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#1
February 11th 04, 07:23 PM
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Bill Daniels wrote:
"Jim Harper" wrote in message om... Mike Borgelt wrote in message . .. some snippage The whole ship chute concept is a bit of a worry. There you are in a large heavy object with absolutely no control. With a personal chute you do have steering on most rigs nowadays. With a whole ship chute would it just ruin your day to have save and then hit the high voltage lines, fall out of a tree, fall over a cliff etc? some MORE snippage Mike Borgelt Actually, Mike, on that we disagree. Unless you are using a square canopy for your personal chute, you have very little choice on where you are gonna land...and hitting the tree, high voltage lines or over the cliff are gonna suck less if you have some aluminum or fiberglass around you. Well, that was my decision for sure. Oh, and keep in mind that as I disagree with you, I do it with all due deference to someone as distinguished in our sport as yourself (no sarcasm, I meant that!) Jim OK, crank these numbers. Consider my Nimbus 2C (Experimental, so I could install a BRS) at 650 Kilos with water (which takes 5 minutes to dump). The gear strut will give 30mm on impact and the tire will give 50mm more. The cockpit shell is just fiberglass with no crush structure. I pop a BRS at 300 meters AGL with the surface wind at 15 knots. What are my chances? Give BRS weights, 'chute diameters and descent rates. Bill Daniels Hi, Bill. Too many variables there to calculate for me, but I did visit the BRS site to gather some data. Their 680 kg. capacity system is 13.5m in diameter, weighs 16kg, and claims 7.6 m/sec descent rate @ 5000' density altitude. So in your proposed situation you're going to land with about a 15kt vertical component and a 15kt horizontal component. Translating that into G-forces and survivability I'll leave up to someone more knowledgeable... OTOH, I'm glad you picked this particular scenario, because I think its exactly where a BRS system would be invaluable. You're at 300m AGL in an unlandable ship - you pull the BRS handle and 2-3 seconds later you are under canopy. In the same situation what are your chances of popping the canopy, unbuckling, bailing, and deploying your chute in time? Now what if you're spinning, tumbling, or pointed straight down without an elevator? At a sufficient altitude where egress time isn't a big factor, I think the personal vs. BRS calculation could go either way. The closer you are to the terrain at the time of the 'incident', the more a BRS system looks like the only game in town. All IMHO, Dave Houlton 
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#2
February 11th 04, 08:11 PM
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"Dave Houlton" wrote in message ... OK, crank these numbers. Consider my Nimbus 2C (Experimental, so I could install a BRS) at 650 Kilos with water (which takes 5 minutes to dump). The gear strut will give 30mm on impact and the tire will give 50mm more. The cockpit shell is just fiberglass with no crush structure. I pop a BRS at 300 meters AGL with the surface wind at 15 knots. What are my chances? Give BRS weights, 'chute diameters and descent rates. Bill Daniels Hi, Bill. Too many variables there to calculate for me, but I did visit the BRS site to gather some data. Their 680 kg. capacity system is 13.5m in diameter, weighs 16kg, and claims 7.6 m/sec descent rate @ 5000' density altitude. So in your proposed situation you're going to land with about a 15kt vertical component and a 15kt horizontal component. Translating that into G-forces and survivability I'll leave up to someone more knowledgeable... Dave Houlton OK, Dave, good numbers. This asks me to add 16 Kilo's (35 pounds) to the non-flying parts of the glider for which I get a 15 knot descent rate when deployed (Maybe less since I will be dumping ballast like crazy.) With a 15 knot wind I would probably whack an obstacle at 20 knots. (Probably survivable - with injuries.) BTW, if I'm getting dragged by an open 'chute in that 15 knot wind, how do I dump the 'chute? I seem to recall that the price of this system is about $3500 - presumably not installed. What would be the installed price? Bill Daniels
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#3
February 11th 04, 08:35 PM
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Bill Daniels wrote:
OK, crank these numbers. Consider my Nimbus 2C (Experimental, so I could install a BRS) at 650 Kilos with water (which takes 5 minutes to dump). The gear strut will give 30mm on impact and the tire will give 50mm more. The cockpit shell is just fiberglass with no crush structure. I pop a BRS at 300 meters AGL with the surface wind at 15 knots. What are my chances? Give BRS weights, 'chute diameters and descent rates. My understanding is the "whole glider" German rescue systems will lower the glider nose down at about 40 degrees or so. If it is more level, it is likely to oscillate wildly so much the descent and impact can't be controlled. So, the landing gear is irrelevant, but the cockpit structure is extremely important. The nose must absorb the "landing". A Nimbus 2 might be a poor candidate for installing a system that won't be tested, except when you really need it. Your safety might be better served by selling the Nimbus and buying newer glider with a more crash tolerant cockpit. At least in the US, crashing while landing (meaning the last 100' of altitude) still claims more pilots than unsuccessful bailouts. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA
