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#41
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required LD versus required MC to make it home
On Aug 24, 5:16*pm, Darryl Ramm wrote:
On Aug 24, 5:06*pm, Ramy wrote: On Aug 24, 2:54*pm, mattm wrote: On Aug 24, 4:44*pm, Ramy wrote: On Aug 24, 1:11*pm, mattm wrote: Reichmann points out that MC 1 is a better setting if you are in desparation mode, because you give up only a little glide distance but you get to sample more air in a given time. Are you sure about that? MC=0 will give you more time and more air to sample (beeing the best L/D speed) than MC=1. I always use MC=0 when I switch to survival mode unless I am also battling significant head wind. Ramy Yes, it's true. *It's on the last page of this paper:http://www.dragonnorth.com/djpresent...training_for_c... "A lot of pilots flew and fly unnecessarily low average speeds when they get low, because they are anxious and fly with a zero setting. They don’t know that with a setting at 1 knot they have almost the same glide angle and lose much less average speed in case they recover and complete the task." In my plane (ASW-19) MC=0 speed is 53kts, and L/D is 38:1. MC=1 speed is 61kts, and L/D is 35:1. *Granted my sink rate is about 30fpm faster, but I'll have almost 20% greater range to find that thermal I need to get back up again. -- Matt Matt I'm afraid you missunderstood Reichmann comment. He claimed that you will lose less average speed with MC1 which is true. But you will not gain 20% greater range. On the contrary, Your search range will always be less if you fly faster than MC=0 (unless you have significant head wind which requires flying faster than best L/D). Bottom line, as other pointed out, it all depends on your goal. If you are flying contest, in which every second counts, then flying correct MC is important. If you fly for OLC or distance, like I believe the majority of XC flights are, and your main objection is to make it back home at the end of the day (as the subject lline says), than fly *MC 0 when you are in survival mode or starting your final glide. Ramy But, but, but, (and I think I can hear John Cochrane pounding his head on his desk in Chicago...) when about to go on final glide and you are in that last thermal you know what the theoretical final glide Mc should be. And by all means factor in safety margins but if you have a climb significantly over your Mc="0" value then keep climbing and bump the Mc appropriately to match that climb. I mean why not? I know sometimes pilots like to float past the home airport and stretch a few more OLC miles then turn back. Personally the call of that cold beer makes me want to fly that final glide as fast as possible. What is really annoying about arguing with Ramy on this point (which I think I've done before) is no matter what I can argue on paper I have no hope of keeping up with him in practice. Sigh Darryl- Hide quoted text - - Show quoted text - Funny, I guess I can fly better than I can explain myself :-) All I am trying to say about the final glide is that if you are not competing (or competing against the sun as in my case sometimes) the exact speed you fly on your final glide wouldn't matter much. And instead of dialing MC according to your last climb to determine when to leave the thermal and then ignore this MC on your glide if you want to ensure you get back home even with no lift, just degrade your polar instead, climb as high as you feel comfortable, then fly as fast as you can without loosing glide. Simple. Of course while on course and high crank up the MC as high as you dare, just make sure you stay in the desired lift band. But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Ramy |
#42
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required LD versus required MC to make it home
On Aug 24, 9:32*pm, Ramy wrote:
On Aug 24, 5:16*pm, Darryl Ramm wrote: On Aug 24, 5:06*pm, Ramy wrote: On Aug 24, 2:54*pm, mattm wrote: On Aug 24, 4:44*pm, Ramy wrote: On Aug 24, 1:11*pm, mattm wrote: Reichmann points out that MC 1 is a better setting if you are in desparation mode, because you give up only a little glide distance but you get to sample more air in a given time. Are you sure about that? MC=0 will give you more time and more air to sample (beeing the best L/D speed) than MC=1. I always use MC=0 when I switch to survival mode unless I am also battling significant head wind. Ramy Yes, it's true. *It's on the last page of this paper:http://www.dragonnorth.com/djpresent...training_for_c... "A lot of pilots flew and fly unnecessarily low average speeds when they get low, because they are anxious and fly with a zero setting. They don’t know that with a setting at 1 knot they have almost the same glide angle and lose much less average speed in case they recover and complete the task." In my plane (ASW-19) MC=0 speed is 53kts, and L/D is 38:1. MC=1 speed is 61kts, and L/D is 35:1. *Granted my sink rate is about 30fpm faster, but I'll have almost 20% greater range to find that thermal I need to get back up again. -- Matt Matt I'm afraid you missunderstood Reichmann