OK, David, I hope you are right.

However, if the computer doesn't know the glider's heading, how does it
solve the wind triangle without turns? If the computer can't solve for the
true wind data how can it compute the headwind component?

People keep telling me that TAS + or - Groundspeed will give a "good enough"
headwind/tailwind component. My experience is that the wind data gets very
stale during a long final glide.
After a few circles to get fresh wind data, the final glide numbers look a
lot different. If the wind shifts or I descend through a wind layer, I need
to know it RIGHT NOW.

Bill Daniels




"David Starer" wrote in message
...
Bill,

Sorry to disagree but a quick calculation shows that if you glide at 70
knots in a 35 knot 90 degree crosswind, you will experience the equivalent
of about 8 kts headwind component. This is the figure you would have to
feed
into the calculation to find the height needed to complete your final
glide.

David Starer

"Bill Daniels" wrote in message
news:An0Ac.50845$0y.34865@attbi_s03...
Partly true. If you have a 35 knot 90 degree crosswind, the wind
component
along the final glide path is zero. However the penalty for crabbing
into
that crosswind to maintain your course to the finish line is
significant.

My concern is mountain flying. Mountain winds tend to change a lot in a
short distance. The sooner you know of a wind shift the easier it is to
take advantage of it. I still want highly accurate real-time wind data.

Bill Daniels

"David Starer" wrote in message
...
For calculating a final glide, you only need to know the wind
component
along the final track; it isn't actually necessary to know the
absolute
wind
strength and direction. The difference between true airspeed
(corrected
IAS)
and ground speed (from the GPS) is equal to the component you need, so
the
glider's heading isn't required.

David Starer

"Bill Daniels" wrote in message
news:gw%zc.59643$HG.25574@attbi_s53...
I've been analyzing the IGC files from my flights and comparing them
to
others.

Generally, in good conditions, I'm circling less than 25% of the
time.
Other, far better pilots than I, are circling less than 15% of the
time.
This means that wind data that depends on the glider flying circles
gets
way
out of date during the long glides. OK, "S" turns can give the
computer
a
chance to compute wind if you remember to fly them but there are
still
a
lot
of long, straight glides.

To compute real-time wind data we need Groundspeed, Ground Track
(any
GPS
gives these)True Airspeed (Some computers do this if they have OAT,
Pressure
Altitude and IAS) and accurate heading data. Heading data it the
tough
nut
to crack.

So, how do we get Heading? One way might be to put a GPS antenna in
each
wing and look at the carrier phase difference. If the computer saw
a
constant track, it could assume the wings are level and determine a
heading
value. This heading value might update an aerospace quality MEMS
heading
gyro that would maintain a flow of heading data to the glide
computer
during
times when the wings were banked.

With good heading data we could get uninterrupted high quality wind
data
regardless of the gliders' maneuvering or lack of it.

OK, RAS gageteers, how about it?

Bill Daniels