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  #51  
Old September 9th 18, 04:26 PM posted to rec.aviation.soaring
Dave Walsh
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Pretty sure all recent DGs come with stall warning built in.
DG's web site explains the background to their thinking.
The system in the DG808C I used to own was pretty good; you
got a verbal warning, hard to misinterpret "Stall, stall".
Dave Walsh

  #52  
Old September 10th 18, 12:17 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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On Saturday, September 8, 2018 at 9:19:29 PM UTC-4, Tom BravoMike wrote:
On Saturday, September 8, 2018 at 7:14:46 PM UTC-5, SoaringXCellence wrote:
AOA devices are becoming very common in the experimental/homebuilt airplane world. A recent publication from the FAA (!) recommended that pilots consider getting a AOA sensor installed in their airplane. The newer completed aircraft in the famous Vans Aircraft RV series are almost all equipped with a AOA device.

I have been investigating a AOA system to install in gliders for several years but keep running into challenges due to flaps and spoilers and their effect on the system. The whole device is very easy if the airflow and overall AOA doesn't change much with configuration changes.

One fix is to set the system primarily for landing and disable it for other flight regimes. Unfortunately that means you can't use the best L/D AOA, or other selected angles to correct for weight changes.

I also have a Raspberry Pi and considered just starting to log the data for my glider. This winter I'm doing a refinish; maybe that a good time to install the pressure sensors and start logging.

Mike


In the SZD55-1 Flight manual,

http://org.ntnu.no/nthf/dokument/fli...als/LN-GAZ.pdf

p. 12a, it says that "For airworthiness the JAR-22 require the sailplane to be equipped at least with: airspeed indicator, altimeter and STALL WARNING DEVICE." I can remember there was some kind of a buzzer on the SZD-55 I used to own for a short time, but I never heard it sound nor don't know how it was supposed to work.


Any other SZD-55 owners/pilots here?


http://www.olk.com.pl/indexen.php?bo...roducts&lpx=26 is the SZD-55 system. Works well but is a bit startling in the flare the first couple of flights.
  #53  
Old September 10th 18, 10:30 PM posted to rec.aviation.soaring
[email protected]
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Hi all,

I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

More info at my homepage: http://niklaslofgren.net/gliding/var...ariometer.html

/Niklas
  #54  
Old September 11th 18, 12:39 AM posted to rec.aviation.soaring
Jonathan St. Cloud
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On Monday, September 10, 2018 at 2:30:43 PM UTC-7, wrote:
Hi all,

I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

More info at my homepage: http://niklaslofgren.net/gliding/var...ariometer.html

/Niklas


Your YouTube links did not have videos.
  #55  
Old September 12th 18, 02:13 PM posted to rec.aviation.soaring
[email protected]
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Oh, sorry, here are the correct links.
Respons test: https://youtu.be/UfeGWYwVdas
vw1020 respons test: https://youtu.be/Irun92_0JWQ?t=11m16s
  #56  
Old September 13th 18, 04:47 AM posted to rec.aviation.soaring
Mike Borgelt[_2_]
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On Tuesday, 11 September 2018 07:30:43 UTC+10, wrote:
Hi all,

I've been looking for a good electrical vario for many years. Having good knowledge in both digital signal processing and gliding I know what to look for. First, a lot of pilots can't even recognise if the vario is compensated or not, let alone if it's fast/slow or even accurate. I've conducted test like these to get the real respons from varios: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

I've owned the airglide and used it for about 200h. Airglide is not a good variometer, very unstable, the filtering is not done correctly. The LXnav /LXnavigation stuff I've flown with have also been quite bad. Old Zander ZS1/940 has a much better variometer. The modern stuff just haven't got the filtering or sensor precision correct. The only modern vario i've tested that was good is the westerboer vw1020: https://www.youtube.com/edit?o=U&video_id=UfeGWYwVdas

More info at my homepage: http://niklaslofgren.net/gliding/var...ariometer.html

/Niklas


Yup, I had a club who got a new DG505. Complained the B500 and B400 varios worked OK when settled in thermal but not otherwise especially in cruise. After about 9 months they got around to doing a leak check and the TE system would not hold pressure. They did not know they had a triple probe fitting in the fin and only a TE probe plugged in. The other two lines we open in the cockpit, hence no TE. Nobody managed to figure out this was the problem. This was the same outfit that years before had a problem in their Twin Astir with a B50 installation. A voltage check at the instrument revealed 8 volts or so which wasn't enough. They rewired the glider and 3 weeks later called to say all was OK and even the radio now worked properly which it hadn't for about 18 months since the electrical fire in the back of the glider! No names to protect the guilty.