comment. He claimed that you will lose less average speed with MC1 which is true. But you will not gain 20% greater range. On the contrary, Your search range will always be less if you fly faster than MC=0 (unless you have significant head wind which requires flying faster than best L/D). Bottom line, as other pointed out, it all depends on your goal. If you are flying contest, in which every second counts, then flying correct MC is important. If you fly for OLC or distance, like I believe the majority of XC flights are, and your main objection is to make it back home at the end of the day (as the subject lline says), than fly *MC 0 when you are in survival mode or starting your final glide. Ramy But, but, but, (and I think I can hear John Cochrane pounding his head on his desk in Chicago...) when about to go on final glide and you are in that last thermal you know what the theoretical final glide Mc should be. And by all means factor in safety margins but if you have a climb significantly over your Mc="0" value then keep climbing and bump the Mc appropriately to match that climb. I mean why not? I know sometimes pilots like to float past the home airport and stretch a few more OLC miles then turn back. Personally the call of that cold beer makes me want to fly that final glide as fast as possible. What is really annoying about arguing with Ramy on this point (which I think I've done before) is no matter what I can argue on paper I have no hope of keeping up with him in practice. Sigh Darryl- Hide quoted text - - Show quoted text - Funny, I guess I can fly better than I can explain myself :-) All I am trying to say about the final glide is that if you are not competing (or competing against the sun as in my case sometimes) the exact speed you fly on your final glide wouldn't matter much. And instead of dialing MC according to your last climb to determine when to leave the thermal and then ignore this MC on your glide if you want to ensure you get back home even with no lift, just degrade your polar instead, climb as high as you feel comfortable, then fly as fast as you can without loosing glide. Simple. Of course while on course and high crank up the MC as high as you dare, just make sure you stay in the desired lift band. But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Ramy Now you are going to start another argument. Oh well, here goes... I degrade my ASH-26E book polar by 5% bugs if the wings are clean, just want to take the edge off and it seems to match pretty close to what I can get. I want the computer to tell me what I can really do and I'll factor safety margins (including using arrival height padding, Mc etc.) depending on how I assess the risk. And that is not just because I flying a motorglider, I'll use similar low bugs when flying the Duo etc. I payed all that money for that 50:1 L/D -- I'm not going to just throw it away :-) (yes for new XC pilots, padding with bugs is entirely different). Darryl |
#43
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required LD versus required MC to make it home
On Aug 24, 10:32*pm, Ramy wrote:
On Aug 24, 5:16*pm, Darryl Ramm wrote: On Aug 24, 5:06*pm, Ramy wrote: On Aug 24, 2:54*pm, mattm wrote: On Aug 24, 4:44*pm, Ramy wrote: On Aug 24, 1:11*pm, mattm wrote: Reichmann points out that MC 1 is a better setting if you are in desparation mode, because you give up only a little glide distance but you get to sample more air in a given time. Are you sure about that? MC=0 will give you more time and more air to sample (beeing the best L/D speed) than MC=1. I always use MC=0 when I switch to survival mode unless I am also battling significant head wind. Ramy Yes, it's true. *It's on the last page of this paper:http://www.dragonnorth.com/djpresent...training_for_c... "A lot of pilots flew and fly unnecessarily low average speeds when they get low, because they are anxious and fly with a zero setting. They don’t know that with a setting at 1 knot they have almost the same glide angle and lose much less average speed in case they recover and complete the task." In my plane (ASW-19) MC=0 speed is 53kts, and L/D is 38:1. MC=1 speed is 61kts, and L/D is 35:1. *Granted my sink rate is about 30fpm faster, but I'll have almost 20% greater range to find that thermal I need to get back up again. -- Matt Matt I'm afraid you missunderstood Reichmann comment. He claimed that you will lose less average speed with MC1 which is true. But you will not gain 20% greater range. On the contrary, Your search range will always be less if you fly faster than MC=0 (unless you have significant head wind which requires flying faster than best L/D). Bottom line, as other pointed out, it all depends on your goal. If you are flying contest, in which every second counts, then flying correct MC is important. If you fly for OLC or distance, like I believe the majority of XC flights are, and your main objection is to make it back home at the end of the day (as the subject lline says), than fly *MC 0 when you are in survival mode or starting your final glide. Ramy But, but, but, (and I think I can hear John Cochrane pounding his