Going Beyond visual line of sight (BVLOS)

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Beyond visual line of sight (BVLOS) is the most talked about concept in the commercial-drone world today—and for good reason. Many of the most lucrative opportunities for introducing drones into real-world commercial use are based on inspecting and gathering data over large swaths of land, such as railroads, utility lines, and farms that require autonomy. There are two key factors that make BVLOS flight a tipping point for commercial-drone industry expansion. The first is enabling service providers to conduct complex drone operations, such as long-line transmission inspection without having to have the drone in sight.

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BVLOS drones bring efficiency and speed to the task of collecting data over large areas, like those along railroad tracks.

This makes these tools much more viable to replace helicopters or other methods of current inspection, and opens up serious opportunities for introducing safer inspection operations into the world. The second is enabling drones to be able to conduct truly unmanned flight with no pilot needed for takeoff or landing. This has happened already in Europe, with power company Enel using Percepto, the drone-in-a-box system, for power-plant inspections related to operations, maintenance, and protection. Cutting humans out of the loop allows for additional use cases and drives the cost of data acquisition down, making use cases in low-margin industries more likely.

Right now in the United States, companies are operating under waivers for BVLOS, and there are several initiatives looking at the safe, autonomous applications of commercial drones and operation with ground support from longer distances than line of sight. The investor interest in this space and the corporate eyes in energy, agriculture, and banking keeping watch around regulatory timing are at a peak. This article will walk through barriers to manufacturing adoption from a regulatory standpoint and shed some light on key concepts everyone should know.

BVLOS is the next step in the future of drone operations and autonomy, but drones have to become airworthy to get there. In this report, we’ll break down the technical and regulatory requirements that must be addressed and to summarize what is known and what is still unclear. To make a drone ready for BVLOS operation, several technical and legal requirements have to be addressed. The primary concern for manufacturers and pilots of BVLOS systems will be meeting the dynamic regulatory requirements for airworthiness put forth by the Federal Aviation Administration (FAA). Related to this FAA compliance, BVLOS-ready systems require robust detect-and-avoid technology for safety as well as long-range reliable and redundant communications technology. We’ll review all three of these major requirements for implementing BVLOS systems.

The FAA’s charter gives the agency the task of regulating civil aviation and promoting safety. Its certifications extend to both manned and unmanned aircraft. “Airworthiness” is the FAA’s designation for individual aircraft that it deems safe to fly. In 14 CFR 3.5, the FAA defines an airworthy aircraft as one that “conforms to its type design and is in a condition for safe operation.” In other words, the FAA aims to recognize different types of aviation technologies and implement detailed regulatory requirements that show individual craft match the “type design” it has already certified. A Boeing 747, for example, has to meet different requirements than a DJI Mavic, but both need to demonstrate precise and consistent implementation of their respective design plans with the exception that the Mavic does not have a “type design” at this time.

As defined in 14 CFR 91.203 and 14 CFR 91.7, “air­worthiness” refers to both the official certification given to an aircraft and the aircraft condition, which has to be maintained for safe flight. An Airworthiness Certificate gives authorization to fly an aircraft. Paper certification alone is not enough, however, and broken aircraft are obviously not cleared to fly by the FAA. There are exceptions to these certificates. Through Part 107, the
FAA has waived the need of Airworthiness Certificates for low-risk category aircraft. This has allowed commercial drones to enter the National Airspace System (NAS) without needing to pass rigorous airworthiness criteria. These low-risk aircraft are limited, however, to low-altitude, short-distance flights in less-populated areas and cannot be flown over people or properties without consent. They also require a human observer within line of sight at all times while airborne. While there are waivers for Part 107 to perform slightly-higher-risk operations, BVLOS flight will almost always require FAA certification, unless you are flying in testing facilities or remote locations, like the desert.

Beyond the Airworthiness Certificate, the FAA pro­vides two other certifications that are important to manufacturers of unmanned aerial vehicles (UAVs). The Type Certificate confirms that the design of the aircraft is up to par with safety standards and provides specific technical and design requirements about the class of aircraft. The Airworthiness Certificate, by contrast, shows that the individual aircraft fits this approved type design. Manufacturers will also want a Production Certificate. Given that the manufacturer already holds a Type Certificate, the Production Certificate attests that the manufacturer can consistently produce airworthy aircraft and authorizes the production of the aircraft at scale. The Production Certificate allows manufacturers to automatically receive Airworthiness Certificates for every individual aircraft (of the certified type) that they manufacture.

