"Marc J. Zeitlin" wrote in message
...
Gliders, of course, are much higher - up to 50:1, or even
better.

The 31 meter span ETA is reported to have an L/D of about 75:1. These
extremely large wingspan gliders are very hard test for L/D since tiny
vertical motions in the atmosphere create too much noise in the data.

In any event, whether the glide path rises or falls is far more likely to be
caused by atmospheric motions than by the glider's performance. They are as
close to perpetual motion machines as has been developed.

Bill Daniels