head on his desk in Chicago...) when about to go on final glide and you are in that last thermal you know what the theoretical final glide Mc should be. And by all means factor in safety margins but if you have a climb significantly over your Mc="0" value then keep climbing and bump the Mc appropriately to match that climb. I mean why not? I know sometimes pilots like to float past the home airport and stretch a few more OLC miles then turn back. Personally the call of that cold beer makes me want to fly that final glide as fast as possible. What is really annoying about arguing with Ramy on this point (which I think I've done before) is no matter what I can argue on paper I have no hope of keeping up with him in practice. Sigh Darryl- Hide quoted text - - Show quoted text - Funny, I guess I can fly better than I can explain myself :-) All I am trying to say about the final glide is that if you are not competing (or competing against the sun as in my case sometimes) the exact speed you fly on your final glide wouldn't matter much. And instead of dialing MC according to your last climb to determine when to leave the thermal and then ignore this MC on your glide if you want to ensure you get back home even with no lift, just degrade your polar instead, climb as high as you feel comfortable, then fly as fast as you can without loosing glide. Simple. Of course while on course and high crank up the MC as high as you dare, just make sure you stay in the desired lift band. But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Ramy Within safe glide to an airport at any one time? What a concept! |
#44
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required LD versus required MC to make it home
On Aug 24, 9:32*pm, Ramy wrote:
On Aug 24, 5:16*pm, Darryl Ramm wrote: On Aug 24, 5:06*pm, Ramy wrote: On Aug 24, 2:54*pm, mattm wrote: On Aug 24, 4:44*pm, Ramy wrote: On Aug 24, 1:11*pm, mattm wrote: Reichmann points out that MC 1 is a better setting if you are in desparation mode, because you give up only a little glide distance but you get to sample more air in a given time. Are you sure about that? MC=0 will give you more time and more air to sample (beeing the best L/D speed) than MC=1. I always use MC=0 when I switch to survival mode unless I am also battling significant head wind. Ramy Yes, it's true. *It's on the last page of this paper:http://www.dragonnorth.com/djpresent...training_for_c... "A lot of pilots flew and fly unnecessarily low average speeds when they get low, because they are anxious and fly with a zero setting. They don’t know that with a setting at 1 knot they have almost the same glide angle and lose much less average speed in case they recover and complete the task." In my plane (ASW-19) MC=0 speed is 53kts, and L/D is 38:1. MC=1 speed is 61kts, and L/D is 35:1. *Granted my sink rate is about 30fpm faster, but I'll have almost 20% greater range to find that thermal I need to get back up again. -- Matt Matt I'm afraid you missunderstood Reichmann comment. He claimed that you will lose less average speed with MC1 which is true. But you will not gain 20% greater range. On the contrary, Your search range will always be less if you fly faster than MC=0 (unless you have significant head wind which requires flying faster than best L/D). Bottom line, as other pointed out, it all depends on your goal. If you are flying contest, in which every second counts, then flying correct MC is important. If you fly for OLC or distance, like I believe the majority of XC flights are, and your main objection is to make it back home at the end of the day (as the subject lline says), than fly *MC 0 when you are in survival mode or starting your final glide. Ramy But, but, but, (and I think I can hear John Cochrane pounding his head on his desk in Chicago...) when about to go on final glide and you are in that last thermal you know what the theoretical final glide Mc should be. And by all means factor in safety margins but if you have a climb significantly over your Mc="0" value then keep climbing and bump the Mc appropriately to match that climb. I mean why not? I know sometimes pilots like to float past the home airport and stretch a few more OLC miles then turn back. Personally the call of that cold beer makes me want to fly that final glide as fast as possible. What is really annoying about arguing with Ramy on this point (which I think I've done before) is no matter what I can argue on paper I have no hope of keeping up with him in practice. Sigh Darryl- Hide quoted text - - Show quoted text - Funny, I guess I can fly better than I can explain myself :-) All I am trying to say about the final glide is that if you are not competing (or competing against the sun as in my case sometimes) the exact speed you fly on your final glide wouldn't matter much. And instead of dialing MC according to your last climb to determine when to leave the thermal and then ignore this MC on your glide if you want to ensure you get back home even with no lift, just degrade your polar instead, climb as high as you feel comfortable, then fly as fast as you can without loosing