Glider down near Reno - pilot OK

"T o d d P a t t i s t" wrote in message
...
"bumper" wrote:

Since the GPS data displayed is base entirely on ground track, strong
winds
will skew those results. Consider crabbing into a 70+ knot wind. A change
in
wind speed, and thus ground track, will be displays as a roll on the
Garmin
panel page - - not so good if one is trying to survive some moments in
IMC.

It might make sense to head downwind before entering the
cloud and hold that heading if you were using GPS to
maintain level flight. It would produce less influence on
the ground track and a less drastic roll rate indicated as
compared to heading into the wind.
--
T o d d P a t t i s t - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)

True, this might be the best option if GPS is your only tool to get down.
However, in wave conditions in mountainous terrain, this might have our
hapless pilot in IMC, and flying towards the next unseen downwind obstacle
at blazingly high ground speeds (g).

bumper

T o d d P a t t i s t wrote:
"bumper" wrote:


Since the GPS data displayed is base entirely on ground track, strong winds
will skew those results. Consider crabbing into a 70+ knot wind. A change in
wind speed, and thus ground track, will be displays as a roll on the Garmin
panel page - - not so good if one is trying to survive some moments in IMC.


It might make sense to head downwind before entering the
cloud and hold that heading if you were using GPS to
maintain level flight. It would produce less influence on
the ground track and a less drastic roll rate indicated as
compared to heading into the wind.

My experimenting showed going downwind made the heading very insensitive
to turning (the opposite of going upwind, as you might guess). I suspect
this would be just as much a problem as the very sensitive situation
going upwind, but I haven't tried either in realistic situations.

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

Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...

My experimenting showed going downwind made the heading very insensitive
to turning (the opposite of going upwind, as you might guess). I suspect
this would be just as much a problem as the very sensitive situation going
upwind, but I haven't tried either in realistic situations.

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

Eric Greenwell
Washington State
USA

Eric,

I thought that too, but imagine downwind would still be a better than
upwind - - if all you had was a GPS to stay upright.

In strong wave conditions, as you know, the ship might be stationary over
the ground or moving in any direction relative to its nose. I've watched my
moving map go spastic trying to figure out which way to orient the display
while nosed into 70 knots. Up like an elevator . . . I love Minden!!

bumper

Just as an experiment, set your GPS to go to a local
feature, such as your clubhouse, and try walking backwards
away from it while holding the GPS unit. You will then
find that the 'compass' needle will tell you that the
feature is behind you!

No I didn't believe it either at first, but a friend
of mine flying sufficiently slowly in wave near the
Long Mynd site in Shropshire, England, as to back up
slightly relative to the ground, reported this precise
effect. He could clearly see the Mynd clubhouse in
front of him, but the GPS needle was telling him it
was in the opposite direction.

Remember that a GPS is not a compass and it tells you
what track you are making good, rather than which direction
you are pointing.

Not normally a problem I know, But it can become one
when you are flying into a very strong wind, as in
wave flying, and not moving over the ground, or even
going backwards.

Derek Copeland

At 02:00 13 November 2005, Bumper wrote:
'Eric Greenwell' wrote in message
...

My experimenting showed going downwind made the heading
very insensitive
to turning (the opposite of going upwind, as you might
guess). I suspect
this would be just as much a problem as the very sensitive
situation going
upwind, but I haven't tried either in realistic situations.

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

Eric Greenwell
Washington State
USA

Eric,

I thought that too, but imagine downwind would still
be a better than
upwind - - if all you had was a GPS to stay upright.

In strong wave conditions, as you know, the ship might
be stationary over
the ground or moving in any direction relative to its
nose. I've watched my
moving map go spastic trying to figure out which way
to orient the display
while nosed into 70 knots. Up like an elevator . .
. I love Minden!!

bumper

At 02:00 13 November 2005, Bumper wrote:
'Eric Greenwell' wrote in message
...

My experimenting showed going downwind made the heading
very insensitive
to turning (the opposite of going upwind, as you might
guess). I suspect
this would be just as much a problem as the very sensitive
situation going
upwind, but I haven't tried either in realistic situations.

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

Eric Greenwell
Washington State
USA

Eric,

I thought that too, but imagine downwind would still
be a better than
upwind - - if all you had was a GPS to stay upright.

In strong wave conditions, as you know, the ship might
be stationary over
the ground or moving in any direction relative to its
nose. I've watched my
moving map go spastic trying to figure out which way
to orient the display
while nosed into 70 knots. Up like an elevator . .
. I love Minden!!

bumper



I have tried flying straight using my moving map at
maximum scale and consider it just one step more practical
than screaming.

Remember that a GPS is not a compass and it tells you
what track you are making good, rather than which direction
you are pointing.

I've seen my moving map (Glide Navigator II) flip on me in high wind
(60+ kts) wave, showing the Gardner MA, USA, airport behind me when I
could see it in front of me. It's probably a difficult software fix and
not important enough to bother with.

Tony V
htth://home.comcasst.net/~verhulst/SOARING

Tony Verhulst wrote:

I've seen my moving map (Glide Navigator II) flip on me in high wind
(60+ kts) wave, showing the Gardner MA, USA, airport behind me when I
could see it in front of me. It's probably a difficult software fix and
not important enough to bother with.

At a guess changing the Glide Navigator map orientation setting from
Heading Up to North Up would do the trick. Same would work for almost
any PDA moving map system I should think.

--
martin@ | Martin Gregorie
gregorie. |
org | Zappa fan & glider pilot

Tony Verhulst wrote:

I've seen my moving map (Glide Navigator II) flip on me in high wind
(60+ kts) wave, showing the Gardner MA, USA, airport behind me when I
could see it in front of me. It's probably a difficult software fix and
not important enough to bother with.

I'd say an impossible software fix. All the GPS engine can do is detect
where it is, and hence which way it's moving. Since it's not a compass it
can't detect how it's oriented without additional hardware. As an obvious
illustration, try holding it upside down.
--
Real name is richard

The phugoid should have a stable amplitude (not diminishing) with stick
fixed, but not with stick free.

GPS heading is based on, obviously, your ground track (the GPS has no
knowledge of your airspeed or magnetic heading). If your ground speed
is low, or zero, (as may well be the case in wave) the GPS heading is
useless. The only way to get useful information is to speed up so that
the ground speed is, at least, a healthy fraction of the airspeed (say
25-50%). This, of course, means you are no longer "parked" in the wave
and are moving relative to the ground. In your crabbing scenario, a
wind speed change will lead to a change in your heading over the
ground. In IMC, the pilot will not know whether he rolled or whether
the wind changed, at least not immediately. If he rolled, however, the
heading will continue to change, while if the wind speed changed to,
and remainded constant at, a new value the heading will initially
change and then remain at the new heading. In both situations the pilot
can react be rolling the opposite direction and either:

1. correct the roll
or
2. commence a turn that returns the heading to the desired point.

A better solution for strong wave conditions is an artificial horizon,
which are now available in electronic form (although the power
consumption is somewhat higher than I would like). But GPS can still be
used for an emergency descent in IMC conditions, IF you keep your
airspeed significantly above the wind speed.

Tom