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#21
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ASG-29/ASW-27 wing refinish
The page he is refering to can be found he
http://www.dg-flugzeugbau.de/sicherheitscockpit-e.html Hope this helps, Markus Eric Greenwell wrote: Gary Evans wrote: While other manufactures have been content with building what looks strong enough DG has actually participated in crash testing. This is not correct. Gerhard Waibel won an OSTIV prize for his work in cockpit safety about 20 years ago. Gerhard's ideas, and the ASW 24 cockpit (the first of the really crashworthy cockpits) was based on extensive testing by a group at MIT, and others. In the years since then, Schleicher continues to monitor the performance of their designs by examining their gliders that are involved in crashes, either when they are brought to their shop for repair, or using pictures sent to them by the mechanics repairing the glider elsewhere. An advantage of this approach is it shows what happens in an actual crash. As a result of this testing they offer the consummate safety cockpit as an option on the 800 series and as standard on the 1000. I have been impressed with DG's improvements in safety over the years, but their single seaters cockpits still do not match what Schleicher has done. This page on the DG website shows that this view is shared by others (go to the "Safety Cockpit" row): http://www.dgflugzeugbau.de/ash-dg-ventus-e.html These differences are not surprising. The low sides and open nose of the DG single seater cockpit pose a difficult engineering problem for the designer, compared to the greater enclosure of the Schleicher cockpits. I'm not suggesting that the DG cockpit is unsafe or inadequate, but only that it does not match what Schleicher has done. A prospective owner should consider the value of that protection along with the other features of the gliders he is considering; for example, the lower sides of the DG cockpit (particularly if the NOAH option is selected) should make baling out easier than from a Schleicher cockpit. If you counting on higher frame rails for protection you may also want to read this. http://www.dg-flugzeugbau.de/index-e.html I was unable to find this reference, but I would like to read it. -- Eric Greenwell - Washington State, USA Change "netto" to "net" to email me directly "Transponders in Sailplanes" on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#22
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ASG-29/ASW-27 wing refinish
At 16:12 11 November 2006, Eric Greenwell wrote:
Gary Evans wrote: While other manufactures have been content with building what looks strong enough DG has actually participated in crash testing. This is not correct. Gerhard Waibel won an OSTIV prize for his work in cockpit safety about 20 years ago. 20 years ago, wasn't Chicago still a swamp? A lot has happened in the past 20 years. The crash tests I referenced that DG participated in were done in 1994. This is the correct link. http://www.dg-flugzeugbau.de/sicherheitscockpit-e.html Gerhard's ideas, and the ASW 24 cockpit (the first of the really crashworthy cockpits) was based on extensive testing by a group at MIT, DG claims that the DG100 from the late 70's was the first to use a double wall construction that is commonly referred to as a safety cockpit. Was the 24 done before or after that advancement? and others. In the years since then, Schleicher continues to monitor the performance of their designs by examining their gliders that are involved in crashes, either when they are brought to their shop for repair, or using pictures sent to them by the mechanics repairing the glider elsewhere. An advantage of this approach is it shows what happens in an actual crash. I suppose looking at the damage after the fact is worth doing if that’s all you have but actual crash testing will reveal more information as explained in the previously referenced test. The car manufactures don't use crash testing just because if costs a lot of money. They gave up just looking at a crashed car a long time ago. It is however expensive but what is safety worth? As a result of this testing they offer the consummate safety cockpit as an option on the 800 series and as standard on the 1000. I have been impressed with DG's improvements in safety over the years, but their single seaters cockpits still do not match what Schleicher has done. That could be termed a matter of opinion unless there is factual data available to prove that advantage. If so post it up. This page on the DG website shows that this view is shared by others (go to the 'Safety Cockpit' row): What your referring to is the old original safety cockpit. As I stated before the term safety cockpit refers to the double wall construction but DG has gone way beyond that as a result of the crash test data. What they now offer is termed a Consummate safety cockpit, which is described in the article. http://www.dgflugzeugbau.de/ash-dg-ventus-e.html These differences are not surprising. The low sides and open nose of the DG single seater cockpit pose a difficult engineering problem for the designer, compared to the greater enclosure of the Schleicher cockpits. I'm not suggesting that the DG cockpit is unsafe or inadequate, but only that it does not match what Schleicher has done. A prospective owner should consider the value of that protection along with the other features of the gliders he is considering; for example, the lower sides of the DG cockpit (particularly if the NOAH option is selected) should make baling out easier than from a Schleicher cockpit. I almost forgot NOAH another big safety step forward. Wonder who developed that? It wasn't DG was it? I think DG may have made the design available to other manufactures so it may be possible for the older guys to actually be able to get out of the high 26 side rails in an emergency. Maybe not though as some seem to believe that whatever Schleicher has done is good enough and anything more is, to steal anothers line, unnecessary like the Lexis auto park option. If you counting on higher frame rails for protection you may also want to read this. http://www.dg-flugzeugbau.de/index-e.html I was unable to find this reference, but I would like to read it. Here it is. http://www.dg-flugzeugbau.de/cockpit-e.html The point is that in a crash there is a G force beyond which survival is unlikely due to the lack of a crush zone. When the cockpit has been strengthened to the point it will not deform and kill the occupant below that force then design improvements are best turned to what else can be done to prevent fatalities(like the better visibility brought by DG style canopies and the NOAH system) rather than just adding more strength to the cockpit. DG's new Consummate safety cockpit, which another poster advised is now standard equipment on the 800/808 and 1000, was designed to prevent the temporary cockpit deformation that occured during crash testing. If DG had only been following Schleicher's method of looking at damage after the fact this safety advantage would never have occurred. -- Eric Greenwell - Washington State, USA Change 'netto' to 'net' to email me directly 'Transponders in Sailplanes' on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html 'A Guide to Self-launching Sailplane Operation' at www.motorglider.org |
