Flight Polars for Grob 102

[John Murphy]

I've got a Grob 102 Standard Astir III. The manual that came with the
plane has one flight polar diagramed. The diagram contains flight
polars for 3 different configurations of the G102. Because so many
lines are drawn in close proximity to each other, its not a diagram
that can be used for calculating speed to fly. Does anyone know have a
clean flight polar for the 102 Standard Astir III being flown without
ballast, or know where I could get one? Thanks, John Murphy.

[[email protected]]

John,

When I needed polars for my Ventus 2C a couple of months ago (15M and
18M), the only ones I could find were those in the SeeYou Polar tool.
They seem to work fine (I use them in my LX7000 and WinPilot), but I'm
still curious about where the SeeYou team got them, since the V2C's 15M
polar is identical to the ASW-27's in their list.

Anyway the polar indicated for the "G102 Club" (the only 102 in the
list) is: at 30 kg/m2, stall speed 39 knots, best L/D 33: a = 1.69, b =
-2.03, c = 1.22.

If you want to see a graph you can download LXe at LX Navigation's web
site and use its polar tool.

~ted/2NO

[Eric Greenwell]

John Murphy wrote:
> I've got a Grob 102 Standard Astir III. The manual that came with the
> plane has one flight polar diagramed. The diagram contains flight
> polars for 3 different configurations of the G102. Because so many
> lines are drawn in close proximity to each other, its not a diagram
> that can be used for calculating speed to fly. Does anyone know have a
> clean flight polar for the 102 Standard Astir III being flown without
> ballast, or know where I could get one? Thanks, John Murphy.

Precision isn't needed to have a useful result, as flying 5 or 10 knots
off the "perfect" speed hardly affects the theoretical cross-country
speed. Generally, people fly slower than the "ideal" speed anyway so
they don't get low so quickly and have more opportunity to find a good
thermal. Good thermals is what gives you the good cross-country speeds.
Be sure to read Reichmann's book if you haven't already.

So, picking points off the chart you have will be fine, or using a polar
from a similar glider will work just as well.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA