Porosity in Paragliders: What it is, how I check it, and why it matters for safe flight

If you fly paragliders like I do, porosity is one of those topics that creeps up as the wing ages. It’s all about how the fabric breathes and how that breathing affects inflation, stability, and overall performance. Here’s my practical take on porosity, how I test it (with a porosimeter), why it matters for safety and maintenance, and how 406 Paragliding in Belgrade, MT can help you keep your wing in top shape.

What is porosity (on a paraglider)

Porosity is the fabric’s air permeability—the rate at which air can pass through the canopy under a defined pressure. We want to know how much air can pass through our wing’s fabric from the inside going out. The fabric when manufactured is coated to reduce its porosity and make it more airtight.

Over time, UV exposure, heat, humidity, and wear change the porosity, so regular checks are smart.

According to Gin Gliders INC. who states in their “Airworthiness inspection instructions for Gin paragliders” the following interpretation of porosity readings.

Using a Hello Porozit Porosimeter that reads the following:

• Greater then 200, the paraglider is considered as new.
• 100-200, Good condition.
• 100-150, Considerably used.
• 50-100, Heavily used.
• Less than 50, the paraglider is overstressed and is no longer airworthy.

 Why porosity matters:

Low porosity readings are an indicator of an aged wing. Aged wings can be badly deformed from their originally designed profile causing poor or dangerous performance.

Since we can’t measure or inspect the “shape of the wing”, porosity must be used as an indicator.

A paraglider that has become significantly more porous will begin to exhibit undesirable behavior that often is incorrectly attributed to being out of trim.

In addition to reduced performance the aged wing’s fabric is becoming weaker and less able to hold its shape.

When buying a used wing, porosity test results can provide some insight into the condition of the paraglider.

According to the Paraglider Manufacturer’s Association (PMA). Visual inspections, line strengths and geometry, fabric tear strength tests along with fabric porosity tests are part of the PMA Standards of “Periodical inspection of paragliders”

How I check porosity (and where a porosimeter fits in)

Porosity is measured using a well-calibrated porosimeter. On the upper surface of the paraglider, four or more clean and undamaged sections, located 20-30 cm behind the leading edge, are tested individually with the porosimeter to measure airflow at each spot. The airflow direction must be from the inside of the wing to the outside.

The results are averaged to determine the flow rate through the fabric per unit area (e.g., liters per square meter per second under set pressure). A higher number indicates better porosity.

Because comparing different types of fabrics can be challenging, it is advised not to include porosity values in the final report. Instead of numerical values, PMA (In their Periodical inspection of paragliders, V. 2024.12.1) suggests categorizing porosity as one of the following: Fail, Acceptable, or Good.

Why this method matters:

Measuring porosity provides an objective and consistent way to understand how the fabric interacts with air. Regular porosity testing helps identify changes early, preventing them from turning into handling issues during flights.

 

Why paraglider porosity matters for safe flight and maintenance

•  Safe flight: Proper porosity keeps your inflations predictable and internal pressure stable.
•  A worn-out porous wing can lead to:
•  Poor or irregular inflation.
• Reduced lift
• longer brake travel required for control.
• Changes in stall behavior or handling that surprise you.
• Porosity changes with aging, UV exposure, abrasion, and use.
• Porosity is one measurement to determine if the paraglider is still airworthy.

 

Maintenance tips to keep porosity in check

Schedule a paraglider porosity test on your wing annually as part of its regular maintenance.

Inspect the seams, patches, and fabric for pinholes, tears and scuffs. Minimize dragging your wing on the ground.

Store and handle your wing properly to minimize UV, moisture and heat damage.

406 Paragliding: your complete shop in Belgrade, MT

I’m lucky to work with 406 Paragliding in Belgrade, MT, where we’ve got a full shop outfitted for paraglider maintenance and inspections. We offer:

•  Professional porosimeter-based porosity testing to verify fabric performance against factory specs.
•  Comprehensive canopy inspections, and panel repairs by trained technicians.
•  Laser trimming, paraglider line replacement and testing.
•  A full range of maintenance services and inspection protocols to keep your wing safe and performing as designed.
• OUR MAINTENANCE WEBPAGE

 

If you’re in the 406 area and want to keep your paraglider in peak, safe condition:

•  Consider a porosity check as part of your annual or post-repair maintenance.
• Ask about a comprehensive canopy inspection that includes porosity testing.
• Reach out to 406 Paragliding in Belgrade, MT to book an inspection or maintenance session. We’re equipped to handle everything from basic checks to full canopy overhauls.