These standards for airworthiness have been based in the last century of manned aviation. Balloons, single-engine planes, rotorcraft, jets, and helicopters have all passed through these regulations as types. Type standards for unmanned civilian aircraft, however, do not yet exist and do not fit into other type standards for these other aerial technologies. The FAA is now faced with a difficult problem of creating a new regulatory framework for assessing UAV airworthiness as its own type. Although many in both industry and government are eager for new regulations to be passed and to be rid of complex exemption processes, these new frameworks require years of flight data and industry-regulator partnerships in order to develop standards for safe flight and type classification. Meanwhile, manufacturers are able to get by with manned-aircraft certification standards. 14 CFR 21.17(b) provides the interim solution: The FAA (and especially the Los Angeles Aircraft Certification Office) picks and chooses requirements which, although intended for manned aircraft, are “found by the FAA to be appropriate for the aircraft and applicable to a specific type design, or such airworthiness criteria as the FAA may find provide an equivalent level of safety.” For manufacturers, this process entails reviewing many requirements (on the scale of thousands) intended for manned aircraft and demonstrating that the UAV either satisfies the requirement or is categorically exempt from the requirement because of its type design. In the simplest case, a manufacturer might file an exemption that it does not need to include a flight manual on the UAV. It is not always this easy, however, to dissect the regulations and determine whether or not they apply in the absence of an onboard pilot.

Both the FAA and the National Aeronautics and Space Administration (NASA) have made recent efforts to push forward the current framework of airworthiness. The FAA’s Unmanned Aircraft System (UAS) Integration Pilot Program, for example, has created opportunities for state and local governments to partner with pilots and manufacturers to help bridge the gap between regulatory standards and industry needs. NASA’s Systems Integration and Operationalization demonstration has been another leading effort toward UAS airworthiness certifications. The Pathfinder Program is the cutting edge of development, where regulators partner directly with technology companies to explore the concepts they wish to refine for developing future regulatory standards. These industry-regulator partnerships are at the forefront of making BVLOS airworthiness certifications a reality.

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“Detect-and-avoid” capabilities ensure that BVLOS drones don’t interfere with full-size aircraft and other obstacles.

As all manned aircraft pilots know that successful flight depends on the concept of “see and avoid.” The world outside the cockpit window receives just as much attention from the pilot as the complex instruments on the dashboard. Indeed, the FAA codifies this “see and avoid” rule in its right-of-way rules for the NAS (14 CFR 91.113). Though many of these regulations for air traffic are common sense, the language of “seeing” has presented some difficulties for UAVs. So far, UAV manufacturers have met these regulatory requirements by limiting drone operational capabilities, but other notions of “sensing” and “detection” have been gaining traction in the regulatory space.

In 2016, the FAA updated its “see and avoid” right-of-way rules to include UAVs in 14 CFR 107.31—Visual line of sight aircraft operation. Section 107.31 requires that the remote pilot or visual observer knows the location, attitude, altitude, and direction of the UAV and is able to observe the airspace for hazards and determine that the UAV does not endanger life or property. By avoiding any explicit lateral boundary, these rules give a way for remote pilots to “see and avoid” specific aircraft in question but do not provide any direction for fully autonomous flights. The boundaries of VLOS, however, are not always clear, as demonstrated by the PrecisionHawk Extended Visual Line of Sight (EVLOS) Pathfinder Program. This program successfully applied for a waiver to section 107.31 to extend its lateral boundary to 2.5 nautical miles (NM). The FAA determined in this case that, even though the unmanned aircraft itself could not be seen at 2.5 NM, other manned aircraft could be observed at this distance. This is a tangible step toward flights outside of human vision. Going further, NASA has suggested that instead of “see and avoid,” UAVs should be held to a standard of “detect and avoid,” where the UAS is able to use computers and sensors to detect nearby air traffic and safely navigate accordingly. Detect-and-avoid systems can take a variety of different forms. The sensors might be on the aircraft itself (typically, radar) or might take advantage of networks of ground-based sensors (radar coverage). Traffic-management platforms can also manage UAVs so that they maintain distance from each other. A number of companies and technology solutions are emerging in this dynamic space. Still, there is some ambiguity in the FAA regulations about staying “well clear” of other aircraft. Although these regulations have not yet taken a finalized and polished form, it is clear that unmanned aircraft will forfeit right of way to manned systems, so detection and avoidance will be crucial systems for any UAV.

