LE Slats (function)

[lou ross]

Understand flaps, but what do the slats do? thanks, lr.

[Trislander]

Hi Lou,

Leading edge slats (when deployed) increase the 'camber' or curvature of the wing thus generating more lift at lower airspeeds.

They are used for take-off, approach & landing.

Tri

[ROB-x38]

Leading-edge high lift devices such as Kruger flaps, slats and droops reduce the stall speed and increase the stalling angle of attack. In the case of slats air is ducted from below the wing to improve boundary layer energy, delaying separation and the stall.

Also a consequence of swept-wing aircraft is that there is a spanwise component of airflow - ie: air flowing from the wing root to tip. This results in a deeper boundary layer at the wingtip and the likelihood that the tip will stall first. Bad because:
- outboard ailerons lose effectiveness
- tip stall -> loss of lift at the tip -> centre of pressure moves forward -> pitch up

Slats help to reduce this spanwise flow and the tendency for a tip-stall.

[john_tullamarine]

If you are comfortable with trailing edge flaps, then it might be easier to think of leading edge devices in terms of reducing the extent of the pressure gradients on the forward chord section at high alpha.

If you think back to the typical trailing edge flap lift curve, leading edge devices have the effect of extending the stall CL end of the lift curve slope to higher alpha and higher CL.

[lou ross]

Thanks for your responses, gentlemen. lr.