On Aug 23, 12:20*pm, Andy wrote:

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?

That goes back to the 50s, very likely. Certainly, it was used on
circular slide rule calculators of the 60s (referenced in Sunship Game
and articles of the era). L/D *is* a little easier to say than "the
inverse of the tangent of the flight path angle", even if it *is*
extremely sloppy shorthand.

-T8