While being able to detect other aircraft outside the pilot’s line of sight is essential to drone safety, it is not the only issue raised by BVLOS. Extended-distance drone operations also communicate command and control information and other data back to the people who need it without link loss, so reliability and redundancy are both essential. Several different types of communications systems can be used to communicate with BVLOS drones, and we break down the popular choices below. These systems vary in four main ways: data costs, hardware costs, coverage and data speed, and caps.

Satellite. Satellite communications (Satcom) are used by the U.S. military for drone operations. These systems are the most expensive but can be used at the largest scale. Satcom is both reliable and can send large amounts of data. With Satcom, you can select a network, a modem, and a service provider based on estimated data usage and the type of connection needed for the operation. Service providers, such as Iridium and Inmarsat, offer global-coverage low-bandwidth machine-to-machine (M2M) services and high-bandwidth services (for a much greater cost available in 2018). M2M systems are the most economical choice for Satcom, if it is possible to optimize the C2 link for minimal data transmission.

Cellular. Drones can also transmit data like smartphones do via cellular networks (Cellcom). These systems haven’t been used for drones for as long as Satcom has, but they are gaining in popularity for commercial UAVs. Cellcom performs well for multirotor drones in low-altitude settings as well as for BVLOS. Cellcom can be better for real-time streaming than Satcom as 4G or even 3G networks are capable of much higher data rates than satellites. The pros and cons of cellular networks both lie in the fact that they are an already-existing infrastructure. Because of this, they are not optimized for the ways drones use data. Drones using Cellcom technology will be uploading large quantities of data using a system that is primarily designed for downloading media. Additionally, many of the places in which drones can be flown also won’t be high-volume cell-service areas. Although Cellcom for UAVs uses the same service providers that cell-phone users do, UAV operators in remote areas can also take advantage of “dual-radio” modems, which will increase coverage by spanning service areas of multiple providers.

Radio. UAVs can also transmit data using point-to-point radio links. Radio communications avoid service fees that come with other communications technologies, but upgrading to new hardware can be significantly more expensive. Radios will work independent of weather or network coverage, and the equipment for operation is portable. Depending on the needs of the operation, radio antennae might fit in a suitcase or might have to be carried in the bed of a truck. Depending on the particular use of the drone, available radio frequencies can include the industrial, scientific, and medical FCC bands (900MHz, 2.4GHz, 5.8GHz) or the licensed S and L bands. Although communication security is a concern with any technology or protocol, it is a more specific concern with drones using unlicensed frequencies. In addition to the risk of a malicious agent hacking a drone-control radio signal, even a local radio signal operating in a nearby frequency could cause interference problems with drones. The Radio Technical Commission for Aeronautics has proposed dedicated waveforms and frequencies to solve some of these security issues, but they are still in the process of being designed and implemented. Meanwhile, unlicensed bands with upgraded radios can still deliver strong results with relatively minimal risks, and changing your radio communicating frequency later will not cost you.

What does the acronym VTOL mean? What type of aircraft are they, and why haven’t we seen more of this type of craft in the last few years? Why is everyone so excited about them, and how do they work? “VTOL” stands for “vertical takeoff and landing.” Any quadcopter or drone by DJI or a similar manufacturer is technically a VTOL drone because it takes off vertically and lands vertically, meaning it doesn’t need a runway. So the concept, by definition, isn’t particularly special, but what is special is a fixed-wing aircraft that can take off and land vertically, sometimes referred to as a “hybrid” from the first use of the technology—it takes off like a helicopter and flies like a plane. When you hear the term “VTOL” referred to in the modern commercial-drone industry, it’s safe to assume speakers mean a fixed-wing VTOL because they are shortening that term. Helicopters and multirotors are actually not very efficient at flying because they are using a significant amount of thrust to hover. This is why a multirotor has less battery life if it’s just hovering still versus flying forward at high speed. But even when a multirotor is flying forward at a consistent speed, it is still mainly relying on downward thrust to keep itself in the air, which is incredibly inefficient. There is a small amount of wing effect from the rotor disc flying through the air, which is why multirotors get a little bit more flight time when they’re in motion as opposed to hovering. Most VTOLs (as the industry uses the term) are fixed-wing aircraft that use a multirotor-style propeller setup to be able to take off vertically and then transition into forward flight. What you’ll generally see is four to six rotors that lift the drone into the air, with one pusher prop in the back so that, as it starts to transition into forward flight, the wings can start giving the aircraft lift. The lift from the wings means the drone needs less and less downward thrust from the rotors that lifted it off the ground. Once the pusher prop comes on, the drone turns off the lifting props, and now, with the single pusher prop, the drone flies as an efficient airplane, with the aerodynamics of an airplane wing. These aerodynamics mean it can get significantly faster flight speed and longer range as a fixed-wing aircraft than it can as a multirotor.

