Drone inspections are making jobs easier, safer, more affordable and often provide a better result than inspections conducted by airplane or people working at heights but this can come at a cost if these common mistakes are made.
Drone Inspection Mistake 1:
Undertaking a drone inspection without certification
Do you need a license to do a drone inspection?
Yes, the Federal Aviation Administration (FAA) states that you need to follow the Part 107 guidelines if flying a drone for work which includes becoming a FAA certified drone pilot. This involves studying drone flying rules and passing a knowledge test.
Your drone will also need to be registered with the FAA if above 250g, with this license you can fly drones up to 55 pounds (24.9kg),
You might be wondering if you need to be certified if you are conducting a drone inspection and not being paid. The answer is YES, the FAA clearly states that the exemption for recreational drone flying is not a matter of if you are being paid. Flying drones for roof inspections, real estate photography or events is non-recreational and therefor the drone pilot will need to follow to Part 107 guidelines and become a certified drone pilot.
There are hefty fines if you’re reported to the FAA for flying a drone for non-recreational use with out certification, it’s not worth the risk!
Drone Inspection Mistake 2:
Using the wrong drone camera
The most common types of camera used in drone inspections are thermal and CMOS lense (standard photographic camera) but using a drone camera that doesn’t have high enough resolution will fail to pick up defects. This is a common mistake made by beginner drone inspectors undertaking roof inspections.
Drone Roof Inspections
Drone pilots undertaking roof inspections are required to report the type of roof and any indications of roof leaks which can include looking at the ceiling from inside the property.
Looking for these details requires a drone camera with an appropriate resolution so images can be zoomed into later. 4k Photography is becoming common in UAVs
and this is going to be more than enough for drone roof inspections.
Close up shots are taken to check the integrity of screws and fixings to see
if they have indications of rust or inspect joints that are no longer flush.
The guidelines for home inspection set out by the InterNACHI Home Inspections Standards of Practice the review the roof should include:
- The roof covering material
- Gutters
- Downspouts
- Vents
- Flashing
- Skylights
- Chimney
- Roof penetrations and general structure
The inspector is not required to predict the expected life of the roof but needs to be able to accurately identify defects in the roof covering such as functional damage that can potentially allow water to pass through, heat blistering of shingles and obstructions that prevent the shedding of water runoff.
Inspecting house roofs for damage can potentially be a risky task but where drone roof inspections really change the game is viewing multi-story building roofs and highly sloped or domed roofs. It’s not a requirement to physically walk on the roof or do anything that is unsafe or that can potentially cause damage.
The images in any drone inspection work need to be steady to give good clear photos so a 3 axial gimbal is a must have.
Drone Inspection Mistake 3:
Not preparing the area and infrastructure (Risk Assessment)
A costly mistake when undertaking a drone inspection is failing to check for obstacles, putting your drone and the infrastructure being inspected at risk.
One of the most costly and high risk scenarios is wind turbine drone inspection but even roof and solar inspection require a risk assesment.
Wind Turbine Drone Inspection
Wind turbines require yearly inspection as a minimum to check for damage and wear. The blades need to be manually stopped before the drone inspection begins but flying near wind turbines is still high risk to the drone as they can flex a lot in the wind. If they collide, the wind turbine blades can cause major damage to the drone and the repair of rotor blades is extremely expensive, labor intensive and time consuming.
Ideally the turbine is manually rotated to face the sun so that the light is coming from behind the drone for most of the photos.
During the wind turbine drone inspection the drone can be manually controlled or follow set waypoints to take the exact same photos for the inspection of each wind turbine in a wind farm.
These are the defects the UAV pilot is looking for during the wind turbine drone inspection:
- Damaged coatings
- Erosion cracks
- De-lamination
- Dents
- Holes in the exterior layers
Each portion of the wind turbine is inspected to check for damage from weather and general wear and tear including the rotor blades, foundations, tower and spinner.
Above: Wind turbines are 100-150m tall so inspection by drone is far safer than physical inspection. Image credit: VisualWorking
Drone Inspection Mistake 4:
Flying at the wrong time of day
The time of day that a drone inspection is conducted is very important for solar panel inspections when looking for defects with a thermal camera drone.
Drone Solar Panel Inspection
IEC standards require a minimum solar radiance of 600W/m2 (amount of light energy). IEC are the International Standard for all electrical, electronic and related technologies.
If the drone solar panel inspection is conducted in the early morning or evening there isn’t going to be enough solar radiance to pick up anomalies in the panels. The solar radiance needs to be checked with a solar irradiance meter before beginning the inspection and at set intervals as the levels can drop due to cloud cover.
The solar panels need to be fully exposed, any leaf litter build up or snow cover needs to be removed.
For solar panel farms, a flight path is programmed to automatically fly the drone at a set altitude in equally spaced parallel lines covering the area. The lower the altitude of the drone, the higher the level of detail obtained in the photos and more defects can be picked up.
Another important factor if doing a solar panel form inspection is using an adequate SD card that writes quickly and have sufficient space. These large scale inspections take hundreds or thousands of photos which are collated to create an orthomosaic, more on that topic in Drone Mapping Explained.
The drone camera needs to be set perpendicular to the solar panels to best capture defects. With thermal imaging, the defects will show up as brighter cells, spots or strips depending on the color scheme.
If you’re looking to invest in a thermal imaging technology, my article on thermal drones goes through the best drones on the market with thermal cameras.
Drone Inspection Mistake 5:
Using the wrong drone for the inspection
There are many types of drone inspection so it’s vital to have the right drone for the job. The importance of having a good camera has already been mentioned but, having a drone that is the right size is key in confined spaces, especially bridge inspection.
Drone Bridge Inspection
To properly conduct an inspection of a bridge the drone needs to easily image the underside of the structure from different angles. The abutment, bearings, columns and headers are all components that need to be checked for corrosion and wear.
If the drone used is too large to navigate around the underside of the bridge then vital defects can go unreported.
The DJI Matrice is a large robust drone often used commercially because of it’s ability to host many different payloads such as LiDAR, interchangeable camera’s and thermal imaging but it’s size and complicated set up is a downfall.
There are several smaller drones that are suitable for bridge inspection and include thermal imaging that I go through in this article.
Final Word on Drone Inspections
Making mistakes while conducting a drone inspection can be costly. It can result in damage to your equipment (leading to down time in the business), damaging to the clients infrastructure or result in costly fines.
To ensure you drone inspection goes to plan:
- Have FAA approved drone piloting certification
- Use a drone camera with adequate resolution (usually 4K)
- Do a risk assessment of the area and check the infrastructure is positioned correctly if mobile.
- Choose the middle of the day for drone solar panel inspection when the solar radiance is above 600W/m2
- Use the correct size drone for the job
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