Re: Leading Edge fences

Date:         28 Sep 97 20:59:09 
From:         luisma@spainmail.com (Luis Manuel Perez Llera)
Organization: Unisource Espana NEWS SERVER
References:   1
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El día 08 Sep 97 02:03:41 , baejs3201@aol.com (BAEJS3201) dijo:

>Hey out there can anyone answer a question for me??? I've noticed that
>aircraft with aft mounted engines(727,DC9/MD80 and maybe Fokkers)have what
>looks like a fence on the leading edges of the wings. Is this to straighten
>the airflow for the engines????

The old French aircraft Caravelle mounted big fences in the leading edge
covering more or less half of the upper surface and one-third lower
surface.

The reason to install the fences was to avoid the lateral sweep of the
airflow.  This sweep caused the boundary layer to separate nearer the
leading edge as we move through the wing span (if the boundary layer
separates, say, at 90% chord at the fuselage junction, the separation
could occur at 60% chord at the wingtip).

This causes the aileron to be absolutately inside the separated airflow,
thus no lateral control is achieved.

Excuse my bad english.