信任危机：主伞钩因金属疲劳而折断

关注这事的人知道，事情闹大后，在2005.3 DHV以AustriAlpin未能按时出具疲劳测试报告的情况下，通告全世界全面禁止AustriAlpin钩的悬挂滑翔使用。随后2005.6月 AustriAlpin提交报告声称他们的钩子没有问题。DHV在6月发部了解除警告。比较诡异的是，在今天的DHV网站上，解除警告不见了，停用警告依然存在。而生产厂商AustriAlpin的拳头产品--铝制主伞钩Parafly从AustriAlpin的网站消失了，仅留下了原来推荐双人伞使用的钢质钩PowerFly~~

关于那个史上著名的捷克断钩的结论仍然存在很大争议。生产商对于伞钩断裂的解释是，在OpenGate的情况下，过载造成伞钩断裂。但是反对者持不同意见：

断裂事故报告中的主伞钩

AustriAlpin的反对者提醒大家注意，断裂面有一个平滑的撕裂面。

破坏性试验后的主伞钩:
在试验室中，在不锁闭的情况下，被测试机器拉断的钩子，其表面呈现另外的样子。

外行看热闹，至于金属断裂面的具体情况，还得请相关专家来评判了。我们只能在脑子里放个问号而已。

随后DHV进行了更大范围的调查，发现疲劳测试中却发现了另一个惊人的故事。这个问题波及到了许多许多的钩子，不仅仅是AustriAlpin。

每种材料发生疲劳的变形不一样，疲劳测试中每个伞钩负载数十KG，这点份量远远达不到拉断的程度（1.5 吨），但是由于制造精度的原因，伞钩关闭后上下钩咬合部分有0.2~2.5mm的缝隙。如果这个咬合所造成的形变大于金属疲劳形变的门限，那么钩子无论是否锁闭，都会导致金属疲劳。在反复的加载和卸掉数十KG力的情况下，会导致出现金属疲劳导致的断裂。Aluminium as well as steel karabiners can be affected.。DHV特别指出无论是铝制品还是钢制品，都将受到金属疲劳影响。

DHV给我们的建议是，如果你在安装伞带的时候，需要用力按才能将扣子合上，那么你的主伞钩已经变形，需要立刻更换主伞钩。

整个滑翔伞世界陷入了一场信心危机当中，很多人用伞绳自制了第二保险锁，从今年PWC世界冠军的主伞钩使用了德国的 Charly Pinlock穿轴式伞钩，有人干脆用最普通的螺旋钢伞钩--就是我们连接副伞的那个。另外一些企业不失时机地推出了制式保险绳索，以实现大家Double伞钩的愿望^^。

好了，最后，DHV的相关测试机构给大家指出一条明路，来测试你的主伞钩咬合点Fk是否会影响其寿命。

先看一下每一个主伞钩的粗略测试数据，其中Fou是可以造成金属疲劳的拉力。Fk是测试机构采样测试中的伞钩锁咬合所需拉力。如果你的伞钩的Fk大于Fou，那么，请立刻停止使用你的伞钩，因为你的伞钩无论上锁与否，都将发生金属疲劳。

测试方法：

1. 将伞钩悬挂在一个结实的地方。
2. 用一个家用体重计或更精准的称，按照上表中数据，在你的伞钩下悬挂负重。负重就是Fk。举例:如果你用铝制的Supair Alu，那么你需要准备少于70KG的坐袋+配重。如果你用铝制AustriAlpin，你需要25KG以内的配重。
3. 悬挂配种的方法如图2，3所示，距离中心点1厘米，这正是DHV测试的方法。
4. 如果配重Fk导致伞钩闭合，那么你将很难将其打开，如果此时的Fk没有超过疲劳拉力Fo，那么你的伞钩是安全的。否则你的伞钩正在承受金属疲劳的折磨，在一个折磨期之后，一个很轻的拉力都会让你听到“咔嚓”一声。

DHV安全警告:

http://www.dhv.de/typo/Safety_Notes.3939.0.html

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Airworthiness advisory
Paraglider harness, harnesscarabiner Parafly Automatic from AustriAlpin

After several fractures of aluminium harnesscarabiner Parafly Automatic from AustriAlpin during use in 2003 and 2004, the manufacturer was asked to prove fatigue strength against vibration. The last deadline was 1. March 2005. This proof has not been shown up today. Tests conducted in the order of DHV to aluminium harnesscarabiner Parafly Automatic from AustriAlpin showed low values of fatigue strength against vibration. The in flight safety is gravely affected. The DHV has decided on the following precautionary safety measure:

All harness carabiners Parafly Automatic by Austrialpin, must not be used any more.

The airworthiness instruction comes into effect with the publishing of the NFGH (Paraglider and Hanglider news).

Gmund, 09.03.2005
Klaus T?nzler
Managing Director

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Safety note

Paraglider harness, Hangglider harness karabiners Finsterwalder GmbH
Investigations by the DHV and the company Finsterwalder GmbH have shown that many paraglider- and hangglider karabiners are not fatigue resistant below the point of actuation by gravity of their catch. Aluminium as well as steel karabiners can be affected.

Harness karabiners with conventional catch fasteners show different fatigue resistance over and below the point of actuation by gravity of their catch. The point of actuation by gravity has not been investigated by the karabiner manufacturers and is subject to an unknown tolerance range.

Endangered above all, are those karabiners, by which the point of actuation by gravity in the fastening catch occurs by a loading (Fk) that is larger than the fatigue strength (Fou) - reduced by 20% - established for the fatigue strength with open catch by the least favourable harness arrangement. By these karabiners, load oscillation tensions can arise on the inner bends of the karabiner, which are greater than the fatigue strength of the material. The reduction of 20% is a result of the safety coefficient of 1.2 with which the fatigue strength must be provided in order to take account of fluctuations in material and finishing. There is no warning before a breakage due to metal fatigue, as pronounced deformation does not occur, and is therefore not recognisable.

A karabiner fastener is "actuated by gravity" when there is no play present in the fastener. Karabiners with catch fasteners exhibit "catch play" from 0.2 mm to 2.5 mm. "Actuation by gravity" first occurs when the catch play is reduced to zero by deformation as a result of loading (Fk).

The point of actuation by gravity Fk can be roughly established by every pilot by testing the size of the load at which the karabiner fastener can still be easily opened.

The DHV has requested the karabiner manufacturers to establish and announce exact values for the fatigue strength Fou by March 1st 2005. This deadline has now been extended to the middle of April.

Endangered karabiners as defined above are not airworthy.

The Finsterwalder GmbH therefore takes the following precautionary safety measure:

It is recommended to use only karabiners whose fatigue resistance has been verified.

Munich, February 2005

Dipl. Ing. Thomas Finsterwalder
Managing director Finsterwalder GmbH

Finsterwalder GmbH, Pagodenburgstr.8, 81247 München, Tel. ++49 (0)89 811 65 28,
Web www.finsterwalder-charly.de .

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最后：
在疲劳测试中，新的钢质金属钩在不锁闭的情况下需要大约2百万次低强度拉力会断，新的铝质钩需要大约500万次才被拉断。
但是，木有人知道时间、气候、温度和其他因素（外力、上树、上电线）对金属疲劳的作用。