glide. Simple. Of course while on course and high crank up the MC as high as you dare, just make sure you stay in the desired lift band. But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Ramy Hi Ramy, I know you are an OLC stud. Nevertheless I will take a crack at spanning the gap between you and Mr. Cochrane - who is a competition strategy stud. There are two potential objectives in calculating how to look for and manage the last climb leading to final glide: 1) maximize the probability of getting home when time is not a factor, and 2) maximizing expected speed (and hence expected contest points) adjusted for probability of landing out. In the first case, if you are low and desperate you pull back to best L/D and fly in the direction of the most likely lift, even if it means backtracking on course. In the second case you are trading off your best estimate of probability of landing out against speed, with the tradeoff in contests dictated by the ratio of speed points to distance points. Reichmann's point here is quite relevant - a 1.0 McCready keeps up progress toward the goal and dilutes your total speed less quickly than Mc = 0, which trades landout probability for speed at a suboptimal rate - that is, you gain expected finish points less quickly than you lose speed points - all probability adjusted. The stronger the lift the more you want to fly a little faster while searching to make sure that you don't give up speed points. As to the final glide itself (and I understand the unique issues associated with returning to an elevated airport like Truckee, where you need to set up the final glide quite far out with little chance to recover if you miss low). The basic issue here is how to balance the glide margin - how much should be based on glide angle margin and how much should be based on finish height margin? There are two potential estimation errors you need to deal with: 1) error associated with mis- estimating the actual glide angle you can achieve at any given glide speed and 2) errors associated with short-term losses in altitude from sink enroute. Ideally you can account for 1) by managing your glide speed to make sure your achieved glide angle is shallower than needed. You can do this in one of two ways. First you can artificially steepen up the glide angle at any given speed through manipulating the polar, or you can set the Mc for higher than the speed you actually fly (or some combination of the two). The basic objective under both approaches is to ensure you gain a bit on the glide rather than losing a bit. The problem with using bugs and flying with a zero Mc is that you fly too slow to optimize speed and you tend to leave strong final thermals too soon. As to issue 2), the issue to keep in mind is the risk of hitting a line of sink and losing your glide. As John points out, this risk goes up as you get closer to home because you get progressively lower and have a declining chance of being able to find a saving climb after a sink street. This is why the better strategy when there is a lot of uncertainty about lift/sink on the way home is to add finish altitude rather than steepen the glide - steepening the glide give you a margin that decrements to zero feet as you approach the finish whereas altitude margin doesn't. This says that you are better off adding finish height than steepening the glide angle as a glide angle margin goes away as you get closer to home. It also argues for leaving the final thermal at with a Mc setting that is a bit higher than you actual climb rate, then setting speed-to-fly a bit slower so yo gain on the glide going home. I will observe that in my experience the first glider to leave the thermal gets home first. I have left thermals before getting to the the height indicated by the Mc setting and won by a couple of minutes and have stuck with 10-knot thermals only to be unable to catch gliders leaving before me. It has never worked any other way. This must mean that either pilots are able to "bump up' the final glide on the way home, or that final thermal isn't as strong as I think. In either case it means I generally stay with my final climb too long. 9B Hope that helps, 9B |
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required LD versus required MC to make it home
On Aug 24, 9:32*pm, Ramy wrote:
On Aug 24, 5:16*pm, Darryl Ramm wrote: On Aug 24, 5:06*pm, Ramy wrote: On Aug 24, 2:54*pm, mattm wrote: On Aug 24, 4:44*pm, Ramy wrote: On Aug 24, 1:11*pm, mattm wrote: Reichmann points out that MC 1 is a better setting if you are in desparation mode, because you give up only a little glide distance but you get to sample more air in a given time. Are you sure about that? MC=0 will give you more time and more air to sample (beeing the best L/D speed) than MC=1. I always use MC=0 when I switch to survival mode unless I am also battling significant head wind. Ramy Yes, it's true. *It's on the last page of this paper:http://www.dragonnorth.com/djpresent...training_for_c... "A lot of pilots flew and fly unnecessarily low average speeds when they get low, because they are anxious and fly with a zero