aerodynamics Flashcards
What are the four forces of flight?
Lift Weight Thrust Drag
How is lift created?
Airfoils accelerate airflow downward – this is an example of Newton’s 3rd law
Bernoulli’s Principle – high speed air over the upper surface creates low pressure while low speed air beneath the wing creates high pressure. Low pressure above the wing is a essentially a suction force that keeps an airplane aloft. High pressure below the wing seeks to equalize the low pressure area above by pushing up against the airfoil and also contributes to lift.
o Air traveling faster over a curved upper surface causes lower pressure
on the top surface, pulls wing up.
o High pressure air underneath the wing tries to get to the upper portion
of the wing, creating lift.
Explain the different types of drag
Parasite- increases with speed
form: shape in air
interference: opposing features combining
skin friction drag: material
Induced – byproduct of lift
Describe the various components of an airfoil
Leading/trailing edge
Upper/lower camber
Chord line
Relative wind
Angle of attack
What is camber?
Can we change it?
Curvature of the wing – it can be changed by extending/retracting flaps
Explain Bernoulli’s Principle
As velocity of a fluid or air increases, the pressure decreases. High speed air over the upper surface creates low pressure while low speed air beneath the wing creates high pressure. High pressure moves upwards towards the lower pressure.
What is angle of incidence? Can we change it?
The angle between the wing chord line and the fuselage – it cannot be changed
Explain Stability
Lateral stability
Longitudinal stability
Vertical stability
Positive stability
Betrayal stability
Negative stability
Static stability
Dynamic stability
Lateral stability
Resistance to roll
Longitudinal Stability
Resistance to pitch
relationship of center of gravity to
center of lift.
In small aircraft, center of gravity is in front of center of lift
Vertical Stability
Resistance to yaw
Positive Stability
Tendency to return to equilibrium
Neutral Stability
Tendency to stay in new position
Negative Stability
Tendency to continue to move away from equilibrium
Static Stability
Initial tendency
Dynamic Stability
Response over time
Compass errors
magnetic variation
Difference between magnetic and true north
What do you do if you become lost in-flight?
Climb
Circle
Conserve
Confess
Communicate
Aircraft is in equilibrium during unaccelerated flight when
Thrust = Drag
Lift = Weight
Chord line
from middle of leading edge to middle of trailing edge of wing
Angle of attack
angle from the relative wind to the chord line (A).
Angle is acute, less than 90 degrees
Laminar flow
when air flows smoothly over the win
aerodynamic stall
angle of attack is too high, the air no longer conforms to the wing and separates
Frost
• Frost or anything else on a wing will disrupt smooth airflow.
• May prevent the aircraft from becoming airborne at normal takeoff speed.
• May also increase stall speed
Aerodynamics of flaps
Flaps down increase the drag, allow a steeper approach to landing (angle of
descent) without increasing airspeed.
Yaw
turning around the vertical axis, controlled by the rudder
Roll
turning around the longitudinal axis, nose to tail, controlled by
alerions
Pitch
turning around the lateral axis, side to side, controlled by the elevators
Load Factor
Banking (turn) increases G forces (the load factor) on aircraft. Compensates
for centrifugal force
Airfoil
The profile (side view) of a wing
Angle of Attack
Angle between the wing chord line and the relative wind. It can be increased or decreased
Chord Line
An imaginary straight line from the wing leading edge to the wing trailing edge
Leading Edge
The farthest front point of the wing where air first strikes
Trailing Edge
The farthest aft point where the air leaves the wing
Upper Camber
Top half of the wing above the chord line
Lower Camber
Lower half of the wing below the chord line
Mean Aerodynamic Chord
Imaginary curved line from the leading edge to the trailing edge
Relative Wind
The air vector striking the airplane as it flies through the air. It is opposite to the flight path
Flight Path
The direction that the airplane is flying through the air
Angle of Incidence
Angle between the chord line and the longitudinal axis of the airplane. This angle is fixed.
Longitudinal Axis
A straight line from the nose of the airplane to the tail
Lateral Axis
A straight line from the one wing tip to the other wing tip
Vertical Axis
A vertical line through the center of the airplane
four basic flight maneuvers
level flight, turns, climbs, and descents
