In aviation, the drag force is the frictional force of air in the opposite direction to the aircraft speed. It has two components:
- The induced drag, generated at the lift surfaces (e.g. the wing) by the lift itself (see diagram);
- the parasitic drag caused by the shapes of the aircraft (e.g. the landing gear, which generates high drag).
Any surface that generates a lift force also produces drag (induced drag). An aircraft wing generates lift opposing the weight but also drag opposing the engine force (the pull of propellers or the thrust of reactors, not shown here). © DR