Inspecting Drilled Shafts Without Sending a Person Down
We are not trying to sell a drone service. We are working toward man-entry avoidance.
Inspecting a drilled foundation shaft, which can be roughly 30 inches wide and 50 feet deep, has traditionally meant lowering a person into it on a winch. That is a confined-space entry, with all the permits, rescue planning and risk that come with it. If a camera can go down instead of a person, everyone goes home safer.
This article shares where that work stands, including the hard parts.
Why drilled shafts are worth the effort
Drilled shafts and caissons carry heavy loads, and the condition of the hole matters before concrete goes in. Inspectors need to see the sidewalls and the bottom. Today, getting eyes down there often means sending a person.
Our goal is to give inspectors and engineers a clear view of the shaft from the surface, with no one entering the hole.
The custom FPV build
Off-the-shelf drones are not designed to fly inside a 30-inch hole, so Travis built one. It includes:
Walksnail HD digital video
Diversity video reception, for a cleaner signal when the shaft walls get in the way
A low-light Moonlight camera, because it gets dark fast below ground
Active cooling
An ExpressLRS (ELRS) control link
It is purpose-built for one job: getting eyes where people should not have to go.
The hard problems we are still working on
Flying inside a shaft is harder than it sounds. We would rather share the hard parts honestly than pretend they are solved.
Prop wash. In a narrow hole, the air the drone pushes down has nowhere to go. It bounces back and makes stable flight difficult.
GPS dropout. Below ground level, satellite positioning disappears, so the aircraft cannot rely on GPS to hold its position.
Lighting. Natural light fades quickly with depth, which limits what the camera can see.
Confined-space rules. The whole point is to keep people out of the hole. We plan and follow the applicable confined-space requirements to the letter.
A regulatory curiosity
Here is a question we did not expect to ask: who owns the airspace inside a hole? When a drone is flying 40 feet below ground, is it operating in airspace in the regulatory sense, and do the usual rules apply? We have our own reading, but we are interested in hearing from aviation attorneys, safety managers and other operators who have thought about it.
Where this stands
This capability is in active development, and we are sharing it because we think the industry benefits from the conversation. We will post updates as testing continues.
If your team does drilled-shaft, caisson or foundation work and you want to talk about where this could help, we would like to hear from you. Call or text 540.987.0618, or email drones@topknotchinnovations.com.
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