Following up from the article A Better Way to Measure Porosity in the last issue, I wanted to explain more about glider inspection and porosity.
During every paraglider inspection various parameters are checked – it’s like getting an annual check on a car. In addition to the general condition and trim, the porosity measurement of the fabric plays a crucial role. This measurement indicates how air-permeable the material is.
A paraglider canopy should allow only a limited amount of air to pass through, as this has an impact on its flight characteristics. Therefore, this simple test often determines right at the beginning of the inspection whether a paraglider will proceed to further checks or be classified as no longer airworthy.
Until recently the following benchmarks applied to air permeability: values below 15 seconds were considered overused and no longer airworthy; while permeability between 15 and 40 seconds was seen as heavily used. Anything above 300 seconds was considered as good as new. However,...
