At the end of this lesson, you should be able to correctly:
Identify changes to lift and drag resulting from:
airspeed changes;
angle of attack changes;
The various types of drag, including:
parasite (zero lift), form, interference and skin friction;
induced (lift dependent).
Lift
Lift is an aerodynamic force
Lift opposes weight
Lift is a component of Total Reaction Force
Lift acts through the Centre of Pressure
Lift operates:
perpendicular (90°) to Relative Air Flow
perpendicular (90°) to lateral axis
What do we have influence over – what don’t we have influence over?
The Pilot’s Lift Equation
The Coefficient of Lift (CL) is a dimensionless coefficient that relates the lift generated by a ’lifting body’ (read wing) to the fluid density (read air) around the body, the fluid velocity (read relative air speed) and an associated reference area (read wing area).
CL is a function of the angle of the body to the flow, its Reynold number and its Mach number. The lift coefficient cl refers to the dynamic lift characteristics of a two-dimensional foil section, with the reference area replaced by the foil chord.
CL Vs Angle of Attack
Total Reaction Force
Centre of Pressure
The centre of pressure is the point where the total sum of a pressure field acts on a body. In aerospace, this is the point on the aerofoil (or wing) where the resultant vector (of lift and drag) acts.
Span-wise Lift Distribution
Drag
Types of Drag
Parasite Drag: Also known as “Zero Lift Drag”.
Made up of:
Skin Friction Drag (Surface Area, Roughness).
Form Drag
Interference Drag (mixing of airflows at airframe junctions)
Induced Drag: Also known as “Lift Dependent Drag”
Drag as a result of the production of Lift
The combination of these 2 types of drag is called TOTAL DRAG.
CD is essentially a function of Lift production. It is defined as the ratio of Drag Pressure to dynamic pressure and S.
It is directly related to Angle of Attack. Drag is directly proportional to α, V² and S.
Induced Drag
created by the production of lift by a wing of finite span