Aerodynamics Flashcards
fWhat are the four forces acting on an aircraft?
- Lift - Upward acting force
- Weight - Downward acting force
- Thrust - Forward acting force
- Drag - Backward acting force
What happens when all opposing forces are equal?
Steady, Straight-and-Level, Unaccelerated flight. When all opposing forces are equal, their respective effects are canceled out.
What is Relative Wind?
Relative Wind is the direction of airflow in respect to the wing.
Flight path and relative wind are always parallel but travel in opposite directions.
What is Angle of Attack?
The angle between the wing chord line and the relative wind. This can be changed by the pilot.
Explain Bernoulli’s Principle. How does this apply to Lift?
The pressure of a fluid (liquid or gas) decreases at points where the speed of the fluid increases.
High speed airflow = Lower pressure
Low speed airflow = Higher pressure
An airfoil (wing) is designed to increase the velocity of airflow above its surface by increasing surface area which decreases pressure above, and on the lower surface will generate higher pressure.
The combination of decreased pressure above and increased pressure below will create lift.
What is Ground Effect?
Ground Effect is a condition of improved performance when a plane is flying close to the ground. (wingspan height off the ground)
What happens in Ground Effect?
The air flow around the wing is restricted by the ground surface. Reducing upwash, downwash, and wing tip vertices.
What is torque effect?
Referring to Newton’s Third Law, as the internal parts and propeller are rotating in one direction an equal force is trying to rotate the airplane in the opposite direction. (Greatest at low airspeeds with high power settings and high angle of attack)
What are the effects of torque?
In flight -
The torque reaction is acting upon the longitudinal axis, making the plane roll.
On the ground -
During takeoff, the left side of the airplane will be forced down by torque reaction causing more weight to be placed on the left landing gear.
What four factors contribute to torque effect? (Left Turning Tendencies)
Torque Reaction of the engine and propeller - the rotation of the propeller to the right causes the plane to roll or bank to the left.
Gyroscopic effect of the propeller - The concept of gyroscopic precession takes effect here.
Propeller Slipstream - The spinning propeller in a high power setting will send a slipstream to the rear of the plane in a corkscrew fashion to hit the rudder on its left side. This will push the tail to the right making the plane yaw to the left.
P-Factor (Asymmetrical Loading of the propeller) - When flying at a high angle of attack, the bite of the downward moving blade is greater than the upward moving blade. This creates more thrust on the downward moving blade on the right side causing the plane to yaw left.
What is Centrifugal Force?
It is the tendency of an object moving in a circle to travel away from the center of the circle. It is the outward force, away from the axis of rotation, acting on a revolving object. It acts “equal and opposite” to the horizontal component of lift.
What is Load Factor?
The ratio of total load supported by the planes wing to the actual weight of the plane and its contents. It can also be expressed as the ratio of given load to the pull of gravity (G forces)
