AER 3: Drag

Question 1

Define drag

Answer 1

A force acting opposite and parallel to flight.

Question 2

Define zero lift drag (ZLD)

Answer 2

ZLD is drag caused by the shape of the aircraft that doesn’t produce lift. ZLD requires thrust to be created and is zero at zero airspeed and increases as the square of the speed of the aircraft. (ZLD increases as EAS increases). Examples of ZLD include: form drag and surface friction drag. (created as the airflow increases).

Question 3

Does the cL and the AoA have an effect on ZLD?

Answer 3

No, they have no direct effect on ZLD, except the drag caused by increase/decrease in AoA, which produces more or less drag.

Question 4

Define Lift Dependant/Induced drag (LDD)

Answer 4

Is created as a result of the aircraft going through the air and caused by the lift motion of the aircraft. As EAS increases, LDD decreases. Example: wingtip vortex created.

Question 5

Define interference drag

Answer 5

Formed at the junction of various surfaces of the a/c, such as between the wing and the fuselage, where the airflow across each surface interacts and becomes turbulent, causing drag. (is an element of ZLD)

Question 6

Define form drag

Answer 6

A function of (created by) the size, shape and speed of an object. (is an element of ZLD)

Question 7

Define surface friction drag

Answer 7

Drag caused by the type of surface of the aircraft, including surface condition and what the skin of the aircraft is made up of. (is an element of ZLD).