The force against the thrust is drag

OR

The force acting in the direction of relative airflow is drag

OR

During flight all parts of an aircraft exposed to the airflow

experiences a resistance as aircraft moves through the air,

the force is known as drag

Drag

Parasite Drag

Profile Drag

Interference Drag

Induced Drag

Skin Friction Drag

Form Drag

The parts not contributing to lift are called parasite

and the drag they produce is called parasite drag

The sum of skin friction drag and form drag is

known as profile drag

Skin friction drag is the reaction to the retardation

of the airflow within boundary layer, it depends

upon the rate at which the air trying to slide

adjacent to the aircraft surface

Directly proportional to square of speed

Roughness

Irregular Shape

Cruise at optimum efficiency speed

Polishing

Aerodynamic shapes

When streamline air flow passing over an aircraft

separates from the surface and becomes

turbulent, this phenomena is known as form drag

Directly proportional to square of speed

Hindrance (e.g. undercarriage)

Irregular shapes

Roughness

Aerodynamic shapes (even, smooth,

well cambered)

Fairing on undercarriage

When two differently directed airflows interfere

they produce interference drag e.g. joint between

different aircraft parts such as wing and fuselage,

lights, stabilizers and antennas

Aerodynamic Joints

The force that occurs when the aircraft redirects the

airflow coming at it, this drag force occurs due to wings

OR

Pressure difference from top to bottom of wing (span-

wise flow) causes vortices along the wings particularly

wing tips

It is a by-product of lift

Increases with increasing angle of

attack

inversely proportional to speed

increases

Increase wing span (Aspect ratio)

Wing-lets

Washout

Fuel tank on wing tips

Tapered wings

Wing tips modification