Lecture 3 Flashcards
What is drag?
A retarding force acting upon a body in motion
The force which tends to resist the motion of a body as it passes through a fluid
What is parasite drag?
Drag produced by air flowing over surfaces not involved in producing lift
What is pressure drag?
How can it be fixed?
Drag resulting from air impinging upon (running into) something
Air hitting a flat board vs air hitting an airfoil
Make frontal area smaller
What is skin friction drag?
How can it be fixed?
Drag resulting from the friction of the air sliding across a surface or the adhesion of the air trying to stick to a surface of a wing or aircraft
Make surfaces smoother
Make wing/aircraft shorter
What is interference drag?
What can be used to eliminate this?
Drag resulting from the turbulence where surfaces meet at 90 degree angles or less
Fairings
Fillets (for small gaps between parts)
What is induced drag?
What can it cause?
Drag that results from the production of lift
High pressure on bottom of the wing slips out from under the wing tips to get to the low pressure on top of the wing
Wingtip vortexes
What makes induced drag worse?
High AOA
High altitude
Flying slowly
High aircraft weight
Inefficient wing design (square is worse than round)
Short wingspan
Low aspect ratio
How can you fix induced drag?
Have a higher aspect ratio
Longer wingspan
Rounded wing design
Winglets
What is a stall?
When can it happen?
How do you recover?
When you exceed the critical AOA and separate the boundary layer, no longer have laminar flow
At any time
Lower the AOA to get air flow going back over the wing