For years, there has always been a point in drone development when an engineering team says, “Well, if you need really long flight time and long endurance, we need a fixed-wing craft,” with the result that drone systems over the years were launched with a catapult system, with rubber bands, or by hand. These systems were a big hassle to launch and even more of a hassle to land because you would need a long runway, which isn’t practical. There are few places that have a nice, long runway for an autopilot on a fixed-wing drone to come down from the air and land itself. This logistical challenge led to massive net systems and wild apparatus to try to catch these drones, sometimes costing hundreds of thousands of dollars, out of the air. Fixed-wing drones were never particularly practical.

Drone developers eventually wanted to combine the benefits of vertical takeoff and landing that you find in multirotors and helicopters with the longer flight time and endurance of fixed-wing unmanned aerial vehicles. We now have fixed-wing VTOL, where these two things are built together. One thing Chris Anderson from 3DR has said many times is that these drones were, for a really long time, kind of like a spork, where you get a not-very-good spoon and a not-very-good fork. The reason this was so hard was because the flight code had to be high quality, and the speed controllers and the motors had to be accurate. Why? Imagine taking off with just a multirotor drone with no wings in 15mph winds; it may be getting blown around, but it’s able to stabilize itself fairly well in wind. Add to that multirotor some big planks for wings. As you take off, you have 15mph winds hitting those big wings; the multirotor, with its propellers, have a hard time stabilizing those wings in the wind. This becomes a big development and technology-component challenge. Next comes the difficult part, especially from a flight code perspective, which is to transition into forward flight. Transitioning from an autopilot flight code stabilizing a fixed wing into an autopilot that’s flying a multirotor and vice versa involves two different types of flight code. Making that transition in real time without letting the aircraft flip over, lose control, or crash is a difficult thing to figure out. There are whole teams of open-source and corporate engineers working on this code, along with lots of interesting designs created to try to circumvent many of the challenges of transition.

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Wingtra is a fixed-wing drone designed for mapping and surveying applications.

Now, for the first time, we’re starting to see, affordable, reliable solutions of various types that are able to make this work. This opens up many operational possibilities for commercial drones. Today, if you want to use drones for inspecting a large mine, a long transmission line, or a railroad line, they mainly just hover inefficiently even when they are flying forward and are, thus, not able to cover that much ground with one flight. With a fixed-wing VTOL, you can cover a lot of track or capture a larger mine or farm, with the added benefit of being able to take off and land in a small defined area like a multirotor, which gives users the best of both worlds. As people are trying to cover larger areas with mapping missions and as companies are preparing for logistics, delivery, longer-range operations, surveillance operations along borders, and the majority of operations that are beyond visual line of sight, it often makes sense to be using a fixed-wing aircraft because you get four to five times the flight time of a multirotor.

One of the recommendations from the Pathfinder Program was that all BVLOS flights should involve a thorough risk assessment. This assessment is not an established regulation but should be considered as a likely requirement and a necessary best practice. A comprehensive assessment should speak to the following points: What functionality must the assistive technology be capable of to enable safe BVLOS operations in the NAS? How do we expect operators to engage with the assistive technology? In what ways can this human-machine system fail? How do we mitigate the risk of failure? The answers to these questions will surely pave the way toward safely and effectively integrating BVLOS flights into the NAS. I hope this has provided some insight worth considering and integrating into your business plans for this year.

By Colin Guinn


Updated: April 11, 2019 — 1:53 pm

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