Drones Can Be Useful in Inspecting Towers and Antennas

Here’s what I’ve learned so far

The author is vice president of engineering at Educational Media Foundation (K-Love/Air1).

One Christmas many years ago, two separate people gave me identical model P-51 airplanes with gas motors. I think I was in eighth grade or maybe early high school, but it was pretty hard to watch politely as everyone else opened their gifts with two airplanes staring at me! Visions of brilliantly executed aerial dogfights filled my head while I feigned interest in my family’s other gifts.

Drone photos can help ensure tower crews installed all bolts and pressure-relief valves.

Finally, my dad, brothers and I escaped to the backyard and we unpacked the planes. They were the old-fashioned type, controlled and tethered by means of a couple strings between the handle and the plane. We assembled and fueled one, spun the prop until the engine fired, and soon my first unmanned aircraft was in the air!

Unfortunately, that first flight was far shorter than the Wright brothers’ inaugural journey. I think I made about one quarter of a rotation before the plane “landed” nose-first, embedding itself in the lawn.

Surprisingly it was undamaged, so we launched it again, this time with dad flying. His flight was only slightly more successful. (I expected more given that he was a licensed pilot.) By the end of the afternoon, the four of us had pretty much trashed both planes, launching, crashing and borrowing parts (from the second plane) until we could no longer consider either one airworthy. Perhaps neither ever was, since we never flew longer than a few seconds — though that blame probably falls squarely on our string-piloting skills.

Sam Wallington readies a DJI Phantom 3 Professional drone for a tower inspection.
Photo by Jeremy Preece

Unmanned Aerial Vehicle technology has come quite a ways since then, not only adding radio control capabilities (still requiring significant skill) but GPS and computer control, so that nearly anyone can successfully fly some models. With great cameras to record the view, combined with very reasonable prices, it is no wonder there is significant interest in owning and flying drones. Indeed, UAVs are becoming a multi-billion-dollar business.

All of this interest has caused the government to take notice. Congress wanted to ensure that hobbyist use of drones was reasonably unrestricted, and therefore limited the Federal Aviation Administration’s regulation of private use of drones. The FAA, however, has taken steps to control what they can — using UAVs for work.

The first time I saw a modern drone in person was at a trade show. A huge crowd had gathered around the DJI booth as a drone flew around inside a net cage. People stood in line for the opportunity to act as pilot for a few minutes. Pretty impressive, and when I started asking questions and found out that I could buy one for much less than I thought, I was hooked. I spent more time learning about how they had designed on-board computers to handle the core flight characteristics, leaving just the fun part of flying to the pilot:  Which way to go? What to see?

That version of the DJI aircraft used a GoPro camera (another very popular booth at the trade show), but DJI and other manufacturers have since expanded to include numerous camera options, including 4K and infrared cameras. Great cameras combined with sophisticated controls allow tremendous power for a very reasonable price.

The main reason I wanted a drone for work was to perform tower inspections. I happen to like climbing towers, but the costs of maintaining certifications and insurance can become prohibitive, plus I found that not many of the engineers on my team share my love of heights.


Jeremy Preece flying a drone.

I asked our station attorney about the rules for drones, and he referred me to an FAA consultant. The consultant, in turn, explained that though we are part of a non-profit organization operating non-commercial stations, we fell within the FAA’s definition of “commercial” use. Regardless of the source of the money, being paid to fly or flying a company-owned drone constitutes commercial use and is therefore regulated.

At the time, it was necessary to ask the FAA for a Section 333 waiver, so we spent some time building that out and submitting our application to do so. Meanwhile, however, the FAA had been working on streamlining the rules because of the strong interest in using drones for business purposes. Before our waiver request was granted, the FAA created the rules necessary to license and regulate commercial drone use, releasing them as 14 CFR part 107 (see sidebar).

Once the FAA released the new rules, we researched how to become licensed and learned that already licensed and current pilots only needed to pass a test on the new Part 107 rules, but everyone else had to also demonstrate other flight knowledge and be vetted by the TSA. Because the only thing I’ve ever wanted to fly was a helicopter, and I had never made that a financial priority, I have never had a private pilot’s license.

Accordingly, it was necessary to take the full test, and I did so two days after the new rules went into effect.

The FAA has a free online study course and test for Part 107, designed to add remote pilot certification to already licensed pilots. I took that course and test over a couple hours, and encouragingly, passed.

Jeremy Preece, left, and Sam Wallington use a drone to take a self-portrait.