setting. They don’t know that with a setting at 1 knot they have almost the same glide angle and lose much less average speed in case they recover and complete the task." In my plane (ASW-19) MC=0 speed is 53kts, and L/D is 38:1. MC=1 speed is 61kts, and L/D is 35:1. *Granted my sink rate is about 30fpm faster, but I'll have almost 20% greater range to find that thermal I need to get back up again. -- Matt Matt I'm afraid you missunderstood Reichmann comment. He claimed that you will lose less average speed with MC1 which is true. But you will not gain 20% greater range. On the contrary, Your search range will always be less if you fly faster than MC=0 (unless you have significant head wind which requires flying faster than best L/D). Bottom line, as other pointed out, it all depends on your goal. If you are flying contest, in which every second counts, then flying correct MC is important. If you fly for OLC or distance, like I believe the majority of XC flights are, and your main objection is to make it back home at the end of the day (as the subject lline says), than fly *MC 0 when you are in survival mode or starting your final glide. Ramy But, but, but, (and I think I can hear John Cochrane pounding his head on his desk in Chicago...) when about to go on final glide and you are in that last thermal you know what the theoretical final glide Mc should be. And by all means factor in safety margins but if you have a climb significantly over your Mc="0" value then keep climbing and bump the Mc appropriately to match that climb. I mean why not? I know sometimes pilots like to float past the home airport and stretch a few more OLC miles then turn back. Personally the call of that cold beer makes me want to fly that final glide as fast as possible. What is really annoying about arguing with Ramy on this point (which I think I've done before) is no matter what I can argue on paper I have no hope of keeping up with him in practice. Sigh Darryl- Hide quoted text - - Show quoted text - Funny, I guess I can fly better than I can explain myself :-) All I am trying to say about the final glide is that if you are not competing (or competing against the sun as in my case sometimes) the exact speed you fly on your final glide wouldn't matter much. And instead of dialing MC according to your last climb to determine when to leave the thermal and then ignore this MC on your glide if you want to ensure you get back home even with no lift, just degrade your polar instead, climb as high as you feel comfortable, then fly as fast as you can without loosing glide. Simple. Of course while on course and high crank up the MC as high as you dare, just make sure you stay in the desired lift band. But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Ramy Ramy et al, Part of the different views in this discussion is the different kinds of final glides people are talking about. For example, in Ramy's case (and mine as well), a typical "final glide" means: it is is around 6:30 pm or even later, lift is dying, you are 40 to 50 nautical miles away from home, you are in the last obvious lift which could be very well be a 5 knot thermal, but still the last one. A westerly wind is pushing everything east, the nature of the airmass ahead is unknown with a potential strong headwind component (funny how winds play havoc on the PDA's estimate of your situation when you are 40~50 miles from home). And to make things even more interesting, "home" means you also need to cross Lake Tahoe to get there. Under this situation it is not unusual to climb to the top of the thermal or even bump up against class A airspace, and you barely have it at MC 0. The bug factor Ramy talks about is to account for the significant uncertainty in the airmass/wind on the 40 nm leg (which can easily span a couple of airmasses). Waiting for an MC 5 altitude under those conditions, not going to happen. David |
#46
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Getting rid of the bugs and gotchas!
On 8/24/2010 7:53 PM, akiley wrote:
On Aug 24, 12:08 am, Eric wrote: I've used SeeYou Mobile for 1000+ hours all over the USA, and I'm not aware of any bugs or gotchas. I would never go back to paper charts, whiz wheels, or just looking out the window. For example, most of my final glides begin 30 to 50 miles from the airport, where I can't even see it, yet they work out well most of the time. Eric, What happens if your electronics fry? Hope you have a backup something. I've used 4 PDAs over 10 years, 2000 hours total, with no failures, so I haven't had to pull out the charts and ruler I always carry with me (mostly out of habit). But, a PDA going bad isn't a SeeYou Mobile problem. There are plenty of gochas I can think of is SeeYouM. All you have to do is not double check what your goto waypoint is, forget to add winds, polar, safety altitude. Maybe they aren't gochas, but they sort of are for new users. These aren't SeeYou Mobile gotchas either, they are part of using a "soaring computer", whether it's a map with circles, paper sheets with tables of glide distances, or an electronic computer. The polar and safety