Too fast vs too slow

If you look at the lines on the bottom of this graph:
http://soaringcafe.wpengine.netdna-c...io-Polars1.jpg

You will see the glide ratio plotted versus the speed. For every speed this diagram gives you the glide ratio for that speed.

If you then look at the optimal glide point, that is the point where graphs reach their lowest point (the Y-axis is on the right for these graphs), you see that on both sides of this peak the line
has roughly the same slope. This leads me to conclude that it does not really matter, for this particular aircraft at least.

W dniu środa, 8 maja 2013 10:02:44 UTC+2 użytkownik Roel Baardman napisał:
If you look at the lines on the bottom of this graph: http://soaringcafe.wpengine.netdna-c...io-Polars1.jpg You will see the glide ratio plotted versus the speed. For every speed this diagram gives you the glide ratio for that speed. If you then look at the optimal glide point, that is the point where graphs reach their lowest point (the Y-axis is on the right for these graphs), you see that on both sides of this peak the line has roughly the same slope. This leads me to conclude that it does not really matter, for this particular aircraft at least.

Bad example - compare this polar with real Concordia performance from igc file ;-)

Your opinion would have been correct if the polar was a straight line, but it isn't...

Your opinion would have been correct if the polar was a straight line, but it isn't...

I was trying to say that, since the shape of the curve on both sides of the theoretical optimal point is symmetric, it does not really matter. Optimal +10kts gives roughly the same L/D as Optimal
-10kts.


Furthermore, I think John Cochrane hits the nail on the head here (again).

Roel

At 12:29 08 May 2013, Roel Baardman wrote:
Your opinion would have been correct if the polar was a straight line,
but it isn't...

I was trying to say that, since the shape of the curve on both sides of
the
theoretical optimal point is symmetric, it does not really matter.
Optimal
+10kts gives roughly the same L/D as Optimal
-10kts.


Furthermore, I think John Cochrane hits the nail on the head here
(again).

Roel


But the polar curve is not symmetric about the point of intersection with
the tangent that passes through the origin, ie the maximum glide - we're
not talking about min sink here.

Infact, I bet you will achieve a better glide ratio if you fly 10 knots
slower than best glide than 10 knots faster (in still air).

we're not talking about min sink here.

This sums up my error quite nicely. Thanks for correcting me!

I think we are all missing a big part of the equation...

How bad do you have to pee?

Boggs