I looked at your videos. A better test of the vario response is the time taken to return to 63% of the zero from the peak. This is the time constant. When connected as a TE vario this will optimally be around 2 to 3 seconds. Any faster the vario will move around a lot and you will spend time averaging by eye or ear which is workload intensive and effectively slower. Alternatively the 10% to 90% response time is another better measure.
Other comments:
1. The advantage of electronic varios isn't just the various kinds of averagers (running, total) but audio and all the other (netto, relative,speed command) signal processing.
2. I disagree about electrical pitot static compensation. The low drag argument goes away if you have a TE probe anyway for the mechanical or other TE probe compensated vario. The effect of sideslip on a static port on the nose of a glider is usually greater than on a good design TE probe. Then we have the problem of getting two large signals to arrive at the vario at the same time. We subtract these from each other to get the TE vario and any phase errors can cause large spurious transient response on that. Been there, done that, don't need the support calls. Then there is the problem when the static ports do not have constant percentage errors over the speed range.. If you use the Prandtl pitot static on the fin you may as well use the TE probe there. There are errors due to changing G loads and rotation of the glider
3. Time constants in the plumbing. I measured these. Without any vario capacities but including the probe, its holes and the mount in the fin the TE line has a time constant of around 90 to 100 milliseconds. I put an inflated balloon around the probe, hooked the pressure transducer connected in the cockpit to a DSO and popped the balloon. If a typical mechanical vario 450 ml flask is in the cockpit but no vario it went to about 270 to 300 milliseconds.
The time constant of the glider at thermal speeds is about 0.5 seconds on entering lift, as mentioned in an earlier post. If you have a vario connected to static that further slows the vario. If connected to TE that time constant disappears. George Moffat mentioned that a vario is "livelier" when connected to TE in the early 1970s but not the reason why.
Just yesterday Carol and I flew in to South East Queensland gliding club in our BD-4 and ran into a guy from Czech Republic. When he found out who we were, we had a nice discussion on variometers. I was pleased that he had flown extensively with Borgelt varios and he found that they confirmed what his other senses were telling him which he said was unlike most of the others, which confirms your observations about some modern varios.
I've also heard from a German customer that his club bought one of the LCD display devices and he considered it more of a "glider entertainment system" than a vario.

Mike





  #57  
Old September 13th 18, 08:57 AM posted to rec.aviation.soaring
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On Friday, September 7, 2018 at 9:08:28 AM UTC-4, Nick Kennedy wrote:
This has turned into a very interesting thread. It looks like we may be using some newer much better varios in the near future.
Another interesting aspect is Mike Borgelt describing the AOA change and the possible cause of low level, low speed [ in the pattern] accidents.
When were up high cruising at 80-100 knots we fly into 10 knots up all the time and pull hard to slow down and get ready to circle. Up high at speed this is no problem. Down low and slow at say 60 knots that 10 knot thermal you just hit may cause a major problem. I think we may be flying way to slow in the pattern. Looking at the stall/spin rates, in all parts of the arrival pattern, I might be right.
I like using the Knauff idea of having a longer higher final leg, and as my max flap extension speed in my LS3a is 86 knots, I try to keep it over 70 knots the whole way to the deck, works for me. This may sound fast and it is. I don't want to stall close to the ground by some rouge air or a booming thermal.
This fast in the pattern stuff was taught to me by Bob Faris CFIG
So far so good!


Regarding air speeds in the pattern, in a prior sequence the subject came up about the correct speed to fly 2-32s in the pattern. Some of the folks responded that 70 knots was way too fast. Yet this was the airspeed most of us using them in our commercial operations flew them at in New England starting in the late 60s. Despite the fact that the 2-32 had a reputation for spinning in, I don't remember any base to final turn spin ins in New England which suggests that the FBOs who came before me like Jim Doyle and John MaCone were doing something right.

