On Jan 12, 9:30*pm, Eric Greenwell wrote:
On 1/11/2011 8:06 AM, Andy wrote:



My mean L/D is always much better than that. *I routinely make flights
of 150-250 miles with a net loss of altitude of *2000 ft or less.
That's an achieved L/D (if we want to persist in using that term out
of context) of about 450/1. *Pretty impressive for a standard class
glider. *The manufacturer only claims 44/1.

An extreme example of why just flying around doesn't yield very good
polar measurements.



Why do we want to continue using the terms L/D, *and best L/D, out of
context?

I do it out of habit, history, and continued use of the term by the
manufacturers and other pilots. I don't know why the manufacturers
continue to use it, but I'm going to guess: habit, history, and
continued use of the term by their customers.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "

I don't think the misuse has anything to do with manufacturers, if you
mean glider manufacturers. They use the term best L/D in its proper
context. The fidelity of the number is a separate discussion.

I think a lot of the blame for the misuse of "L/D" lies with SeeYou
flight analysis software. There are far too many people that believe
anything that appears on their computer screen.

In any case the knowledge of the glide angle achieved in any segment
of a flight is meaningless without taking into account the wind
velocity and average ground speed for the flight segment. If those
and the glider polar are known then something can be deduced about the
behavior of the air mass for that flight segment. Similarly if they
are known, and the air mass movement is known, then something can be
deduced about the glider polar.

So how about it SeeYou people. Can you please stop using the term "L./
D" out of context?

Andy