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#1
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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 This means that wind data that depends on the glider flying circles gets way out of date during the long glides.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 |
#2
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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 This means that wind data that depends on the glider flying circles gets way out of date during the long glides.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 |
#3
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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 |
#4
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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 |
#5
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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 |
#6
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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 |
#7
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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 |
#8
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"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 |
#9
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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 |
#10
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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 |
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