Post-Repair Verification: Proving the Repair, Not the Blade

What this stage covers

The scope is the repaired zone plus the interface band around it, not the whole blade. A rebuilt bond line and a re-laminated shell section present the same planar separation risk that a volumetric pass exists to size. Covering the repair alone leaves the parent-to-repair boundary on trust, and that boundary is where the next indication tends to appear.

What the inspection includes

• A volumetric pass over the repaired zone and the interface band around it, so the parent-to-repair boundary is covered rather than assumed
• Acceptance drawn from the same table as the original scan, so the repair is not judged more leniently than the structure it replaces
• TOFD alongside PAUT on a rebuilt bond line, because fillet depth is what confirms the repair was made to the drawing
• The evidence chain rewritten against the blade serial, so the repair scan sits on the same record as the campaign that found the defect
• A repeat pass at the next scheduled interval, because a repair that holds on day one still has to hold through the fatigue cycles the blade was designed for

Where the value sits

The value is comparability. A repair accepted on a different basis from the original scan leaves two sets of records that cannot be read against each other, and the next campaign inherits that problem. Hold the repaired zone to the Table G.1 limit, size each indication in any direction, and index the result to the blade serial at plus or minus 0.1 mm, so the repair scan and the defect scan describe the same coordinates on the same model.

How to plan this stage

Run these checks in order. By Step 5 the scan, the threshold and the record are aligned to the stage.

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.

Read the figures as sourced, not as marketing. Each one sits in the documentation we already publish on this site.