Industry, Regulators Edge Closer To Beyond Line Of Sight UAS

An AeroVironment Puma AE small unmanned aircraft inspected a dozen miles of power lines in rural Virginia in April to demonstrate flights beyond the operator’s line of sight. The FAA issued a “Drotam” to alert other airspace users, the aircraft carried three different communications links, and the inspections were performed under the watchful eye of a Robinson R44 helicopter.

Such is the reality for beyond-visual-line-of-sight (BVLOS) operations. While the use of small unmanned aircraft systems (UAS), or drones, is becoming routine, it is strictly limited to daylight, below 400 ft. and within visual line of sight in the U.S. and other countries. The FAA does grant waivers to the limits of its Part 107 small UAS rule. So far, 21% of requests are for BVLOS operations versus 65% for use at night.

But the drone industry is pushing to be allowed off the leash and beyond line of sight. It sees the enhanced capability as unlocking the economics of unmanned aircraft to perform tasks such as pipeline, power-line and infrastructure inspections, agricultural surveys and other missions where UAS promise lower costs and higher safety and efficiency than manned aircraft or ground teams.

The Puma tests near Dillwyn, Virginia, involved Dominion Power, which is interested in BVLOS for power-line inspections, particularly after storms. The utility uses VLOS drones for niche inspections but helicopters for detailed inspections of power-line towers and routine surveys of transmission lines between substations approximately 50 mi. apart. Dominion inspects its 6,500 mi. of high power lines at least once a year, looking for leaning trees or broken components.

“With UAS, we would potentially fly more often,” says Steve Eisenrauch, manager of transmission line services. “There’s a big potential for cost reduction once BVLOS is possible.” Post-storm damage assessments and resolving power-out situations are tasks for which Dominion hopes to use UAS. “If a crew can dispatch a BVLOS UAS from a site nearby, fly out, hover and get real-time video, they can figure out how many workers they’ll need, the access and materials required before the work crews get to the office,” Eisenrauch explains.

Other industries have similar use cases. Among the three BVLOS waivers granted by the FAA as of April 21 is one for BNSF Railway, which has been working since 2015 under the agency’s Pathfinder program to enable use of UAS for track inspections in rural areas. Having started in New Mexico and now expanding to other areas, BNSF flies UAS daily over its property along the tracks. The waiver requires the drone to be in sight of visual observers throughout the flight and limits operations to 200-ft. altitude.


The ViaSat terminal for Ligado’s SkyTerra L-band satellite provided continuous connectivity with the AeroVironment Puma. (Credit: Ligado Networks)


Similar BVLOS operations are being approved around the world. In February, Aeryon Labs’ SkyRanger quadcopter flew for Ventus Geospatial and Canadian Unmanned on the Foremost UAS test range in Alberta. Canadian UAVs followed in March, flying pipeline and power-line inspections at Foremost with Lockheed Martin’s Indago 2 quadcopter. In April, Drone Delivery Canada began BVLOS testing at the Foremost range, aimed at gaining approval to begin delivery flights in remote areas of Northern Canada.

Sharper Shape has had approval for BVLOS power-line inspections in Finland since 2014. Approval is pending in Denmark for similar operations by Heliscope and inspection specialist Scopito. In Switzerland in February, SenseFly was first to receive country-wide “anytime” authorization to fly its eBee mapping drone BVLOS, using observers but without having to set up a danger area in advance. In April, Swiss Post conducted approved BVLOS drone delivery trials between hospitals in Lugano. In Israel, Airobotics was approved in March to fly fully automated drones BVLOS, without a certified pilot, over Israel Chemicals and Intel plants.

Electrical utility Transpower in February completed the first BVLOS flight in New Zealand to inspect transmission lines and towers in the Rimutaka Range mountains. Transpower already uses a combination of helicopters and VLOS drones for inspections. In March, Australia’s V-TOL Aerospace conducted day and night, multi-UAS BVLOS test flights in Brisbane, supported by a UAS traffic management (UTM) system using cellphone networks to monitor the drones continuously.

In the U.S., as the result of another FAA Pathfinder initiative, PrecisionHawk in August was granted a waiver for extended-visual-line-of-sight (EVLOS) UAS operations over sparsely populated areas. EVLOS is a subset of BVLOS in which the operator cannot see the drone but can view and scan the airspace in which the UAS is operating to detect intruding manned aircraft. It is based on Pathfinder data showing a trained pilot can detect and avoid aircraft at greater range, up to 2.5 mi. versus 1-2 mi. for non-pilots.

The FAA expected to propose rules for extended UAS operations this year, including EVLOS and limited BVLOS. But a rule allowing flights over people has been delayed by law-enforcement concerns, so new regulations on remote identification of drones will take precedence over extended operations. In addition, the Trump administration’s moratorium on new regulations has placed all rulemaking in limbo.

