DNV-ST-0376: Rotor Blade Certification and Testing

What the standard covers

The standard addresses the rotor blade over its qualification path, so the NDT content shows up around full-scale testing and the examination stages that support it. A programme reporting to it scans prototype blades before and after static and fatigue testing, then carries the same methods into series production and service.

What it demands

• Blade examination against the standard at the qualification stages, including full-scale testing
• NDT before and after testing so the before and after states can be compared
• Methods aligned with the manufacturing and in-service clauses so one method serves the whole path
• Certification evidence that a notified body can review against the standard

How it lands on a blade scan

The value of the standard for a blade programme is continuity. IEC 61400-5 Section 12 covers full-scale testing with NDT before and after, and DNV-ST-0376 frames the same blade over its qualification. When the factory scans at 500 mm/s and the in-service crawler tracks the curve at 300 mm/s with the same volumetric methods, a blade carries one evidence chain from prototype through production and into service. That continuity is what a certification audit is actually checking. A 3-day audit that becomes a 3-hour document review is the result of the chain being intact rather than of the audit being lenient.

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.

The numbers below are drawn from the equipment records and field campaigns this site already publishes, not from a generic catalogue.