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American Robotics Reese Mozer on the Many Types of BVLOS Flight: EVLOS, True BVLOS, Automated & More

By Reese Mozer | May 18, 2022

The Many Flavors of BVLOS – an explanation of the different types of BVLOS flight, and what they mean for regulators and industry.

Ah, BVLOS. One of the most consequential acronyms of our time. It also happens to be one of the most misunderstood.

Let’s start with the basics. BVLOS stands for “Beyond-Visual-Line-of-Sight”. That phrase refers to where in space a drone is operating in relation to the Pilot In Command, or PIC. This last part is where the confusion begins. In the aviation world, every flight must have a designated Pilot In Command, regardless of whether the aircraft is a Boeing 747 or an $8 micro-drone from the mall. This “PIC” title refers to a very specific individual that is formally granted the authority to fly and ultimately, the responsibility of the safety of the operation.

Why do the FAA and other regulators care about this? For an aircraft to safely operate in the airspace, the PIC has to have some understanding of the state of their own aircraft and where other aircraft are so he or she can avoid them if necessary, and continue to maintain the safety of the operation and the airspace. For the past 100 years, the primary sensor tasked with accomplishing this ‘see and avoid’ capability was the Mark 1 human eye and brain, hence the emphasis on “visual”.

In the drone world, BVLOS flight can technically occur under a number of very different circumstances, supported by technology, additional people, or a combination of both, and though the same acronym is confusingly used for all of them, the differences between these operations have massive economic and scalability implications. Some people already understand this, some might have a vague comprehension that differences somehow exist, but my guess is most are unaware of the details. And why would they be? This topic is inherently confusing and obscured because there is one acronym being used to describe a host of drastically different scenarios.

All scenarios are typically labeled “BVLOS” in government documents and company marketing materials, so the following are informal designations to describe the varying scenarios:

Note: The discussion below doesn’t include any temporary waivers related to extraordinary circumstances such as natural disasters.

EVLOS with chase aircraft

“EVLOS” stands for Extended-Visual-Line-of-Sight, and is an informal designation in scenarios where additional human eyeballs are used to extend the operation beyond the line of sight of the PIC. This particular version of EVLOS is the lowest and least useful form of BVLOS. A manned aircraft (i.e. a plane) follows a drone while it is flying to monitor the surrounding airspace for potential aircraft collision risks. The pilot of this manned aircraft radios back to the PIC, and instructs that person to take avoidance action if necessary.

EVLOS with VOs

A marginal improvement over chase aircraft, but provides little-to-no value in the majority of commercial scenarios interested in regular operations. This encompasses 90%+ of the “BVLOS” waivers granted today. This method incorporates one or more visual observers (VOs) stationed on the ground in the area of operation tasked with monitoring the drone and the surrounding airspace for potential collision risks. The VOs communicate back to the PIC, and instruct that person to take avoidance action if necessary. If the purpose of drones is to reduce the human labor burden, this achieves the opposite effect: The number of people involved in each operation goes up, and since the human eye can only see a typical drone to about 0.5 – 0.75 miles away, the number of VOs required can be quite large for any reasonable area of operation.

BVLOS with infrastructure masking

Getting closer to commercial usefulness now, but still niche. There have been a handful of approvals under this category. In this scenario, “BVLOS” operation is permitted temporarily where a drone flies under or behind a structure within very close proximity. One example would be a PIC surveying a bridge, and the bridge temporarily occludes the view of the drone as it scans the underside. Another example would be a PIC standing on one side of the building and the drone flies around to the other side of the building, still within very close proximity to both the ground and the structure. The logic is (1) the PIC must maintain knowledge of where the drone is through flight planning and some sort of ground station software, (2) the PIC must monitor the surrounding airspace for potential air traffic threats, and (3) manned aircraft are unlikely to be flying that close to structures on the ground unless something has gone terribly wrong. A handful of these have been granted, and they are mostly geared towards public safety and bridge inspection.


We are now approaching the promised land. “True” BVLOS is the scenario where no VOs are present on the ground during flight. The PIC is located somewhere remotely, looking at a remote software interface with real-time position and telemetry data. To detect other potential aircraft threats in the area of operation, some form of Detect-and-Avoid (DAA) sensor technology is employed. There are three categories of technology proposed for this: radar, optics, and acoustics (each with various pros and conS). These sensors can theoretically be mounted to the drone or installed separately on the ground. Whatever is chosen, this sensor must be able to detect crewed aircraft in all directions at distances far enough to safely allow an avoidance maneuver. I will avoid the math here, but the typical outcome is a requirement to reliably detect aircraft many miles from where the drone is operating. This information is streamed back to the PIC in real time, and either a manual or automated action is taken in the event of a collision threat. Less than 10 of these have been granted in the United States.

Automated BVLOS

What’s the difference between automated BVLOS and true BVLOS? A single drone flight typically has little to no value. Whether you are trying to deliver packages or collect thermal data on a power plant, the idea is to do this over and over again, multiple times every day, forever. Thus, the question of what happens before and after flight comes up. That is the purpose of drone-in-a-box (DIB) systems, where you install said box in the area you wish to operate, and it lives there conducting its missions autonomously every day. To operate BVLOS before, during, and after flight, the final step is to overcome the regulatory requirement for in-person pre-flight checks. This means remotely determining that both the drone and the immediate surrounding area is safe for takeoff. If you can achieve all of that, you now have an economically viable product for the vast majority of the commercial markets. Only 2 of these approvals have ever been granted, and only one of them to a drone manufacturer: American Robotics.

Reese Mozer, President of Ondas Holdings
About the author

Reese Mozer is the co-founder and CEO of American Robotics Inc. The Marlborough, Mass.-based company is an industrial drone developer specializing in rugged, real-world environments. Through innovations in robot autonomy, machine vision, edge computing and AI, American Robotics said it has created the next generation of drone technology: a fully-automated drone capable of continuous, unattended operation.

Mozer is an entrepreneur, leader, and roboticist with a decade of experience designing, developing, and marketing autonomous drone technologies for the commercial sector. He holds a master’s in robotic systems development from Carnegie Mellon University. Mozer is a member multiple drone and robotics industry standards bodies and associations, including the FAA Center of Excellence for UAS Research (ASSURE), the Association for Unmanned Vehicle Systems International (AUVSI), the Commercial Drone Alliance (CDA), and the Massachusetts Technology Leadership Council (MassTLC).

Source: DroneLife


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