+ Structures
+ Aircraft Performance
= Aircraft
(or Rocket)
Design!!!
Aeronautical Engineering:
The Pilot’s Perspective
Aeronautical Engineering:
The Engineer’s Perspective
Aeronautical Engineering:
The Engineer’s Perspective
Objective of
Aeronautical Engineering
 Effectively and efficiently
create and manipulate
forces for flight
 Efficiently manipulate
energy
Aeronautical Engineering
Designing extraordinary aircraft…
Uncovering fascinating
physical phenomena…
Sometimes the engineer
makes a mistake…
Sometimes the pilot
makes a mistake…
AERODYNAMICS
Aerodynamics In
A Nutshell
 When a fluid moves about a solid surface, pressure and
friction forces are created
– Air may be considered a “fluid” just like water
– Doesn’t matter if the fluid is moving past a stationary object or if the
object is moving in a stationary fluid
– Pressure and friction forces can help (“lift”) or hurt (“drag”)
 wind tunnels often used in design of aircraft
 open car window “wind tunnel”
 We control forces by changing or controlling the…
– …shape of the object
– …orientation of the object with respect to the flow
– …relative speed of the object and the flow
 Goal: Lift overcomes Weight, Thrust overcomes Drag!!!
Aerodynamics and the
Laws of Physics
 Conservation of Mass
– Mass can be neither created nor destroyed...
– What happens when you hold your thumb over the end of a water
hose?
 Conservation of Momentum - Newton’s Second Law
– Time rate of change of momentum of a body is proportional to, and
in the same direction as, the force (momentum is conserved)
– Force = Mass x Acceleration
 Ideal Gas Law
– Relates pressure, temperature, and density of gases
– Pressure = Density x Temperature x Gas Constant
Euler’s Equation
(Momentum Equation for Fluids)
F  m
dV
 mass x accelerati on
dt
General statement of
Newton’s 2nd Law
What it means:
• force acting on an object is proportional to time rate
of change of momentum
 dp   VdV
What it means:
Euler’s Equation - Newton’s
2nd Law applied to a fluid
 Pressure  Density x Velocity x Velocity
• small changes in velocity make small changes in pressure
and visa versa, or
• as velocity increases, pressures drops (Bernoulli Principle)
 Airflow between two Styrofoam balls
Application: Flow Past
an Aircraft Wing
 Conservation of Mass - flow speeds up as streamlines
get closer together
– You’ll see a smaller space between smoke lines
higher V!
 Euler’s Equation says static pressure must therefore
decrease
– higher V
lower P!
 Pressure difference between upper and lower
surfaces (higher pressure below wing) results in lift
INTRODUCTION
TO
AIRFOILS & WINGS
Airfoil Parts
z
Max thickness
Max camber
Mean camber line
x
Chord line
Chord
x=0
Leading edge
x=c
Trailing edge
Airfoil Characteristics
tip
chord
root
chord
leading edge
sweep angle
total wing
area, S
span, b
tip chord
root chord
b2
aspect ratio 
S
taper ratio 
Airfoil Forces
and Moments
Lift
Aerodynamic Force
Moment
+
V

Drag
Relative
wind
Angle of attack () : angle between relative wind and
chord line
Note: 1) lift is perpendicular to relative wind
2) drag is parallel to relative wind, not the horizon
3) moment is positive nose-up
Effect of
Angle-of-Attack
A higher angle-of-attack results in increased lift (up to
stall), but also increased drag
L
D
stall
zero
lift

L
Wingtip Vortices
low
pressure
high
pressure
Wingtip Vortices
Contrails:
A Vortex or a Cloud?
INTRODUCTION
TO
STABILITY
AND
CONTROL
Balance and Stability
Examples
 Center of Gravity vs
Aerodynamic Center
 Examples:
 Frisbee Ring
 Balsa wood airfoil
Restoring Moments
Desired Restoring Moment (-Mcg )
V
Disturbance (+ a )
Restoring Moments
V
Displacement (-  )
a
Desired Restoring Moment (+Mcg )
Aircraft Axis System
l
x
(Longitudinal
Axis)
 An automobile has 2 degrees of freedom
 An aircraft has 6 degrees of freedom
– 3 in translation (movement along each axis)
– 3 in rotation (movement about each axis)
m
y
(Lateral Axis)
n
z
(Vertical Axis)
Traditional
Aircraft Controls
All moving
Elevators
(Also called stabilator
or tailplane)
Ailerons
(Flaperons)
Rudder
Aircraft Motions - Roll
 Roll: Motion about the longitudinal (X) axis
produced by the ailerons
Ailerons
Aircraft Motions - Pitch
 Pitch: Motion about the lateral (Y) axis produced
by the elevators
Elevator
Aircraft Motions - Yaw
 Yaw: Motion about vertical (Z) axis produced by
the rudder(s)
Rudder
Stability and Control ?!?
Sometimes you have it… yeah!!!
Sometimes you don’t… ouch!!!
The future???
Balsa Glider
Moment Balance
L
L
M
l
X ac
X
ac
cg
t
t