Posted for Bill Hogarty <billhogarty@direcway.com>:

 Marv:
 
 Hope you will post some of the rationale for the flap fences. .  I find them
 very interesting but dont know anything about them.  Would like to get
 educated.  thanks,  bill Hogarty
 


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The fences were originally tested on both ailerons and flaps of heavy aircraft in an effort to try and reduce some of the noise the turbulent airflow at the extremes of the surfaces produced.  They did that job and, in the process, it was found that the surfaces also gained authority.  By containing the airflow and not allowing it to spill up around and over the ends of the control surfaces (ie, create vortices) the effectiveness of the surface was enhanced. (This is my recollection and I'm paraphrasing, so please don't jump me for inaccuracies <G>... I'll get the report number when I go back to the hangar and pass it along so you can read it yourself and reach your own conclusions.) Anyway, it didn't require much time or effort to engineer & install them, so we thought they were worth a shot.  They're basically 6-BID CF flat plates... the inboard one bonded onto the flap's end , and the outboard one installed in a slot... they are aligned with the aircraft's longitudinal axis.    If they do what was reported and help lower the stall speed by even a knot we'll have won.  We're hoping for more.   <marv>
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