On Aug 23, 7:00*am, John Cochrane
wrote:

If you must think about glide angles, the right units are D/L not L/
D. *L/D goes through infinity when you run in to lift. D/L (feet per
mile, meters per kilometer) does not.

No expression using the terms lift and drag is appropriate for
defining a ground referenced flight path angle.

The proper term is, surprise, flight path angle. It has been used in
the aerospace industry for many, many, years. It has a range +/- 90
degrees. Required FPA describes the required geometry to reach the
goal and instantaneous FPA will descibe the current glider flight path
accurately whether climbing or descending.

Required and instantaneous FPA are just as easily calculated as the
incorrect term L/D or the misleadingly named term "efficiency".

Where did the use of L/D (the ratio of lift to drag) to describe a
ground referenced flight path angle originate? I know it has been
perpetuated by SeeYou, but did they start it?

Andy (GY)