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#211
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On 5 Jul 2005 21:16:28 GMT, "Ian Johnston"
wrote: As Bert already stated: As long as you stay within the safe speed range, there is no way to exceed the stress limits of the glider - simply there isn't enough lift available. Um, must check, but am pretty sure angle of attack influences lift as well... Indeed... but if you stay within the allowed speed range, you'll get a stall if you pull too hard instead of overstressing the glider. Besides: I've never seen an ASW-20 break a weak link on my home airfield. We were using the blue ones for the 20. So why would anyone fly with a 33% over strength link? Ask Bert - he's got his reasons! Unless the glider hits a gust, or the pilot pulls back too hard, or the throttle of the winch suddenly shoots open or ... Nope. Either of these cases results either in a stall (pulling back too hard) or overspeed... but does not lead to overstress. If you leave the safe speed range, you pull the release... problem solved immediately. It's been ages since I did a winch launch in an SF34 and I really can't remember much about it, but surely in that case the manufacturer should be approached about changing the link officially, and issuing a strengthening modification if required? Indeed... but nothing has happened. I wonder if Centrair changed this on the Alliance 34? I must check the handbook - we have one at my current (all aerotow!) club. Please do - I'd be interested if it's different for the Alliance 34. Bye Andreas |
#212
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TOST WEAK LINKS.
The BGA now recommend as follows: "The weak-link assembly incorporates a link to suit the glider being launched (see Appendix E) and this remains with the parachute assembly. (At some sites, a selection of weak-links, suitable for launching each of the glider types in the club’s fleet, may remain permanently attached to the parachute assembly. This is convenient, but calls for extra care in ensuring that the correct link is chosen for each launch.) "N.B. The Tost weak-link system is designed for use either with a single link or with double links. If the double-link system is employed, it is essential that the links are of different design (the main link having round holes and the reserve link having slotted holes). Using two weak links, each of the same design doubles the breaking load and renders the whole assembly ineffective. Because of the risk of assembling two weak links incorrectly, the single-link assembly is recommended as the more foolproof system." This is a quote from the BGA Winch Operators Manual , page 20, http://www.gliding.co.uk/forms/clubm...t/winchops.pdf . This recommendation was made after an Olympia 463 had structural failure while being winch launched, and the pilot was killed. It was found that there was weakness in the wings due to water ingress while in the trailer, and a double strength weak link had been used; it was not established which was the critical factor. This accident was on 13th July 1996, BGA Ref: 79/96, AAIB Ref: EW/C96/7/5. W.J. (Bill) Dean (U.K.) Remove "ic" to reply. "Ian Johnston" wrote in message news:dzZo7CxomoOm-pn2-1IU6gvmrdIOd@localhost... On Tue, 5 Jul 2005 15:59:24 UTC, M B wrote: Is there any commonly known way to test a weak link non-destructively (other than launching a glider)? The Tost system uses two in parallel, one slightly longer than the other. Whoever hooks up the glider should always check that both links are intact and that only one is taking the load. Ian |
#213
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In article ,
"Bert Willing" wrote: I have seen (from the ground) quite a couple of critical situations resulting from fatigued weak link breakage, and I prefer to watch angle of attack and speed, and pull the knob myself if necessary. With all due respect, Bert, if a weak link breakage creates a "critical" situation, then the pilot has a training issue which needs to be resolved. Sounds like some cable break practice is in order. A launch isn't supposed to be a hazardous maneuver. If there's -any- stage during the launch where someone wouldn't be comfortable with the cable breaking, they need to find an instructor and get some remedial training. - mark |
#215
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Bert, if you mean that the consequences of mishandling the controls is
higher during a aborted launch, I agree. However, that risk is more than adequately managed through training. I feel confident that no unmanageable situation will arise that will hurt me or my students as long as they fly the way they were taught. I can't say that about air tow. While all the risks involved in winch launch are manageable, situations beyond my control can happen with air tow. Bill Daniels "Bert Willing" wrote in message ... With all due respect from my side, I am well trained to aborted launches, to high-speed passes below 20ft along a runway, and to circeling inverted. However, each of these situations presents an elevated risk as the margin for errors is reduced. Now if you think that an aborted winch launch does not represent an elevated risk - keep on dreaming. -- Bert Willing ASW20 "TW" "Mark Newton" a écrit dans le message de news: ... In article , "Bert Willing" wrote: I have seen (from the ground) quite a couple of critical situations resulting from fatigued weak link breakage, and I prefer to watch angle of attack and speed, and pull the knob myself if necessary. With all due respect, Bert, if a weak link breakage creates a "critical" situation, then the pilot has a training issue which needs to be resolved. Sounds like some cable break practice is in order. A launch isn't supposed to be a hazardous maneuver. If there's -any- stage during the launch where someone wouldn't be comfortable with the cable breaking, they need to find an instructor and get some remedial training. - mark |
