352 CHAPTER 11 Structural Components of Aircraft
Fig.11.1
Principal aerodynamic forces on an aircraft during flight.
Fig.11.2
(a) Pressure distribution around an aerofoil; (b) transference of lift and drag loads to the AC.
and its function; the wings provide the lift, and the tailplane is the main contributor to directional
control. In addition, ailerons, elevators, and the rudder enable the pilot to maneuver the aircraft and
maintain its stability in flight, while wing flaps provide the necessary increase of lift for takeoff and
landing.Figure11.1showstypicalaerodynamicforceresultantsexperiencedbyanaircraftinsteady
flight.
The force on an aerodynamic surface (wing, vertical or horizontal tail) results from a differential
pressuredistributioncausedbyincidence,camber,oracombinationofboth.Suchapressuredistribution,
showninFig.11.2(a),hasvertical(lift)andhorizontal(drag)resultantsactingatacenterofpressure
(CP).(Inpractice,liftanddragaremeasuredperpendicularandparalleltotheflightpath,respectively.)
Clearly,thepositionoftheCPchangesasthepressuredistributionvarieswithspeedorwingincidence.