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#4
February 11th 04, 09:37 PM
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"Eric Greenwell" wrote in message ... Bill Daniels wrote: OK, crank these numbers. Consider my Nimbus 2C (Experimental, so I could install a BRS) at 650 Kilos with water (which takes 5 minutes to dump). The gear strut will give 30mm on impact and the tire will give 50mm more. The cockpit shell is just fiberglass with no crush structure. I pop a BRS at 300 meters AGL with the surface wind at 15 knots. What are my chances? Give BRS weights, 'chute diameters and descent rates. My understanding is the "whole glider" German rescue systems will lower the glider nose down at about 40 degrees or so. If it is more level, it is likely to oscillate wildly so much the descent and impact can't be controlled. So, the landing gear is irrelevant, but the cockpit structure is extremely important. The nose must absorb the "landing". A Nimbus 2 might be a poor candidate for installing a system that won't be tested, except when you really need it. Your safety might be better served by selling the Nimbus and buying newer glider with a more crash tolerant cockpit. At least in the US, crashing while landing (meaning the last 100' of altitude) still claims more pilots than unsuccessful bailouts. Eric Greenwell Washington State USA OK, good info Eric - now we are getting down to it. To summarize the thread so far: The BRS requires a reinforced cockpit to absorb the non-trivial landing impact forces. Most accidents involve premature termination of tow or landing errors where a BRS 'chute wouldn't help anyway. Or perhaps, mid-air collisions at an altitude where a personal 'chute is the equal for a BRS for survivability. A BRS is likely to require non-trivial pilot training and discipline in its operation and maintenance. Injuries should be expected with the used of either personal or BRS 'chutes. On the other hand, taking the 'chute off the back of the pilot and putting it on the glider adds significantly to ergonomics and comfort. The BRS can be deployed at low altitudes where a pilot with a personal 'chute is unlikely to make a successful egress. This altitude band favoring a BRS probably expands where the pilot is old or infirm. Maybe it's something to think about on a new glider but retrofitting an older glider is problematical. A BRS is perhaps a useful option but not a panacea. I remain skeptical but open to ideas. Bill Daniels
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#5
February 12th 04, 12:00 AM
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Bill Daniels wrote:
Eric Greenwell wrote My understanding is the "whole glider" German rescue systems will lower the glider nose down at about 40 degrees or so. If it is more level, it is likely to oscillate wildly so much the descent and impact can't be controlled. So, the landing gear is irrelevant, but the cockpit structure is extremely important. The nose must absorb the "landing". A Nimbus 2 might be a poor candidate for installing a system that won't be tested, except when you really need it. Your safety might be better served by selling the Nimbus and buying newer glider with a more crash tolerant cockpit. At least in the US, crashing while landing (meaning the last 100' of altitude) still claims more pilots than unsuccessful bailouts. To summarize the thread so far: The BRS requires a reinforced cockpit to absorb the non-trivial landing impact forces. Most accidents involve premature termination of tow or landing errors where a BRS 'chute wouldn't help anyway. Or perhaps, mid-air collisions at an altitude where a personal 'chute is the equal for a BRS for survivability. A BRS is likely to require non-trivial pilot training and discipline in its operation and maintenance. Injuries should be expected with the used of either personal or BRS 'chutes. On the other hand, taking the 'chute off the back of the pilot and putting it on the glider adds significantly to ergonomics and comfort. The BRS can be deployed at low altitudes where a pilot with a personal 'chute is unlikely to make a successful egress. This altitude band favoring a BRS probably expands where the pilot is old or infirm. Maybe it's something to think about on a new glider but retrofitting an older glider is problematical. A BRS is perhaps a useful option but not a panacea. I remain skeptical but open to ideas. I think that's a good summary. For me, it's not possible because I have a motor glider. That also excludes about half the German production. I don't think the on-ground safety aspects are difficult - remember, these units have been used successfully (BRS lists 159 saves so far) in ultralight aircraft for many years and they have systems for the Cessna 150, 172, 180, and Cirrus, so it's not like the basic system is new. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA
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#6
February 12th 04, 01:24 AM
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"Bill Daniels" wrote in message ...