The rest of the test was harder to prepare for. It covers subjects as wide-ranging as the effects of weather on a UAV (or, in the FAA’s parlance, UAS — Unmanned Aerial System, or sUAS—small Unmanned Aerial System), chart reading (to determine whether the UAV is allowed to fly in a particular type of airspace, the frequency of a particular airport tower, the elevation of obstacles and the like), loading of an aircraft and safety.

At the time, there weren’t many obvious study options for that part of the test, short of taking a ground-school-like course taught by some enterprising businesses. Instead, I spent a number of hours online studying the FAA’s documentation and whatever else I could find. Since then, the FAA has fleshed out and better organized that information, making it now relatively easy to study for the exam.

The exam itself costs $150 and is administered by a local FAA testing office. If you don’t pass, there is a required delay and a retake of the test at additional cost, so it’s worth the effort to go in well-prepared.

When I took mine, I was instructed about the consequences of cheating or revealing specifics about the test questions, then escorted to a testing room (with another candidate taking the test) and seated at a computer.

Avoid flying in the aperture of live antennas.

The questions are selected randomly from a pool, and you’re given a couple hours to complete the test. You can easily navigate within the test to go back and review or change your answers or skip a question you’re unsure about. I was loaned a bound book containing diagrams and portions of sectional air charts, and the test refers to pages in the book to answer specific questions. With my over-40 eyes, I truly regretted not bringing reading glasses.

Once my exam was completed, I was escorted back to the front desk and given my results (I passed!). I was given a paper marked “do not lose,” which showed my score, the specific questions I missed and other pertinent info. That document is used to apply for a temporary license, which was granted a few days after I applied. At that point, I could legally fly a drone for business purposes.

After a few weeks, my permanent driver’s license-like license was mailed to me. A few weeks after I received my license, a coworker also obtained his, and we were excited to finally put the station’s drone in the air.


Drones let you check for guy point or paint issues without climbing.

Though modern GPS-and-computer-aided drones are easy to fly, practice is still a required part of the journey. My coworkers and I have found that an empty field or the parking lot behind the station make excellent locations for becoming comfortable with takeoff, landing and maneuvering the aircraft.

Because the purpose is to generate usable video, it is necessary to practice being smooth in moving the aircraft. Additionally, practice builds muscle memory, so moving the correct joystick in the right direction to ascend, descend, fly or rotate in the desired direction becomes automatic. Practice also helps resolve potential confusion when the aircraft’s left and right differs from my left and right, depending on the direction the UAV is flying.

Practice doesn’t end once flying is reasonably mastered. Good camera control is important so that starting and stopping recording, tilting the camera up or down, controlling exposure or taking still pictures becomes quick and easy. Eventually, with enough practice, recording a shot with the UAV “trucking” left or right while ascending or descending can become second nature — and makes the resulting videos a pleasure to watch.

Though a drone itself is relatively inexpensive and may or may not be worth insuring, it is important to cover any potential liability caused by the drone.

Thinking worst-case scenario, liability might include a failure, causing the drone to crash into a propane tank, which then explodes and kills or injures someone. Perhaps more realistically, what if the station is sued by someone living near the transmitter site for violation of their privacy? Or if an employee is cut by the rotating blades? Insurance companies are just feeling this out, so rates may be higher than you’d expect (hopefully competition and real-world “practice” will drive rates down in the future).


Registered drone, Remote Pilot license, insurance and practice. Finally, all the pieces were in place, and we could go inspect towers!

Drone photos can alert crews about work challenges before they climb — in this case, rusted bolts.

Our first few attempts were useable, but we’ve learned a few things along the way you might find helpful. Flying at a tower site is a study in awareness. There are many potential obstacles, some of which (like guy wires) are difficult to see. Also, sunlight, while helpful for great video, does make it difficult to see the UAV control screen (I recommend an inexpensive “hood” to block the light). When the sun is not directly overhead, it is best to fly between the tower and the sun so the tower is well lit — plan the timing of the visit accordingly.

With off-the-shelf drones using standard camera systems, it can be necessary to fly quite close to the tower to get a desired close-up shot. The signal from a nearby high-power FM, TV or microwave antenna may overload the control radios on the drone when it gets too close, resulting in activation of the drone’s “return-to-home” safety software. Accordingly, RF fields must be anticipated and planned for. It is wise to experiment under controlled conditions to understand how a particular drone will react to RF in different frequency bands.

There are a couple possibilities to resolve this challenge. First, aftermarket cameras with higher power and/or zoom lenses may be a viable solution. Better lenses can allow the drone to obtain good quality images without approaching a transmitting antenna too closely.

