"john smith" wrote in message
...
One of aviation's Rules of Thumb...
an approximate best approach speed is found halfway between the top and
bottom of the white arc.

It's certainly never going to kill you, but it doesn't make any adjustments
for being light (say 1 pilot, and minimal fuel) - which can make approx 13
knots difference to the ideal approach speed in the Arrow (and 10 knots
difference to your dirty stall speed).

Since I started calculating approach speeds I've been amazed at how the
consistancy of my landings has improved - even 5 knots makes a difference.