altitude (I assume you mean the "arrival altitude", are settings you should do at home; i.e. "set and forget". I'm not sure what you mean by "add winds", as SYM automatically uses the winds in it's computations. Perhaps you mean "adjusting the winds"? Sometimes you have to do that when you realize the winds ahead of you are different from the winds SYM has calculated. It takes a lot of thinking to make sure you know what you are doing. Yep, the cockpit is a busy place in a glider if you are going cross-country, and it takes a while to get accustomed to a flight computer. I had the advantage of 20 years of soaring before using PDA flight computers, so the transition was much easier for me. I have the latest version of SeeYouM that I bought last fall. One known bug is that the wing loading changes when you leave the polar screen then come back. Try it. It doesn't change on my setup (Ipaq 3835 with ver 3.11). Maybe it's a 3.12 issue. I think they fixed the one with Oudie that didn't allow the user to set NM in units. You would have to reset it every time you loaded SeeYouM. I haven't gotten an answer on my Magnetic Track NavBox yet. It's off by 12 degrees. I have to admit I've never used any kind of track bearing. I just put the two different track bearing boxes on my PDA (simulator mode), and they both read correctly (Washington state area); however, I get the same error you do when I try to "fly" in Michigan. Maybe it's party to do with old PDA hardware but I've had a lot of problems with logging not starting, and NavBoxes showing no data, and lockups. Other have had these problem too. Some days my statistic page that is supposed to show thermal graphs doesn't. There is a quirk in the older Ipaqs that can cause symptoms like this. The fix is to disable the IR port, which is sensitive to sunlight, and slows down the system. Make sure the beam is off on your Ipaq. Do something like this: Start, Settings, Connections, Beam, uncheck box. It also might be your hardware, as I've had none of those problems on my fairly old 3835. What PDA are you using? Do you have GPS problems (you might be able to determine that by looking at the flight trace in SeeYou)? What GPS do you use? I'm slowly replacing components of my iPaq to see if that's the problem. I just replaced the CF card adapter back, I've tried a different CF card. We'll see. I'm definitely a navigator user. I have a Garmin 395, I've put quite a lot of hours on Garmin G1000's in IFR flight. My point is one has to be careful throwing full trust into these things. Agreed. Start out conservatively, get comfortable with it, and then you can reduce the margins bit by bit to make cross-country flying easier and more enjoyable. -- Eric Greenwell - Washington State, USA (netto to net to email me) |
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required LD versus required MC to make it home
On 8/24/2010 9:32 PM, Ramy wrote:
On Aug 24, 5:16 pm, Darryl R But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Point #1: I think what you are doing is essentially the same as keeping the bugs at "no bugs", but using a high MC setting to figure the "safety glide". A high MC means a steep glide angle compared to 0 MC - there's the "degradation" in the polar you are wondering about. I normally use a 4 MC for my "safety glide" computation, which gives an L/D of 70% of my max L/D. Point #2: In addition to the 4 MC setting, I usually carry excess altitude above the 4 MC glide slope to absorb strong sink and unexpectedly strong headwinds. Over friendly ground in moderate conditions, 500' excess has proven adequate; in strong conditions over unfriendly ground, it might be as much as 2000' excess. These numbers are trimmed as the distance to the airport decreases, starting about 10-20 miles out, because my 1000' AGL arrival height begins to provide the "sink absorption" buffer. Of course, I don't use the 4 MC setting as my speed to fly if I have to head towards my safety airport; instead, I use a 1 MC setting (or zero MC if I'm truly desperate). My MC setting for the "safety glide" is separate from my "speed to fly" setting on my Cambridge 302, which is usually set at 1 (moderate conditions) or 2 (strong conditions). The above MC and excess altitude settings have proved satisfactory for all my gliders, from a Ka-6e to an ASH 26 E. Of course, the speeds flown were quite different for each glider. -- Eric Greenwell - Washington State, USA (netto to net to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz |
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required LD versus required MC to make it home
On Aug 25, 2:41*pm, Eric Greenwell wrote:
