Drag Flashcards
What is drag?
Drag is the resistance to motion of an object through the air
Define the 2 major types of drag and their speed relaitonship?
Profile Drag and Induced (Lift) Drag
Profile Drag (zero lift drag) comprises of…
Form/ Pressure Drag
Skin Friction Drag
Interference Drag
Induced Drag is greater at ______ speeds.
Lower Speeds (as you need more lift)
Induced Drag and Profile Drag meet at ____.
Vmd
How is the drag curve on a jet compared to a prop?
A jet drag curve is…
- Flatter due to less Induced and Profile Drag
- Shifted to the right with a higher Vmd because of the swept wings is
more efficient against profile drag
What is the pitching moment associated with the thrust-drag couple?
Causes an upward pitching moment due to the thrust vector being below the drag vector. Causing a natural pitch up.
What are high-drag devices?
Trailing Edge Flaps
Spoilers
Landing Gear
Reverse Thrust
Braking Parachute
What causes wing-tip vortices
Created by a span wise flow over the upper and lower surfaces of an aerofoil. Happens a lot on a swept wing. The pressure differential gets smaller as you go down the wing, and by the time you get to the tip it is 0.
What is the effect of span wise airflow over a wing?
Creates wing-tip vortices
Reduced aileron efficiency
Increased disturbed airflow on the upper surface of the tip, contributing to wing tip stall
What are the effects of wing tip vortices?
Creates aircraft drag (induced drag) by downwash
How do you stop span wise airflow?
Fences and vortex generators
What are winglets, how do they work?
Designed to reduce induced drag. They dispense span wise flow, preventing mixing of these airflows to reduce induced drag vortices
What are winglets, how do they work?
Designed to reduce induced drag. They dispense span wise flow, preventing mixing of these airflows to reduce induced drag vortices