What I do remember was a triple fatality involving a 2-32 in which the glider pilot did not properly lock the canopy prior to take off and stopped flying the glider instead of pulling the release on the ground roll the moment the canopy started flopping. He continued to attempt to close the canopy until the glider reached 100 feet at which point the tow pilot was forced to release the glider. A similar accident also occurred in New England in an ASK-21 that killed the passenger sitting in the front seat along with another 2-32 accident in which the glider pilot had a canopy locking failure on take off on Oahu that killed the pilot only. I suspect there were others I never heard about, after we switched hobby businesses. However we were not immune to a 2-32 spin, that can occur in many different situations. We had a low altitude 2-32 spin in at Plymouth MA, when a tow pilot who obviously was not awake early in the day attempted to tow a 2-32 at its stall speed of 50 mph after landing with the flaps down and neglecting to raise them for the next tow. The 2-32 pilot, unable to keep up with the tow plane, decided to do a 180 return instead of landing straight ahead causing the 2-32 to enter a spin low and hit a cross taxiway right wing down which collapsed and absorbed most of the impact energy injuring the ankles of the passenger only who was sitting in the front seat. The spin in discussions possibly caused by sharp edged vertical gusts are corroborate in YOs discussion in Soaring of the 1986 Regional at Sugarbush in which five gliders were damaged, one fatal, two of which occurred when folks attempted high speed finishes flying too slowly pulled up to go around and instead of gaining altitude spun in. The probable cause was a rotor that frequently forms right over the airport and which on a good wave day when John MaCone operated Sugarbush, broke most of his tow ropes forcing John to go out and purchase a spool of 1/4 inch Nylon rope.

While these comments are not 100% on topic, they highlight what I consider to be a significant problem in our society: disseminating safety information in a manner that does not draw attention to critical safety problems that frequently repeat. In addition, when you can go on the web and watch a video that shows a 1-34 pilot demonstrating precisely what not to do when a canopy flies open on the ground roll or just after lifting off, in which he demonstrates how to fly the glider using one hand to hold the canopy while the other flies the glider, we have a big time problem. Not only are we not reiterating safety issues that were discovered years ago along with their solutions (Schweitzer in response showed that all of their gliders could fly with the canopy flopping), but we are not making a fuss when someone comes along and demonstrates precisely what not to do! As YO also points out, in other countries, folks don't learn to do high speed passes on their own, which is what he claims was the cause of the two rotor induced spin ins at the Bush that did surprisingly did not injure either pilot.
  #58  
Old September 13th 18, 04:50 PM posted to rec.aviation.soaring
Jonathan St. Cloud
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On Thursday, September 13, 2018 at 12:57:15 AM UTC-7, wrote:
On Friday, September 7, 2018 at 9:08:28 AM UTC-4, Nick Kennedy wrote:
This has turned into a very interesting thread. It looks like we may be using some newer much better varios in the near future.
Another interesting aspect is Mike Borgelt describing the AOA change and the possible cause of low level, low speed [ in the pattern] accidents.
When were up high cruising at 80-100 knots we fly into 10 knots up all the time and pull hard to slow down and get ready to circle. Up high at speed this is no problem. Down low and slow at say 60 knots that 10 knot thermal you just hit may cause a major problem. I think we may be flying way to slow in the pattern. Looking at the stall/spin rates, in all parts of the arrival pattern, I might be right.
I like using the Knauff idea of having a longer higher final leg, and as my max flap extension speed in my LS3a is 86 knots, I try to keep it over 70 knots the whole way to the deck, works for me. This may sound fast and it is. I don't want to stall close to the ground by some rouge air or a booming thermal.
This fast in the pattern stuff was taught to me by Bob Faris CFIG
So far so good!


Regarding air speeds in the pattern, in a prior sequence the subject came up about the correct speed to fly 2-32s in the pattern. Some of the folks responded that 70 knots was way too fast. Yet this was the airspeed most of us using them in our commercial operations flew them at in New England starting in the late 60s. Despite the fact that the 2-32 had a reputation for spinning in, I don't remember any base to final turn spin ins in New England which suggests that the FBOs who came before me like Jim Doyle and John MaCone were doing something right.

