http://w3n-a.blogspot.com/2008/11/de...-airspeed.html

Too fast a glide during the approach for landing invariably results in
floating over the ground for varying distances, or even overshooting,
while too slow a glide causes undershooting, flat approaches, and hard
touchdowns. A pilot without the ability to recognize a normal glide
will not be able to judge where the airplane will go, or can be made
to go, in an emergency. Whereas, in a normal glide, the flight- path
may be sighted to the spot on the ground on which the airplane will
land. This cannot be done in any abnormal glide.

http://w3n-a.blogspot.com/2008/11/de...-airspeed.html