OK, crank these numbers. Consider my Nimbus 2C (Experimental, so I could install a BRS) at 650 Kilos with water (which takes 5 minutes to dump). The gear strut will give 30mm on impact and the tire will give 50mm more. The cockpit shell is just fiberglass with no crush structure. I pop a BRS at 300 meters AGL with the surface wind at 15 knots. What are my chances? Give BRS weights, 'chute diameters and descent rates. Bill Daniels Hi, Bill. Please don't take what follows in any sort of argumentitive way. I've played out the scenario you describe in making my decision to buy the BRS. As I reread it, it sounds harsh, but it certainly isn't meant harshly...just heart-felt. Thanks for taking it in the spirit it is intended...Dave answered the primary question you had...a 15 knot collision with the earth is gonna hurt for sure. However let's put you in your Nimbus, busted...at around 980 feet, plummeting earthward at...oh, let's just say...80 mph. You need to pull your ripcord at a minimum of, what, 350 feet? That would be borderline...I'd rather try it at 500 feet. Ok, you have (117 fps down) 3-4 seconds to open (jettison) your canopy, unfasten your belts and get out of and away from your glider and pull the ripcord. Pretty much half the amount of time it took to read that last sentence out loud. Do you really think you can? Add the g-forces associated with any significant damage and just making the decision...If you can, you are a better man than I. Put me in the same position in my BRS equipped glider...I need to reach over my right shoulder and pull...much the same move as your first move to jettison the canopy...but in a different direction, of course :-). I am now under canopy. I am hanging nose down (I figure around 45 degrees or so) I've got (around 22 fps down) 20 seconds (assuming I wind up under canopy at 500 feet) to get my landing gear down, tighten my straps, brace and take the impact. The glider hits nose first (with an impact which is a significant fraction of the total force...let's call it 75% of the force...so about what I would get by running into a brick wall at 12 mph), and the rest of the force is dissipated by the glider rotating down to the landing gear...one would expect that it would take the rest with minimum loading on my body. I'm hurting but alive, most likely. You're dead, most likely. God forbid either one of us explore this scenario...but I prefer my chances over the non-BRS equipped glider. Jim
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#7
February 12th 04, 03:22 AM
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Here is a link that shows Jim's HP-16 BRS installation.
http://www.soaridaho.com/Schreder/HP...S_in_HP-16.htm The HP-16's stub box spar across the fuselage is ideal for a BRS application. Wayne http://www.soaridaho.com/Schreder "Jim Harper" wrote in message om... "Bill Daniels" wrote in message ... OK, crank these numbers. Consider my Nimbus 2C (Experimental, so I could install a BRS) at 650 Kilos with water (which takes 5 minutes to dump). The gear strut will give 30mm on impact and the tire will give 50mm more. The cockpit shell is just fiberglass with no crush structure. I pop a BRS at 300 meters AGL with the surface wind at 15 knots. What are my chances? Give BRS weights, 'chute diameters and descent rates. Bill Daniels Hi, Bill. Please don't take what follows in any sort of argumentitive way. I've played out the scenario you describe in making my decision to buy the BRS. As I reread it, it sounds harsh, but it certainly isn't meant harshly...just heart-felt. Thanks for taking it in the spirit it is intended...Dave answered the primary question you had...a 15 knot collision with the earth is gonna hurt for sure. However let's put you in your Nimbus, busted...at around 980 feet, plummeting earthward at...oh, let's just say...80 mph. You need to pull your ripcord at a minimum of, what, 350 feet? That would be borderline...I'd rather try it at 500 feet. Ok, you have (117 fps down) 3-4 seconds to open (jettison) your canopy, unfasten your belts and get out of and away from your glider and pull the ripcord. Pretty much half the amount of time it took to read that last sentence out loud. Do you really think you can? Add the g-forces associated with any significant damage and just making the decision...If you can, you are a better man than I. Put me in the same position in my BRS equipped glider...I need to reach over my right shoulder and pull...much the same move as your first move to jettison the canopy...but in a different direction, of course :-). I am now under canopy. I am hanging nose down (I figure around 45 degrees or so) I've got (around 22 fps down) 20 seconds (assuming I wind up under canopy at 500 feet) to get my landing gear down, tighten my straps, brace and take the impact. The glider hits nose first (with an impact which is a significant fraction of the total force...let's call it 75% of the force...so about what I would get by running into a brick wall at 12 mph), and the rest of the force is dissipated by the glider rotating down to the landing gear...one would expect that it would take the rest with minimum loading on my body. I'm hurting but alive, most likely. You're dead, most likely. God forbid either one of us explore this scenario...but I prefer my chances over the non-BRS equipped glider. Jim
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#8
February 11th 04, 08:29 PM
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#9
February 12th 04, 02:02 PM
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Mike Borgelt wrote in message . ..
