Flap Settings

Ken Kochanski (KK) wrote:
I understand, a wing will perform optimally when the flap is set at
the proper angle for the airspeed ... any mismatch of flap to airspeed
will result in some performance losses vs. the correct setting. Of
course, we have a couple of compromises here ... the flaps are set at
fixed increments and the airspeed varies continuously ... so by
design, you will rarely have the flap and airspeed matched up
perfectly.

I remember seeing a story where one of the German schools modified an
LS-3 with springs, etc. so it automatically put in the correct amount
of flap for the airspeed ... did this result in a measurable
improvement?

Along the same lines, I have heard some pilots say they put the flap
in a position where they feel no pressure ... does this work?

I myself tend to go negative quicker or maintain a negative setting
longer ... then pulling in positive flap ... thinking being too
positive is more costly then too negative ... is this valid?

Its well worth digging out Dick Johnson's reports on flapped gliders and
looking at the combined polar he plots - the one showing polars for all
flap settings.

The polars for the ASW-20 blend quite nicely except at the ends of the
speed range for each setting and the available speed range gets smaller
for each setting at more positive settings. The implication, I suppose,
is that selecting the right flap is more critical at lower airspeeds.

The same may apply to other gliders too: I haven't looked.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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