References: -Transport Canada Study and Reference Guide Glider Pilot -FTGU pages 21-39 : 40 Minutes 6.05 Lift BC Online Ground School: Theory of Flight References: -Transport Canada Study and Reference Guide Glider Pilot -FTGU pages 21-39
Slide 2 : 1. Name the 4 forces acting on an aircraft.
Lift, Weight, Thrust, Drag
2. What are Newton’s 3 laws?
A body persists its state of rest or of uniform motion will stay in motion unless acted on by an external unbalanced force.
Force = mass x acceleration
For every action, there is an equal and opposite reaction.
3. Is an aircraft considered to be in a state of equilibrium when it is on the ground.
No
Slide 3 : MTPs
Bernoulli’s Principle- how lift is created
Airfoil terms
Relative airflow
Angle of Attack
Centre of Pressure
Angle of attack versus lift
Types of airfoils
Slide 4 : Bernoulli’s Principle
An increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.
Slide 5 : Bernoulli’s Principle Pressure Speed Speed Pressure
Slide 6 : Bernoulli’s Principle
Airfoils are shaped in a way to manipulate air pressure based on Bernoulli’s principle.
Air moves faster over the upper surface of the wing, decreasing pressure (or increasing suction)
Air moves slower over the lower surface of the wing and creates a higher pressure, or pushing force.
Slide 7 : Terms related to airfoils
Relative Airflow
Angle of Attack
Centre of Pressure
Slide 8 : Relative Airflow
The direction of the airflow with respect to the wing.
It is created by the movement of the airplane as well as the movement of air.
Relative airflow is usually opposite to the flight path.
Relative airflow is not related to lift
Slide 9 : Angle of Attack
The angle at which the airfoil meets the relative airflow
Slide 10 : Centre of Pressure
Is the average of the pressure on an airfoil
Sum of the distributed pressures on the airfoil acting through a single straight line
Moves forward on an airfoil as the angle of attack is increased
Slide 11 : Center of Pressure
** Centre of pressure moves forward until the point of a stall, then it moves rapidly backward
Slide 12 : Now we know how we get lift but how much can we get?
One factor affecting lift is Angle of Attack
As the angle of attack increases, what happens to lift?
BUT… As the angle of attack increases, what happens to drag? Lift Increases Drag Increases
Slide 13 : Lift can only be optimized until the critical angle of attack is exceeded.
Critical Angle of attack: the angle at which an aircraft will stall
Once this critical A of A is exceeded, the airfoil will stall regardless of airspeed or camber
Slide 14 : Lift/ Drag Angle of Attack
Slide 15 : Airfoils
A two-dimensional surface designed to obtain a reaction from the air through which it moves.
The shape of an airfoil will affect how air flows over the wing Airfoil – 2D vs. Wing – 3D
Slide 16 : What are some functions of airfoils?
Create lift
Create thrust
Attachment point for the control surfaces (including flaps, slots, slats, etc)
House fuel tanks and instrument components
Stability
Slide 17 : Confirmation Check
Slide 18 : 1. Label where the high pressure and low pressure are:
2. Fill in the blanks
__________________: The angle at which the airfoil meets the relative airflow
__________________: airflow with respect to the wing
__________________:the average of the pressure on an airfoil
Slide 19 : 3. Lift acts 90o to the ________________.
4. Bernoulli’s principle states that:
An ____________ (increase/decrease) in the speed of a fluid occurs simultaneously with a _____________________ (increase/decrease) in pressure or a _______________ (increase/decrease) in the fluid's potential energy
5. As lift increases, drag _______________.
Slide 20 : What we have covered
Bernoulli’s Principle- how lift is created
Airfoil terms
Relative airflow
Angle of Attack
Centre of Pressure
Angle of attack versus lift
Types of airfoils