Re: 727 inboard leading edge devices

Date:         20 Jan 98 01:29:57 
From: (Luis Manuel Perez Llera)
Organization: Unisource Espana NEWS SERVER
References:   1 2
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El día 01 Dec 97 02:33:50 , Simon Ellwood <> dijo:

>The inboard devices are known as Kruger flaps, whilst the outer devices
>are standard slats.
>Both devices increase lift by increasing the curvature and camber of the
>wing at the LE. However, when the slat is fully deployed, it leaves a
>slot between itself and the LE of the wing. This slot effectively
>accelerates flow over the wing LE, increasing the energy in the boundary
>layer flow.

I disagree. There is a subtle difference between slat and slot. Let me

1) A slot allows the aire from the lower region (which is at higher
pressure than the upper region) to flow to the boundary layer. The
boundary layer energy is thus increased, as you stated before.

2) A slat is an airfoil different from the main airfoil. It then
deccelerates the airflow under it -- that is, in the main airfoil's
upper surface, mainly at the suction peak. The main airfoil lift
DECREASES (this should be solved by the slat lift), but the adverse
pressure gradient over the boundary layer is snaller than it was. The
boundary layer can thus be attached more length.