Aerodynamic Forces
What is the aerodynamic tradeoff between air density and aircraft performance?
Thinner air creates less drag so the aircraft is more fuel efficient, but if the air is too thin it can't create enough lift for the aircraft to stay in the air.
Define angle of attack. Can it be changed during flight?
The angle between the chord line and relative wind. Yes.
Is the speed of sound a higher speed at lower temps or higher temps?
Higher.
What is a subcategory of tab that has to be adjusted on the ground?
Fixed trim tab.
What type of wing contributes to dutch roll?
Swept back wings.
What is the purpose of a spoiler on a wing?
It "spoils" lift by increasing drag. It can help lower a wing in a turn.
Define parasite drag and induced drag.
Parasite drag is caused by things that protrude into the airflow. Induced drag is drag caused by the action of air over the airfoil.
Define angle of incidence.
The angle between the chord line and the longitudinal axis of the aircraft.
Is the speed of sound the same knots per hour all the time? Why or why not?
No. It varies with the air temperature.
What tab is like a servo tab, but has extra force kick in when the aerodynamic load reaches a certain threshold?
Spring tab.
What type of wing helps with lateral stability?
Dihedral.
What is one type of flap that is found on the leading edge?
Krueger flaps.
What is the boundary layer?
It's the layer of air that "sticks" to the surface of an airfoil.
Which combination flight surface is V-shaped?
Ruddervator.
Lateral: controlled by the elevator.
Longitudinal: controlled by the ailerons.
Vertical: controlled by the rudder.
Which type of tab has its own control in the flight deck?
Trim tab.
What is the difference between a ventral fin and a ventral strake?
A ventral fin is a single blade on the centerline of the bottom of the aircraft. A ventral strake is one of a pair of blades on the bottom, straddling the centerline of the aircraft.
What do flaps do?
They increase the surface area of the wing to increase lift. In some cases they also increase the camber of the wing.
If a wing is stalling, what would the airflow look like on top of the wing?
It would look turbulent and swirly, not smooth.
What is the center of pressure?
It's where the total lift force intersects with the chord line.
What is the main difference between supersonic airflow and subsonic airflow?
Supersonic airflow is compressible.
Which type of tab moves in the same direction as the flight control it's attached to? What purpose does it serve?
Anti servo tabs. To dampen the aircraft movement that results from moving the control surface.
What do canards do?
They are forward of the wings. They stall before the wings, causing the aircraft to nose down and descend, which brings it out of the stall before the wings have a chance to stall.
How does the Bernoulli principle apply to wings?
What do vortex generators do and why are they needed?
They create small vortices on the wing surface. This creates a lower pressure area right at the surface which helps the boundary layer "stick."
What is adverse yaw and how is it counteracted?
It's when an aircraft tries to yaw out of the turn; you counteract it by applying rudder input in the direction of the turn.
What type of tab is moved by the movement of the flight control horn, and is there to reduce the force needed to move the flight control?
Balance tab.
You push the nose down on the aircraft. When you let go of the control column, the aircraft swings to nose up, then to slightly less nose down, then slightly less nose up, and so on, until it comes to rest in a level position. What is this an example of?
Positive dynamic and static stability.
Winglets help by reducing vortices at the wingtips. What causes these vortices?
The higher pressure air on the bottom of the wing seeks lower pressure (pressure flows high to low). So, the air is always moving towards the area of lower pressure, which is the tops of the wings - the easiest path is along the bottom out to the tips, where it creates the vortices.