Increasing Camber or Energy Additions to the Boundary Layer
AMT 280 LaboratoryAirfoil Slat & Flap Effects•One of the ways to improve the versatility and flight characteristics of an airplane is to install wing flaps and slats. Flaps are designed so that when extended they not only provide higher lift but also have higher drag. This allows a steep angle of descent at slow airspeeds with low engine power output •Objectives–Observe the effects of the flap and the slat on a model airfoil with respect to lift and drag.–Observe the general airflow pattern over the airfoil while using flaps and slats.–To observe the creation of wing tip vortices
Airfoil Slat & Flap EffectsEffect of high lift devices•The primary purpose of high lift devices (flaps, slots, slats, etc.) is to increase the CLmaxof the aircraft and to reduce the stall speed. •Take-off and landing speeds are also reduced.
Split flap – larger change in drag because of turbulent wake produced by this type of flap
Slotted flap – high-energy air from the lower surface is ducted to the flap upper surface. This air from the slot accelerates the upper surface boundary layer and delays airflow separation to some higher lift coefficient. This flap causes much greater increases in CLmaxthan the plain or split flap and section drags are much lower
Slats or leading edge devicesThe leading edge slats allow the aircraft to fly at a high angle of attack (lower speed) by accelerating the air between the slat and the wing (venturi effect).This increases the drag, but improves handling at low speed.
When the slot on a wing is open, the air flows through the slot and over the airfoil. This results in a delay of airflow separation (figure a). Use of a slat allows the airfoil to be flown at a higher angle of attack before a stall would occur.