Robert W. Mellette
DRAG can be defined as the resistance to the forward motion of an aircraft. Students can probably best understand what drag is by experiencing it. Explain that DRAG can be “felt” by putting your hand out of the window of a fast moving automobile. The hand with fingers extended is placed with the open palm facing in the direction of travel. The impact of the airstream creates a force (DRAG) that is readily sensed. In more scientific terms, DRAG is actually a combination of many separate forces that add together to retard the forward motion of the aircraft.
DRAG can be divided into two main categories,
INDUCED
DRAG and PARASITIC
DRAG
. INDUCED DRAG is the DRAG created as a result of the process required to produce LIFT. PARASITIC
DRA
G is due to the frictional forces involved as the airstream pass-es over the surfaces of the aircraft.
At certain times, the pilot uses DRAG intentionally to control the aircraft. As an example, in preparation to landing a pilot lowers FLAPS to increase DRAG to slow the aircraft down to the proper approach speed.
(figure available in print form)