Check the comparison boundary

A storm interval may have higher speed or turbulence than a dry comparison, so the difference cannot automatically be assigned to water. Use the same measurement location and valid sensor configuration where possible. Note whether the effect begins during rain or appears later, because delayed behaviour may raise a different retention question. Missing or low-resolution records can prevent a confident statement about the sequence.

Connect the trend with condition evidence

A recurring drainage change, visible deposits or an altered blade surface may help narrow the investigation. Retained water and changed aerodynamics can coexist, and neither can be quantified from stain length alone. SKF diagnostic methods support examining the response pattern, while blade inspection evidence addresses physical condition. A spectrum can identify relationships but cannot prove where water is located or whether the blade structure is sound.

A response beginning well after rain ends can justify a different retention hypothesis from an immediate wet-surface change. The delay must be supported by sufficiently resolved records, because coarse averaging can make a prompt response appear later than it actually occurred.

Choose a discriminating assessment

Ask what approved examination can distinguish a wet-surface effect from retention, damage or an unrelated operating change. Do not drill a drain, add a balance weight or apply a coating to remove the symptom without a supported cause. No MARSTON rain-vibration characteristic or allowable wet operating response is established here. The actual equipment instructions and qualified findings must define any restriction, correction or release.