ASTM E426 and Eddy Current on Composite Blade Repair

What the standard covers

The practice covers electromagnetic examination of tubular and conductive products, and a blade programme applies it where a conductive element is present. Lightning protection hardware, down conductor paths and repair fittings fall in scope, and the field platform carries eddy current as one of several payloads for exactly that reason.

What it demands

• Application to the conductive elements rather than to the non-conductive laminate
• Examination of lightning protection and repair hardware where present
• A payload interchangeable with the ultrasonic channels on one platform
• A record that sits alongside the volumetric data for the same blade serial

How it lands on a blade scan

The method is a specialist instrument rather than a general one, and that shapes how it is deployed. A field crawler carries PAUT, eddy current and thermography payloads on one interface with tool-free swaps in under 30 seconds, so eddy current can be brought to a conductive element without a second platform. The value is the record it adds, because a blade carries lightning protection hardware and repair fittings, and examining those on the same pass keeps one dataset per serial rather than several. The multi-brand platform holds Eddyfi, Zetec, Olympus and Dolphitech probe families, so the probe choice follows the element rather than the platform.

How to apply it to a blade

Run these checks in order. By Step 5 the scan plan has the threshold, the geometry and the record it needs.

1. Fix the acceptance threshold. Start from the threshold the zone carries, not from the method you happen to own. IEC 61400-5 Section 11 asks for volumetric detection of indications 6 mm and larger in the laminate plane, and DNV-ST-0126 tightens the leading edge to 3 mm, so the threshold is set before the probe is chosen.
2. Read the geometry off the drawing. Measure the thickness and the curvature the probe has to travel. A spar cap up to 80 mm of unidirectional laminate and a root transition of changing radius are two different scan problems, and the radius decides how the array is coupled.
3. Choose the modality pair. Pick modules by defect geometry, not by habit. PAUT images planar separations that lie parallel to the plies, TOFD catches volumetric clusters whatever their orientation, and running both on a 256-channel system puts the two mechanisms in one pass.
4. Automate the scan path. Put the probe on an encoder-driven carriage and let the path, not the technician, set coverage. A 600 mm spar cap falls to one longitudinal pass at 500 mm/s on a linear array, where a single-element probe needs 20 parallel passes and runs about five times longer.
5. Lock the evidence chain. Write the coverage map, the daily calibration and the indication log to the blade serial while the scan is running. It is the difference between a 3-day type-certification audit and a 3-hour document review, and it is what ISO 9712 qualification is there to sign.

Nothing here is rounded up for effect. Each value is the one on the equipment sheet or in the field report behind it.