Glider computers - what's important?

Eric, it's a matter of laying all options on the table. I have found that
GPS_LOG WinCE showed options that I would not have otherwise considered. It
wasn't a mater of not being able to compute (or estimate) all options, but
of being too focused on the flight plan to see them.

An example is a flight where it had become clear that I wasn't getting home
so the task became getting as close as possible, landing at a convienient
airport to reduce the retrieve distance. Playing back the IGC file on
SeeYou with output to the PDA showed that for about two minutes I had a safe
glide to an airport that would have cut the retrieve by 200 miles of
mountain driving. During those two minutes, I was distracted and didn't see
the option. If I had a glide footprint display, it would have been too
obvious to miss.

A moving map with a glide footprint display is very easy to interpret so I
won't miss good alternatives again. I will never fly without it again even
though I own licenses for Glide Navigator II and WinPilot. If I use those,
it will be on a second PDA showing only the data boxes.

A "glide footprint" shows clearly how to cross a mountain range since it
computes glide distance in all directions. The courseline may happen to
cross the range at a high peak so a list type display will show the goal as
unreachable but the "glide footprint" will show that a slight change in
course will easily clear the terrain.

There is also the case where known lift is available in the distance -
perhaps from good clouds or from radio chatter coming from other pilots. If
this area isn't near an airport, list displays aren't useful. With a glide
footprint it's easy to see when the lift is reachable. Then there's
landable terrain that isn't in the airport database. Just knowing that good
landout options are reachable reduces stress and allows the pilot to
concentrate on the task.

It answers at a glance the question of, "Where can I go from right here,
right now at the current McCready setting?" For everyone who has watched a
simulation of a glide footprint display, there's a big "AHA!" moment.

Bill Daniels


"Eric Greenwell" wrote in message
news:SmgIh.11700$ig.1130@trndny01...
An "ide footprint"? That was supposed to be "glide footprint"!


--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Bill Daniels wrote:

A "glide footprint" shows clearly how to cross a mountain range since it
computes glide distance in all directions. The courseline may happen to
cross the range at a high peak so a list type display will show the goal as
unreachable but the "glide footprint" will show that a slight change in
course will easily clear the terrain.

I can use that feature!


There is also the case where known lift is available in the distance -
perhaps from good clouds or from radio chatter coming from other pilots. If
this area isn't near an airport, list displays aren't useful. With a glide
footprint it's easy to see when the lift is reachable.

Actually, this is something I've really wanted, but hadn't thought about
how a glide footprint would help.

Then there's
landable terrain that isn't in the airport database. Just knowing that good
landout options are reachable reduces stress and allows the pilot to
concentrate on the task.

I reduce my stress by carrying an "iron thermal"! But your other points
are well chosen, and I like the idea. I've informed SeeYou it's now on
my wish list.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric Greenwell schrieb:

landable terrain that isn't in the airport database. Just knowing
that good landout options are reachable reduces stress

I reduce my stress by carrying an "iron thermal"!

Dangerous tactic. Your personal thermal may or may not work.

"Stefan" wrote in message
. ..
Eric Greenwell schrieb:

landable terrain that isn't in the airport database. Just knowing that
good landout options are reachable reduces stress

I reduce my stress by carrying an "iron thermal"!

Dangerous tactic. Your personal thermal may or may not work.


Actually, Eric flies an ASH26E, so his "iron thermal" is the indescribably
smooth and reliable Wankel rotary engine. It always works :c)

bumper
ASH26E
Minden

Stefan wrote:
Eric Greenwell schrieb:

landable terrain that isn't in the airport database. Just knowing
that good landout options are reachable reduces stress

I reduce my stress by carrying an "iron thermal"!

Dangerous tactic. Your personal thermal may or may not work.

It doesn't have to be perfect to be a stress reducer! I always have a
good field in easy reach before I attempt to start; so far, only one
failure to start out of 165 in-flight restart attempts. That's a lot
less stress than 164 retrieves.

For a detailed look at how I use the "iron thermal" it's advantages for
the pursuit of soaring, read my "Guide" - see below for the download link.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric Greenwell wrote:

Bill Daniels wrote:

A "glide footprint" shows clearly how to cross a mountain range since it
computes glide distance in all directions. The courseline may happen to
cross the range at a high peak so a list type display will show the goal as
unreachable but the "glide footprint" will show that a slight change in
course will easily clear the terrain.

I can use that feature!

Use GPS_LOG WinCE. It has it.

Henryk Birecki

Hi,

Use GPS_LOG WinCE.

I do.

It has it.

Can you enlighten me on on how the footprint is computed?

Just by looking in a few directions, determining the "points of impact" in
those directions and connecting them? Or is it more complicated?

Would a single mountain on a vast plane look like an island in the glide
footprint?

Ciao, MM
--
Marian Aldenhövel, Rosenhain 23, 53123 Bonn
http://www.marian-aldenhoevel.de
"Success is the happy feeling you get between the time you
do something and the time you tell a woman what you did."

"Marian Aldenhövel" wrote in message
...
Hi,

Use GPS_LOG WinCE.

I do.

It has it.

Can you enlighten me on on how the footprint is computed?

Just by looking in a few directions, determining the "points of impact" in
those directions and connecting them? Or is it more complicated?

It simply looks in 48 directions around the compass and computes the maximum
glide in each direction considering wind, polar, McCready, balast and bugs.
It terminates each glide at the 'safety altitude' you have selected. It
then connects these glide termination points with a line that forms a 48
sided polygon. It does this about once a minute.

Would a single mountain on a vast plane look like an island in the glide
footprint?

A single isolated mountain on a plain would be a "notch" in the polygon, not
an island. If you know the terrain, it's obvious that you can glide around
the mountain and land in the notch on the other side.

Bill Daniels

On Mar 12, 5:08 am, "Bill Daniels" bildan@comcast-dot-net wrote:

It simply looks in 48 directions around the compass and computes the maximum
glide in each direction considering wind, polar, McCready, balast and bugs.

Plase confirm this function uses current MC. I browsed the on-line
manual and I thought it said ZERO MC which is not the implementation I
would want.

Is anyone using the terrain functions on an Aero 1550? If so is
performance adequate?

thanks

Andy

"Andy" wrote:

On Mar 12, 5:08 am, "Bill Daniels" bildan@comcast-dot-net wrote:

It simply looks in 48 directions around the compass and computes the maximum
glide in each direction considering wind, polar, McCready, balast and bugs.


Yes it does. 48 seemed like a good compromise between computation time
and "precision". This could be made a user input parameter in future
editions if there is a general concensus that it would be useful.

Plase confirm this function uses current MC. I browsed the on-line
manual and I thought it said ZERO MC which is not the implementation I
would want.

You are right about documentation. I will need to check in the code.
It may well be ZERO MC as it is a "safety" feature. If you are looking
for a safe place to land you want to fly at best glide angle, not best
time. Anyone would like to comment?


Is anyone using the terrain functions on an Aero 1550? If so is
performance adequate?


I am. I have not seen any problems so far, and I usually do fly in the
mountains.

Henryk Birecki