Seeing beyond the long-range potential of UAS

Exemptions for the commercial operation of unmanned aerial systems (UAS) issued by the U.S. Federal Aviation Administration (FAA) have come with an important caveat: the aircraft cannot operate beyond visual line of sight (LOS), greatly restricting their use for many applications.

Mike Tully, CEO of Aerial Service Inc. in Cedar Falls, Iowa, knows the frustration. His company has been in the remote sensing business for 50 years, using manned aircraft to provide customers with geographic information for mapping, surveying and other purposes.

After hiring an attorney to file an exemption request with the FAA and waiting 60 days, the company was approved for an ASI Section 333 exemption last May. It was something of a hollow victory, however, for a company that wants to use UAS in place of manned aircraft where it makes sense to do so.

“Overall, my feelings are that the main limitation of this exemption is that it’s restricted to visual line of sight only; we can only fly it where we can see it with the naked eye,” Tully says. “That’s way too restrictive, and I think it’s unnecessary given the technology we have today. It relegates our use of the unmanned vehicle to a far more limited scope of operations and markets.”

David Phillips, Textron Systems Unmanned Systems vice president of small and medium-endurance UAS, points out that his company has more than 110,000 hours of civil and military experience in beyond LOS operations with its Aerosonde unmanned aerial vehicle (UAV).

“I would say 99 percent of that is beyond line-of sight-missions,” he notes. “We’ve got experience in the Arctic and the Antarctic. We’ve flown across the Atlantic. We fly into hurricanes and into typhoons. We’ve flown in the remote Australian outback.”

Much of Textron’s flying is done for the military overseas in such places as Afghanistan, but it also flies beyond LOS civil missions overseas where it has done work for the oil and gas industry. No matter what the circumstances, Phillips says they coordinate their UAS flights with local air traffic control or a governmental authority to operate safely.

“In the U.S., we fly beyond line of sight at FAA-approved test sites in the commercial airspace in coordination with the site and we do beyond line of sight at all of our military test ranges,” Phillips says. “All of those are beyond line-of-sight operations in which we bring the critical enabling technologies and maturity that enable us to convince the authorities in those areas that we can operate safely.”

Unlike most civilian companies, Textron has a U.S. Navy-authorized flight clearance for beyond LOS operations, which means its UAS systems and subsystems must pass a thorough review process for reliability and configuration control.

Phillips ticks off a list of factors that enable Textron to fly its Aerosonde UAS in both the civilian and military worlds. They include the reliability of a purpose-built Lycoming UAS engine and redundant flight and data link systems.

“It’s completely unacceptable in beyond line-of-sight operations that if you lose link, your aircraft just falls out of the sky,” Phillips notes.

If a communications link is lost, there’s a redundant link to kick in. If that’s lost, flight control software takes the UAS back to the last GPS coordinate where it had a data link. The aircraft will always return to a point when it can reestablish a link, Phillips says.

Health unit monitoring through real-time sensors on Textron’s UAS provide information on the aircraft’s systems to the ground control station. If a potential problem can’t be solved in the air, the aircraft returns to base.

“We have separate and distinct data links for communications that are actively redundant, and then a third data link and separate radar that controls our payloads,” Phillips notes. “We don’t bring our payload or streaming video down in the same data link that we’re using to communicate with the aircraft. We want to keep those bandwidths separate.”

The company’s UAS operators are rated pilots who go through 14 weeks of certification training, as well as annual training. In addition, Textron has a certified maintenance program in which preemptive maintenance is performed and UAS are taken out of service and overhauled after a certain amount of time.

Whether flying in civil or military airspace, Phillips says Textron’s UAS pilots communicate directly with air traffic control. Their UAVs have transponders enabling them to be positively identified on radar systems.

The problem isn’t that the technology for UAS beyond LOS operations doesn’t exist. Instead, it’s a matter of the FAA having confidence in its ability to reliably track and safely manage thousands of UAS sharing the world’s most complex airspace with manned aircraft from the ground up .

“To go beyond visual line of sight in any significant manner requires advancement in two areas of technology,” says Douglas Olsen, a UAS research assistant with the University of North Dakota’s School of Aerospace Sciences. “One is airborne detect-and-avoid or sense-and-avoid capabilities for seeing other aircraft. The other one is maintaining control of aircraft at extended distances.”

Special Committee 228 (SC228) of the Radio Technical Commission for Aeronautics (RTCA) has been tasked by the FAA to develop minimum operational performance standards (MOPS) for UAS. The committee is working on standards for detect-and-avoid (DAA) systems to maintain safe separation between aircraft and data link standards for UAS command and control (C2) functions. The final version of the MOPS is expected by July 2016.

Olsen, a member of the SC228 C2 committee, manages a research project jointly funded by avionics manufacturer Rockwell Collins of Cedar Rapids, Iowa, and the North Dakota Department of Commerce. Radio technology being developed by Rockwell Collins for beyond LOS missions is being flown on the Northrop Grumman SandShark UAV.

Olsen says the concept for UAS beyond LOS operations being pursued involves designating a secure, robust aviation-protected radio communications link and establishing a network of towers across the U.S. As a UAS is being flown cross-country by a ground control station, it would be handed off from tower to tower.

“That’s the direction that the regulations are leaning,” Olsen notes.