Second, taking the high-power signal off the air may be a viable option — just like a station may have to go off-air to protect a tower crew. A drone’s flight can be relatively quick, as it requires no rigging or climbing around obstacles, reducing the duration of the outage. If only a single part of the antenna is to be inspected, the drone can fly to the correct elevation horizontally separated from the antenna before the station is powered down. The drone can then move in horizontally, get the required video, and “retreat,” allowing the station to return to operation even before the drone lands.



(condensed from https://www.faa.gov/uas/media/Part_107_Summary.pdf)

Operational Limitations (potentially waivable):
● Unmanned aircraft must
* weigh less than 55 lbs. (25 kg).
 * be operated during daylight only
 * yield right of way to other aircraft
 * move at a maximum of 100 mph (87 knots)
 * operate no more than 400 feet above ground, or within 400 feet of a structure
 * remain within Visual line-of-sight (VLOS)
 * fly with a minimum weather visibility of 3 miles from the control station
 * not operate over people not directly participating in the operation
 * be registered (Foreign-registered sUAS must also satisfy part 375)
 * carry only loads that are securely attached and do not adversely affect flight
Permitted Operations
* Flight in Class G airspace without Air Traffic Control (ATC) permission, in Class B, C, D and E airspace with ATC permission
 * Transportation of property for compensation or hire (with restrictions)
Operations NOT permitted
* from a moving aircraft
 * from a moving vehicle unless the operation is over a sparsely populated area
 * careless or reckless operations
 * carriage of hazardous materials
Remote Pilot must
* not have any physical or mental condition that would interfere with the safe operation
 * either hold a remote pilot airman certificate with a small UAS rating or be under the direct supervision of a person who does hold a remote pilot certificate (remote pilot in command).
 * demonstrate aeronautical knowledge by either passing an FAA aeronautical knowledge test or hold a current part 61 pilot certificate other than student pilot and complete an FAA small UAS online training course
 * be vetted by the Transportation Security Administration.
 * be at least 16 years old.
 * make available to the FAA, upon request, the sUAS for inspection or testing, and any associated required documents/records
 * report to the FAA within 10 days any operation resulting in serious injury, loss of consciousness or property damage of at least $500
 * conduct a preflight inspection, to include specific aircraft and control station systems checks, to ensure the small UAS is in a condition for safe operation.
     (A remote pilot in command may deviate from the requirements of this rule in response to an in-flight emergency)
Model Aircraft
Part 107 does not apply to model aircraft that satisfy all of the criteria specified in section 336 of Public Law 112-95.
The rule codifies the FAA’s enforcement authority in part 101 by prohibiting model aircraft operators from endangering the safety of the NAS.

One time, I began my flight from one side of the tower, and during the flight decided the lighting would be better if I moved to another side. However, after doing so, I flew the drone close enough to an energized antenna to cause it to momentarily lose communication with the controls, and the drone went into “return home” mode. It immediately flew through the guy wire path — fortunately between the wires themselves — to get back to the side I’d started on, as that was set as “home” to the drone. Though there was no actual problem or damage, it was a good reminder to remain aware of where “home” is. Regardless of the reason, the drone could try to return there at any time, so make sure it won’t have to travel through an object to get there.

Be sure to use the control software to set the return home minimum elevation to an appropriate level. For example, if you will need to fly on multiple sides of a tower, you could set the return-to-home elevation at 10 or 20 feet above the height of the tower’s tallest appurtenance. That way, activation of the return-to-home feature will cause the drone to ascend above the tower before it returns to its home coordinates and begins descending, ensuring it won’t hit the tower, an antenna or guy wires.

Once these precautions are met, it’s possible to get great photos or video of antennas, their mounting bolts, guy anchorages on the tower, lighting structures, paint condition, coax routing and many other details of the tower’s configuration and situation.

Using a drone with a tower crew on site adds two additional benefits. By flying the drone before the crew climbs, it is possible to document the “before” situation as well as accurately communicate challenges or work specifics to the crew. Spending a few minutes with the drone video can help the crew see where problems lie or anticipate problems that can’t be seen from the ground (for example, a missing bolt). This knowledge can ensure an efficient use of the crew’s time and enhance their safety.

Once the crew finishes its work and clears the tower, a second flight can validate that the work has been completed satisfactorily. The crew may carry digital cameras that can provide feedback about things they’re aware of; the drone can supplement that with other views they may not have thought to check, and validate that all bolts are in place, etc.

Towers are just one area where UAVs can be helpful in broadcasting. Inspecting roofs, overhead cable routing (being careful to avoid any high voltage lines) are all easy possibilities. We even used our UAVs to provide nice overview shots as part of updating our building evacuation training video during a recent fire drill. Investing in obtaining licensing and an appropriate drone can pay off.

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