Lift Flashcards
What is an airfoil?
It is any surface that is designed to obtain lift
What is the most suitable shape for producing lift?
most suitable shape is a curved or cambered shape
Which surfaces in an airfoil section has a greater curve?
The upper surface has a greater curve than the lower surface
what is a DOWNWASH?
air passes OVER the wing towards the trailing edge, the air flows not only rearward but downward as well
What was Isaac third law?
For every action there is an opposite and equal reaction
What happens to the airflow that passes under the wing?
The airflow is bended downward by the bottom surface of the wing
What happens when you put a downward force into the air?
When you put a downward force into the air the wing will receive an upward counterforce creating lift (refer to newton’s third law)
What happens when more air is bended downward?
the more air that is bended downward the more lift that is created
What is the Bernoulli principle?
if one element of an energy system is increased, another decreases to counter balance it
How does the Bernoulli principle apply to lift?
the faster speed of air along the top of the wing leads to less air pressure therefore creating lift
What is relative airflow/relative wind?
Relative airflow is the direction of airflow to the wing
What is the relative airflow to the wing when the wing moves forward and downward?
the relative airflow is upward and backward
If the wing is moving forward horizontally what is the relative airflow?
the relative airflow moves backwards horizontally
What is the connection between the relative airflow to the wing?
the connection is that they are always parallel but opposite of each other
How is relative airflow created?
It is created by the motion of the airplane through the air or by the motion of air that passes a stationary body. Or it could be created by a combination of both
Does the direction and speed of the wind have an effect on relative airflow?
No, this is because only the motion and mass of air will produces relative airflow
What is the angle of attack?
The angle of attack is when the airfoil meets the relative airflow
What happens when the angle of attack increases?
when the angle of attack increases this changes the pressure over the upper and lower surfaces and amount of downwash which increases up to a point (angle of stalling) before it decreases.
What is the centre of pressure?
If you add all the forces into one single force it will act as a straight line. The point where the line cuts the chord of an airfoil is the centre of pressure
what happens when the angle of attack is increased up to the point of a stall?
The centre of pressure will move forward after this point it will move back
How does the movement of the centre of pressure effects the airplane?
It will make the airplane unstable