#216
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In article ,
"Bert Willing" wrote: With all due respect from my side, I am well trained to aborted launches, to high-speed passes below 20ft along a runway, and to circeling inverted. However, each of these situations presents an elevated risk as the margin for errors is reduced. Now if you think that an aborted winch launch does not represent an elevated risk - keep on dreaming. You didn't say "elevated risk". You said "critical situation," which means something completely different to "elevated risk." You are now pretending you didn't say that for the sole purpose of taking umbrage at my comments, which you would have me believe are wrong. They are not wrong, and I stand by my comments. Perhaps if you stood by yours instead of redefining the language you used we'd be able to walk away from this without any disagreement. - mark "Mark Newton" a écrit dans le message de news: ... In article , "Bert Willing" wrote: I have seen (from the ground) quite a couple of critical situations resulting from fatigued weak link breakage, and I prefer to watch angle of attack and speed, and pull the knob myself if necessary. With all due respect, Bert, if a weak link breakage creates a "critical" situation, then the pilot has a training issue which needs to be resolved. Sounds like some cable break practice is in order. A launch isn't supposed to be a hazardous maneuver. If there's -any- stage during the launch where someone wouldn't be comfortable with the cable breaking, they need to find an instructor and get some remedial training. |
#217
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From an elevated risk, you have critical situations more easily happening.
Being well trained for interruptions is to my mind mandatory for anybody who wants to make winch launching. -- Bert Willing ASW20 "TW" "Mark Newton" a écrit dans le message de news: ... In article , "Bert Willing" wrote: With all due respect from my side, I am well trained to aborted launches, to high-speed passes below 20ft along a runway, and to circeling inverted. However, each of these situations presents an elevated risk as the margin for errors is reduced. Now if you think that an aborted winch launch does not represent an elevated risk - keep on dreaming. You didn't say "elevated risk". You said "critical situation," which means something completely different to "elevated risk." You are now pretending you didn't say that for the sole purpose of taking umbrage at my comments, which you would have me believe are wrong. They are not wrong, and I stand by my comments. Perhaps if you stood by yours instead of redefining the language you used we'd be able to walk away from this without any disagreement. - mark "Mark Newton" a écrit dans le message de news: ... In article , "Bert Willing" wrote: I have seen (from the ground) quite a couple of critical situations resulting from fatigued weak link breakage, and I prefer to watch angle of attack and speed, and pull the knob myself if necessary. With all due respect, Bert, if a weak link breakage creates a "critical" situation, then the pilot has a training issue which needs to be resolved. Sounds like some cable break practice is in order. A launch isn't supposed to be a hazardous maneuver. If there's -any- stage during the launch where someone wouldn't be comfortable with the cable breaking, they need to find an instructor and get some remedial training. |
#218
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A couple of points. After the first launch a weak link
is no longer at it's design strength, this reduces with every launch. After 20 launches check the hole in the centre of the tost weak link you will find it is slightly oval and if you run your fingers along the edges you will feel a depression. Unfortunately many weak link 'holders' do not allow this check to be made easily. A weak link will eventually break just through 'normal' use if it is not replaced. Up to the point at which the cable is at an angle of more than 60 deg to the ground it is best if the cable is released under full tension and the result dealt with as a launch failure. What should be avoided is lowering the nose early in the launch and pulling the release especially if the launch is fast. It is very easy for the parachute to open and fly and glider catch up with it in those circumstances. I have seen the cable wrapped round the wing when a pilot lowered the nose because he was going to enter cloud and then pulled the release. It should always be the other way round. Lowering the nose when the glider is directly over the winch, at the top of the climb is fine. At 12:48 11 July 2005, Mark Newton wrote: In article , 'Bert Willing' wrote: I have seen (from the ground) quite a couple of critical situations resulting from fatigued weak link breakage, and I prefer to watch angle of attack and speed, and pull the knob myself if necessary. With all due respect, Bert, if a weak link breakage creates a 'critical' situation, then the pilot has a training issue which needs to be resolved. Sounds like some cable break practice is in order. A launch isn't supposed to be a hazardous maneuver. If there's -any- stage during the launch where someone wouldn't be comfortable with the cable breaking, they need to find an instructor and get some remedial training. - mark |
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