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#11
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In article ,
Gezellig wrote: On Thu, 09 Jul 2009 17:44:28 -0500, Jim Logajan wrote: http://www.ntsb.gov/ntsb/brief.asp?e...07X17184&key=1 How long after first impact should it take for the ELT to kick out a call on frequency? If the ELT isn't destroyed in the crash, it usually doesn't go off until the wreckage is hauled away. 406 ELTs are slightly better then 121.5 ELTs in terms of false positives (ELT goes off with no crash), but in real crashes, they both have extremely high failure rates. I don't have access to the stats any more, but when I was in CAP, something like 98% of ELT searches where false activations, and ELTs failed to activate in about 95% of all crashes. Numbers are from memory, so might be off by a bit, but the magnitude of the issue should be obvious. Being on flight following and/or getting off a Mayday before crashing greatly increase your chances of being found. Manually triggering your ELT before impact might help, if it survives the impact. John -- John Clear - http://www.clear-prop.org/ |
#12
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On Jul 10, 6:48*am, Gezellig wrote:
CAP was combing the area by the NTSB with no report of transmission so I suppose we can extrapolate that a severe enough impact can render the ELT useless. I am guessing where the AC took the initial hit would be important too in relation ot the positioning of the ELT in the AC.- Hide quoted text - - Show quoted text - ....i think we can infer from the following description of damage, from the information found on the NTSB Summary's "Full Narrative" link, that listening for an ELT signal, regardless of where it was installed in the aircraft, was moot: "The airplane was severely fragmented and a severe post crash fire burned most of the structure and surrounding vegetation. The first evidence of ground contact was a boulder with paint transfers on it consistent with the left main wheel and the belly of the airplane. " "All of the cockpit instruments and avionics were destroyed. Pieces of instruments were found scattered throughout the debris field. The airplane's ELT was destroyed; numerous pieces of its orange plastic case and internal circuit board components were found scattered in the debris field." ....and this: "The engine sustained severe impact damage. The crankshaft was broken off about 3.5 inches inside the nose case, a piece of the nose case was broken out, and the front thrust bearing was partially extruded, bent and deformed. All accessories and the oil sump were stripped from the engine. The cylinder heads of the right side cylinders (#1 and #3) were destroyed; the impact crush angle measured at the lower #1 cylinder barrel was 39 degrees." ....and finally: "The front seat frame was bent, deformed and crushed to a size about one third of its original dimension." S McF |
#13
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On Jul 9, 10:14*pm, Mike Ash wrote:
If it can happen to him, it could happen to you! And that's the most important thing this low hours pilot takes from every crash report. I'm not afraid to die, I just don't want to bend a perfectly good airplane in the process. As this relates to trucking, an area where I have more expertise, it is often the most experienced drivers who are involved in the most serious incidents. ----- - gpsman |
#14
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On Fri, 10 Jul 2009 15:44:52 +0000 (UTC), John Clear wrote:
In article , Gezellig wrote: On Thu, 09 Jul 2009 17:44:28 -0500, Jim Logajan wrote: http://www.ntsb.gov/ntsb/brief.asp?e...07X17184&key=1 How long after first impact should it take for the ELT to kick out a call on frequency? If the ELT isn't destroyed in the crash, it usually doesn't go off until the wreckage is hauled away. 406 ELTs are slightly better then 121.5 ELTs in terms of false positives (ELT goes off with no crash), but in real crashes, they both have extremely high failure rates. Tell me about it. Mine went off on a maintenance tow ![]() I don't have access to the stats any more, but when I was in CAP, something like 98% of ELT searches where false activations, and ELTs failed to activate in about 95% of all crashes. Numbers are from memory, so might be off by a bit, but the magnitude of the issue should be obvious. Holy s**t, I never knew, now I feel better. Being on flight following and/or getting off a Mayday before crashing greatly increase your chances of being found. Manually triggering your ELT before impact might help, if it survives the impact. John Thx. |
#15
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"Gezellig" wrote in message
... On Fri, 10 Jul 2009 15:44:52 +0000 (UTC), John Clear wrote: In article , Gezellig wrote: On Thu, 09 Jul 2009 17:44:28 -0500, Jim Logajan wrote: http://www.ntsb.gov/ntsb/brief.asp?e...07X17184&key=1 How long after first impact should it take for the ELT to kick out a call on frequency? If the ELT isn't destroyed in the crash, it usually doesn't go off until the wreckage is hauled away. 406 ELTs are slightly better then 121.5 ELTs in terms of false positives (ELT goes off with no crash), but in real crashes, they both have extremely high failure rates. Tell me about it. Mine went off on a maintenance tow ![]() I don't have access to the stats any more, but when I was in CAP, something like 98% of ELT searches where false activations, and ELTs failed to activate in about 95% of all crashes. Numbers are from memory, so might be off by a bit, but the magnitude of the issue should be obvious. Holy s**t, I never knew, now I feel better. Being on flight following and/or getting off a Mayday before crashing greatly increase your chances of being found. Manually triggering your ELT before impact might help, if it survives the impact. John Thx. This seems to really involve more than one subject: 1) In the particular case of Steve Fossett; it appears that timely location would have made no difference at all for Mr Fossett, but admittedly would have saved a tremendous amount of effort and also expedited and simplified the settlement of his estate. (As a side note, simply as serendipity, the search for Mr Fossett did appear to uncover the answers to some other misteries which had been under investigation for some time.) 2) One of the major arguments for the adoption of the 406Mhz system was the ever expanding use of the 121.5Mhz beacons by hikers, boaters, and probably others as well. IIRC, the new beacons were supposed to be available for the various uses so that searchers would have greater reason to presume which type of incident might be involved. (I have not ket up, and don't know whether the change has helped; but there do seem to be some similarities to the use of other emergency response systems.) 