snip I once saw a movie of the BRS drop test on a C150 simulating its arrival under a deployed BRS chute. I doubt that the Cessna was useable again even though it was a symmetrical level attitude when it hit with no drift. I'd hate to hit at a similar descent rate in a glider. In Oz we've had a few people do hard landings in the last couple of years. Some are considered lucky to be walking but the gliders are repairable. Air bags may be essential. Of course I would expect that the glider wouldn't be reusable after using the BRS...I would only pull the thing is a situation that would lead to me leaving the airplane, should I have had a parachute. In that case, the airplane is a write-off. As I have previously recounted, I have the thing set up to lower the airplane nose down somewhat...one hopes that the forces will be somewhat dissipated by the landing attitude. Of course the risk of injury exists for a successful bail-out as well. It's interesting that in this dialogue folks worry about hitting under canopy IN the glider, and don't discuss the myriad of risks associated with hitting under canopy OUT of the glider. I parachuted in the military and in sport. I have seen more than a few broken bones, broken backs, internal injuries and others. And those were with trained parachutists jumping under controlled situations and the best possible conditions, with prepared...or at least planned...drop-zones. I don't think that to be the case for the typical emergency bail-out from a broken glider. We've had this debate on this board more than once and in each case, it seems to me that we set a double standard...somehow we assume that the guy who leaves the glider and deploys a round canopy for his first parachute jump ever will arrive on the ground unscathed...and the guy who pulls the BRS lever is subjecting himself to an extraordinary amount of risk, because he _might_ hit the ground in a manner that _might_ lead to injury. The reality is that when the decision to deploy either your personal canopy OR the BRS is made, your only other option is very likely death. If I can fly the airplane, I am going to fly the airplane. If my airplane is damaged beyond the point that I can fly it, I am going to deploy. If when I land I am injured, I still firmly believe that I am going to be far better off than if I had ridden the glider to the ground without a parachute. And no question...if I had room in the cockpit/no weight constraints, I would ALSO wear a square emergency parachute for those cases where I AM high enough to choose that egress. I think that I would STILL have the BRS, though, for the collision in the pattern or the like. And I have far more experience under a parachute canopy than 99% of glider pilots. Are your gliding club members smart enough to avoid inadvertent deployment of a ballistic chute in the hangar? At one club I used to belong to the new ASW20B got wheeled up twice in a month or so - in the hangar as people said "what does this lever do?". In the chute case you would hope nobody else was standing behind the wing looking into the cockpit. The BRS system has a remove before flight safety pin. With the pin in place, the BRS cannot be deployed. If some yahoo starts playing with my glider and REMOVES the safety tag/pin and then pulls the handle? I would, under those circumstances, hope he DOES have his face in front of it. He will certainly have exceeded any reasonable "what does THIS lever do" level of curiosity in my book. About 12 years ago we did a precision altimeter project for an RAAF test project. The chief aero engineer of the research and development unit was building an ultralight of his own design. I asked if he was fitting a BRS chute. He said he was designing the aircraft basically to high enough standards that like a FAR 23 power plane it was reliable enough in its structure and control systems that flying without a chute was a good risk. His opinion was that the whole ship chutes at the time couldn't meet their claimed descent rates with the chute sizes used. His first job had been with a parachute manufacturer so I had to take some notice of his opinion. Mike Borgelt One hopes one's glider isn't going to go poof in flight. However, certificated gliders HAVE gone poof in flight. Further, our sport has a much higher (at least theoretical) risk of collision in the air than the usual spam-can. My glider is better built than most of them out there, and I don't carry the BRS in expectation of a wing spontaneously folding up. Nor do I plan on running into someone in a gaggle. But if it happens, I am comforted in knowing that it's there. BRS parachutes DO meet their claimed descent rates. Look at their data. They have tested these things extensively. I would suggest that an aero engineer who had worked for a parachute manufacturer may have had a bias just like any other fellow...and that WAS 12 years ago. I guess that if you are making a decision based on one person's opinion during the last millenium, no matter how experienced, well, more power to you. I prefer doing a bit more research than that. Once again, with all due respect, and no offense intended. Jim
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#10
February 12th 04, 04:28 PM
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Jim Harper wrote:
Are your gliding club members smart enough to avoid inadvertent deployment of a ballistic chute in the hangar? At one club I used to belong to the new ASW20B got wheeled up twice in a month or so - in the hangar as people said "what does this lever do?". In the chute case you would hope nobody else was standing behind the wing looking into the cockpit. The BRS system has a remove before flight safety pin. With the pin in place, the BRS cannot be deployed. If some yahoo starts playing with my glider and REMOVES the safety tag/pin and then pulls the handle? I would, under those circumstances, hope he DOES have his face in front of it. He will certainly have exceeded any reasonable "what does THIS lever do" level of curiosity in my book. THe BRS web site says it is a 35-40 pound pull, a rather stout effort, and well beyond what you need to collapse the gear on an ASW20B. A key lock could be used to prevent removal of the safety tag and pin, if one is really concerned. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA
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