Tools of the Trade: Drones for the 21st Century Investigator

By Bill English

Throughout its history, the NTSB has prided itself on staying on the cutting edge of transportation technology. One of the most revolutionary changes ever to come about in aviation is the recent explosive growth—in number and capability—of unmanned aircraft systems (UASs), or drones. Last year, the number of registered UASs exceeded the number of manned aircraft. Nothing has drawn as much attention in aviation as the UAS revolution.

CBP MQ-9 crash near Nogales, Arizona, in 2006
CBP MQ-9 crash near Nogales, Arizona, in 2006

This phenomenon didn’t surprise us at the NTSB. Our first occasion to investigate a UAS accident came in 2006, with the crash of a Customs and Border Protection Predator-B MQ-9 near Nogales, Arizona. That investigation gave us a glimpse into the future of civil commercial drone use. In 2008, we held a public forum on UASs. Soon after, we officially acknowledged that UASs represented an expansion of the aviation world that we needed to thoroughly understand.

My entry into the world of UASs began with a side task: learn enough to update Title 49 USC Part 830. We published a revised regulation in August 2010, clarifying the NTSB’s role in investigating UAS accidents. The revision remains valid today, even with all the changes in the industry, and so far, civil, nonhobbyist UASs have a very good record: at the time of this writing, they have caused zero serious injuries and resulted in zero confirmed collisions.

NTSB in vestigators using a UAS to inspect an inflight breakup
Using a UAS to inspect an inflight breakup

The NTSB began experimenting with small UAS (sUAS) technology that could support on-scene accident investigation in 2013. By 2015, we had taken the first real steps toward using UASs to support multimodal accident documentation, obtaining authorization to research sUAS methods and to fly in the DC Special Flight Rules Area, and we began test flights. In early 2016, we started the process of obtaining a public agency Certificate of Authorization (COA) and also began procedures to expedite access to controlled airspace. In April, we made our first flights over an accident site under the COA.

We kept up with the quickly expanding rules for flying small UASs. The FAA published the sUAS Part 107 regulation in August 2016, and we were one of the first in line for a Part 107 certificate. Since then, we’ve developed Federal Flight Program documentation and procedures, conducted more deployments, and obtained our “flagship” drone, a DJI Inspire.

Overhead image of accident site taken by UAS.
With photogrammetry, an orthomosaic can be created in less than an hour.

As we started to gather information and gain experience with drones, we quickly realized that sUASs and their associated technology—small, high-resolution cameras and processing software—would be great tools for NTSB investigations. One such use of this technology is photogrammetry, which, using pixels from multiple photos of an object or area, creates a 3-D model or an orthomosaic (a map with geographical coordinates throughout). We know the value of aerial photographs; there is hardly a major NTSB accident report without an aerial image in it. But with a drone, we can now take high-quality photos, our investigators can specify the most important points of view, and we can immediately review the results. We can re-fly an approach path to view witness marks or runway alignment and quickly obtain high-quality photos of hard-to-access areas (for example, a plane crash into a building that our investigators cannot safely enter).

3-D model of a collapsed rail terminal
3-D model of a collapsed rail terminal

Photogrammetry, especially when it’s enabled by digital GPS-referenced photos, is the real game changer. Gone are the days of hunting through dozens of photos for just the right point of view, or scribbling down a few GPS points and hoping you took the right measurements. Orthomosaic maps and 3-D models let you go back for whatever you need. Our team continues to deploy to accident sites in aviation and rail, and we can now can deploy a drone to an accident site on request—with our COA approval, we can even get the OK to fly in controlled airspace within hours—and our photogrammetry-trained staff continues to grow. Every time we document an accident site, we learn more and get better at using the equipment and techniques.

NTSB investigators involved in photogrammetry training
Photogrammetry training

We intend to keep growing the UAS program and the ability to bring in external partners. Building this program has had an unanticipated side benefit: To operate the drone, which is an aircraft by all definitions, we developed a flight program following the Interagency Committee for Aviation Policy template. Now, anyone who wants to be involved in any aspect of flight operation—whether it be by putting together safety and operational procedures, developing training and standardization, or carrying out safety reporting/SMS activities—has a way to participate in our own little flight department!

NTSB investigators use a UAS for a high-elevation search
High-elevation search

As we grow in our knowledge of UASs, we’re able to maintain our high investigative standards in an expanding segment of aviation and improve our investigative techniques, giving our investigators an opportunity for hands-on experience.

Bill English is an Investigator-in-Charge in the NTSB’s Major Investigations Division and leads the UAS program. He is a current CFI-I who holds an FAA remote pilot certificate and a graduate certificate in geospatial intelligence.

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