On 8/24/2010 9:32 PM, Ramy wrote: On Aug 24, 5:16 pm, Darryl R But honestly, I don't understand how many of you fly XC safely if you don't degrade your polar. How do you determine you are within safe glide from airports at any point in time? using your published polar and a safety altitude margin? Good luck if you hit any sink or head wind on the way unless you use a big altitude margin which will significantly hurt your decision down lower. The suggestion to use bug factor to degrade your polar is basically an implementation of the common rule of thumb to use 50%-75% of your published polar to determine arrival altitude. Point #1: I think what you are doing is essentially the same as keeping the bugs at "no bugs", but using a high MC setting to figure the "safety glide". A high MC means a steep glide angle compared to 0 MC - there's the "degradation" in the polar you are wondering about. I normally use a 4 MC for my "safety glide" computation, which gives an L/D of 70% of my max L/D. Point #2: In addition to the 4 MC setting, I usually carry excess altitude above the 4 MC glide slope to absorb strong sink and unexpectedly strong headwinds. Over friendly ground in moderate conditions, 500' excess has proven adequate; in strong conditions over unfriendly ground, it might be as much as 2000' excess. These numbers are trimmed as the distance to the airport decreases, starting about 10-20 miles out, because my 1000' AGL arrival height begins to provide the "sink absorption" buffer. Of course, I don't use the 4 MC setting as my speed to fly if I have to head towards my safety airport; instead, I use a 1 MC setting (or zero MC if I'm truly desperate). My MC setting for the "safety glide" is separate from my "speed to fly" setting on my Cambridge 302, which is usually set at 1 (moderate conditions) or 2 (strong conditions). The above MC and excess altitude settings have proved satisfactory for all my gliders, from a Ka-6e to an ASH 26 E. Of course, the speeds flown were quite different for each glider. -- Eric Greenwell - Washington State, USA (netto to net to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz I generally do something similar to what Eric describes. In my computer setup it's a lot easier to fiddle with the Mc setting than adjust the bugs setting. The basic idea is to have a steeper glide dialed and fly slightly slower until you establish that you are on glidepath or better, but also to keep a constant arrival altitude margin to account for the "2 miles of 10 kts down" scenario - for that you need an arrival altitude buffer, not a glide angle buffer. If you are way out on final glide you might start with a negative arrival margin in an attempt to bump it up over time, but you need to get up to glidepath by the time you are about 20 mile out or you will be out of search range to find some lift to get up to glidepath. 9B |
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Getting rid of the bugs and gotchas!
On Aug 25, 2:35*pm, Eric Greenwell wrote:
On 8/24/2010 7:53 PM, akiley wrote: On Aug 24, 12:08 am, Eric *wrote: I've used SeeYou Mobile for 1000+ hours all over the USA, and I'm not aware of any bugs or gotchas. I would never go back to paper charts, whiz wheels, or just looking out the window. For example, most of my final glides begin 30 to 50 miles from the airport, where I can't even see it, yet they work out well most of the time. Eric, What happens if your electronics fry? *Hope you have a backup something. I've used 4 PDAs over 10 years, 2000 hours total, with no failures, so I haven't had to pull out the charts and ruler I always carry with me (mostly out of habit). But, a PDA going bad isn't a SeeYou Mobile problem.. There are plenty of gochas I can think of is SeeYouM. *All you have to do is not double check what your goto waypoint is, forget to add winds, polar, safety altitude. Maybe they aren't gochas, but they sort of are for new users. These aren't SeeYou Mobile gotchas either, they are part of using a "soaring computer", whether it's a map with circles, paper sheets with tables of glide distances, or an electronic computer. The polar and safety altitude (I assume you mean the "arrival altitude", are settings you should do at home; i.e. "set and forget". I'm not sure what you mean by "add winds", as SYM automatically uses the winds in it's computations. Perhaps you mean "adjusting the winds"? Sometimes you have to do that when you realize the winds ahead of you are different from the winds SYM has calculated. * *It takes a lot of thinking to make sure you know what you are doing. I mean clear the winds totally in SeeYou then enter the official winds aloft forecast. Maybe SeeYou does a better job, I haven't really tested this. I just look at my IGC file from this Wednesday and the winds were supposed to be 320 at 12kts in the 3000 to 6000 range. At a few points spanning several minutes, SeeYou came back with winds from 160 at 2 kts. But maybe this happens and is to be believed. Or I'm really bad a drawing circles with a glider. Probably the later. Yep, the cockpit is a busy place in a glider if you are going cross-country, and it takes a while to get accustomed to a flight computer. I had the advantage of 20 years of soaring before using PDA flight computers, so the transition was much easier for me. I have the latest version of SeeYouM that I bought last fall. *One known bug is that the wing loading changes when you leave the polar screen then come back. *Try it. It doesn't change on my setup (Ipaq 3835 with ver 3.11). Maybe it's a 3.12 issue. * *I think they fixed the one with