>>
Of course even when the flap is retracted, some air will find its way
up thru the gap between the leading edge of the flap and the vertical
face of the wing closeout, and it is this airflow which one wants to
eliminate in order to enhance cruise efficiency.
If this is so, it would seem that another way to get this increase in
cruise efficiency might be to install a compressible strip which would
close the gap when flaps are retracted but allow airflow over the flaps
when they are deployed, thus maintaining the short field
characteristics of the aircraft which, if I understand you correctly,
have been changed. <<
Adding compressible strips in the flap closeout was suggested to me some
time ago by a person with many years of aeronautical design experience.
The key is to close the airflow from lower to upper surface during
cruise but to ensure that the lower to upper airflow over the flap
remains per the design spec when the flaps are down.
This is quite easy to achieve by adding some light doorstop strip into
the flap closeout and, in many cases, will have already been achieved on
the port side if the pitot/static lines were run in the flap closout as
part of a retrofit.
Tony
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