Looking toward the FAA’s regulatory approach, NASA has funded Rockwell Collins to develop a prototype CNPC (command, non-payload, communication) radio and wave form to demonstrate its capabilities in the L and C band frequencies of the aviation-protected spectrum.

“These are areas of the spectrum that others won’t be able to use,” Olsen explains. “They are secure and won’t be stepped on by other users.”

Working with the Northern Plains UAS Test Site, Olsen says UND and Rockwell Collins are installing the radios and antennas on small, composite-material UAS and flying them from a public airport in challenging communications areas, such as at low altitudes where multi-pass effects can occur. They’re studying the performance of different antenna types and conducting a host of radio frequency experiments.

Tom Vogl, Rockwell Collins project engineer, says that the company has worked with NASA to validate the CNPC radios for beyond LOS operations at a range of more than 100 miles and has flown tests of applications that perform handoffs between towers. Among the technical issues yet to be addressed are how the radio spectrum is allocated and the development of an infrastructure to support it, he notes.

Vogl says the RTCA SC228 is also studying satellite communications for UAS beyond LOS operations, which would provide a more comprehensive communications solution in addition to air and ground systems. 

According to Vogl, longer range goals for Rockwell Collins are to validate concepts, make them available at the FAA’s UAS test sites, develop infrastructure others can use to validate their concepts and make certain that the form factor of the prototype CNPC radio is appropriate for a wide range of users in the UAS community.

The use of UAS to inspect critical linear infrastructure such as oil and gas pipelines and electrical transmission lines is one area in which beyond LOS operations are likely to first occur, says David Yoel, CEO of American Aerospace Technologies Inc. The Pennsylvania-based company has already conducted two research flights this year during which its UAVs flew beyond the pilot’s line of sight while being followed by a chase helicopter.

Overall, Yoel says AAT has flown as far as 20 miles downrange from the UAS launch point and has done about 100 flights beyond the sight line of the pilot in command.

The first flight in March was flown with AAT’s RS-16—built by Arcturus UAV—for 12 miles over a Colonial Pipeline Co. pipeline to establish the aviation operation. The second flight in June covered 40 miles of pipeline, this time using the company’s larger RS-20 UAV, which carried a sensor package that successfully identify threats to the pipeline’s integrity. A third flight is planned for later this year.

The missions were overseen by Mid-Atlantic Aviation Partnership (MAAP) and Virginia Tech University with the support of the Pipeline Research Council International. The test area within the COA covers 185 square miles, has a 3,000-foot flight ceiling and is located about 15 miles west of Richmond, Virginia.

“We can eliminate risk to the pilots and identify machinery threats, the biggest risk to the industry,” Yoel says. “We’ve now done that with the use of UAS beyond visual line of sight.”

He says the goal is to eventually fly UAS missions hundreds of miles long without using chase aircraft and while employing sensors that quickly and automatically identify threats to pipeline integrity. However, before that can happen, Yoel says, “We need to integrate various detect-and-avoid technologies to determine which would be appropriate in a linear infrastructure environment and provide it in a safe way that the FAA can consider adopting.”

“It’s the non-cooperative users of the airspace that we have to be concerned about,” Yoel explains. “They’re not required to file a flight plan or to carry a radio. We have to be able to detect and avoid them without their cooperation. If we can’t do that, there will be no beyond-line-of-sight civil unmanned aviation industry. Period. That is a fundamental bottleneck.”

Phillips says that fitting DAA devices on a UAV the size of the Aerosonde is a challenge, but Textron is making investments to come up with a solutions, possibly using a combination of visual and audible technologies.

“When the FAA opens up the airspace, they’re going to want you to safely detect, sense and avoid something that’s on a collision course with your aircraft and take autonomous measures to change your course,” he says. “They’re going to want you to do that 24/7, day or night in any weather condition.”

Because technology that depends on sight can be hindered by weather, Textron is also considering an audible system that cancels out the UAV’s engine noise and looks for other sounds within the spectrum similar to aircraft engines, Phillips says.

NASA is continuing its research on developing sense-and-avoid technology. During June and July, the agency collaborated with the FAA, General Atomics and Honeywell for flight testing at the agency’s Armstrong Fight Research Center in California. It was the first full testing of an automatic collision avoidance capability on autonomous aircraft.

The tests were the third in a series that built on similar experiments to demonstrate a proof-of-concept DAA system. The tests engaged the core air traffic infrastructure and supporting software components through a live and virtual environment to demonstrate how an autonomous aircraft interacts with air traffic controllers and other air traffic.

“I think the maturity of the technology on the communications side is further along than it is on the detect-and-avoid side,” says Yoel. “The detection and avoidance combined is a difficult task. It’s a fundamental technology needed for the entire industry.”

Obviously, not every business engaged in the UAS industry has the resources and connections of a Textron Systems. But the company’s experience and thousands of hours of UAS operations provide a useful roadmap leading toward safe, effective beyond LOS operations.

“We’ve got certificates of authorization to fly at two of the FAA approved test sites in Warm Springs, Oregon, and at the Mid-Atlantic Aviation Partnership down at Fort Pickett, Virginia,” Phillips says. “We’ll utilize that commercial airspace and those relationships with the test sites to integrate technologies and go try them out in the commercial airspace. I think we’ll be ready when they sort all that out.”

Author: Patrick C. Miller
Staff Writer, UAS Magazine
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