#23
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ASG-29/ASW-27 wing refinish
Gary Evans wrote:
At 16:12 11 November 2006, Eric Greenwell wrote: Gary Evans wrote: While other manufactures have been content with building what looks strong enough DG has actually participated in crash testing. This is not correct. Gerhard Waibel won an OSTIV prize for his work in cockpit safety about 20 years ago. 20 years ago, wasn't Chicago still a swamp? A lot has happened in the past 20 years. That was to support my claim Schleicher lead the way to a significant improvement in cockpit crash protection. Of course, Schleicher's work did not stop with the prize or the 24. snip DG claims that the DG100 from the late 70's was the first to use a double wall construction that is commonly referred to as a safety cockpit. Was the 24 done before or after that advancement? The 24 first appeared 1988. It uses a very strong, straight, and stiff cockpit sill to maintain the integrity of the cockpit near the pilot and to absorb the loads from the fuselage and wings. The cockpit itself is single wall construction of at least three materials (some carbon, but primarily fiberglass and synthetic fabrics, including some hybrid fabrics) selected and fabricated to crush progressively to absorb energy in a controlled fashion. As I recall Waibel's explanation, the strong sill and mixed materials made it easier to achieve the desired crash protection than a double-walled cockpit. For pictures and more explanation, unfortunately only in German, go to the Schleicher website: http://tinyurl.com/y3pk9m http://tinyurl.com/tufw6 Google language tools did an almost adequate job of translating. snip This page on the DG website shows that this view is shared by others (go to the 'Safety Cockpit' row): What your referring to is the old original safety cockpit. As I stated before the term safety cockpit refers to the double wall construction but DG has gone way beyond that as a result of the crash test data. The table I referenced at http://www.dgflugzeugbau.de/ash-dg-ventus-e.html is labeled "ASH26E / DG-808C / Ventus 2cM - The Differences", so I believe it refers to current production. What they now offer is termed a Consummate safety cockpit, which is described in the article. http://www.dgflugzeugbau.de/ash-dg-ventus-e.html Included in this article is a reference to another article (http://www.dgflugzeugbau.de/sicherheitscockpit-e.html), which includes this remark: "The cockpit sides [of the other gliders] are higher than the DG sailplanes. The large canopy is one of our "Trade Marks" and leads to, we must admit, slightly less strength than the higher cockpits." And from another article: "The more enclosed cockpit of the same construction can certainly absorb a higher impact energy than one with a large canopy." So, I conclude the table I referred to accurately reflects DG's opinion. snip If you counting on higher frame rails for protection you may also want to read this. http://www.dg-flugzeugbau.de/index-e.html I was unable to find this reference, but I would like to read it. Here it is. http://www.dg-flugzeugbau.de/cockpit-e.html The point is that in a crash there is a G force beyond which survival is unlikely due to the lack of a crush zone. Quoting from the article you reference: "The more enclosed cockpit of the same construction can certainly absorb a higher impact energy than one with a large canopy." That's all I'm trying to point out. Prospective owners have to determine for themselves what particular features of each glider are important to them and their situation. My determination was, for me, a crash was more likely than a mid-air collision where G forces pinned me in the cockpit, and that the extra visibility afforded by the DG cockpit would not significantly reduce my chances of a mid-air collision. So, for this safety aspect of the glider, I prefer Schleicher's solution. If the particular safety aspects of a glider are important to a prospective owner, I urge you to talk directly to the designers (DG, Schleicher, Schempp-Hirth, etc). I have found them to generally be candid in person, pleased to speak to a pilot that is interested in safety, and eager to describe how they chose their particular solution to a difficult problem. A good place to meet them is at the SSA conventions, but I also recommend getting on a plane and visiting the factory. Flights are available in the $500 range, a cheap price for a pilot contemplating a new glider. Or, you could start with a phone call! -- Eric Greenwell - Washington State, USA Change "netto" to "net" to email me directly "Transponders in Sailplanes" on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#24
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ASG-29/ASW-27 wing refinish
If the particular safety aspects of a glider are important to a
prospective owner, I urge you to talk directly to the designers (DG, Schleicher, Schempp-Hirth, etc). I have found them to generally be candid in person, pleased to speak to a pilot that is interested in safety, and eager to describe how they chose their particular solution to a difficult problem. A good place to meet them is at the SSA conventions, but I also recommend getting on a plane and visiting the factory. Flights are available in the $500 range, a cheap price for a pilot contemplating a new glider. Or, you could start with a phone call! Eric, I, too, had a great experience corresponding directly with the factory...and with Gerhard Waibel himself when I was seeking information about a new ASW 24 15 years ago. I would also encourage anyone who has a question to do the same. For example, I had a number of questions about the canopy wire deflector bar that was then mandatory in Holland (and which I ordered and still use): how did it affect visibility, would it stop a telephone or powerline strike, was it a potential hazard to the pilot's head in a crash, etc.? Herr Waibel answered each question in a fax and mailed me a drawing of the bar with the suggestion to sit in a '24 after taping up the canopy with black tape to simulate the bar positions to check visibility. I cannot conceive of an American manufacturer being as candid and straightforward and refreshingly free of "caution: flying may be hazardous to your health" warnings. Similarly, anyone reading the DG site must also be amazed at their candor on the subject of safety. FWIW, I "voted with my wallet" and paid a price premium for my '24 over the other brands even though they were all said to have equivalent performance simply because of the enhanced safety I thought the '24 offered at the time. That it's turned out to be a wonderful glider that is still fully competitive is a bonus. Chip Bearden ASW 24 "JB" |
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