Paraglider Fabric Porosity & Line Length Annual Inspection

ContextPorosity is rarely uniform across a canopy. The leading edge absorbs the most UV radiation and mechanical stress from inflation cycles and ground handling, so it typically degrades fastest. A reading of 0 to 30 l/m2/s is considered excellent for a modern glider. Readings between 30 and 100 l/m2/s are generally acceptable but always check your manufacturer's specific limit — some specify 50 l/m2/s as the maximum before remedial action is required. Readings above 200 l/m2/s typically indicate a wing losing cell pressure during flight. Record every individual reading with cell number and position in the log table.

ContextTechnique materially affects results. Hold the meter flush against the fabric with steady hand pressure — rocking or angling the device breaks the seal and produces artificially low readings that make degraded fabric appear healthier than it is. Take three readings at each location and log the average. Wind significantly affects open-air testing; always test in a sheltered environment if possible. A closed hangar or garage consistently produces more repeatable results than a hilltop in any breeze.

ContextThe bottom skin near wingtips and the first two cells either side of center absorbs significant abrasion from slope and field landings. This surface is frequently skipped in pilot self-inspections because it requires flipping sections of the canopy and is less visually obvious. Test the lower surface at the trailing edge specifically, as this area experiences both fabric flex fatigue from repeated brake inputs and UV exposure during typical laid-out ground time. Neglecting the bottom skin means you may miss the fastest-degrading zone on an active cross-country wing.

ContextHold a powerful LED torch or panel inside or behind each cell while viewing from the opposite side. Pinholes show as sharp bright points; thin spots glow more intensely than surrounding fabric. Even if a pinhole zone passes the porosity meter test because the test aperture does not center on the hole, a cluster of pinholes in a single panel section can cause local cell pressure loss under high G loading. Mark every suspicious area with a fabric-safe pen and include a sketch or photo reference in the log.

ContextHot-melt adhesive tape and sewn seams separate with age and UV exposure. Run your finger along every leading edge seam — it should feel firmly bonded with no lifted edges. Any delamination wider than 5 mm or longer than 10 cm must be flagged for bonding repair before the next flight. On canopies older than five years, pay particular attention to the attachment points where internal diagonal ribs meet the top skin — these joints carry high aerodynamic loads and can develop micro-tears that are invisible from outside but detectable when you look at the rib junction from inside the cell with a torch.

ContextA patch that is lifting at its edges creates a localized venturi effect — airflow channels under the raised edge and dramatically elevates local porosity even if the patch itself remains intact. Position the porosity meter 1 to 2 cm outside the patch boundary rather than on the patch itself. If the area surrounding an old patch reads significantly higher than comparable areas without prior repair history, the patch may be masking wider degradation. Flag the area for professional re-evaluation and note the patch location and approximate age in the log if known.

ContextThis step is physically demanding but irreplaceable. Remove footwear, use a headlamp, and carefully work your way into each cell from the nose opening. Internal diagonal ribs shape the aerofoil profile; a torn rib causes localized cell collapse and deformation that affects glide performance and stability in turbulence. A small tear under 3 cm in a non-load-bearing position may be patch-repairable by a rigger, but any rib that has fully detached from either the top or bottom skin is a grounding finding that must be resolved in a workshop before the next flight.

ContextLeading edge battens are thin plastic rods or sheet inserts sewn into pockets along the nose that maintain the aerofoil profile during inflation. Run your hand along the interior nose from cell to cell to feel for broken pieces, gaps where a batten has slid out of position, or pockets that are empty. A cracked batten may remain in place initially but can fracture under the dynamic loads of inflation and puncture the fabric from inside — creating damage that looks from the outside like an impact tear with no obvious cause. Replacement battens are generally available from the manufacturer and the repair is straightforward when caught early.

ContextUV degradation in paraglider nylon and polyester progresses from color fading, to surface texture changes (a chalky or rough feel), to structural weakening of the polymer chains. Compare color uniformity across the entire top surface — areas noticeably lighter than surrounding panels have received more cumulative UV dose. This is most common on the top-rear panels and wingtips. A bleached zone may currently pass a porosity test but represents an accelerated degradation trajectory. Record the location and approximate area of any bleached zones as priority re-test points for the next inspection.

ContextLine length measurements are only meaningful under tension. Modern paraglider lines — Dyneema, Aramid, Vectran — have minimal stretch but will sag under their own weight if slack, introducing measurement error. A standardized load of approximately 5 kg per line is the workshop standard, but a firm, consistent hand-tension that removes all sag is acceptable for a field check. Measure from the sail attachment loop to the maillon at the riser, not from any intermediate junction. Use the same anchor point and reference method for every line on the same riser to keep comparisons consistent.