If progress toward BVLOS is incremental, the reason is safety. “VLOS is the foundation on which the air transportation system in the U.S. is built,” says Jim Williams, principal at New York-based law firm Dentons and former manager of the FAA UAS integration office. “The rule that rules all is that pilots have to maintain vigilance to see and avoid other aircraft. By definition, no UAS flying BVLOS can meet that rule.”

A foundation for BVLOS is reliable command-and-control (C2) data links. The Dillwyn trials were led by Ligado Networks, formerly Lightsquared, which operates a hybrid satellite and terrestrial communications network. The BVLOS tests, staged with the Virginia Tech-led Mid-Atlantic Aviation Partnership test site, used Ligado’s licensed L-band satcom (1.6-GHz) and terrestrial (1670-1675-MHz) frequencies and unlicensed 2.4-GHz wireless spectrum.


A “Drotam” issued by the FAA alerted pilots to airspace being used for a power-line inspection demonstration in rural Virginia. (Credit: SkyVector)


“We’re showcasing the power, availability, reliability and security when you combine terrestrial and satellite links,” says Tamara Casey, Ligado’s chief technology officer. The wireless link connected with the UAS out to 5.4 nm using a high-gain directional antenna, and the 1670-1675-MHz band out to 12.4 nm, the full length of the airspace corridor available. Satellite connectivity was maintained continuously using a small ViaSat terminal mounted atop the Puma’s fuselage.

According to Casey, the satellite is used for C2 and critical telemetry while terrestrial links support both C2 and high-bandwidth payload data. For commercial BVLOS operations, Ligado has petitioned the Federal Communications Commission (FCC) to modify portions of the 40 MHz of L-band spectrum it owns for base stations and mobile terminals. The 1670-1675-MHz band is approved for terrestrial use but required a “special temporary authority” from the FCC for the Dillwyn testing.

“It’s not finalized, but the FAA is looking for beyond-line-of-sight C2 links, critical telemetry and positioning links to have a minimum 99.95% reliability, . . . and depending on how congested the airspace is, we expect those requirements could go even higher,” explains Casey, adding the FAA favors a hybrid terrestrial/satellite architecture. “So we are talking multiple highly secure, reliable and available links.”

Another foundational requirement for routine BVLOS is a detect-and avoid (DAA) capability, likely ground-based at first, to eliminate the need for chase planes and visual observers. Here, the FAA-designated test sites are taking the lead in building infrastructure, to support research initially but eventually for operations.

With $250 million of New York state funding, the Northeast UAS Airspace Integration Research Alliance plans to build a 50-mi. airspace corridor between the Griffiss International Airport UAS test site and nearby  Syracuse, starting in 2018. This will combine primary radar, automatic dependent surveillance-broadcast (ADS-B) and wide-area multilateration to enable BVLOS operations.

The corridor will be used to validate the performance of a large-scale UTM system, using technology under development by NASA and the FAA, says Craig Marcinkowski, director of strategy and business development at radar developer Gryphon Sensors, which led the initial design phase of the project.


In the Dillwyn trails, the Puma flew more than 12 mi. from the operator to conduct simulated power-line inspections. (Credit: Ligado Networks)

The Northern Plains UAS test Site in North Dakota is taking a two-pronged approach based on altitude. Ground-based DAA for larger UAS at higher altitudes will use data from the DASR-11 digital approach radar at Grand Forks AFB. This will enable BVLOS operations in a wedge of airspace out to 60 nm northwest of the airbase, says Trevor Woods, director of operations. Flight tests are planned for June-July, and vendor testing of airborne DAA systems is a likely early use for the airspace, he says.

To enable BVLOS operations by small UAS below 3,000 ft., Harris has partnered with the University of North Dakota and the test site and, with a state grant, is fielding a network of ADS-B ground stations. This will cover the Grand Forks-Fargo corridor but is designed to be scalable to all of North Dakota, and eventually the entire U.S. Testing is planned to begin by year-end and continue into 2019, says Woods.

Ultimately airborne DAA will be needed, but this requires a quantitative definition of “well clear” – the separation UAS must maintain from manned traffic. This has been defined for large UAS (over 55 lb.) and, in November, the multiagency UAS ExCom Science and Research Panel recommended a well-clear definition for small UAS: a 2,000-ft. horizontal by 250-ft. vertical “hockey puck” of airspace around the UAS. If accepted, this will allow development of specifications and regulations for small-UAS DAA.

The technical pieces are coming together, but the economics must be there. “The biggest barrier for BVLOS operations is the uncertainty around the business case,” says Williams. “There is no certificated aircraft with a price tag to let me know what my cost of ownership and operation is going to be. And the reason there is no certified aircraft is there are no real customers banging on the door of the manufacturers, because they don’t know the price point. It is a chicken-and-egg situation,” he says.

“The barriers that made that uncertainty unfathomable are an airborne means of detect-and-avoid and a communications link that can be certified. These are being resolved. The Puma is close to getting FAA type certification,” notes Williams. Whether the price of a certified Puma meets operators’ needs is to be seen, but “we are poised at the edge of the beginning for UAS operating BVLOS,” he says. “In the next couple of years, it’s going to become a reality.”

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