Lift And Drag Flashcards
What are the lift and drag formulae?
Lift = ½ρV²SCL
Drag = ½ρV²SCD
Name each of the terms used in the Lift and Drag formula and state their SI unit.
V = Airflow or flight velocity (m/s)
S = Wing Area (m²)
ρ = Air Density (kg/m³)
CD = Coefficient of Drag
CL = Coefficient of Lift
What are the approximate angles of attack for best efficiency and stall?
Most efficient angle: 2° to 4°
Stall angle: 12° to 16°
What are the two types of drag that make up total drag?
- Profile drag
- Induced drag
What is Pressure (form) drag caused by?
Caused by the increased static pressure at the front and decreased static pressure at the rear of the object or aircraft.
What is Skin Friction Drag caused by?
Caused by the viscous dragging nature of the boundary layer on the skin.
State the three types of drag that make up profile (zero lift) drag.
- Pressure (form) drag
- Skin or surface friction drag
- Interference drag
When is induced drag produced and what causes it?
It is only produced when the aircraft generates lift. It is caused by differences in static pressure between the upper and lower surfaces of the wing, with air spilling around the tip creating a vortex that increases drag.
Which type of drag is reduced by streamlining an aircraft?
Pressure (form) drag.
Explain how winglets reduce induced drag.
They partially block air spilling around the wing tip from the high-pressure region below to the low-pressure region above, stopping the large vortex formation.
Give two other methods of reducing induced drag.
- Using high aspect ratio wings
- Using tapered wings or wings with washout.
