Electronic horizon?

In absence of more suitable instrument and/or rating, couldn't a GPS or PDA
with moving map be used to descend through clouds in emergency by zooming in
and noting if and what direction the glider is turning?

Ramy

"Bill Daniels" wrote in message
...
There are several PDA based 'glass cockpit' software packages that appear
to
work well. They derive bank attitude from TAS (or GS if TAS is not
available) and the rate of change of ground track. Pitch data is derived
from the rate of change of airspeed. 'Heading' is actually ground track
but
that is good enough.

Since many glider pilots already have a PDA in the cockpit, these might be
good enough for an emergency. Simply have the 'glass cockpit' running in
the background and switch to it if the need arises. The beauty is that no
additional hardware is needed beyond what is already in the glider.

FWIW, I tried a simulated 'blind let down' using only the wet compass in
the
back seat of a G103. With the glider on a southerly heading, I used the
southerly leading error to keep the wings level and hold the heading. I
was
able to do this for about 10 minutes under the 'hood' without outside
reference.

For those readers not aware of this trick, a magnetic compass senses not
only the N-S magnet field but also the 'dip' angle. While on a southerly
heading in mid northern latitudes, the magnetic compass will indicate a
turn
as soon as a wing is down and before a turn actually starts. Banking the
glider left and right as needed to keep the compass on S will keep the
wings
level. This is very tricky in a fast airplane but surprisingly easy in a
slow glider as long as the air isn't very turbulent. (For out friends in
the Southern Hemisphere this trick requires a north heading.)

Bill Daniels


"Martin Gregorie" wrote in message
news
On Thu, 25 Aug 2005 20:53:43 -0700, rhpf wrote:

Martin,

I have flown with this instrument, it works well. It will tumble after
several minutes of extreme bank angles. Even higher priced instrument
in
the $3000 to $5000 range have a cage function for acrobatic maneuvers
or
extreme bank angles.

This instrument group is one that I'd almost never use during normal XC:
the reason I'm looking is that when/if I do some wave flying I'd like to
have these displays onboard in case of canopy icing and/or finding
the slot slammed shut below me. Would you trust it for that? I'm asking
because I've heard stories that continuous circling would tumble it.

--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |