Inspect IQ

Wind Turbine Drone Inspection: Finding Blade Damage and Planning Repairs

By Kush Agarwal, President and CEO, YelloSKYE. Published 2026-10-19.

Executive Summary

• The Question: How are wind turbine blades inspected by drone, what damage does it find, and how do the findings become a repair programme?
• The Answer: With the rotor stopped, a drone flies along every side of each blade and records erosion, lightning damage, cracks and coating faults with their exact position on the span. The record lets owners grade damage, watch it grow between inspections and send rope or platform teams only to the blades that need work.
• The YelloSKYE Angle: Inspect IQ runs high-resolution sweeps of turbine blades to detect lightning strikes, leading-edge erosion and fine fractures, and keeps every located finding in the DEX platform for comparison and repair planning.

A wind turbine drone inspection is a close visual survey of a turbine's blades, and often its tower and nacelle, carried out by a drone flying a set path around the stopped rotor. It records surface damage such as leading-edge erosion, lightning strikes and cracking along the full length of every blade, and ties each finding to the blade and its distance from the root. The turbine is back generating soon after the drone lands.

For owners, asset managers and maintenance contractors, the drone answers the first question in any blade programme: which blades are damaged, where, and how badly. YelloSKYE's Inspect IQ carries out rapid high-resolution blade sweeps for exactly that purpose. This guide covers the defects that matter, how an inspection is flown, how onshore and offshore work differ, and how a set of findings becomes a repair plan.

Why blades get most of the attention

A modern blade is a long composite shell, usually glass or carbon fibre in resin, built in two halves and bonded together along its leading and trailing edges. It spins through rain, hail, dust and insects at high tip speed for years at a time, and it is the tallest point in the landscape when a storm passes over. Blades are also expensive to replace and slow to source, so finding damage while it is still small and repairable is where most of the value lies.

Blade damage also tends to progress. A rough patch of coating lets water and grit work into the laminate; a small crack grows with every load cycle. Regular inspection is how owners catch damage at the stage where a repair team can fix it in a few hours on a rope, instead of later when a blade has to come down.

Defects a drone inspection finds

The table lists the common external findings, how they look in close imagery and why they matter.

On the asset inspection page, Inspect IQ's blade diagnostics are described as detecting lightning strikes, leading-edge erosion and micro-fractures. YelloSKYE's AI models flag likely defects across the image set and categorise each one, which shortens the search through the large number of frames a single turbine produces. A blade engineer then reviews and grades what has been flagged.

The same flight usually covers the rest of the exterior as well: oil running down the tower, coating breakdown and corrosion, damage to the nacelle cover, and on offshore units the transition piece and access platform.

How a blade inspection is flown

Preparing the turbine

The operator stops the turbine, locks the rotor and yaws the nacelle to suit the wind and the light. The rotor is usually parked with one blade pointing straight down, which gives the drone a clean line along that blade and a predictable layout for the other two. Blades may be pitched so that the face being photographed is turned towards the camera.

The flight path

Each blade has four faces to cover: the pressure side, the suction side, the leading edge and the trailing edge. The drone flies along the span at a fixed distance, root to tip and back, capturing overlapping images so nothing is missed. Many inspection systems now follow the blade automatically, using onboard sensors to hold a steady stand-off along its length, which gives consistent images from one inspection to the next. YelloSKYE flies pre-programmed paths wherever the asset allows for the same reason: repeat flights produce comparable views.

Tagging every image

An image of a white composite surface means nothing unless you know where it was taken. Each frame is tagged to the turbine, the blade (often by its position on the hub or its serial number), the face and the distance from the root. That reference is what lets a rope team arrive at the right spot.

Conditions

Turbines are built where it is windy, so the inspection window is set by the drone's wind limits as well as the operator's wish to stop the turbine when generation is low. Bright sun gives sharp detail but can cause glare on glossy coatings, so pilots adjust angles to keep reflections off the surface they are recording. Rain, low cloud and ice all stop the work.

