no instrument flight

wrote:
Eric Greenwell wrote:
...suppose you always flew gliders with a redundant altimeter that read
AGL? Would it be proper for the pilot to refer to this during landing?
Would he be safer overall, even if his "that looks about right" skills
faded a bit?

A lot of us have this redundant, AGL readout altimeter in our cockpits
already: it's a PDA running a program like SeeYou or Winpilot.

Eric,

The problem is, as always, with the "always". Most low time or student
pilots will probably not be flying in a glider equipped with a PDA - or
a glide computer, for that matter!

I don't think it's a good thing for student pilots, but how about the
licensed pilot flying cross-country? Would outlandings be safer if
pilots used the AGL information? I already do so to some extent, when I
use the "make waypoint here" feature over a good outlanding field, then
use that waypoint as my "target" for the glide computer.


In addition, while the PDA is a fantastic tool (I use MCU, with the AGL
navbox on all the time) it is also a serious "eye-magnet", and the last
thing a pilot should be looking at in the pattern! It should really be
used in the same way as the altimeter - at the IP (or equivalent) to
confirm the approximate height above the landing area, then once
commited to a landing, should be completely ignored.

That's the way I think it should be used. The big difference over an
altimeter is the PDA/moving map can indicate (fairly well) your AGL at
an uncharted farmer's field, and the altimeter can't.


Like drugs, all the fancy moving map displays have a big potential for
mis-use - there is so much neat information there, that it is a real
temptation (especially during "easy" phases of flight) to look at the
display and play with it, instead of looking out the window. One needs
to train oneself to only access the information when it is needed, and
to setup the displays so that important info is easily gained without a
lot of button pushing - otherwise it can be a real safety hazard!

Absolutely! Pilots should know the difference between "need to know" and
"just interesting" information. Of course, I had the same problem with
paper maps, rulers, and whiz wheel calculators, trying to figure out
where I was, how far away I was from a safe field, and if I could still
get there. A difference, perhaps, is I suspect pilots weren't likely to
pull out a paper map while in a gaggle, but they might be inclined to
punch a few buttons on their glide computers while in the gaggle.


--
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Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

Eric Greenwell wrote:
I don't think it's a good thing for student pilots, but how about the
licensed pilot flying cross-country? Would outlandings be safer if
pilots used the AGL information? I already do so to some extent, when I
use the "make waypoint here" feature over a good outlanding field, then
use that waypoint as my "target" for the glide computer.

I've been working with digital terrain elevation data since the mid-80s.
There are noticeable errors in some of the publicly available source
data. Fitting data for a usable area into the memory available in a PDA
requires a reduction in resolution. One also needs to consider the
possibility of significant GPS altitude errors. This data is fine for
drawing maps and getting a general idea of the height of the terrain,
but, in my opinion, depending on it for flying a pattern into an
unfamiliar field would be a mistake...

Marc

Marc Ramsey wrote:
Eric Greenwell wrote:
I don't think it's a good thing for student pilots, but how about the
licensed pilot flying cross-country? Would outlandings be safer if
pilots used the AGL information? I already do so to some extent, when
I use the "make waypoint here" feature over a good outlanding field,
then use that waypoint as my "target" for the glide computer.

I've been working with digital terrain elevation data since the mid-80s.
There are noticeable errors in some of the publicly available source
data. Fitting data for a usable area into the memory available in a PDA
requires a reduction in resolution. One also needs to consider the
possibility of significant GPS altitude errors. This data is fine for
drawing maps and getting a general idea of the height of the terrain,
but, in my opinion, depending on it for flying a pattern into an
unfamiliar field would be a mistake...

Marc is quite correct, and I should have mentioned I usually add 500
feet to my reserve to mitigate the problems he mentions; also, I
normally use it over relatively level terrain where the 2D resolution
wouldn't be important, and it's been accurate enough. I don't exactly
use it to fly a pattern, but just to get me back to the field high
enough to set up a pattern in the usual fashion - "that looks about right".

Now I'm curious about the accuracy of the terrain data used in my pda,
which runs SeeYou Mobile. I know SeeYou itself uses "relatively
accurrate" data now after the change (last year?) to data downloaded
from the Internet as needed, and SeeYou's terrain data is used to
produce the terrain data for the pda.

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

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"