Oudie that didn't allow the user to set NM in units. *You would have to reset it every time you loaded SeeYouM. *I haven't gotten an answer on my Magnetic Track NavBox yet. *It's off by 12 degrees. I bought this used iPaq which was listed as a 3700 on the reciept from Wings and Wheels. Just out of warrantee. The label is worn and unreadable on the back. Don't know of a software way to positively ID the unit. It uses the CF cards and an add-on sleeve adapter to hold the CF card. I have the slightly newer SeeYou Mobil ver 3.12. I have had lots of IGC files with broken track or perfectly straight lines or both. Also, I have to reboot my iPaq on a daily basis. Not sure if I replace the iPaq next or the GPS. I did get an uninterrupted file this wednesday on a 2.5 hr flight in the Cirrus. I have to admit I've never used any kind of track bearing. I just put the two different track bearing boxes on my PDA (simulator mode), and they both read correctly (Washington state area); however, I get the same error you do when I try to "fly" in Michigan. * *Maybe it's party to do with old PDA hardware but I've had a lot of problems with logging not starting, and NavBoxes showing no data, and lockups. Other have had these problem too. *Some days my statistic page that is supposed to show thermal graphs doesn't. I just have the navBox called "Magnetic track over ground" at the top center used as a heading indicator, even though it really is'nt. There is a quirk in the older Ipaqs that can cause symptoms like this. The fix is to disable the IR port, which is sensitive to sunlight, and slows down the system. Make sure the beam is off on your Ipaq. Do something like this: Start, Settings, Connections, Beam, uncheck box. I just checked, this box is unchecked. But thanks for the heads up. It also might be your hardware, as I've had none of those problems on my fairly old 3835. What PDA are you using? Do you have GPS problems (you might be able to determine that by looking at the flight trace in SeeYou)? What GPS do you use? I'm slowly replacing components of my iPaq to see if that's the problem. *I just replaced the CF card adapter back, I've tried a different CF card. *We'll see. I had the guys on the Navitar forum looking at these IGC files and trying to help me with all my issues. They never came to any conclusion on the broken flight tracks. .... akiley I'm definitely a navigator user. *I have a Garmin 395, I've put quite a lot of hours on Garmin G1000's in IFR flight. *My point is one has to be careful throwing full trust into these things. Agreed. Start out conservatively, get comfortable with it, and then you can reduce the margins bit by bit to make cross-country flying easier and more enjoyable. -- Eric Greenwell - Washington State, USA (netto to net to email me) |
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Getting rid of the bugs and gotchas!
On 8/26/2010 7:16 PM, akiley wrote:
I mean clear the winds totally in SeeYou then enter the official winds aloft forecast. Maybe SeeYou does a better job, I haven't really tested this. I just look at my IGC file from this Wednesday and the winds were supposed to be 320 at 12kts in the 3000 to 6000 range. At a few points spanning several minutes, SeeYou came back with winds from 160 at 2 kts. But maybe this happens and is to be believed. Or I'm really bad a drawing circles with a glider. Probably the later. I always let Mobile fill in the blanks. It does a good job of measuring the wind while circling, so I think it's better to use the actual wind instead of a forecast wind; less trouble, too. I will sometimes change the wind settings when I know I am flying into an area where the wind is different from what Mobile has measured. This is usually the final glide to the home airport, and since I haven't flown near home for the last few hours, the wind it measured after the takeoff and the first couple of thermals as I headed out on course may no longer be correct. I bought this used iPaq which was listed as a 3700 on the reciept from Wings and Wheels. Just out of warrantee. The label is worn and unreadable on the back. Don't know of a software way to positively ID the unit. It uses the CF cards and an add-on sleeve adapter to hold the CF card. I have the slightly newer SeeYou Mobil ver 3.12. I have had lots of IGC files with broken track or perfectly straight lines or both. Also, I have to reboot my iPaq on a daily basis. Not sure if I replace the iPaq next or the GPS. I did get an uninterrupted file this wednesday on a 2.5 hr flight in the Cirrus. Mobile for PDAs is a mature, stable program. These problems are almost certainly hardware related. Can you borrow another Ipaq for a flight or two? I just have the navBox called "Magnetic track over ground" at the top center used as a heading indicator, even though it really is'nt. Unless you are really in love with magnetic bearings, I suggest you switch to "track over ground" to use True bearings instead. -- Eric Greenwell - Washington State, USA (netto to net to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz |
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