ContextA-lines are the frontmost row, attached to the leading edge, and are the primary determinants of the wing's pitch attitude and angle of attack. They are typically the shortest lines and the most safety-critical in terms of trim. The typical tolerance is plus or minus 15 mm from the manufacturer's nominal, but high-performance EN-C and EN-D wings often specify plus or minus 10 mm — check your specific model. Lines shorter than nominal pull the leading edge down, reducing stall margin. Lines longer than nominal do the opposite. Asymmetric discrepancies between left and right A-lines cause the glider to consistently turn or surge toward the shorter side.

ContextB-lines support the mid-chord section and serve as the control connection for the B-line stall emergency maneuver. Individual line variation within a riser group — rather than a riser average — is what matters for detecting spanwise twist. A riser average can look perfectly within tolerance while individual lines within it span 30 mm, causing localized deformation of the aerofoil profile. Line shortening in Dyneema B-lines is more common than elongation and typically affects pitch stability first, making the wing feel unusually prone to surging in thermal cores before it shows up as an obvious handling issue.

ContextC-lines connect to the C-riser, which also serves as the speed system attachment point on most gliders. Shortened C-lines reduce camber and lower the trailing edge angle, affecting performance subtly before it becomes obvious. If the wing has been deliberately tuned away from factory trim — for example, by a previous owner seeking a different speed or pitch behavior — that modification must be documented here with the reason, date, and who made the change. Undocumented modifications from factory spec are a significant finding in any inspection.

ContextNot all wings have D-risers — many EN-A and EN-B beginner wings use a three-riser layout, while EN-C and EN-D performance wings typically have four. If D-lines are present, they support the trailing edge and stabilizer panels and are subject to significant fatigue from the vibration transmitted through brake input. On reflex-profile speed gliders and EN-D wings equipped with trimmers, D-line measurement is especially critical because changes in D-line length interact directly with the trimmer range and can shift the effective stall angle at full speed.

ContextBrake lines are typically made from softer, more abrasion-resistant material than the main structural lines and wear faster. They are also the most commonly field-replaced lines, which means the left and right brake lines may come from different batches with different elongation histories. Measure both independently and note any asymmetry. A brake line longer than specified requires greater pilot input to achieve the same trailing edge deflection. A brake line shorter than specified induces premature trailing edge deflection, which is a stall-characteristic concern in thermic or turbulent conditions.

ContextSpeed bar lines are frequently made from a different material than the main lines and may have their own separate maintenance specification in the wing's manual — they often do not appear on the primary trim chart. Check the maintenance section specifically for speed system tolerances. While measuring, press the speed bar by hand and watch every pulley in the system: each should rotate freely. A pulley that does not spin creates a hard wear point on the accelerator line at that contact location. Seized pulleys are a common finding that is almost never caught in casual pre-flight checks because pilots rarely examine riser-mounted pulleys in detail.

ContextHold the line between thumbs and forefingers approximately 10 cm apart and twist the outer sheath in one direction while restraining the core end. In a healthy line, the sheath and core are bonded together and the sheath will rotate only minimally. If the sheath spins freely — rotating several times while the core stays stationary — or if the sheath bunches while the core remains straight, the internal core fibers have been severed. This damage is completely invisible from the outside and can result from a hard tree landing, rock impact, or even a ground collision that seemed minor at the time. Any line that fails this test must be replaced before the next flight, regardless of appearance.

ContextAramid (Kevlar-type) lines are particularly vulnerable to UV degradation and can become critically brittle long before their measured tensile strength shows a meaningful decline in a simple pull test. Run your fingernail lightly along the sheath: a fine surface fuzz or pilling indicates UV damage to the outer fibers. Then gently bend a section of each line in a small loop — a healthy line flexes readily. A line that resists bending, feels stiff or crunchy instead of supple, or produces a faint crackling sensation is overdue for retirement regardless of its measured length. UV-degraded lines can retain as little as 50 to 70 percent of their nominal breaking strength with no visible external indicator of weakness.

ContextMaillons at the sail end should be screwed to hand-tight and then given an additional quarter turn. The gate must be fully closed — if you can insert a fingernail between the gate and the maillon body, it is not properly secured. Inspect all aluminum maillons for white powdery deposit (aluminum oxide), which signals moisture ingress; any maillon showing surface pitting should be replaced. Each maillon should also rotate freely on the line attachment loop. A seized maillon transmits torsion loads directly to the terminal splice of the line, accelerating fatigue at the attachment point over many flight cycles.

