Lecture 2 Flashcards
What makes up the atmosphere?
78% Nitrogen
21% Oxygen
1% Other
By _____ feet, half of all the air on the planet is below you and by ____ feet, 75% of all air is below you.
18,000
34,000
How does temperature affect the density of air?
Air expands when heated
Air is less dense when it is ____ and more dense when it is ____.
hot
cold
How does humidity affect the density of air?
Water vapor is less dense than air (less dense in high humidity)
Air is less dense when there is ____ humidity and more dense when there is ____ humidity.
high
low
How does altitude affect the density of air?
Fewer air molecules as you reach higher altitude
Air molecules can spread out more at higher altitudes
Air is less dense at ____ altitude and more dense at ____ altitude.
high
low
Air is least dense on ____, ____ days, and at ____ altitude.
Air is most dense on _____, _____ days and near _____.
hot
humid
high
cool
dry
sea level
What is a standard day?
59°F
Sea level
Zero humidity
What are the four forces on an airplane?
Lift
Weight
Thrust
Drag
What is Newton’s 1st Law?
Which force(s) does it apply to?
A body at rest will stay at rest until an external force acts on it
Drag
What is Newton’s 2nd Law?
A force applied to an object at rest causes it to accelerate in the direction of the force
What is Newton’s 3rd Law?
Which force(s) does it apply to?
For every action, there is an equal and opposite reaction
Accounts for 10% of lift
Thrust
What is Bernoulli’s Principle?
As the velocity of a fluid increases, the pressure decreases
Does the top or the bottom of the wing have higher pressure?
Why?
Pressure is higher on the bottom on the wing
Velocity over the top of the wing is higher and lowers the pressure (Bernoulli’s Principle)
What accounts for 90% of the lift of a wing?
What about the other 10%?
Bernoulli’s Principle (Bernoulli Effect)
Newton’s 3rd Law
How is lift created?
The more differential pressure between the top and the bottom of the wing, the more lift is produced
What is the Coanda Effect?
A moving stream of fluid in contact with a curved surface will follow the curvature of the surface rather than continue traveling in a straight line
How can you increase the camber shape of the airflow?
How can a higher camber help?
Increasing the AOA of the wing
More camber = more lift
List some things that can disturb airflow on the leading edge of a wing
Rivet heads
Bolts
Dents
Ice formation
What is the center of pressure?
Lowest air pressure on the top of the wing, or the greatest pressure differential between the top and bottom
Lift acts _____ from the _____.
Weight acts _____ from the _____.
upward
center of pressure
downward
center of gravity
Where is the center of gravity in relation to the center of pressure?
CG is slightly forward of the CP
What is the center of gravity?
Mathematical collection of where weight is applied
What are the five parts of an airfoil?
Leading edge
Trailing edge
Upper camber
Lower camber
Chord line
What is the chord line?
Does it have to be inside the wing?
A straight line from the leading edge to the trailing edge
No
What is camber?
The curvature of the wing
The curvature of the air over or under the wing
What is span?
What is chord?
What is aspect ratio?
Length of a wing
Width of a wing
Span divided by chord
What is the dihedral angle?
What is the purpose of it?
The angle of the wing from wing chord to wing tip in relation to the ground
Stability
What is the mean camber line?
Which side of this line is positive?
Average camber line
Created by subtracting chord line to lower camber from chord line to upper camber
Above the line is positive
Below the line is negative
What is the mean aerodynamic chord?
The distance between the leading and trailing edge of a wing measured parallel to normal airflow over the wing
Why do we care where maximum camber is located?
Correlates to the location of lowest pressure (center of pressure)
We need to keep the center of gravity in front of the center of pressure to keep the aircraft stable