3) When I was working on avionics, it seemed to me that about three fourths of all radio problems that I saw were airframe wiring as opposed to inside the radios. The radios themselves have probably gotten more reliable in the years since, so I would be amazed if the change to 406Mhz has made much more difference in physical reliability than would have been the case if all of the old 121.5Mhz beacons were completely removed and then completely reinstalled during the same time period. 4) In the event that most false or inadvertant activations actually occur on airports, which would certainly make sense, then there should be a fairly simple and cost effective method to observe, locate and deactivate the beacons in question. 5) Crashes that occur away from the airports, where a search operation is needed, probably involve a very small percentage of pilots and passengers over their lifetimes. I really don't know how small that percentage is; but if the percentage is as small as I suspect, then there is some question about whether any system makes sense--with the exception of post crash beacons in aircraft carrying passengers commercially and possibly combat aircraft. (If the lifetime probability, for the participants in the activity, is only one or two percent, then it is long past time to reopen the debate about general aviation fleetwide use in terms of its value versus cost in money, time, effort, freedom and privacy.) Peter |
#16
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In article ,
Peter Dohm wrote: 2) One of the major arguments for the adoption of the 406Mhz system was the ever expanding use of the 121.5Mhz beacons by hikers, boaters, and probably others as well. IIRC, the new beacons were supposed to be available for the various uses so that searchers would have greater reason to presume which type of incident might be involved. (I have not ket up, and don't know whether the change has helped; but there do seem to be some similarities to the use of other emergency response systems.) 406Mhz ELT/EPIRB/PRB emit a distinct identifier and are supposed to be registered, so false positives can often be taken care of with a phone call and not a SAR team going out at 2am looking for it. 4) In the event that most false or inadvertant activations actually occur on airports, which would certainly make sense, then there should be a fairly simple and cost effective method to observe, locate and deactivate the beacons in question. Most false activations are on airports (or marinas, EPIRBs are on 121.5/406 as well). Tracking down which specific plane/boat is still very time consuming with 121.5 beacons. With 406 beacons, it is much easier, if they are registered. Especially at airports, the metal hangars make finding the activated 121.5 beacon very challenging since the signal reflects all over the place. Another unfun one to track is when someone sends a ELT/EBIRP in for servicing, but doesn't remove the batteries. UPS trucks have plastic tops, so the signal hits the satellite just fine, but tracking the moving target from the ground is nearly impossible. 5) Crashes that occur away from the airports, where a search operation is needed, probably involve a very small percentage of pilots and passengers over their lifetimes. I really don't know how small that percentage is; but if the percentage is as small as I suspect, then there is some question about whether any system makes sense--with the exception of post crash beacons in aircraft carrying passengers commercially and possibly combat aircraft. (If the lifetime probability, for the participants in the activity, is only one or two percent, then it is long past time to reopen the debate about general aviation fleetwide use in terms of its value versus cost in money, time, effort, freedom and privacy.) ELTs were originally mandated by Congress after Congressman Hale Boggs's plane went missing in 1972 (and still hasn't been found). There never was a serious discussion of the cost/benefits of ELTs. http://en.wikipedia.org/wiki/Hale_Bo...nce_and_search I haven't seen any stats, but I feel the number of survivable crashes where an ELT assisted in the rescue is very small. On the water, a large number of rescues have been the result of EPIRB activations. I've heard ELTs referred to as ballast, since the most useful thing they do is move the CG aft. John -- John Clear - http://www.clear-prop.org/ |
#17
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On Sat, 11 Jul 2009 09:37:22 -0400, Peter Dohm wrote:
5) Crashes that occur away from the airports, where a search operation is needed, probably involve a very small percentage of pilots and passengers over their lifetimes. I really don't know how small that percentage is; but if the percentage is as small as I suspect, then there is some question about whether any system makes sense--with the exception of post crash beacons in aircraft carrying passengers commercially and possibly combat aircraft. (If the lifetime probability, for the participants in the activity, is only one or two percent, then it is long past time to reopen the debate about general aviation fleetwide use in terms of its value versus cost in money, time, effort, freedom and privacy.) Peter I was told but never confirmed that it was a prerequisite for insuring the plane and, potentially, the pilot. |
#18
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On Sun, 12 Jul 2009 04:34:43 +0000 (UTC), John Clear wrote:
I haven't seen any stats, but I feel the number of survivable crashes where an ELT assisted in the rescue is very small. On the water, a large number of rescues have been the result of EPIRB activations. I've heard ELTs referred to as ballast, since the most useful thing they do is move the CG aft. Do you know if there is a mandated position on any plane where the ELT must be installed? Or is it mfg preference (so to properly balance CG, etc) |
#19
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Gezellig wrote:
On Sat, 11 Jul 2009 09:37:22 -0400, Peter Dohm wrote: 5) Crashes that occur away from the airports, where a search operation is needed, probably involve a very small percentage of pilots and passengers over their lifetimes. I really don't know how small that percentage is; but if the percentage is as small as I suspect, then there is some question about whether any system makes sense--with the exception of post crash beacons in aircraft carrying passengers commercially and possibly combat aircraft. (If the lifetime probability, for the participants in the activity, is only one or two percent, then it is long past time to reopen the debate about general aviation fleetwide use in terms of its value versus cost in money, time, effort, freedom and privacy.) I was told but never confirmed that it was a prerequisite for insuring the plane and, potentially, the pilot. I flew a plane for seven-eight years without an ELT, and the insurance carrier never seemed to care. That was just a liability policy, though. Ron Wanttaja |
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