You may have read a DHV notice about problems with Aramid / Kevlar. Here some explanations:

The Problem: Some gliders have experienced line failures in the upper cascades in flight.

Good news: The fact that your glider manufacturer is listed under this safety notice does not mean your glider necessarily has a line problem. Most gliders are fine!

Bad news: Just because your glider / manufacturer was not listed under this warning does not neccessarily mean your lines are not affected. It could simply mean that the manufacturer of your glider did not want to be named in connection with this notice, but you still have the affected line material on your glider. All gliders using Aramid / Kevlar lines may be affected, regardless of manufaturer or model.

Background: In Germany and Austria, it is compulsory to send all gliders back to the manufacturer or to licensed testing companies after 200 hrs or 2 years, or as specified by the manufacturer (e.g. Acro, school or commercial tandem wings should be tested more frequently). These 1 or 2 year checks include e.g. a full line length check, porosity check, material strength test and line strength check. Usually several lines are broken, the breaking strength is recorded and the lines are replaced. Should the lines not show the required breaking strength or cloth quality, more lines may be replaced or no check certificate may be issued. This means that the glider loses his airworthiness certificate for Germany and Austria and may not be flown any more in this countries.

So far, it has been assumed that Kevlar / Aramid lines weaken due to kinking / bending while in use. Hence, the main lines (bottom cascade) seemed to be most affected as they are handled more during packing, launching etc. Also, when manufacturers calculate the min breaking strength of a line, the sum of the breaking strength all lines in any one cascade is higher than the breaking strength of the next lower single cascade line. That means the lowest line should be the weakest point. As a result, usually only the bottom lines were breake tested.

After some instances of upper cascade lines breaking, it was found that these lines may weaken with use as much as the main lines. The weakening of the lines seems to be not only due not to kinking / bending of the lines, but also the movement when loading and un-loading the line in flight. This effects all cascades.

The DHV safety notice simply reminds manufacturers and more importantly the independent checking companies, to check top cascade lines as well as the main lines, to make sure weaknesses in those are detected in future.

Text copied from Wings & Waves New Zealand, Eva Keim