What I do remember was a triple fatality involving a 2-32 in which the glider pilot did not properly lock the canopy prior to take off and stopped flying the glider instead of pulling the release on the ground roll the moment the canopy started flopping. He continued to attempt to close the canopy until the glider reached 100 feet at which point the tow pilot was forced to release the glider. A similar accident also occurred in New England in an ASK-21 that killed the passenger sitting in the front seat along with another 2-32 accident in which the glider pilot had a canopy locking failure on take off on Oahu that killed the pilot only. I suspect there were others I never heard about, after we switched hobby businesses. However we were not immune to a 2-32 spin, that can occur in many different situations. We had a low altitude 2-32 spin in at Plymouth MA, when a tow pilot who obviously was not awake early in the day attempted to tow a 2-32 at its stall speed of 50 mph after landing with the flaps down and neglecting to raise them for the next tow. The 2-32 pilot, unable to keep up with the tow plane, decided to do a 180 return instead of landing straight ahead causing the 2-32 to enter a spin low and hit a cross taxiway right wing down which collapsed and absorbed most of the impact energy injuring the ankles of the passenger only who was sitting in the front seat. The spin in discussions possibly caused by sharp edged vertical gusts are corroborate in YOs discussion in Soaring of the 1986 Regional at Sugarbush in which five gliders were damaged, one fatal, two of which occurred when folks attempted high speed finishes flying too slowly pulled up to go around and instead of gaining altitude spun in. The probable cause was a rotor that frequently forms right over the airport and which on a good wave day when John MaCone operated Sugarbush, broke most of his tow ropes forcing John to go out and purchase a spool of 1/4 inch Nylon rope.

While these comments are not 100% on topic, they highlight what I consider to be a significant problem in our society: disseminating safety information in a manner that does not draw attention to critical safety problems that frequently repeat. In addition, when you can go on the web and watch a video that shows a 1-34 pilot demonstrating precisely what not to do when a canopy flies open on the ground roll or just after lifting off, in which he demonstrates how to fly the glider using one hand to hold the canopy while the other flies the glider, we have a big time problem. Not only are we not reiterating safety issues that were discovered years ago along with their solutions (Schweitzer in response showed that all of their gliders could fly with the canopy flopping), but we are not making a fuss when someone comes along and demonstrates precisely what not to do! As YO also points out, in other countries, folks don't learn to do high speed passes on their own, which is what he claims was the cause of the two rotor induced spin ins at the Bush that did surprisingly did not injure either pilot.


Years ago before I had a commercial ticket, my local FBO operated their 2-32's such that 70 MPH was the speed in the pattern. I was out of soaring for decade and half, when I returned to soaring, the SOP for the 2-32 had risen to 80 MPH in the pattern and you fly it onto the runway landing on main only. In the last year I have gotten about 100 hours in a 2-32 flying rides, flies like a dream. But I fly it as the owners want 80 MPH in the pattern and fly it on to a main wheel landing. Got good at kissing the main fairly slow. One of the things I love about a 2-32 is that they are an honest spinner, like a T-6, ham fist it and over you go, hope you know what you are doing.
  #59  
Old September 13th 18, 07:44 PM posted to rec.aviation.soaring
kirk.stant
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On Thursday, September 13, 2018 at 10:50:35 AM UTC-5, Jonathan St. Cloud wrote:

One of the things I love about a 2-32 is that they are an honest spinner, like a T-6, ham fist it and over you go, hope you know what you are doing.

Totally agree - flown properly the 2-32 is a sweet glider, same as the T-6. And I found the stall/spin characteristics of both to be entertaining reminders of how planes used to fly - and a strong incentive to respect them! The "balancing on a needle" feeling of a T-6 just before the stall break is priceless!

Been awhile since I spun (intentionally) a 2-32, but still remember the serious push force needed to get that stabilizer forward to break the stall. None of this "let go of the stick and scream like a girl" spin recovery in that beast!

Yeah, I know, not PC, deal with it ;^)

Cheers,

66
  #60  
Old September 14th 18, 10:17 PM posted to rec.aviation.soaring
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On Tuesday, 28 August 2018 05:28:01 UTC-4, Mike Borgelt wrote:


All pressure based instruments will suffer from much the same problems. It does not matter whether the TE compensation is by TE probe or derived from the pitot - static. TE probes are easier as pitot - static compensation introduces potential mismatches between the time the pressure signals arrive at the sensors and as you are subtracting two large signals to look at a small one it is easy to get large transient indications.




Forgive me Mr. Borgelt if I ask a stupid question. I am no expert, but doesn't my ASI subtract these two large signals (Pitot - static)? I do not observe 'large transient indications', ever, expect maybe when I inadvertently stumble in a wave rotor. What am I missing in understanding?
 




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