ContextAt the canopy, line loads transfer through a reinforced fabric tab sewn into the top skin. Every stitch on these tabs must be intact — broken threads or fraying at the tab edge indicates fatigue. On older canopies, check specifically whether the tab has migrated sideways within its pocket: it should sit centered in its reinforcement patch. A laterally migrated tab concentrates load on one side of the reinforcement rather than distributing it evenly across the stitching, and is one of the most commonly missed findings on high-hour canopies because it is only visible when the wing is fully flat-laid with adequate lighting.

ContextRiser webbing — typically Dyneema or polyester flat braid — can absorb severe damage that is invisible at a casual glance. Inspect specifically at fold points: where the riser passes over a pulley or through a buckle. These are the locations where fatigue cracking and abrasion concentrate under cyclic loading. A cut that exposes inner fibers means the riser must be replaced immediately — there is no field repair for cut riser webbing. Chemical staining from fuels, solvents, agricultural sprays, or unknown liquids can reduce webbing tensile strength by 40 to 70 percent depending on the substance and exposure duration, with little to no change in external appearance. Any stain of unknown origin should be treated as suspect and the riser retired from service.

ContextSpeed system pulleys are load-bearing components whose failure can cause abrupt, asymmetric application of the speed system in flight. Spin each pulley between thumb and forefinger: it should rotate smoothly with only light resistance. A gritty or stiff pulley can be cleaned with isopropyl alcohol and retested; if stiffness persists after cleaning, replace the pulley before the next flight. Inspect the plastic or alloy pulley body for cracks, focusing around the axle pin hole where stress concentrates. On pulleys retained by a split pin, confirm the pin is present, fully inserted, and not bent open.

ContextOn risers that use HMS-style or oval connectors instead of maillons, the locking mechanism (screw sleeve or twist-lock) must be in the engaged locked position, not just snapped shut on the gate. A gate that is closed but unlocked can open under vibration, contact with the harness frame, or debris on the riser. While performing this check, also inspect the body of each connector for deep grooves from hardware-on-hardware contact during previous flights — surface gouges can propagate into structural cracks under cyclic loading and should be treated as cause for replacement regardless of their current depth.

ContextBrake toggles absorb direct hand loads on every flight and receive UV exposure whenever the wing is spread on the ground. The webbing loop attaching the toggle to the brake line must be free of cuts and fraying along its full length. The stitching at the loop-to-toggle junction is a high-stress point — pull firmly on each toggle in the direction of normal use and watch for any movement of the stitching or listen for any creaking that suggests fatigue. Some pilots replace brake toggles every one to two seasons as a low-cost precaution; the component cost is minimal, and toggle failure during a recovery maneuver in turbulence carries disproportionate consequences.

ContextA structured table — not narrative notes — is essential for this data. The purpose of consistent formatting is to enable year-on-year trend comparison: a cell reading 45 l/m2/s this year that read 20 l/m2/s last year is technically passing but degrading at twice the expected rate. That trend should inform whether you shorten the next inspection interval to six months instead of twelve. Keep a digital copy of every completed log in addition to any physical record stored with the wing.

ContextUse millimeters throughout — not centimeters. The precision matters at the tolerance boundary, where a 5 mm difference can be the difference between a pass and a flag. Note the measurement method and load condition in the table header (for example, '5 kg rig tension, fiberglass tape'). For any line within 5 mm of the manufacturer's tolerance boundary, add a monitor note and schedule a mid-year re-measurement rather than waiting for the next full annual. Record the inspector's name and date on every table.

ContextThe four categories are: Airworthy — all items pass with no concerns; Airworthy with Conditions — minor findings exist such as one line near the tolerance limit, which must be re-checked before the next annual but do not require grounding today; Requires Repair Before Flight — specific identified items must be corrected by a certified rigger before the next flight, and the wing should be bagged and tagged with a note; and Grounded — a critical finding such as a torn structural rib, porosity failure across multiple cells, or severely out-of-tolerance lines renders the wing unsafe until workshop repair is completed and a re-inspection performed.

ContextEven when the pilot and inspector are the same person, create this document. In the event of an incident investigation, an undocumented inspection provides no legal or insurance protection. The summary should reference the log table data directly, name each finding by cell or line identifier, and specify whether the repair can be performed in the field or requires a certified workshop. Give a specific calendar date for the next inspection — not 'annually' but a precise month and year. Sign and date the summary and attach it to the log.

ContextA paper log stored loosely in a wing bag can be destroyed by moisture, abrasion, or a rough retrieval after an incident — precisely the moment when the documentation would matter most. A waterproof zip-lock sleeve inside the bag is the minimum protection. For digital backup, a dated PDF in a dedicated cloud folder labeled by wing serial number and year is best practice. Photographing the completed log with your phone immediately after signing takes under ten seconds and creates a redundant copy automatically timestamped by your device.