Glide distance vs. weight

Take several aircraft at the same altitude. Make it a B-52 H since it can
carry over 300,000# of fuel so it can vary considerably in weight. Make one
weigh 300,000#, another weigh 400,000#, and a third one weight 500,000#.
The heavier the aircraft, the more energy it took to get it to that same
altitude but once it's there and the engines are shut down the heaviest one
has more potential energy (due to its greater weight affected by gravity).
The heaviest aircraft would have a much higher driftdown speed than the
lightest one and would reach the ground sooner than the others. It's higher
speed would induce more drag so that would counter the greater energy
available due to the greater weight. In no wind conditions all 3 should
glide the same distance. The lightest one would stay aloft longest but at a
slower driftdown speed producing the same glide distance. The driftdown
vertical speed of the heaviest would be the highest. It would travel across
the ground faster than the others... but for a shorter period of time.

Throw in a wind and you dramatically change things. Gliding into a headwind
the heaviest aircraft will glide the furtherest since it's effected by the
headwind a shorter time. Gliding with a tailwind the lightest aircraft will
glide the furtherest since it glides for a longer time thereby using the
most tailwind assist.

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
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"news.mcgraw-hill.com" wrote in message
...
During a review of the V-speeds for an airplane I've never flown before,
my
instructor asked me about glide speed vs. weight, and total glide
distance.

I got the glide speed vs. weight part right, but the distance part seemed
counterintuitive - that the total distance covered (by flying at the
correct
best glide speed for the weight) would be the same, regardless of the
weight.

Can anyone explain this so that it makes sense?