On Aug 23, 8:17*am, akiley wrote:
On Aug 23, 12:32*am, Darryl Ramm wrote:



On Aug 22, 7:10*pm, akiley wrote:
[snip]
Required L/D to target tells you what you need to achieve. It makes no
sense to fold wind into that, its just the distance divided by the
difference in height. Achieved L/D tells you what you are getting
obviously with wind affects as well, all without any assumptions about
polars, mass, bugs, or wind. That is the beauty of working with L/D
required and achieved.

This is a good point, but since wind isn't factored into required L/D,
you don't know what your achieved L/D is unless you turn around and
head back to the airport. *But it does seem to be safer and more
straight forward. *And I suppose since you are always aware of the
winds, you can make a fairly accurate guess as to what you achieved L/
D is likely to be. *If it's a straight headwind home at 5 knots, I
could just mentally modify what I expect to achieve.

Again the L/D required is a statement of fact (as long as your
altitude and the destination elevation are accurate. It's beautiful
for it's simplicity. It also relates directly to the glide angle (OK
Andy) and you should develop eyeball skill for that over time.

Now its clearer where you are at, I would recommend at this stage of
your flying, where you are just taking steps away from the home
gliderport, to use the PDA calculated arrival height (above a safety
margin, with bugs factored -- in SeeYou Mobile if you want higher bugs
than 30% then you will need to modify the polar parameters). And that
arrival height will give you a safety margin that you can probalby
best relate to.

I suspect what John is talking about with Mc is too much for a new,
pre-XC pilot, it is probalby easier to work with what is likely to be
a more intuitive understanding of arrival height to start with. Then
I'd add the L/D metrics to get a feel for those (esp. as a sanity
check since they don't rely on computations) then maybe move up to
thinking more about the Mc stuff as you worry about XC performance and
develop a feel for what a Mc margin means.

How you are getting the wind calculation? As mentioned by others if
you don't have reliable wind data then worrying about factoring in
wind data may be irrelevant or worse. If you are hand entering wind
data that you trust that is great (all soaring software users knew how
to do that or at least how to reset suspect overly optimistic winds).

What Mc do you actually fly at? And how do you do this? For starting
off I would leave the Mc you actually fly at (i.e. your average
airspeed) low and don't try chasing the speed to fly (STF). Even if
you have a real STF computer that can calculate a reasonable STF there
are technical arguments about why its not as efficient as it might be,
but for a newer XC pilot overly chasing the STF is just a distraction
and especially may make it hard to find lift, estimate whether to take
a thermal, find blue convergence/energy lines etc. And don't try to
closely follow the STF Navbox on SeeYou Mobile, it just cannot
calculate that anything that useful from altitude (GPS or pressure)
data.

---

The PDA software is just a help, like other say, its a moving
sectional chart and a way to reduce calculations you would otherwise
do in your head, with a glide ruler or on a prayer wheel. Often a good
exercise to construct a glide ruler and hand draw some glide circles
on a sectional with different winds factored in. Doing that by hand
for where you fly should gives you a good feel for wind effects -- see
the ruler template at http://www.gliderbooks.com/downloads.html and
instructions in his Glider Pilot's Handbook of Aeronautical Knowledge
book. Just like getting a sectional and marking down landing options
also helps, "flying" to those in Google Earth or visiting them in a
power aircraft really help but there is something beautifully simple
and very tactile about pen and paper that seems to help people really
get a fell for things. GlidePlan (http://www.glideplan.com) can also
do this for you on a Mac or PC but doing by hand at least once is
probably a good idea.

But even better than asking on r.a.s. can you find a local
accomplished XC pilot(s) who can mentor you on all this stuff?

Yes, my club has several and I'm talking to them too. *It's also funny
about gadgets in aircraft. *My feeling is learn to use the autopilot
and whenever you can, learn navigators using simulators. *Half
learning electronics is the most dangerous in my opinion. *I enjoy
navigators, but I'm strict as to when and how to use them.

Compared to power XC flying you are much more dependent on all the
subtleties happening outside the glider, so try to get the PDA into
the background and focus on finding lift, working thermals, finding
energy lines, flying smoothly and efficiently. You can learn a lot
just flying triangles around a local gliderport and just keep stepping
up what you do. There are lots of ways to skin a cat, but if somebody
skilled is willing to mentor you it is worth following the way they do
things so you can more easily learn from them.

If you know of any bugs in SeeYou Mobile, please report then to
Naviter.

Darryl