I must differ with respect to Flap 10 increasing range in a glide!!!!
Flap selection changes the lift:drag ratio adversely. This in turn REDUCES the glide range of the aircraft.
Easily demonstrated by flying straight & level at whatever speed requires minimum power (min thrust to be precise but harder to find easily in a piston type), & then selecting flap. You will need more power to maintain S&L. This because there is an increase in drag -ie a reduction in lift:drag ratio
NOTE: Very, very calm/smooth conditions are best for this
This IAS can be found by maintaining S&L & gradually reducing power a bit at a time, wait until IAS is stabilised & then reducing again.
Eventually you will not be able to maintain a constant IAS without descending.
After stabilising at this just found min. pwr S&L IAS, select 10 deg flap. You will need more power to maintain S&L flight. If in doubt repeat with the next flap setting.
The definitive proof is to look at a set of Lift/drag curves with & without flap. They very clearly show an adverse effect.
BTW: If it was correct that flap selection increases the glide performance, then this would also mean selecting flap to maximise cruise range
[This message has been edited by Tinstaafl (edited 05 May 2000).]