Thermal capture

Thermal imaging can sometimes reveal damage beneath the surface, such as delamination or a failing bond line, because those areas heat or cool differently as the sun moves across the blade. Results depend heavily on conditions and on the blade construction, so thermal blade findings are treated as leads that need confirming. Our guide to drone thermal inspection explains when thermal data can be trusted.

Onshore and offshore inspections

The inspection method is the same at sea; almost everything around it changes.

Because hands-on access is so much harder offshore, a thorough drone record carries more weight there. A repair campaign planned from good images can group work by location and severity, so a vessel and its rope teams spend their limited weather windows on the blades that most need them.

From findings to a repair plan

An inspection is only as useful as the decisions it supports. The steps below turn a set of images into a programme of work.

Grade every finding

Most owners grade blade damage on a numbered scale. The definitions belong to the owner, manufacturer or insurer, but they usually look something like this:

Locate and measure

Each finding needs its turbine, blade, face, distance from the root and approximate size. That is what a repair contractor prices and plans against.

Track change between inspections

The same erosion patch seen on two dates tells you how fast it is growing, which is the best guide to when it needs fixing. In the DEX platform, YelloSKYE places each finding on the captured asset, lets reviewers slide between capture dates to see when damage first appeared, and provides dashboards of open issues, severity and resolution across a whole portfolio.

Group the work

Repairs are planned by site, by weather season and by access method. Grouping several grade 3 repairs on the same turbines into one rope-access visit is usually cheaper than chasing each one separately. YelloSKYE exports findings as a defect database, with marked-up images, GPS position, severity rating and a recommended remedy for each entry, in PDF, Excel or BIM-linked formats, which makes it easier to hand a scoped package to a repair contractor.

Close the loop

Mark a repair as complete only when a later image, from the repair team or the next drone flight, shows the fixed condition. A blade history built this way also supports warranty claims, insurance discussions and end-of-warranty inspections.

The pattern is the one YelloSKYE describes in its solar farm thermal inspection work: every defect mapped to its exact position so maintenance crews know exactly where to go, instead of searching on the ground. On a wind farm, the search happens at height, which makes a precise location even more valuable.

What a drone blade inspection cannot tell you

• It sees the outside only. Damage to the spar, shear webs or internal bond lines appears in images only once it reaches the surface. Internal inspections use crawlers or cameras inside the blade.
• It cannot test the lightning protection system. Burn marks show a strike; whether the down conductor still works needs an electrical continuity test by a technician.
• It cannot measure depth. An image shows how wide erosion is, not how far into the laminate it goes. A repair technician confirms that by hand.
• It needs the turbine stopped. Inspection time is lost generation, so plan for low-wind periods.
• It depends on image quality. Dirt, insect build-up and glare can hide or imitate damage, and a poor image set is worse than a short delay for better conditions.

None of these limits is a reason to skip the drone. They are reasons to treat the drone record as the first stage, with targeted hands-on work following it. The same order of work applies on buildings, as the facade inspection from a desk use case describes, and on bridges, covered in our guide to drone bridge inspection.

Blade inspection checklist

1. Decide the purpose: routine condition check, post-lightning check, end-of-warranty review or pre-purchase due diligence.
2. Agree the grading scale with the owner, manufacturer or insurer before the first flight.
3. Confirm the blade identification scheme so every image can be tagged correctly.
4. Arrange stop, rotor lock and yaw position with the turbine operator, and pick a low-wind window.
5. Obtain flight approval from your national aviation authority (such as the FAA for American sites, or the CAA and GCAA for British and Emirati ones) plus any site or marine permissions.
6. Cover all four faces of every blade, plus tower and nacelle if in scope.
7. Grade, locate and measure each finding, and compare with the previous inspection.
8. Group repairs by site, severity and access method, and book rope or platform teams only where needed.
9. Record each repair and keep the same flight plan for the next cycle.

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