Chapter 3 Flashcards
Bernoulli’s Principle
As the velocity of a fluid increases, its internal pressure decreases.
Venturi
Tube which is narrower in the middle than at the ends.
Airfoil
Any surface which provides aerodynamic force when it interacts with a moving stream of air.
Upwash
Deflection of oncoming airstream upward and over the wing.
Leading edge
Part of airfoil that meets the airflow first
Trailing edge
Portion of airfoil where airflow over upper surface and lower surface join
Downwash
Downward deflection of airstream as it passes over wing and past the trailing edge.
Angle of Attack
Angle formed by wing chord line and relative wind.
Relative Wind
Airflow which is parallel to and opposite the flight path of the airplane.
Camber
Characteristic curve of the airfoil’s upper and lower surfaces.
Chord Line
An imaginary straight line drawn through airfoil from leading edge to trailing edge.
Lift acts _____ to the relative wind, regardless of angle of attack.
Perpendicular.
Coefficient of Lift (C_L)
A way to measure lift as it relates to the angle of attack.
How is C_L determined?
Wind tunnel tests. Based on airfoil design and angle of attack.
Stall
Separation of airflow from the wing’s upper surface. Results in rapid decrease of lift.
Stalling or critical angle of attack
For a given airplane, a stall always occurs at the same angle regardless of airspeed, flight attitude, or weight.
First indications of stall in training airplane?
- mushy controls
- stall warning device
- slight buffering of airplane
What is the essential goal of recovering from a stall?
Restore smooth airflow by decreasing angle of attack to a point below the critical angle of attack.
C_LMax
Angle of attack that has the maximum amount of lift. After this point lift decreases rapidly.
Four main design considerations for wing design
1) wing planform
2) camber
3) aspect ratio
4) total wing area
Boundary layer
Thin layer of air next to the surface of an airfoil which shows a reduction in speed due to air’s viscosity.
The boundary layer can be described in two ways what are they?
Laminate or turbulent
Laminar flow
Begins near leading edge. Consists of smooth laminations of air sliding over one another.
Aspect Ratio
Span of wing tip to wing tip, divided by average chord. Higher the aspect ratio, the higher the efficiency of the wing.
One of primary factors in determining lift/drag characteristics. At a given angle of attack, a higher aspect ratio produces less drag for the same amount of lift.