Gageteers, we need a digital heading sensor

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out of date during the long glides.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

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out of date during the long glides.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

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

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

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

Bill Daniels wrote:
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?

The "headwind" = TAS - (Ground speed). It's the "effective" headwind
along your course (GPS ground track), not the actual headwind on the
glider's heading.


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.

Yes, and a way to handle in some glide computers is to manually update
the wind value in use, using the measured "effective" headwind.

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.

The effective "headwind" seems to do this quite well, based on my
experience with a 302 and Glide Navigator (GN). GN also displays the
error between the effective headwind and the headwind calculated using
the last vector wind determination. If the error is more than a knot or
two, I know the vector wind has changed.

Of course, knowing it's changed doesn't tell you what it is, but once
alerted, I can circle or deviate my course to pick up the new vector
wind. For mountain flying, I'm often turning frequently anyway, so it
hasn't been the problem that the long straight glides in the open
sometimes are. Still, having an update to the vector wind every 20
seconds or so would be a nice.

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

Eric Greenwell
Washington State
USA

Todd Pattist wrote:

"David Starer" wrote:


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.


1) It's not at all unusual for me to be high enough to final
glide to a TP, then turn and glide home. I need more than a
component of the wind to figure out if I can make it to the
TP and then home.

If the wind is changing along your course, knowing it accurately right
at the moment probably won't help much. You'll still be guessing about
the wind along the rest of the course, 10-20-30 minutes later. I suggest
using the headwind component for the entire final glide.


2) To figure out which of five potential airports in the
area you can safely get to with maximum remaining altitude
needs more than the wind component along your current glide
path.

Since you can easily make the turnpoint, this won't be an issue until
you reach it. When you make the turn at the turnpoint, the computer
will update the vector wind. This should improve the glide calculations
to your safety airports. If you have head for one, you can go back the
headwind value to improve the calculations.


3) I'm gliding down to the ridge from thermals and expect to
arrive low over relatively poor landability terrain. I'd
really like that real time wind speed and direction to
comfort my fearful heart as I dump off precious altitude and
descend to the ridge.

I think this is the kind of short term (a minute or two) situation -
getting close to the ridge where you either need to turn away or
continue - that wind updates every 10-20 seconds would be useful. The
other situations involved long (30-40 minutes) glides during which the
wind could change several times.

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

Eric Greenwell
Washington State
USA

"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


This is only true if you can wait for the solution until you are
established on the final glide from the last turnpoint. Most of us
want the solution before rounding the last point, or perhaps even
before the last several turnpoints if working close in points to use
up a good last thermal on a MAT or PST. The wind direction and
magnitude are both required to derive that solution.


Andy

Bill - The heading is not required. In the ILEC SN10 we do this
without heading, and it normally has the wind by the time you're
off tow. Pilot feedback and measurements indicate that we do
it quite accurately. We just use TAS and GPS ground track over
multiple observations (TAS requiring accurate IAS, press, temp).
Best Regards, Dave "YO"

"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

Dave, can it give highly accurate, real-time wind data, second by second on
a straight one hour glide?

My last flight showed this problem during a long glide. For 30 miles the
wind data showed SW winds at 20 knots but then I noticed the glider drifting
to the west. Two 360 turns and the computer showed wind at 090 at 10 knots.
When I crossed the wind shift line I had a chance to change strategy. 30
miles later when the wind error became obvious it was too late.

More and more I think we need very accurate real-time wind data with no
requirement to be constantly changing heading. A cheap, reliable heading
sensor would make this possible.

Bill Daniels

"Dave Nadler YO" wrote in message
m...
Bill - The heading is not required. In the ILEC SN10 we do this
without heading, and it normally has the wind by the time you're
off tow. Pilot feedback and measurements indicate that we do
it quite accurately. We just use TAS and GPS ground track over
multiple observations (TAS requiring accurate IAS, press, temp).
Best Regards, Dave "YO"

"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